View Filing Data

December 31,

2017

Risk-free interest rate

Expected volatility

Expected term

Expected dividend yield

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	EVOK
Entity Registrant Name	Evoke Pharma Inc
Entity Central Index Key	0001403708
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		17,427,533

Condensed Balance Sheets (Unaudited) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 6,567,918	$ 7,679,267
Prepaid expenses	438,957	251,046
Total current assets	7,006,875	7,930,313
Other assets	11,551	11,551
Total assets	7,018,426	7,941,864
Current Liabilities:
Accounts payable and accrued expenses	625,994	1,048,927
Accrued compensation	984,683	1,025,911
Total current liabilities	1,610,677	2,074,838
Warrant liability		3,701,277
Total liabilities	1,610,677	5,776,115
Stockholders' equity:
Common stock, $0.0001 par value; authorized shares - 50,000,000; issued and outstanding shares - 17,427,533 and 15,413,610 at September 30, 2018 and December 31, 2017, respectively	1,743	1,541
Additional paid-in capital	82,250,109	73,202,863
Accumulated deficit	(76,844,103)	(71,038,655)
Total stockholders' equity	5,407,749	2,165,749
Total liabilities and stockholders' equity	$ 7,018,426	$ 7,941,864

Condensed Statements of Operations (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating expenses:
Research and development	$ 625,497	$ 2,717,698	$ 3,399,654	$ 5,505,953
General and administrative	897,060	984,047	2,846,611	3,065,595
Total operating expenses	1,522,557	3,701,745	6,246,265	8,571,548
Loss from operations	(1,522,557)	(3,701,745)	(6,246,265)	(8,571,548)
Other income (expense):
Interest income	3,089	2,822	7,425	5,452
Change in fair value of warrant liability		(1,544,138)	433,392	(3,354,973)
Total other income (expense)	3,089	(1,541,316)	440,817	(3,349,521)
Net loss	$ (1,519,468)	$ (5,243,061)	$ (5,805,448)	$ (11,921,069)
Net loss per share of common stock, basic	$ (0.09)	$ (0.34)	$ (0.36)	$ (0.81)
Net loss per share of common stock, diluted	$ (0.09)	$ (0.34)	$ (0.36)	$ (0.84)
Weighted-average shares used to compute basic net loss per share	17,129,649	15,351,295	16,327,385	14,740,977
Weighted-average shares used to compute diluted net loss per share	17,129,649	15,351,295	16,327,385	14,766,853

Condensed Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (5,805,448)	$ (11,921,069)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,161,266	1,404,926
Change in fair value of warrant liability	(433,392)	3,354,973
Change in operating assets and liabilities:
Prepaid expenses and other assets	(187,911)	(59,020)
Accounts payable and accrued expenses	(464,161)	1,236,986
Net cash used in operating activities	(5,729,646)	(5,983,204)
Financing activities
Proceeds from issuance of common stock, net	4,618,297	7,389,101
Net cash provided by financing activities	4,618,297	7,389,101
Net increase (decrease) in cash and cash equivalents	(1,111,349)	1,405,897
Cash and cash equivalents at beginning of period	7,679,267	9,007,071
Cash and cash equivalents at end of period	6,567,918	10,412,968
Non-cash financing activities
Reclassification of warrant liability to equity due to exercise of warrants		$ 1,399,091
Reclassification of warrant liability to equity due to amendment of warrants	$ 3,267,885

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The accompanying condensed balance sheet as of December 31, 2017, 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, 2017, which are contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 7, 2018. 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.

Contract Research Organizations

The Company relies on contract research organizations (“CROs”) and consultants to assist with ongoing regulatory discussions and submissions supporting the NDA. If these 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, 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.

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 will no longer be classified as a liability on the Company’s balance sheet, were adjusted to fair value as of the date of the Warrant Amendments, and 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 our 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.

The fair value of each warrant was 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 the Company’s limited historical data as a public company, 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 risk-free rate was based upon U.S. Treasury securities with remaining terms similar to the expected term of the stock award being valued.

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 and, if necessary, 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 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.

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 excluded 45,000 shares of common stock subject to repurchase from the weighted-average number of common stock outstanding for the three and nine months ended September 30, 2017. Since June 2018 when the Company’s repurchase right lapsed upon the filing of the NDA, 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 0 and 25,055 weighted-average shares from the weighted-average number of common stock outstanding for the three and nine months ended September 30, 2018, respectively. 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 common stock 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 their inclusion would be anti-dilutive:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Common stock subject to repurchase	—			45,000		25,055		45,000
Warrants to purchase common stock		2,713,561		2,797,561		2,713,561		2,771,685
Common stock options		3,017,624		2,131,624		3,017,624		2,131,624
Employee stock purchase plan		2,697		7,064		2,697		7,064
Total excluded securities		5,733,882		4,981,249		5,758,937		4,955,373

The following table sets forth the calculation of basic and diluted net loss per share:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017

Net loss attributable to common shareholders for basic net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(11,921,069	)
Adjustment for loss from change in fair value of warrants	—			—			—				(429,702	)
Net loss used for diluted net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(12,350,771	)

Weighted-average shares used to compute basic net loss per share		17,129,649			15,351,295			16,327,385			14,740,977
Adjustment to reflect assumed exercise of warrants	—			—			—				25,876
Weighted-average shares used to compute diluted net loss per share		17,129,649			15,351,295			16,327,385			14,766,853

Net loss per share attributable to common shareholders:
Basic	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.81	)
Diluted	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.84	)

Recent Accounting Pronouncements

In February 2016, the FASB issued Accounting Standards Update (“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. In July 2018, the FASB issued ASU No. 2018-11, Leases – Targeted Improvements to provide entities with relief from the costs of implementing certain aspects of ASU No. 2016-02. Specifically, under the amendments in ASU No. 2018-11, entities may (1) elect not to recast the comparative periods presented when transitioning to the new leasing standard, and (2) lessors may elect not to separate lease and non-lease components when certain conditions are met. ASU No. 2018-11 has the same effective date as ASU No. 2016-02. The Company’s only significant lease is its facility lease, which expires on December 31, 2019. The Company does not expect the pending adoption of the new standard to have a material impact on the Company’s financial statements.

Stockholders' Equity

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Stockholders' Equity

4. Stockholders’ Equity

Warrants

In February 2017, an institutional investor from the Company’s financing which closed in July 2016 converted its warrant to purchase 526,315 shares of the Company’s 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 was adjusted to the fair value immediately prior to the exercise and approximately $1.4 million was reclassified from warrant liability to additional paid-in capital, a component of stockholders’ equity.

In March 2018, the Company entered into the Warrant Amendments with each of the holders of the Company’s outstanding Warrants. As a result of the Warrant Amendments, all of the remaining Warrants to purchase 2,449,129 shares of the Company’s common stock are 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 gain of approximately $433,000 in the statement of operations, 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.

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. 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 offering expenses paid by the Company, the net proceeds to the Company from this offering was approximately $7.3 million.

At the Market Equity Offering Program

In November 2017, the Company filed a new shelf registration with the SEC on Form S-3 to replace a prior Form S-3 shelf registration which was set to expire on November 25, 2017. This new shelf registration was declared effective by the SEC on December 28, 2017. The new 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”). The Company did not sell any shares of common stock through the FBR Sales Agreement during 2017. During the nine months ended September 30, 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. From October 1, 2018 through October 31, 2018, the Company has not sold any additional shares of common stock pursuant to the FBR Sales Agreement.

Under current SEC regulations, if at the time the Company files its Annual Report on Form 10-K (“Form 10-K”), and 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 October 31, 2018, the Company’s public float was approximately $47.8 million, based on 14,349,303 shares of outstanding common stock held by non-affiliates and at a price of $3.33 per share, which was the last reported sale price of the Company’s common stock on the Nasdaq Capital Market on September 17, 2018. 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 the Company only has the capacity to sell shares up to one-third of its public float under shelf registration statements in any twelve-month period. If the Company’s public float decreases, the amount of securities the Company may sell under its Form S-3 shelf registration statement will also decrease. As of October 31, 2018, the Company had the capacity to issue up to approximately $11.2 million worth of additional 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.

Employee Stock Purchase Plan and Equity Incentive Award Plan

As a result of payroll withholdings from the Company’s employees of approximately $47,000 and $135,000, the Company sold 28,869 and 75,529 shares of common stock through its ESPP during the nine months ended September 30, 2018 and 2017, respectively.

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.

On April 26, 2018, the Company’s stockholders approved the amendment and restatement of the Company’s 2013 Equity Incentive Award Plan (the “Restated Equity Incentive Plan”) to increase the number of shares of common stock authorized for issuance under the Restated Equity Incentive Plan by 1,500,000 shares, to an aggregate of 6,286,425 shares, and to extend the term of the Restated Equity Incentive 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 Equity Incentive Plan may not exceed an aggregate of 8,000,000 shares.

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 nine months ended September 30, 2018 and 2017:

	Nine Months Ended September 30,
	2018	2017
Common Stock Options
Risk free interest rate	2.66% - 2.85%	1.93% - 2.16%
Expected option term	5.5 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	90.15% - 92.30%	94.05% - 98.25%
Expected dividend yield	0.0%	0.0%

There were no stock options granted during the three months ended September 30, 2018 and 2017.

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 three and nine months ended September 30, 2018 and 2017:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2018	2017	2018	2017
Employee Stock Purchase Plan
Risk free interest rate	2.29%	1.10%	1.85% - 2.29%	0.79% - 1.10%
Expected term	6 months	6 months	6 months	6 months
Expected volatility of common stock	45.24%	37.60%	45.24% - 58.76%	37.60% - 99.23%
Expected dividend yield	0.0%	0.0%	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 September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development	$	161,515	$	200,773	$	519,025	$	626,976
General and administrative		218,547		275,124		642,241		777,950
Total stock-based compensation expense	$	380,062	$	475,897	$	1,161,266	$	1,404,926

As of September 30, 2018, there were approximately $2.2 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.

Fair Value Measurements

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. 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.

During the third quarter of 2016 the Company entered into an agreement 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.

As noted in Notes 2 and 4, 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, were classified as Level 3.

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

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 nine months ended September 30, 2018 and 2017:

	September 30,
	2018			2017
Beginning balance of warrant liability	$	3,701,277		$	4,095,019
Change in fair value upon re-measurement		(433,392	)		3,354,973
Reclassification to Additional Paid-in Capital due to warrant exercise	—				(1,399,091	)
Reclassification to Additional Paid-in Capital due to warrant amendment		(3,267,885	)	—
Ending balance of warrant liability	$	-		$	6,050,901

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)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Use of Estimates

Contract Research Organizations

Warrant Accounting

Stock-Based Compensation

Research and Development Expenses

Net Loss Per Share

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Common stock subject to repurchase	—			45,000		25,055		45,000
Warrants to purchase common stock		2,713,561		2,797,561		2,713,561		2,771,685
Common stock options		3,017,624		2,131,624		3,017,624		2,131,624
Employee stock purchase plan		2,697		7,064		2,697		7,064
Total excluded securities		5,733,882		4,981,249		5,758,937		4,955,373

The following table sets forth the calculation of basic and diluted net loss per share:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017

Net loss attributable to common shareholders for basic net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(11,921,069	)
Adjustment for loss from change in fair value of warrants	—			—			—				(429,702	)
Net loss used for diluted net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(12,350,771	)

Weighted-average shares used to compute basic net loss per share		17,129,649			15,351,295			16,327,385			14,740,977
Adjustment to reflect assumed exercise of warrants	—			—			—				25,876
Weighted-average shares used to compute diluted net loss per share		17,129,649			15,351,295			16,327,385			14,766,853

Net loss per share attributable to common shareholders:
Basic	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.81	)
Diluted	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.84	)

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2018

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 their inclusion would be anti-dilutive:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Common stock subject to repurchase	—			45,000		25,055		45,000
Warrants to purchase common stock		2,713,561		2,797,561		2,713,561		2,771,685
Common stock options		3,017,624		2,131,624		3,017,624		2,131,624
Employee stock purchase plan		2,697		7,064		2,697		7,064
Total excluded securities		5,733,882		4,981,249		5,758,937		4,955,373

Summary of Calculation of Basic and Diluted Net Loss Per Share

The following table sets forth the calculation of basic and diluted net loss per share:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017

Net loss attributable to common shareholders for basic net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(11,921,069	)
Adjustment for loss from change in fair value of warrants	—			—			—				(429,702	)
Net loss used for diluted net loss per share	$	(1,519,468	)	$	(5,243,061	)	$	(5,805,448	)	$	(12,350,771	)

Weighted-average shares used to compute basic net loss per share		17,129,649			15,351,295			16,327,385			14,740,977
Adjustment to reflect assumed exercise of warrants	—			—			—				25,876
Weighted-average shares used to compute diluted net loss per share		17,129,649			15,351,295			16,327,385			14,766,853

Net loss per share attributable to common shareholders:
Basic	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.81	)
Diluted	$	(0.09	)	$	(0.34	)	$	(0.36	)	$	(0.84	)

Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Summary of Estimated Fair Value of Stock Option Award

	Nine Months Ended September 30,
	2018	2017
Common Stock Options
Risk free interest rate	2.66% - 2.85%	1.93% - 2.16%
Expected option term	5.5 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	90.15% - 92.30%	94.05% - 98.25%
Expected dividend yield	0.0%	0.0%

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

	Three Months Ended September 30,		Nine Months Ended September 30,
	2018	2017	2018	2017
Employee Stock Purchase Plan
Risk free interest rate	2.29%	1.10%	1.85% - 2.29%	0.79% - 1.10%
Expected term	6 months	6 months	6 months	6 months
Expected volatility of common stock	45.24%	37.60%	45.24% - 58.76%	37.60% - 99.23%
Expected dividend yield	0.0%	0.0%	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 September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development	$	161,515	$	200,773	$	519,025	$	626,976
General and administrative		218,547		275,124		642,241		777,950
Total stock-based compensation expense	$	380,062	$	475,897	$	1,161,266	$	1,404,926

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Summary of Warrants Liability and Remeasured Liability to Estimated Fair Value

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

	September 30,
	2018			2017
Beginning balance of warrant liability	$	3,701,277		$	4,095,019
Change in fair value upon re-measurement		(433,392	)		3,354,973
Reclassification to Additional Paid-in Capital due to warrant exercise	—				(1,399,091	)
Reclassification to Additional Paid-in Capital due to warrant amendment		(3,267,885	)	—
Ending balance of warrant liability	$	-		$	6,050,901

Summary of Significant Accounting Policies - Summary of Calculation of Basic and Diluted Net Loss Per Share (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net loss attributable to common shareholders for basic net loss per share	$ (1,519,468)	$ (5,243,061)	$ (5,805,448)	$ (11,921,069)
Adjustment for loss from change in fair value of warrants				(429,702)
Net loss used for diluted net loss per share	$ (1,519,468)	$ (5,243,061)	$ (5,805,448)	$ (12,350,771)
Weighted-average shares used to compute basic net loss per share	17,129,649	15,351,295	16,327,385	14,740,977
Adjustment to reflect assumed exercise of warrants				25,876
Weighted-average shares used to compute diluted net loss per share	17,129,649	15,351,295	16,327,385	14,766,853
Basic	$ (0.09)	$ (0.34)	$ (0.36)	$ (0.81)
Diluted	$ (0.09)	$ (0.34)	$ (0.36)	$ (0.84)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

+ Details

- Definition

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

+ References + Details

Stockholders' Equity - Common Stock - Additional Information (Detail) - USD ($)	1 Months Ended	2 Months Ended	9 Months Ended
	Oct. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Nov. 30, 2017
Sale Of Stock [Line Items]
Proceeds from issuance of common stock, net			$ 4,618,297	$ 7,389,101
Common stock, shares issued			17,427,533		15,413,610
Underwritten Public Offering [Member]
Sale Of Stock [Line Items]
Common stock shares issues		2,775,861
Purchase price of common stock		$ 2.90
Gross proceeds from public offering of common stock		$ 8,000,000
Proceeds from issuance of common stock, net		$ 7,300,000
FBR Sales Agreement [Member]
Sale Of Stock [Line Items]
Proceeds from issuance of common stock, net			$ 4,600,000
Common stock, shares issued			1,985,054
Common stock , weighted average price per share			$ 2.38
FBR Sales Agreement [Member] \| Maximum [Member]
Sale Of Stock [Line Items]
Common stock, value of shares issuable						$ 16,000,000
Entity public float			$ 75,000,000
FBR Sales Agreement [Member] \| Subsequent Event [Member]
Sale Of Stock [Line Items]
Additional common stock, shares issued	0
Entity public float	$ 47,800,000
Entity public float, common stock shares	14,349,303
Common stock, closing price	$ 3.33
Proceeds from issuance of additional common stock	$ 11,200,000

Stockholders' Equity - Employee Stock Purchase Plan and Equity Incentive Award Plan and Stock-Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 26, 2018	May 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	May 03, 2017	May 02, 2017
Sale Of Stock [Line Items]
Payroll withholdings from employees			$ 47,000	$ 135,000	$ 47,000	$ 135,000
Issuance of common stock under employee stock purchase plan					28,869	75,529
Aggregate number of shares of common stock reserved under the plan	6,286,425
Award plan expiration month and year	2028-02
Stock options granted			0	0
Unrecognized compensation costs			$ 2,200,000		$ 2,200,000
Weighted average period					1 year 2 months 26 days
Amended and ESPP 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
Amended and Restated Equity Incentive Plan 2013 [Member]
Sale Of Stock [Line Items]
Increase in number of shares of common stock reserved under the plan	1,500,000
Aggregate number of shares of common stock reserved under the plan	8,000,000
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 Equity Incentive Plan may not exceed an aggregate of 8,000,000 shares.
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%

Stockholders' Equity - Summary of Estimated Fair Value of Shares to be Acquired Under Employee Stock Purchase Plan (Detail) - Employee stock purchase plan [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.29%	1.10%
Risk free interest rate, minimum			1.85%	0.79%
Risk free interest rate, maximum			2.29%	1.10%
Expected term	6 months	6 months	6 months	6 months
Expected volatility of common stock	45.24%	37.60%
Expected volatility of common stock, minimum			45.24%	37.60%
Expected volatility of common stock, maximum			58.76%	99.23%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Sep. 30, 2016	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock, shares issued		17,427,533	15,413,610
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

Organization and Basis of Presentation	9 Months Ended
Organization and Basis of Presentation	Sep. 30, 2018
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, Gimoti™, and has not realized revenues from its planned principal operations. The Company filed a New Drug Application (“NDA”) for Gimoti with the U.S. Food and Drug Administration (“FDA”) on June 1, 2018, which was accepted and is being reviewed by FDA. However, 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 the third quarter of 2018 with approximately $6.6 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, marketing and manufacturing of Gimoti, and 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 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, 2017, 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 that its current cash and cash equivalents as of September 30, 2018 will be sufficient to meet estimated working capital requirements and fund operations through June 2019. The Company will need to raise additional cash through debt, equity or other forms of financing, such as potential collaboration arrangements, 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.

Technology Acquisition Agreement	9 Months Ended
Technology Acquisition Agreement	Sep. 30, 2018
Technology Acquisition Agreement [Abstract]
Technology Acquisition Agreement	3. 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 one year 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.

Technology Acquisition Agreement - Additional Information (Detail)	1 Months Ended		9 Months Ended
	May 31, 2014 USD ($)	Jun. 30, 2007 USD ($)	Sep. 30, 2018 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 to Mallinckrodt a low single digit royalty on net sales of Gimoti.
Milestone payments contingent amount			$ 47,000,000

Stockholders' Equity - Warrants - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2018	Feb. 28, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sale Of Stock [Line Items]
Change in fair value of warrant liability			$ (1,544,138)	$ 433,392	$ (3,354,973)
July 2016 Financing [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock		526,315
Conversion of stock, shares issued		211,860
Weighted average exercise price of warrants		$ 2.41
Reclassification of warrant liability to Additional Paid-in Capital		$ 1,400,000
Warrant Amendments [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock	2,449,129			2,449,129
Reclassification of warrant liability to Additional Paid-in Capital				$ 3,300,000
Change in fair value of warrant liability				$ 433,000
Amendment date				2018-03
Underwriters [Member]
Sale Of Stock [Line Items]
Unregistered warrants to purchase of common stock expired	84,000

Fair Value Measurements - Summary of Warrants Liability and Remeasured Liability to Estimated Fair Value (Detail)	12 Months Ended
	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative Investment, Measurement Input [Extensible List]	evok:BlackScholesOptionPricingModelMember
Risk-free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Estimated fair value assumptions	2.09
Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Estimated fair value assumptions	100.39
Expected Term [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term	4 years 29 days
Expected Dividend Yield [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Estimated fair value assumptions	0.0

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
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	17,427,533	15,413,610
Common stock, shares outstanding	17,427,533	15,413,610

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] - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 3,701,277	$ 4,095,019
Change in fair value upon re-measurement	(433,392)	3,354,973
Reclassification to Additional Paid-in Capital due to warrant exercise		(1,399,091)
Reclassification to Additional Paid-in Capital due to warrant amendment	$ (3,267,885)
Ending balance		$ 6,050,901