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Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2018	Feb. 25, 2019	Jun. 29, 2018
Document Information [Line Items]
Entity Registrant Name	ACELRX PHARMACEUTICALS INC
Entity Central Index Key	0001427925
Trading Symbol	acrx
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding (in shares)		78,757,930
Entity Public Float			$ 177,225,920
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Shell Company	false

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 87,975	$ 52,902
Short-term investments	17,740	7,567
Accounts receivable, net	49	1,533
Tax receivable	352
Inventories	854	956
Prepaid expenses and other current assets	1,024	455
Total current assets	107,994	63,413
Property and equipment, net	11,483	11,051
Restricted cash	178	178
Long-term tax receivable	351	703
Other assets	527	207
Total Assets	120,533	75,552
Liabilities and Stockholders’ Equity (Deficit)
Accounts payable	2,070	1,424
Accrued liabilities	4,540	3,543
Long-term debt, current portion	8,611	7,727
Deferred revenue, current portion	315	362
Liability related to the sale of future royalties, current portion	392	604
Total current liabilities	15,928	13,660
Deferred rent, net of current portion	416	378
Long-term debt, net of current portion	3,380	11,369
Deferred revenue, net of current portion	3,148	3,463
Liability related to the sale of future royalties, net of current portion	93,287	82,984
Contingent put option liability	121	207
Total liabilities	116,280	112,061
Commitments and Contingencies
Stockholders’ Equity (Deficit):
Common stock, $0.001 par value—100,000,000 shares authorized as of December 31, 2018 and December 31, 2017; 78,757,930 and 50,899,154 shares issued and outstanding as of December 31, 2018 and December 31, 2017	78	51
Additional paid-in capital	349,194	261,310
Accumulated deficit	(345,019)	(297,870)
Total stockholders’ equity (deficit)	4,253	(36,509)
Total Liabilities and Stockholders’ Equity (Deficit)	$ 120,533	$ 75,552

Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	78,757,930	50,899,154
Common stock, outstanding (in shares)	78,757,930	50,899,154

Consolidated Statements of Comprehensive Loss - USD ($)	12 Months Ended
Consolidated Statements of Comprehensive Loss - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Revenue	$ 2,151,000	$ 7,995,000	$ 17,357,000
Operating costs and expenses:
Cost of goods sold	3,976,000	10,659,000	12,315,000
Research and development	13,137,000	19,409,000	21,402,000
General and administrative	20,765,000	16,609,000	15,597,000
Total operating costs and expenses	37,878,000	46,677,000	49,314,000
Loss from operations	(35,727,000)	(38,682,000)	(31,957,000)
Other expense:
Interest expense	(2,217,000)	(3,316,000)	(2,770,000)
Interest income and other income, net	1,138,000	510,000	918,000
Non-cash interest expense on liability related to sale of future royalties	(10,341,000)	(10,721,000)	(9,382,000)
Total other expense	(11,420,000)	(13,527,000)	(11,234,000)
Net loss before income taxes	(47,147,000)	(52,209,000)	(43,191,000)
Provision (benefit) for income taxes	2,000	(701,000)	(34,000)
Net loss	(47,149,000)	(51,508,000)	(43,157,000)
Other comprehensive (loss) income:
Unrealized (losses) gains on available for sale securities		(3,000)	4,000
Comprehensive loss	$ (47,149,000)	$ (51,511,000)	$ (43,153,000)
Net loss per share of common stock, basic and diluted (in dollars per share)	$ (0.81)	$ (1.10)	$ (0.95)
Shares used in computing net loss per share of common stock, basic and diluted –see Note 14 (in shares)	58,408,548	46,883,535	45,313,118
Collaboration Agreement Revenue [Member]
Revenue:
Revenue	$ 1,313,000	$ 7,143,000	$ 6,440,000
Contract and Other [Member]
Revenue:
Revenue	$ 838,000	$ 852,000	$ 10,917,000

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2015	45,273,772
Balance at Dec. 31, 2015	$ 45	$ 236,274	$ (203,205)	$ (1)	$ 33,113
Stock-based compensation		4,479			4,479
Modification of warrants		45			45
Issuance of common stock upon ESPP purchase (in shares)	60,018
Issuance of common stock upon ESPP purchase		179			179
Change in unrealized gains and losses on investments				4	4
Net loss			(43,157)		(43,157)
Balance (in shares) at Dec. 31, 2016	45,333,790
Balance at Dec. 31, 2016	$ 45	240,977	(246,362)	3	(5,337)
Stock-based compensation		4,294			4,294
Issuance of common stock upon ESPP purchase (in shares)	94,893
Issuance of common stock upon ESPP purchase		246			246
Change in unrealized gains and losses on investments				(3)	(3)
Net loss			(51,508)		(51,508)
Net proceeds from issuance of common stock in connection with equity financings (in shares)	5,401,099
Net proceeds from issuance of common stock in connection with equity financings	$ 6	15,688			15,694
Issuance of common stock upon exercise of stock options (in shares)	69,372
Issuance of common stock upon exercise of stock options		105			105
Net proceeds from issuance of common stock in connection with equity financings (in shares)	5,401,099
Balance (in shares) at Dec. 31, 2017	50,899,154
Balance at Dec. 31, 2017	$ 51	261,310	(297,870)		(36,509)
Stock-based compensation		5,168			5,168
Issuance of common stock upon ESPP purchase (in shares)	182,360
Issuance of common stock upon ESPP purchase		275			275
Change in unrealized gains and losses on investments
Net loss			(47,149)		(47,149)
Net proceeds from issuance of common stock in connection with equity financings (in shares)	27,364,301
Net proceeds from issuance of common stock in connection with equity financings	$ 27	81,498			$ 81,525
Issuance of common stock upon exercise of stock options (in shares)	135,385				135,385
Issuance of common stock upon exercise of stock options		401			$ 401
Net proceeds from issuance of common stock in connection with equity financings (in shares)	27,364,301
Issuance of common stock upon exercise of warrants (in shares)	176,730
Issuance of common stock upon exercise of warrants		542			542
Balance (in shares) at Dec. 31, 2018	78,757,930
Balance at Dec. 31, 2018	$ 78	$ 349,194	$ (345,019)		$ 4,253

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (47,149)	$ (51,508)	$ (43,157)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to royalty monetization	(289)	(151)	(7)
Non-cash interest expense on liability related to royalty monetization	10,341	10,721	9,382
Depreciation and amortization	575	1,744	2,052
Non-cash interest expense related to debt financing	613	1,265	877
Stock-based compensation	5,168	4,294	4,479
Revaluation of put option and PIPE warrant liabilities	(86)	(205)	(767)
Loss on disposal and impairment of property and equipment		12
Inventory impairment charge		369
Other	(115)	(5)	17
Changes in operating assets and liabilities:
Accounts receivable	1,484	4,300	(2,547)
Inventories	102	920	(1,688)
Prepaid expenses and other assets	(850)	175	975
Tax receivable		(703)
Accounts payable	458	309	(437)
Accrued liabilities	922	(1,301)	639
Deferred revenue	(362)	(361)	989
Deferred rent	113	360	(202)
Net cash used in operating activities	(29,075)	(29,765)	(29,395)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(819)	(2,405)	(3,720)
Purchase of investments	(30,558)	(7,565)	(996)
Proceeds from maturities of investments	20,500		6,525
Net cash (used in) provided by investing activities	(10,877)	(9,970)	1,809
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of long-term debt	(7,718)	(3,514)
Payment of debt modification transaction costs		(204)	(205)
Net proceeds from issuance of common stock in connection with equity financings	81,525	15,694
Net proceeds from issuance of common stock through equity plans	1,218	351	179
Net cash provided by (used in) financing activities	75,025	12,327	(26)
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	35,073	(27,408)	(27,612)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—Beginning of period	53,080	80,488	108,100
CASH, CASH EQUIVALENTS AND RESTRICTED CASH —End of period	88,153	53,080	80,488
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest	1,667	2,043	1,893
Income taxes paid (refunded)	2	2	(55)
NONCASH INVESTING AND FINANCING ACTIVITIES:
Modification of warrants for common stock			45
Purchases of property and equipment in Accounts payable	$ 410	$ 222	$ 532

Reconciliation of Cash, Cash Equivalents, and Restricted Cash

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Cash and Cash Equivalents Disclosure [Text Block]

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statement of cash flows (in thousands):

	Year Ended December 31,
	2018		2017		2016
CASH AND CASH EQUIVALENTS		87,975		52,902		80,310
RESTRICTED CASH		178		178		178
CASH, CASH EQUIVALENTS AND RESTRICTED CASH SHOWN IN STATEMENT OF CASH FLOWS	$	88,153	$	53,080	$	80,488

Amounts included in restricted cash represent letters of credit required to be maintained under the Company’s facility lease and corporate credit card agreements as security for performance under these agreements. The letters of credit are secured by certificates of deposit in amounts equal to the letters of credit.

See notes to consolidated financial statements.

Note 1 - Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Basis of Presentation and Significant Accounting Policies [Text Block]

Organization and Summary of Significant Accounting Policies

The Company

AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on

July 13, 2005

as SuRx, Inc., and in

January 2006,

the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company’s operations are based in Redwood City, California.

AcelRx is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for use in medically supervised settings. DSUVIA (known as DZUVEO in Europe) and Zalviso, are

both focused on the treatment of acute pain, and each utilize sufentanil, delivered via a non-invasive route of sublingual administration, exclusively for use in medically supervised settings. On

November 2, 2018,

the U.S. Food and Drug Administration, or FDA, approved DSUVIA for use in adults in a certified medically supervised healthcare setting, such as hospitals, surgical centers, and emergency departments, for the management of acute pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate. In

June 2018,

the European Commission, or EC, granted marketing approval of DZUVEO for the treatment of patients with moderate-to-severe acute pain in medically monitored settings. AcelRx is developing a distribution capability and commercial organization to market and sell DSUVIA in the United States. The commercial launch of DSUVIA in the United States occurred in the

first

quarter of

2019.

In geographies where AcelRx decides

not

to commercialize products by itself, including for DZUVEO in Europe, the Company

may

seek to out-license commercialization rights. The Company currently intends to commercialize and promote DSUVIA/DZUVEO outside the United States with

one

or more strategic partners, although it has

not

yet entered into any such arrangement. The Company is currently evaluating the timing of the resubmission of the NDA for Zalviso. AcelRx intends to seek regulatory approval for Zalviso in the United States and, if successful, potentially promote Zalviso either by itself or with strategic partners. Zalviso is approved in Europe and is currently being commercialized by Grünenthal GmbH, or Grünenthal.

DSUVIA

DSUVIA, known as DZUVEO in Europe, approved by the FDA in

November 2018,

is indicated for use in adults in a certified medically supervised healthcare setting, such as hospitals, surgical centers, and emergency departments, for the management of acute pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate. DSUVIA was designed to provide rapid analgesia via a non-invasive route and to eliminate dosing errors associated with IV administration. DSUVIA is a single-strength solid dosage form administered sublingually via a single-dose applicator, or SDA, by healthcare professionals. Sufentanil is an opioid analgesic currently marketed for intravenous, or IV, and epidural anesthesia and analgesia. The sufentanil pharmacokinetic profile when delivered sublingually avoids the high peak plasma levels and short duration of action observed with IV administration. The EC approved DZUVEO for marketing in Europe in

June 2018.

DSUVIA was approved with a Risk Evaluation and Mitigation Strategy, or REMS, which restricts distribution to certified medically supervised healthcare settings in order to prevent respiratory depression resulting from accidental exposure. DSUVIA will only be distributed to facilities certified in the DSUVIA REMS program following attestation by an authorized representative to comply with appropriate dispensing and use restrictions of DSUVIA. To become certified, a healthcare setting will need to train their healthcare professionals on the proper use of DSUVIA and have the ability to manage respiratory depression. DSUVIA will

not

be available in retail pharmacies or for outpatient use. As part of the REMS program, the Company will monitor distribution and audit wholesalers’ data, evaluate proper usage within the healthcare settings and monitor for any diversion and abuse. Additionally, AcelRx will de-certify healthcare settings that are non-compliant with the REMS program.

Zalviso

Zalviso delivers

mcg sufentanil sublingually through a non-invasive delivery route via a pre-programmed, patient-controlled analgesia, or PCA, system. Zalviso is approved in Europe and is in late-stage development in the U.S. The Company had initially submitted to the FDA an NDA seeking approval for Zalviso in

September 2013

but received a CRL on

July 25, 2014.

Subsequently, the FDA requested an additional clinical study,

IAP312,

designed to evaluate the effectiveness of changes made to the functionality and usability of the Zalviso device and to take into account comments from the FDA on the study protocol. In the

IAP312

study, for which top-line results were announced in

August 2017,

Zalviso met safety, satisfaction and device usability expectations. These results will supplement the

three

Phase

trials already completed in the Zalviso NDA resubmission. The Company is currently evaluating the timing of the NDA resubmission for Zalviso.

December 16, 2013,

AcelRx and Grünenthal entered into a Collaboration and License Agreement, or the License Agreement, which was amended effective

July 17, 2015

and

September 20, 2016,

or the Amended License Agreement, which grants Grünenthal rights to commercialize Zalviso PCA system, or the Product, in the countries of the EU, Switzerland, Liechtenstein, Iceland, Norway and Australia (collectively, the Territory) for human use in pain treatment within, or dispensed by, hospitals, hospices, nursing homes and other medically supervised settings, or the Field. In

September 2015,

the EC approved the MAA, previously submitted to the EMA, for Zalviso for the management of acute moderate-to-severe post-operative pain in adult patients. On

December 16, 2013,

AcelRx and Grünenthal, entered into a related Manufacture and Supply Agreement, or the MSA, and together with the License Agreement, the Agreements. Under the MSA, the Company will exclusively manufacture and supply the Product to Grünenthal for the Field in the Territory. On

July 22, 2015,

the Company and Grünenthal amended the MSA, or the Amended MSA, effective as of

July 17, 2015.

The Amended MSA and the Amended License Agreement are referred to as the Amended Agreements.

The Company has incurred recurring operating losses and negative cash flows from operating activities since inception. Although Zalviso has been approved for sale in Europe, on

September 18, 2015,

the Company sold the majority of the royalty rights and certain commercial sales milestones it is entitled to receive under the Amended License Agreement with Grünenthal to PDL BioPharma, Inc., or PDL, in a transaction referred to as the Royalty Monetization. The FDA approved DSUVIA in

November 2018

and the Company began its commercial launch of DSUVIA in the

first

quarter of

2019.

As a result, the Company expects to continue to incur operating losses and negative cash flows until such time as DSUVIA has gained market acceptance and generated significant revenues.

Except as the context otherwise requires, when we refer to "we," "our," "us," the "Company" or "AcelRx" in this document, we mean AcelRx Pharmaceuticals, Inc., and its consolidated subsidiary. “DSUVIA” and “DZUVEO” are trademarks, and “ACELRX” and “Zalviso” are registered trademarks, all owned by AcelRx Pharmaceuticals, Inc. This report also contains trademarks and trade names that are the property of their respective owners.

Basis of Presentation

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. Actual results could differ from those estimates.

Reclassifications

Certain prior year amounts in the Consolidated Financial Statements have been reclassified to conform to the current year's presentation. In particular, the amount reported in the Consolidated Statements of Cash Flows as “Noncash Investing and Financing Activities – Purchases of property and equipment in Accrued liabilities” has been reclassified to “Noncash Investing and Financing Activities – Purchases of property and equipment in Accounts payable” for the year ended

December 31, 2017,

and the amount reported in the Consolidated Statements of Cash Flows as “Amortization of premium/discount on investments, net” has been reclassified to “Other” for the year ended

December 31, 2016.

Principles of Consolidation

The Consolidated Financial Statements include the accounts of the Company and its wholly owned subsidiary, ARPI LLC, which was formed in

September 2015

for the sole purpose of facilitating the Royalty Monetization with PDL of the expected royalty stream and milestone payments due from the sales of Zalviso in the European Union by its commercial partner, Grünenthal, pursuant to the Amended License Agreement. All intercompany accounts and transactions have been eliminated in consolidation. Refer to Note

“Liability Related to Sale of Future Royalties” for additional information.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. Management evaluates its estimates on an ongoing basis including critical accounting policies. Estimates are based on historical experience and on various other market-specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are

not

readily apparent from other sources. Actual results could differ from those estimates.

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investments with an original maturity (at date of purchase) of

three

months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks.

All marketable securities are classified as available-for-sale and consist of U.S. government sponsored enterprise debt securities and commercial paper. These securities are carried at estimated fair value, which is based on quoted market prices or observable market inputs of almost identical assets, with unrealized gains and losses included in accumulated other comprehensive income (loss). The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income or expense. The cost of securities sold is based on specific identification. The Company’s investments are subject to a periodic impairment review for other-than-temporary declines in fair value. The Company’s review includes the consideration of the cause of the impairment including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. When the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other-than-temporary, it reduces the carrying value of the security it holds and records a loss in the amount of such decline.

Fair Value of Financial Instruments

The Company measures and reports its cash equivalents, investments and financial liabilities at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a

three

-level valuation hierarchy for disclosure of fair value measurements as follows:

Level I—Unadjusted quoted prices in active markets for identical assets or liabilities;

Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are

not

active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level III—Unobservable inputs that are supported by little or

market activity for the related assets or liabilities.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Segment Information

The Company operates in a single segment, the development and commercialization of product candidates for the treatment of pain. The Company’s contract revenue relates to sales in the United States. The Company’s collaboration revenue relates to the Amended License Agreement with Grünenthal to commercialize Zalviso in the countries of the European Union, Switzerland, Liechtenstein, Iceland, Norway and Australia.

Concentration of Risk

The Company invests cash that is currently

not

being used for operational purposes in accordance with its investment policy in debt securities of U.S. government sponsored agencies and overnight deposits. The Company is exposed to credit risk in the event of default by the institutions holding the cash equivalents and available-for-sale securities to the extent recorded on the Consolidated Balance Sheets.

The Company relies on a single

third

-party supplier for the supply of sufentanil, the active pharmaceutical ingredient in DSUVIA and Zalviso, and various sole-source

third

-party contract manufacturer organizations to manufacture the DSUVIA SDA and Zalviso drug cartridge and device components, including the controller, the dispenser kit and the accessories.

To date, the Company has had only

two

customers. These

two

customers account for

100%

of the revenues for the years ended

December 31, 2018,

2017

and

2016.

One of these customers accounted for

100%

and

79%

of the accounts receivable balance as of

December 31, 2018,

and

2017,

respectively, while the other customer accounted for

71%

of the accounts receivable balance as of

December 31, 2016.

The Company has

not

experienced any losses with respect to the collection of its accounts receivable and believes that the entire accounts receivable balance as of

December 31, 2018

is collectible.

Accounts Receivable, Net

The Company has receivables from its collaboration partner and the U.S. Department of Defense, or DoD. To date, the Company has

not

had a bad debt allowance because of the limited number of financially sound customers who have historically paid their balances timely. The need for a bad debt allowance is evaluated each reporting period based on the Company’s assessment of the credit worthiness of its customers or any other potential circumstances that could result in bad debt.

Inventories

Inventories are valued at the lower of cost and net realizable value. Cost is determined using the

first

-in,

first

-out method for all inventories. Inventory includes the cost of the active pharmaceutical ingredients, or API, raw materials and

third

-party contract manufacturing and packaging services. Indirect overhead costs associated with production and distribution are allocated to the appropriate cost pool and then absorbed into inventory based on the units produced or distributed, assuming normal capacity, in the applicable period. Indirect overhead costs in excess of normal capacity are recorded as period costs in the period incurred.

The Company's policy is to write down inventory that has become obsolete, inventory that has a cost basis in excess of its expected net realizable value and inventory in excess of expected requirements. The Company periodically evaluates the carrying value of inventory on hand for potential excess amount over demand using the same lower of cost or market approach as that used to value the inventory. Because the predetermined, contractual transfer prices the Company is receiving from Grünenthal are less than the direct costs of manufacturing, all Zalviso inventories are carried at net realizable value.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, generally

three

five

years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term. Expenditures for repairs and maintenance, which do

not

extend the useful life of the property and equipment, are expensed as incurred. Upon retirement, the asset cost and related accumulated depreciation are relieved from the accompanying Consolidated Balance Sheets. Gains and losses associated with dispositions are reflected as a component of Other expense in the accompanying Consolidated Statements of Comprehensive Loss.

Impairment of Long-Lived Assets

The Company periodically assesses the impairment of long-lived assets and, if indicators of asset impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through an analysis of the undiscounted future expected operating cash flows. If impairment is indicated, the Company records the amount of such impairment for the excess of the carrying value of the asset over its estimated fair value. For example, if the Company is

not

successful in its commercialization of DSUVIA, and if approved, Zalviso, purchased equipment and manufacturing-related facility improvements the Company has made at its contract manufacturers could become impaired. The Company

may

determine that it is

longer probable that the Company will realize the future economic benefit associated with the costs of these assets through future manufacturing activities, and if so, the Company would record an impairment charge associated with these assets. As of

September 30, 2015,

the Company remeasured on a non-recurring basis a portion of its leasehold improvements in its corporate offices using Level III valuation techniques. The write down to fair value of these long-lived assets resulted in an impairment charge of

$0.5

million in the year ended

December 31, 2015,

which was recorded in interest income and other income, net in the Consolidated Statements of Comprehensive Loss. As of

December

31,

2018,

the Company has

not

written down any additional long-lived assets as a result of impairment.

Restricted Cash

Under the Company’s facility lease and corporate credit card agreements, the Company is required to maintain letters of credit as security for performance under these agreements. The letters of credit are secured by certificates of deposit in amounts equal to the letters of credit, which are classified as restricted cash on the Consolidated Balance Sheets.

Debt Issuance Costs

Debt issuance costs, which are included in long-term debt, net of current portion, are amortized as interest expense over the contractual terms of the related credit facilities.

Contingent put option

The contingent put option associated with the Company’s loan and security agreement with Hercules Technology II, L.P. and Hercules Technology Growth Capital, Inc., collectively referred to as the Lenders, is recorded as a liability. Changes in the fair value of the contingent put option are recognized as interest income and other income, net in the Consolidated Statements of Comprehensive Loss. For additional information regarding the contingent put option, see Note

“Long-Term Debt”.

Warrants

Warrants issued in connection with the Company’s Private Placement, completed in

June 2012,

are recorded as liabilities as they have the potential for cash settlement upon the occurrence of certain transactions (as defined in the warrant; see Note

“Warrants”). Changes in the fair value of the warrants are recognized as interest income and other income, net in the Consolidated Statements of Comprehensive Loss. As of

December 31, 2018,

all outstanding warrants of the Company had either been exercised or had expired.

Revenue Recognition

Beginning

January

2018,

the Company has followed the provisions of ASC Topic

606,

Revenue from Contracts with Customers

. The guidance provides a unified model to determine how revenue is recognized.

The Company generates revenue from collaboration agreements. These agreements typically include payments for upfront signing or license fees, cost reimbursements for development and manufacturing services, milestone payments, product sales, and royalties on licensee’s future product sales.

The Company has entered into award contracts with U.S. Department of Defense, or the DoD, to support the development of DSUVIA. These contracts provide for the reimbursement of qualified expenses for research and development activities. Revenue under these arrangements is recognized when the related qualified research expenses are incurred. The Company is entitled to reimbursement of overhead costs associated with the study costs under the DoD arrangements. The Company estimates this overhead rate by utilizing forecasted expenditures. Final reimbursable overhead expenses are dependent on direct labor and direct reimbursable expenses throughout the life of each contract, which

may

increase or decrease based on actual expenses incurred.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation.

Performance Obligations

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic

606.

The Company’s performance obligations include commercialization license rights, development services, services associated with the regulatory approval process, joint steering committee services, demo devices, manufacturing services, material rights for discounts on manufacturing services, and product supply.

The Company has optional additional items in contracts, which are considered marketing offers and are accounted for as separate contracts when the customer elects such options. Arrangements that include a promise for future commercial product supply and optional research and development services at the customer’s or the Company’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, such material rights are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded in revenue when the customer obtains control of the goods or services.

Transaction Price

The Company has both fixed and variable consideration. Non-refundable upfront fees and product supply selling prices are considered fixed, while milestone payments are identified as variable consideration when determining the transaction price. Funding of research and development activities is considered variable until such costs are reimbursed at which point they are considered fixed. The Company allocates the total transaction price to each performance obligation based on the relative estimated standalone selling prices of the promised goods or services for each performance obligation.

At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would

not

occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price. Milestone payments that are

not

within the control of the Company, such as approvals from regulators, are

not

considered probable of being achieved until those approvals are received.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).

Allocation of Consideration

As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. Estimated selling prices for license rights and material rights for discounts on manufacturing services are calculated using an income approach model and can include the following key assumptions: the development timeline, sales forecasts, costs of product sales, commercialization expenses, discount rate, the time which the manufacturing services are expected to be performed, and probabilities of technical and regulatory success. For all other performance obligations, the Company uses a cost-plus margin approach.

Timing of Recognition

Significant management judgment is required to determine the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under the arrangement. The Company estimates the performance period or measure of progress at the inception of the arrangement and re-evaluates it each reporting period. This re-evaluation

may

shorten or lengthen the period over which revenue is recognized. Changes to these estimates are recorded on a cumulative catch up basis. If the Company cannot reasonably estimate when its performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. Revenue is recognized for products at a point in time when control of the product is transferred to the customer in an amount that reflects the consideration the Company expects to be entitled to in exchange for those product sales, which is typically once the product physically arrives at the customer, and for licenses of functional intellectual property at the point in time the customer can use and benefit from the license. For performance obligations that are services, revenue is recognized over time proportionate to the costs that the Company has incurred to perform the services using the cost-to-cost input method.

Cost of Goods Sold

Under the Amended Agreements with Grünenthal, the Company sells Zalviso to Grünenthal at predetermined, contractual transfer prices that are less than the direct costs of manufacturing and recognizes indirect costs as period costs where they are in excess of normal capacity and

not

realizable on a lower of cost or market basis. Cost of goods sold for Zalviso shipped to Grünenthal includes the inventory costs of API,

third

-party contract manufacturing costs, packaging and distribution costs, shipping, handling and storage costs, depreciation and costs of the employees involved with production.

Research and Development Expenses

Research and development costs are charged to expense when incurred. Research and development expenses include salaries, employee benefits, including stock-based compensation, consultant fees, laboratory supplies, costs associated with clinical trials and manufacturing, including contract research organization fees, other professional services and allocations of corporate costs. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies and other events.

Stock-Based Compensation

Compensation expense for all share-based payment awards made to employees and directors, including employee stock options and restricted stock units related to the

2011

Equity Incentive Plan, or

2011

EIP, and employee share purchases related to the

2011

Employee Stock Purchase Plan, or ESPP, is based on estimated fair values at grant date. The Company determines the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognizes the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards.

The Black-Scholes option pricing model requires inputs such as expected term, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. Estimates of expected life during the year ended

December 31, 2016,

was primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did

not

believe its historical option exercise experience, which was limited, provided a reasonable basis upon which to estimate expected term. During this period, volatility was derived from historical volatilities of several public companies within AcelRx’s industry that were deemed to be comparable to AcelRx’s business because AcelRx had insufficient history on the volatility of its common stock relative to the expected life assumptions used by the Company. During the year ended

December 31, 2017,

the Company determined that its historical data provided a reasonable basis for estimating future behavior in regard to expected term and volatility, and as a result, began using its historical option exercise experience and the volatility of its common stock as the basis for these assumptions. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. Further, during the year ended

December 31, 2016,

the Company estimated forfeitures at the time of grant and revised those estimates in subsequent periods if actual forfeitures differed from those estimates. Effective

January 1, 2017,

the Company adopted ASU

2016

and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

Non-Cash Interest Expense on Liability Related to Sale of Future Royalties

September 2015,

the Company sold certain royalty and milestone payment rights from the sales of Zalviso in the European Union by its commercial partner, Grünenthal, pursuant to the Collaboration and License Agreement, dated as of

December 16, 2013,

as amended, to PDL for an upfront cash purchase price of

$65.0

million, referred to as the Royalty Monetization. The Company continues to have significant continuing involvement in the Royalty Monetization primarily due to an obligation to act as the intermediary for the supply of Zalviso to Grünenthal. Under the relevant accounting guidance, because of the Company’s significant continuing involvement, the Royalty Monetization has been accounted for as a liability that will be amortized using the effective interest method over the life of the arrangement. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future royalty and milestone payments to be received by ARPI LLC and payments paid to PDL, up to a capped amount of

$195.0

million, over the life of the arrangement. The aggregate future estimated royalty and milestone payments (subject to the capped amount), less the

$61.2

million of net proceeds the Company received will be recorded as interest expense over the life of the liability. Consequently, the Company imputes interest on the unamortized portion of the liability and records interest expense related to the Royalty Monetization accordingly.

There are a number of factors that could materially affect the amount and timing of royalty payments from Zalviso in Europe, most of which are

not

within the Company’s control. Such factors include, but are

not

limited to, the success of Grünenthal’s sales and promotion of Zalviso, changing standards of care, the introduction of competing products, manufacturing or other delays, intellectual property matters, adverse events that result in governmental health authority imposed restrictions on the use of Zalviso, significant changes in foreign exchange rates as the royalties remitted to ARPI are made in U.S. dollars (USD) while significant portions of the underlying European sales of Zalviso, as well as the royalty payments remitted by Grünenthal to ARPI on such sales, are made in currencies other than USD, and other events or circumstances that could result in reduced royalty payments from European sales of Zalviso, all of which would result in a reduction of non-cash royalty revenues and the non-cash interest expense over the life of the Royalty Monetization. Conversely, if sales of Zalviso in Europe are more than expected, the non-cash royalty revenues and the non-cash interest expense recorded by the Company would be greater over the term of the Royalty Monetization. The Company periodically assesses the expected royalty and milestone payments using a combination of historical results, internal projections and forecasts from external sources. To the extent such payments are greater or less than the Company’s initial estimates or the timing of such payments is materially different than its original estimates, the Company will prospectively adjust the amortization of the liability and the interest rate.

The Company will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the Royalty Monetization.

Comprehensive Loss

Comprehensive loss is comprised of net loss and other comprehensive income (loss) and is disclosed in the Consolidated Statements of Comprehensive Loss. For the Company, other comprehensive income (loss) consists of changes in unrealized gains and losses on the Company’s investments.

Income Taxes

Deferred tax assets and liabilities are measured based on differences between the financial reporting and tax basis of assets and liabilities using enacted rates and laws that are expected to be in effect when the differences are expected to reverse. The Company records a valuation allowance for the full amount of deferred assets, which would otherwise be recorded for tax benefits relating to operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than

not.

Net Loss per Share of Common Stock

The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, convertible preferred stock, options to purchase common stock, restricted stock subject to repurchase, warrants to purchase convertible preferred stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, such common stock equivalents are excluded from the calculation of diluted net loss per share of common stock if their effect is antidilutive. For additional information regarding the net loss per share, see Note

“Net Loss per Share of Common Stock”.

Recently

Adopted Accounting Pronouncement

May 2014,

the FASB issued ASU

No.

2014

09,

Revenue from Contracts with Customers (Topic

606

)

, to provide guidance on revenue recognition. In

August 2015

and

March,

April,

May

and

December 2016,

the FASB issued additional amendments to the new revenue guidance relating to reporting revenue on a gross versus net basis, identifying performance obligations, licensing arrangements, collectability, noncash consideration, presentation of sales tax, transition, and clarifying examples. Collectively these are referred to as ASC Topic

606,

which replaces all legacy GAAP guidance on revenue recognition and eliminates all industry-specific guidance. The new revenue recognition guidance provides a unified model to determine how revenue is recognized. The core principal of the guidance is that an entity should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In applying ASC Topic

606,

companies need to use more judgment and make more estimates than under legacy guidance. This includes identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each distinct performance obligation. ASC Topic

606

is effective for interim and annual reporting periods beginning after

December 15, 2017,

with early adoption permitted

one

year earlier.

The Company adopted the new standard effective

January 1, 2018

under the modified retrospective transition method, applying the new guidance in the

first

quarter of

2018

to those contracts which were

not

completed as of

January 1, 2018.

For contracts which were modified before the adoption date, the Company has elected to treat the contracts and their modifications as combined contracts. Upon adoption, there was

change to the units of accounting previously identified under legacy GAAP, which are now considered performance obligations under the new guidance, and there was

change to the revenue recognition pattern for each performance obligation. Therefore, the adoption of the new standard resulted in

cumulative effect to the opening accumulated deficit balance.

May 2017,

the FASB issued ASU

2017

09,

Compensation - Stock Compensation (Topic

718

Scope of Modification Accounting

, to clarify which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under ASC

718.

Under the new guidance, an entity will

not

apply modification accounting to a share-based payment award if all of the following remain unchanged immediately before and after the change of terms and conditions:

●

The award’s fair value (or calculated value or intrinsic value, if those measurement methods are used),

●

The award’s vesting conditions, and

●

The award’s classification as an equity or liability instrument.

ASU

2017

is effective for annual periods, and interim periods within those annual periods, beginning after

December 15, 2017

for all entities. Early adoption is permitted, including adoption in any interim period for which financial statements have

not

yet been issued or made available for issuance. The ASU will be applied prospectively to awards modified on or after the adoption date. The adoption of ASU

2017

effective

January 1, 2018

did

not

have a material effect on the Company’s results of operations, financial condition or cash flows.

November 2016,

the FASB issued ASU

No.

2016

18,

Statement of Cash Flows (Topic

230

): Restricted Cash

. ASU

No.

2016

is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the consolidated statement of cash flows. The ASU requires that the consolidated statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the consolidated statement of cash flows and the cash and equivalents balance presented on the consolidated balance sheet. The Company adopted ASU

No.

2016

18,

and the guidance has been retrospectively applied to all periods presented. The adoption of the guidance did

not

have an impact on the Company’s consolidated balance sheets or statements of comprehensive loss.

August 2016,

the FASB issued ASU

No.

2016

15,

Statement of Cash Flows (Topic

230

): Classification of Certain Cash Receipts and Cash Payments,

addressing

eight

specific cash flow issues in an effort to reduce diversity in practice. The amended guidance is effective for fiscal years beginning after

December 15, 2017,

and for interim periods within those years. The adoption of ASU

2016

effective

January 1, 2018

did

not

have a material impact on the Company’s consolidated statements of cash flows.

Recently Issued

Accounting Pronouncements

February 2016,

the FASB issued ASU

No.

2016

02,

Leases (Topic

842

)

, which establishes a new lease accounting model for lessees. In

January,

July

and

December 2018,

the FASB issued additional amendments to the new lease guidance relating to, transition, and clarification. The

July 2018

amendment, ASU

No.

2018

11,

Leases (Topic

842

): Targeted Improvements

, provides an optional transition method that allows entities to elect to apply the standard prospectively at its effective date, versus recasting the prior periods presented. Pursuant to ASU

No.

2018

11,

the Company will elect to use the effective date approach at transition. Unlike current GAAP, which requires only capital leases to be recognized on the balance sheet, the new guidance will require both types of leases (i.e. operating and capital leases) to be recognized on the balance sheet. The FASB lessee accounting model will continue to account for both types of leases. Capital leases will be accounted for in substantially the same manner as capital leases are accounted for under existing GAAP. Operating leases will be accounted for in a manner similar to operating leases under existing GAAP, except that lessees will recognize a lease liability and a lease asset for all of those leases. The amended guidance is effective for fiscal years, and interim periods within those years, beginning after

December 15, 2018,

with early adoption permitted. The Company plans to adopt this standard on the effective date of

January 1, 2019.

The Company is substantially complete with its evaluation of the new standard as it relates to its operating lease disclosed in Note

“Commitments and Contingencies”. The remaining steps in the implementation process include finalizing lease liability and right of use asset schedules and the review and evaluation of disclosures and presentation in the Company’s financial statements. In addition, an evaluation of whether there are existing contracts that

may

contain embedded leases has been performed and the Company is evaluating the impact of its findings. However, it does

not

expect that the identification of any embedded leases will result in a material impact to the consolidated financial statements and disclosures upon the adoption of this standard. The adoption of the new standard will

not

have a material impact on the Company’s consolidated statements of comprehensive loss; however, it will materially impact the carrying value of the assets and liabilities in the consolidated balance sheets as a result of the requirement to record right-of-use assets and corresponding lease obligations for current operating leases. The Company will continue to monitor additional modifications, clarifications or interpretations undertaken by the FASB that

may

impact its current conclusions and will expand its analysis to include any new lease arrangements initiated prior to adoption.

Note 2 - Investments and Fair Value Measurement

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Investments and Fair Value Measurement Disclosure [Text Block]

Investments and Fair Value Measurement

Investments

The Company classifies its marketable securities as available-for-sale and records its investments at fair value. Available-for-sale securities are carried at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive income. Marketable securities which have maturities beyond

one

year as of the end of the reporting period are classified as
non-current.

The table below summarizes the Company’s cash, cash equivalents and investments (in thousands):

	As of December 31 , 201 8
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	2,037	$	—	$	—	$	2,037
Money market funds		1,436		—		—		1,436
U.S. government agency securities		10,181		—		—		10,181
Commercial paper		74,321		—		—		74,321
Total cash and cash equivalents		87,975		—		—		87,975

Short-term investments:
U.S. government agency securities	$	1,497	$	—	$	—	$	1,497
Commercial paper		16,243		—		—		16,243
Total marketable securities and commercial paper		17,740		—		—		17,740

Total cash, cash equivalents and investments	$	105,715	$	—	$	—	$	105,715

	As of December 31 , 201 7
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	29,765	$	—	$	—	$	29,765
U.S. government agency securities		23,137		—		—		23,137
Total cash and cash equivalents		52,902		—		—		52,902

Short-term investments:
U.S. government agency securities	$	7,567	$	—	$	—	$	7,567
Total marketable securities		7,567		—		—		7,567

Total cash, cash equivalents and investments	$	60,469	$	—	$	—	$	60,469

None

of the available-for-sale securities held by the Company had material unrealized losses and there were

realized losses for the years ended

December

31,

2018

and

2017.

There were

other-than-temporary impairments for these securities as of

December

31,

2018

2017.

gross realized gains or losses were recognized on the available-for-sale securities and, accordingly, there were

amounts reclassified out of accumulated other comprehensive income to earnings during the years ended

December 31, 2018

and

2017.

As of

December

31,

2018

and

2017,

the contractual maturity of all investments held was less than

one

year.

Fair Value Measurement

The Company’s financial instruments consist of Level I and II assets and Level III liabilities. Money market funds are highly liquid investments and are actively traded. The pricing information on these investment instruments are readily available and can be independently validated as of the measurement date. This approach results in the classification of these securities as Level

of the fair value hierarchy. For Level II instruments, the Company estimates fair value by utilizing

third

party pricing services in developing fair value measurements where fair value is based on valuation methodologies such as models using observable market inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers and other reference data. Such Level II instruments typically include U.S. treasury, U.S. government agency securities and commercial paper. As of

December

31,

2018

and

December

31,

2017,

the Company held, in addition to Level II assets, a contingent put option liability associated with the Amended and Restated Loan and Security Agreement, or the Amended Loan Agreement with Hercules Capital Funding Trust

2014

and Hercules Technology II, L.P., together, Hercules. See Note

“Long-Term Debt” for further description. The Company’s estimate of fair value of the contingent put option liability was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the

two

estimated fair values is the estimated fair value of the default provisions, or the contingent put option. Changes to the estimated fair value of these liabilities are recorded in Interest income and other income, net in the Consolidated Statements of Comprehensive Loss. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default and discounting such cash flows back to the reporting date using a risk-free rate.

The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy (in thousands):

	As of December 31 , 201 8
	Fair Value		Level I		Level II		Level III
Assets
Money market funds	$	1,436	$	1,436	$	—	$	—
U.S. government agency securities		11,678		—		11,678		—
Commercial paper		90,564		—		90,564		—
Total assets measured at fair value	$	103,678	$	1,436	$	102,242	$	—

Liabilities
Contingent put option liability	$	121	$	—	$	—	$	121
Total liabilities measured at fair value	$	121	$	—	$	—	$	121

	As of December 31 , 201 7
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency securities	$	30,704	$	—	$	30,704	$	—
Total assets measured at fair value	$	30,704	$	—	$	30,704	$	—

Liabilities
Contingent put option liability	$	207	$	—	$	—	$	207
Total liabilities measured at fair value	$	207	$	—	$	—	$	207

The following table sets forth a summary of the changes in the fair value of the Company’s Level III financial liabilities for the years ended

December

31,

2018

and

2017

(in thousands):

	Year Ended December 31, 201 8
Fair value—beginning of period	$	207
Change in fair value of contingent put option associated with Amended Loan Agreement		(86	)
Fair value—end of period	$	121

	Year Ended December 31, 201 7
Fair value—beginning of period	$	412
Expiration of fair value of PIPE warrants		(288	)
Change in fair value of contingent put option associated with Amended Loan Agreement		83
Fair value—end of period	$	207

Note 3 - Inventories

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Inventory Disclosure [Text Block]

Inventories

Inventories consist of finished goods, raw materials and work in process and are stated at the lower of cost or market and consist of the following (in thousands):

	As of December 31,
	201 8		201 7
Raw materials	$	694	$	702
Work-in-process		160		254
Inventories	$	854	$	956

The Company periodically evaluates the carrying value of inventory on hand for potential excess amount over demand using the same lower of cost or market approach as that used to value the inventory. During the year ended

December 31, 2017,

the Company recorded an inventory impairment charge of

$0.4

million, primarily for Zalviso raw materials inventory on hand, plus related purchase commitments.

Note 4 - Property and Equipment

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Property, Plant and Equipment Disclosure [Text Block]

Property and Equipment

Property and equipment consist of the following (in thousands):

	As of December 31,
	201 8			201 7
Laboratory equipment	$	3,972		$	3,920
Leasehold improvements		4,469			4,469
Computer equipment and software		237			241
Construction in process		10,593			9,703
Tooling		1,109			1,109
Furniture and fixtures		47			47
		20,427			19,489
Less accumulated depreciation and amortization		(8,944	)		(8,438	)
Property and equipment, net	$	11,483		$	11,051

Depreciation and amortization expense was

$0.5

million,

$1.7

million and

$2.1

million during the years ended

December

31,

2018,

2017

and

2016,

respectively.

Note 5 - Adoption of ASC Topic 606, Revenue From Contracts With Customers

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Revenue from Contract with Customer [Text Block]

Adoption of ASC Topic

606,

Revenue from Contracts with Customers

January 1, 2018,

the Company adopted Topic

606

using the modified retrospective method applied to those contracts which were

not

completed as of

January 1, 2018.

Results for reporting periods beginning after

January 1, 2018,

are presented under Topic

606,

while prior period amounts are

not

adjusted and continue to be reported in accordance with the Company’s historical accounting under Topic

605.

The adoption of the new revenue recognition guidance resulted in

changes to deferred revenue or the accumulated deficit as of

January

2018.

Revenue Recognition

As described in Note

“Organization and Summary of Significant Accounting Policies,” the Company has entered into the Amended Agreements with Grünenthal related to Zalviso. At

December 31, 2018,

approximately

$3.5

million of the transaction price under the Amended Agreements is allocated to the discount on future manufacturing services, which the Company expects to be recognized through

2029.

For additional detail on the Company’s accounting policy regarding revenue recognition, refer to Note

“Organization and Summary of Significant Accounting Policies - Revenue Recognition.”

The following table presents changes in the Company’s contract liabilities for the year ended

December 31, 2018:

	Balance at Beginning of the Period		Additions		Deductions			Balance at the end of the Period
	(in thousands)
Contract liability:
Deferred revenue	$	3,825	$	-	$	(362	)	$	3,463

During the year ended

December 31, 2018,

the Company recognized the following revenue (in thousands):

	Year ended December 31 , 2018
Amounts included in contract liabilities at the beginning of the period:
Performance obligations satisfied – Amended Agreements	$	362
New activities in the period from performance obligations satisfied:
Performance obligations satisfied – Amended Agreements		566
Total revenue from performance obligations satisfied		928
Royalty revenue		385
Contract and other		838
Total revenue	$	2,151

Note 6 - U.S. Department of Defense Funding	12 Months Ended
Note 6 - U.S. Department of Defense Funding	Dec. 31, 2018
Notes to Financial Statements
Long-term Contracts or Programs Disclosure [Text Block]	6 . U.S. Department of Defense Funding On May 11, 2015, the Company entered into an award contract (referred to as the DoD Contract) supported by the Clinical and Rehabilitative Medicine Research Program, or CRMRP, of the United States Army Medical Research and Materiel Command, or the USAMRMC, within the U.S. Department of Defense, or the DoD, in which the DoD agreed to provide up to $17.0 million to the Company in order to support the development of DSUVIA (sufentanil sublingual tablet, 30 mcg), a proprietary, non-invasive, single-use tablet in a disposable, pre-filled single-dose applicator, or SDA, for the treatment of moderate-to-severe acute pain. Under the terms of the DoD Contract, the DoD has reimbursed the Company for costs incurred for development, manufacturing, regulatory and clinical costs outlined in the DoD Contract, including reimbursement for certain personnel and overhead expenses. The period of performance under the DoD Contract began on May 11, 2015. The DoD Contract gives the DoD the option to extend the term of the DoD Contract and provide additional funding for the research. On March 2, 2016, the DoD Contract was amended to approve enrollment of additional patients in the SAP302 study, approve the addition of the SAP303 study, and extend the DoD Contract period of performance by four months from November 10, 2016 to March 9, 2017, to accommodate the increased SAP302 patient enrollment and the SAP303 study. The costs for these changes were included within the current DoD Contract value. On March 9, 2017, the DoD Contract was amended to incorporate additional activities including the development and testing of packaging changes; additional stability testing; and preparation for any FDA advisory committee meeting for DSUVIA. The amendment also extends the DoD Contract period of performance by 11 months through February 28, 2018 to accommodate these additional activities. At December 31, 2017, the additional activities as outlined under the DoD Contract through February 28, 2018 were substantially complete. On February 28, 2018, the DoD contract was amended to incorporate additional services in the amount of $0.5 million and to extend the contract period by twelve months through February 28, 2019. The DoD has the option to purchase a certain number of units of commercial product pursuant to the terms of the DoD Contract. Revenue is recognized based on expenses incurred by the Company in conducting research and development activities, including overhead, as set forth in the agreement. Revenue attributable to the work performed under the DoD Contract, recorded as Contract and other revenue in the Consolidated Statements of Comprehensive Loss, was $0.8 million, $0.9 million and $10.9 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Note 7 - Collaboration Agreement

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Collaborative Arrangement Disclosure [Text Block]

Collaboration Agreement

As described in Note

“Organization and Summary of Significant Accounting Policies,” as of

January 1, 2018,

the Company follows the guidance of ASC

606,

Revenue from Contracts with Customers

to account for revenue from its Agreements with Grünenthal related to Zalviso. In the Amended Agreements, the parties amended the Product supply configurations and packaging of Product components and accessories, and associated pricing therefor, which the Company will manufacture and supply to Grünenthal for the Territory. The parties agreed to increase the pricing of the Product components and accessories in exchange for a reduction of

$5.5

million in the total milestone payments due from Grünenthal contingent upon achieving specified net sales targets from a total of

$171.5

million to

$166.0

million. The parties also updated the development plan for the Product in the Territory, providing for additional near-term development services to be rendered by AcelRx in exchange for payments by Grünenthal of

$0.7

million. In accordance with the terms of the Amended MSA, AcelRx also received a binding Product forecast from Grünenthal for approximately

$3.7

million, which was fully delivered by the end of

2016.

Amended License Agreement

Under the terms of the Amended License Agreement, Grünenthal has the exclusive right to commercialize the Product in the Field in the Territory. The Company retains control of clinical development, while Grünenthal and the Company will be responsible for certain development activities pursuant to a development plan as agreed between the parties. The Company will

not

receive separate payment for such development activities, apart from the

$0.7

million included under the Amended Agreements. Grünenthal is exclusively responsible for marketing approval applications and other regulatory filings relating to the sufentanil sublingual tablet drug cartridge for the Product in the Field in the Territory, while the Company is responsible for the CE Mark and other regulatory filings relating to device portions of the Product. A CE Mark for Zalviso was obtained in the

fourth

quarter of

2014

which specifies AcelRx as the device design authority and manufacturer. In

September 2015,

the European Commission approved the MAA for Zalviso for the

EU member states as well as for the EEA. In

April 2016,

Grünenthal completed the

first

commercial sale of Zalviso.

The Company received an upfront non-refundable cash payment of

$30.0

million in

December 2013,

and a milestone payment of

$5.0

million related to the MAA submission in the

third

quarter of

2014,

and an additional

$15.0

million milestone payment upon the EC approval of the MAA for Zalviso, which was approved in

September 2015.

Under the Amended License Agreement, the Company is eligible to receive approximately

$194.5

million in additional milestone payments, based upon successful regulatory and product development efforts (

$28.5

million) and net sales target achievements (

$166.0

million). Grünenthal will also make tiered royalty and supply and trademark fee payments in the mid-teens up to the mid-twenties percent range, depending on the level of sales achieved, on net sales of Zalviso. A portion of the tiered royalty payment, exclusive of the supply and trademark fee payments, will be paid to PDL in connection with the Royalty Monetization. For additional information on the Royalty Monetization with PDL, see Note

“Liability Related to Sale of Future Royalties”. Unless earlier terminated, the Amended License Agreement continues in effect until the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments, which supply and trademark fee continues for so long as the Company continues to supply the Product to Grünenthal. The Amended License Agreement is subject to earlier termination in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party, upon the bankruptcy or insolvency of either party, or by Grünenthal for convenience.

Amended MSA

Under the terms of the Amended MSA, the Company will manufacture and supply the Product for use in the Field for the Territory exclusively for Grünenthal. Grünenthal shall purchase from AcelRx, during the

first

five

years after the effective date of the MSA, or

December 16, 2013

through

December 15, 2018,

100%

and thereafter

80%

of Grünenthal’s and its sublicensees’ and distributors’ requirements of Product for use in the Field for the Territory. The Product will be supplied at a predetermined transfer price, subject to certain caps, as defined in the Amended MSA. The Company will

not

recover internal indirect costs as part of this predetermined transfer price. In addition, the Amended MSA includes declining maximum transfer prices over the term of the contract with Grünenthal. The Amended MSA requires the Company to use commercially reasonable efforts to enter stand-by contracts with

third

parties providing significant supply and manufacturing services and, under certain specified conditions, permits Grünenthal to use a

third

party back-up manufacturer to manufacture the Product for Grünenthal’s commercial sale in the Territory.

Unless earlier terminated, the Amended MSA continues in effect until the later of the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments or the end of any transition period for manufacturing obligations due to the expiration or termination of the Amended License Agreement. The Amended MSA is subject to earlier termination in connection with certain termination events in the Amended License Agreement, in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party or upon the bankruptcy or insolvency of either party.

Prior to the adoption of ASC Topic

606

January 1, 2018,

the Company followed the provisions of ASC Topic

605.

However, as described in Note

the adoption of the new guidance did

not

have a material impact on the Company’s consolidated financial statements and did

not

result in any change to the initial allocation that was performed under Topic

605.

The Company identified

four

significant performance obligations under the original Agreements:

) intellectual property (license),

) the obligation to provide research and development services,

) the significant and incremental discount on the manufacturing of Zalviso for commercial purposes, and

) the obligation to participate in the joint steering committee.

At the time the Amended Agreements were executed, with the exception of the intellectual property license, these obligations remained partially unsatisfied. Additionally, the Company identified the following

three

additional performance obligations under the Amended Agreements:

) the obligation to provide additional research and development services,

) the obligation to provide Zalviso demonstration device systems, and

) the obligation to manufacture and deliver Product under the binding forecast. The Company determined that the amendments under the Amended Agreements were modifications to the original Agreements.

The Company determined that the performance obligations outlined above are considered distinct and thus should be treated as separate units of accounting. The Company’s management determined that the license under the original License Agreement was distinct and represented a separate unit of accounting because it is considered functional intellectual property and the rights conveyed permitted Grünenthal to perform all efforts necessary to commercialize and begin selling the product upon regulatory approval. In addition, Grünenthal has the appropriate development, regulatory and commercial expertise with products similar to the product licensed under the agreement and has the ability to engage

third

parties to manufacture the product allowing Grünenthal to realize the value of the license on its own without receiving any of the remaining deliverables. Grünenthal can also sublicense its license rights to

third

parties. Also, the Company’s management determined that the research and development services, Zalviso demonstration device systems, joint steering committee participation, the significant and incremental discount on the manufacturing of Zalviso, and the obligation to manufacture and deliver Products each represent individual units of accounting. Each of the obligations meet the criteria to be considered distinct as Grünenthal could perform such services and/or could acquire these on a separate basis and

none

of the obligations are contractually dependent on other obligations within the contract.

The Company believes that

none

of the performance obligations have an observable price, vendor-specific objective evidence, or VSOE, or sufficient

third

-party evidence, or TPE, of selling price, as

none

of them have been sold separately by the Company, and as there is only limited information about

third

party pricing for similar deliverables. Accordingly, the Company developed the stand alone selling price for each performance obligation in order to allocate the fixed arrangement consideration to each performance obligation, based on current information available as of the modification date.

The Company’s management determined the standalone selling price for the license based on Grünenthal’s estimated future cash flows arising from the arrangement. Embedded in the estimate were significant assumptions regarding regulatory expenses, revenue, including potential customer market for the product and product price, costs to manufacture the product and the discount rate. The Company’s management determined the standalone selling price of the research and development services and committee participation based on the nature and timing of the services to be performed and in consideration of personnel and other costs incurred in the delivery of the services. For the discount on manufacturing services, the Company’s management estimated the selling price based on the market level of contract manufacturing margin it could have received if it were engaged to supply products to a customer in a separate transaction, the estimated cost of manufacturing, and the anticipated volume of Grünenthal’s orders over the course of the agreement, to which the discount would apply. For the Zalviso demonstration devices and the obligation to manufacture and deliver Product, the Company’s management estimated the selling price based on the binding volume of such devices and Products, the estimated cost of manufacturing, and the market level of contract manufacturing margin. The standalone selling price of the license, research and development and committee participation services and the discount on manufacturing services were updated at the time the Amended Agreements were executed for purposes of allocating the amended arrangement consideration.

The original Agreements included

two

milestones associated with the regulatory developments for Zalviso in Europe. Aggregate potential payments for these milestones totaled

$20.0

million. In

July 2014,

Grünenthal submitted an MAA to the EMA for Zalviso for the management of acute moderate-to-severe post-operative pain in adult patients, triggering the

first

of these

two

milestones, a cash payment of

$5.0

million. In

September

2015,

the MAA was approved by the European Commission, triggering the

second

of these

two

milestones, a cash payment of

$15.0

million. As of the date of adoption of Topic

606

January 1, 2018,

the

$20.0

million in development milestones are considered fixed consideration and included in the transaction price. Amounts received for these milestones were allocated to performance obligations based on their standalone selling prices and recognized as appropriate for each obligation. As of

December 31, 2018,

the Company has excluded the remaining milestone payment of

$1.0

million related to the Australia sub-license from the transaction price due to the constraint on variable consideration.

The Amended Agreements entitle the Company to receive additional payments upon the achievement of certain development milestones which relate to post approval product enhancements, expanded market opportunities and manufacturing efficiencies for Zalviso and require future research, development and regulatory activities. These payments are excluded from the transaction price as they are considered payments for optional additional services that Grünenthal

may

elect in the future. When these services are elected, they will be considered as a new contract under Topic

606

and will

not

impact the revenue recognition of the performance obligations identified under Amended Agreements.

The Amended Agreements also include milestone payments related to specified net sales targets, totaling

$166.0

million. These payments are considered sales-based license royalties under Topic

606

and will be recognized apart from the other contract consideration when the related sales occur.

The Company recognizes revenue from license rights when the customer can use and benefit from the license rights. The Company recognizes revenue from its services performance obligations over time using a cost-to-cost input method which best represents the incremental benefit that the customer receives as control is transferred.

Below is a summary of revenue recognized under the Amended Agreements during the years ended

December 31, 2018,

2017

and

2016

(in thousands):

	Years Ended December 31,
	201 8		2017		201 6
Product sales	$	825	$	6,673	$	5,742
Joint steering committee, research and development services and demonstration devices		103		269		688
Non-cash royalty revenue related to Royalty Monetization (See Note 9)		289		151		7
Royalty revenue		96		50		3
Total	$	1,313	$	7,143	$	6,440

As of

December 31, 2018,

the Company has deferred current and noncurrent portions of the transaction price that is allocated to the performance obligations that are unsatisfied (or partially unsatisfied) under the Amended Agreements of

$0.3

million and

$3.2

million, respectively.

Note 8 - Long-term Debt

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Long-term Debt [Text Block]

. Long-Term Debt

Amended

Loan and Security Agreement

December

16,

2013,

AcelRx entered into an Amended and Restated Loan and Security Agreement with Hercules Technology II, L.P. and Hercules Capital, Inc., formerly known as Hercules Technology Growth Capital, Inc., together, the Lenders, or the Original Loan Agreement, under which the Company was provided the ability to borrow up to

$40.0

million in

three

tranches. The loans were represented by secured convertible term promissory notes, collectively, the

2013

Notes. The Original Loan Agreement amended and restated the prior Loan and Security Agreement between the Company and the Lenders dated as of

June

29,

2011.

The Company borrowed the

first

tranche of

$15.0

million upon closing of the transaction on

December

16,

2013,

and the

second

tranche of

$10.0

million on

June 16, 2014.

The Company used approximately

$8.6

million of the proceeds from the

first

tranche to repay its obligations under the prior Loan and Security Agreement with the Lenders. The Company recorded the new debt at an estimated fair value of

$24.9

million as of

December 31, 2014.

In connection with the Original Loan Agreement, the Company issued a warrant to each Lender which, collectively, are exercisable for an aggregate of

176,730

shares of common stock and each carried an exercise price of

$6.79

per share.

September

24,

2014,

the Company entered into Amendment

No.

to the Original Loan Agreement with the Lenders. Amendment

No.

extended the time period under which the Company could draw down the

third

tranche, of up to

$15.0

million, from

March

15,

2015

August

2015,

subject to the Company obtaining approval for Zalviso from the FDA. The Company did

not

receive FDA approval of Zalviso by

August 1, 2015

and as such, did

not

have access to the

third

tranche.

September 18, 2015,

concurrently with the closing of the Royalty Monetization, the Company entered into a Consent and Amendment

No.

or Amendment

No.

to the Original Loan Agreement with the Lenders. Amendment

No.

includes an interest only period from

October 1, 2015

through

March 31, 2016,

with further extension to

September 30, 2016

upon satisfaction of certain conditions. These conditions were satisfied in the

third

quarter of

2015

and the interest only period was extended through

September 30, 2016.

Loans under the Original Loan Agreement were scheduled to mature on

October 1, 2017.

In connection with Amendment

No.

the Company reduced the exercise price of the warrants already held by the Lenders, which are exercisable for an aggregate of

176,730

shares of Common Stock, from the previous exercise price of

$6.79

per share to

$3.88

per share.

September 30, 2016,

the Company entered into Amendment

No.

to the Original Loan Agreement with the Lenders. Among other things, Amendment

No.

extended the interest-only period from

October 1, 2016

April 1, 2017.

In connection with Amendment

No.

the Company reduced the exercise price of the existing warrants held by the Lenders, which are exercisable for an aggregate of

176,730

shares of common stock, from the previous exercise price of

$3.88

per share to

$3.07

per share.

March 2, 2017,

the Company amended and restated the Original Loan Agreement with the Lenders, which is referred to as the Amended Loan Agreement. Pursuant to the Amended Loan Agreement, the Company borrowed the

first

tranche of approximately

$20.5

million upon closing of the transaction on

March 2, 2017,

which is represented by secured term promissory notes, or the Notes. The Company used all of the proceeds from the

first

tranche to repay its obligations under the Original Loan Agreement, including a final payment of

$1.7

million made on

October 1, 2017.

The interest rate is calculated at a rate equal to the greater of either (i)

9.55%

plus the prime rate as reported from time to time in The Wall Street Journal minus

3.50%,

and (ii)

9.55%.

Payments under the Amended Loan Agreement were interest-only until

October 1, 2017

followed by equal monthly payments of principal and interest through the scheduled maturity date of

March 1, 2020.

A final payment equal to

6.5%

of the aggregate principal amount of loans funded under the Amended Loan Agreement, or End of Term Fee, or EOT Fee, will be due on the earliest of (i) the maturity date, (ii) prepayment in full of the loans (other than by a refinancing with Hercules) or (iii) the date on which the loans under the Amended Loan Agreement become due and payable. The Company’s obligations under the Amended Loan Agreement are secured by a security interest in substantially all of its assets, other than its intellectual property.

If the Company prepays the loans under the Amended Loan Agreement prior to the maturity date, it will pay Hercules a prepayment charge, based on a percentage of the then outstanding principal balance, equal to

if the prepayment occurs after

March 2, 2018,

but prior to

March 2, 2019,

if the prepayment occurs after

March 2, 2019.

The Amended Loan Agreement includes customary affirmative and restrictive covenants, but does

not

include any financial maintenance covenants, and also includes standard events of default, including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of Hercules’ security interest or in the value of the collateral, and events relating to bankruptcy or insolvency. Upon the occurrence of an event of default, a default interest rate of an additional

may

be applied to the outstanding loan balances, and Hercules

may

declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Amended Loan Agreement.

Upon an event of default, including a change of control, Hercules has the option to accelerate repayment of the Amended Loan Agreement, including payment of any applicable prepayment charges. This option is considered a contingent put option liability, as the holder of the loan has the ability to exercise the option in the event of default, and is considered an embedded derivative, which must be valued and separately accounted for in the Company’s financial statements. As the Original Loan Agreement entered into on

December 16, 2013

was considered an extinguishment, the contingent put option liability associated with the prior Loan and Security Agreement, which had an estimated fair value of

$32

thousand at the time of the amendment, was written off as a part of the loss on extinguishment, and a new contingent put option liability was established. As of

December 31, 2018

and

2017,

the estimated fair value of the contingent put option liability was

$0.1

million and

$0.2

million, respectively, which was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the

two

estimated fair values is the estimated fair value of the default provisions, or the contingent put option. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default and discounting such cash flows back to the reporting date using a risk-free rate. The contingent put option liability is revalued at the end of each reporting period and any change in the fair value is recognized in interest income and other income, net in the Consolidated Statements of Comprehensive Loss.

The Company performed an analysis of Amendments

No.

and

No.

to determine if each amendment was a modification or extinguishment of the debt under the Original Loan Agreement. The Company assumed immediate prepayment of both the pre-modification debt and post-modification debt, including the change in the fair value due to the warrant amendments, and concluded that Amendments

No.

and

No.

were each modifications rather than extinguishments of the debt.

The accrued balance due under the Amended Loan Agreement was

$12.0

million and

$19.1

million at

December 31, 2018

and

2017,

respectively. Interest expense related to the Amended Loan Agreement was

$2.2

million,

$3.3

million and

$2.8

million for the years ended

December 31, 2018,

2017

and

2016,

respectively.

Future Payments on Long-Term Debt

The following table summarizes the outstanding future payments associated with the Company’s long-term debt as of

December

31,

2018

(in thousands):

2019	$	9,437
2020		3,701

Total payments		13,138
Less amount representing interest		(872	)

Notes payable, gross		12,266
Unamortized portion of final payment		(229	)
Unamortized discount on notes payable		(46	)

Long-term debt		11,991
Less current portion of notes payable, including unamortized discount		(8,611	)

Long-term debt, current portion	$	3,380

Note 9 - Liability Related to Sale of Future Royalties

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

. Liability Related to Sale of Future Royalties

September 18, 2015,

the Company consummated the Royalty Monetization, in which it sold certain royalty and milestone payment rights to its newly formed wholly owned subsidiary, ARPI LLC, pursuant to a Purchase and Sale Agreement, or PSA. Subsequently, ARPI LLC sold the royalty and milestone payment rights to PDL for an upfront cash purchase price of

$65.0

million, subject to a capped amount of

$195.0

million pursuant to the Subsequent Purchase and Sale Agreement, or SPSA. Under the SPSA, PDL will receive

75%

of the European royalties under the Amended License Agreement as well as

80%

of the

first

four

commercial milestones, worth

$35.6

million (or

80%

$44.5

million), subject to the capped amount. The Company is entitled to receive

25%

of the royalties,

20%

of the

first

four

commercial milestones,

100%

of the remaining commercial milestones and all remaining development milestones of

$43.5

million, including the

$15.0

million payment for the EC approval of the MAA for Zalviso.

The Company and ARPI LLC continue to retain certain duties and obligations under the Amended License Agreement. These include the collection of the royalty and milestones amounts due and enforcement of related provisions under the Amended License Agreement, among others. In addition, the Company must prepare a quarterly distribution report relating to the Amended License Agreement, containing among other items, the amount of royalty and milestone payments received, reimbursable expenses and set-offs. The Company and ARPI LLC must also provide PDL with notice of certain communications, events or actions with respect to the Amended License Agreement and infringement of any underlying intellectual property.

The Company has significant continuing involvement in the Royalty Monetization primarily due to an obligation to act as the intermediary for the supply of Zalviso to Grünenthal. Under the relevant accounting guidance, because of its significant continuing involvement, the Royalty Monetization has been accounted for as a liability that will be amortized using the effective interest method over the life of the arrangement. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future royalty and milestone payments to be received by ARPI LLC and paid to PDL, up to a capped amount of

$195.0

million, over the life of the arrangement. The aggregate future estimated royalty and milestone payments (subject to the capped amount), less the

$61.2

The Company periodically assesses the expected royalty and milestone payments using a combination of historical results, internal projections and forecasts from external sources. To the extent such payments are greater or less than the Company’s initial estimates or the timing of such payments is materially different than its original estimates, the Company will prospectively adjust the amortization of the liability and the effective interest rate. From inception through

December 31, 2018,

the Company’s effective annual interest rate was approximately

13.0%;

however, currently the prospective rate is estimated to be approximately

7.0%

as a result of lower projected European royalties from sales of Zalviso over the life of the liability because the product launch has been slower than originally anticipated. The effective interest rate for the years ended

December 31, 2018,

2017

and

2016,

was

11.6%,

13.6%,

and

13.7%,

respectively.

There are a number of factors that could materially affect the amount and timing of royalty payments from Zalviso in Europe, most of which are

not

within the Company’s control. Such factors include, but are

not

The following table shows the activity within the liability account during the year ended

December 31, 2018 (

in thousands):

	Year ended December 31, 201 8			Period from inception to December 31, 201 8
Liability related to sale of future royalties — beginning balance	$	83,588		$	—
Proceeds from sale of future royalties		—			61,184
Non-cash royalty revenue		(250	)		(377	)
Non-cash interest expense recognized		10,341			32,872
Liability related to sale of future royalties as of December 31, 2018		93,679			93,679
Less: current portion		(392	)		(392	)
Liability related to sale of future royalties — net of current portion	$	93,287		$	93,287

As royalties are remitted to PDL from ARPI LLC, as described in Note

“Organization and Summary of Significant Accounting Policies,” the balance of the liability will be effectively repaid over the life of the agreement. The Company will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the Royalty Monetization.

Note 10 - Warrants	12 Months Ended
Note 10 - Warrants	Dec. 31, 2018
Notes to Financial Statements
Warrants Disclosure [Text Block]	10 . Warrants Amended and Restated Loan Agreement Warrants In connection with the Original Loan Agreement, executed in December 2013, the Company issued warrants to the Lenders which were exercisable for an aggregate of 176,730 shares of common stock with an exercise price of $6.79 per share, or the Warrants. In connection with Amendment No. 2 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $6.79 per share to $3.88 per share, or the First Warrant Amendments. In connection with Amendment No. 3 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $3.88 per share to $3.07 per share, or the Second Warrant Amendments. Each Warrant may be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of five years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants. The Company estimated the fair value of these Warrants as of the issuance date to be $1.1 million, which was used in the estimating of the fair value of the amended debt instrument and was recorded as equity. The fair value of the Warrants was calculated using the Black-Scholes option-valuation model, and was based on the original strike price of $6.79, the stock price at issuance of $9.67, the five -year contractual term of the warrants, a risk-free interest rate of 1.55%, expected volatility of 71% and 0% expected dividend yield. The Company estimated the fair value of the modification of the First Warrant Amendments, as of the issuance date to be $0.1 million, which was used in estimating the fair value of the amended debt instrument in September 2015 and was recorded as equity, as well as the Second Warrant Amendments, which fair value was estimated to be $45.0 thousand at the issuance date, and which was used in estimating the fair value of the amended debt instrument in September 2016 and was recorded as equity. In December 2018, all of the outstanding warrants were exercised to purchase 176,730 shares of common stock which were issued to the Lenders. 2012 Private Placement Warrants In connection with the Private Placement, completed in June 2012, the Company issued PIPE warrants to purchase up to 2,630,103 shares of common stock. The per share exercise price of the PIPE warrants was $3.40 which equals the closing consolidated bid price of the Company’s common stock on May 29, 2012, the effective date of the Purchase Agreement. The PIPE warrants issued in the Private Placement became exercisable six months after the issuance date and expire on the five year anniversary of the initial exercisability date. Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of 50% of the Company’s issued and outstanding common stock, which is outside of the Company’s control, each PIPE warrant holder may elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model. Accordingly, the PIPE warrants were recorded as a liability at fair value, as determined by the Black-Scholes option-pricing model, and then marked to fair value each reporting period, with changes in estimated fair value recorded through the Consolidated Statements of Comprehensive Loss in interest income and other income (expense), net. The Black-Scholes assumptions used to value the PIPE warrants are disclosed in Note 2 “Investments and Fair Value Measurement.” Upon execution of the Purchase Agreement, the fair value of the PIPE warrants was estimated to be $5.8 million, which was recorded as a liability. The change in fair value for the years ended December 31, 2017 and 2016, which was recorded as other income, was $0.3 million and $0.6 million, respectively. During the year ended December 31, 2017, 512,456 warrants expired unexercised.

Note 11 - Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Commitments and Contingencies Disclosure [Text Block]

. Commitments and

Contingencies

Operating Leases

December 2011,

the Company entered into a non-cancelable lease agreement with Metropolitan Life Insurance Company, or the Landlord, referred to as the Existing Lease, for approximately

13,787

square feet of office and laboratory facilities located at

301

Galveston Drive, Redwood City, California, or the Current Premises, which serve as the Company headquarters, effective

April 2012.

Rent expense from the facility lease is recognized on a straight-line basis from the inception of the lease in

December 2011,

the early access date, through the end of the lease.

May 2014,

the Company entered into an amendment, or the Lease Amendment, to the Existing Lease for the Current Premises. Pursuant to the Lease Amendment, the term of the Existing Lease was extended for a period of

twenty

(

) months and

twenty-two

(

) days and expiring on

January 31, 2018,

unless sooner terminated pursuant to the terms of the Existing Lease. In addition, the Lease Amendment included a new lease on an additional approximately

12,106

square feet of office space located at

351

Galveston Drive in Redwood City, California, or the Expansion Space, which is adjacent to the Current Premises. The lease for the Expansion Space had a term of

months which commenced on

August 1, 2014

and expired on

January 31, 2018.

October 2, 2015,

the Company executed an agreement to sublease approximately

11,871

square feet of the Expansion Space for a term of

months commencing on

December 1, 2015.

The sublessee was entitled to abatement of the

first

two

monthly installments of rent. Subsequent monthly installments of rent start at a rental rate of

$2.05

per square foot (subject to agreed nominal increases). Minimum rents received under this sublease were

$25.0

thousand and

$0.3

million for the years ended

December 31, 2018

and

2017,

respectively.

June 14, 2017,

the Company entered into a

second

amendment, or the Second Lease Amendment, to the Existing Lease, and as amended by the Second Lease Amendment, the Lease, with the Landlord, for approximately

25,893

square feet located at

301

–

351

Galveston Drive, Redwood City, California, or the Current Premises and the Expansion Space, together, the Premises. Pursuant to the Second Lease Amendment, the term of the Existing Lease has been extended for a period of

seventy-two

(

) months, or the Extended Term, beginning

February 1, 2018

and expiring

January 31, 2024,

or the Expiration Date, unless sooner terminated pursuant to the terms of the Lease.

January 2, 2019,

the Company entered into an agreement to sublease

12,106

square feet of the Expansion Space commencing on

February 16, 2019

and expiring on

January 31, 2024.

Rent installments from the sublessee are approximately

$48,000

per month (subject to agreed nominal increases).

Pursuant to the Lease Amendment, the Company will pay on a monthly basis annual rent of approximately

$1.2

million, with annual increases each

-month period beginning

February 1

, and the

first

two

months to be abated provided that the Company is

not

in default thereunder. In addition, the Company will pay the Landlord specified percentages of certain operating expenses related to the leased facility incurred by the Landlord.

Rent expense was

$1.1

million,

$0.6

million and

$0.3

million for the Premises during the years ended

December

31,

2018,

2017

and

2016,

respectively.

Future minimum payments under the Lease as of

December

31,

2018,

are as follows (in thousands):

Year Ending December 31:
2019	$	1,230
2020		1,268
2021		1,305
2022		1,345
2023		1,386
Thereafter		116
Total minimum payments	$	6,650

Litigation

From time to time the Company

may

be involved in legal proceedings arising in the ordinary course of business. The Company does

not

have contingent liabilities established for any litigation matters.

Note 12 - Stockholders' Equity	12 Months Ended
Note 12 - Stockholders' Equity	Dec. 31, 2018
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	1 2 . Stockholders’ Equity Common Stock 2018 Underwritten Public Offerings On November 14, 2018, the Company completed an underwritten public offering of 12,698,412 shares of common stock, at a price of $3.15 per share to the public. On November 12, 2018, the underwriters exercised their option in full and purchased an additional 1,904,761 shares at the public offering price of $3.15 per share. The total gross proceeds from this offering of an aggregate 14,603,173 shares were approximately $46.0 million with net proceeds to the Company of $43.1 million after deducting the underwriting discounts and commissions and other offering expenses payable by us. On July 16, 2018, the Company completed an underwritten public offering of 7,272,727 shares of common stock, at a price of $2.75 per share to the public. On August 7, 2018, the underwriters exercised in full their option to purchase an additional 1,090,909 shares of common stock at the public offering price of $2.75 per share, less underwriting discounts and commissions. The total gross proceeds from this offering of an aggregate 8,363,636 shares were approximately $23.0 million with net proceeds to the Company of $21.7 million after deducting the underwriting discounts and commissions and other offering expenses payable by the Company. 201 6 ATM Agreement On June 21, 2016, the Company entered into a Controlled Equity Offering SM Sales Agreement, or the Sales Agreement, or 2016 ATM Agreement, with Cantor Fitzgerald & Co., or Cantor, as agent, pursuant to which the Company may offer and sell, from time to time through Cantor, shares of the Company’s common stock, or the Common Stock having an aggregate offering price of up to $40.0 million, or the Shares. The offering of Shares pursuant to the Sales Agreement will terminate upon the earlier of (a) the sale of all of the Shares subject to the Sales Agreement or (b) the termination of the Sales Agreement by Cantor or the Company, as permitted therein. The Company will pay Cantor a commission rate in the low single digits on the aggregate gross proceeds from each sale of Shares and have agreed to provide Cantor with customary indemnification and contribution rights. During the year ended December 31, 2018, the Company issued and sold an aggregate of 4.4 million shares of common stock pursuant to the Sales Agreement, for which the Company received net proceeds of approximately $16.8 million, after deducting commissions, fees and expenses of $0.4 million. During the year ended December 31, 2017, the Company issued and sold 5.4 million shares of common stock pursuant to the 2016 ATM Agreement, for which the Company received net proceeds of approximately $15.7 million, after deducting commissions, fees and expenses of $0.5 million. Stock Plans 2006 Stock Plan In August 2006, the Company established the 2006 Plan in which 342 shares of common stock were originally reserved for the issuance of incentive stock options, or ISOs, and nonstatutory stock options, or NSOs, to employees, directors or consultants of the Company. In February 2008, an additional 375 shares of common stock were reserved for issuance under the 2006 Plan and, in November 2009, an additional approximately 1.4 million shares of common stock were reserved for issuance under the 2006 Plan. Per the 2006 Plan, the exercise price of ISOs and NSOs granted to a stockholder who at the time of grant owns stock representing more than 10% of the voting power of all classes of the stock of the Company could not be less than 110% of the fair value per share of the underlying common stock on the date of grant. Effective upon the execution and delivery of the underwriting agreement for the Company’s IPO, no additional stock options or other stock awards may be granted under the 2006 Plan. 2011 Equity Incentive Plan In January 2011, the Board of Directors adopted, and the Company’s stockholders approved, the 2011 Equity Incentive Plan, or 2011 Incentive Plan, as a successor to the 2006 Plan. The 2011 Incentive Plan became effective immediately upon the execution and delivery of the underwriting agreement for the IPO on February 10, 2011. As of February 10, 2011, no more awards may be granted under the 2006 Plan, although all outstanding stock options and other stock awards previously granted under the 2006 Plan will continue to remain subject to the terms of the 2006 Plan. The approximately 52 shares reserved under the 2006 Plan that remained available for future grant at the time of the IPO were transferred to the share reserve of the 2011 Incentive Plan. The initial aggregate number of shares of the Company’s common stock that may be issued pursuant to stock awards under the 2011 Incentive Plan is approximately 1.9 million shares, which number was the sum of (i) 52 shares remaining available for future grant under the 2006 Plan at the time of the execution and delivery of the underwriting agreement for the Company’s IPO, and (ii) an additional approximately 1.8 million new shares. Then, the number of shares of common stock reserved for issuance under the 2011 Incentive Plan will automatically increase on January 1st each year, starting on January 1, 2012 and continuing through January 1, 2020, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the Board of Directors. The term of the option is determined by the Board of Directors on the date of grant but shall not be longer than 10 years. Options under the 2011 Equity Incentive Plan generally vest over four years, and all options expire after 10 years. The Company issues new shares for settlement of vested restricted stock units and exercises of stock options. The Company does not have a policy of purchasing its shares relating to its share-based programs. 2011 Employee Stock Purchase Plan Additionally, in January 2011, the Board of Directors adopted, and the Company’s stockholders approved, the 2011 Employee Stock Purchase Plan, or the ESPP, which also became effective immediately upon the execution and delivery of the underwriting agreement for the IPO. Initially, 250 shares of the Company’s common stock were authorized for issuance under the ESPP pursuant to purchase rights granted to the Company’s employees or to employees of any of its designated affiliates. The number of shares of the Company’s common stock reserved for issuance will automatically increase on January 1st each year, starting January 1, 2012 and continuing through January 1, 2020, in an amount equal to the lower of ( 1 ) 2% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or ( 2 ) a number of shares of common stock as determined by the Board of Directors. If a purchase right granted under the ESPP terminates without having been exercised, the shares of the Company’s common stock not purchased under such purchase right will be available for issuance under the ESPP. As of December 31, 2018, there are 858,889 shares available for issuance under the ESPP. In the year ended December 31, 2018, there were 182,360 shares issued under the ESPP. The weighted average fair value of shares issued under the ESPP in 2018, 2017 and 2016 was $1.51, $2.59 and $2.98 per share, respectively.

Note 13 - Stock-based Compensation

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

. Stock-Based Compensation

The Company recorded total stock-based compensation expense for stock options, stock awards and the ESPP as follows
(in thousands):

	December 31, 201 8		December 31, 201 7		December 31, 201 6
Cost of goods sold	$	358	$	324	$	302
Research and development		1,970		1,901		2,308
General and administrative		2,840		2,069		1,869
Total	$	5,168	$	4,294	$	4,479

The following table summarizes option activity under the

2011

Incentive Plan and

2006

Plan:

	Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
								(in thousands)
December 31, 2017		8,455,098		$	4.25
Granted		3,553,713			2.28
Forfeited		(217,816	)		2.87
Expired		(232,905	)		6.36
Exercised		(135,385	)		2.96
December 31, 2018		11,422,705		$	3.64		7.1	$	659
Vested and exercisable options—December 31, 2018		6,468,788		$	4.44		5.8	$	46
Vested and expected to vest—December 31, 2018		11,422,705		$	3.64		7.1	$	659

As of

December

31,

2018,

there were

1,217,341

shares available for future grant under the

2011

Incentive Plan. In

January 2019,

an additional

3,150,317

shares were authorized for issuance under the

2011

Incentive Plan.

Additional information regarding the Company’s stock options outstanding and vested and exercisable as of

December

31,

2018

is summarized below:

			Options Outstanding						Options Vested and Exercisable
Exercise Prices			Number of Stock Options Outstanding		Weighted-Average Remaining Contractual Life (Years)		Weighted-Average Exercise Price per Share		Shares Subject to Stock Options		Weighted-Average Exercise Price per Share
$1.20	-	$2.00		1,856,170		9.0	$	2.00		6,900	$	1.20
$2.225	-	$3.35		5,406,951		7.8	$	2.82		2,698,203	$	2.82
$3.37	-	$5.31		2,855,022		5.2	$	4.13		2,459,123	$	4.19
$5.45	-	$8.18		688,562		5.0	$	6.47		688,562	$	6.47
$10.22	-	$10.55		616,000		5.1	$	10.34		616,000	$	10.34
				11,422,705		7.1	$	3.64		6,468,788	$	4.44

The weighted average grant-date fair value of options granted during the years ended

December

31,

2018,

2017

and

2016

was

$1.62,

$1.91

and

$2.24

per share, respectively. As of

December

31,

2018,

total stock-based compensation expense related to unvested options to be recognized in future periods was

$7.5

million which is expected to be recognized over a weighted-average period of

2.4

years. The grant date fair value of shares vested during the years ended

December

31,

2018,

2017

and

2016

was

$4.9

million,

$3.5

million and

$3.9

million, respectively. The total intrinsic value of options exercised during the years ended

December

31,

2018

and

2017

was

$0.2

million and

$40

thousand, respectively. There were

option exercises during the year ended

December 31, 2016.

The Company used the following assumptions to calculate the fair value of each employee stock option:

	Year Ended December 31,
	201 8			201 7			201 6
Expected term (in years)		5.89			5.70		5.25	-	6.25
Risk-free interest rate	2.5%	-	3.1%	1.82%	-	2.09%	1.24%	-	1.47%
Expected volatility		83%			73%			80%
Expected dividend rate		0%			0%			0%

Note 14 - Net Loss Per Share of Common Stock

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Earnings Per Share [Text Block]

14.

Net Loss per Share of Common Stock

The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, options to purchase common stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, common stock equivalents are excluded from the calculation of diluted net loss per share of common stock if their effect is antidilutive.

The PIPE warrants expired during the year ended

December 31, 2017.

During the year ended

December 31, 2016,

the exercise price of the PIPE warrants exceeded the average of AcelRx’s closing share price. As a result, the PIPE warrants were anti-dilutive during the year ended

December 31, 2016.

The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:

	Year Ended December 31,
	201 8		201 7		201 6
ESPP and stock options to purchase common stock		11,797,960		8,767,783		6,395,879
Convertible debt into common stock		—		—		553,763
Common stock warrants		—		176,730		692,611

Note 15 - Accrued Liabilities

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Accounts Payable and Accrued Liabilities Disclosure [Text Block]

15.

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	December 31,
	201 8		201 7
Accrued compensation and employee benefits	$	3,611	$	2,190
Inventory and other contract manufacturing accruals		234		511
Other accrued liabilities		695		842
Total accrued liabilities	$	4,540	$	3,543

Note 16 - 401(k) Plan	12 Months Ended
Note 16 - 401(k) Plan	Dec. 31, 2018
Notes to Financial Statements
Pension and Other Postretirement Benefits Disclosure [Text Block]	16. 401 (k) Plan The Company sponsors a 401 (k) plan that stipulates that eligible employees can elect to contribute to the 401 (k) plan, subject to certain limitations. Pursuant to the 401 (k) plan, the Company makes a matching contribution of up to 4% of the related compensation. Under the vesting schedule, employees have ownership in the matching Employer Contributions based on the number of years of vesting service completed. Company contributions were $0.3 million for each of the years ended December 31, 2018, 2017 and 2016.

Note 17 - Income Taxes

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Income Tax Disclosure [Text Block]

. Income Taxes

The Company recorded a provision for income taxes of

$2.0

thousand during the year ended

December 31, 2018,

a benefit for income taxes of

$0.7

million during the year ended

December 31, 2017,

and a benefit for income taxes of

$34.0

thousand during the year ended

December

31,

2016.

The provision (benefit) for income taxes consisted of the following (in thousands):

	December 31, 201 8		December 31, 201 7
Current:
Federal	$	—	$	(702	)
State		2		1
Total Current		2		(701	)
Deferred:
Federal		—		—
State		—		—
Total Deferred		—		—
Provision (benefit) for income taxes	$	2	$	(701	)

Net deferred tax assets as of

December

31,

2018

and

2017

consist of the following (in thousands):

	December 31, 201 8			December 31, 201 7
Deferred tax assets:
Accruals and other	$	3,263		$	2,717
Research credits		7,275			6,530
Net operating loss carryforward		39,082			31,064
Section 59(e) R&D expenditures		10,387			12,156
Deferred revenue		20,689			18,384
Total deferred tax assets		80,696			70,851
Valuation allowance		(80,696	)		(70,851	)
Net deferred tax assets	$	—		$	—

Reconciliations of the statutory federal income tax to the Company’s effective tax during the years ended

December

31,

2018,

2017

and

2016

are as follows (in thousands):

	Year Ended December 31,
	201 8			201 7			201 6
Tax at statutory federal rate	$	(9,901	)	$	(17,751	)	$	(14,685	)
State tax—net of federal benefit		(792	)		350			(73	)
PIPE warrant liability		(18	)		(70	)		(260	)
General business credits		(500	)		(316	)		(360	)
Stock options		1,048			42			1,115
Other		313			51			33
Change in valuation allowance		9,852			(17,110	)		14,196
Tax reform – tax rate change		—			34,103			—
Provision for income taxes	$	2		$	(701	)	$	(34	)

ASC

740

requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is “more likely than

not.”

Realization of deferred tax assets is dependent on future taxable income, if any, the timing and the amount of which are uncertain. Accordingly, the deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by

$9.9

million, decreased by

$17.1

million and increased by

$14.2

million during the years ended

December 31, 2018,

2017

and

2016,

respectively.

As of

December

31,

2018,

the Company had federal net operating loss carryforwards of

$153.2

million, of which

$114.9

million federal net operating losses generated before

January 1, 2018

will begin to expire in

2029.

Federal net operating losses of

$38.3

million generated in

2018

will carryforward indefinitely but are subject to the

80%

taxable income limitation. As of

December

31,

2018,

the Company had state net operating loss carryforwards of

$97.2

million, which begin to expire in

2028.

As of

December 31, 2017,

the Company had a federal alternative minimum tax credit carryover of

$0.7

million which is now refundable under the tax reform enacted on

December 22, 2017,

of which

$0.4

million is classified as Tax receivable on the Company’s balance sheet and

$0.3

million is classified as a Long-term tax receivable.

As of

December

31,

2018,

the Company had federal research credit carryovers of

$6.5

million, which begin to expire in

2026.

As of

December

31,

2018,

the Company had state research credit carryovers of

$4.0

million, which will carryforward indefinitely.

The Company adopted ASU

2016

in the year end

December 31, 2017.

The impact of this adoption resulted in gross increases of

$2.9

million and

$2.0

million to federal and state net operating losses, respectively, during the year ended

December 31, 2017.

The Company has recorded a full valuation allowance against its deferred tax assets.

Under Section

382

of the Internal Revenue Code of

1986,

as amended, if a corporation undergoes an “ownership change,” generally defined as a greater than

50%

change (by value) in its equity ownership over a

three

year period, the corporation’s ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes, such as research credits, to offset its post-change income

may

be limited. Based on an analysis performed by the Company as of

December

31,

2013,

it was determined that

two

ownership changes have occurred since inception of the Company. The

first

ownership change occurred in

2006

at the time of the Series A financing and, as a result of the change,

$1.4

million in federal and state net operating loss carryforwards will expire unutilized. In addition,

$26,000

in federal and state research and development credits will expire unutilized. The

second

ownership change occurred in

July 2013

at the time of the underwritten public offering; however, the Company believes the resulting annual imposed limitation on use of pre-change tax attributes is sufficiently high that the limit itself will

not

result in unutilized pre-change tax attributes.

December 22, 2017,

the Tax Cuts and Jobs Act of

2017

(the “Act”) was signed into law resulting in significant changes to the Internal Revenue Code. The Act reduced the federal corporate income tax rate decrease from

35%

21%

effective for tax periods beginning after

December 31, 2017,

changes U.S international taxation from a worldwide tax system to a territorial system, and a

one

-time transition tax on the untaxed cumulative foreign earnings and profits as of

December 31, 2017.

The Act also included provisions for the elimination of the Alternative Minimum Tax, among other changes. The Company calculated its best estimate of the impact of the Act in its

December 31, 2017

year end income tax provision in accordance with its understanding of the Act and guidance available and, as a result, recorded

$0.7

million as an additional income tax benefit in the

fourth

quarter of

2017,

the period in which the legislation was enacted. The provisional amount of

$0.7

million related to the reversal of AMT credits are now refundable credits under the provisions of the Act. The Company remeasured the deferred tax assets and liabilities based on the rate at which they were expected to reverse in the future.

provision or benefit was recorded as the Company had recorded a full valuation allowance against its deferred tax assets. The effects of other provisions of the Act did

not

have a material impact on the Company’s financial statements.

Uncertain Tax Positions

A reconciliation of the beginning and ending balances of the unrecognized tax benefits during the years ended

December

31,

2018,

2017

and

2016

is as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Unrecognized benefit—beginning of period	$	2,365	$	2,162	$	1,939
Gross increases—prior period tax positions		57		—		—
Gross increases—current period tax positions		213		203		223
Unrecognized benefit—end of period	$	2,635	$	2,365	$	2,162

The entire amount of the unrecognized tax benefits would

not

impact the Company’s effective tax rate if recognized.

There were

accrued interest or penalties related to unrecognized tax benefits in the years ended

December 31, 2018,

2017

and

2016.

The Company files income tax returns in the United States and in California. The tax years

2005

through

2018

remain open in both jurisdictions. The Company is

not

currently under examination by income tax authorities in federal, state or other foreign jurisdictions. The Company does

not

anticipate any significant changes within

months of this reporting date of its uncertain tax positions.

Note 18 - Subsequent Event	12 Months Ended
Note 18 - Subsequent Event	Dec. 31, 2018
Notes to Financial Statements
Subsequent Events [Text Block]	18. Subsequent Event On January 2, 2019, the Company entered into an agreement to sublease 12,106 square feet of the Expansion Space commencing on February 16, 2019 and expiring on January 31, 2024. Rent installments from the sublessee are approximately $48,000 per month (subject to agreed nominal increases).

Note 19 - Unaudited Quarterly Financial Data

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Quarterly Financial Information [Text Block]

. Unaudited Quarterly Financial Data

The following table sets forth certain unaudited quarterly financial data for the

eight

quarters ended

December

31,

2018.

The unaudited information set forth below has been prepared on the same basis as the audited information and includes all adjustments necessary to present fairly the information set forth herein. The operating results for any quarter are

not

indicative of results for any future period. All data is in thousands except per share data.

	201 8												2017
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	343		$	818		$	377		$	613		$	3,109		$	2,659		$	1,487		$	740
Operating costs and expenses	$	8,612		$	7,971		$	9,705		$	11,590		$	15,182		$	12,600		$	10,348		$	8,547
Net loss	$	(11,592	)	$	(10,541	)	$	(12,458	)	$	(12,558	)	$	(15,551	)	$	(13,059	)	$	(13,013	)	$	(9,885	)
Net loss per share (basic and diluted)	$	(0.23	)	$	(0.20	)	$	(0.21	)	$	(0.18	)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Business Description of Entity [Policy Text Block]

The Company

AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on

July 13, 2005

as SuRx, Inc., and in

January 2006,

the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company’s operations are based in Redwood City, California.

both focused on the treatment of acute pain, and each utilize sufentanil, delivered via a non-invasive route of sublingual administration, exclusively for use in medically supervised settings. On

November 2, 2018,

June 2018,

first

quarter of

2019.

In geographies where AcelRx decides

not

to commercialize products by itself, including for DZUVEO in Europe, the Company

may

seek to out-license commercialization rights. The Company currently intends to commercialize and promote DSUVIA/DZUVEO outside the United States with

one

or more strategic partners, although it has

not

DSUVIA

DSUVIA, known as DZUVEO in Europe, approved by the FDA in

November 2018,

June 2018.

not

Zalviso

Zalviso delivers

September 2013

but received a CRL on

July 25, 2014.

Subsequently, the FDA requested an additional clinical study,

IAP312,

designed to evaluate the effectiveness of changes made to the functionality and usability of the Zalviso device and to take into account comments from the FDA on the study protocol. In the

IAP312

study, for which top-line results were announced in

August 2017,

Zalviso met safety, satisfaction and device usability expectations. These results will supplement the

three

Phase

trials already completed in the Zalviso NDA resubmission. The Company is currently evaluating the timing of the NDA resubmission for Zalviso.

December 16, 2013,

AcelRx and Grünenthal entered into a Collaboration and License Agreement, or the License Agreement, which was amended effective

July 17, 2015

and

September 20, 2016,

September 2015,

the EC approved the MAA, previously submitted to the EMA, for Zalviso for the management of acute moderate-to-severe post-operative pain in adult patients. On

December 16, 2013,

July 22, 2015,

the Company and Grünenthal amended the MSA, or the Amended MSA, effective as of

July 17, 2015.

The Amended MSA and the Amended License Agreement are referred to as the Amended Agreements.

The Company has incurred recurring operating losses and negative cash flows from operating activities since inception. Although Zalviso has been approved for sale in Europe, on

September 18, 2015,

November 2018

and the Company began its commercial launch of DSUVIA in the

first

quarter of

2019.

As a result, the Company expects to continue to incur operating losses and negative cash flows until such time as DSUVIA has gained market acceptance and generated significant revenues.

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

Reclassification, Policy [Policy Text Block]

Reclassifications

December 31, 2017,

and the amount reported in the Consolidated Statements of Cash Flows as “Amortization of premium/discount on investments, net” has been reclassified to “Other” for the year ended

December 31, 2016.

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

The Consolidated Financial Statements include the accounts of the Company and its wholly owned subsidiary, ARPI LLC, which was formed in

September 2015

“Liability Related to Sale of Future Royalties” for additional information.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

not

readily apparent from other sources. Actual results could differ from those estimates.

Cash, Cash Equivalents, and Marketable Securities [Policy Text Block]

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investments with an original maturity (at date of purchase) of

three

months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks.

Fair Value Measurement, Policy [Policy Text Block]

Fair Value of Financial Instruments

three

-level valuation hierarchy for disclosure of fair value measurements as follows:

Level I—Unadjusted quoted prices in active markets for identical assets or liabilities;

Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are

not

active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level III—Unobservable inputs that are supported by little or

market activity for the related assets or liabilities.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Segment Reporting, Policy [Policy Text Block]

Segment Information

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Concentration of Risk

The Company invests cash that is currently

not

The Company relies on a single

third

-party supplier for the supply of sufentanil, the active pharmaceutical ingredient in DSUVIA and Zalviso, and various sole-source

third

-party contract manufacturer organizations to manufacture the DSUVIA SDA and Zalviso drug cartridge and device components, including the controller, the dispenser kit and the accessories.

To date, the Company has had only

two

customers. These

two

customers account for

100%

of the revenues for the years ended

December 31, 2018,

2017

and

2016.

One of these customers accounted for

100%

and

79%

of the accounts receivable balance as of

December 31, 2018,

and

2017,

respectively, while the other customer accounted for

71%

of the accounts receivable balance as of

December 31, 2016.

The Company has

not

experienced any losses with respect to the collection of its accounts receivable and believes that the entire accounts receivable balance as of

December 31, 2018

is collectible.

Receivables, Policy [Policy Text Block]

Accounts Receivable, Net

The Company has receivables from its collaboration partner and the U.S. Department of Defense, or DoD. To date, the Company has

not

Inventory, Policy [Policy Text Block]

Inventories

Inventories are valued at the lower of cost and net realizable value. Cost is determined using the

first

-in,

first

-out method for all inventories. Inventory includes the cost of the active pharmaceutical ingredients, or API, raw materials and

third

Property, Plant and Equipment, Policy [Policy Text Block]

Property and Equipment

three

five

years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term. Expenditures for repairs and maintenance, which do

not

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Impairment of Long-Lived Assets

not

may

determine that it is

September 30, 2015,

$0.5

million in the year ended

December 31, 2015,

which was recorded in interest income and other income, net in the Consolidated Statements of Comprehensive Loss. As of

December

31,

2018,

the Company has

not

written down any additional long-lived assets as a result of impairment.

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

Restricted Cash

Debt, Policy [Policy Text Block]

Debt Issuance Costs

Debt issuance costs, which are included in long-term debt, net of current portion, are amortized as interest expense over the contractual terms of the related credit facilities.

Contingent Put Option, Policy [Policy Text Block]

Contingent put option

“Long-Term Debt”.

Warrants, Policy [Policy Text Block]

Warrants

Warrants issued in connection with the Company’s Private Placement, completed in

June 2012,

are recorded as liabilities as they have the potential for cash settlement upon the occurrence of certain transactions (as defined in the warrant; see Note

“Warrants”). Changes in the fair value of the warrants are recognized as interest income and other income, net in the Consolidated Statements of Comprehensive Loss. As of

December 31, 2018,

all outstanding warrants of the Company had either been exercised or had expired.

Revenue Recognition, Policy [Policy Text Block]

Revenue Recognition

Beginning

January

2018,

the Company has followed the provisions of ASC Topic

606,

Revenue from Contracts with Customers

. The guidance provides a unified model to determine how revenue is recognized.

may

increase or decrease based on actual expenses incurred.

Performance Obligations

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic

606.

Transaction Price

not

occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price. Milestone payments that are

not

within the control of the Company, such as approvals from regulators, are

not

considered probable of being achieved until those approvals are received.

Allocation of Consideration

Timing of Recognition

may

Cost of Sales, Policy [Policy Text Block]

Cost of Goods Sold

not

realizable on a lower of cost or market basis. Cost of goods sold for Zalviso shipped to Grünenthal includes the inventory costs of API,

third

-party contract manufacturing costs, packaging and distribution costs, shipping, handling and storage costs, depreciation and costs of the employees involved with production.

Research and Development Expense, Policy [Policy Text Block]

Research and Development Expenses

Share-based Compensation, Option and Incentive Plans, Director Policy [Policy Text Block]

Stock-Based Compensation

Compensation expense for all share-based payment awards made to employees and directors, including employee stock options and restricted stock units related to the

2011

Equity Incentive Plan, or

2011

EIP, and employee share purchases related to the

2011

December 31, 2016,

was primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did

not

December 31, 2017,

December 31, 2016,

the Company estimated forfeitures at the time of grant and revised those estimates in subsequent periods if actual forfeitures differed from those estimates. Effective

January 1, 2017,

the Company adopted ASU

2016

and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

Interest Expense, Policy [Policy Text Block]

Non-Cash Interest Expense on Liability Related to Sale of Future Royalties

September 2015,

December 16, 2013,

as amended, to PDL for an upfront cash purchase price of

$65.0

$195.0

million, over the life of the arrangement. The aggregate future estimated royalty and milestone payments (subject to the capped amount), less the

$61.2

There are a number of factors that could materially affect the amount and timing of royalty payments from Zalviso in Europe, most of which are

not

within the Company’s control. Such factors include, but are

not

The Company will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the Royalty Monetization.

Comprehensive Income, Policy [Policy Text Block]

Comprehensive Loss

Income Tax, Policy [Policy Text Block]

Income Taxes

not.

Earnings Per Share, Policy [Policy Text Block]

Net Loss per Share of Common Stock

“Net Loss per Share of Common Stock”.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently

Adopted Accounting Pronouncement

May 2014,

the FASB issued ASU

No.

2014

09,

Revenue from Contracts with Customers (Topic

606

)

, to provide guidance on revenue recognition. In

August 2015

and

March,

April,

May

and

December 2016,

606,

606

is effective for interim and annual reporting periods beginning after

December 15, 2017,

with early adoption permitted

one

year earlier.

The Company adopted the new standard effective

January 1, 2018

under the modified retrospective transition method, applying the new guidance in the

first

quarter of

2018

to those contracts which were

not

completed as of

January 1, 2018.

For contracts which were modified before the adoption date, the Company has elected to treat the contracts and their modifications as combined contracts. Upon adoption, there was

change to the units of accounting previously identified under legacy GAAP, which are now considered performance obligations under the new guidance, and there was

change to the revenue recognition pattern for each performance obligation. Therefore, the adoption of the new standard resulted in

cumulative effect to the opening accumulated deficit balance.

May 2017,

the FASB issued ASU

2017

09,

Compensation - Stock Compensation (Topic

718

Scope of Modification Accounting

, to clarify which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under ASC

718.

Under the new guidance, an entity will

not

apply modification accounting to a share-based payment award if all of the following remain unchanged immediately before and after the change of terms and conditions:

●

The award’s fair value (or calculated value or intrinsic value, if those measurement methods are used),

●

The award’s vesting conditions, and

●

The award’s classification as an equity or liability instrument.

ASU

2017

is effective for annual periods, and interim periods within those annual periods, beginning after

December 15, 2017

for all entities. Early adoption is permitted, including adoption in any interim period for which financial statements have

not

yet been issued or made available for issuance. The ASU will be applied prospectively to awards modified on or after the adoption date. The adoption of ASU

2017

effective

January 1, 2018

did

not

have a material effect on the Company’s results of operations, financial condition or cash flows.

November 2016,

the FASB issued ASU

No.

2016

18,

Statement of Cash Flows (Topic

230

): Restricted Cash

. ASU

No.

2016

No.

2016

18,

and the guidance has been retrospectively applied to all periods presented. The adoption of the guidance did

not

have an impact on the Company’s consolidated balance sheets or statements of comprehensive loss.

August 2016,

the FASB issued ASU

No.

2016

15,

Statement of Cash Flows (Topic

230

): Classification of Certain Cash Receipts and Cash Payments,

addressing

eight

specific cash flow issues in an effort to reduce diversity in practice. The amended guidance is effective for fiscal years beginning after

December 15, 2017,

and for interim periods within those years. The adoption of ASU

2016

effective

January 1, 2018

did

not

have a material impact on the Company’s consolidated statements of cash flows.

Recently Issued

Accounting Pronouncements

February 2016,

the FASB issued ASU

No.

2016

02,

Leases (Topic

842

)

, which establishes a new lease accounting model for lessees. In

January,

July

and

December 2018,

the FASB issued additional amendments to the new lease guidance relating to, transition, and clarification. The

July 2018

amendment, ASU

No.

2018

11,

Leases (Topic

842

): Targeted Improvements

, provides an optional transition method that allows entities to elect to apply the standard prospectively at its effective date, versus recasting the prior periods presented. Pursuant to ASU

No.

2018

11,

December 15, 2018,

with early adoption permitted. The Company plans to adopt this standard on the effective date of

January 1, 2019.

The Company is substantially complete with its evaluation of the new standard as it relates to its operating lease disclosed in Note

may

contain embedded leases has been performed and the Company is evaluating the impact of its findings. However, it does

not

may

impact its current conclusions and will expand its analysis to include any new lease arrangements initiated prior to adoption.

Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	Year Ended December 31,
	2018		2017		2016
CASH AND CASH EQUIVALENTS		87,975		52,902		80,310
RESTRICTED CASH		178		178		178
CASH, CASH EQUIVALENTS AND RESTRICTED CASH SHOWN IN STATEMENT OF CASH FLOWS	$	88,153	$	53,080	$	80,488

Note 2 - Investments and Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Cash, Cash Equivalents and Investments [Table Text Block]

	As of December 31 , 201 8
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	2,037	$	—	$	—	$	2,037
Money market funds		1,436		—		—		1,436
U.S. government agency securities		10,181		—		—		10,181
Commercial paper		74,321		—		—		74,321
Total cash and cash equivalents		87,975		—		—		87,975

Short-term investments:
U.S. government agency securities	$	1,497	$	—	$	—	$	1,497
Commercial paper		16,243		—		—		16,243
Total marketable securities and commercial paper		17,740		—		—		17,740

Total cash, cash equivalents and investments	$	105,715	$	—	$	—	$	105,715

	As of December 31 , 201 7
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	29,765	$	—	$	—	$	29,765
U.S. government agency securities		23,137		—		—		23,137
Total cash and cash equivalents		52,902		—		—		52,902

Short-term investments:
U.S. government agency securities	$	7,567	$	—	$	—	$	7,567
Total marketable securities		7,567		—		—		7,567

Total cash, cash equivalents and investments	$	60,469	$	—	$	—	$	60,469

Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]

	As of December 31 , 201 8
	Fair Value		Level I		Level II		Level III
Assets
Money market funds	$	1,436	$	1,436	$	—	$	—
U.S. government agency securities		11,678		—		11,678		—
Commercial paper		90,564		—		90,564		—
Total assets measured at fair value	$	103,678	$	1,436	$	102,242	$	—

Liabilities
Contingent put option liability	$	121	$	—	$	—	$	121
Total liabilities measured at fair value	$	121	$	—	$	—	$	121

	As of December 31 , 201 7
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency securities	$	30,704	$	—	$	30,704	$	—
Total assets measured at fair value	$	30,704	$	—	$	30,704	$	—

Liabilities
Contingent put option liability	$	207	$	—	$	—	$	207
Total liabilities measured at fair value	$	207	$	—	$	—	$	207

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

	Year Ended December 31, 201 8
Fair value—beginning of period	$	207
Change in fair value of contingent put option associated with Amended Loan Agreement		(86	)
Fair value—end of period	$	121

	Year Ended December 31, 201 7
Fair value—beginning of period	$	412
Expiration of fair value of PIPE warrants		(288	)
Change in fair value of contingent put option associated with Amended Loan Agreement		83
Fair value—end of period	$	207

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Note 3 - Inventories (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Inventory, Current [Table Text Block]

	As of December 31,
	201 8		201 7
Raw materials	$	694	$	702
Work-in-process		160		254
Inventories	$	854	$	956

Note 4 - Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Property, Plant and Equipment [Table Text Block]

	As of December 31,
	201 8			201 7
Laboratory equipment	$	3,972		$	3,920
Leasehold improvements		4,469			4,469
Computer equipment and software		237			241
Construction in process		10,593			9,703
Tooling		1,109			1,109
Furniture and fixtures		47			47
		20,427			19,489
Less accumulated depreciation and amortization		(8,944	)		(8,438	)
Property and equipment, net	$	11,483		$	11,051

Note 5 - Adoption of ASC Topic 606, Revenue From Contracts With Customers (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Contract with Customer, Asset and Liability [Table Text Block]

	Balance at Beginning of the Period		Additions		Deductions			Balance at the end of the Period
	(in thousands)
Contract liability:
Deferred revenue	$	3,825	$	-	$	(362	)	$	3,463

Disaggregation of Revenue [Table Text Block]

	Year ended December 31 , 2018
Amounts included in contract liabilities at the beginning of the period:
Performance obligations satisfied – Amended Agreements	$	362
New activities in the period from performance obligations satisfied:
Performance obligations satisfied – Amended Agreements		566
Total revenue from performance obligations satisfied		928
Royalty revenue		385
Contract and other		838
Total revenue	$	2,151

Note 7 - Collaboration Agreement (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Revenue Recognition Amended Agreements [Table Text Block]

	Years Ended December 31,
	201 8		2017		201 6
Product sales	$	825	$	6,673	$	5,742
Joint steering committee, research and development services and demonstration devices		103		269		688
Non-cash royalty revenue related to Royalty Monetization (See Note 9)		289		151		7
Royalty revenue		96		50		3
Total	$	1,313	$	7,143	$	6,440

Note 8 - Long-term Debt (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Maturities of Long-term Debt [Table Text Block]

2019	$	9,437
2020		3,701

Total payments		13,138
Less amount representing interest		(872	)

Notes payable, gross		12,266
Unamortized portion of final payment		(229	)
Unamortized discount on notes payable		(46	)

Long-term debt		11,991
Less current portion of notes payable, including unamortized discount		(8,611	)

Long-term debt, current portion	$	3,380

Note 9 - Liability Related to Sale of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Other Liabilities [Table Text Block]

	Year ended December 31, 201 8			Period from inception to December 31, 201 8
Liability related to sale of future royalties — beginning balance	$	83,588		$	—
Proceeds from sale of future royalties		—			61,184
Non-cash royalty revenue		(250	)		(377	)
Non-cash interest expense recognized		10,341			32,872
Liability related to sale of future royalties as of December 31, 2018		93,679			93,679
Less: current portion		(392	)		(392	)
Liability related to sale of future royalties — net of current portion	$	93,287		$	93,287

Note 11 - Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Year Ending December 31:
2019	$	1,230
2020		1,268
2021		1,305
2022		1,345
2023		1,386
Thereafter		116
Total minimum payments	$	6,650

Note 13 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	December 31, 201 8		December 31, 201 7		December 31, 201 6
Cost of goods sold	$	358	$	324	$	302
Research and development		1,970		1,901		2,308
General and administrative		2,840		2,069		1,869
Total	$	5,168	$	4,294	$	4,479

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
								(in thousands)
December 31, 2017		8,455,098		$	4.25
Granted		3,553,713			2.28
Forfeited		(217,816	)		2.87
Expired		(232,905	)		6.36
Exercised		(135,385	)		2.96
December 31, 2018		11,422,705		$	3.64		7.1	$	659
Vested and exercisable options—December 31, 2018		6,468,788		$	4.44		5.8	$	46
Vested and expected to vest—December 31, 2018		11,422,705		$	3.64		7.1	$	659

Schedule of Share-based Compensation, Stock Options Outstanding and Exercisable Activity [Table Text Block]

			Options Outstanding						Options Vested and Exercisable
Exercise Prices			Number of Stock Options Outstanding		Weighted-Average Remaining Contractual Life (Years)		Weighted-Average Exercise Price per Share		Shares Subject to Stock Options		Weighted-Average Exercise Price per Share
$1.20	-	$2.00		1,856,170		9.0	$	2.00		6,900	$	1.20
$2.225	-	$3.35		5,406,951		7.8	$	2.82		2,698,203	$	2.82
$3.37	-	$5.31		2,855,022		5.2	$	4.13		2,459,123	$	4.19
$5.45	-	$8.18		688,562		5.0	$	6.47		688,562	$	6.47
$10.22	-	$10.55		616,000		5.1	$	10.34		616,000	$	10.34
				11,422,705		7.1	$	3.64		6,468,788	$	4.44

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	201 8			201 7			201 6
Expected term (in years)		5.89			5.70		5.25	-	6.25
Risk-free interest rate	2.5%	-	3.1%	1.82%	-	2.09%	1.24%	-	1.47%
Expected volatility		83%			73%			80%
Expected dividend rate		0%			0%			0%

Note 14 - Net Loss Per Share of Common Stock (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Year Ended December 31,
	201 8		201 7		201 6
ESPP and stock options to purchase common stock		11,797,960		8,767,783		6,395,879
Convertible debt into common stock		—		—		553,763
Common stock warrants		—		176,730		692,611

Note 15 - Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Accrued Liabilities [Table Text Block]

	December 31,
	201 8		201 7
Accrued compensation and employee benefits	$	3,611	$	2,190
Inventory and other contract manufacturing accruals		234		511
Other accrued liabilities		695		842
Total accrued liabilities	$	4,540	$	3,543

Note 17 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	December 31, 201 8		December 31, 201 7
Current:
Federal	$	—	$	(702	)
State		2		1
Total Current		2		(701	)
Deferred:
Federal		—		—
State		—		—
Total Deferred		—		—
Provision (benefit) for income taxes	$	2	$	(701	)

Schedule of Deferred Tax Assets [Table Text Block]

	December 31, 201 8			December 31, 201 7
Deferred tax assets:
Accruals and other	$	3,263		$	2,717
Research credits		7,275			6,530
Net operating loss carryforward		39,082			31,064
Section 59(e) R&D expenditures		10,387			12,156
Deferred revenue		20,689			18,384
Total deferred tax assets		80,696			70,851
Valuation allowance		(80,696	)		(70,851	)
Net deferred tax assets	$	—		$	—

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ended December 31,
	201 8			201 7			201 6
Tax at statutory federal rate	$	(9,901	)	$	(17,751	)	$	(14,685	)
State tax—net of federal benefit		(792	)		350			(73	)
PIPE warrant liability		(18	)		(70	)		(260	)
General business credits		(500	)		(316	)		(360	)
Stock options		1,048			42			1,115
Other		313			51			33
Change in valuation allowance		9,852			(17,110	)		14,196
Tax reform – tax rate change		—			34,103			—
Provision for income taxes	$	2		$	(701	)	$	(34	)

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	Year Ended December 31,
	2018		2017		2016
Unrecognized benefit—beginning of period	$	2,365	$	2,162	$	1,939
Gross increases—prior period tax positions		57		—		—
Gross increases—current period tax positions		213		203		223
Unrecognized benefit—end of period	$	2,635	$	2,365	$	2,162

Note 19 - Unaudited Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Quarterly Financial Information [Table Text Block]

	201 8												2017
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	343		$	818		$	377		$	613		$	3,109		$	2,659		$	1,487		$	740
Operating costs and expenses	$	8,612		$	7,971		$	9,705		$	11,590		$	15,182		$	12,600		$	10,348		$	8,547
Net loss	$	(11,592	)	$	(10,541	)	$	(12,458	)	$	(12,558	)	$	(15,551	)	$	(13,059	)	$	(13,013	)	$	(9,885	)
Net loss per share (basic and diluted)	$	(0.23	)	$	(0.20	)	$	(0.21	)	$	(0.18	)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)

Reconciliation of Cash, Cash Equivalents, and Restricted Cash - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 87,975	$ 52,902	$ 80,310
RESTRICTED CASH	178	178	178
CASH, CASH EQUIVALENTS AND RESTRICTED CASH SHOWN IN STATEMENT OF CASH FLOWS	$ 88,153	$ 53,080	$ 80,488	$ 108,100

Note 1 - Organization and Summary of Significant Accounting Policies (Details Textual) $ in Thousands		1 Months Ended	12 Months Ended				39 Months Ended
	Sep. 18, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015 USD ($)	Dec. 31, 2018 USD ($)
Proceeds From Sale of Royalty and Milestone Rights	$ 65,000	$ 65,000
Royalty Arrangment Maximum Payments	$ 195,000	195,000
Net Proceeds from Sale of Future Royalties		$ 61,200					$ 61,184
Interest Income [Member]
Asset Impairment Charges, Total			$ 0			$ 500
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Number of Major Customers			2	2	2
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Two Customers [Member]
Concentration Risk, Percentage			100.00%	100.00%	100.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| One Customer [Member]
Concentration Risk, Percentage			100.00%	79.00%	71.00%

Note 2 - Investments and Fair Value Measurement (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale Securities, Gross, Unrealized Gain (Loss) Accumulated In Investments	$ 0	$ 0
Available-for-sale Securities, Gross Realized Gain (Loss), Total	0	0
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Total	0	0
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	$ 0	$ 0

Note 2 - Investments and Fair Value Measurement - Summary of Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost	$ 105,715	$ 60,469
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	105,715	60,469
Cash and cash equivalents:
Amortized Cost	105,715	60,469
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	105,715	60,469
Cash and Cash Equivalents [Member]
Amortized Cost	87,975	52,902
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	87,975	52,902
Cash and cash equivalents:
Amortized Cost	87,975	52,902
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	87,975	52,902
Cash and Cash Equivalents [Member] \| Cash [Member]
Amortized Cost	2,037	29,765
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	2,037	29,765
Cash and cash equivalents:
Amortized Cost	2,037	29,765
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	2,037	29,765
Cash and Cash Equivalents [Member] \| Money Market Funds [Member]
Amortized Cost	1,436
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	1,436
Cash and cash equivalents:
Amortized Cost	1,436
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	1,436
Cash and Cash Equivalents [Member] \| U.S. Government Agency Securities [Member]
Amortized Cost	10,181	23,137
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	10,181	23,137
Cash and cash equivalents:
Amortized Cost	10,181	23,137
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	10,181	23,137
Cash and Cash Equivalents [Member] \| Commercial Paper [Member]
Amortized Cost	74,321
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	74,321
Cash and cash equivalents:
Amortized Cost	74,321
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	74,321
Marketable Securities [Member]
Amortized Cost	17,740	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	17,740	7,567
Cash and cash equivalents:
Amortized Cost	17,740	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	17,740	7,567
Marketable Securities [Member] \| U.S. Government Agency Securities [Member]
Amortized Cost	1,497	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	1,497	7,567
Cash and cash equivalents:
Amortized Cost	1,497	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	1,497	$ 7,567
Marketable Securities [Member] \| Commercial Paper [Member]
Amortized Cost	16,243
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	16,243
Cash and cash equivalents:
Amortized Cost	16,243
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	$ 16,243

Note 2 - Investments and Fair Value Measurement - Fair Value of Financial Assets and Liabilities by Level Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets, fair value	$ 103,678	$ 30,704
Liabilities, fair value	121	207
Contingent Put Option Liability [Member]
Liabilities, fair value	121	207
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	1,436
Liabilities, fair value
Fair Value, Inputs, Level 1 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	102,242	30,704
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 3 [Member]
Assets, fair value
Liabilities, fair value	121	207
Fair Value, Inputs, Level 3 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value	121	207
Money Market Funds [Member]
Assets, fair value	1,436
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets, fair value	1,436
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets, fair value
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets, fair value
U.S. Government Agency Obligations [Member]
Assets, fair value	11,678	30,704
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets, fair value
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets, fair value	11,678	30,704
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets, fair value
Commercial Paper [Member]
Assets, fair value	90,564
Commercial Paper [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets, fair value
Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets, fair value	90,564
Commercial Paper [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets, fair value

Note 2 - Investments and Fair Value Measurement - Summary of Changes in Fair Value of Level III Financial Liabilities (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair value, Beginning of period	$ 207	$ 412
Fair value, End of period	121	207
Expiration of fair value of PIPE warrants		(288)
Hercules 2011 Loan and Security Agreement [Member]
Change in fair value of contingent put option associated with Amended Loan Agreement	$ (86)	$ 83

Note 3 - Inventories (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventory Write-down		$ 369
ZALVISO [Member]
Inventory Write-down		$ 400

Note 3 - Inventories - Inventory Components (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Raw materials	$ 694	$ 702
Work-in-process	160	254
Inventories	$ 854	$ 956

Note 4 - Property and Equipment (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Depreciation, Total	$ 0.5	$ 1.7	$ 2.1

Note 4 - Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment, Gross	$ 20,427	$ 19,489
Less accumulated depreciation and amortization	(8,944)	(8,438)
Property and equipment, net	11,483	11,051
Laboratory Equipment [Member]
Property and Equipment, Gross	3,972	3,920
Leasehold Improvements [Member]
Property and Equipment, Gross	4,469	4,469
Computer Equipment and Software [Member]
Property and Equipment, Gross	237	241
Construction in Progress [Member]
Property and Equipment, Gross	10,593	9,703
Tooling [Member]
Property and Equipment, Gross	1,109	1,109
Furniture and Fixtures [Member]
Property and Equipment, Gross	$ 47	$ 47

Note 5 - Adoption of ASC Topic 606, Revenue From Contracts With Customers (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Discount on Manufacturing Services	$ 3.5

Note 5 - Adoption of ASC Topic 606, Revenue From Contracts With Customers - Changes in Contract Liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Contract Liabilities: Deferred Revenue	$ 3,825
Contract Liabilities: Deferred Revenue, Deductions	(362)
Contract Liabilities: Deferred Revenue	$ 3,463

Note 5 - Adoption of ASC Topic 606, Revenue From Contracts With Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amounts included in contract liabilities at the beginning of the period: Performance obligations satisfied – Amended Agreements									$ 362
New activities in the period from performance obligations satisfied: Performance obligations satisfied – Amended Agreements									566
Total revenue from performance obligations satisfied									928
Revenue	$ 613	$ 377	$ 818	$ 343	$ 740	$ 1,487	$ 2,659	$ 3,109	2,151	$ 7,995	$ 17,357
Royalty Revenue [Member]
Revenue									385
Contract and Other [Member]
Revenue									$ 838	$ 852	$ 10,917

Note 6 - U.S. Department of Defense Funding (Details Textual) - USD ($) $ in Thousands				12 Months Ended
	Feb. 28, 2018	Mar. 09, 2017	Mar. 02, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 11, 2015
Government Contract Receivable							$ 17,000
Revenue from Contract with Customer, Including Assessed Tax				$ 928
Amendment to DoD Contract Incorporate Additional Services [Member]
Government Contract Receivable	$ 500
Award Contract Renewal Term	1 year
Government [Member]
Award Contract Renewal Term		330 days	120 days
Government [Member] \| Contract and Other Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax				$ 800	$ 900	$ 10,900

Note 7 - Collaboration Agreement (Details Textual) - USD ($) $ in Thousands		1 Months Ended			3 Months Ended	15 Months Ended	19 Months Ended	60 Months Ended
	Jul. 17, 2015	Dec. 31, 2018	Sep. 30, 2015	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2015	Jul. 16, 2015	Dec. 15, 2018	Dec. 31, 2017
Payments in Exchange for Services Under Collaboration Agreement	$ 700
Amount of Binding Product Forecast Revenue	3,700
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	194,500
Manufacturing Agreement, Percentage for Five Years								100.00%
Manufacturing Agreement, Percentage, Thereafter		80.00%
Deferred Revenue, Current		$ 315							$ 362
Deferred Revenue, Noncurrent		3,148							$ 3,463
Amended License Agreement [Member]
Proceeds from Collaborators				$ 30,000
Amended License Agreement [Member] \| Europe [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total			$ 15,000		$ 5,000	$ 20,000
Amended License Agreement [Member] \| AUSTRALIA
Remaining Potential Milestone Payment		$ 1,000
Based upon Net Sales Target Achievements [Member]
Increase (Decrease) in Milestone Payments Related to Net Sales Target	5,500
Potential Milestone Payments Related to Net Sales Target	166,000						$ 171,500
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	166,000
Based upon Successful Regulatory and Product Development Efforts [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	$ 28,500

Note 7 - Collaboration Agreement - Summary of Revenue Recognized Under the Amended Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Non-cash royalty revenue related to Royalty Monetization (See Note 9)	$ 289	$ 151	$ 7
Total revenue from performance obligations satisfied	928
Collaborative Arrangement [Member]
Revenue Recognized	103	269	688
Non-cash royalty revenue related to Royalty Monetization (See Note 9)	289	151	7
Total	1,313	7,143	6,440
Collaborative Arrangement [Member] \| ZALVISO [Member] \| Grunenthal [Member]
Revenue Recognized	825	6,673	5,742
Collaborative Arrangement [Member] \| Royalty [Member]
Total revenue from performance obligations satisfied	$ 96	$ 50	$ 3

Note 8 - Long-term Debt (Details Textual) $ / shares in Units, $ in Thousands					1 Months Ended		6 Months Ended	12 Months Ended
	Mar. 02, 2017 USD ($)	Sep. 30, 2016 $ / shares shares	Sep. 18, 2015 $ / shares shares	Dec. 16, 2013 USD ($) $ / shares shares	Sep. 30, 2016 $ / shares	Dec. 31, 2013 $ / shares shares	Jun. 30, 2016 $ / shares	Mar. 01, 2020	Mar. 01, 2019	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 01, 2017 USD ($)	Sep. 17, 2015 $ / shares	Dec. 31, 2014 USD ($)	Sep. 24, 2014 USD ($)	Jun. 16, 2014 USD ($)
Repayments of Long-term Debt, Total										$ 7,718	$ 3,514
Fair Value of Contingent Put Option, Liability										121	207
Interest Expense, Total										2,217	3,316	$ 2,770
Hercules Warrants [Member]
Common Stock Warrants Exercised \| shares		176,730	176,730	176,730		176,730
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares		$ 3.07	$ 3.88	$ 6.79	$ 3.07	$ 9.67								$ 6.79
Investment Warrants, Exercise Price \| $ / shares					$ 3.07	$ 6.79	$ 3.88
Amended and Restated Loan and Security Agreement [Member]
Line of Credit Facility, Maximum Borrowing Capacity				$ 40,000
Number of Tranches for Loan and Security Agreement				3
Debt Instrument, Fair Value Disclosure, Total															$ 24,900
Long-term Debt Maturities Balloon Payments													$ 1,700
Debt Instrument, Variable Rate Threshold	9.55%
Debt Instrument, Percentage Used to Calculate Variable Rate	3.50%
Debt Instrument, Final Payment, Percentage of Aggregate Principal Amount	6.50%
Amended and Restated Loan and Security Agreement [Member] \| Prime Rate [Member]
Debt Instrument, Interest Rate, Effective Percentage												9.55%
Amended and Restated Loan and Security Agreement [Member] \| First Tranche [Member]
Debt Instrument, Face Amount				$ 15,000
Repayments of Long-term Debt, Total				8,600
Amended and Restated Loan and Security Agreement [Member] \| Second Tranche [Member]
Debt Instrument, Face Amount																	$ 10,000
Amended and Restated Loan and Security Agreement [Member] \| Third Tranche [Member]
Line of Credit Facility, Maximum Borrowing Capacity																$ 15,000
Hercules Loan and Security Agreement [Member]
Additional Default Interest Rate	5.00%
Fair Value of Contingent Put Option, Liability				$ 32						100	200
Long-term Line of Credit, Total										12,000	19,100
Interest Expense, Total										$ 2,200	$ 3,300	$ 2,800
Hercules Loan and Security Agreement [Member] \| Scenario, Forecast [Member]
Prepayment Charge of Term Loan Percentage								1.00%	2.00%
Hercules Loan and Security Agreement [Member] \| First Tranche [Member]
Debt Instrument, Face Amount	$ 20,500

Note 8 - Long-term Debt - Outstanding Future Payments of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
2019	$ 9,437
2020	3,701
Total payments	13,138
Less amount representing interest	(872)
Notes payable, gross	12,266
Unamortized portion of final payment	(229)
Unamortized discount on notes payable	(46)
Long-term debt	11,991
Less current portion of notes payable, including unamortized discount	(8,611)	$ (7,727)
Long-term debt, current portion	$ 3,380	$ 11,369

Note 9 - Liability Related to Sale of Future Royalties (Details Textual) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended				39 Months Ended
	Sep. 18, 2015	Sep. 30, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Proceeds From Sale of Royalty and Milestone Rights	$ 65,000	$ 65,000
Royalty Arrangment Maximum Payments	$ 195,000	$ 195,000
Effective Annual Interest Rate				11.60%	13.60%	13.70%	13.00%
ZALVISO [Member] \| Scenario, Forecast [Member]
Effective Annual Interest Rate			7.00%
First Four Commercial Milestones [Member]
Percentage of Royalties and Rights Under Agreement	20.00%
Royalties [Member]
Percentage of Royalties and Rights Under Agreement	25.00%
Remaining Commercial and All Development Milestone[Member]
Percentage of Royalties and Rights Under Agreement	100.00%
Commercial Milestones Value	$ 43,500
MAA Approval [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount	15,000
PDL [Member]
Proceeds From Sale of Royalty and Milestone Rights	$ 61,200
Percentage of Royalties and Rights Under Agreement	75.00%
PDL [Member] \| First Four Commercial Milestones [Member]
Percentage of Royalties and Rights Under Agreement	80.00%
Commercial Milestones Value Maximum Amount Available	$ 35,600
AcelRX [Member] \| First Four Commercial Milestones [Member]
Commercial Milestones Value Maximum Amount Available	$ 44,500

Note 9 - Liability Related to Sale of Future Royalties - Activity of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended			39 Months Ended
	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Liability related to sale of future royalties — beginning balance		$ 83,588
Proceeds from sale of future royalties	$ 61,200				61,184
Non-cash royalty revenue		(250)			(377)
Non-cash interest expense recognized		10,341	$ 10,721	$ 9,382	32,872
Liability related to sale of future royalties as of December 31, 2018		93,679	83,588		93,679
Less: current portion		(392)	(604)		(392)
Liability related to sale of future royalties — net of current portion		$ 93,287	$ 82,984		$ 93,287

Note 10 - Warrants (Details Textual) $ / shares in Units, $ in Thousands				1 Months Ended			6 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 18, 2015 $ / shares shares	Dec. 16, 2013 $ / shares shares	Sep. 30, 2016 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares $ / item shares	Jun. 30, 2012 USD ($) $ / shares shares	Jun. 30, 2016 $ / shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2018 shares	Sep. 30, 2015 USD ($)	Sep. 17, 2015 $ / shares
Hercules Warrants [Member]
Common Stock Warrants Exercised \| shares	176,730	176,730	176,730		176,730
Investment Warrants, Exercise Price \| $ / shares				$ 3.07	$ 6.79		$ 3.88
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares	$ 3.07	$ 3.88	$ 6.79	$ 3.07	$ 9.67							$ 6.79
Warrant Exercisable Term					5 years
Fair Value of Warrant On Date Of Issuance \| $	$ 45			$ 45	$ 1,100						$ 100
Derivative, Price Risk Option Strike Price \| $ / item					6.79
Class of Warrant or Right Fair Value Assumption Risk Free Interest Rate					1.55%
Class of Warrant or Right Fair Value Assumption Stock Volatility					71.00%
Class of Warrant or Right Fair Value Assumption Expected Dividend Yield					0.00%
Class of Warrant or Right, Outstanding \| shares										176,730
PIPE Warrants [Member]
Investment Warrants, Exercise Price \| $ / shares						$ 3.40
Warrant Exercisable Term						5 years
Class of Warrant or Right, Outstanding \| shares						2,630,103		512,456
Warrants Vesting Condition Description						50.00%
2012 Private Placement [Member]
Fair Value of Warrant Upon Execution of Securities Purchase Agreement \| $						$ 5,800
2012 Private Placement [Member] \| Nonoperating Income (Expense) [Member]
Fair Value Adjustment of Warrants \| $								$ (300)	$ (600)

Note 11 - Commitments and Contingencies (Details Textual)			1 Months Ended	12 Months Ended
	Jun. 14, 2017 USD ($) a	Oct. 02, 2015 ft² $ / item	May 31, 2014 ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Feb. 16, 2019 USD ($) ft²	Dec. 31, 2011 ft²
Rental Rate Per Square Foot \| $ / item		2.05
Sublease Income				$ 25,000	$ 300,000
Operating Leases, Rent Expense, Net, Total				$ 1,100,000	$ 600,000	$ 300,000
Redwood City, California [Member]
Area of Operating Lease \| ft²		11,871						13,787
Lessee, Operating Lease, Term of Contract		2 years 60 days
Lease Extended Term [Member]
Area of Operating Lease \| ft²			12,106
Lessee, Operating Lease, Renewal Term			1 year 261 days
Lease Agreement, Term			3 years 180 days
Executive Offices in Redwood City, CA [Member] \| Metropolitan Life Insurance Company [Member]
Lessee, Operating Lease, Renewal Term	6 years
Area of Real Estate Property \| a	25,893
Operating Lease, Annual Rent	$ 1,200,000
Lessee, Operating Lease, Term for Annual Rent Increase	1 year
Expansion Space Sublease [Member] \| Subsequent Event [Member]
Area of Operating Lease \| ft²							12,106
Operating Leases, Future Monthly Payments Due, Future Minimum Sublease Rentals							$ 48,000

Note 11 - Commitments and Contingencies - Future Minimum Payments Under Lease Agreement (Details) $ in Thousands	Dec. 31, 2018 USD ($)
2019	$ 1,230
2020	1,268
2021	1,305
2022	1,345
2023	1,386
Thereafter	116
Total minimum payments	$ 6,650

Note 12 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended				12 Months Ended
	Nov. 14, 2018	Nov. 14, 2018	Nov. 12, 2018	Aug. 07, 2018	Jul. 16, 2018	Jun. 21, 2016	Feb. 10, 2011	Aug. 07, 2018	Nov. 30, 2009	Feb. 29, 2008	Aug. 31, 2006	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2011
Proceeds from Issuance of Common Stock, Net												$ 81,525	$ 15,694
Employee Stock Purchase Plan, Shares Issued, Weighted Average Fair Value												$ 1.51	$ 2.59	$ 2.98
2006 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized											342,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized									1,400,000	375,000
2006 Equity Incentive Plan [Member] \| Minimum [Member]
Common Stock Voting Rights Percentage											10.00%
2006 Equity Incentive Plan [Member] \| Maximum [Member]
Fair Value of Common Stock as Percentage of Option Exercise Price											110.00%
2011 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized															1,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Outstanding							52,000								1,900,000
Stock Option Plan Option Reserve Annual Increase as Percentage of Outstanding Shares Allowed															4.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period															4 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant												1,217,341
2011 Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period															10 years
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized															250,000
Share-based Payment Award, Number of Shares Authorized															2.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans												858,889
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant												182,360
Public Offering [Member]
Proceeds from Issuance Initial Public Offering						$ 40,000
Underwritten Public Offering [Member]
Stock Issued During Period, Shares, New Issues	14,603,173	12,698,412	1,904,761	1,090,909	7,272,727			8,363,636
Shares Issued, Price Per Share	$ 3.15	$ 3.15	$ 3.15	$ 2.75	$ 2.75			$ 2.75
Proceeds from Issuance of Common Stock	$ 46,000							$ 23,000
Proceeds from Issuance of Common Stock, Net	$ 43,100							$ 21,700
ATM Agreement 2016 [Member]
Stock Issued During Period, Shares, New Issues												4,400,000	5,400,000
Proceeds from Issuance of Common Stock, Net												$ 16,800	$ 15,700
Payments of Stock Issuance Costs												$ 400	$ 500

Note 13 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 1.62	$ 1.91	$ 2.24
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total		$ 7,500
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition		2 years 146 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value		$ 4,900	$ 3,500	$ 3,900
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		$ 200	$ 40	$ 0
2011 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		1,217,341
2011 Equity Incentive Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	3,150,317

Note 13 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-based compensation expense	$ 5,168	$ 4,294	$ 4,479
Cost of Sales [Member]
Stock-based compensation expense	358	324	302
Research and Development Expense [Member]
Stock-based compensation expense	1,970	1,901	2,308
General and Administrative Expense [Member]
Stock-based compensation expense	$ 2,840	$ 2,069	$ 1,869

Note 13 - Stock-based Compensation - Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Outstanding (in shares) \| shares	8,455,098
Outstanding (in dollars per share) \| $ / shares	$ 4.25
Granted (in shares) \| shares	3,553,713
Granted, weighted-average exercise price (in dollars per share) \| $ / shares	$ 2.28
Forfeited (in shares) \| shares	(217,816)
Forfeited, weighted-average exercise price (in dollars per share) \| $ / shares	$ 2.87
Expired (in shares) \| shares	(232,905)
Expired, weighted-average exercise price (in dollars per share) \| $ / shares	$ 6.36
Exercised (in shares) \| shares	(135,385)
Exercised, weighted-average exercise price (in dollars per share) \| $ / shares	$ 2.96
Outstanding (in shares) \| shares	11,422,705
Outstanding, weighted-average exercise price (in dollars per share) \| $ / shares	$ 3.64
Outstanding, weighted-average remaining contractual life (Year)	7 years 36 days
Outstanding, aggregate intrinsic value \| $	$ 659
Vested and exercisable options (in shares) \| shares	6,468,788
Vested and exercisable options, weighted-average exercise price (in dollars per share) \| $ / shares	$ 4.44
Vested and exercisable options, weighted-average remaining contractual life (Year)	5 years 292 days
Vested and exercisable options, aggregate intrinsic value \| $	$ 46
Vested and expected to vest (in shares) \| shares	11,422,705
Vested and expected to vest, weighted-average exercise price (in dollars per share) \| $ / shares	$ 3.64
Vested and expected to vest, weighted-average remaining contractual life (Year)	7 years 36 days
Vested and expected to vest, aggregate intrinsic value \| $	$ 659

Note 13 - Stock-based Compensation - Stock Options Outstanding, Vested and Exercisable (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Stock Options Outstanding (in shares)	11,422,705	8,455,098
Weighted-average Remaining Contractual LIfe (Year)	7 years 36 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 3.64	$ 4.25
Shares Subject to Stock Options (in shares)	6,468,788
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 4.44
Exercise Price Range 1 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	1.20
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 2
Number of Stock Options Outstanding (in shares)	1,856,170
Weighted-average Remaining Contractual LIfe (Year)	9 years
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 2
Shares Subject to Stock Options (in shares)	6,900
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 1.20
Exercise Price Range 2 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	2.225
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 3.35
Number of Stock Options Outstanding (in shares)	5,406,951
Weighted-average Remaining Contractual LIfe (Year)	7 years 292 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 2.82
Shares Subject to Stock Options (in shares)	2,698,203
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 2.82
Exercise Price Range 3 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	3.37
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 5.31
Number of Stock Options Outstanding (in shares)	2,855,022
Weighted-average Remaining Contractual LIfe (Year)	5 years 73 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 4.13
Shares Subject to Stock Options (in shares)	2,459,123
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 4.19
Exercise Price Range 4 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	5.45
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 8.18
Number of Stock Options Outstanding (in shares)	688,562
Weighted-average Remaining Contractual LIfe (Year)	5 years
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 6.47
Shares Subject to Stock Options (in shares)	688,562
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 6.47
Exercise Price Range 5 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	10.22
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 10.55
Number of Stock Options Outstanding (in shares)	616,000
Weighted-average Remaining Contractual LIfe (Year)	5 years 36 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 10.34
Shares Subject to Stock Options (in shares)	616,000
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 10.34

Note 13 - Stock-based Compensation - Assumptions to Calculate Fair Value of Each Employee Stock Option (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Expected term (Year)	5 years 324 days	5 years 255 days
Expected volatility	83.00%	73.00%	80.00%
Expected dividend rate	0.00%	0.00%	0.00%
Minimum [Member]
Expected term (Year)			5 years 91 days
Risk-free interest rate	2.50%	1.82%	1.24%
Expected volatility
Expected dividend rate
Maximum [Member]
Expected term (Year)			6 years 91 days
Risk-free interest rate	3.10%	2.09%	1.47%
Expected volatility
Expected dividend rate

Note 14 - Net Loss Per Share of Common Stock - Common Stock Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ESPP and Employee Stock Options [Member]
Antidilutive securities (in shares)	11,797,960	8,767,783	6,395,879
Convertible Debt Securities [Member]
Antidilutive securities (in shares)			553,763
Warrant [Member]
Antidilutive securities (in shares)		176,730	692,611

Note 15 - Accrued Liabilities - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued compensation and employee benefits	$ 3,611	$ 2,190
Inventory and other contract manufacturing accruals	234	511
Other accrued liabilities	695	842
Total accrued liabilities	$ 4,540	$ 3,543

Note 16 - 401(k) Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan, Employer Discretionary Contribution Percentage	4.00%
Contributions by Employer to Postemployment Benefit Obligations	$ 0.3	$ 0.3	$ 0.3

Note 17 - Income Taxes (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
Note 17 - Income Taxes (Details Textual) - USD ($)	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Expense (Benefit), Total		$ 2,000	$ (701,000)	$ (34,000)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Period Increase (Decrease), Total		9,900,000	(17,100,000)	14,200,000
Income Taxes Receivable, Current		352,000
Income Taxes Receivable, Noncurrent	703,000	$ 351,000	$ 703,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	35.00%
Tax Adjustments, Settlements, and Unusual Provisions	(700,000)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	0	$ 0	$ 0	$ 0
Subject to Expiration [Member]
Operating Loss Carryforwards, Total		$ 1,400,000
Research Tax Credit Carryforward [Member] \| Subject to Expiration [Member]
Tax Credit Carryforward, Amount	26,000		26,000
Earliest Tax Year [Member]
Open Tax Year		2005
Latest Tax Year [Member]
Open Tax Year		2018
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	114,900,000	$ 153,200,000	114,900,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	700,000		700,000
Income Taxes Receivable, Current	400,000		400,000
Income Taxes Receivable, Noncurrent	300,000		300,000
Domestic Tax Authority [Member] \| Accounting Standards Update 2016-09 [Member]
Operating Loss Carryforwards, Total	2,900,000		2,900,000
Domestic Tax Authority [Member] \| Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount		6,500,000
Domestic Tax Authority [Member] \| Tax Year 2018 [Member]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Period Increase (Decrease), Total		38,300,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total		97,200,000
State and Local Jurisdiction [Member] \| Accounting Standards Update 2016-09 [Member]
Operating Loss Carryforwards, Total	$ 2,000,000		$ 2,000,000
State and Local Jurisdiction [Member] \| Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount		$ 4,000,000

Note 17 - Income Taxes - Provision (Benefit) for Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal		$ (702,000)
State	2,000	1,000
Total Current	2,000	(701,000)
Deferred:
Federal
State
Total Deferred
Provision (benefit) for income taxes	$ 2,000	$ (701,000)	$ (34,000)

Note 17 - Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accruals and other	$ 3,263	$ 2,717
Research credits	7,275	6,530
Net operating loss carryforward	39,082	31,064
Section 59(e) R&D expenditures	10,387	12,156
Deferred revenue	20,689	18,384
Total deferred tax assets	80,696	70,851
Valuation allowance	(80,696)	(70,851)
Net deferred tax assets		$ 0

Note 17 - Income Taxes - Reconciliation of Statutory Federal Income Tax (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax at statutory federal rate	$ (9,901,000)	$ (17,751,000)	$ (14,685,000)
State tax—net of federal benefit	(792,000)	350,000	(73,000)
PIPE warrant liability	(18,000)	(70,000)	(260,000)
General business credits	(500,000)	(316,000)	(360,000)
Stock options	1,048,000	42,000	1,115,000
Other	313,000	51,000	33,000
Change in valuation allowance	9,852,000	(17,110,000)	14,196,000
Tax reform – tax rate change		34,103,000
Provision (benefit) for income taxes	$ 2,000	$ (701,000)	$ (34,000)

Note 17 - Income Taxes - Reconciliation of Beginning and Ending Balance of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecognized benefit—beginning of period	$ 2,365	$ 2,162	$ 1,939
Gross increases—prior period tax positions	57
Gross increases—current period tax positions	213	203	223
Unrecognized benefit—end of period	$ 2,635	$ 2,365	$ 2,162

Note 18 - Subsequent Event (Details Textual) - Expansion Space Sublease [Member] - Subsequent Event [Member]	Feb. 16, 2019 USD ($) ft²
Area of Operating Lease \| ft²	12,106
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals \| $	$ 48,000

Note 19 - Unaudited Quarterly Financial Data - Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 613	$ 377	$ 818	$ 343	$ 740	$ 1,487	$ 2,659	$ 3,109	$ 2,151	$ 7,995	$ 17,357
Total operating costs and expenses	11,590	9,705	7,971	8,612	8,547	10,348	12,600	15,182	37,878	46,677	49,314
Net loss	$ (12,558)	$ (12,458)	$ (10,541)	$ (11,592)	$ (9,885)	$ (13,013)	$ (13,059)	$ (15,551)	$ (47,149)	$ (51,508)	$ (43,157)
Net loss per share of common stock, basic and diluted (in dollars per share)	$ (0.18)	$ (0.21)	$ (0.20)	$ (0.23)	$ (0.20)	$ (0.28)	$ (0.29)	$ (0.34)	$ (0.81)	$ (1.10)	$ (0.95)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details