Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Mar. 09, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	CPRX
Entity Registrant Name	CATALYST PHARMACEUTICALS, INC.
Entity Central Index Key	0001369568
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		102,556,164
Entity Public Float			$ 216,521,603

Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 57,496,702	$ 13,893,064
Short-term investments	26,516,711	26,512,753
Prepaid expenses and other current assets	1,173,744	1,047,944
Total current assets	85,187,157	41,453,761
Property and equipment, net	191,385	244,204
Deposits	8,888	8,888
Total assets	85,387,430	41,706,853
Current Liabilities:
Accounts payable	1,945,575	933,176
Accrued expenses and other liabilities	2,320,587	1,161,359
Total current liabilities	4,266,162	2,094,535
Accrued expenses and other liabilities, non-current	157,456	181,162
Warrants liability, at fair value		122,226
Total liabilities	4,423,618	2,397,923
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized: none issued and outstanding at December 31, 2017 and 2016
Common stock, $0.001 par value, 150,000,000 shares authorized; 102,549,498 shares and 82,972,316 shares issued and outstanding at December 31, 2017 and 2016, respectively	102,549	82,972
Additional paid-in capital	207,421,710	147,374,028
Accumulated deficit	(126,560,447)	(108,148,070)
Total stockholders' equity	80,963,812	39,308,930
Total liabilities and stockholders' equity	$ 85,387,430	$ 41,706,853

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	102,549,498	82,972,316
Common stock, shares outstanding	102,549,498	82,972,316

Consolidated Statements of Operations - USD ($)	12 Months Ended
Consolidated Statements of Operations - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues	$ 0	$ 0	$ 0
Operating costs and expenses:
Research and development	11,375,237	11,369,941	11,801,342
General and administrative	7,304,399	7,910,260	8,597,010
Total operating costs and expenses	18,679,636	19,280,201	20,398,352
Loss from operations	(18,679,636)	(19,280,201)	(20,398,352)
Other income, net	454,163	321,612	100,389
Change in fair value of warrants liability	(186,904)	886,137	65,005
Loss before income taxes	(18,412,377)	(18,072,452)	(20,232,958)
Provision for income taxes	0	0	0
Net loss	$ (18,412,377)	$ (18,072,452)	$ (20,232,958)
Net loss per share - basic and diluted	$ (0.21)	$ (0.22)	$ (0.25)
Weighted average shares outstanding - basic and diluted	85,802,487	82,875,281	80,858,393

Consolidated Statement of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2014	$ 35,242,330	$ 69,119	$ 105,015,871	$ (69,842,660)
Issuance of common stock, net	34,873,869	11,527	34,862,342
Issuance of stock options for services	1,510,018		1,510,018
Amortization of restricted stock for services	75,440		75,440
Exercise of warrants for common stock	3,617,261	1,178	3,616,083
Exercise of stock options for common stock	390,351	1,027	389,324
Net loss	(20,232,958)			(20,232,958)
Ending Balance at Dec. 31, 2015	55,476,311	82,851	145,469,078	(90,075,618)
Issuance of common stock, net		27	(27)
Issuance of stock options for services	1,760,591		1,760,591
Amortization of restricted stock for services	75,494		75,494
Exercise of stock options for common stock	68,986	94	68,892
Net loss	(18,072,452)			(18,072,452)
Ending Balance at Dec. 31, 2016	39,308,930	82,972	147,374,028	(108,148,070)
Issuance of common stock, net	53,772,560	16,455	53,756,105
Issuance of stock options for services	2,342,625		2,342,625
Amortization of restricted stock for services	65,336		65,336
Exercise of warrants for common stock	3,518,553	2,258	3,516,295
Exercise of stock options for common stock	368,185	864	367,321
Net loss	(18,412,377)			(18,412,377)
Ending Balance at Dec. 31, 2017	$ 80,963,812	$ 102,549	$ 207,421,710	$ (126,560,447)

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net loss	$ (18,412,377)	$ (18,072,452)	$ (20,232,958)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	45,689	43,406	34,468
Stock-based compensation	2,407,961	1,836,085	1,585,458
Change in fair value of warrants liability	186,904	(886,137)	(65,005)
(Increase) decrease in:
Prepaid expenses and other current assets and deposits	(125,800)	456,794	(452,040)
Increase (decrease) in:
Accounts payable	1,012,399	(860,951)	(20,083)
Accrued expenses and other liabilities	1,142,652	(480,248)	1,134,939
Net cash used in operating activities	(13,742,572)	(17,963,503)	(18,015,221)
Investing Activities:
Capital expenditures		(96,061)	(23,465)
Proceeds (purchase) of short-term investments	(3,958)	(68,603)	18,812
Proceeds (purchase) of certificates of deposit		3,717,229	(1,846)
Net cash provided by (used in) investing activities	(3,958)	3,552,565	(6,499)
Financing Activities:
Proceeds from issuance of common stock, net	53,772,560		34,873,869
Payment of employee withholding tax related to stock- based compensation		(11,265)
Proceeds from exercise of warrants	3,209,423		1,895,738
Proceeds from exercise of options	368,185	80,251	390,351
Net cash provided by financing activities	57,350,168	68,986	37,159,958
Net increase (decrease) in cash and cash equivalents	43,603,638	(14,341,952)	19,138,238
Cash and cash equivalents - beginning of period	13,893,064	28,235,016	9,096,778
Cash and cash equivalents - end of period	57,496,702	$ 13,893,064	28,235,016
Non-cash investing and financing activities:
Exercise of liability classified warrants for common stock	$ 309,130		1,721,523
Non-cash incentive received from lessor			$ 131,175

Organization and Description of Business

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Description of Business

1.	Organization and Description of Business

Catalyst Pharmaceuticals, Inc. and subsidiary (collectively, the Company), is a development-stage biopharmaceutical company focused on developing and commercializing innovating therapies for people with rare debilitating, chronic neuromuscular and neurological diseases, including Lambert-Eaton Myasthenic Syndrome (LEMS), Congenital Myasthenic Syndromes (CMS), MuSK antibody positive myasthenia gravis, and infantile spasms. The Company (f/k/a Catalyst Pharmaceutical Partners, Inc.) was incorporated in Delaware in July 2006. It is the successor by merger to Catalyst Pharmaceutical Partners, Inc., a Florida corporation, which commenced operations in January 2002.

Since inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff, acquiring operating assets and raising capital. The Company’s primary focus is on the development and commercialization of its drug candidates. The Company has incurred operating losses in each period from inception through December 31, 2017. The Company has been able to fund its cash needs to date through several public and private offerings of its common stock and warrants, through government grants, and through an investment by a strategic purchaser. See Note 11.

Capital Resources

While there can be no assurance, based on currently available information, the Company estimates that it currently has sufficient resources to support its operations for at least the next 12 months.

The Company may raise required funds in the future through public or private equity offerings, debt financings, corporate collaborations, governmental research grants or other means. The Company may also seek to raise new capital to fund additional product development efforts, even if it has sufficient funds for its planned operations. Any sale by the Company of additional equity or convertible debt securities could result in dilution to the Company’s current stockholders. There can be no assurance that any such required additional funding will be available to the Company at all or available on terms acceptable to the Company. Further, to the extent that the Company raises additional funds through collaborative arrangements, it may be necessary to relinquish some rights to the Company’s drug candidates or grant sublicenses on terms that are not favorable to the Company. If the Company is not able to secure additional funding when needed, the Company may have to delay, reduce the scope of, or eliminate one or more research and development programs, which could have an adverse effect on the Company’s business.

Basis of Presentation and Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of Presentation and Significant Accounting Policies

2.	Basis of Presentation and Significant Accounting Policies

PRINCIPLES OF CONSOLIDATION. The consolidated financial statements include the Company’s accounts and those of its wholly-owned subsidiary Catalyst Pharmaceuticals Ireland, Ltd. (“Catalyst Ireland”). All intercompany accounts and transactions have been eliminated in consolidation. Catalyst Ireland was organized in August 2017.

USE OF ESTIMATES. The preparation of financial statements in conformity with U.S. generally accepted accounting principles (U.S. GAAP) requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.

CASH AND CASH EQUIVALENTS. The Company considers all highly liquid instruments, purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist mainly of money market funds. The Company has substantially all of its cash and cash equivalents deposited with one financial institution. These amounts at times may exceed federally insured limits.

SHORT-TERM INVESTMENTS. The Company invests in short-term investments in high credit-quality funds in order to obtain higher yields on its cash available for investments. As of December 31, 2017, and 2016, short-term investments consisted of a short-term bond fund. Such investments are not insured by the Federal Deposit Insurance Corporation. Short-term investments at December 31, 2017 and 2016 were accounted for as trading securities. Trading securities are recorded at fair value based on the closing market price of the security. For trading securities, the Company recognizes realized gains and losses and unrealized gains and losses to earnings. Unrealized gain (loss) on trading securities for the years ended December 31, 2017, 2016 and 2015 were $29,430, $58,861, and ($29,430), respectively, and are included in other income, net in the accompanying consolidated statements of operations.

PREPAID EXPENSES AND OTHER CURRENT ASSETS. Prepaid expenses and other current assets consist primarily of prepaid research fees, prepaid insurance, prepaid pre-commercialization fees and prepaid subscription fees. Prepaid research fees consist of advances for the Company’s product development activities, including drug manufacturing, contracts for preclinical studies, clinical trials and studies, regulatory affairs and consulting. Such advances are recorded as expense as the related goods are received or the related services are performed.

PROPERTY AND EQUIPMENT. Property and equipment are recorded at cost. Depreciation is calculated to amortize the depreciable assets over their useful lives using the straight-line method and commences when the asset is placed in service. Leasehold improvements are amortized on a straight-line basis over the term of the lease or the estimated life of the improvement, whichever is shorter. Useful lives generally range from three years for computer equipment to three to six years for furniture and equipment, and from five to seven years for leasehold improvements. Expenditures for repairs and maintenance are charged to expenses as incurred.

OPERATING LEASES. The Company recognizes lease expense on a straight-line basis over the initial lease term. For leases that contain rent holidays, escalation clauses or tenant improvement allowances, the Company recognizes rent expense on a straight-line basis and records the difference between the rent expense and rental amount payable as deferred rent. As of December 31, 2017, and 2016, the Company had $181,467 and $199,256, respectively, of deferred rent and lease incentive in accrued expenses and other liabilities.

FAIR VALUE OF FINANCIAL INSTRUMENTS. The Company’s financial instruments consist of cash and cash equivalents, short-term investments, accounts payable and accrued expenses and other liabilities, and warrants liability. At December 31, 2017 and 2016, the fair value of these instruments approximated their carrying value.

FAIR VALUE MEASUREMENTS. Current Financial Accounting Standards Board (FASB) fair value guidance emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, current FASB guidance establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity’s own assumptions that it believes market participants would use in pricing assets or liabilities (unobservable inputs classified within Level 3 of the hierarchy).

Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability.


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2017		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	56,820,688	$	56,820,688	$	—	$	—

Short-term investments	$	26,516,711	$	26,516,711	$	—	$	—


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2016		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	13,395,759	$	13,395,759	$	—	$	—

Short-term investments	$	26,512,753	$	26,512,753	$	—	$	—

Warrants liability	$	122,226	$	—	$	—	$	122,226

WARRANTS LIABILITY. In October 2011, the Company issued 1,523,370 warrants (the 2011 warrants) to purchase shares of the Company’s common stock in connection with a registered direct offering. The Company accounted for these warrants as a liability measured at fair value due to a provision included in the warrants agreement that provided the warrants holders with an option to require the Company (or its successor) to purchase their warrants for cash in an amount equal to their Black-Scholes Option Pricing Model (the Black-Scholes Model) value, in the event that certain fundamental transactions, as defined, were to occur while the 2011 warrants were outstanding. During periods that the 2011 warrants were outstanding, the fair value of the warrants liability was estimated using the Black-Scholes Model which required inputs such as the expected term of the warrants, share price volatility and risk-free interest rate. These assumptions were reviewed on a quarterly basis and changes in the estimated fair value of the outstanding warrants were recognized each reporting period in the “Change in fair value of warrants liability” line in the consolidated statements of operations. The 2011 warrants expired on May 2, 2017. At December 31, 2017 and 2016, respectively, none and 763,913 of the 2011 warrants remained outstanding.

RESEARCH AND DEVELOPMENT. Costs incurred in connection with research and development activities are expensed as incurred. These costs consist of direct and indirect costs associated with specific projects as well as fees paid to various entities that perform research related services for the Company.

STOCK-BASED COMPENSATION. The Company recognizes expense in the consolidated statements of operations for the fair value of all stock-based payments to employees, directors, scientific advisors and consultants, including grants of stock options and other share-based awards. For stock options, the Company uses the Black-Scholes option valuation model, the single-option award approach and the straight-line attribution method. Using this approach, compensation cost is amortized on a straight-line basis over the vesting period of each respective stock option, generally one to three years. Forfeitures are recognized as a reduction of share-based compensation expense as they occur.

For the years ended December 31, 2017, 2016 and 2015, the Company recorded stock-based compensation expense as follows:


	2017		2016		2015
Research and development	$	785,899	$	590,857	$	378,548
General and administrative		1,622,062		1,245,228		1,206,910

Total stock-based compensation	$	2,407,961	$	1,836,085	$	1,585,458

CONCENTRATION OF CREDIT RISK. The financial instruments that potentially subject the Company to concentration of credit risk are cash equivalents (i.e. money market funds) and short-term investments. The Company places its cash equivalents with high-credit quality financial institutions. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in these accounts.

INCOME TAXES. The Company utilizes the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized.

The Company recognizes the financial statement benefit of a tax position only after determining that the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more-likely-than-not threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement with the relevant tax authority. The Company is subject to income taxes in the U.S. federal jurisdiction and various state jurisdictions. Tax regulations within each jurisdiction are subject to the interpretation of the related tax laws and regulations and require significant judgment to apply. The Company is not subject to U.S. federal, state and local tax examinations by tax authorities for years before 2014. If the Company were to subsequently record an unrecognized tax benefit, associated penalties and tax related interest expense would be reported as a component of income tax expense.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35 to 21 percent; (2) requiring companies to pay a one-time transition tax on certain repatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) requiring a current inclusion in U.S. federal taxable income earnings of controlled foreign corporations; (5) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (6) creating the base erosion anti-abuse tax (BEAT), a new minimum tax; (7) creating a new limitation on deductible interest expense, and (8) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017.

COMPREHENSIVE INCOME (LOSS). U.S. GAAP require that all components of comprehensive income (loss) be reported in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is net income (loss), plus certain other items that are recorded directly into stockholders’ equity. For all periods presented, the Company’s net loss equals comprehensive loss, since the Company has no items which are considered other comprehensive income (loss).

NET INCOME (LOSS) PER SHARE. Basic loss per share is computed by dividing net loss for the period by the weighted average number of common shares outstanding during the period. The calculation of basic and diluted net loss per share is the same for all periods presented, as the effect of potential common stock equivalents is anti-dilutive due to the Company’s net loss position for all periods presented. The potential shares, which are excluded from the determination of basic and diluted net loss per share as their effect is anti-dilutive, for the years ended December 31, 2017, 2016 and 2015, are as follows:


	2017		2016		2015
Stock options to purchase common stock		5,191,666		4,660,000		4,250,000
Warrants to purchase common stock		—		2,407,663		2,407,663
Unvested restricted stock		—		26,667		53,334

Potential equivalent common stock excluded		5,191,666		7,094,330		6,710,997

Potentially dilutive stock options to purchase common stock as of December 31, 2017, 2016 and 2015 have exercise prices ranging from $0.47 to $4.64. Potentially dilutive warrants to purchase common stock as of December 31, 2016 and 2015 had exercise prices ranging from $1.04 to $2.08 and expired in periods between May 2017 and August 2017.

SEGMENT INFORMATION. Management has determined that the Company operates in one reportable segment, which is the development and commercialization of pharmaceutical products.

RECLASSIFICATIONS. Certain prior year amounts in the consolidated financial statements have been reclassified to conform to the current year presentation.

RECENTLY ISSUED ACCOUNTING STANDARDS. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact this accounting standard will have on its consolidated financial statements.

On March 30, 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which simplifies several aspects of the accounting for employee share-based payment transactions for both public and nonpublic entities, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. For public companies, the changes are effective for reporting periods (annual and interim) beginning after December 15, 2016. The Company adopted this standard in the first quarter of 2017. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 is effective for all entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period, applied prospectively on or after the effective date. The Company is currently evaluating the impact this accounting standard will have on its consolidated financial statements; however, the Company does not expect that the adoption of this standard will have a material impact on the Company’s consolidated financial statements.

Warrants Liability, at Fair Value

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Warrants Liability, at Fair Value

3.	Warrants Liability, at Fair Value

The Company allocated approximately $1.3 million of proceeds from its October 2011 registered direct offering to the fair value of common stock purchase warrants issued in connection with the offering that were classified as a liability (the 2011 warrants). The 2011 warrants were classified as a liability because of provisions in such warrants that allowed for the net cash settlement of such warrants in the event of certain fundamental transactions (as defined in the warrant agreement).

During periods that the 2011 warrants were outstanding, the valuation of the 2011 warrants was determined using the Black-Scholes Model. This model uses inputs such as the underlying price of the shares issued when the warrant is exercised, volatility, risk free interest rate and expected life of the instrument. The Company has determined that the 2011 warrants liability should be classified within Level 3 of the fair value hierarchy by evaluating each input for the Black-Scholes Model against the fair value hierarchy criteria and using the lowest level of input as the basis for the fair value classification. There are six inputs: closing price of the Company’s common stock on the day of evaluation; the exercise price of the warrants; the remaining term of the warrants; the volatility of the Company’s common stock; annual rate of dividends; and the risk-free rate of return. Of those inputs, the exercise price of the warrants and the remaining term are readily observable in the warrants agreement. The annual rate of dividends is based on the Company’s historical practice of not granting dividends. The closing price of the Company’s common stock would fall under Level 1 of the fair value hierarchy as it is a quoted price in an active market. The risk-free rate of return is a Level 2 input, while the historical volatility is a Level 3 input in accordance with the fair value accounting guidance. Since the lowest level input is a Level 3, the Company determined the 2011 warrants liability was most appropriately classified within Level 3 of the fair value hierarchy. This liability was subject to a fair value mark-to-market adjustment each reporting period.

The calculated value of the 2011 warrants liability was determined using the Black-Scholes option-pricing model with the following assumptions:


	December 31, 2016
Risk free interest rate		0.85	%
Expected term		0.33 years
Expected volatility		100	%
Expected dividend yield		0	%
Expected forfeiture rate		0	%

The following table rolls forward the fair value of the Company’s warrants liability activity for the years ended December 31, 2017, 2016 and 2015:


	2017			2016			2015
Fair value, beginning of period	$	122,226		$	1,008,363		$	2,794,891
Issuance of warrants		—			—			—
Exercise of warrants		(309,130	)		—			(1,721,523	)
Change in fair value		186,904			(886,137	)		(65,005	)

Fair value, end of period	$	—		$	122,226		$	1,008,363

During 2017, 613,913 of the 2011 warrants were exercised, with proceeds of $798,087 to the Company. On May 2, 2017, the outstanding and unexercised 2011 warrants expired. During 2016, none of the 2011 warrants were exercised. During 2015, 478,261 of the 2011 warrants were exercised, with proceeds to the Company of $621,739. During periods that the 2011 warrants were outstanding, the Company recognized the change in the fair value of the warrants liability as a non-operating income or loss in the consolidated statements of operations.

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Prepaid Expenses and Other Current Assets

4.	Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following as of December 31:


	2017		2016
Prepaid research fees	$	388,977	$	334,565
Prepaid insurance		638,139		598,909
Prepaid pre-commercialization fees		65,000		35,500
Prepaid subscriptions fees		23,347		22,770
Prepaid rent		—		19,756
Other		58,281		36,444

Total prepaid expenses and other current assets	$	1,173,744	$	1,047,944

Property and Equipment, net

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment, net

5.	Property and Equipment, net

Property and equipment, net consists of the following as of December 31:


	2017			2016
Computer equipment	$	27,915		$	27,915
Furniture and equipment		169,931			177,061
Leasehold improvements		152,708			152,708

		350,554			357,684
Less: Accumulated depreciation		(159,169	)		(113,480	)

Total property and equipment, net	$	191,385		$	244,204

Depreciation expense was $45,689, $43,406, and $34,468, respectively, for the years ended December 31, 2017, 2016 and 2015.

Accrued Expenses and Other Liabilities

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Accrued Expenses and Other Liabilities

6.	Accrued Expenses and Other Liabilities

Accrued expenses and other liabilities consist of the following as of December 31:


	2017		2016
Accrued preclinical and clinical trial expenses	$	970,649	$	623,855
Accrued professional fees		227,457		102,673
Accrued compensation and benefits		821,935		264,237
Accrued license fees		252,500		152,500
Deferred rent and lease incentive		24,011		18,094
Other		24,035		—

Current accrued expenses and other liabilities		2,320,587		1,161,359
Deferred rent and lease incentive—non-current		157,456		181,162

Non-current accrued expenses and other liabilities		157,456		181,162

Total accrued expenses and other liabilities	$	2,478,043	$	1,342,521

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

7.	Commitments and Contingencies

The Company has contracted with drug manufacturers and other vendors, including clinical research organizations (CRO) overseeing the clinical trials of the Company’s drug candidates, to assist in the execution of the Company’s preclinical and clinical trials, analysis, and the preparation of material necessary for the submission of new drug applications (NDAs) and abbreviated new drug applications (ANDAs) with the U.S. Food and Drug Administration (FDA). The contracts are cancelable at any time, but obligate the Company to reimburse the providers for any time or costs incurred through the date of termination.

The Company has executed a non-cancellable operating lease agreement for its corporate office. The lease has free and escalating rent payment provisions. The Company recognizes rent expense under such lease on a straight-line basis over the term of the lease. As of December 31, 2017, future minimum lease payments under the operating lease agreement are as follows:


2018	$	213,644
2019		220,053
2020		226,655
2021		233,454
2022		220,023

	$	1,113,829

In March 2015, the Company amended the lease to its corporate offices to obtain additional space for its operations. The Company now leases approximately 5,200 square feet and the lease term now expires in 2022. In connection with the expansion, approximately $131,000 of tenant build-out costs were funded and paid by the landlord through lease incentives. The lease incentives are being amortized over the term of the lease as a reduction of rent expense. The lease provides for fixed increases in minimum annual rent payments, as well as rent free periods. The total amount of rental payments due over the lease term is being charged to rent expense on the straight-line method over the term of the lease. The differences between rent expense recorded and the amount paid is credited or charged to accrued expenses and other liabilities in the accompanying consolidated balance sheets. Rent expense was $204,170, $201,920, and $129,727 respectively, for the years ended December 31, 2017, 2016 and 2015.

There are no obligations under capital leases.

For commitments related to the Company’s license agreements with BioMarin (defined below) and Northwestern (defined below), see Note 8.

Agreements

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Agreements

8.	Agreements

LICENSE AGREEMENT WITH NORTHWESTERN UNIVERSITY. On August 27, 2009, the Company entered into a license agreement with Northwestern University (Northwestern), under which it acquired worldwide rights to commercialize new GABA aminotransferase inhibitors and derivatives of vigabatrin that have been discovered by Northwestern. Under the terms of the license agreement, Northwestern granted the Company an exclusive worldwide license to certain composition of matter patents related to the new class of inhibitors and a patent application relating to derivatives of vigabatrin. The Company has identified and designated the lead compound under this license as CPP-115.

Under the license agreement with Northwestern, the Company is responsible for continued research and development of any resulting product candidates. As of December 31, 2017, the Company has paid $424,885 in connection with the license and has accrued license fees of $252,500 and $152,500 as of December 31, 2017, and 2016, respectively, in the accompanying consolidated balance sheets for expenses, maintenance fees and milestones. In addition, the Company is obligated to pay certain milestone payments in future years relating to clinical development activities with respect to CPP-115, and royalties on any products resulting from the license agreement. The next milestone payment of $300,000 is due on the earlier of successful completion of the first Phase 3 clinical trial for CPP-115 or August 27, 2018.

LICENSE AGREEMENT WITH NEW YORK UNIVERSITY AND THE FEINSTEIN INSTITUTE FOR MEDICAL RESEARCH. On December 13, 2011, the Company entered into a license agreement with New York University (NYU) and the Feinstein Institute for Medical Research (FIMR) under which it acquired worldwide rights to commercialize GABA aminotransferase inhibitors in the treatment for Tourette syndrome. The Company is obligated to pay certain milestone payments in future years relating to clinical development activities and royalties on any products resulting from the license agreement.

LICENSE AGREEMENT WITH BIOMARIN. On October 26, 2012, the Company entered into a license agreement with BioMarin Pharmaceutical, Inc. (BioMarin) for the North American rights to Firdapse^®.

Under the License Agreement, the Company has agreed to pay: (i) royalties to BioMarin for seven years from the first commercial sale of Firdapse^® equal to 7% of net sales (as defined in the license agreement) in North America for any calendar year for sales up to $100 million, and 10% of net sales in North America in any calendar year in excess of $100 million; and (ii) royalties to the third-party licensor of the rights sublicensed to the Company for seven years from the first commercial sale of Firdapse^® equal to 7% of net sales (as defined in the license agreement between BioMarin and the third-party licensor) in any calendar year.

Under the Company’s license agreement with BioMarin, the Company has agreed to pay certain milestone payments that BioMarin is obligated to pay to both a third-party licensor of the rights that have been sublicensed to the Company and to the former stockholders of Huxley Pharmaceuticals (“Huxley”) under an earlier stock purchase agreement between BioMarin and the former Huxley stockholders. These milestones aggregate (i) approximately $2.6 million due upon acceptance by the FDA of a filing of an NDA for Firdapse^® for the treatment of LEMS or CMS (approximately $150,000 of which will be due to the third party licensor and approximately $2,425,000 of which will be due to the former Huxley stockholders), and (ii) approximately $7.2 million due upon the unconditional approval by the FDA of an NDA for Firdapse^® for the treatment of LEMS (approximately $3.0 million of which will be due to the third party licensor and approximately $4.2 million of which will be due to the former Huxley stockholders). However, under BioMarin’s agreement with the former Huxley stockholders (and under the Company’s license agreement with BioMarin), BioMarin’s obligation to pay the milestone payments due to the former Huxley stockholders (and the Company’s corresponding obligation to pay such milestone payments) expressly expires if these milestones have not been not satisfied by April 20, 2018.

BioMarin has recently advised the Company that the former Huxley stockholders may take legal action seeking payment of the milestone payments due to them from BioMarin if these milestones are achieved after April 20, 2018, notwithstanding the express termination date in the agreements. BioMarin has also advised the Company that the Company could become involved in any such legal action. While it is too early to determine how this matter will affect the Company, based on currently available information the Company does not believe that this matter will have a material adverse effect on the Company’s financial position or results of operations.

The Company also agreed to share in the cost of certain post-marketing studies conducted by BioMarin, and, as of both December 31, 2017, and 2016, the Company had paid BioMarin $3.8 million in the aggregate, related to expenses in connection with Firdapse^® studies and trials.

AGREEMENTS FOR DRUG DEVELOPMENT, PRECLINICAL AND CLINICAL STUDIES. The Company has entered into agreements with contract manufacturers for the manufacture of drug and study placebo for the Company’s trials and studies, and for commercial requirements if any product is approved for commercialization, with contract research organizations (CRO) to conduct and monitor the Company’s trials and studies and with various entities for laboratories and other testing related to the Company’s trials and studies. The contractual terms of the agreements vary, but most require certain advances as well as payments based on the achievement of milestones. Further, these agreements are cancellable at any time, but obligate the Company to reimburse the providers for any time or costs incurred through the date of termination.

Related Party Transactions

12 Months Ended

Dec. 31, 2017

Related Party Transactions

9.	Related Party Transactions

During each of the years ended December 31, 2017, 2016 and 2015, the Company paid approximately $10,000, in consulting fees to members of the Company’s Scientific Advisory Board.

During 2015, the Company entered into a consulting agreement with one of its directors to serve as interim chief commercial officer during a period that the Company was seeking to fill that position. The consulting arrangement ended in September 2015 and the director received a total of $45,000 in consulting fees for those services.

The Company has an employment agreement with its Chief Executive Officer. Under this agreement, the CEO will receive an annual base salary of approximately $525,000 in 2018. This agreement expires in November 2018.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

10.

Income Taxes

Due to the ongoing operating losses and the inability to recognize any income tax benefit, there is no provision for income taxes in any period presented in these financial statements. Since inception, the Company has only generated pretax losses.

The reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 34% to amounts included in the consolidated statements of operations is as follows:


	2017			2016			2015
Statutory rate		34.0	%		34.0	%		34.0	%
State tax		3.5	%		3.4	%		3.6	%
Valuation allowance		26.5	%		(44.7	)%		(37.7	)%
Federal rate change		(73.2	)%		0.0	%		0.0	%
Tax credit		6.8	%		6.2	%		0.0	%
Other		2.4	%		1.1	%		0.1	%

		0.0	%		0.0	%		0.0	%

Deferred tax assets and liabilities reflect the net tax effects of net operating loss and tax credit carryovers and the temporary differences between the carrying amounts of assets and liabilities for financial reporting and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets as of December 31, 2017 and 2016 are as follows:


	2017			2016
Net operating loss	$	15,718,570		$	21,050,217
Start-up cost		10,508,487			12,823,113
Tax credits		11,582,134			6,960,838
Deferred compensation		1,326,189			1,555,425
Other		72,395			207,133

Gross deferred tax asset		39,207,775			42,596,726
Valuation allowance		(39,207,775	)		(42,596,726	)

Net deferred tax assets	$	0		$	0

The Company’s deferred tax assets have been fully offset by a valuation allowance at December 31, 2017 and 2016 because the Company believes that it is more likely than not that the deferred tax asset will not be realized. The decrease and increase in the valuation allowance on the deferred tax assets was $3,388,951 and $8,287,962 for the years ended December 31, 2017 and 2016, respectively.

Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in years in which those temporary differences are expected to be recovered or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through income tax expense. As a result of the reduction in the U.S. corporate tax rate from 35% to 21% under the Tax Act enacted in December 2017, the Company recorded a reduction of approximately $13.5 million in the fourth quarter of 2017 related to the revaluation of its deferred tax assets. There was no impact to tax expense as a result of the revaluation as the Company’s deferred tax assets have a full valuation allowance.

At December 31, 2017 and 2016, respectively, the Company had net operating loss carryforwards of approximately $62.6 million and $56.3 million available to reduce future taxable income, if any. The net operating loss carryforwards will expire at various dates beginning in 2024 and ending in 2037. If an ownership change, as defined under Internal Revenue Code Section 382, occurs, the use of these carry-forwards may be subject to limitation. The effective tax rate of 0% in all periods presented differs from the statutory rate of 34% due to the valuation allowance and because the Company had no taxable income.

Beginning in 2010, the Company has received several orphan drug designations by the FDA for products currently under development. The orphan drug designations allow the Company to claim increased federal tax credits for certain research and development activities.

No interest or penalties were accrued through December 31, 2017. The Company’s policy is to recognize any related interest or penalties in income tax expense. The Company is not subject to U.S federal, state and local tax examinations by tax authorities for any years before 2014. The Company is not currently under income tax examinations by any tax authorities.

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Stockholders' Equity

11.

Stockholders’ Equity

Preferred Stock

The Company has 5,000,000 shares of authorized preferred stock, $0.001 par value per share at December 31, 2017 and 2016. No shares of preferred stock were outstanding at December 31, 2017 and 2016.

Common Stock

During 2015, the Company’s stockholders approved an increase in the Company’s authorized common stock par value $0.001 per share, from 100,000,000 shares to 150,000,000 shares. At December 31, 2017 and 2016, 102,549,498 and 82,972,316 shares, respectively, of common stock were issued and outstanding. Each holder of common stock is entitled to one vote of each share of common stock held of record on all matters on which stockholders generally are entitled to vote.

2016 Shelf Registration Statement

On December 23, 2016, the Company filed a shelf Registration Statement on Form S-3 (the 2016 Shelf Registration Statement) with the SEC to sell up to approximately $33.8 million of common stock. The 2016 Shelf Registration Statement (file No. 333-215315) was declared effective by the SEC on January 9, 2017. No sales have been conducted to date under the 2016 Shelf Registration Statement.

2017 Shelf Registration Statement

On July 12, 2017, the Company filed a universal shelf Registration Statement on Form S-3 (the 2017 Shelf Registration Statement) with the SEC to sell up to $150 million of common stock, preferred stock, warrants to purchase common stock, or debt securities (including debt securities that may be convertible or exchangeable for common stock or other securities), which securities may be offered separately or together in units or multiple series. The 2017 Shelf Registration Statement (file No. 333-219259) was declared effective by the SEC on July 26, 2017. The Company has to date conducted the following sales of its securities under the 2017 Shelf Registration Statement:

(a)

On November 28, 2017, the Company filed a prospectus supplement and offered for sale 16,428,572 shares if its common stock at a price of $3.50 per share in an underwritten public offering. The Company received gross proceeds in the public offering of approximately $57.5 million before underwriting commission and incurred expenses of approximately $3.7 million.

As of December 31, 2017, there is approximately $92.5 million available for future sale under the 2017 Shelf Registration Statement.

Warrant Exercises

For the year ended December 31, 2017, the Company issued 2,257,663 of its authorized but unissued common stock upon the exercise of previously issued common stock purchase warrants, with net proceeds to the Company of $3,209,423. No warrants were exercised during the year ended December 31, 2016. For the year ended December 31, 2015, the Company issued an aggregate of 1,178,261 shares of its authorized but unissued common stock upon the exercise of previously issued common stock purchase warrants, raising net proceeds of $1,895,738.

Stockholder Rights Plan

On September 20, 2011, the Board of Directors approved the Company’s adoption of a Stockholder Rights Plan. Under the Plan, a dividend of one preferred share purchase right (a Right) was declared for each share of common stock of the Company that was outstanding on October 7, 2011. Each Right entitles the holder to purchase from the Company one one-hundredth of a share of Series A Junior Preferred Stock at a purchase price of $7.80, subject to adjustment.

The Rights trade automatically with the common stock and will not be exercisable until a person or group has become an “acquiring person” by acquiring 17.5% or more of the Company’s outstanding common stock, or a person or group commences, or publicly announces a tender offer that will result in such a person or group owning 17.5% or more of the Company’s outstanding common stock. Upon announcement that any person or group has become an acquiring person, each Right will entitle all rightholders (other than the acquiring person) to purchase, for the exercise price of $7.80, a number of shares of the Company’s common stock having a market value equal to twice the exercise price. Rightholders would also be entitled to purchase common stock of the acquiring person having a value of twice the exercise price if, after a person had become an acquiring person, the Company were to enter into certain mergers or other transactions. If any person becomes an acquiring person, the Board of Directors may, at its option and subject to certain limitations, exchange one share of common stock for each Right.

The Rights have certain anti-takeover effects, in that they would cause substantial dilution to a person or group that attempts to acquire a significant interest in the Company on terms not approved by the Board of Directors. In the event that the Board of Directors determines a transaction to be in the best interests of the Company and its stockholders, the Board of Directors may redeem the Rights for $0.001 per share at any time prior to a person or group becoming an acquiring person.

On September 19, 2016, the Board of Directors unanimously approved, and on the same date the Company entered into Amendment No. 1 to the Stockholder Rights Plan (the “Amendment”). Under the terms of the Amendment, the outside expiration date of the rights plan has been extended from September 20, 2016 to September 20, 2019. Additionally, as part of the Amendment, the Board adopted a Certificate of Designation, Preferences and Rights of Series A Junior Participating Preferred Stock of the Company to increase the number of shares of Series A Junior Participating Preferred Stock of the Company available for issuance under the Rights Plan from 500,000 shares to 1.5 million shares.

At the Company’s 2017 annual meeting of stockholders, the Company’s stockholders approved the stockholder rights plan, as amended.

Stock Compensation Plans

12 Months Ended

Dec. 31, 2017

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

Stock Compensation Plans

12.

Stock Compensation Plans

Stock Options

The Company may issue stock options, restricted stock, stock appreciation rights and restricted stock units (collectively, the “Awards”) to employees, directors, consultants and scientific advisors of the Company under the 2006 and 2014 Stock Incentive Plans (the 2006 Plan and the 2014 Plan or collectively, the Plans). At December 31, 2017, no shares remain available for future issuance under the 2006 Plan. Under the 2014 Plan, 9,000,000 shares were reserved for issuance and as of December 31, 2017, 3,646,668 shares remain available for future issuance.

The Company has granted stock options to employees, officers, directors, scientific advisors and consultants generally at exercise prices equal to the market price of the common stock at grant date. Option awards generally vest over a period of 1 to 3 years of continuous service and have contractual terms from 5 to 7 years. Certain awards provide for accelerated vesting if there is a change in control. The Company issues new shares as shares are required to be delivered upon exercise of outstanding stock options.

During the years ended December 31, 2017, 2016, and 2015, options to purchase 780,000, 75,000, and 265,000 shares of the Company’s common stock were exercised with gross proceeds to the Company of $368,185, $80,251, and $390,351, respectively. Further, during the years ended December 31, 2017, 2016, and 2015, options to purchase 100,000, 50,000, and 984,608 shares of the Company’s common stock were exercised on a “cashless” basis, resulting in the issuance of an aggregate of 84,280, 20,030, and 761,600 shares of the Company’s common stock, respectively.

During the years ended December 31, 2017, 2016 and 2015 the Company recorded non-cash stock-based compensation expense related to stock options totaling $2,342,625, $1,760,591, and $1,510,018, respectively.

During the years ended December 31, 2017, 2016 and 2015, the Company granted seven-year options to purchase an aggregate of 1,550,000, 1,285,000 and 1,760,000 shares, respectively, of the Company’s common stock to certain of the Company’s officers, employees, directors, and consultants.

Stock option activity under the Company’s Plans for the year ended December 31, 2017 is summarized as follows:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year		4,660,000		$	1.94
Granted		1,550,000			1.17
Exercised		(880,000	)		0.47
Forfeited or cancelled		(138,334	)		1.94
Expired		—			0.00

Outstanding at end of year		5,191,666		$	1.96		4.94	$	10,178,881

Exercisable at end of year		2,908,330		$	2.44		4.40	$	4,334,327

Other information pertaining to stock option activity during the years ended December 31, 2017, 2016 and 2015 was as follows:


	2017		2016		2015
Weighted–average fair value of granted stock options	$	0.91	$	0.62	$	2.13
Total fair value of vested stock options	$	2,016,992	$	1,634,562	$	1,307,895
Total intrinsic value of exercised stock options	$	2,296,100	$	42,000	$	3,311,599

The following table summarizes information about the Company’s options outstanding at December 31, 2017:


	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price
$0.47 to $0.85		1,085,000		5.15	$	0.78		550,000		5.09	$	0.79
$0.86 to $1.14		1,516,666		6.00	$	1.13		199,999		5.99	$	1.13
$1.15 to $2.80		1,195,000		4.75	$	2.48		866,665		4.65	$	2.51
$2.81 to $3.23		1,020,000		3.67	$	3.12		1,020,000		3.67	$	3.12
$3.24 to $4.64		375,000		4.06	$	3.93		271,666		3.81	$	3.94

		5,191,666		4.94	$	1.96		2,908,330		4.40	$	2.44

As of December 31, 2017, there was approximately $1,367,155 of unrecognized compensation expense related to non-vested stock option awards granted under the Plans. That cost is expected to be recognized over a weighted average period of approximately 1.39 years.

The Company utilizes the Black-Scholes option-pricing model to determine the fair value of stock options on the date of grant. This model derives the fair value of stock options based on certain assumptions related to the expected stock price volatility, expected option life, risk-free interest rate and dividend yield. Expected volatility is based on reviews of historical volatility of the Company’s common stock. The estimated expected option life is based upon estimated employee exercise patterns and considers whether and the extent to which the options are in-the-money. The Company estimates the expected option life for options granted to employees and directors based upon the simplified method. Under this method, the expected life is presumed to be the mid-point between the vesting date and the end of the contractual term. The Company will continue to use the simplified method until it has sufficient historical exercise data to estimate the expected life of the options. The risk-free interest rate assumption is based upon the U.S. Treasury yield curve appropriate for the estimated life of the stock options awards. The expected dividend rate is zero. Stock–based compensation expense also includes an estimate, which the Company makes at grant date, of the number of awards that are expected to be forfeited. The Company revises this estimate in subsequent periods if actual forfeitures differ from those estimates.

Assumptions used during the years were as follows:


	Year ended December 31,
	2017			2016			2015
Risk free interest rate		1.66% to 2.25	%		0.76% to 2.15	%		1.00% to 2.13	%
Expected term		4 to 7 years			2 to 6 years			3 to 7 years
Expected volatility		104	%		100	%		102	%
Expected dividend yield		—	%		—	%		—	%
Expected forfeiture rate		—	%		—	%		—	%

Restricted Stock Units

Under the 2014 Plan, participants may be granted restricted stock units, each of which represents a conditional right to receive shares of common stock in the future. The restricted stock units granted under this plan generally vest ratably over a three to four-year period. Upon vesting, the restricted stock units will convert into an equivalent number of shares of common stock. The amount of expense relating to the restricted stock units is based on the closing market price of the Company’s common stock on the date of grant and is amortized on a straight-line basis over the requisite service period. Restricted stock unit activity during 2017, 2016, and 2015 was as follows:


	2017					2016					2015
	Number of Restricted Stock Units			Weighted Average Grant Date Fair Value		Number of Restricted Stock Units			Weighted Average Grant Date Fair Value		Number of Restricted Stock Units			Weighted Average Grant Date Fair Value
Nonvested balance at beginning of year		26,667		$	2.83		53,334		$	2.83		80,000		$	2.83
Granted		—			—		—			—		—			—
Vested		(26,667	)		2.83		(26,667	)		2.83		(26,666	)		2.83
Forfeited		—			—		—			—		—			—

Nonvested balance at end of year	$	—		$	—		26,667		$	2.83		53,334		$	2.83

During the years ended December 31, 2017, 2016 and 2015, the Company recorded non-cash stock-based compensation expense related to restricted stock units totaling $65,336, $75,494, and $75,440, respectively.

Quarterly Financial Information (unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information (unaudited)

14.

Quarterly Financial Information (unaudited)

The following table presents unaudited supplemental quarterly financial information for the years ended December 31, 2017 and 2016:


	Quarter Ended
	March 31, 2017			June 30, 2017			September 30, 2017			December 31, 2017
Revenues	$	—		$	—		$	—		$	—
Loss from operations		(4,679,871	)		(4,181,271	)		(4,306,708	)		(5,511,786	)
Change in fair value of warrants liability		(397,235	)		210,331			—			—
Net loss	$	(4,967,129	)	$	(3,879,901	)	$	(4,177,649	)	$	(5,387,698	)
Net loss per share—basic and diluted	$	(0.06	)	$	(0.05	)	$	(0.05	)	$	(0.06	)


	Quarter Ended
	March 31, 2016			June 30, 2016			September 30, 2016			December 31, 2016
Revenues	$	—		$	—		$	—		$	—
Loss from operations		(6,237,536	)		(4,814,452	)		(3,914,014	)		(4,314,199	)
Change in fair value of warrants liability		733,356			152,783			(106,948	)		106,946
Net loss	$	(5,386,237	)	$	(4,568,914	)	$	(3,953,981	)	$	(4,163,320	)
Net loss per share—basic and diluted	$	(0.07	)	$	(0.06	)	$	(0.05	)	$	(0.05	)

Quarterly basic and diluted net loss per common share were computed independently for each quarter and do not necessarily total to the full year basic and diluted net loss per common share.

Basis of Presentation and Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

PRINCIPLES OF CONSOLIDATION

USE OF ESTIMATES

CASH AND CASH EQUIVALENTS

SHORT-TERM INVESTMENTS

PREPAID EXPENSES AND OTHER CURRENT ASSETS

PROPERTY AND EQUIPMENT

OPERATING LEASES

FAIR VALUE OF FINANCIAL INSTRUMENTS

FAIR VALUE MEASUREMENTS


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2017		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	56,820,688	$	56,820,688	$	—	$	—

Short-term investments	$	26,516,711	$	26,516,711	$	—	$	—


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2016		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	13,395,759	$	13,395,759	$	—	$	—

Short-term investments	$	26,512,753	$	26,512,753	$	—	$	—

Warrants liability	$	122,226	$	—	$	—	$	122,226

WARRANTS LIABILITY

RESEARCH AND DEVELOPMENT

STOCK-BASED COMPENSATION

For the years ended December 31, 2017, 2016 and 2015, the Company recorded stock-based compensation expense as follows:


	2017		2016		2015
Research and development	$	785,899	$	590,857	$	378,548
General and administrative		1,622,062		1,245,228		1,206,910

Total stock-based compensation	$	2,407,961	$	1,836,085	$	1,585,458

CONCENTRATION OF CREDIT RISK

INCOME TAXES

COMPREHENSIVE INCOME (LOSS)

NET INCOME (LOSS) PER SHARE


	2017		2016		2015
Stock options to purchase common stock		5,191,666		4,660,000		4,250,000
Warrants to purchase common stock		—		2,407,663		2,407,663
Unvested restricted stock		—		26,667		53,334

Potential equivalent common stock excluded		5,191,666		7,094,330		6,710,997

SEGMENT INFORMATION

q.	SEGMENT INFORMATION. Management has determined that the Company operates in one reportable segment, which is the development and commercialization of pharmaceutical products.

RECLASSIFICATIONS

r.	RECLASSIFICATIONS. Certain prior year amounts in the consolidated financial statements have been reclassified to conform to the current year presentation.

RECENTLY ISSUED ACCOUNTING STANDARDS

Basis of Presentation and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Fair Value Measurement Specific to Assets or Liability

The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability.


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2017		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	56,820,688	$	56,820,688	$	—	$	—

Short-term investments	$	26,516,711	$	26,516,711	$	—	$	—


			Fair Value Measurements at Reporting Date Using
	Balances as of December 31, 2016		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	13,395,759	$	13,395,759	$	—	$	—

Short-term investments	$	26,512,753	$	26,512,753	$	—	$	—

Warrants liability	$	122,226	$	—	$	—	$	122,226

Stock-Based Compensation Expense

For the years ended December 31, 2017, 2016 and 2015, the Company recorded stock-based compensation expense as follows:


	2017		2016		2015
Research and development	$	785,899	$	590,857	$	378,548
General and administrative		1,622,062		1,245,228		1,206,910

Total stock-based compensation	$	2,407,961	$	1,836,085	$	1,585,458

Potential Shares Excluded from Determination of Basic and Diluted Net Loss Per Share

The potential shares, which are excluded from the determination of basic and diluted net loss per share as their effect is anti-dilutive, for the years ended December 31, 2017, 2016 and 2015, are as follows:


	2017		2016		2015
Stock options to purchase common stock		5,191,666		4,660,000		4,250,000
Warrants to purchase common stock		—		2,407,663		2,407,663
Unvested restricted stock		—		26,667		53,334

Potential equivalent common stock excluded		5,191,666		7,094,330		6,710,997

Warrants Liability, at Fair Value (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Company's Warrants Liability Activity

The following table rolls forward the fair value of the Company’s warrants liability activity for the years ended December 31, 2017, 2016 and 2015:


	2017			2016			2015
Fair value, beginning of period	$	122,226		$	1,008,363		$	2,794,891
Issuance of warrants		—			—			—
Exercise of warrants		(309,130	)		—			(1,721,523	)
Change in fair value		186,904			(886,137	)		(65,005	)

Fair value, end of period	$	—		$	122,226		$	1,008,363

Warrants Liability, at Fair Value [Member]

Summary of Assumptions Used in Black-Scholes Model to Calculate Fair Value of Warrants Liability

The calculated value of the 2011 warrants liability was determined using the Black-Scholes option-pricing model with the following assumptions:


	December 31, 2016
Risk free interest rate		0.85	%
Expected term		0.33 years
Expected volatility		100	%
Expected dividend yield		0	%
Expected forfeiture rate		0	%

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following as of December 31:


	2017		2016
Prepaid research fees	$	388,977	$	334,565
Prepaid insurance		638,139		598,909
Prepaid pre-commercialization fees		65,000		35,500
Prepaid subscriptions fees		23,347		22,770
Prepaid rent		—		19,756
Other		58,281		36,444

Total prepaid expenses and other current assets	$	1,173,744	$	1,047,944

Property and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment, net

Property and equipment, net consists of the following as of December 31:


	2017			2016
Computer equipment	$	27,915		$	27,915
Furniture and equipment		169,931			177,061
Leasehold improvements		152,708			152,708

		350,554			357,684
Less: Accumulated depreciation		(159,169	)		(113,480	)

Total property and equipment, net	$	191,385		$	244,204

Accrued Expenses and Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Liabilities

Accrued expenses and other liabilities consist of the following as of December 31:


	2017		2016
Accrued preclinical and clinical trial expenses	$	970,649	$	623,855
Accrued professional fees		227,457		102,673
Accrued compensation and benefits		821,935		264,237
Accrued license fees		252,500		152,500
Deferred rent and lease incentive		24,011		18,094
Other		24,035		—

Current accrued expenses and other liabilities		2,320,587		1,161,359
Deferred rent and lease incentive—non-current		157,456		181,162

Non-current accrued expenses and other liabilities		157,456		181,162

Total accrued expenses and other liabilities	$	2,478,043	$	1,342,521

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Future Minimum Lease Payments under Operating Lease Agreement

As of December 31, 2017, future minimum lease payments under the operating lease agreement are as follows:


2018	$	213,644
2019		220,053
2020		226,655
2021		233,454
2022		220,023

	$	1,113,829

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Reconciliation of Income Tax Expense (Benefit) Computed at Statutory Federal Income Tax Rate

The reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 34% to amounts included in the consolidated statements of operations is as follows:


	2017			2016			2015
Statutory rate		34.0	%		34.0	%		34.0	%
State tax		3.5	%		3.4	%		3.6	%
Valuation allowance		26.5	%		(44.7	)%		(37.7	)%
Federal rate change		(73.2	)%		0.0	%		0.0	%
Tax credit		6.8	%		6.2	%		0.0	%
Other		2.4	%		1.1	%		0.1	%

		0.0	%		0.0	%		0.0	%

Components of Deferred Tax Assets

Significant components of the Company’s deferred tax assets as of December 31, 2017 and 2016 are as follows:


	2017			2016
Net operating loss	$	15,718,570		$	21,050,217
Start-up cost		10,508,487			12,823,113
Tax credits		11,582,134			6,960,838
Deferred compensation		1,326,189			1,555,425
Other		72,395			207,133

Gross deferred tax asset		39,207,775			42,596,726
Valuation allowance		(39,207,775	)		(42,596,726	)

Net deferred tax assets	$	0		$	0

Stock Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

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

Stock option activity under the Company's Plans

Stock option activity under the Company’s Plans for the year ended December 31, 2017 is summarized as follows:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year		4,660,000		$	1.94
Granted		1,550,000			1.17
Exercised		(880,000	)		0.47
Forfeited or cancelled		(138,334	)		1.94
Expired		—			0.00

Outstanding at end of year		5,191,666		$	1.96		4.94	$	10,178,881

Exercisable at end of year		2,908,330		$	2.44		4.40	$	4,334,327

Schedule of Other Information Pertaining to Stock Option Activity

Other information pertaining to stock option activity during the years ended December 31, 2017, 2016 and 2015 was as follows:


	2017		2016		2015
Weighted–average fair value of granted stock options	$	0.91	$	0.62	$	2.13
Total fair value of vested stock options	$	2,016,992	$	1,634,562	$	1,307,895
Total intrinsic value of exercised stock options	$	2,296,100	$	42,000	$	3,311,599

Summary of Company's Stock Options Outstanding

The following table summarizes information about the Company’s options outstanding at December 31, 2017:


	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price
$0.47 to $0.85		1,085,000		5.15	$	0.78		550,000		5.09	$	0.79
$0.86 to $1.14		1,516,666		6.00	$	1.13		199,999		5.99	$	1.13
$1.15 to $2.80		1,195,000		4.75	$	2.48		866,665		4.65	$	2.51
$2.81 to $3.23		1,020,000		3.67	$	3.12		1,020,000		3.67	$	3.12
$3.24 to $4.64		375,000		4.06	$	3.93		271,666		3.81	$	3.94

		5,191,666		4.94	$	1.96		2,908,330		4.40	$	2.44

Summary of Stock Options Awards Based on Certain Assumptions

Assumptions used during the years were as follows:


	Year ended December 31,
	2017			2016			2015
Risk free interest rate		1.66% to 2.25	%		0.76% to 2.15	%		1.00% to 2.13	%
Expected term		4 to 7 years			2 to 6 years			3 to 7 years
Expected volatility		104	%		100	%		102	%
Expected dividend yield		—	%		—	%		—	%
Expected forfeiture rate		—	%		—	%		—	%

Summary of Restricted Stock Unit Activity

Restricted stock unit activity during 2017, 2016, and 2015 was as follows:


	2017					2016					2015
	Number of Restricted Stock Units			Weighted Average Grant Date Fair Value		Number of Restricted Stock Units			Weighted Average Grant Date Fair Value		Number of Restricted Stock Units			Weighted Average Grant Date Fair Value
Nonvested balance at beginning of year		26,667		$	2.83		53,334		$	2.83		80,000		$	2.83
Granted		—			—		—			—		—			—
Vested		(26,667	)		2.83		(26,667	)		2.83		(26,666	)		2.83
Forfeited		—			—		—			—		—			—

Nonvested balance at end of year	$	—		$	—		26,667		$	2.83		53,334		$	2.83

Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The following table presents unaudited supplemental quarterly financial information for the years ended December 31, 2017 and 2016:


	Quarter Ended
	March 31, 2017			June 30, 2017			September 30, 2017			December 31, 2017
Revenues	$	—		$	—		$	—		$	—
Loss from operations		(4,679,871	)		(4,181,271	)		(4,306,708	)		(5,511,786	)
Change in fair value of warrants liability		(397,235	)		210,331			—			—
Net loss	$	(4,967,129	)	$	(3,879,901	)	$	(4,177,649	)	$	(5,387,698	)
Net loss per share—basic and diluted	$	(0.06	)	$	(0.05	)	$	(0.05	)	$	(0.06	)


	Quarter Ended
	March 31, 2016			June 30, 2016			September 30, 2016			December 31, 2016
Revenues	$	—		$	—		$	—		$	—
Loss from operations		(6,237,536	)		(4,814,452	)		(3,914,014	)		(4,314,199	)
Change in fair value of warrants liability		733,356			152,783			(106,948	)		106,946
Net loss	$	(5,386,237	)	$	(4,568,914	)	$	(3,953,981	)	$	(4,163,320	)
Net loss per share—basic and diluted	$	(0.07	)	$	(0.06	)	$	(0.05	)	$	(0.05	)

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Oct. 31, 2011 shares	Dec. 31, 2018	Dec. 31, 2017 USD ($) Segment $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Maximum maturity period of cash and cash equivalent			Three months
Deferred rent and lease incentive in accrued expenses and other liabilities \| $			$ 181,467	$ 199,256
Statutory rate			34.00%	34.00%	34.00%
Stock option exercise price range, Minimum			$ 0.47	$ 0.47	$ 0.47
Stock option exercise price range, Maximum			$ 4.64	$ 4.64	$ 4.64
Number of reportable segment \| Segment			1
October 28, 2011 Warrants [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Warrants issued in offering \| shares	1,523,370
Warrants outstanding \| shares			0	763,913
October 28, 2011 Warrants [Member] \| Warrants Liability, at Fair Value [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Warrants expiration date			May 02, 2017
Trading Securities [Member] \| Other Income, Net [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Unrealized gain (loss) \| $			$ 29,430	$ 58,861	$ (29,430)
Scenario, Plan [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Statutory rate		21.00%
U.S. federal corporate tax rate [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Statutory rate			35.00%
Computer Equipment [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets			3 years
Minimum [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Minimum amortization period of compensation cost on straight line basis			1 year
Potentially dilutive warrants to purchase common stock				$ 1.04	$ 1.04
Minimum [Member] \| Leasehold Improvements [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets			5 years
Minimum [Member] \| Furniture and Equipment [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets			3 years
Maximum [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Minimum amortization period of compensation cost on straight line basis			3 years
Potentially dilutive warrants to purchase common stock				$ 2.08	$ 2.08
Maximum [Member] \| Leasehold Improvements [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets			7 years
Maximum [Member] \| Furniture and Equipment [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets			6 years

Basis of Presentation and Significant Accounting Policies - Fair Value Measurement Specific to Assets or Liability (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 26,516,711	$ 26,512,753
Warrants liability		122,226
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	56,820,688	13,395,759
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26,516,711	26,512,753
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 56,820,688	13,395,759
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants liability		$ 122,226

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References + Details

Basis of Presentation and Significant Accounting Policies - Stock-Based Compensation Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 2,407,961	$ 1,836,085	$ 1,585,458
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	785,899	590,857	378,548
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,622,062	$ 1,245,228	$ 1,206,910

Basis of Presentation and Significant Accounting Policies - Potential Shares Excluded from Determination of Basic and Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	5,191,666	7,094,330	6,710,997
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	5,191,666	4,660,000	4,250,000
Warrants Liability, at Fair Value [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded		2,407,663	2,407,663
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded		26,667	53,334

Warrants Liability, at Fair Value - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Recognition of warrants fair value at date of issuance		$ 0	$ 0	$ 0
Number of warrants exercised during the period		2,257,663	0	1,178,261
Proceeds of Warrants		$ 3,209,423		$ 1,895,738
October 28, 2011 Warrants [Member] \| Warrants Liability, at Fair Value [Member]
Class of Warrant or Right [Line Items]
Recognition of warrants fair value at date of issuance	$ 1,300,000
Number of warrants exercised during the period		613,913	0	478,261
Proceeds of Warrants		$ 798,087		$ 621,739
Warrants expiration date		May 02, 2017

Warrants Liability, at Fair Value - Summary of Assumptions Used in Black-Scholes Model to Calculate Fair Value of Warrants Liability (Detail) - Warrants Liability, at Fair Value [Member]	12 Months Ended
	Dec. 31, 2016
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Risk free interest rate	0.85%
Expected term	3 months 29 days
Expected volatility	100.00%
Expected dividend yield	0.00%
Expected forfeiture rate	0.00%

Warrants Liability, at Fair Value - Summary of Company's Warrants Liability Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair value, beginning of period	$ 122,226	$ 1,008,363	$ 2,794,891
Issuance of warrants	0	0	0
Exercise of warrants	(309,130)		(1,721,523)
Change in fair value	$ 186,904	(886,137)	(65,005)
Fair value, end of period		$ 122,226	$ 1,008,363

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research fees	$ 388,977	$ 334,565
Prepaid insurance	638,139	598,909
Prepaid pre-commercialization fees	65,000	35,500
Prepaid subscriptions fees	23,347	22,770
Prepaid rent		19,756
Other	58,281	36,444
Total prepaid expenses and other current assets	$ 1,173,744	$ 1,047,944

Property and Equipment, net - Property and Equipment, net (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 350,554	$ 357,684
Less: Accumulated depreciation	(159,169)	(113,480)
Total property and equipment, net	191,385	244,204
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,915	27,915
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	169,931	177,061
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 152,708	$ 152,708

Accrued Expenses and Other Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued preclinical and clinical trial expenses	$ 970,649	$ 623,855
Accrued professional fees	227,457	102,673
Accrued compensation and benefits	821,935	264,237
Accrued license fees	252,500	152,500
Deferred rent and lease incentive	24,011	18,094
Other	24,035
Current accrued expenses and other liabilities	2,320,587	1,161,359
Deferred rent and lease incentive-non-current	157,456	181,162
Non-current accrued expenses and other liabilities	157,456	181,162
Total accrued expenses and other liabilities	$ 2,478,043	$ 1,342,521

Commitments and Contingencies - Future Minimum Lease Payments under Operating Lease Agreement (Detail)	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2018	$ 213,644
2019	220,053
2020	226,655
2021	233,454
2022	220,023
Total	$ 1,113,829

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Area of leased property \| ft²	5,200
Lease expiration year	2022
Tenant build-out costs	$ 131,000
Rent expense		$ 204,170	$ 201,920	$ 129,727
Obligations under capital leases		$ 0

Agreements - Northwestern University - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
License Agreement [Line Items]
Accrued license fees	$ 252,500	$ 152,500
Northwestern License Agreement [Member]
License Agreement [Line Items]
License fee paid	424,885
Accrued license fees	252,500	$ 152,500
Future milestone payment	$ 300,000

Agreements - BioMarin - Additional Information (Detail) - License Agreement with BioMarin [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
License Agreement [Line Items]
Date on which strategic collaboration is entered into	Oct. 26, 2012
Royalty agreement period	7 years
Net sales royalty threshold	$ 100,000,000
Milestone payment due upon NDA acceptance	2,600,000
Milestone payment due upon NDA approval	7,200,000
Costs paid for Firdapse joint studies	$ 3,800,000	$ 3,800,000
Milestone Payment Description	BioMarin’s obligation to pay the milestone payments due to the former Huxley stockholders (and the Company’s corresponding obligation to pay such milestone payments expressly expires if these milestones have not been not satisfied by April 20, 2018
Huxley Pharmaceuticals [Member]
License Agreement [Line Items]
Milestone payment due upon NDA acceptance	$ 2,425,000
Milestone payment due upon NDA approval	4,200,000
Third Party Licensor [Member]
License Agreement [Line Items]
Milestone payment due upon NDA acceptance	150,000
Milestone payment due upon NDA approval	$ 3,000,000
Minimum [Member]
License Agreement [Line Items]
Percentage of royalty on net sales	7.00%
Maximum [Member]
License Agreement [Line Items]
Percentage of royalty on net sales	10.00%

Related Party Transactions - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Consulting fees to Company officer and members of the Scientific Advisory Board		$ 10,000	$ 10,000	$ 10,000
CEO Employment Agreement [Member]
Related Party Transaction [Line Items]
Annual base salary of CEO		$ 525,000
Expiration date of employment agreement		2018-11
Consulting Agreements [Member]
Related Party Transaction [Line Items]
Consulting fees to Company officer and members of the Scientific Advisory Board	$ 45,000

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Statutory rate			34.00%	34.00%	34.00%
Increase (decrease) in valuation allowance on deferred tax assets			$ (3,388,951)	$ 8,287,962
Reduction in net deferred tax assets	$ 13,500,000
Net operating loss carryforwards	62,600,000		$ 62,600,000	$ 56,300,000
Net operating loss carryforwards expiration date			Beginning in 2024 and ending in 2037.
Effective tax rate			0.00%	0.00%	0.00%
Interest or penalties accrued	$ 0		$ 0
Scenario, Plan [Member]
Income Taxes [Line Items]
Statutory rate		21.00%
U.S. federal corporate tax rate [Member]
Income Taxes [Line Items]
Statutory rate			35.00%

Income Taxes - Schedule of Reconciliation of Income Tax Expense (Benefit) Computed at Statutory Federal Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory rate	34.00%	34.00%	34.00%
State tax	3.50%	3.40%	3.60%
Valuation allowance	26.50%	(44.70%)	(37.70%)
Federal rate change	(73.20%)	0.00%	0.00%
Tax credit	6.80%	6.20%	0.00%
Other	2.40%	1.10%	0.10%
Reconciliation of income tax expense (benefit)	0.00%	0.00%	0.00%

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Components of Deferred Tax Assets [Abstract]
Net operating loss	$ 15,718,570	$ 21,050,217
Start-up cost	10,508,487	12,823,113
Tax credits	11,582,134	6,960,838
Deferred compensation	1,326,189	1,555,425
Other	72,395	207,133
Gross deferred tax asset	39,207,775	42,596,726
Valuation allowance	(39,207,775)	(42,596,726)
Net deferred tax assets	$ 0	$ 0

Stockholders' Equity (Preferred Stock and Common Stock) - Additional Information (Detail)	Dec. 31, 2017 Vote $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 shares
Equity [Abstract]
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value \| $ / shares	$ 0.001	$ 0.001
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	150,000,000	150,000,000	150,000,000	100,000,000
Common stock, par value \| $ / shares	$ 0.001	$ 0.001	$ 0.001
Common stock, shares issued	102,549,498	82,972,316
Common stock, shares outstanding	102,549,498	82,972,316
Number of votes entitled for each share of common stock \| Vote	1

Stockholders' Equity (2017 Shelf Registration Statement) - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 28, 2017	Dec. 31, 2017	Jul. 12, 2017
Underwritten Public Offering [Member]
Stockholders' Equity [Line Items]
Number of common stock sold in offering	16,428,572
Common stock issued, price per share	$ 3.50
Gross proceeds from issuance of common stock	$ 57,500,000
Offering expenses	$ 3,700,000
2017 Shelf Registration Statement [Member]
Stockholders' Equity [Line Items]
Maximum dollar amount of securities to be issued under shelf registration statement			$ 150,000,000
Value of common stock available for future sale		$ 92,500,000

Stockholders' Equity (Stockholder Rights Plan) - Additional Information (Detail) - $ / shares	Sep. 19, 2016	Sep. 20, 2011	Dec. 31, 2017
Series A Preferred Stock [Member]
Stockholders' Equity [Line Items]
Preferred share purchase right price		$ 7.80
Series A Preferred Stock [Member] \| Certificate of Designation [Member]
Stockholders' Equity [Line Items]
Junior participating preferred stock shares issued available for issuance under rights agreement, initial			500,000
Junior participating preferred stock shares issued available for issuance under rights agreement, amended			1,500,000
Stockholder Rights Plan [Member]
Stockholders' Equity [Line Items]
Warrants exercise price		$ 7.80
Minimum percentage of outstanding stock acquired by a person or group to trigger Shareholder Rights Plan		17.50%
Stockholders Rights Plan redemption price of right		$ 0.001
Class of warrant or right expiration date	Sep. 20, 2016
Class of warrant or right expiration date, Extended	Sep. 20, 2019

Stock Compensation Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual term	4 years 4 months 24 days
Number of stock options exercised	880,000
Proceeds from exercise of stock options	$ 368,185	$ 80,251	$ 390,351
Stock options granted	1,550,000
Expected dividend rate	0.00%	0.00%	0.00%
Stock Option [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting period	1 year
Stock option contractual term	5 years
Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting period	3 years
Stock option contractual term	7 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 65,336	$ 75,494	$ 75,440
2014 Stock Incentive Plan [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for issuance under the Plan	9,000,000
Common stock shares available for future issuance under the Plan	3,646,668
2006 Stock Incentive Plan [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for future issuance under the Plan	0
Two Thousand Fourteen Plan [Member] \| Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting period	3 years
Two Thousand Fourteen Plan [Member] \| Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting period	4 years
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options exercised	780,000	75,000	265,000
Proceeds from exercise of stock options	$ 368,185	$ 80,251	$ 390,351
Non-cash stock-based compensation expense	$ 2,342,625	$ 1,760,591	$ 1,510,018
Stock option granted, contractual term	7 years	7 years
Stock options granted	1,550,000	1,285,000	1,760,000
Unrecognized compensation expense related to non-vested stock compensation awards granted under the Plan	$ 1,367,155
Expected remaining weighted average vesting period	1 year 4 months 20 days
Expected dividend rate	0.00%
Options to Purchase Common Stock [Member] \| Cashless Basis [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options exercised	100,000	50,000	984,608
Shares issued for cashless option exercise	84,280	20,030	761,600

Stock Compensation Plans - Summary of Stock Option Activity under the Company's Plan (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Outstanding at beginning of year \| shares	4,660,000
Number of options, Granted \| shares	1,550,000
Number of options, Exercised \| shares	(880,000)
Number of options, Forfeited or cancelled \| shares	(138,334)
Number of options, Expired \| shares	0
Number of options, Outstanding at end of year \| shares	5,191,666
Number of options, Exercisable at end of year \| shares	2,908,330
Weighted average exercise price, Outstanding at beginning of year \| $ / shares	$ 1.94
Weighted average exercise price, Granted \| $ / shares	1.17
Weighted average exercise price, Exercised \| $ / shares	0.47
Weighted average exercise price, Forfeited or cancelled \| $ / shares	1.94
Weighted average exercise price, Expired \| $ / shares	0.00
Weighted average exercise price, Outstanding at end of year \| $ / shares	1.96
Weighted average exercise price, Exercisable at end of year \| $ / shares	$ 2.44
Weighted Average Remaining Contractual Term (Years), Outstanding at end of year	4 years 11 months 8 days
Weighted Average Remaining Contractual Term (Years), Exercisable at end of year	4 years 4 months 24 days
Aggregate Intrinsic value, Outstanding at end of year \| $	$ 10,178,881
Aggregate Intrinsic value, Exercisable at end of year \| $	$ 4,334,327

Stock Compensation Plans - Schedule of Other Information Pertaining to Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-average fair value of granted stock options	$ 0.91	$ 0.62	$ 2.13
Total fair value of vested stock options	$ 2,016,992	$ 1,634,562	$ 1,307,895
Total intrinsic value of exercised stock options	$ 2,296,100	$ 42,000	$ 3,311,599

Stock Compensation Plans - Summary of Company's Stock Options Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	$ 0.47	$ 0.47	$ 0.47
Range of Exercise Prices Upper Range	$ 4.64	$ 4.64	$ 4.64
Number Outstanding, Options Outstanding	5,191,666
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 11 months 8 days
Weighted Average Exercise Price, Options Outstanding	$ 1.96
Number Exercisable Options Exercisable	2,908,330
Weighted Average Remaining Contractual Life (Years), Options Exercisable	4 years 4 months 24 days
Weighted Average Exercise Price, Options Exercisable	$ 2.44
$0.47 to $0.85 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	0.47
Range of Exercise Prices Upper Range	$ 0.85
Number Outstanding, Options Outstanding	1,085,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	5 years 1 month 24 days
Weighted Average Exercise Price, Options Outstanding	$ 0.78
Number Exercisable Options Exercisable	550,000
Weighted Average Remaining Contractual Life (Years), Options Exercisable	5 years 1 month 2 days
Weighted Average Exercise Price, Options Exercisable	$ 0.79
$0.86 to $1.14 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	0.86
Range of Exercise Prices Upper Range	$ 1.14
Number Outstanding, Options Outstanding	1,516,666
Weighted Average Remaining Contractual Life (Years), Options Outstanding	6 years
Weighted Average Exercise Price, Options Outstanding	$ 1.13
Number Exercisable Options Exercisable	199,999
Weighted Average Remaining Contractual Life (Years), Options Exercisable	5 years 11 months 26 days
Weighted Average Exercise Price, Options Exercisable	$ 1.13
$1.15 to $2.80 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	1.15
Range of Exercise Prices Upper Range	$ 2.80
Number Outstanding, Options Outstanding	1,195,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 9 months
Weighted Average Exercise Price, Options Outstanding	$ 2.48
Number Exercisable Options Exercisable	866,665
Weighted Average Remaining Contractual Life (Years), Options Exercisable	4 years 7 months 24 days
Weighted Average Exercise Price, Options Exercisable	$ 2.51
$2.81 to $3.23 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	2.81
Range of Exercise Prices Upper Range	$ 3.23
Number Outstanding, Options Outstanding	1,020,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	3 years 8 months 2 days
Weighted Average Exercise Price, Options Outstanding	$ 3.12
Number Exercisable Options Exercisable	1,020,000
Weighted Average Remaining Contractual Life (Years), Options Exercisable	3 years 8 months 2 days
Weighted Average Exercise Price, Options Exercisable	$ 3.12
$3.24 to $4.64 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	3.24
Range of Exercise Prices Upper Range	$ 4.64
Number Outstanding, Options Outstanding	375,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 22 days
Weighted Average Exercise Price, Options Outstanding	$ 3.93
Number Exercisable Options Exercisable	271,666
Weighted Average Remaining Contractual Life (Years), Options Exercisable	3 years 9 months 22 days
Weighted Average Exercise Price, Options Exercisable	$ 3.94

Stock Compensation Plans - Summary of Stock Options Awards Based on Certain Assumptions (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, Minimum	1.66%	0.76%	1.00%
Risk free interest rate, Maximum	2.25%	2.15%	2.13%
Expected volatility	104.00%	100.00%	102.00%
Expected dividend yield	0.00%	0.00%	0.00%
Expected forfeiture rate	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	4 years	2 years	3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	7 years	6 years	7 years

Stock Compensation Plans - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Restricted Stock Activity [Line Items]
Nonvested balance at beginning of year	26,667	53,334	80,000
Granted	0	0	0
Vested	(26,667)	(26,667)	(26,666)
Forfeited	0	0	0
Nonvested balance at end of year		26,667	53,334
Nonvested Weighted Average Grant Date Fair Value balance at beginning of year	$ 2.83	$ 2.83	$ 2.83
Weighted Average Grant Date Fair Value, Granted	0	0	0
Weighted Average Grant Date Fair Value, Vested	2.83	2.83	2.83
Weighted Average Grant Date Fair Value, Forfeited	$ 0	0	0
Nonvested Weighted Average Grant Date Fair Value balance at end of year		$ 2.83	$ 2.83

Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Employees contribution of pre-tax annual compensation	15.00%
Discretionary matching contributions of employee contributions of an employee's gross salary	4.00%
Contributions	$ 84,000	$ 59,000	$ 69,000

Quarterly Financial Information (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Loss from operations	(5,511,786)	(4,306,708)	(4,181,271)	(4,679,871)	(4,314,199)	(3,914,014)	(4,814,452)	(6,237,536)	(18,679,636)	(19,280,201)	(20,398,352)
Change in fair value of warrants liability			210,331	(397,235)	106,946	(106,948)	152,783	733,356	(186,904)	886,137	65,005
Net loss	$ (5,387,698)	$ (4,177,649)	$ (3,879,901)	$ (4,967,129)	$ (4,163,320)	$ (3,953,981)	$ (4,568,914)	$ (5,386,237)	$ (18,412,377)	$ (18,072,452)	$ (20,232,958)
Net loss per share - basic and diluted	$ (0.06)	$ (0.05)	$ (0.05)	$ (0.06)	$ (0.05)	$ (0.05)	$ (0.06)	$ (0.07)	$ (0.21)	$ (0.22)	$ (0.25)

Subsequent Events - Additional Information (Detail) - shares	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Stock options granted		1,550,000
Options to Purchase Common Stock [Member]
Subsequent Event [Line Items]
Stock option granted, contractual term		7 years	7 years
Stock options granted		1,550,000	1,285,000	1,760,000
Options to Purchase Common Stock [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Stock option granted, contractual term	7 years
Stock options granted	1,772,500

Stockholders' Equity (2016 Shelf Registration Statement) - Additional Information (Detail)	Dec. 23, 2016 USD ($)
2016 Shelf Registration Statement [Member]
Stockholders' Equity [Line Items]
Maximum dollar amount of common stock to be issued under shelf registration statement	$ 33,800,000