Catalyst Pharmaceuticals (CPRX) 10-Q 7 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	CPRX
Entity Registrant Name	CATALYST PHARMACEUTICALS, INC.
Entity Central Index Key	1,369,568
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Company	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		102,739,257

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 10,616,313	$ 57,496,702
Short-term investments	51,047,842	26,516,711
Prepaid expenses and other current assets	816,820	1,173,744
Total current assets	62,480,975	85,187,157
Investments	5,018,857
Property and equipment, net	201,093	191,385
Deposits	8,888	8,888
Total assets	67,709,813	85,387,430
Current Liabilities:
Accounts payable	1,340,984	1,945,575
Accrued expenses and other liabilities	2,127,450	2,320,587
Total current liabilities	3,468,434	4,266,162
Accrued expenses and other liabilities, non-current	164,781	157,456
Total liabilities	3,633,215	4,423,618
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized: none issued and outstanding at September 30, 2018 and December 31, 2017
Common stock, $0.001 par value, 150,000,000 shares authorized; 102,689,257 shares and 102,549,498 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	102,689	102,549
Additional paid-in capital	210,084,209	207,421,710
Accumulated deficit	(146,064,352)	(126,560,447)
Accumulated other comprehensive loss	(45,948)
Total stockholders' equity	64,076,598	80,963,812
Total liabilities and stockholders' equity	$ 67,709,813	$ 85,387,430

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
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	102,689,257	102,549,498
Common stock, shares outstanding	102,689,257	102,549,498

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating costs and expenses:
Research and development	$ 4,538,369	$ 2,704,923	$ 11,502,235	$ 7,970,603
General and administrative	3,644,234	1,601,785	8,949,663	5,197,247
Total operating costs and expenses	8,182,603	4,306,708	20,451,898	13,167,850
Loss from operations	(8,182,603)	(4,306,708)	(20,451,898)	(13,167,850)
Other income, net	343,730	129,059	947,993	330,075
Change in fair value of warrants liability				(186,904)
Loss before income taxes	(7,838,873)	(4,177,649)	(19,503,905)	(13,024,679)
Provision for income taxes	0	0	0	0
Net loss	$ (7,838,873)	$ (4,177,649)	$ (19,503,905)	$ (13,024,679)
Net loss per share - basic and diluted	$ (0.08)	$ (0.05)	$ (0.19)	$ (0.16)
Weighted average shares outstanding - basic and diluted	102,641,504	84,797,969	102,598,740	83,898,724
Net loss	$ (7,838,873)	$ (4,177,649)	$ (19,503,905)	$ (13,024,679)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities	(9,450)		(45,948)
Comprehensive loss	$ (7,848,323)	$ (4,177,649)	$ (19,549,853)	$ (13,024,679)

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity (unaudited) - 9 months ended Sep. 30, 2018 - USD ($)	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2017	$ 80,963,812	$ 0	$ 102,549	$ 207,421,710	$ (126,560,447)
Issuance of common stock, net	10,549		3	10,546
Issuance of stock options for services	2,506,026			2,506,026
Exercise of stock options for common stock	146,064		137	145,927
Other comprehensive loss	(45,948)					$ (45,948)
Net loss	(19,503,905)				(19,503,905)
Ending Balance at Sep. 30, 2018	$ 64,076,598	$ 0	$ 102,689	$ 210,084,209	$ (146,064,352)	$ (45,948)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net loss	$ (19,503,905)	$ (13,024,679)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	25,485	38,754
Stock-based compensation	2,521,023	1,922,451
Change in fair value of warrants liability		186,904
(Increase) decrease in:
Prepaid expenses and other current assets and deposits	356,924	537,452
Increase (decrease) in:
Accounts payable	(604,591)	148,432
Accrued expenses and other liabilities	(185,812)	477,981
Net cash used in operating activities	(17,390,876)	(9,712,705)
Investing Activities:
Purchases of property and equipment	(35,193)
Purchases of investments	(37,141,968)	(64,748)
Proceeds from maturities of investments	7,546,032
Net cash provided by (used in) investing activities	(29,631,129)	(64,748)
Financing Activities:
Payment of employee withholding tax related to stock-based compensation	(4,448)
Proceeds from exercise of warrants		3,209,423
Proceeds from exercise of stock options	146,064	3,950
Net cash provided by (used in) financing activities	141,616	3,213,373
Net increase (decrease) in cash and cash equivalents	(46,880,389)	(6,564,080)
Cash and cash equivalents - beginning of period	57,496,702	13,893,064
Cash and cash equivalents - end of period	10,616,313	7,328,984
Non-cash investing and financing activities:
Unrealized gain (loss) on available-for-sale securities	$ (45,948)
Exercise of liability classified warrants for common stock		$ 309,130

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business. Catalyst Pharmaceuticals, Inc. (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), and MuSK antibody positive myasthenia gravis (MuSK-MG). 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 September 30, 2018. 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 10. Capital Resources While there can be no assurance, based on currently available information, the Company estimates that it has sufficient resources to support its operations for at least the next 12 months. The Company may raise additional funds in the future, if required for its business, 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 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 Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies. a. INTERIM FINANCIAL STATEMENTS. 10-Q In the opinion of management, the accompanying unaudited interim consolidated financial statements of the Company contain all adjustments (consisting of only normal recurring adjustments) necessary to present fairly the financial position of the Company as of the dates and for the periods presented. Accordingly, these consolidated statements should be read in conjunction with the financial statements and notes thereto for the year ended December 31, 2017 included in the 2017 Annual Report on Form 10-K b. PRINCIPLES OF CONSOLIDATION c. USE OF ESTIMATES. d. CASH AND CASH EQUIVALENTS. e. INVESTMENTS Short-term bond fund The short-term bond fund is classified in 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. At September 30, 2018 and December 31, 2017, the only investment classified as trading securities was the short-term bond fund. Unrealized gain (loss) on trading securities was $0 and ($29,430), respectively, for the three and nine months ended September 30, 2018, and $29,431 and $58,861 for the three and nine months ended September 30, 2017 and is included in other income, net in the accompanying consolidated statements of operations. U.S. Treasuries U.S. Treasuries are classified as available-for-sale available-for-sale Available-for-sale non-current available-for-sale available-for-sale available-for-sale f. PREPAID EXPENSES AND OTHER CURRENT ASSETS pre-commercialization pre-clinical g. FAIR VALUE OF FINANCIAL INSTRUMENTS. h. FAIR VALUE MEASUREMENTS. 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 Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 10,372,148 $ 10,372,148 $ — $ — Short-term investments: Short-term bond fund $ 26,534,352 $ 26,534,352 $ — $ — U.S. Treasuries $ 24,513,490 $ — $ 24,513,490 $ — Investments: U.S. Treasuries $ 5,018,857 $ — $ 5,018,857 $ — Balances as of Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 56,820,688 $ 56,820,688 $ — $ — Short-term investments: Short-term bond fund $ 26,516,711 $ 26,516,711 $ — $ — i. WARRANTS LIABILITY. j. STOCK-BASED COMPENSATION. As of September 30, 2018, there were outstanding stock options to purchase 8,062,500 shares of common stock, of which stock options to purchase 4,011,663 shares of common stock were exercisable as of September 30, 2018. For the three and nine-month periods ended September 30, 2018 and 2017, the Company recorded stock-based compensation expense as follows: Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 Research and development $ 240,122 $ 192,796 $ 820,062 $ 622,700 General and administrative 518,054 336,942 1,700,961 1,299,751 Total stock-based compensation $ 758,176 $ 529,738 $ 2,521,023 $ 1,922,451 k. COMPREHENSIVE INCOME (LOSS). available-for-sale l. NET LOSS PER SHARE. September 30, 2018 2017 Options to purchase common stock 8,062,500 6,085,000 Unvested restricted stock — 26,667 Potential equivalent common stock excluded 8,062,500 6,111,667 Potentially dilutive options to purchase common stock as of September 30, 2018 have exercise prices ranging from $0.79 to $4.64. Potentially dilutive options to purchase common stock as of September 30, 2017 had exercise prices ranging from $0.47 to $4.64. m. RECENTLY ISSUED ACCOUNTING STANDARDS . No. 2016-02, Leases (Topic 842) 2016-02 In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting 2017-09 In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting 2018-07 n. RECLASSIFICATIONS.

Warrants Liability, at Fair Val

Warrants Liability, at Fair Value	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Warrants Liability, at Fair Value	3. Warrants Liability, at Fair Value. 2011 Warrants 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 the period 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 had 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 were readily observable in the warrant agreement. The annual rate of dividends was 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 was a Level 2 input, while the historical volatility was a Level 3 input in accordance with the fair value accounting guidance. Since the lowest level input was a Level 3, the Company determined the 2011 warrants liability were most appropriately classified within Level 3 of the fair value hierarchy. This liability was subject to a fair value mark-to-market The following table rolls forward the fair value of the Company’s warrants liability activity for the three and nine-month periods ended September 30, 2017: Three months September 30, Nine months September 30, Fair value, beginning of period $ — $ 122,226 Issuance of warrants — — Exercise of warrants — (309,130 ) Change in fair value — 186,904 Fair value, end of period $ — $ — On May 2, 2017, the outstanding and unexercised 2011 warrants expired. During the nine months ended September 30, 2017, 613,913 of the 2011 warrants were exercised, with proceeds of $798,087 to the Company.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	4. Investments. Available-for-sale Amortized Gross Gross Estimated At September 30, 2018: U.S. Treasuries – ST $ 24,524,244 $ — $ (10,754 ) $ 24,513,490 U.S. Treasuries – LT 5,054,051 — (35,194 ) 5,018,857 Total $ 29,578,295 $ — $ (45,948 ) $ 29,532,347 At December 31, 2017, the Company did not have any available-for-sale In accordance with FASB ASC Topic 320, “Investments – Debt and Equity Securities”, or ASC 320, the Company has classified its U.S. Treasuries as available-for-sale available-for-sale Certain U.S. Treasuries at September 30, 2018 had fair values less than their amortized costs and, therefore, contained unrealized losses. Given that the Company has no intent to sell the U.S. Treasuries until a recovery of the fair value, which may be at maturity, and there are no current requirements to sell any of these securities, the Company did not consider these investments to be other-than-temporarily impaired as of September 30, 2018. The Company anticipates full recovery of amortized costs with respect to these investments at maturity. The duration of time the U.S. Treasuries have been in a continuous unrealized loss position as of September 30, 2018 was less than 9 months. The estimated fair values of available-for-sale September 30, Due in one year or less $ 24,513,490 Due after one year but within two years 5,018,857 $ 29,532,347

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets. Prepaid expenses and other current assets consist of the following: September 30, December 31, Prepaid research fees $ 301,837 $ 388,977 Prepaid insurance 116,774 638,139 Prepaid pre-commercialization 121,706 65,000 Prepaid subscription fees 63,288 23,347 Prepaid rent 21,924 — Other 191,291 58,281 Total prepaid expenses and other current assets $ 816,820 $ 1,173,744

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net. Property and equipment, net consists of the following: September 30, December 31, Computer equipment $ 27,915 $ 27,915 Furniture and equipment 191,835 169,931 Leasehold improvements 165,997 152,708 385,747 350,554 Less: Accumulated depreciation (184,654 ) (159,169 ) Total property and equipment, net $ 201,093 $ 191,385 Depreciation expense was $9,294 and $25,485, respectively, for the three and nine-month periods ended September 30, 2018 and $12,839 and $38,754, respectively for the three and nine-month periods ended September 30, 2017.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	7. Accrued Expenses and Other Liabilities. Accrued expenses and other liabilities consist of the following: September 30, December 31, Accrued preclinical and clinical trial expenses $ 896,566 $ 970,649 Accrued professional fees 429,073 227,457 Accrued compensation and benefits 740,939 821,935 Accrued license fees — 252,500 Deferred rent and lease incentive 21,914 24,011 Other 38,958 24,035 Current accrued expenses and other liabilities 2,127,450 2,320,587 Deferred rent and lease incentive – non-current 164,781 157,456 Non-current 164,781 157,456 Total accrued expenses and other liabilities $ 2,292,231 $ 2,478,043

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies. a. LICENSE AGREEMENT WITH NORTHWESTERN UNIVERSITY (CPP-115). On August 27, 2009, the Company entered into a license agreement with Northwestern University (Northwestern), under which it acquired worldwide rights to CPP-115. As of September 30, 2018, the Company had paid $424,885 in connection with the license and had accrued license fees of $0 in the accompanying September 30, 2018 consolidated balance sheet for expenses, maintenance fees and milestones. Recently, the Company became aware that certain patents granted to Northwestern in 2018 (which patents have been licensed by Northwestern to a third-party) for a new GABA aminotransferase inhibitor were derived from CPP-115. As a result, it is the Company’s position that Northwestern has violated the license agreement based on its failure to transfer these new patent rights to the Company as part of the existing license agreement. It is also the Company’s position that Northwestern’s publication of information about the new patents in violation of the license agreement has damaged the Company. On October 26, 2018, because good faith efforts to resolve these disputes had not been successful, the Company notified Northwestern that it was terminating the license agreement and seeking damages for Northwestern’s breach of the license agreement. Further, on the same date, the Company filed a claim for damages in arbitration against Northwestern for Northwestern’s breaches of the license agreement. On November 5, 2018, Northwestern advised the Company that in its view, Northwestern has a right to terminate the license agreement with the Company because the Company has allegedly breached the license agreement by failing to pay certain milestones and by allegedly failing to use commercially reasonable efforts to develop and commercialize any products. Northwestern has also advised the Company that, in its view, the Company has engaged in wrongful conduct and communications with the third party that licensed the new patents from Northwestern, and that such communications have damaged Northwestern’s relationship with that third party. The Company disputes Northwestern’s allegations and intends to vigorously defend itself against any claims that Northwestern may bring against it in the arbitration proceedings relating to these allegations. This matter is at a very early stage and there can be no assurance as to the outcome of this matter. See Note 12. b. LICENSE AGREEMENT WITH NEW YORK UNIVERSITY AND THE FEINSTEIN INSTITUTE FOR MEDICAL RESEARCH. c. LICENSE AGREEMENT WITH BIOMARIN (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 ® ® Additionally, the Company’s license agreement with BioMarin requires the Company 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. With respect to the third party licensor of the rights that have been sublicensed to the Company, the Company has agreed to pay: (i) $150,000 upon acceptance by the FDA of a filing of an NDA for Firdapse ® ® ® With respect to the former Huxley stockholders, the Company had agreed that it would pay the following milestone payments if either of the following milestones were satisfied before April 20, 2018: (i) $2,425,000 upon acceptance by the FDA of a filing of an NDA for Firdapse ® ® ® The Company also agreed to share in the cost of certain post-marketing studies being conducted by BioMarin, and, as of September 30, 2018, the Company had paid BioMarin $3.8 million related to expenses in connection with Firdapse ® d. AGREEMENTS FOR DRUG DEVELOPMENT, PRE-CLINICAL

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes. The Company is subject to income taxes in the U.S. federal jurisdiction and various states 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 any years before 2015. 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. The Company’s net deferred tax asset has a 100% valuation allowance at September 30, 2018 and December 31, 2017 as the Company believes that it is more likely than not that the deferred tax asset will not be realized.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity. 2016 Shelf Registration Statement On December 23, 2016, the Company filed a shelf Registration Statement on Form S-3 No. 333-215315) 2017 Shelf Registration Statement On July 12, 2017, the Company filed a universal shelf Registration Statement on Form S-3 No. 333-219259) On November 28, 2017, the Company filed a prospectus supplement and offered for sale 16,428,572 shares of its common stock at a price of $3.50 per share in an underwritten public offering under the 2017 Shelf Registration. 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. At September 30, 2018, there is approximately $92.5 million available for future sale under the 2017 Shelf Registration Statement.

Stock Compensation

Stock Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation	11. Stock Compensation. Stock Options During the three and nine-month periods ended September 30, 2018, the Company granted seven-year term options to purchase an aggregate of 550,000 shares and 3,267,500 shares, respectively, of the Company’s common stock to employees and directors. The Company recorded stock-based compensation related to stock options totaling $758,176 and $2,506,026 respectively, during the three and nine-month periods ended September 30, 2018. During the three and nine-month periods ended September 30, 2018, 5,000 options and 1,314,998 options vested, respectively. During the three and nine-month periods ended September 30, 2017, the Company granted seven-year term options to purchase an aggregate of 0 shares and 1,535,000 shares, respectively, of the Company’s common stock to employees and directors. The Company recorded stock-based compensation related to stock options totaling $510,715 and $1,866,005 respectively, during the three and nine-month periods ended September 30, 2017. During the three and nine-month periods ended September 30, 2017, 261,668 options and 1,138,335 options vested, respectively. During the three and nine-month periods ended September 30, 2018, options to purchase 89,999 shares and 136,665 shares, respectively, of the Company’s common stock were exercised, with proceeds of $104,532 and $146,064, respectively, to the Company. During the three and nine months ended September 30, 2017, options to purchase 5,000 shares of the Company’s common stock were exercised, with proceeds of $3,950 to the Company. As of September 30, 2018, there was approximately $6,204,000 of unrecognized compensation expense related to non-vested Restricted Stock Units No restricted stock units were granted during the three and nine-month periods ended September 30, 2018 and 2017. No stock-based compensation related to restricted stocks was recorded during the three and nine-months periods ended September 30, 2018. The Company recorded stock-based compensation related to restricted stock units totaling $19,023 and $56,446, respectively, during the three and nine-month periods ended September 30, 2017. All restricted stock units were vested as of December 31, 2017. Common Stock No shares of common stock were granted during the three-month period ended September 30, 2018. During the nine-month period ended September 30, 2018, the Company granted 3,094 net shares of common stock to employees as compensation. The Company recorded stock-based compensation related to common stock issued to employees totaling $0 and approximately $15,000, respectively, during the three and nine-month periods ended September 30, 2018. There were no grants of common stock to employees during the three and nine-month periods ended September 30, 2017.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events. Subsequent to quarter end, the Company commenced an arbitration proceeding against Northwestern in regard to CPP-155.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
INTERIM FINANCIAL STATEMENTS	a. INTERIM FINANCIAL STATEMENTS. 10-Q In the opinion of management, the accompanying unaudited interim consolidated financial statements of the Company contain all adjustments (consisting of only normal recurring adjustments) necessary to present fairly the financial position of the Company as of the dates and for the periods presented. Accordingly, these consolidated statements should be read in conjunction with the financial statements and notes thereto for the year ended December 31, 2017 included in the 2017 Annual Report on Form 10-K
PRINCIPLES OF CONSOLIDATION.	b. PRINCIPLES OF CONSOLIDATION
USE OF ESTIMATES	c. USE OF ESTIMATES.
CASH AND CASH EQUIVALENTS	d. CASH AND CASH EQUIVALENTS.
INVESTMENTS	e. INVESTMENTS Short-term bond fund The short-term bond fund is classified in 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. At September 30, 2018 and December 31, 2017, the only investment classified as trading securities was the short-term bond fund. Unrealized gain (loss) on trading securities was $0 and ($29,430), respectively, for the three and nine months ended September 30, 2018, and $29,431 and $58,861 for the three and nine months ended September 30, 2017 and is included in other income, net in the accompanying consolidated statements of operations. U.S. Treasuries U.S. Treasuries are classified as available-for-sale available-for-sale Available-for-sale non-current available-for-sale available-for-sale available-for-sale
PREPAID EXPENSES AND OTHER CURRENT ASSETS	f. PREPAID EXPENSES AND OTHER CURRENT ASSETS pre-commercialization pre-clinical
FAIR VALUE OF FINANCIAL INSTRUMENTS	g. FAIR VALUE OF FINANCIAL INSTRUMENTS.
FAIR VALUE MEASUREMENTS	h. FAIR VALUE MEASUREMENTS. 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 Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 10,372,148 $ 10,372,148 $ — $ — Short-term investments: Short-term bond fund $ 26,534,352 $ 26,534,352 $ — $ — U.S. Treasuries $ 24,513,490 $ — $ 24,513,490 $ — Investments: U.S. Treasuries $ 5,018,857 $ — $ 5,018,857 $ — Balances as of Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 56,820,688 $ 56,820,688 $ — $ — Short-term investments: Short-term bond fund $ 26,516,711 $ 26,516,711 $ — $ —
WARRANTS LIABILITY	i. WARRANTS LIABILITY.
STOCK-BASED COMPENSATION	j. STOCK-BASED COMPENSATION. As of September 30, 2018, there were outstanding stock options to purchase 8,062,500 shares of common stock, of which stock options to purchase 4,011,663 shares of common stock were exercisable as of September 30, 2018. For the three and nine-month periods ended September 30, 2018 and 2017, the Company recorded stock-based compensation expense as follows: Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 Research and development $ 240,122 $ 192,796 $ 820,062 $ 622,700 General and administrative 518,054 336,942 1,700,961 1,299,751 Total stock-based compensation $ 758,176 $ 529,738 $ 2,521,023 $ 1,922,451
COMPREHENSIVE INCOME (LOSS)	k. COMPREHENSIVE INCOME (LOSS). available-for-sale
NET LOSS PER SHARE	l. NET LOSS PER SHARE. September 30, 2018 2017 Options to purchase common stock 8,062,500 6,085,000 Unvested restricted stock — 26,667 Potential equivalent common stock excluded 8,062,500 6,111,667 Potentially dilutive options to purchase common stock as of September 30, 2018 have exercise prices ranging from $0.79 to $4.64. Potentially dilutive options to purchase common stock as of September 30, 2017 had exercise prices ranging from $0.47 to $4.64.
RECENTLY ISSUED ACCOUNTING STANDARDS	m. RECENTLY ISSUED ACCOUNTING STANDARDS . No. 2016-02, Leases (Topic 842) 2016-02 In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting 2017-09 In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting 2018-07
RECLASSIFICATIONS	n. RECLASSIFICATIONS.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
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 Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 10,372,148 $ 10,372,148 $ — $ — Short-term investments: Short-term bond fund $ 26,534,352 $ 26,534,352 $ — $ — U.S. Treasuries $ 24,513,490 $ — $ 24,513,490 $ — Investments: U.S. Treasuries $ 5,018,857 $ — $ 5,018,857 $ — Balances as of Quoted Prices Significant Significant Cash and cash equivalents: Money market funds $ 56,820,688 $ 56,820,688 $ — $ — Short-term investments: Short-term bond fund $ 26,516,711 $ 26,516,711 $ — $ —
Stock-Based Compensation Expense	For the three and nine-month periods ended September 30, 2018 and 2017, the Company recorded stock-based compensation expense as follows: Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 Research and development $ 240,122 $ 192,796 $ 820,062 $ 622,700 General and administrative 518,054 336,942 1,700,961 1,299,751 Total stock-based compensation $ 758,176 $ 529,738 $ 2,521,023 $ 1,922,451
Potential Shares Excluded from Determination of Basic and Diluted Net Loss Per Share	l. NET LOSS PER SHARE. September 30, 2018 2017 Options to purchase common stock 8,062,500 6,085,000 Unvested restricted stock — 26,667 Potential equivalent common stock excluded 8,062,500 6,111,667

Warrants Liability, at Fair V_2

Warrants Liability, at Fair Value (Tables)	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Summary of Company's Warrants Liability Activity	The following table rolls forward the fair value of the Company’s warrants liability activity for the three and nine-month periods ended September 30, 2017: Three months September 30, Nine months September 30, Fair value, beginning of period $ — $ 122,226 Issuance of warrants — — Exercise of warrants — (309,130 ) Change in fair value — 186,904 Fair value, end of period $ — $ —

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Investments by Security type	Available-for-sale Amortized Gross Gross Estimated At September 30, 2018: U.S. Treasuries – ST $ 24,524,244 $ — $ (10,754 ) $ 24,513,490 U.S. Treasuries – LT 5,054,051 — (35,194 ) 5,018,857 Total $ 29,578,295 $ — $ (45,948 ) $ 29,532,347
Estimated Fair Values of Available for Sale Securities	The estimated fair values of available-for-sale September 30, Due in one year or less $ 24,513,490 Due after one year but within two years 5,018,857 $ 29,532,347

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following: September 30, December 31, Prepaid research fees $ 301,837 $ 388,977 Prepaid insurance 116,774 638,139 Prepaid pre-commercialization 121,706 65,000 Prepaid subscription fees 63,288 23,347 Prepaid rent 21,924 — Other 191,291 58,281 Total prepaid expenses and other current assets $ 816,820 $ 1,173,744

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and equipment, net consists of the following: September 30, December 31, Computer equipment $ 27,915 $ 27,915 Furniture and equipment 191,835 169,931 Leasehold improvements 165,997 152,708 385,747 350,554 Less: Accumulated depreciation (184,654 ) (159,169 ) Total property and equipment, net $ 201,093 $ 191,385

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following: September 30, December 31, Accrued preclinical and clinical trial expenses $ 896,566 $ 970,649 Accrued professional fees 429,073 227,457 Accrued compensation and benefits 740,939 821,935 Accrued license fees — 252,500 Deferred rent and lease incentive 21,914 24,011 Other 38,958 24,035 Current accrued expenses and other liabilities 2,127,450 2,320,587 Deferred rent and lease incentive – non-current 164,781 157,456 Non-current 164,781 157,456 Total accrued expenses and other liabilities $ 2,292,231 $ 2,478,043

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2011	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Maximum maturity period of cash and cash equivalent				Three months
Number of options outstanding		8,062,500		8,062,500
Number of options exercisable		4,011,663		4,011,663
Stock option exercise price range, Minimum				$ 0.79	$ 0.47
Stock option exercise price range, Maximum				$ 4.64	$ 4.64
Lease Expiration Date				Nov. 30, 2022
October 28, 2011 Warrants [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Warrants issued in offering	1,523,370
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 2, 2017
Other Income, Net [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Unrealized gain(loss),trading securities		$ 0	$ 29,431	$ (29,430)	$ 58,861
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
Maximum [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Minimum amortization period of compensation cost on straight line basis				5 years

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Fair Value Measurement Specific to Assets or Liability (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 5,018,857
Short-Term Bond Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	26,534,352	$ 26,516,711
U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	24,513,490
Investments	5,018,857
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	10,372,148	56,820,688
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Short-Term Bond Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	26,534,352	26,516,711
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	10,372,148	$ 56,820,688
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	24,513,490
Investments	$ 5,018,857

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies - Stock-Based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 758,176	$ 529,738	$ 2,521,023	$ 1,922,451
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	240,122	192,796	820,062	622,700
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 518,054	$ 336,942	$ 1,700,961	$ 1,299,751

Basis of Presentation and Sig_7

Basis of Presentation and Significant Accounting Policies - Potential Shares Excluded from Determination of Basic and Diluted Net Loss Per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	8,062,500	6,111,667
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	8,062,500	6,085,000
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded		26,667

Warrants Liability, at Fair V_3

Warrants Liability, at Fair Value - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2011	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Class of Warrant or Right [Line Items]
Recognition of warrants fair value at date of issuance		$ 0		$ 0
Proceeds of Warrants				$ 3,209,423
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
Warrants expiration date			May 2, 2017
Number of warrants exercised during the period				613,913
Proceeds of Warrants				$ 798,087

Warrants Liability, at Fair V_4

Warrants Liability, at Fair Value - Summary of Company's Warrants Liability Activity (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair value, beginning of period		$ 122,226
Issuance of warrants	$ 0	0
Exercise of warrants		(309,130)
Change in fair value		186,904
Fair value, end of period

Investment - Summary of Availab

Investment - Summary of Available-for-Sale Investments by Security type (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)
Net Investment Income [Line Items]
Amortized cost	$ 29,578,295
Gross Unrealized Gains	0
Gross Unrealized Losses	(45,948)
Estimated Fair Value	29,532,347
U.S. Treasuries - ST [Member]
Net Investment Income [Line Items]
Amortized cost	24,524,244
Gross Unrealized Gains	0
Gross Unrealized Losses	(10,754)
Estimated Fair Value	24,513,490
U.S. Treasuries - LT [Member]
Net Investment Income [Line Items]
Amortized cost	5,054,051
Gross Unrealized Gains	0
Gross Unrealized Losses	(35,194)
Estimated Fair Value	$ 5,018,857

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Realized gains losses from available for sale securities	$ 0	$ 0

Investment - Estimated Fair Val

Investment - Estimated Fair Values of Available for Sale Securities (Detail)	Sep. 30, 2018USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 24,513,490
Due after one year but within two years	5,018,857
Estimated Fair Value	$ 29,532,347

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research fees	$ 301,837	$ 388,977
Prepaid insurance	116,774	638,139
Prepaid pre-commercialization fees	121,706	65,000
Prepaid subscription fees	63,288	23,347
Prepaid rent	21,924
Other	191,291	58,281
Total prepaid expenses and other current assets	$ 816,820	$ 1,173,744

Property and Equipment, Net - P

Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 385,747	$ 350,554
Less: Accumulated depreciation	(184,654)	(159,169)
Total property and equipment, net	201,093	191,385
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	191,835	169,931
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 165,997	$ 152,708

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 9,294	$ 12,839	$ 25,485	$ 38,754

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued preclinical and clinical trial expenses	$ 896,566	$ 970,649
Accrued professional fees	429,073	227,457
Accrued compensation and benefits	740,939	821,935
Accrued license fees		252,500
Deferred rent and lease incentive	21,914	24,011
Other	38,958	24,035
Current accrued expenses and other liabilities	2,127,450	2,320,587
Deferred rent and lease incentive - non-current	164,781	157,456
Non-current accrued expenses and other liabilities	164,781	157,456
Total accrued expenses and other liabilities	$ 2,292,231	$ 2,478,043

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Jul. 26, 2018	Apr. 20, 2018	Sep. 30, 2018	Dec. 31, 2017
Commitments [Line Items]
Accrued license fees				$ 252,500
Northwestern License Agreement [Member]
Commitments [Line Items]
Accrued license fees			$ 0
Northwestern License Agreement [Member] | License [Member]
Commitments [Line Items]
License fee paid			$ 424,885
License Agreement with BioMarin [Member]
Commitments [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 Description			However, prior to April 20, 2018, the Company was advised that the former Huxley stockholders intended to take legal action against BioMarin and the Company seeking payment of the milestone payments due to them even if the milestones were achieved after their expiration date (April 20, 2018).
Costs paid for Firdapse joint studies			$ 3,800,000
License Agreement with BioMarin [Member] | Minimum [Member]
Commitments [Line Items]
Percentage of royalty on net sales			7.00%
License Agreement with BioMarin [Member] | Maximum [Member]
Commitments [Line Items]
Percentage of royalty on net sales			10.00%
License Agreement with BioMarin [Member] | Third Party Licensor [Member]
Commitments [Line Items]
Milestone payment due upon NDA acceptance			$ 150,000
Milestone payment due upon new drug application approval			$ 3,000,000
License Agreement with BioMarin [Member] | Huxley [Member]
Commitments [Line Items]
Milestone payment due upon NDA acceptance	$ 1,000,000	$ 2,425,000
Milestone payment due upon new drug application approval	$ 1,000,000	$ 4,200,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Valuation allowance	100.00%	100.00%

Stockholders' Equity (2016 Shel

Stockholders' Equity (2016 Shelf Registration Statement) - Additional Information (Detail)	Dec. 23, 2016USD ($)
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

Stockholders' Equity (2017 Shel

Stockholders' Equity (2017 Shelf Registration Statement) - Additional Information (Detail) - USD ($)	Nov. 28, 2017	Sep. 30, 2018	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

Stock Compensation - Additional

Stock Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from exercise of stock options			$ 146,064	$ 3,950
Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock unit granted	0	0	3,094	0
Stock-based compensation	$ 0		$ 15,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 0	$ 19,023	$ 0	$ 56,446
Restricted stock unit granted	0	0	0	0
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock unit granted	550,000	0	3,267,500	1,535,000
Stock-based compensation	$ 758,176	$ 510,715	$ 2,506,026	$ 1,866,005
Stock option vested during the period	5,000	261,668	1,314,998	1,138,335
Stock option granted, contractual term	7 years	7 years	7 years	7 years
Number of stock options exercised	89,999	5,000	136,665	5,000
Proceeds from exercise of stock options	$ 104,532	$ 3,950	$ 146,064	$ 3,950
Unrecognized compensation expense related to non-vested stock compensation awards granted under the Plan	$ 6,204,000		$ 6,204,000
Expected remaining weighted average vesting period			2 years 6 months 21 days