View Filing Data

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2017	May 05, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Trading Symbol	EVOK
Entity Registrant Name	Evoke Pharma Inc
Entity Central Index Key	0001403708
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		15,388,325

Condensed Balance Sheets (Unaudited) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 14,654,998	$ 9,007,071
Prepaid expenses	171,524	267,711
Other current assets		7,997
Total current assets	14,826,522	9,282,779
Other assets	11,551	11,551
Total assets	14,838,073	9,294,330
Current Liabilities:
Accounts payable and accrued expenses	549,039	478,223
Accrued compensation	586,772	933,450
Total current liabilities	1,135,811	1,411,673
Warrant liability	5,768,675	4,095,019
Total liabilities	6,904,486	5,506,692
Stockholders' equity:
Common stock, $0.0001 par value; authorized shares - 50,000,000; issued and outstanding shares - 15,388,325 and 12,350,360 at March 31, 2017 and December 31, 2016, respectively	1,539	1,235
Additional paid-in capital	71,793,230	62,595,546
Accumulated deficit	(63,861,182)	(58,809,143)
Total stockholders' equity	7,933,587	3,787,638
Total liabilities and stockholders' equity	$ 14,838,073	$ 9,294,330

Condensed Statements of Operations (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating expenses:
Research and development	$ 770,686	$ 2,015,076
General and administrative	1,209,570	1,137,753
Total operating expenses	1,980,256	3,152,829
Loss from operations	(1,980,256)	(3,152,829)
Other expenses:
Interest income (expense), net	964	(72,580)
Change in fair value of warrant liability	(3,072,747)
Total other expenses	(3,071,783)	(72,580)
Net loss	$ (5,052,039)	$ (3,225,409)
Net loss per share of common stock, basic and diluted	$ (0.37)	$ (0.45)
Weighted-average shares used to compute basic and diluted net loss per share	13,528,311	7,168,005

Condensed Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (5,052,039)	$ (3,225,409)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	464,158	418,912
Non-cash interest		10,362
Change in fair value of warrant liability	3,072,747
Change in operating assets and liabilities:
Prepaid expenses and other assets	104,184	68,555
Accounts payable and accrued expenses	(275,862)	37,379
Net cash used in operating activities	(1,686,812)	(2,690,201)
Financing activities
Proceeds from issuance of common stock, net	7,334,739	98,744
Net cash provided by financing activities	7,334,739	98,744
Net increase (decrease) in cash and cash equivalents	5,647,927	(2,591,457)
Cash and cash equivalents at beginning of period	9,007,071	8,691,155
Cash and cash equivalents at end of period	$ 14,654,998	6,099,698
Supplemental disclosure of cash flow information
Interest paid		$ 62,563

Organization and Basis of Presentation	3 Months Ended
Organization and Basis of Presentation	Mar. 31, 2017
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 publicly-held 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 product development, raising capital and building infrastructure, and has not realized revenues from its planned principal operations. The Company does not anticipate realizing revenues for the foreseeable future. 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. Sale of Common Stock On February 22, 2017, the Company completed the sale of 2,413,793 shares of the Company’s common stock in an underwritten public offering and on March 3, 2017, the underwriter of the offering exercised its option to purchase an additional 362,068 shares of the Company’s common stock. Gross proceeds from this offering were $8.0 million. See Note 5 for further description. 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 its sole product, Gimoti™. Although the Company ended the first quarter of 2017 with approximately $14.7 million in cash and cash equivalents, the Company anticipates that it will continue to incur losses from operations due to its plans to fund additional clinical development, including the comparative exposure pharmacokinetic (“PK”) clinical trial, completion of a planned new drug application (“NDA”) submission for Gimoti, pre-approval and pre-commercialization activities, including marketing and manufacturing of Gimoti, and support its 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 financial statements are issued. 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, 2016, 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, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. The Company’s net losses may fluctuate significantly from quarter to quarter and year to year. The Company believes that its current cash and cash equivalents will be sufficient to meet estimated working capital requirements and fund operations through at least February 2018. The Company will need to raise additional debt or equity financing to fund future operations. There can be no assurance that additional financing will be available when needed 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.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The accompanying condensed balance sheet as of December 31, 2016, which has been derived from audited financial statements, and the unaudited interim condensed financial statements, have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and follow the requirements of the U.S. Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP can be condensed or omitted. In management’s opinion, the unaudited interim financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position and its results of operations and its cash flows for the periods presented. These statements do not include all disclosures required by GAAP and should be read in conjunction with the Company’s financial statements and accompanying notes for the year ended December 31, 2016, which are contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 15, 2017. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other interim period.

Use of Estimates

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.

The Company also relies on contract research organizations (“CROs”) to manage and recruit subjects for its clinical trials. If these CROs are unable to continue managing the clinical trials, or are unable to recruit the sufficient number of subjects, the delays could adversely affect the completion of the trials and the timing of the filing of the Company’s NDA with FDA.

In addition, the Company relies on third-party manufacturers for the production of its drug candidate. If the third-party manufacturers are unable to continue manufacturing the Company’s drug candidate, or if the Company loses one of its sole source suppliers used in its manufacturing processes, the Company may not be able to meet clinical trial supply demand for its product candidate and the development of the product candidate could be materially and adversely affected.

Warrant Accounting

Certain of the warrants to purchase shares of the Company’s common stock, issued as a part of the at-the-market registered direct offerings in July and August 2016, are classified as warrant liability and recorded at fair value. These warrants contain a feature that could require the transfer of cash in the event a change of control occurs without the authorization of our Board of Directors, and therefore, are classified as a liability in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 480.

The fair value of each warrant is estimated on the date of issuance, and each subsequent balance sheet date, using the Black-Scholes valuation model using the appropriate risk-free interest rate, expected term and volatility assumptions. The expected life of the warrant was calculated using the remaining life of the warrant. Due to our limited historical data as a public company, the estimated volatility is calculated based upon our historical volatility and comparable companies whose share prices are publicly available for a sufficient period of time. The risk-free rate is based upon U.S. Treasury securities with remaining terms similar to the expected term of the stock award being valued.

This warrant liability is subject to remeasurement at each balance sheet date and the Company recognizes any change in the fair value of the warrant liability in the statement of operations. The Company will continue to adjust the carrying value of the warrants for changes in the estimated fair value until the earlier of the modification, exercise or expiration of the warrants. At that time, the liabilities will be reclassified to additional paid-in capital, a component of stockholders’ equity. We anticipate that the value of the warrants could fluctuate from quarter to quarter and that such fluctuation could have a material impact on our financial statements.

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 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 to perform research, conduct clinical trials and develop drug materials and delivery devices. 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.

The Company bases its expense accruals related to clinical studies on estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and CROs that conduct and manage clinical studies on its behalf. The financial terms of these agreements vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors, such as the successful enrollment of patients, site initiation and the completion of clinical study milestones. 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 will be performed and the level of effort to be 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.

Included in research and development expenses were costs of approximately $4,500 for the three months ended March 31, 2017, for clinical trial services incurred by a related party of one of the Company’s officers. There were no related party costs incurred during the three months ended March 31, 2016.

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 preclinical research and clinical trials. Other than an agreement with Cosma S.p.A. to supply metoclopramide for the manufacture of Gimoti, and with Patheon UK Limited to manufacture Gimoti for the comparative exposure PK trial, the Company does not have any other contractual relationships for the manufacture of commercial supplies of Gimoti. If Gimoti is approved by any regulatory agency, the Company intends to enter into agreements with third-party contract manufacturers for the commercial production at that time. The Company currently utilizes a third-party consultant, which it engages on an as-needed, hourly basis, to manage its manufacturing contractors.

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. The Company has excluded 45,000 shares of common stock subject to repurchase from the weighted-average number of common stock outstanding for the three months ended March 31, 2017 and 2016. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of shares subject to repurchase, warrants for the purchase of common stock, options outstanding 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:

	Three Months Ended March 31,
	2017		2016
Common stock subject to repurchase		45,000		45,000
Warrants to purchase common stock		2,797,561		118,881
Common stock options		1,925,624		1,161,624
Employee stock purchase plan		5,185		2,760
Total excluded securities		4,773,370		1,328,265

Recent Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases. 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. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. A modified retrospective transition approach is required for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. The Company is currently evaluating the impact of its pending adoption of the new standard on the Company’s financial statements.

In March 2016, the FASB issued ASU No. 2016-09 Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. This guidance changes the accounting for certain aspects of share-based payments to employees. The guidance requires the recognition of the income tax effects of awards in the income statement when the awards vest or are settled, thus eliminating additional paid-in capital pools. The guidance also allows for the employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting. In addition, the guidance allows for a policy election to account for forfeitures as they occur rather than on an estimated basis. This guidance is effective for annual and interim reporting periods of public entities beginning after December 15, 2016. The adoption of this statement did not have a material impact on the Company’s financial statements.

Technology Acquisition Agreement

3 Months Ended

Mar. 31, 2017

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 made to Questcor, the Company may also be required to make additional milestone payments totaling up to $51.5 million. These milestones include up to $4.5 million in payments if Gimoti achieves the following development targets:

•

$1.5 million upon FDA’s acceptance for review of a new drug application for Gimoti; and

•

$3 million upon FDA’s approval of 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 to 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 2030.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1497-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1490-128463

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1486-128463

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1524-128463

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7000-128479

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4922-128472

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4934-128472

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4926-128472

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=73530397&loc=SL65897772-128472

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1383-128463

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6996-128479

+ Details

Stockholders' Equity

3 Months Ended

Mar. 31, 2017

Equity [Abstract]

Stockholders' Equity

5. Stockholders’ Equity

Sale of Common Stock and Warrants

On July 25, 2016, the Company completed a registered direct offering of 1,804,512 shares of common stock at a purchase price of $2.49375 per share (the “July 2016 Financing”). Concurrently in a private placement, for each share of common stock purchased by an investor, such investor received from the Company an unregistered warrant to purchase three-quarters of a share of common stock, for a total of 1,353,384 shares (the “July Warrants”). The July Warrants have an exercise price of $2.41 per share, are immediately exercisable and will expire on January 25, 2022. The aggregate gross proceeds from the sale of the common stock and warrants were $4.5 million, and the net proceeds after deduction of commissions and fees were $4.0 million.

In connection with the July 2016 Financing, the Company issued to its placement agent, Rodman & Renshaw, a unit of H.C. Wainwright & Co. LLC (“Wainwright”), and its designees unregistered warrants to purchase an aggregate of 90,226 shares of the Company’s common stock (the “July Wainwright Warrants”). The July Wainwright Warrants have substantially the same terms as the July Warrants, except that the July Wainwright Warrants will expire on July 21, 2021 and have an exercise price equal to $3.1172 per share of common stock.

On August 3, 2016, the Company completed a registered direct offering of 3,244,120 shares of common stock at a purchase price of $3.0825 per share (the “August 2016 Financing”) and together with the July 2016 Financing (the “2016 Financings”). Concurrently in a private placement, for each share of common stock purchased by an investor, such investor received from the Company an unregistered warrant to purchase one half of a share of common stock, for a total of 1,622,060 shares (the “August Warrants”). The August Warrants have an exercise price of $3.03 per share, are immediately exercisable and will expire on February 3, 2022. The aggregate gross proceeds from the sale of the common stock and warrants were $10 million, and the net proceeds after deduction of commissions and fees was approximately $9.2 million.

In connection with the August 2016 financing, the Company issued to its placement agent, Wainwright, and its designees unregistered warrants to purchase an aggregate of 162,206 shares of the Company’s common stock (the “August Wainwright Warrants”). The August Wainwright Warrants have substantially the same terms as the August Warrants, except that the August Wainwright Warrants will expire on July 29, 2021 and have an exercise price equal to $3.853125 per share of common stock.

The warrants issued in connection with the 2016 Financings had a total initial fair value of $4,899,459 on their respective closing dates as determined using the Black Scholes pricing model and such value was recorded as the initial carrying value of the warrant liability. The fair value of the warrants is remeasured at each financial reporting period with any change in fair value recognized as a change in fair value of the warrant liability in the Statement of Operations.

On December 15, 2016, the Company entered into amendments (the “Warrant Amendments”) with certain of the holders (the “Holders”) of the Company’s outstanding warrants to purchase common stock issued on July 25, 2016 and August 3, 2016. Pursuant to the Warrant Amendments, the Holders’ right to require the Company to purchase the outstanding warrants upon the occurrence of certain fundamental transactions will not apply if the fundamental transaction is a result of a transaction that has not been approved by the Company’s board of directors. As a result of this amendment, warrants to purchase 252,432 shares of the Company’s common stock were no longer required to be classified as liabilities. The value of amended warrants were adjusted to their fair value immediately prior to the amendment and approximately $207,000 was reclassified from warrant liability to Additional Paid-in Capital.

On February 16, 2017, an institutional investor from the Company’s financing which closed in July 2016 converted its warrant to purchase 526,315 shares of our common stock by a “cashless” exercise and received 211,860 shares of the Company’s common stock. The warrant had an exercise price of $2.41 per share. The shares were issued, and the warrants were sold, in reliance upon the registration exemption set forth in Section 4(a)(2) of the Securities Act of 1933, as amended. The value of the exercised warrants were adjusted to their fair value immediately prior to the exercise and approximately $1.4 million was reclassified from warrant liability to Additional Paid-in Capital. Subsequent to this transaction, warrants to purchase 2,449,129 shares of the Company’s common stock remain classified as a liability.

Sale of Common Stock in Public Offering

In February and March 2017, the Company completed the sale of 2,775,861 shares of its common stock in an underwritten public offering led by Laidlaw & Company (UK) Ltd. The price to the public in this offering was $2.90 per share resulting in gross proceeds to the Company of approximately $8.0 million. After deducting underwriting discounts and commissions and estimated offering expenses payable by the Company, the net proceeds to the Company from this offering was approximately $7.3 million.

At the Market Equity Offering Program

On April 15, 2016, the Company terminated its At Market Sales Agreement with MLV & Co. LLC and entered into a new At Market Issuance Sales Agreement with FBR & Co. (“FBR”) (“FBR Sales Agreement”), and filed a prospectus supplement, pursuant to which the Company may sell from time to time, at its option, up to an aggregate of 649,074 shares of the Company’s common stock through FBR as the sales agent. The sales of shares made through this equity program are made in “at-the-market” offerings as defined in Rule 415 of the Securities Act. Through December 31, 2016, the Company sold 56,000 shares of common stock at a weighted average price per share of $5.45 and received proceeds of approximately $296,000, net of commissions and fees.

On March 10, 2017, the Company filed a prospectus supplement, which replaced the prospectus supplement filed on April 15, 2016, permitting the Company to sell up to an aggregate of $20.0 million of shares of its common stock through FBR as a sales agent. Under current SEC regulations, if at the time the Company files its Annual Report on Form 10-K, or Form 10-K, the Company’s public float is less than $75 million, and for so long as its public float remains less than $75 million, the amount the Company can raise through primary public offerings of securities in any twelve-month period using shelf registration statements is limited to an aggregate of one-third of the Company’s public float, which is referred to as the baby shelf rules. As of May 5, 2017, the Company’s public float was approximately $36.0 million, based on 12,846,511 shares of outstanding common stock held by non-affiliates and at a price of $2.80 per share, which was the last reported sale price of the Company’s common stock on The Nasdaq Capital Market on May 5, 2017. As a result of the Company’s public float being below $75 million, the Company will be limited by the baby shelf rules until such time as the Company’s public float exceeds $75 million, which means, since the Company has sold approximately $4.8 million in the prior twelve month period under baby shelf rules, the Company only has the capacity to sell approximately $7.2 million of shares. If the Company’s public float decreases, the amount of securities we may sell under our Form S-3 shelf registration statement, including this prospectus supplement, will also decrease. The Company has not sold any shares of common stock through the FBR Sales Agreement during 2017.

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.

Employee Stock Purchase Plan and Equity Incentive Award Plan

As a result of payroll withholdings from the Company’s employees of approximately $80,000 and $99,000, the Company sold 50,244 and 34,067 shares of common stock through its Employee Stock Purchase Plan (“ESPP”) during the three months ended March 31, 2017 and 2016, respectively.

On May 3, 2017, the Company’s stockholders approved an amendment and restatement of the Company’s 2013 ESPP (the “Restated Plan”) to increase the number of shares of common stock reserved under the Restated Plan 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 Restated Plan into 2027.

Stock-Based Compensation

Stock-based compensation expense includes charges related to stock option grants and employee stock purchases under the ESPP. 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 three months ended March 31, 2017 and 2016:

	Three Months Ended March 31,
	2017		2016
Common Stock Options
Risk free interest rate		2.16%	1.25% - 1.575%
Expected option term	6.0 years		5.3 - 6.0 years
Expected volatility of common stock		94.05%	74.44% - 75.91%
Expected dividend yield		0.0%		0.0%

The estimated fair value of each ESPP award 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 three months ended March 31, 2017 and 2016:

	Three Months Ended March 31,
	2017		2016
Employee Stock Purchase Plan
Risk free interest rate		0.79%		0.50%
Expected term	6.0 months		6.0 months
Expected volatility of common stock		99.23%		83.83%
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 as follows:

	Three Months Ended March 31,
	2017		2016
Research and development	$	206,858	$	158,788
General and administrative		257,300		260,124
Total stock-based compensation expense	$	464,158	$	418,912

As of March 31, 2017, there were approximately $2.6 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 1.3 years.

Fair Value Measurements

3 Months Ended

Mar. 31, 2017

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 Note 5, during the third quarter of 2016 the Company entered into the 2016 Financings with an institutional investor providing for the issuance and sale by the Company of 5,048,632 shares of the Company’s common stock and warrants to purchase up to 2,975,444 shares of the Company’s common stock for aggregate gross proceeds of $14.5 million. In addition, as partial payment for services, the Company issued to the underwriters warrants to purchase up to 252,432 shares of the Company’s common stock.

The Company utilizes a valuation hierarchy for disclosure of the inputs to the valuations used to measure fair value. This hierarchy prioritizes 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 is classified as Level 3.

The Company has classified the warrants as a liability and has remeasured the liability to estimated fair value at March 31, 2017 and December 31, 2016, using the Black Scholes option pricing model with the following assumptions:

	March 31, 2017		December 31, 2016
Risk-free interest rate		1.93%		1.93%
Expected volatility	101.44		94.19
Expected term	4.83 years		5.08 years
Expected dividend yield		0.0%		0.0%

The following fair value hierarchy table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016:

	Level 1		Level 2		Level 3		Total
Warrant liability Balance at March 31, 2017	$	—	$	—	$	5,768,675	$	5,768,675
Balance at December 31, 2016	$	—	$	—	$	4,095,019	$	4,095,019

The following table presents a reconciliation of the Company’s liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three months ended March 31, 2017:

	Warrant Liability
Balance at December 31, 2016	$	4,095,019
Issuance of warrants	—
Change in fair value upon re-measurement		3,072,747
Reclassification to Additional Paid-in Capital due to warrant exercise		(1,399,091	)
Balance at March 31, 2017	$	5,768,675

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

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2017

Accounting Policies [Abstract]

Use of Estimates

Warrant Accounting

Stock-Based Compensation

Research and Development Expenses

Net Loss Per Share

	Three Months Ended March 31,
	2017		2016
Common stock subject to repurchase		45,000		45,000
Warrants to purchase common stock		2,797,561		118,881
Common stock options		1,925,624		1,161,624
Employee stock purchase plan		5,185		2,760
Total excluded securities		4,773,370		1,328,265

Recent Accounting Pronouncements

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2017

Equity [Abstract]

Summary of Estimated Fair Value of Stock Option Award

	Three Months Ended March 31,
	2017		2016
Common Stock Options
Risk free interest rate		2.16%	1.25% - 1.575%
Expected option term	6.0 years		5.3 - 6.0 years
Expected volatility of common stock		94.05%	74.44% - 75.91%
Expected dividend yield		0.0%		0.0%

Summary of Estimated Fair Value of Employee Stock Purchase Plan Award

	Three Months Ended March 31,
	2017		2016
Employee Stock Purchase Plan
Risk free interest rate		0.79%		0.50%
Expected term	6.0 months		6.0 months
Expected volatility of common stock		99.23%		83.83%
Expected dividend yield		0.0%		0.0%

Summary of Recognized Non-Cash Stock-Based Compensation Expense

The Company recognized non-cash stock-based compensation expense to employees and directors in its research and development and its general and administrative functions as follows:

	Three Months Ended March 31,
	2017		2016
Research and development	$	206,858	$	158,788
General and administrative		257,300		260,124
Total stock-based compensation expense	$	464,158	$	418,912

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Summary of Warrants Liability and Remeasured Liability to Estimated Fair Value

	March 31, 2017		December 31, 2016
Risk-free interest rate		1.93%		1.93%
Expected volatility	101.44		94.19
Expected term	4.83 years		5.08 years
Expected dividend yield		0.0%		0.0%

Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

	Level 1		Level 2		Level 3		Total
Warrant liability Balance at March 31, 2017	$	—	$	—	$	5,768,675	$	5,768,675
Balance at December 31, 2016	$	—	$	—	$	4,095,019	$	4,095,019

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

	Warrant Liability
Balance at December 31, 2016	$	4,095,019
Issuance of warrants	—
Change in fair value upon re-measurement		3,072,747
Reclassification to Additional Paid-in Capital due to warrant exercise		(1,399,091	)
Balance at March 31, 2017	$	5,768,675

Debt - Additional Information (Detail) - Square 1 Bank [Member] - Loan and Security Agreement [Member] - USD ($)		1 Months Ended
	Aug. 04, 2016	Jul. 31, 2016	Dec. 31, 2014
Debt Instrument [Line Items]
Repayment of principal and accrued interest	$ 4,500,000
Line of credit facility, loan origination cost			$ 82,685
Debt instrument, unamortized discount	38,000
Warrants exercisable, stock issued			22,881
Warrant exercise price per share			$ 5.90
Warrants to purchase common stock [Member]
Debt Instrument [Line Items]
Debt instrument, unamortized discount	$ 59,000
Common stock shares issued upon conversion of warrants		9,887
Warrant value recorded in equity			$ 108,122

Technology Acquisition Agreement - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended
	May 31, 2014	Jun. 30, 2007	Mar. 31, 2017
Technology Acquisition Agreement [Line Items]
Payment expensed as in-process research and development		$ 650,000
Mallinckrodt Plc [Member] \| Patented Technology [Member]
Technology Acquisition Agreement [Line Items]
Expected expiration of patent right			2030
Mallinckrodt Plc [Member] \| Rights and Patents Acquired from Questcor Pharmaceuticals Inc [Member] \| Maximum [Member]
Technology Acquisition Agreement [Line Items]
Milestone payments contingent amount			$ 51,500,000
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 Two And Three [Member] \| Mallinckrodt Plc [Member] \| Maximum [Member]
Technology Acquisition Agreement [Line Items]
Milestone payments contingent amount			$ 4,500,000
Development Target Two [Member] \| Mallinckrodt Plc [Member]
Technology Acquisition Agreement [Line Items]
Development targets description			Upon FDA's acceptance for review of a new drug application for Gimoti
Milestone payments contingent amount			$ 1,500,000
Development Target Three [Member] \| Mallinckrodt Plc [Member]
Technology Acquisition Agreement [Line Items]
Development targets description			Upon the FDA's approval of Gimoti
Milestone payments contingent amount			$ 3,000,000
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 to Mallinckrodt a low single digit royalty on net sales of Gimoti.
Milestone payments contingent amount			$ 47,000,000

Stockholders' Equity - Additional Information (Detail) - USD ($)										2 Months Ended	3 Months Ended			12 Months Ended
	May 03, 2017	Mar. 10, 2017	Mar. 03, 2017	Feb. 22, 2017	Feb. 16, 2017	Dec. 15, 2016	Aug. 03, 2016	Jul. 25, 2016	Apr. 15, 2016	Mar. 31, 2017	Mar. 31, 2017	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	May 05, 2017	May 02, 2017
Sale Of Stock [Line Items]
Common stock, shares issued										15,388,325	15,388,325			12,350,360
Proceeds from issuance of common stock, net											$ 7,334,739		$ 98,744
Value of shares sold in prior twelve months		$ 4,800,000
Payroll withholdings from employees										$ 80,000	$ 80,000		$ 99,000
Issuance of common stock under employee stock purchase plan											50,244		34,067
Unrecognized compensation costs										$ 2,600,000	$ 2,600,000
Weighted average period											1 year 3 months 18 days
Subsequent Event [Member] \| Amended and Restated ESPP 2013 Plan [Member]
Sale Of Stock [Line Items]
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
Aggregate number of shares of common stock reserved under the plan	1,250,000
Award plan expiration year	2027
July 2016 Financing [Member]
Sale Of Stock [Line Items]
Common stock, shares issued								1,804,512
Purchase price of common stock								$ 2.49375
Warrant exercise price per share					$ 2.41
Unregistered warrants to purchase of common stock					526,315					2,449,129	2,449,129
Aggregate gross proceeds from sale of common stock and warrants								$ 4,500,000
Aggregate net proceeds from sale of common stock and warrants								$ 4,000,000
Reclassification of warrant liability to Additional Paid-in Capital					$ 1,400,000
Common stock shares issued upon conversion of warrants					211,860
July Warrants [Member]
Sale Of Stock [Line Items]
Warrants exercisable, stock issued								0.75
Warrant exercise price per share								$ 2.41
Warrants expiration date								Jan. 25, 2022
Unregistered warrants to purchase of common stock								1,353,384
July Wainwright Warrants [Member]
Sale Of Stock [Line Items]
Warrant exercise price per share								$ 3.1172
Warrants expiration date								Jul. 21, 2021
Unregistered warrants to purchase of common stock								90,226
August 2016 Financing [Member]
Sale Of Stock [Line Items]
Common stock, shares issued							3,244,120
Purchase price of common stock							$ 3.0825
Aggregate gross proceeds from sale of common stock and warrants							$ 10,000,000
Aggregate net proceeds from sale of common stock and warrants							$ 9,200,000
August Warrants [Member]
Sale Of Stock [Line Items]
Warrants exercisable, stock issued							0.5
Warrant exercise price per share							$ 3.03
Warrants expiration date							Feb. 03, 2022
Unregistered warrants to purchase of common stock							1,622,060
August Wainwright Warrants [Member]
Sale Of Stock [Line Items]
Warrant exercise price per share							$ 3.853125
Warrants expiration date							Jul. 29, 2021
Unregistered warrants to purchase of common stock							162,206
2016 Financings [Member]
Sale Of Stock [Line Items]
Common stock, shares issued												5,048,632
Aggregate gross proceeds from sale of common stock and warrants												$ 14,500,000
2016 Financings [Member] \| Warrant Liability [Member]
Sale Of Stock [Line Items]
Total initial fair value of warrants issued											$ 4,899,459
Warrant Amendments [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock						252,432
Amendment Date						Dec. 15, 2016
Reclassification of warrant liability to Additional Paid-in Capital						$ 207,000
Underwritten Public Offering [Member]
Sale Of Stock [Line Items]
Purchase price of common stock			$ 2.90	$ 2.90
Issuance of common stock, shares			362,068	2,413,793						2,775,861
Gross proceeds from public offering of common stock			$ 8,000,000							$ 8,000,000
Proceeds from issuance of common stock, net										7,300,000
FBR Sales Agreement [Member]
Sale Of Stock [Line Items]
Common stock, shares issued														56,000
Issuance of common stock, shares											0
Proceeds from issuance of common stock, net														$ 296,000
Common stock, shares issuable									649,074
Common stock , weighted average price per share														$ 5.45
FBR Sales Agreement [Member] \| Subsequent Event [Member]
Sale Of Stock [Line Items]
Entity public float															$ 36,000,000
Entity public float, common stock shares															12,846,511
Common stock, closing price															$ 2.80
FBR Sales Agreement [Member] \| Maximum [Member]
Sale Of Stock [Line Items]
Common stock, value of shares issuable		$ 20,000,000								$ 7,200,000	$ 7,200,000

Stockholders' Equity - Summary of Estimated Fair Value of Stock Option Award (Detail) - Common stock options [Member]	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.16%
Expected option term	6 years
Expected volatility of common stock	94.05%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate		1.25%
Expected option term		5 years 3 months 18 days
Expected volatility of common stock		74.44%
Maximum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate		1.575%
Expected option term		6 years
Expected volatility of common stock		75.91%

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Sep. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock, shares issued		15,388,325	12,350,360
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
2016 Financings [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock, shares issued	5,048,632
Aggregate gross proceeds from sale of common stock and warrants	$ 14,500,000
2016 Financings [Member] \| Maximum [Member] \| Common Stock Warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrants to purchase of common stock	2,975,444
Underwriters [Member] \| Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrants to purchase of common stock	252,432

Debt	3 Months Ended
Debt	Mar. 31, 2017
Debt Disclosure [Abstract]
Debt	3. Debt On August 4, 2016, the Company repaid in full the entire $4.5 million of outstanding principal and interest under the Loan and Security Agreement (the “Loan Agreement”) between the Company and Square 1 Bank (“Square 1”). In connection with such repayment, the Loan Agreement was terminated, and all security, liens or other encumbrances on assets of the Company were released. The Company incurred $82,685 of loan origination costs related to this credit facility. The remaining unamortized costs of approximately $38,000 were charged to interest expense upon the payment of the loan in August 2016. In connection with the funding of the term loan, the Company issued to Square 1 a warrant to purchase 22,881 shares of the Company’s common stock at an exercise price of $5.90 per share, the closing price of the Company’s common stock on the day of funding of the credit facility. During July 2016, Square 1 converted its warrant by a “cashless” conversion and received 9,887 shares of the Company’s common stock. The value determined for the warrant at the time of the grant of $108,122 was recorded as a debt discount, as well as to stockholders’ equity. The remaining unamortized debt discount associated with the warrant of approximately $59,000 was charged to interest expense upon the payment of the loan in August 2016.

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	15,388,325	12,350,360
Common stock, shares outstanding	15,388,325	12,350,360

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Significant Accounting Policies [Line Items]
Shares of common stock subject to repurchase excluded from the weighted-average number of common stock outstanding	45,000	45,000
Officers [Member] \| Clinical Trial Services [Member]
Significant Accounting Policies [Line Items]
Related Party expenses	$ 4,500	$ 0

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	4,773,370	1,328,265
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	45,000	45,000
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	2,797,561	118,881
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	1,925,624	1,161,624
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	5,185	2,760

Stockholders' Equity - Summary of Recognized Non-Cash Stock-Based Compensation Expense (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 464,158	$ 418,912
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	206,858	158,788
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 257,300	$ 260,124

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurement, Recurring [Member] - Warrant Liability [Member] - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value	$ 5,768,675	$ 4,095,019
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value	$ 5,768,675	$ 4,095,019

Fair Value Measurements - Summary of Reconciliation of Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Detail) - Fair Value Measurement, Recurring [Member] - Warrant Liability [Member]	3 Months Ended
	Mar. 31, 2017 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2016	$ 4,095,019
Change in fair value upon re-measurement	3,072,747
Reclassification to Additional Paid-in Capital due to warrant exercise	(1,399,091)
Balance at March 31, 2017	$ 5,768,675