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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Feb. 29, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	Evoke Pharma Inc
Entity Central Index Key	0001403708
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 13.2
Entity Common Stock, Shares Outstanding		24,431,914
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	EVOK
Security Exchange Name	NASDAQ
Entity File Number	001-36075
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8447886
Entity Address, Address Line One	420 Stevens Avenue
Entity Address, Address Line Two	Suite 370
Entity Address, City or Town	Solana Beach
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92075
City Area Code	858
Local Phone Number	345-1494
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A in connection with the registrant’s 2020 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such proxy statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the registrant’s fiscal year ended December 31, 2019.

Balance Sheets - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 5,663,833	$ 5,319,004
Prepaid expenses	581,706	329,218
Total current assets	6,245,539	5,648,222
Operating lease right-of-use asset	138,538
Other assets	11,551	11,551
Total assets	6,395,628	5,659,773
Current Liabilities:
Accounts payable and accrued expenses	1,033,383	476,202
Accrued compensation	843,162	1,158,251
Operating lease liability	138,538
Total current liabilities	2,015,083	1,634,453
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value; authorized shares — 5,000,000 at December 31, 2019 and 2018; issued and outstanding shares — 0 at December 31, 2019 and 2018
Common stock, $0.0001 par value; authorized shares — 50,000,000 at December 31, 2019 and 2018; issued and outstanding shares — 24,431,914 and 17,427,533 at December 31, 2019 and 2018, respectively	2,443	1,743
Additional paid-in capital	90,108,492	82,628,312
Accumulated deficit	(85,730,390)	(78,604,735)
Total stockholders' equity	4,380,545	4,025,320
Total liabilities and stockholders' equity	$ 6,395,628	$ 5,659,773

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	24,431,914	17,427,533
Common stock, shares outstanding	24,431,914	17,427,533

Statements of Operations - USD ($)	12 Months Ended
Statements of Operations - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 3,416,466	$ 4,095,014
General and administrative	3,737,987	3,919,671
Total operating expenses	7,154,453	8,014,685
Loss from operations	(7,154,453)	(8,014,685)
Other income:
Interest income	28,798	15,213
Gain from change in fair value of warrant liability		433,392
Total other income	28,798	448,605
Net loss	$ (7,125,655)	$ (7,566,080)
Net loss per share of common stock, basic and diluted	$ (0.32)	$ (0.46)
Weighted-average shares used to compute basic and diluted net loss per share	22,296,089	16,602,422

Statements of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2017	$ 2,165,749	$ 1,541	$ 73,202,863	$ (71,038,655)
Beginning Balance, Shares at Dec. 31, 2017		15,413,610
Stock-based compensation expense	1,539,469		1,539,469
Issuance of common stock from employee stock purchase plan	$ 47,057	$ 3	47,054
Issuance of common stock from employee stock purchase plan, Shares	28,869	28,869
Issuance of common stock, net	$ 4,571,240	$ 199	4,571,041
Issuance of common stock, shares net		1,985,054
Reclassification of warrant liability due to warrant amendment	3,267,885		3,267,885
Net loss	(7,566,080)			(7,566,080)
Ending Balance at Dec. 31, 2018	$ 4,025,320	$ 1,743	82,628,312	(78,604,735)
Ending Balance, Shares at Dec. 31, 2018	17,427,533	17,427,533
Stock-based compensation expense	$ 1,373,958		1,373,958
Issuance of common stock from employee stock purchase plan, Shares	0
Issuance of common stock, net	$ 6,106,922	$ 700	6,106,222
Issuance of common stock, shares net		7,004,381
Net loss	(7,125,655)			(7,125,655)
Ending Balance at Dec. 31, 2019	$ 4,380,545	$ 2,443	$ 90,108,492	$ (85,730,390)
Ending Balance, Shares at Dec. 31, 2019	24,431,914	24,431,914

- Definition

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

+ References + Details

Statements of Cash Flows - USD ($)	12 Months Ended
Statements of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net loss	$ (7,125,655)	$ (7,566,080)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,373,958	1,539,469
Change in fair value of warrant liability		(433,392)
Change in operating assets and liabilities:
Prepaid expenses and other assets	(116,676)	(78,172)
Accounts payable and accrued expenses	106,280	(440,385)
Net cash used in operating activities	(5,762,093)	(6,978,560)
Financing activities
Proceeds from issuance of common stock, net	6,106,922	4,618,297
Net cash provided by financing activities	6,106,922	4,618,297
Net increase (decrease) in cash and cash equivalents	344,829	(2,360,263)
Cash and cash equivalents at beginning of period	5,319,004	7,679,267
Cash and cash equivalents at end of period	$ 5,663,833	5,319,004
Non-cash financing activities
Reclassification of warrant liability to equity due to amendment of warrants		$ 3,267,885

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2019

Organization And Basis Of Presentation [Abstract]

Organization and Basis of Presentation

1. Organization and Basis of Presentation

Evoke Pharma, Inc. (the “Company”) was incorporated in the state of Delaware in January 2007. The Company is a specialty pharmaceutical company focused primarily on the development of drugs to treat gastroenterological disorders and disease.

Since its inception, the Company has devoted substantially all of its efforts to developing its sole product candidate, Gimoti™, and has not realized revenues from its planned principal operations. The Company filed a 505(b)(2) New Drug Application (“NDA”) for Gimoti with the U.S. Food and Drug Administration (“FDA”) on June 1, 2018, and on April 1, 2019, the Company received a Complete Response Letter (“CRL”) from FDA for the NDA. The CRL stated that FDA has determined it cannot approve the NDA in its present form and provided recommendations to address the two remaining approvability issues in an NDA resubmission. The approvability issues are related to clinical pharmacology and product quality/device quality. FDA did not request any new clinical data and did not raise any safety concerns.

On July 25, 2019, the Company completed a type A meeting with FDA to obtain FDA’s feedback and agreement on the Company’s plan to address deficiencies cited in the CRL in support of a resubmission of the Gimoti NDA. The focus of the discussion was on topics noted in the CRL, including the root cause analysis of low drug exposure in the comparative bioavailability study and additional product quality/device quality control testing.

On December 19, 2019, based on FDA feedback received during the type A meeting, the Company resubmitted the Gimoti NDA to FDA. The resubmission provided the requested additional information intended to address the deficiencies cited in the CRL. To address the clinical pharmacology issues, the resubmission included an in-depth root cause analysis, as well as patient use and experience data from the Company’s clinical trials. To address product quality/device quality issues cited in the CRL, the resubmission included 3-month stability data from commercial scale registration batches that met all product specifications. We believe these data support the acceptance criteria for performance characteristics and device quality control we proposed in the Gimoti NDA. Additionally, as requested by FDA, the resubmission included data from an analysis of pump performance characteristics for the product used in the comparative bioavailability study and the product from commercial scale registration batches. The results of this testing showed all products performed within specifications.

On January 17, 2020, the Company received a notice from FDA that it had accepted the Company’s NDA resubmission for review and set a target goal date for a decision under the Prescription Drug User Fee Act (“PDUFA”) of June 19, 2020.

The Company does not anticipate realizing revenues until FDA approves the NDA and the Company begins commercializing Gimoti, which events may never occur. The Company’s activities are subject to the significant risks and uncertainties associated with any specialty pharmaceutical company that has substantial expenditures for research and development, including funding its operations.

Going Concern

The Company has incurred recurring losses and negative cash flows from operations since inception and expects to continue to incur net losses for the foreseeable future until such time, if ever, that it can generate significant revenues from the sale of Gimoti. Although the Company ended 2019 with approximately $5.7 million in cash and cash equivalents, the Company anticipates that it will continue to incur losses from operations due to pre-approval and pre-commercialization activities, including interactions with FDA on the Company’s NDA submission for Gimoti, responding to approvability issues raised in the CRL received from FDA, and potentially manufacturing commercial batches of Gimoti, and for general and administrative costs to support operations. As a result, the Company believes that there is substantial doubt about its ability to continue as a going concern for one year after the date these financial statements are issued. The financial statements do not include any adjustments that may result from the outcome of this uncertainty.

The determination as to whether the Company can continue as a going concern contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. In its report on the Company’s financial statements for the year ended December 31, 2019, the Company’s independent registered public accounting firm included an explanatory paragraph expressing substantial doubt regarding the Company’s ability to continue as a going concern.

The Company’s net losses may fluctuate significantly from quarter to quarter and year to year. The Company believes, based on its current operating plan, that its existing cash and cash equivalents will be sufficient to fund its operations through the target goal date for a decision under PDUFA and into the third quarter of 2020. If Gimoti is approved by FDA, additional funds will become available from the revolving credit facility (the “Eversana Credit Facility”) with Eversana Life Sciences Services, LLC (“Eversana”), as disclosed in Note 8, which we believe, based on our current operating plan, will provide sufficient cash to fund the Company’s operations into 2021 excluding any potential future Gimoti product revenue. This period could be shortened if there are any significant increases in planned spending other than anticipated. Even with the Eversana Credit Facility, the Company will be required to raise additional funds through debt, equity or other forms of financing, such as potential collaboration arrangements, to fund future operations and continue as a going concern.

There can be no assurance that additional financing will be available when needed or on acceptable terms. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, and/or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations, financial condition and future prospects. There can be no assurance that the Company will be able to further develop Gimoti, if required, and receive FDA approval of the Gimoti NDA. Because the Company’s business is entirely dependent on the success of Gimoti, if the Company is unable to secure additional financing or identify and execute on other development or strategic alternatives for Gimoti or the company, the Company will be required to curtail all of its activities and may be required to liquidate, dissolve or otherwise wind down its operations.

Notice of Delisting

On May 15, 2019, the Company received a letter from Nasdaq indicating that, for the last thirty consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued listing on the Nasdaq Capital Market.

In accordance with Nasdaq listing rules, the Company was provided an initial period of 180 calendar days, or until November 11, 2019, to regain compliance. The Nasdaq letter had no immediate effect on the listing or trading of the Company’s common stock and the common stock continued to trade on the Nasdaq Capital Market.

The Company did not regain compliance with Nasdaq listing rules by November 11, 2019, but Nasdaq provided an additional 180 calendar day compliance period. On November 29, 2019, the Company received notification from Nasdaq that the Company regained compliance with the minimum bid price requirement for continued listing on the Nasdaq Capital Market.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ materially from those estimates.

Segment Reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment operating in the United States.

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents include cash in readily available checking and savings accounts.

Fair Value of Financial Instruments

The carrying amounts of all financial instruments, including accounts payable and accrued expenses, and employee-related liabilities, are considered to be representative of their respective fair values because of the short-term nature of those instruments.

Concentrations of Risk

Financial instruments that potentially subject the Company to significant credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in a federally insured financial institution in excess of federally insured limits. The Company has established guidelines designed to maintain safety and liquidity, has not experienced any losses in such accounts and believes the exposure to significant risk to the cash balance is minimal.

The Company relies on contract research organizations (“CROs”) and consultants to assist with ongoing regulatory discussions and submissions supporting the NDA. If the CROs and consultants are unable to continue their support, this could adversely affect FDA’s review of the NDA.

In addition, the Company relies on third-party manufacturers for the production of Gimoti. If the third-party manufacturers are unable to continue manufacturing Gimoti, or if the Company loses one of its sole source suppliers used in its manufacturing processes, the Company may not be able to meet any development needs or commercial supply demand for Gimoti, if approved by FDA, and the development and/or commercialization of Gimoti could be materially and adversely affected.

The Company also relies on third-party sales and marketing organizations for the management of the pre-commercial launch preparation for Gimoti, as well as for a dedicated sales team to sell Gimoti, if approved by FDA. If such third-party organizations are unable to continue managing the launch preparation, or serving as a dedicated sales team, the commercialization of Gimoti could be materially and adversely affected.

Warrant Accounting

In March 2018, the Company entered into warrant amendments (the “Warrant Amendments”) with each of the holders of the Company’s outstanding warrants to purchase common stock issued on July 25, 2016 and August 3, 2016 (the “Warrants”). As a result of the Warrant Amendments, the Warrants are no longer classified as a liability on the Company’s balance sheet, were adjusted to fair value as of the date of the Warrant Amendments, and were reclassified to additional paid-in capital, a component of stockholders’ equity.

Prior to the Warrant Amendments, the Warrants were classified as warrant liability and recorded at fair value. These Warrants contained a feature that could have required the transfer of cash in the event a change of control occurred without the authorization of the Company’s board of directors, and therefore, were classified as a liability in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 480, Distinguishing Liabilities from Equity.

This warrant liability was subject to remeasurement at each reporting date and the Company recognized any change in the fair value of the warrant liability in the statement of operations. The Company continued to adjust the carrying value of the warrants for changes in the estimated fair value until the date of the Warrant Amendments.

Stock-Based Compensation

Stock-based compensation expense for stock option grants and employee stock purchases under the Company’s Employee Stock Purchase Plan (the “ESPP”) is recorded at the estimated fair value of the award as of the grant date and is recognized as expense on a straight-line basis over the employee’s requisite service period. The estimation of stock option and ESPP fair value requires management to make estimates and judgments about, among other things, employee exercise behavior, forfeiture rates and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized.

The Company grants stock options to purchase common stock to employees and members of the board of directors with exercise prices equal to the Company’s closing market price on the date the stock options are granted. The risk-free interest rate assumption was based on the yield of an applicable rate for U.S. Treasury instruments with maturities similar to those of the expected term of the award being valued. The weighted average expected term of options and employee stock purchases was calculated using the simplified method as prescribed by accounting guidance for stock-based compensation. This decision was based on the lack of relevant historical data due to the Company’s limited historical experience. In addition, due to the Company’s limited historical data, the estimated volatility was calculated based upon the Company’s historical volatility, supplemented, as necessary, with historical volatility of comparable companies in the biotechnology industry whose share prices are publicly available for a sufficient period of time. The assumed dividend yield was based on the Company never paying cash dividends and having no expectation of paying cash dividends in the foreseeable future.

Research and Development Expenses

Research and development costs are expensed as incurred and primarily include compensation and related benefits, stock-based compensation expense and costs paid to third-party contractors for product development activities and drug product materials. The Company expenses costs relating to the purchase and production of pre-approval inventories as research and development expense in the period incurred until FDA approval is received.

Service providers typically invoice the Company monthly in arrears for services performed. In accruing service fees, the Company estimates the time period over which services were performed and the level of effort expended in each period. If the Company does not identify costs that have begun to be incurred, or if the Company underestimates or overestimates the level of services performed or the costs of these services, actual expenses could differ materially from estimates. To date, the Company has not experienced significant changes in estimates of accrued research and development expenses after a reporting period. However, due to the nature of estimates, no assurance can be made that changes to the estimates will not be made in the future as the Company becomes aware of additional information about the status or conduct of clinical studies and other research activities.

The Company does not own or operate manufacturing facilities for the production of Gimoti, nor does it plan to develop its own manufacturing operations in the foreseeable future. The Company currently depends on third-party contract manufacturers for all of its required raw materials, drug substance and finished product for its pre-commercial product development. The Company has agreements with Cosma S.p.A. to supply metoclopramide for the manufacture of Gimoti, and with Thermo Fisher Scientific Inc., who acquired Patheon UK Limited, for product development and manufacturing of Gimoti. The Company currently utilizes third-party consultants, which it engages on an as-needed, hourly basis, to manage product development and manufacturing contractors.

Income Taxes

The Company accounts for income taxes in accordance with ASC 740, Income Taxes. Under ASC 740, deferred tax assets and liabilities reflect the future tax consequences of the differences between the financial reporting and tax basis of assets and liabilities using current enacted tax rates. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax assets will be realized.

The Company’s policy related to accounting for uncertainty in income taxes prescribes a recognition threshold and measurement attributed criteria for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common stock outstanding for the period, without consideration for common stock equivalents and adjusted for the weighted-average number of common stock outstanding that are subject to repurchase. Since the Company’s repurchase right lapsed upon the filing of the NDA in June 2018, the Company no longer has any common stock subject to repurchase. As such, to account for the time the common stock was subject to repurchase, the Company excluded 18,791 shares from the weighted-average number of common stock outstanding for the year ended December 31, 2018. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of shares subject to repurchase, warrants to purchase common stock, options to purchase common stock under the Company’s equity incentive plans and potential shares to be purchased under the ESPP. For the periods presented, the following table sets forth the outstanding potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive:

	Year Ended December 31,
	2019		2018
Common stock subject to repurchase	—			18,791
Warrants to purchase common stock		2,713,561		2,713,561
Common stock options		3,114,371		3,017,624
Employee stock purchase plan		25,000		10,785
Total excluded securities		5,852,932		5,760,761

Recent Accounting Pronouncements

In February 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842). The new standard establishes a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. The Company adopted this standard effective January 1, 2019, as required. The Company determines if an arrangement is a finance lease, operating lease or short-term lease at inception. The Company elected the “package of practical expedients,” which permits the Company not to reassess prior conclusions about lease identifications, lease classification and initial direct costs. The Company also elected not to separate lease and non-lease components when certain conditions are met. As discussed in Note 3, the Company’s only significant lease is its facility lease, which expires on December 31, 2020, and is classified as an operating lease.

Commitments

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments

3. Commitments

In December 2016, the Company entered into an operating lease for office space in Solana Beach, California. The lease commenced on January 1, 2017, was extended in September 2018 and December 2019, and has an expiration date of December 31, 2020. According to ASU No. 2016-02, the Company recognized an operating lease ROU asset and liability based on the present value of the future minimum lease payments over the lease term at the commencement date, using the Company’s assumed incremental borrowing rate, and then amortizes the ROU assets over the lease term. The Company applies a discount rate to the minimum lease payments within the lease agreement to determine the value of right-of-use assets and lease liabilities. Unless the rate implicit in the lease is determinable, ASU No. 2016-02 requires the use of the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term for a similar amount to the lease payments in a similar economic environment. The Company noted that the implicit rate in the lease was not determinable and calculated its incremental borrowing rate primarily based on the Company’s assumed borrowing rate of 12%. On January 1, 2019, the Company recorded an operating lease ROU asset and liability of approximately $136,000 based on the present value of the remaining minimum lease payments. During the year ended December 31, 2019, changes in operating lease ROU asset and payments of the lease liability were included in prepaid expenses and other assets and accounts payable and other current liabilities, respectively, on the statement of cash flows.

Upon amendment and renewal of the term of the lease in December 2019, the Company updated the operating lease ROU asset and liability based on the present value of the future minimum lease payments over the lease term at the commencement date of the lease amendment and recorded an operating lease ROU asset and liability of approximately $139,000.

Rent expense for the years ended December 31, 2019 and 2018 was approximately $145,000 and $139,000, respectively. The Company also pays pass through costs and utility costs, which are expensed as incurred.

As of December 31, 2019, the Company has future minimum lease payments under its facility lease in 2020 of approximately $146,000.

Technology Acquisition Agreement

12 Months Ended

Dec. 31, 2019

Technology Acquisition Agreement [Abstract]

Technology Acquisition Agreement

4. Technology Acquisition Agreement

In June 2007, the Company acquired all worldwide rights, data, patents and other related assets associated with Gimoti from Questcor Pharmaceuticals, Inc. (“Questcor”) pursuant to an Asset Purchase Agreement. The Company paid Questcor $650,000 in the form of an upfront payment and $500,000 in May 2014 as a milestone payment based upon the initiation of the first patient dosing in the Company’s Phase 3 clinical trial for Gimoti. In August 2014, Mallinckrodt, plc (“Mallinckrodt”) acquired Questcor. As a result of that acquisition, Questcor transferred its rights included in the Asset Purchase Agreement with the Company to Mallinckrodt. In addition to the payments previously made to Questcor, the Company may also be required to make additional milestone payments totaling up to $52 million. In March 2018, the Company and Mallinckrodt amended the Asset Purchase Agreement to defer development and approval milestone payments, such that, rather than paying two milestone payments based on FDA acceptance for review of the NDA and final product marketing approval, the Company would be required to make a single $5 million payment on the one-year anniversary after the Company receives FDA approval to market Gimoti.

The remaining $47 million in milestone payments depend on Gimoti’s commercial success and will only apply if Gimoti receives regulatory approval. In addition, the Company will be required to pay Mallinckrodt a low single digit royalty on net sales of Gimoti. The Company’s obligation to pay such royalties will terminate upon the expiration of the last patent right covering Gimoti, which is expected to occur in 2032, subject to possible extension should any additional, later expiring, licensed patents be granted.

Preferred Stock, Common Stock and Stockholders' Equity

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Preferred Stock, Common Stock and Stockholders' Equity

5. Preferred Stock, Common Stock and Stockholders’ Equity

Preferred Stock

Under the Company’s amended and restated certificate of incorporation, the Company is authorized to issue 5,000,000 shares of preferred stock with a $0.0001 par value. No shares of preferred stock were outstanding as of December 31, 2019 or 2018.

Common Stock

As of December 31, 2019, there were 24,431,914 shares of common stock outstanding. Each share of common stock is entitled to one vote. The holders of the common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors of the Company. To date, no dividends have been declared.

As of December 31, 2019, the holders of 1,509,789 shares of the Company’s common stock are entitled to reasonable best efforts registration rights with respect to the registration of their shares under the Securities Act of 1933, as amended (“Securities Act.”). Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act, except for shares held by affiliates, as defined in Rule 144 under the Securities Act.

At the Market Equity Offering Program

In November 2017, the Company filed a shelf registration with the SEC on Form S-3. The shelf registration statement includes a prospectus for the at-the-market offering to sell up to an aggregate of $16.0 million of shares of the Company’s common stock through B. Riley FBR, Inc. (“FBR”) as a sales agent (the “FBR Sales Agreement”). During the year ended December 31, 2018, the Company sold 1,985,054 shares of common stock at a weighted-average price per share of $2.38 pursuant to the FBR Sales Agreement and received proceeds of approximately $4.6 million, net of commissions and fees. During the year ended December 31, 2019, the Company sold 7,004,381 shares of common stock at a weighted-average price per share of $0.89 pursuant to the FBR Sales Agreement and received proceeds of approximately $6.1 million, net of commissions and fees. From January 1, 2020 through February 29, 2020, the Company has not sold any shares of common stock pursuant to the FBR Sales Agreement.

Future sales will depend on a variety of factors including, but not limited to, market conditions, the trading price of the Company’s common stock and the Company’s capital needs. There can be no assurance that FBR will be successful in consummating future sales based on prevailing market conditions or in the quantities or at the prices that the Company deems appropriate.

In addition, the Company will not be able to make future sales of common stock pursuant to the FBR Sales Agreement unless certain conditions are met, which include the accuracy of representations and warranties made to FBR under the FBR Sales Agreement. Furthermore, FBR is permitted to terminate the FBR Sales Agreement in its sole discretion upon ten days’ notice, or at any time in certain circumstances, including the occurrence of an event that would be reasonably likely to have a material adverse effect on the Company’s assets, business, operations, earnings, properties, condition (financial or otherwise), prospects, stockholders’ equity or results of operations. The Company has no obligation to sell the remaining shares available for sale pursuant to the FBR Sales Agreement.

Warrants

The Company has issued warrants to purchase common stock to banks that have previously loaned funds to the Company, as well as to representatives of the underwriters of the Company’s public offerings and certain of their affiliates.

In March 2018, the Company entered into the Warrant Amendments with each of the holders of the Company’s outstanding Warrants acquired as a part of the Company’s financings which closed in July and August 2016. As a result of the Warrant Amendments, all of the remaining Warrants to purchase 2,449,129 shares of the Company’s common stock were no longer required to be classified as liabilities. The value of the amended Warrants was adjusted to the fair value immediately prior to the Warrant Amendments, resulting in a net gain of approximately $433,000 in the statement of operations for 2018, and approximately $3.3 million was reclassified from warrant liability to additional paid-in capital.

In September 2018, warrants to purchase 84,000 shares of the Company’s common stock, issued to representatives of the underwriters in connection with the Company’s initial public offering in September 2013, expired and have been cancelled.

At December 31, 2019 and 2018, there were warrants outstanding to purchase 2,713,561 shares of the Company’s common stock with a weighted average exercise price of $2.91. At December 31, 2019, the weighted average remaining contractual term of the outstanding warrants is 2.04 years.

Equity Incentive Award Plans

The Company adopted the 2007 Equity Incentive Plan (the “2007 Plan”) in May 2007 under which 450,000 shares of common stock were reserved for issuance to employees, nonemployee directors and consultants of the Company. There are no options available for future grant under this plan.

In August 2013, the Company adopted the 2013 Equity Incentive Award Plan (the “2013 Plan”) as a successor to the 2007 Plan. Under the 2013 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company. A total of 510,000 shares of common stock were initially reserved for issuance under the 2013 Plan. In addition, the number of shares of common stock available for issuance under the 2013 Plan will be annually increased on the first day of each fiscal year during the term of the 2013 Plan, beginning with the 2014 fiscal year, by an amount equal to the least of: (i) 300,000 shares; (ii) four percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.

In April 2016, the Company’s stockholders approved an amendment and restatement of the 2013 Equity Plan to increase the number of shares of common stock reserved under the 2013 Plan by 500,000 shares, to an aggregate of 4,786,425 shares, and to extend the term of the 2013 Plan into 2026.

In April 2018, the Company’s stockholders approved another amendment and restatement of the 2013 Plan (the “Restated Plan”) to increase the number of shares of common stock authorized for issuance under the 2013 Plan by 1,500,000 shares, to an aggregate of 6,286,425 shares, and to extend the term of the 2013 Plan to February 2028. In addition, beginning on January 1, 2019, the number of shares available for issuance will be annually increased on the first day of each fiscal year by that number of shares equal to the least of (a) four percent of the outstanding shares of common stock on the last day of the immediately preceding calendar year, and (b) such other amount determined by the Company’s board of directors. Notwithstanding the foregoing, the number of shares of common stock that may be issued or transferred pursuant to incentive stock options under the Restated Plan may not exceed an aggregate of 8,000,000 shares.

In June 2019, the Company effected a one-time option exchange, wherein employees were offered the opportunity to exchange certain outstanding stock options for the grant of a lesser number of replacement stock options. The participants received three new stock options for every four stock options tendered for exchange. As a result, 2,456,999 stock options were exchanged for 1,842,746 replacement stock options. The replacement stock options have a four-year vesting schedule and an exercise price of $0.62 per share, which was the closing price of the Company’s common stock on the date of the option exchange. All other terms of the replacement stock options remain the same as the original stock options that were exchanged. As a result of this transaction, the Company will recognize approximately $84,000 of additional stock-based compensation expense over the four-year vesting term of the exchanged options.

As a result of the annual increases since the 2013 Plan originated, and the increase of stock options reserved under the Restated Plan approved by the Company’s stockholders through April 2018, the Company has increased the number shares reserved for issuance under the 2013 Plan by 4,073,526 shares. As of December 31, 2019, 1,587,155 options remain available for future grant under the 2013 Plan. On January 1, 2020, the Company further increased the number of shares reserved for issuance under the 2013 Plan by 977,277 shares, making 2,564,432 options available for future grant under the 2013 Plan.

Options granted under the 2007 Plan and 2013 Plan have ten-year terms from the date of grant and generally vest over a one to four year period. The Company granted options to purchase 829,500 and 886,000 shares of common stock in 2019 and 2018, respectively. The exercise price of all options granted during the years ended December 31, 2019 and 2018 was equal to the market value per share of the Company’s common stock on the date of grant.

A summary of the Company’s stock option activity under the 2007 Plan and 2013 Plan is as follows:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding at December 31, 2018		3,017,624		$	3.11		7.68	$	382,160
Granted/Exchanged		2,672,246		$	1.20		9.36	—
Exercised	—			—		—		—
Expired/Forfeited/Exchanged		(2,575,499	)	$	2.82		7.48	—
Outstanding at December 31, 2019		3,114,371		$	1.71		8.32	$	2,143,756

Vested and expected to vest at December 31, 2019		3,114,371		$	1.71		8.32	$	2,143,756

Exercisable at December 31, 2019		1,230,605		$	3.17		6.70	$	392,604

The intrinsic values above represent the aggregate value of the total pre-tax intrinsic value based upon a common stock price of $1.62 and $2.48 at December 31, 2019 and 2018, respectively, and the contractual exercise price.

The weighted average grant date fair value per share of employee stock options granted during the years ended December 31, 2019 and 2018, was $0.91 and $1.86, respectively.

There were no options exercised in 2019 and 2018.

The Company had the following nonvested options under the 2007 Plan and 2013 Plan:

	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested at December 31, 2018		1,117,407		$	2.44
Granted		2,672,246		$	1.20
Vested		(494,674	)	$	1.53
Expired/Forfeited/Exchanged		(1,411,213	)	—
Nonvested at December 31, 2019		1,883,766		$	0.75

Employee Stock Purchase Plan

In June 2013, the Company’s board of directors adopted the ESPP, and the Company’s stockholders approved the ESPP on August 29, 2013. The ESPP became effective on the day prior to the effectiveness of the IPO. The ESPP permits participants to purchase the Company’s common stock at 85% of the fair market value through payroll deductions of up to 20% of their eligible compensation. A total of 30,000 shares of common stock were initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP has been annually increased on the first day of each fiscal year during the term of the ESPP by an amount equal to the lesser of: (i) 30,000 shares; (ii) one percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.

In May 2017, the Company’s stockholders approved an amendment and restatement of the Company’s ESPP to increase the number of shares of common stock reserved under the ESPP by 100,000 shares (to an aggregate of 1,250,000 shares), to increase the annual evergreen provision from 30,000 shares to 100,000 shares, and to extend the term of the ESPP into 2027. The Company increased the number shares reserved for issuance under the ESPP by 420,000 shares since the inception of the ESPP. As of December 31, 2019, 263,065 shares remain available for future issuance under the ESPP. On January 1, 2020, the Company further increased the number of shares reserved for future issuance under the ESPP by 100,000 shares, making 363,065 shares available for future issuance under the ESPP after that increase.

Payroll withholdings from the Company’s employees of approximately $47,000 resulted in the issuance of 28,869 shares of common stock through its ESPP during the year ended December 31, 2018. No shares of common stock were issued through the ESPP during 2019.

Stock-Based Compensation

Stock-based compensation expense includes charges related to employee stock purchases under the ESPP and stock option grants. The Company measures stock-based compensation expense based on the grant date fair value of any awards granted to its employees. Such expense is recognized over the period of time that employees provide service and earn rights to the awards.

The estimated fair value of each stock option award granted was determined on the date of grant using the Black Scholes option-pricing valuation model with the following weighted-average assumptions for option grants during the years ended December 31, 2019 and 2018:

	Year Ended December 31,
	2019	2018
Risk free interest rate	1.80% - 2.55%	2.66% - 2.85%
Expected option term	4.27 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	90.34% - 112.58%	90.15% - 92.30%
Expected dividend yield	0.0%	0.0%

The estimated fair value of the shares to be acquired under the ESPP was determined on the initiation date of each six-month purchase period using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for ESPP shares to be purchased during the years ended December 31, 2019 and 2018 as follows:

	Year Ended December 31,
	2019	2018
Risk free interest rate	1.89% - 2.52%	1.85% - 2.29%
Expected term	0.5 years	0.5 years
Expected volatility of common stock	130.36% - 170.68%	45.24% - 58.76%
Expected dividend yield	0.0%	0.0%

The Company recognized non-cash stock-based compensation expense to employees and directors in its research and development and its general and administrative functions during the years ended December 31, 2019 and 2018 as follows:

	Year Ended December 31,
	2019		2018
Research and development	$	710,155	$	673,525
General and administrative		663,803		865,944
Total stock-based compensation expense	$	1,373,958	$	1,539,469

As of December 31, 2019, there was approximately $2.1 million of unrecognized compensation costs related to outstanding employee and board of director options, which are expected to be recognized over a weighted-average period of 1.24 years.

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2019 and 2018:

	December 31,
	2019		2018
Stock options issued and outstanding		3,114,371		3,017,624
Authorized for future option grants		1,587,155		986,801
Warrants to purchase common stock		2,713,561		2,713,561
Authorized for employee stock purchase plan		263,065		163,065
Total common stock reserved for future issuance		7,678,152		6,881,051

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. Fair Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date.

As noted in Notes 2 and 5, due to the Warrant Amendments in March 2018, the warrant liability was reclassified to additional paid-in capital. Prior to the Warrant Amendments, the Company utilized a valuation hierarchy for disclosure of the inputs to the valuations used to measure fair value. This hierarchy prioritized the inputs into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on the Company’s own assumptions used to measure assets and liabilities at fair value. A financial asset or liability’s classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement.

The Company had no assets or liabilities classified as Level 1 or Level 2. The warrant liability, prior to the Warrant Amendments of the warrants, was classified as Level 3.

The following table presents a reconciliation of the Company’s warrant liability measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the year ended December 31, 2018:

	December 31,
	2018
Beginning balance of warrant liability	$	3,701,277
Change in fair value upon re-measurement		(433,392	)
Reclassification to Additional Paid-in Capital due to warrant exercise	—
Reclassification to Additional Paid-in Capital due to warrant amendment		(3,267,885	)
Ending balance of warrant liability	$	-

There were no transfers between Level 1 and Level 2 in any of the periods reported.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Employee Benefit Plan

12 Months Ended

Dec. 31, 2019

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plan

7. Employee Benefit Plan

The Company has established a defined contribution 401(k) plan (the “Plan”) for all employees who are at least 21 years of age. Employees are eligible to participate in the Plan beginning on the date of employment. Under the terms of the Plan, employees may make voluntary contributions as a percentage of compensation. The Company’s contributions to the Plan are discretionary, and no contributions have been made by the Company to date. For the years ended December 31, 2019 and 2018, the Company adopted Safe Harbor 401(k) provisions. No contributions were required to be made to the accounts of employees for the years ended December 31, 2019 and 2018 in order to maintain the Plan’s compliance with Internal Revenue Service regulations.

Commercial Services and Loan Agreements with Eversana

12 Months Ended

Dec. 31, 2019

Commercial Services And Loan Agreements [Abstract]

Commercial Services and Loan Agreements with Eversana

8. Commercial Services and Loan Agreements with Eversana

On January 21, 2020, the Company entered into a commercial services agreement (the “Eversana Agreement”) with Eversana for the commercialization of Gimoti. Pursuant to the Eversana Agreement, Eversana will commercialize and distribute Gimoti in the United States, if approved by FDA. Eversana will manage the marketing of Gimoti to gastroenterologists and other targeted health care providers, as well as the sales and distribution of Gimoti to wholesalers, pharmacies and other customers within the United States.

Under the terms of the Eversana Agreement, the Company maintains ownership of the Gimoti NDA, as well as legal, regulatory, and manufacturing responsibilities for Gimoti. Eversana will utilize its internal sales organization, along with other commercial functions, for market access, marketing, distribution and other related patient support services. The Company will record sales for Gimoti and retain more than 80% of net product profits once the parties’ costs are reimbursed. Eversana will receive reimbursement of its commercialization costs pursuant to an agreed upon budget and a percentage of product profits in the mid-to-high teens. Net product profits are the net sales (as defined in the Eversana Agreement) of Gimoti, less (i) reimbursed commercialization costs, (ii) manufacturing and administrative costs set at a fixed percentage of net sales, and (iii) third party royalties. During the term of the Eversana Agreement, Eversana agreed to not market, promote, or sell a competing product in the United States.

The term of the Eversana Agreement is from January 21, 2020 until five years from the date, if any, that FDA approves the Gimoti NDA. Upon expiration or termination of the agreement, the Company will retain all profits from product sales and assume all corresponding commercialization responsibilities. Within 30 days after each of the first three annual anniversaries of commercial launch, either party may terminate the agreement if net sales of Gimoti do not meet certain annual thresholds. Either party may terminate the agreement: for the material breach of the other party, subject to a 60-day cure period; in the event an insolvency, petition of the other party is pending for more than 60 days; upon 30 days written notice to the other party if Gimoti is subject to a safety recall; the other party is in breach of certain regulatory compliance representations under the agreement; the Company discontinues the development or production of Gimoti; Gimoti is not commercially launched within nine months of FDA approval, if any, or the net profit is negative for any two consecutive calendar quarters beginning with the first full calendar quarter 24 months following commercial launch; or if there is a change in applicable laws that makes operation of the services as contemplated under the agreement illegal or commercially impractical. Either party may also terminate the Eversana Agreement upon a change of control of the Company’s ownership, subject, in the event that the Company initiates such termination, to a one-time payment equal to between two times and one times annualized service fees paid by the Company under the Eversana Agreement, with such amount based on which year after commercial launch the change of control occurs. Such payment amount would be reduced by the amount of previously reimbursed commercialization costs and profit split paid for the related prior twelve month period and any revenue which occurred prior to the termination yet to be collected. In addition, Eversana may terminate the Eversana Agreement if Gimoti is not approved by FDA by December 31, 2020 (provided Eversana gives the Company notice of such termination no later than March 1, 2021), or if the Company withdraws Gimoti from the market for more than 90 days. The Company may also terminate the agreement if the parties are unable to agree to a commercialization plan and budget within 75 days of the date of the Eversana Agreement.

In addition, in connection with the Eversana Agreement, the Company and Eversana have entered into the Eversana Credit Facility, pursuant to which Eversana has agreed to provide a revolving Credit Facility of up to $5.0 million to the Company upon FDA approval of the Gimoti NDA, if any, as well as certain other customary conditions. The Eversana Credit Facility is secured by all of the Company’s personal property other than the Company’s intellectual property. Under the terms of the Eversana Credit Facility, the Company cannot grant an interest in the Company’s intellectual property to any other person. Each loan under the Eversana Credit Facility will bear interest at an annual rate equal to 10.0%.

The Company may prepay any amounts borrowed under the Eversana Credit Facility at any time without penalty or premium. The maturity date of all amounts, including interest, borrowed under the Eversana Credit Facility will be 90 days after the expiration or earlier termination of the Eversana Agreement. The Eversana Credit Facility also includes events of default, the occurrence and continuation of which provide Eversana with the right to exercise remedies against the Company and the collateral securing the loans under the Eversana Credit Facility, including the Company’s cash. These events of default include, among other things, the Company’s failure to pay any amounts due under the Eversana Credit Facility, an uncured material breach of the representations, warranties and other obligations under the Eversana Credit Facility, the occurrence of insolvency events and the occurrence of a change in control.

On January 23, 2020, the Company and Novos Growth, LLC mutually agreed to terminate, effective immediately, a commercialization agreement entered into in January 2019.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

9. Income Taxes

The Company accounts for uncertain tax positions in accordance with ASC Topic 740, Income Taxes. The application of income tax law and regulations is inherently complex. Interpretations and guidance surrounding income tax laws and regulations change over time. As such, changes in the Company’s subjective assumptions and judgments can materially affect amounts recognized in its financial statements.

The Company’s policy is to recognize interest and/or penalties related to income tax matters in income tax expense. The Company had no accrual for interest and penalties on the balance sheet at December 31, 2019. The Company has an uncertain tax position of $2.0 million related to California net operating losses at December 31, 2019. The Company is subject to taxation in the United States and state jurisdictions, and the Company’s tax years beginning 2007 to date are subject to examination by taxing authorities.

Deferred income taxes result from temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements that will result in taxable or deductible amounts in future years. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in years in which those temporary differences are expected to be recovered or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through income tax expense.

A reconciliation of the federal statutory income tax rate and the effective income tax rate is as follows for the years ended December 31, 2019 and 2018:

	December 31,
	2019			2018
	(%)			(%)
Federal statutory rate		21			21
Change in valuation allowance		(4	)		(1	)
State income taxes, net of federal effect		7		—
Warrant liability FMV adjustment	—				1
Research and development credits		3			4
Removal of net operating losses and other credits		(27	)		(22	)
Impact of state tax rate change		4		—
Stock compensation and other permanent items		(4	)		(3	)
Effective income tax rate	—			—

Pursuant to Internal Revenue Code (“IRC”) Sections 382 and 383, annual use of the Company’s net operating loss and research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has not completed an IRC Section 382/383 analysis regarding the limitation of net operating loss and research and development credit carryforwards. Until this analysis has been completed, the Company has removed the deferred tax assets for net operating losses of approximately $19.0 million and a research and development credit of approximately $3.5 million generated through December 31, 2019 from its deferred tax asset schedule, and has recorded a corresponding decrease to its valuation allowance. When this analysis is finalized, the Company plans to update its unrecognized tax benefits accordingly. The Company does not expect this analysis to be completed within the next twelve months and, as a result, the Company does not expect that the unrecognized tax benefits will change within twelve months of this reporting date. Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact the Company’s effective tax rate.

Significant components of the Company’s deferred tax assets at December 31, 2019 and 2018 are as follows:

	December 31,
	2019			2018
Deferred tax assets:
Acquired technology	$	80,000		$	81,000
Stock compensation expense		846,000			574,000
Lease liability		39,000		—
Accruals and other		237,000			244,000
Total deferred tax assets	$	1,202,000		$	899,000
Deferred tax liabilities:
Right of use asset		(39,000	)	—
Total deferred tax liabilities		(39,000	)	—
Less valuation allowance		(1,163,000	)		(899,000	)
Net deferred tax assets (liabilities)	—			—

At December 31, 2019, the Company has federal and California net operating loss carryforwards of approximately $74.5 million and $47.7 million, respectively. The federal and California net operating loss carryforwards begin to expire in 2027 and 2028, respectively, unless previously utilized. The portion of federal net operating losses created after 2017 of approximately $12.6 million do not expire and will carry forward indefinitely. The Company also has federal and California research tax credit carryforwards of approximately $2.3 million and $1.4 million, respectively. The federal research credit carryforwards will begin expiring in 2027 unless previously utilized. The California research credit will carry forward indefinitely. Furthermore, under U.S. tax legislation enacted in December 2017, although the treatment of tax losses generated before December 31, 2017 has generally not changed, tax losses generated in calendar year 2018 and beyond do not expire, but may only offset 80% of the Company’s taxable income. This change may require us to pay federal income taxes in future years despite generating a loss for federal income tax purposes in prior years.

There were no changes to unrecognized tax benefits in 2019 and 2018. As such, the balance of unrecognized tax benefits (excluding interest and penalties) was approximately $2.0 million at December 31, 2019 and 2018.

Due to the full valuation allowance that the Company has on the deferred tax assets, there are no unrecognized tax benefits that would impact the effective tax rate, if recognized.

Subsequent Events

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Events

10. Subsequent Events

For the purposes of the financial statements as of December 31, 2019 and the year then ended, the Company has evaluated subsequent events through the date the audited annual financial statements were issued. The Company has concluded that no subsequent event has occurred that required disclosure in the financial statements other than what has been disclosed.

Summarized Quarterly Data (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Data (Unaudited)

11. Summarized Quarterly Data (Unaudited)

The following financial information reflects all adjustments, which include only normal recurring adjustments, which are, in the opinion of management, necessary for a fair statement of the financial results of the interim periods. Summarized quarterly data for the years ended December 31, 2019 and 2018 are as follows:

	For the Quarters Ended
	March 31,			June 30,			September 30,			December 31,
2019
Research and development expense	$	746,882		$	1,205,599		$	822,444		$	641,541
General and administrative expense	$	1,223,013		$	918,139		$	814,218		$	782,617
Net loss	$	(1,965,266	)	$	(2,114,096	)	$	(1,628,065	)	$	(1,418,228	)
Net loss per common share, basic and diluted⁽¹⁾	$	(0.11	)	$	(0.09	)	$	(0.07	)	$	(0.06	)
Weighted average shares outstanding, basic and diluted		17,484,318			23,258,567			24,128,060			24,313,411

2018
Research and development expense	$	1,385,366		$	1,388,791		$	625,497		$	695,360
General and administrative expense	$	1,032,245		$	917,305		$	897,060		$	1,073,061
Gain from change in fair value of warrant liability	$	433,392		—			—			—
Net loss	$	(1,982,786	)	$	(2,303,193	)	$	(1,519,468	)	$	(1,760,633	)
Net loss per common share, basic and diluted⁽¹⁾	$	(0.13	)	$	(0.14	)	$	(0.09	)	$	(0.10	)
Weighted average shares outstanding, basic and diluted		15,427,037			16,425,468			17,129,649			17,427,533

(1)	Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly per-share calculations will not necessarily equal the annual per share calculation.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Use of Estimates

Segment Reporting

Cash and Cash Equivalents

Fair Value of Financial Instruments

Concentrations of Risk

Warrant Accounting

Stock-Based Compensation

Research and Development Expenses

Income Taxes

Net Loss Per Share

	Year Ended December 31,
	2019		2018
Common stock subject to repurchase	—			18,791
Warrants to purchase common stock		2,713,561		2,713,561
Common stock options		3,114,371		3,017,624
Employee stock purchase plan		25,000		10,785
Total excluded securities		5,852,932		5,760,761

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Outstanding Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

For the periods presented, the following table sets forth the outstanding potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive:

	Year Ended December 31,
	2019		2018
Common stock subject to repurchase	—			18,791
Warrants to purchase common stock		2,713,561		2,713,561
Common stock options		3,114,371		3,017,624
Employee stock purchase plan		25,000		10,785
Total excluded securities		5,852,932		5,760,761

Preferred Stock, Common Stock and Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Summary of Stock Option Activity

A summary of the Company’s stock option activity under the 2007 Plan and 2013 Plan is as follows:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding at December 31, 2018		3,017,624		$	3.11		7.68	$	382,160
Granted/Exchanged		2,672,246		$	1.20		9.36	—
Exercised	—			—		—		—
Expired/Forfeited/Exchanged		(2,575,499	)	$	2.82		7.48	—
Outstanding at December 31, 2019		3,114,371		$	1.71		8.32	$	2,143,756

Vested and expected to vest at December 31, 2019		3,114,371		$	1.71		8.32	$	2,143,756

Exercisable at December 31, 2019		1,230,605		$	3.17		6.70	$	392,604

Summary of Nonvested Options Activity

The Company had the following nonvested options under the 2007 Plan and 2013 Plan:

	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested at December 31, 2018		1,117,407		$	2.44
Granted		2,672,246		$	1.20
Vested		(494,674	)	$	1.53
Expired/Forfeited/Exchanged		(1,411,213	)	—
Nonvested at December 31, 2019		1,883,766		$	0.75

Summary of Estimated Fair Value of Stock Option Award

	Year Ended December 31,
	2019	2018
Risk free interest rate	1.80% - 2.55%	2.66% - 2.85%
Expected option term	4.27 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	90.34% - 112.58%	90.15% - 92.30%
Expected dividend yield	0.0%	0.0%

Summary of Estimated Fair Value of Shares to be Acquired under Employee Stock Purchase Plan

	Year Ended December 31,
	2019	2018
Risk free interest rate	1.89% - 2.52%	1.85% - 2.29%
Expected term	0.5 years	0.5 years
Expected volatility of common stock	130.36% - 170.68%	45.24% - 58.76%
Expected dividend yield	0.0%	0.0%

Summary of Recognized Non-Cash Stock-Based Compensation Expense

	Year Ended December 31,
	2019		2018
Research and development	$	710,155	$	673,525
General and administrative		663,803		865,944
Total stock-based compensation expense	$	1,373,958	$	1,539,469

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2019 and 2018:

	December 31,
	2019		2018
Stock options issued and outstanding		3,114,371		3,017,624
Authorized for future option grants		1,587,155		986,801
Warrants to purchase common stock		2,713,561		2,713,561
Authorized for employee stock purchase plan		263,065		163,065
Total common stock reserved for future issuance		7,678,152		6,881,051

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Reconciliation of Warrant Liability Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs

	December 31,
	2018
Beginning balance of warrant liability	$	3,701,277
Change in fair value upon re-measurement		(433,392	)
Reclassification to Additional Paid-in Capital due to warrant exercise	—
Reclassification to Additional Paid-in Capital due to warrant amendment		(3,267,885	)
Ending balance of warrant liability	$	-

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate

A reconciliation of the federal statutory income tax rate and the effective income tax rate is as follows for the years ended December 31, 2019 and 2018:

	December 31,
	2019			2018
	(%)			(%)
Federal statutory rate		21			21
Change in valuation allowance		(4	)		(1	)
State income taxes, net of federal effect		7		—
Warrant liability FMV adjustment	—				1
Research and development credits		3			4
Removal of net operating losses and other credits		(27	)		(22	)
Impact of state tax rate change		4		—
Stock compensation and other permanent items		(4	)		(3	)
Effective income tax rate	—			—

Summary of Significant Components of Deferred Tax Assets

Significant components of the Company’s deferred tax assets at December 31, 2019 and 2018 are as follows:

	December 31,
	2019			2018
Deferred tax assets:
Acquired technology	$	80,000		$	81,000
Stock compensation expense		846,000			574,000
Lease liability		39,000		—
Accruals and other		237,000			244,000
Total deferred tax assets	$	1,202,000		$	899,000
Deferred tax liabilities:
Right of use asset		(39,000	)	—
Total deferred tax liabilities		(39,000	)	—
Less valuation allowance		(1,163,000	)		(899,000	)
Net deferred tax assets (liabilities)	—			—

Summarized Quarterly Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Data

Summarized quarterly data for the years ended December 31, 2019 and 2018 are as follows:

	For the Quarters Ended
	March 31,			June 30,			September 30,			December 31,
2019
Research and development expense	$	746,882		$	1,205,599		$	822,444		$	641,541
General and administrative expense	$	1,223,013		$	918,139		$	814,218		$	782,617
Net loss	$	(1,965,266	)	$	(2,114,096	)	$	(1,628,065	)	$	(1,418,228	)
Net loss per common share, basic and diluted⁽¹⁾	$	(0.11	)	$	(0.09	)	$	(0.07	)	$	(0.06	)
Weighted average shares outstanding, basic and diluted		17,484,318			23,258,567			24,128,060			24,313,411

2018
Research and development expense	$	1,385,366		$	1,388,791		$	625,497		$	695,360
General and administrative expense	$	1,032,245		$	917,305		$	897,060		$	1,073,061
Gain from change in fair value of warrant liability	$	433,392		—			—			—
Net loss	$	(1,982,786	)	$	(2,303,193	)	$	(1,519,468	)	$	(1,760,633	)
Net loss per common share, basic and diluted⁽¹⁾	$	(0.13	)	$	(0.14	)	$	(0.09	)	$	(0.10	)
Weighted average shares outstanding, basic and diluted		15,427,037			16,425,468			17,129,649			17,427,533

(1)	Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly per-share calculations will not necessarily equal the annual per share calculation.

Organization and Basis of Presentation - Additional Information (Detail) - USD ($)		12 Months Ended
	May 15, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization And Basis Of Presentation [Abstract]
Month and year of incorporation		2007-01
Cash and cash equivalents		$ 5,663,833	$ 5,319,004	$ 7,679,267
Minimum common stock closing bid price	$ 1.00
Initial period to regain compliance	180 days
Closing bid price description		On May 15, 2019, the Company received a letter from Nasdaq indicating that, for the last thirty consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued listing on the Nasdaq Capital Market. In accordance with Nasdaq listing rules, the Company was provided an initial period of 180 calendar days, or until November 11, 2019, to regain compliance. The Nasdaq letter had no immediate effect on the listing or trading of the Company’s common stock and the common stock continued to trade on the Nasdaq Capital Market.

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 Segment	Dec. 31, 2018 shares
Accounting Policies [Abstract]
Number of operating segment \| Segment	1
Shares of common stock subject to repurchase excluded from the weighted-average number of common stock outstanding \| shares		18,791

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	5,852,932	5,760,761
Common stock subject to repurchase [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share		18,791
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	2,713,561	2,713,561
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	3,114,371	3,017,624
Employee stock purchase plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	25,000	10,785

Commitments - Additional Information (Detail) - USD ($)	12 Months Ended
Commitments - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Disclosure - Commitments - Additional Information (Detail) [Line Items]
Lease commencement date	Jan. 01, 2017
Lease expiry date	Dec. 31, 2020
Operating lease incremental borrowing rate	12.00%
Operating lease ROU	$ 138,538		$ 136,000
Operating lease liability	138,538		136,000
Rent expense	145,000	$ 139,000
Future minimum facility lease payments due in 2020	146,000
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease ROU	138,538		136,000
Operating lease liability	138,538		$ 136,000
Accounting Standards Update 2016-02
Disclosure - Commitments - Additional Information (Detail) [Line Items]
Operating lease ROU	139,000
Operating lease liability	139,000
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease ROU	139,000
Operating lease liability	$ 139,000

Technology Acquisition Agreement - Additional Information (Detail)	1 Months Ended		12 Months Ended
	May 31, 2014 USD ($)	Jun. 30, 2007 USD ($)	Dec. 31, 2019 USD ($) Milestone
Technology Acquisition Agreement [Line Items]
Payment expensed as in-process research and development		$ 650,000
Mallinckrodt Plc [Member]
Technology Acquisition Agreement [Line Items]
Milestone payments contingent amount			$ 5,000,000
Number of milestone payments \| Milestone			1
Mallinckrodt Plc [Member] \| Rights and Patents Acquired from Questcor Pharmaceuticals Inc [Member] \| Maximum [Member]
Technology Acquisition Agreement [Line Items]
Milestone payments contingent amount			$ 52,000,000
Development Target One [Member] \| Rights and Patents Acquired from Questcor Pharmaceuticals Inc [Member]
Technology Acquisition Agreement [Line Items]
Milestone payment	$ 500,000
Development targets description			Upon the initiation of the first patient dosing in the Company’s Phase 3 clinical trial for Gimoti
Development Target Four [Member] \| Mallinckrodt Plc [Member] \| Patented Technology [Member]
Technology Acquisition Agreement [Line Items]
Development targets description			Depend on Gimoti’s commercial success and will only apply if Gimoti receives regulatory approval. In addition, the Company will be required to pay Mallinckrodt a low single digit royalty on net sales of Gimoti
Milestone payments contingent amount			$ 47,000,000
Expected expiration of patent right			2032

Preferred Stock, Common Stock and Stockholders' Equity - Preferred Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares outstanding	0	0

Preferred Stock, Common Stock and Stockholders' Equity - Common Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Feb. 29, 2020	Dec. 31, 2017	Nov. 30, 2017
Sale Of Stock [Line Items]
Common stock, shares outstanding	24,431,914	17,427,533
Shareholders voting power description	Each share of common stock is entitled to one vote. The holders of the common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors of the Company.
Dividends declared on common stock	$ 0
Shares of common stock subject to Registration Rights	1,509,789
Common stock, shares issued	24,431,914	17,427,533
Proceeds from issuance of common stock, net	$ 6,106,922	$ 4,618,297
FBR Sales Agreement [Member]
Sale Of Stock [Line Items]
Common stock, shares issued	7,004,381	1,985,054		0
Common stock , weighted average price per share	$ 0.89	$ 2.38
Proceeds from issuance of common stock, net	$ 6,100,000	$ 4,600,000
FBR Sales Agreement [Member] \| Maximum [Member]
Sale Of Stock [Line Items]
Common stock, value of shares issuable					$ 16,000,000
FBR Sales Agreement [Member] \| Subsequent Event [Member]
Sale Of Stock [Line Items]
Common stock, shares issued			0

Preferred Stock, Common Stock and Stockholders' Equity - Warrants - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Sale Of Stock [Line Items]
Change in fair value of warrant liability		$ 433,392		$ 433,392
Warrants outstanding to purchase common stock			2,713,561	2,713,561
Weighted average exercise price of warrants			$ 2.91	$ 2.91
Weighted average remaining contractual term of outstanding warrants			2 years 14 days	2 years 14 days
Warrant Amendments [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock		2,449,129
Change in fair value of warrant liability		$ 433,000
Reclassification of warrant liability to Additional Paid-in Capital		$ 3,300,000
Amendment date		2018-03
Underwriters [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock expired	84,000

Preferred Stock, Common Stock and Stockholders' Equity - Equity Incentive Award Plans - Additional Information (Detail)			6 Months Ended	12 Months Ended
	Apr. 26, 2018 shares	Apr. 27, 2016 shares	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares	Jan. 01, 2020 shares	Aug. 31, 2013 shares	May 31, 2007 shares
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan	6,286,425			7,678,152	6,881,051
Award plan expiration month and year	2028-02
Stockholders' equity, stock split, conversion ratio			0.75
Stock options exchanged			2,456,999
Stock options issued			1,842,746
Exercise price \| $ / shares			$ 0.62
Share-based compensation expense \| $			$ 84,000
Share-based compensation arrangement, vesting period			4 years
Options available for future grant				1,587,155	986,801
Intrinsic value, common stock price \| $ / shares				$ 1.62	$ 2.48
Weighted Average Grant Date Fair Value Per Share, Granted \| $ / shares				$ 0.91	$ 1.86
Options Granted [Member]
Sale Of Stock [Line Items]
Options granted, weighted average term				10 years
Number of stock options granted				829,500	886,000
Options Granted [Member] \| Minimum [Member]
Sale Of Stock [Line Items]
Share-based compensation arrangement, vesting period				1 year
Options Granted [Member] \| Maximum [Member]
Sale Of Stock [Line Items]
Share-based compensation arrangement, vesting period				4 years
2007 Equity Incentive Plan [Member]
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan				0				450,000
2013 Equity Incentive Award Plan [Member]
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan							510,000
Shares available for issuance, description				In addition, the number of shares of common stock available for issuance under the 2013 Plan will be annually increased on the first day of each fiscal year during the term of the 2013 Plan, beginning with the 2014 fiscal year, by an amount equal to the least of: (i) 300,000 shares; (ii) four percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
Additional common stock reserved for issuance				4,073,526
Options available for future grant				1,587,155
2013 Equity Incentive Award Plan [Member] \| Subsequent Event [Member]
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan						977,277
Options available for future grant						2,564,432
2013 Equity Incentive Award Plan [Member] \| Annual Increase in Shares [Member]
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan				300,000
Reserve percentage for issuance of shares				4.00%
Amended and Restated Equity Incentive Plan 2013 [Member]
Sale Of Stock [Line Items]
Aggregate number of shares of common stock reserved under the plan	8,000,000	4,786,425
Shares available for issuance, description					In addition, beginning on January 1, 2019, the number of shares available for issuance will be annually increased on the first day of each fiscal year by that number of shares equal to the least of (a) four percent of the outstanding shares of common stock on the last day of the immediately preceding calendar year, and (b) such other amount determined by the Company’s board of directors. Notwithstanding the foregoing, the number of shares of common stock that may be issued or transferred pursuant to incentive stock options under the Restated Plan may not exceed an aggregate of 8,000,000 shares.
Increase in number of shares of common stock reserved under the plan	1,500,000	500,000
Award plan expiration year		2026
Amended and Restated Equity Incentive Plan 2013 [Member] \| Annual Increase in Shares [Member]
Sale Of Stock [Line Items]
Reserve percentage for issuance of shares				4.00%

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	3,017,624
Options, Outstanding ending balance	3,114,371	3,017,624
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding beginning balance	3,017,624
Options, Granted/Exchanged	2,672,246
Options, Expired/Forfeited/Exchanged	(2,575,499)
Options, Outstanding ending balance	3,114,371	3,017,624
Options, Vested and expected to vest at December 31, 2019	3,114,371
Options, Exercisable at December 31, 2019	1,230,605
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding beginning balance	$ 3.11
Weighted Average Exercise Price, Granted/Exchanged	1.20
Weighted Average Exercise Price, Expired/Forfeited/Exchanged	2.82
Weighted Average Exercise Price, Outstanding ending balance	1.71	$ 3.11
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2019	1.71
Weighted Average Exercise Price, Exercisable at December 31, 2019	$ 3.17
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Remaining Contractual Term [Abstract]
Weighted Average Remaining Contractual Term (Years), Outstanding	8 years 3 months 26 days	7 years 8 months 5 days
Weighted Average Remaining Contractual Term (Years), Granted/Exchanged	9 years 4 months 9 days
Weighted Average Remaining Contractual Term (Years), Expired/Forfeited/Exchanged	7 years 5 months 23 days
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest at December 31, 2019	8 years 3 months 26 days
Weighted Average Remaining Contractual Term (Years), Exercisable at December 31, 2019	6 years 8 months 12 days
Share Based Compensation Arrangement by Share Based Payment Award Options Outstanding, Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value, Outstanding beginning balance	$ 382,160
Aggregate Intrinsic Value, Outstanding ending balance	2,143,756	$ 382,160
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2019	2,143,756
Aggregate Intrinsic Value, Exercisable at December 31, 2019	$ 392,604

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Nonvested Options Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Per Share, Granted	$ 0.91	$ 1.86
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Options Nonvested, Outstanding beginning balance	1,117,407
Options, Granted	2,672,246
Options Vested	(494,674)
Options, Expired/Forfeited/Exchanged	(1,411,213)
Options Nonvested, Outstanding ending balance	1,883,766	1,117,407
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Per Share, Nonvested beginning balance	$ 2.44
Weighted Average Grant Date Fair Value Per Share, Granted	1.20
Weighted Average Grant Date Fair Value Per Share, Vested	1.53
Weighted Average Grant Date Fair Value Per Share, Nonvested ending balance	$ 0.75	$ 2.44

Preferred Stock, Common Stock and Stockholders' Equity - Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended
	Jan. 01, 2020	May 31, 2017	Jun. 30, 2013	Dec. 31, 2019	Dec. 31, 2018	Apr. 26, 2018	Apr. 30, 2017
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs				$ 2,100,000
Weighted average period				1 year 2 months 26 days
Aggregate number of shares of common stock reserved under the plan				7,678,152	6,881,051	6,286,425
Shares of common stock available for future issuance under ESPP				263,065	163,065
Stock issued during period, shares, period increase					420,000
Issuance of common stock under employee stock purchase plan				0	28,869
Payroll withholdings from employees					$ 47,000
Amended and Restated ESPP [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares of common stock reserved under the plan		1,250,000
Increase in number of shares of common stock reserved under the plan		100,000
Number of shares increased annually to common stock shares reserved for issuance		100,000					30,000
Award plan expiration year		2027
Employee stock purchase plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock as percentage of fair market value			85.00%
Percentage of deduction of eligible compensation			20.00%
Aggregate number of shares of common stock reserved under the plan			30,000
Shares available for issuance, description				In addition, the number of shares of common stock available for issuance under the ESPP has been annually increased on the first day of each fiscal year during the term of the ESPP by an amount equal to the lesser of: (i) 30,000 shares; (ii) one percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
Reserve percentage for issuance of shares			1.00%
ESPP approval date			Aug. 29, 2013
Subsequent Event [Member] \| Employee stock purchase plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares of common stock reserved under the plan	363,065
Stock issued during period, shares, period increase	100,000

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Estimated Fair Value of Stock Option Award (Detail) - Common stock options [Member]	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.80%	2.66%
Expected option term	4 years 3 months 7 days	5 years 6 months
Expected volatility of common stock	90.34%	90.15%
Maximum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.55%	2.85%
Expected option term	6 years	6 years
Expected volatility of common stock	112.58%	92.30%

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Estimated Fair Value of Employee Stock Purchase Plan Award (Detail) - Employee stock purchase plan [Member]	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 months	6 months
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.89%	1.85%
Expected volatility of common stock	130.36%	45.24%
Maximum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.52%	2.29%
Expected volatility of common stock	170.68%	58.76%

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Recognized Non-Cash Stock-Based Compensation Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,373,958	$ 1,539,469
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	710,155	673,525
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 663,803	$ 865,944

Preferred Stock, Common Stock and Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2019	Dec. 31, 2018	Apr. 26, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options issued and outstanding	3,114,371	3,017,624
Authorized for future option grants	1,587,155	986,801
Warrants to purchase common stock	2,713,561	2,713,561
Authorized for employee stock purchase plan	263,065	163,065
Total common stock reserved for future issuance	7,678,152	6,881,051	6,286,425

Fair Value Measurements - Additional Information (Detail)	Dec. 31, 2019 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers of assets out of Level 1 into Level 2	$ 0
Transfers of assets out of Level 2 into Level 1	0
Transfers of liabilities out of Level 1 into Level 2	0
Transfers of liabilities out of Level 2 into Level 1	0
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	0
Liabilities	0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	0
Liabilities	$ 0

Fair Value Measurements - Summary of Reconciliation of Warrant Liability Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Detail) - Fair Value Measurement, Recurring [Member] - Warrant Liability [Member]	12 Months Ended
	Dec. 31, 2018 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 3,701,277
Change in fair value upon re-measurement	(433,392)
Reclassification to Additional Paid-in Capital due to warrant amendment	$ (3,267,885)

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Postemployment Benefits [Abstract]
Eligible age for employees for participating in the plan	21 years
Company's contributions to employee benefit plan	$ 0	$ 0

Commercial Services and Loan Agreements with Eversana - Additional Information (Detail) - Eversana Agreement [Member]	Jan. 21, 2020 USD ($)
Commercial Services And Loan Agreements [Line Items]
Term of agreement	5 years
Agreement termination fee description	The Company may also terminate the agreement if the parties are unable to agree to a commercialization plan and budget within 75 days of the date of the Eversana Agreement.
Subsequent Event [Member] \| Revolving Credit Facility [Member]
Commercial Services And Loan Agreements [Line Items]
Line of credit	$ 5,000,000
Line of credit facility, Interest rate	10.00%
Gimoti [Member] \| Minimum [Member] \| Subsequent Event [Member]
Commercial Services And Loan Agreements [Line Items]
Percentage Of Product Profits	80.00%

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Accrual on interest and penalties related to income taxes	$ 0
Uncertain tax position	2,000,000	$ 2,000,000
Removal of net operating losses from deferred tax assets	$ 19,000,000
Cumulative change in ownership for limitation of use of net operating loss and research and development credit carryforwards	50.00%
Period of cumulative change of ownership	3 years
Removal of research and development credit from deferred tax assets	$ 3,500,000
Percentage of taxable income offset by tax losses	80.00%
Changes to unrecognized tax benefits	$ 0	$ 0
Unrecognized tax benefits that would affect company's effective tax rate, if recognized	$ 0
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax years subject to examination by taxing authorities	2007
California [Member]
Operating Loss Carryforwards [Line Items]
Uncertain tax position	$ 2,000,000
Net operating loss carry forwards	$ 47,700,000
Expiry date of carry forwards	Dec. 31, 2028
California [Member] \| Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forwards	$ 1,400,000
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	$ 74,500,000
Expiry date of carry forwards	Dec. 31, 2027
Net operating loss carryforwards, not subject to expiration	$ 12,600,000
Federal [Member] \| Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carry forwards	$ 2,300,000

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%
Change in valuation allowance	(4.00%)	(1.00%)
State income taxes, net of federal effect	7.00%
Warrant liability FMV adjustment		1.00%
Research and development credits	3.00%	4.00%
Removal of net operating losses and other credits	(27.00%)	(22.00%)
Impact of state tax rate change	4.00%
Stock compensation and other permanent items	(4.00%)	(3.00%)

Income Taxes - Summary of Significant Components of Deferred Tax Assets (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Acquired technology	$ 80,000	$ 81,000
Stock compensation expense	846,000	574,000
Lease liability	39,000
Accruals and other	237,000	244,000
Total deferred tax assets	1,202,000	899,000
Deferred tax liabilities:
Right of use asset	(39,000)
Total deferred tax liabilities	(39,000)
Less valuation allowance	$ (1,163,000)	$ (899,000)

Summarized Quarterly Data (Unaudited) - Summarized Quarterly Data (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Research and development expense	$ 641,541	$ 822,444	$ 1,205,599	$ 746,882	$ 695,360	$ 625,497	$ 1,388,791	$ 1,385,366	$ 3,416,466	$ 4,095,014
General and administrative expense	782,617	814,218	918,139	1,223,013	1,073,061	897,060	917,305	1,032,245	3,737,987	3,919,671
Gain from change in fair value of warrant liability								433,392		433,392
Net loss	$ (1,418,228)	$ (1,628,065)	$ (2,114,096)	$ (1,965,266)	$ (1,760,633)	$ (1,519,468)	$ (2,303,193)	$ (1,982,786)	$ (7,125,655)	$ (7,566,080)
Net loss per share of common stock, basic and diluted	$ (0.06)	$ (0.07)	$ (0.09)	$ (0.11)	$ (0.10)	$ (0.09)	$ (0.14)	$ (0.13)	$ (0.32)	$ (0.46)
Weighted average shares outstanding, basic and diluted	24,313,411	24,128,060	23,258,567	17,484,318	17,427,533	17,129,649	16,425,468	15,427,037	22,296,089	16,602,422

- Definition

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

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