Catalyst Pharmaceuticals (CPRX) 10-K 18 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 14, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
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 Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		102,739,257
Entity Public Float			$ 298,397,093

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 16,559,400	$ 57,496,702
Short-term investments	36,922,213	26,516,711
Inventory	56,012	0
Prepaid expenses and other current assets	1,649,781	1,173,744
Total current assets	55,187,406	85,187,157
Investments	5,008,243	0
Property and equipment, net	245,425	191,385
Deposits	8,888	8,888
Total assets	60,449,962	85,387,430
Current Liabilities:
Accounts payable	2,337,367	1,945,575
Accrued expenses and other liabilities	7,173,987	2,320,587
Total current liabilities	9,511,354	4,266,162
Accrued expenses and other liabilities, non-current	154,799	157,456
Total liabilities	9,666,153	4,423,618
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized: none issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, $0.001 par value, 150,000,000 shares authorized; 102,739,257 shares and 102,549,498 shares issued and outstanding at December 31, 2018 and 2017, respectively	102,739	102,549
Additional paid-in capital	211,265,279	207,421,710
Accumulated deficit	(160,563,961)	(126,560,447)
Accumulated other comprehensive loss	(20,248)
Total stockholders' equity	50,783,809	80,963,812
Total liabilities and stockholders' equity	$ 60,449,962	$ 85,387,430

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 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	102,739,257	102,549,498
Common stock, shares outstanding	102,739,257	102,549,498

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues from collaborative arrangement	$ 500,000	$ 0
Operating costs and expenses:
Research and development	19,919,204	11,375,237
General and administrative	15,875,961	7,304,399
Total operating costs and expenses	35,795,165	18,679,636
Loss from operations	(35,295,165)	(18,679,636)
Other income, net	1,291,651	454,163
Change in fair value of warrants liability		(186,904)
Loss before income taxes	(34,003,514)	(18,412,377)
Provision for income taxes	0	0
Net loss	$ (34,003,514)	$ (18,412,377)
Net loss per share - basic and diluted	$ (0.33)	$ (0.21)
Weighted average shares outstanding - basic and diluted	102,633,884	85,802,487
Net loss	$ (34,003,514)	$ (18,412,377)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities	(20,248)
Comprehensive loss	$ (34,023,762)	$ (18,412,377)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning 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)
Issuance of common stock, net	10,549	3	10,546
Issuance of stock options for services	3,535,647		3,535,647
Exercise of stock options for common stock	297,563	187	297,376
Other comprehensive loss	(20,248)				$ (20,248)
Net loss	(34,003,514)			(34,003,514)
Ending Balance at Dec. 31, 2018	$ 50,783,809	$ 102,739	$ 211,265,279	$ (160,563,961)	$ (20,248)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net loss	$ (34,003,514)	$ (18,412,377)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	37,978	45,689
Stock-based compensation	3,550,644	2,407,961
Change in fair value of warrants liability		186,904
(Increase) decrease in:
Inventory	(56,012)
Prepaid expenses and other current assets and deposits	(476,037)	(125,800)
Increase (decrease) in:
Accounts payable	391,792	1,012,399
Accrued expenses and other liabilities	4,850,743	1,142,652
Net cash used in operating activities	(25,704,406)	(13,742,572)
Investing Activities:
Purchases of property and equipment	(92,018)
Purchases of investments	(36,802,418)	(3,958)
Proceeds from maturities of investments	21,368,425
Net cash provided by (used in) investing activities	(15,526,011)	(3,958)
Financing Activities:
Proceeds from issuance of common stock, net		53,772,560
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	297,563	368,185
Net cash provided by (used in) financing activities	293,115	57,350,168
Net increase (decrease) in cash and cash equivalents	(40,937,302)	43,603,638
Cash and cash equivalents - beginning of period	57,496,702	13,893,064
Cash and cash equivalents - end of period	16,559,400	57,496,702
Non-cash investing and financing activities:
Unrealized gain (loss) on available-for-sale securities	$ (20,248)
Exercise of liability classified warrants for common stock		$ 309,130

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2018
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), and MuSK antibody positive myasthenia gravis (MuSK-MG). On November 28, 2018, the U.S. Food and Drug Administration, or FDA, granted approval of Firdapse ® 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, 2018. The Company has been able to fund its cash needs to date primarily through public and private offerings of its securities. 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 from the issuance date of this Form 10-K. 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 Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies. a. PRINCIPLES OF CONSOLIDATION b. USE OF ESTIMATES. c. CASH AND CASH EQUIVALENTS. d. INVESTMENTS. Short-term bond fund The short-term bond fund is classified 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. At December 31, 2018 and 2017, the only investment classified as trading securities was the short-term bond fund. Unrealized gain (loss) on trading securities was ($29,430) and $29,430, respectively, for the years ended December 31, 2018, and 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 e. INVENTORY. first-in-first-out ® ® Products that have been approved by the FDA or other regulatory authorities, such as Firdapse ® ® The Company evaluates for potential excess inventory by analyzing current and future product demand relative to the remaining product shelf life. The Company builds demand forecasts by considering factors such as, but not limited to, overall market potential, market share, market acceptance, and patient usage. f. PREPAID EXPENSES AND OTHER CURRENT ASSETS. pre-commercialization g PROPERTY AND EQUIPMENT. h OPERATING LEASES. i. FAIR VALUE OF FINANCIAL INSTRUMENTS. j. 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 in Significant (Level 2) Significant (Level 3) Cash and cash equivalents: Money market funds $ 14,462,087 $ 14,462,087 $ — $ — Short-term investments: Short-term bond fund $ 26,541,349 $ 26,541,349 $ — $ — U.S. Treasuries $ 10,380,864 $ — $ 10,380,864 $ — Investments: U.S. Treasuries $ 5,008,243 $ — $ 5,008,243 $ — Balances as of Quoted Prices in Significant Significant (Level 3) 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 $ — $ — k. WARRANTS LIABILITY. The following table rolls forward the fair value of the Company’s warrants liability activity for the year ended December 31, 2017. On May 2, 2017, all outstanding and unexercised 2011 warrants expired. 2017 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 $ — During the year ended December 31, 2017, 613,913 of the 2011 warrants were exercised, with proceeds of $798,087 to the Company. l. REVENUES FROM COLLABORATIVE ARRANGEMENT ® Nonrefundable upfront license fees are recognized upon receipt as persuasive evidence of an arrangement exists, the price to the collaborator is fixed or determinable and collectability is reasonably assured. An upfront license fee of $500,000 was recognized in the year ended December 31, 2018 when it was paid following execution of the collaborative arrangement for vigabatrin tablets. Refer to Note 7, Collaborative Arrangement, for further discussion on the Company’s collaborative arrangement. m. RESEARCH AND DEVELOPMENT. n. STOCK-BASED COMPENSATION o. CONCENTRATION OF CREDIT RISK. p. INCOME TAXES 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 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 q. COMPREHENSIVE INCOME (LOSS). available-for-sale r. NET LOSS PER SHARE 2018 2017 Options to purchase common stock 10,532,500 5,191,666 Potential equivalent common stock excluded 10,532,500 5,191,666 Potentially dilutive stock options to purchase common stock as of December 31, 2018, had exercise prices ranging from $0.79 to $4.64. Potentially dilutive stock options to purchase common stock as of December 31, 2017 had exercise prices ranging from $0.47 to $4.64. s. SEGMENT INFORMATION. t. RECLASSIFICATIONS. u. 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 In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments

Investments

Investments	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	3. Investments. Available-for-sale Amortized Gross Gross Estimated At December 31, 2018: U.S. Treasuries – ST $ 10,382,699 $ — $ (1,835 ) $ 10,380,864 U.S. Treasuries – LT 5,026,656 — (18,413 ) 5,008,243 Total $ 15,409,355 $ — $ (20,248 ) $ 15,389,107 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” available-for-sale available-for-sale Certain U.S. Treasuries at December 31, 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, as of December 31, 2018, the Company did not consider these investments to be other-than-temporarily impaired. 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 December 31, 2018 was less than 12 months. The estimated fair values of available-for-sale 2018 Due in one year or less $ 10,380,864 Due after one year but within two years 5,008,243 $ 15,389,107

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2018
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: 2018 2017 Prepaid research fees $ 358,209 $ 388,977 Prepaid insurance 800,261 638,139 Prepaid pre-commercialization 17,030 65,000 Prepaid subscriptions fees 170,552 23,347 Prepaid rent 31,561 — Other 272,168 58,281 Total prepaid expenses and other current assets $ 1,649,781 $ 1,173,744

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2018
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: 2018 2017 Computer equipment $ 52,704 $ 27,915 Furniture and equipment 212,451 169,931 Leasehold improvements 177,417 152,708 442,572 350,554 Less: Accumulated depreciation (197,147 ) (159,169 ) Total property and equipment, net $ 245,425 $ 191,385 Depreciation expense was $37,978 and $45,689, respectively, for the years ended December 31, 2018 and 2017.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	12 Months Ended
	Dec. 31, 2018
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: 2018 2017 Accrued preclinical and clinical trial expenses $ 821,633 $ 970,649 Accrued professional fees 1,311,061 227,457 Accrued compensation and benefits 1,941,449 821,935 Accrued license fees 3,000,000 252,500 Deferred rent and lease incentive 33,408 24,011 Other 66,436 24,035 Current accrued expenses and other liabilities 7,173,987 2,320,587 Deferred rent and lease incentive – non-current 154,799 157,456 Non-current 154,799 157,456 Total accrued expenses and other liabilities $ 7,328,786 $ 2,478,043

Collaborative Arrangement

Collaborative Arrangement	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative Arrangement	7. Collaborative Arrangement. In December 2018, the Company entered into a collaboration and license agreement with Endo International plsc’s subsidiary, Endo Ventures Limited (EVL), for the further development and commercialization of generic Sabril ® EVL assumes all development, manufacturing, clinical, regulatory, sales and marketing costs under the collaboration, while the Company is responsible for exercising commercially reasonable efforts to develop, or cause the development of, a final finished, stable dosage form of generic Sabril ® Under the terms of the Collaboration, the Company has received an up-front mid-double ®

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies. The Company has contracted with drug manufacturers and other vendors, including clinical research organizations (CRO) overseeing one or more of 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. 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 operating lease agreements for its corporate office. The leases have free and escalating rent payment provisions. The Company recognizes rent expense under such leases on a straight-line basis over the term of the lease. As of December 31, 2018, future minimum lease payments under the operating lease agreements are as follows: 2019 $ 329,725 2020 339,612 2021 349,792 2022 329,662 $ 1,348,791 In August 2018, the Company entered into a fourth amendment to the lease to its corporate offices to obtain additional space for its operations. The Company now leases approximately 7,800 square feet and the lease term expires in November 2022. In connection with the expansion, approximately $13,000 of tenant build-out There are no obligations under capital leases. On August 27, 2009, the Company entered into a license agreement with Northwestern University (Northwestern), under which it acquired worldwide rights to CPP-115. In 2018, 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. 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 is vigorously defending itself against claims that Northwestern has brought against it in the arbitration proceeding. There can be no assurance as to the outcome of this matter. The Company has an employment agreement with its Chief Executive Officer. Under this agreement, the CEO received an annual base salary of approximately $525,000 in 2018. This agreement expires in November 2020.

Agreements

Agreements	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Agreements	9. Agreements. a. 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 ® ® Under the Company’s license agreement with BioMarin, the Company agreed to pay certain milestone payments that BioMarin was obligated to pay to both a third-party licensor of the rights that have been sublicensed to us and to the former stockholders of Huxley Pharmaceuticals (“Huxley”) under an earlier stock purchase agreement between BioMarin and the former Huxley stockholders. In full satisfaction of the milestone obligations, the Company has paid (i) $3,150,000 in milestone payments to the third party licensor of the rights that have been sublicensed to the Company ($3.0 million of which was paid in February 2019 and the balance of which was paid in 2018) and (ii) $2.0 million in milestone payments to the former Huxley Stockholders (all of which was paid in 2018). In the BioMarin License Agreement, the Company agreed to share in the cost of certain post-marketing studies of Firdapse ® b AGREEMENTS FOR DRUG DEVELOPMENT, PRECLINICAL AND CLINICAL STUDIES

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
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 21% to amounts included in the statements of operations is as follows: 2018 2017 Statutory rate 21.0 % 34.0 % State tax 4.2 % 3.5 % Valuation allowance (25.9 )% 26.5 % Federal rate change 0.0 % (73.2 )% Tax credit 1.4 % 6.8 % Other (0.7 )% 2.4 % 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, 2018 and 2017 are as follows: 2018 2017 Net operating loss $ 19,867,591 $ 15,718,570 Start-up 13,861,147 10,508,487 Tax credits 12,625,275 11,582,134 Deferred compensation 1,919,434 1,326,189 Other 109,779 72,395 Gross deferred tax asset 48,383,226 39,207,775 Valuation allowance (48,383,226 ) (39,207,775 ) Net deferred tax assets $ — $ — The Company’s deferred tax assets have been fully offset by a valuation allowance at December 31, 2018 and 2017 because the Company believes that it is more likely than not that the deferred tax asset will not be realized. The increase and decrease in the valuation allowance on the deferred tax assets was $9,175,451 and $3,388,951 for the years ended December 31, 2018 and 2017, respectively. At December 31, 2018 and 2017, respectively, the Company had net operating loss carryforwards of approximately $79.0 million and $62.6 million available to reduce future taxable income, if any. The net operating loss carryforwards will expire at various dates beginning in 2023 and ending in 2037, the amount of net operating loss generated in 2018 will have an infinite life, but will be limited to utilization per year of 80% of taxable income. 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 21% 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, 2018. 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 2015. The Company is not currently under income tax examinations by any tax authorities.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
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, 2018 and 2017. No shares of preferred stock were outstanding at December 31, 2018 and 2017. Common Stock The Company has 150,000,000 shares of authorized common stock, par value $0.001 per share. At December 31, 2018 and 2017, 102,739,257 and 102,549,498 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 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 December 31, 2018, there is approximately $92.5 million available for future sale under the 2017 Shelf Registration Statement. Warrant Exercises All unexercised warrants expired in 2017. For the year ended December 31, 2017, the Company issued 2,257,663 shares 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. 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 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 Stockholders 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.

Stock Compensation Plans

Stock Compensation Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation Plans	12. Stock Compensation Plans. For the years ended December 31, 2018 and 2017, the Company recorded stock-based compensation expense as follows: 2018 2017 Research and development $ 1,079,230 $ 785,899 General and administrative 2,471,414 1,622,062 Total stock-based compensation $ 3,550,644 $ 2,407,961 The Company may issue stock options, restricted stock, stock appreciation rights and restricted stock units (collectively, the “Awards”) to employees, directors, and consultants of the Company under the 2014 and 2018 Stock Incentive Plans (the 2014 Plan and the 2018 Plan or collectively, the Plans). At December 31, 2018, no shares remain available for future issuance under the 2014 Plan. Under the 2018 Plan, 7,500,000 shares were reserved for issuance and as of December 31, 2018, 3,620,603 shares remain available for future issuance. Stock Options The Company has granted stock options to employees, officers, directors, 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 5 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, 2018 and 2017, options to purchase 186,665 and 780,000 shares of the Company’s common stock were exercised with gross proceeds to the Company of $297,563 and $368,185, respectively. Further, during the year ended December 31, 2018, no options to purchase shares of the Company’s common stock were exercised on a “cashless” basis. During the year ended December 31, 2017, options to purchase 100,000 shares of the Company’s common stock were exercised on a “cashless” basis, resulting in the issuance of an aggregate of 84,280 shares of the Company’s common stock, respectively. During the years ended December 31, 2018 and 2017 the Company recorded non-cash During the years ended December 31, 2018 and 2017, the Company granted seven-year options to purchase an aggregate of 5,822,500 and 1,550,000 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, 2018 is summarized as follows: Number of Weighted Weighted Aggregate Outstanding at beginning of year 5,191,666 $ 1.96 Granted 5,822,500 3.04 Exercised or released (186,665 ) 1.59 Forfeited or cancelled (270,001 ) 2.94 Expired (25,000 ) 0.47 Outstanding at end of year 10,532,500 $ 2.54 5.39 $ 2,239,500 Exercisable at end of year 4,349,996 $ 2.16 4.00 $ 1,679,297 Other information pertaining to stock option activity during the years ended December 31, 2018 and 2017 was as follows: 2018 2017 Weighted–average fair value of granted stock options $ 1.93 $ 0.91 Total fair value of vested stock options $ 2,193,294 $ 2,016,992 Total intrinsic value of exercised stock options $ 274,864 $ 2,296,100 The following table summarizes information about the Company’s options outstanding at December 31, 2018: Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted Weighted Number Weighted Weighted $0.79 to $1.13 2,385,000 4.78 $ 0.99 1,686,664 4.69 $ 0.93 $1.14 to $2.28 2,440,000 6.87 $ 2.22 209,999 6.22 $ 2.07 $2.29 to $3.07 1,765,000 4.84 $ 2.60 1,098,333 3.72 $ 2.53 $3.08 to $3.75 2,005,000 4.59 $ 3.30 995,000 2.71 $ 3.14 $3.76 to $4.64 1,937,500 5.62 $ 4.03 360,000 3.92 $ 4.11 10,532,500 5.39 $ 2.54 4,349,996 4.00 $ 2.16 As of December 31, 2018, there was approximately $8.8 million of unrecognized compensation expense related to non-vested 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. mid-point Assumptions used during the years were as follows: December 31, December 31, Risk free interest rate 2.09% to 2.88% 1.66% to 2.25% Expected term 0 to 7 years 4 to 7 years Expected volatility 82% 104% Expected dividend yield — % — % Expected forfeiture rate — % — % Restricted Stock Units Under the 2018 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 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. No restricted stock units were granted during 2018. Restricted stock unit activity during 2017 was as follows: 2017 Number of Restricted Weighted Average Nonvested balance at beginning of year 26,667 $ 2.83 Granted — — Vested (26,667 ) 2.83 Forfeited — — Nonvested balance at end of year — $ — No stock-based compensation related to restricted stocks was recorded during 2018. During the year ended December 31, 2017, the Company recorded non-cash Common Stock During the year ended December 31, 2018, the Company granted 3,094 net shares of common stock to an employee as compensation. The Company recorded stock-based compensation related to common stock issued to an employee totaling approximately $15,000, during the year ended December 31, 2018. No shares of common stock were granted during the year ended December 31, 2017.

Benefit Plan

Benefit Plan	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Benefit Plan	13. Benefit Plan. The Company maintains an employee savings plan pursuant to Section 401(k) of the Internal Revenue Code covering all eligible employees. Subject to certain dollar limits, eligible employees may contribute up to 15% of their pre-tax

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2018
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, 2018 and 2017: Quarter Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Revenues $ — $ — $ — $ 500,000 Loss from operations $ (5,933,440 ) $ (6,335,855 ) $ (8,182,603 ) $ (14,843,267 ) Net loss $ (5,699,892 ) $ (5,965,140 ) $ (7,838,873 ) $ (14,499,609 ) Net loss per share – basic and diluted $ (0.06 ) $ (0.06 ) $ (0.08 ) $ (0.14 ) 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 ) 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.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	15. Subsequent Events. On January 15, 2019, the Company launched its first product, Firdapse ®

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
PRINCIPLES OF CONSOLIDATION.	a. PRINCIPLES OF CONSOLIDATION
USE OF ESTIMATES	b. USE OF ESTIMATES.
CASH AND CASH EQUIVALENTS	c. CASH AND CASH EQUIVALENTS.
INVESTMENTS	d. INVESTMENTS. Short-term bond fund The short-term bond fund is classified 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. At December 31, 2018 and 2017, the only investment classified as trading securities was the short-term bond fund. Unrealized gain (loss) on trading securities was ($29,430) and $29,430, respectively, for the years ended December 31, 2018, and 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
INVENTORY	e. INVENTORY. first-in-first-out ® ® Products that have been approved by the FDA or other regulatory authorities, such as Firdapse ® ® The Company evaluates for potential excess inventory by analyzing current and future product demand relative to the remaining product shelf life. The Company builds demand forecasts by considering factors such as, but not limited to, overall market potential, market share, market acceptance, and patient usage.
PREPAID EXPENSES AND OTHER CURRENT ASSETS	f. PREPAID EXPENSES AND OTHER CURRENT ASSETS. pre-commercialization
PROPERTY AND EQUIPMENT	g PROPERTY AND EQUIPMENT.
OPERATING LEASES	h OPERATING LEASES.
FAIR VALUE OF FINANCIAL INSTRUMENTS	i. FAIR VALUE OF FINANCIAL INSTRUMENTS.
FAIR VALUE MEASUREMENTS	j. 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 in Significant (Level 2) Significant (Level 3) Cash and cash equivalents: Money market funds $ 14,462,087 $ 14,462,087 $ — $ — Short-term investments: Short-term bond fund $ 26,541,349 $ 26,541,349 $ — $ — U.S. Treasuries $ 10,380,864 $ — $ 10,380,864 $ — Investments: U.S. Treasuries $ 5,008,243 $ — $ 5,008,243 $ — Balances as of Quoted Prices in Significant Significant (Level 3) 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	k. WARRANTS LIABILITY. The following table rolls forward the fair value of the Company’s warrants liability activity for the year ended December 31, 2017. On May 2, 2017, all outstanding and unexercised 2011 warrants expired. 2017 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 $ — During the year ended December 31, 2017, 613,913 of the 2011 warrants were exercised, with proceeds of $798,087 to the Company.
REVENUES FROM COLLABORATIVE ARRANGEMENT	l. REVENUES FROM COLLABORATIVE ARRANGEMENT ® Nonrefundable upfront license fees are recognized upon receipt as persuasive evidence of an arrangement exists, the price to the collaborator is fixed or determinable and collectability is reasonably assured. An upfront license fee of $500,000 was recognized in the year ended December 31, 2018 when it was paid following execution of the collaborative arrangement for vigabatrin tablets. Refer to Note 7, Collaborative Arrangement, for further discussion on the Company’s collaborative arrangement.
RESEARCH AND DEVELOPMENT	m. RESEARCH AND DEVELOPMENT.
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION
CONCENTRATION OF CREDIT RISK	o. CONCENTRATION OF CREDIT RISK.
INCOME TAXES	p. INCOME TAXES 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 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
COMPREHENSIVE INCOME (LOSS)	COMPREHENSIVE INCOME (LOSS). available-for-sale
NET LOSS PER SHARE	r. NET LOSS PER SHARE 2018 2017 Options to purchase common stock 10,532,500 5,191,666 Potential equivalent common stock excluded 10,532,500 5,191,666 Potentially dilutive stock options to purchase common stock as of December 31, 2018, had exercise prices ranging from $0.79 to $4.64. Potentially dilutive stock options to purchase common stock as of December 31, 2017 had exercise prices ranging from $0.47 to $4.64.
SEGMENT INFORMATION	s. SEGMENT INFORMATION.
RECLASSIFICATIONS	t. RECLASSIFICATIONS.
RECENTLY ISSUED ACCOUNTING STANDARDS	u. 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 In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 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 in Significant (Level 2) Significant (Level 3) Cash and cash equivalents: Money market funds $ 14,462,087 $ 14,462,087 $ — $ — Short-term investments: Short-term bond fund $ 26,541,349 $ 26,541,349 $ — $ — U.S. Treasuries $ 10,380,864 $ — $ 10,380,864 $ — Investments: U.S. Treasuries $ 5,008,243 $ — $ 5,008,243 $ — Balances as of Quoted Prices in Significant Significant (Level 3) 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 $ — $ —
Summary of Company's Warrants Liability Activity	The following table rolls forward the fair value of the Company’s warrants liability activity for the year ended December 31, 2017. On May 2, 2017, all outstanding and unexercised 2011 warrants expired. 2017 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 $ —
Potential Shares Excluded from Determination of Basic and Diluted Net Loss Per Share	r. NET LOSS PER SHARE 2018 2017 Options to purchase common stock 10,532,500 5,191,666 Potential equivalent common stock excluded 10,532,500 5,191,666

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Investments by Security type	Available-for-sale Amortized Gross Gross Estimated At December 31, 2018: U.S. Treasuries – ST $ 10,382,699 $ — $ (1,835 ) $ 10,380,864 U.S. Treasuries – LT 5,026,656 — (18,413 ) 5,008,243 Total $ 15,409,355 $ — $ (20,248 ) $ 15,389,107
Estimated Fair Values of Available for Sale Securities	The estimated fair values of available-for-sale 2018 Due in one year or less $ 10,380,864 Due after one year but within two years 5,008,243 $ 15,389,107

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following as of December 31: 2018 2017 Prepaid research fees $ 358,209 $ 388,977 Prepaid insurance 800,261 638,139 Prepaid pre-commercialization 17,030 65,000 Prepaid subscriptions fees 170,552 23,347 Prepaid rent 31,561 — Other 272,168 58,281 Total prepaid expenses and other current assets $ 1,649,781 $ 1,173,744

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and equipment, net consists of the following as of December 31: 2018 2017 Computer equipment $ 52,704 $ 27,915 Furniture and equipment 212,451 169,931 Leasehold improvements 177,417 152,708 442,572 350,554 Less: Accumulated depreciation (197,147 ) (159,169 ) Total property and equipment, net $ 245,425 $ 191,385

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following as of December 31: 2018 2017 Accrued preclinical and clinical trial expenses $ 821,633 $ 970,649 Accrued professional fees 1,311,061 227,457 Accrued compensation and benefits 1,941,449 821,935 Accrued license fees 3,000,000 252,500 Deferred rent and lease incentive 33,408 24,011 Other 66,436 24,035 Current accrued expenses and other liabilities 7,173,987 2,320,587 Deferred rent and lease incentive – non-current 154,799 157,456 Non-current 154,799 157,456 Total accrued expenses and other liabilities $ 7,328,786 $ 2,478,043

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments under Operating Lease Agreement	As of December 31, 2018, future minimum lease payments under the operating lease agreements are as follows: 2019 $ 329,725 2020 339,612 2021 349,792 2022 329,662 $ 1,348,791

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
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 21% to amounts included in the statements of operations is as follows: 2018 2017 Statutory rate 21.0 % 34.0 % State tax 4.2 % 3.5 % Valuation allowance (25.9 )% 26.5 % Federal rate change 0.0 % (73.2 )% Tax credit 1.4 % 6.8 % Other (0.7 )% 2.4 % 0.0 % 0.0 %
Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets as of December 31, 2018 and 2017 are as follows: 2018 2017 Net operating loss $ 19,867,591 $ 15,718,570 Start-up 13,861,147 10,508,487 Tax credits 12,625,275 11,582,134 Deferred compensation 1,919,434 1,326,189 Other 109,779 72,395 Gross deferred tax asset 48,383,226 39,207,775 Valuation allowance (48,383,226 ) (39,207,775 ) Net deferred tax assets $ — $ —

Stock Compensation Plans (Table

Stock Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense	For the years ended December 31, 2018 and 2017, the Company recorded stock-based compensation expense as follows: 2018 2017 Research and development $ 1,079,230 $ 785,899 General and administrative 2,471,414 1,622,062 Total stock-based compensation $ 3,550,644 $ 2,407,961
Stock option activity under the Company's Plans	Stock option activity under the Company’s Plans for the year ended December 31, 2018 is summarized as follows: Number of Weighted Weighted Aggregate Outstanding at beginning of year 5,191,666 $ 1.96 Granted 5,822,500 3.04 Exercised or released (186,665 ) 1.59 Forfeited or cancelled (270,001 ) 2.94 Expired (25,000 ) 0.47 Outstanding at end of year 10,532,500 $ 2.54 5.39 $ 2,239,500 Exercisable at end of year 4,349,996 $ 2.16 4.00 $ 1,679,297
Schedule of Other Information Pertaining to Stock Option Activity	Other information pertaining to stock option activity during the years ended December 31, 2018 and 2017 was as follows: 2018 2017 Weighted–average fair value of granted stock options $ 1.93 $ 0.91 Total fair value of vested stock options $ 2,193,294 $ 2,016,992 Total intrinsic value of exercised stock options $ 274,864 $ 2,296,100
Summary of Company's Stock Options Outstanding	The following table summarizes information about the Company’s options outstanding at December 31, 2018: Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted Weighted Number Weighted Weighted $0.79 to $1.13 2,385,000 4.78 $ 0.99 1,686,664 4.69 $ 0.93 $1.14 to $2.28 2,440,000 6.87 $ 2.22 209,999 6.22 $ 2.07 $2.29 to $3.07 1,765,000 4.84 $ 2.60 1,098,333 3.72 $ 2.53 $3.08 to $3.75 2,005,000 4.59 $ 3.30 995,000 2.71 $ 3.14 $3.76 to $4.64 1,937,500 5.62 $ 4.03 360,000 3.92 $ 4.11 10,532,500 5.39 $ 2.54 4,349,996 4.00 $ 2.16
Summary of Stock Options Awards Based on Certain Assumptions	Assumptions used during the years were as follows: December 31, December 31, Risk free interest rate 2.09% to 2.88% 1.66% to 2.25% Expected term 0 to 7 years 4 to 7 years Expected volatility 82% 104% Expected dividend yield — % — % Expected forfeiture rate — % — %
Summary of Restricted Stock Unit Activity	Restricted stock unit activity during 2017 was as follows: 2017 Number of Restricted Weighted Average Nonvested balance at beginning of year 26,667 $ 2.83 Granted — — Vested (26,667 ) 2.83 Forfeited — — Nonvested balance at end of year — $ —

Quarterly Financial Informati_2

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 and 2017: Quarter Ended March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Revenues $ — $ — $ — $ 500,000 Loss from operations $ (5,933,440 ) $ (6,335,855 ) $ (8,182,603 ) $ (14,843,267 ) Net loss $ (5,699,892 ) $ (5,965,140 ) $ (7,838,873 ) $ (14,499,609 ) Net loss per share – basic and diluted $ (0.06 ) $ (0.06 ) $ (0.08 ) $ (0.14 ) 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 )

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)	Jan. 01, 2019USD ($)	Oct. 31, 2011shares	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)Segment$ / shares	Dec. 31, 2017USD ($)$ / sharesshares
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Maximum maturity period of cash and cash equivalent				Three months
Inventory			$ 56,012	$ 56,012	$ 0
Deferred rent and lease incentive in accrued expenses and other liabilities			188,207	188,207	181,467
Proceeds of Warrants					3,209,423
Upfront license fees			$ 500,000	$ 500,000	$ 0
Statutory rate				21.00%	34.00%
Stock option exercise price range, Minimum | $ / shares				$ 0.79	$ 0.47
Stock option exercise price range, Maximum | $ / shares				$ 4.64	$ 4.64
Number of reportable segment | Segment				1
Lease Expiration Date				Nov. 30, 2022
U.S. federal corporate tax rate [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Statutory rate					35.00%
Furniture and Equipment [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets				5 years
Subsequent Event [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Additional assets	$ 1,000,000
Corresponding liability	$ 1,500,000
October 28, 2011 Warrants [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Warrants issued in offering | shares		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
Number of warrants exercised during the period | shares					613,913
Proceeds of Warrants					$ 798,087
Other Income, Net [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Unrealized gain(loss),trading securities				$ (29,430)	$ 29,430
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
Minimum [Member] | Leasehold Improvements [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets				4 years
Minimum [Member] | Computer 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				5 years
Maximum [Member] | Leasehold Improvements [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets				7 years
Maximum [Member] | Computer Equipment [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful life of assets				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 ($)	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 5,008,243	$ 0
Short-Term Bond Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	26,541,349	26,516,711
U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Fair Value Disclosure	10,380,864
Investments	5,008,243
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	14,462,087	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	26,541,349	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	14,462,087	$ 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	10,380,864
Investments	$ 5,008,243

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies - Summary of Company's Warrants Liability Activity (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value Disclosures [Abstract]
Fair value, beginning of period	$ 122,226
Issuance of warrants	0
Exercise of warrants	(309,130)
Change in fair value	186,904
Fair value, end of period	$ 0

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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	10,532,500	5,191,666
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential equivalent common stock excluded	10,532,500	5,191,666

Investment - Summary of Availab

Investment - Summary of Available-for-Sale Investments by Security type (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
Net Investment Income [Line Items]
Amortized cost	$ 15,409,355
Gross Unrealized Gains	0
Gross Unrealized Losses	(20,248)
Estimated Fair Value	15,389,107
U.S. Treasuries - ST [Member]
Net Investment Income [Line Items]
Amortized cost	10,382,699
Gross Unrealized Gains	0
Gross Unrealized Losses	(1,835)
Estimated Fair Value	10,380,864
U.S. Treasuries - LT [Member]
Net Investment Income [Line Items]
Amortized cost	5,026,656
Gross Unrealized Gains	0
Gross Unrealized Losses	(18,413)
Estimated Fair Value	$ 5,008,243

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 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)	Dec. 31, 2018USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 10,380,864
Due after one year but within two years	5,008,243
Estimated Fair Value	$ 15,389,107

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research fees	$ 358,209	$ 388,977
Prepaid insurance	800,261	638,139
Prepaid pre-commercialization fees	17,030	65,000
Prepaid subscriptions fees	170,552	23,347
Prepaid rent	31,561
Other	272,168	58,281
Total prepaid expenses and other current assets	$ 1,649,781	$ 1,173,744

Property and Equipment, Net - P

Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 442,572	$ 350,554
Less: Accumulated depreciation	(197,147)	(159,169)
Total property and equipment, net	245,425	191,385
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	52,704	27,915
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	212,451	169,931
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 177,417	$ 152,708

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 37,978	$ 45,689

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued preclinical and clinical trial expenses	$ 821,633	$ 970,649
Accrued professional fees	1,311,061	227,457
Accrued compensation and benefits	1,941,449	821,935
Accrued license fees	3,000,000	252,500
Deferred rent and lease incentive	33,408	24,011
Other	66,436	24,035
Current accrued expenses and other liabilities	7,173,987	2,320,587
Deferred rent and lease incentive - non-current	154,799	157,456
Non-current accrued expenses and other liabilities	154,799	157,456
Total accrued expenses and other liabilities	$ 7,328,786	$ 2,478,043

Collaborative Arrangement - Add

Collaborative Arrangement - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Collaboration Arrangement Disclosure [Abstract]
Upfront license fee	$ 500,000	$ 500,000	$ 0
Period of collaboration agreement		10 years

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Lease Payments under Operating Lease Agreement (Detail)	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 329,725
2020	339,612
2021	349,792
2022	329,662
Total	$ 1,348,791

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Aug. 31, 2018USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Commitments [Line Items]
Area of leased property | ft²	7,800
Lease expiration date	2022-11
Tenant build-out costs	$ 13,000
Rent expense		$ 242,155	$ 204,170
Obligations under capital leases		0
Accrued license fees		3,000,000	$ 252,500
CEO Employment Agreement [Member]
Commitments [Line Items]
Annual base salary of CEO		$ 525,000
Expiration date of employment agreement		2020-11
Northwestern License Agreement [Member]
Commitments [Line Items]
License fee paid		$ 424,885
Accrued license fees		$ 0

Agreements - Additional Informa

Agreements - Additional Information (Detail) - License Agreement with BioMarin [Member] - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2019	Dec. 31, 2018
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
Third Party Licensor [Member]
License Agreement [Line Items]
Milestone payment due		3,150,000
Third Party Licensor [Member] | Subsequent Event [Member]
License Agreement [Line Items]
Milestone payment due	$ 3,000,000
Huxley [Member]
License Agreement [Line Items]
Milestone payment due		$ 2,000,000
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%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	34.00%
Increase (decrease) in valuation allowance on deferred tax assets	$ 9,175,451	$ (3,388,951)
Net operating loss carryforwards	$ 79,000,000	$ 62,600,000
Net operating loss carryforwards expiration date	Beginning in 2023 and ending in 2037
Effective tax rate	0.00%	0.00%
Percentage of limited utilization of taxable income per year	80.00%
Interest or penalties accrued	$ 0

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax Expense (Benefit) Computed at Statutory Federal Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	34.00%
State tax	4.20%	3.50%
Valuation allowance	(25.90%)	26.50%
Federal rate change	0.00%	(73.20%)
Tax credit	1.40%	6.80%
Other	(0.70%)	2.40%
Reconciliation of income tax expense (benefit)	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Tax Assets [Abstract]
Net operating loss	$ 19,867,591	$ 15,718,570
Start-up cost	13,861,147	10,508,487
Tax credits	12,625,275	11,582,134
Deferred compensation	1,919,434	1,326,189
Other	109,779	72,395
Gross deferred tax asset	48,383,226	39,207,775
Valuation allowance	(48,383,226)	(39,207,775)
Net deferred tax assets	$ 0	$ 0

Stockholders' Equity (Preferred

Stockholders' Equity (Preferred Stock and Common Stock) - Additional Information (Detail)	Dec. 31, 2018Vote$ / sharesshares	Dec. 31, 2017$ / sharesshares
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
Common stock, par value | $ / shares	$ 0.001	$ 0.001
Common stock, shares issued	102,739,257	102,549,498
Common stock, shares outstanding	102,739,257	102,549,498
Number of votes entitled for each share of common stock | Vote	1

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	Dec. 31, 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

Stockholders' Equity (Warrant E

Stockholders' Equity (Warrant Exercises) - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)shares
Equity [Abstract]
Issuance of common stock for warrant exercises | shares	2,257,663
Proceeds from exercise of warrants | $	$ 3,209,423

Stockholders' Equity (Stockhold

Stockholders' Equity (Stockholder Rights Plan) - Additional Information (Detail) - $ / shares	Sep. 19, 2016	Sep. 20, 2011	Dec. 31, 2018
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 - Stoc

Stock Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 3,550,644	$ 2,407,961
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	1,079,230	785,899
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 2,471,414	$ 1,622,062

Stock Compensation Plans - Addi

Stock Compensation Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual term	4 years
Number of stock options exercised	186,665
Proceeds from exercise of stock options	$ 297,563	$ 368,185
Common stock unit granted	5,822,500	0
Expected dividend rate	0.00%	0.00%
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 15,000
Common stock unit granted	3,094
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	5 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	$ 0	$ 65,336
2014 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 Eighteen 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	7,500,000
Common stock shares available for future issuance under the Plan	3,620,603
Two Thousand Eighteen Stock Incentive Plan [Member] | Restricted Stock Units (RSUs) [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	186,665	780,000
Proceeds from exercise of stock options	$ 297,563	$ 368,185
Non-cash stock-based compensation expense	$ 3,535,647	$ 2,342,625
Stock option granted, contractual term	7 years	7 years
Common stock unit granted	5,822,500	1,550,000
Unrecognized compensation expense related to non-vested stock compensation awards granted under the Plan	$ 8,800,000
Expected remaining weighted average vesting period	2 years 6 months 29 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	0	100,000
Shares issued for cashless option exercise		84,280

Stock Compensation Plans - Summ

Stock Compensation Plans - Summary of Stock Option Activity under the Company's Plan (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Outstanding at beginning of year	5,191,666
Number of options, Granted	5,822,500	0
Number of options, Exercised or released	(186,665)
Number of options, Forfeited or cancelled	(270,001)
Number of options, Expired	(25,000)
Number of options, Outstanding at end of year	10,532,500	5,191,666
Number of options, Exercisable at end of year	4,349,996
Weighted average exercise price, Outstanding at beginning of year	$ 1.96
Weighted average exercise price, Granted	3.04
Weighted average exercise price, Exercised or released	1.59
Weighted average exercise price, Forfeited or cancelled	2.94
Weighted average exercise price, Expired	0.47
Weighted average exercise price, Outstanding at end of year	2.54	$ 1.96
Weighted average exercise price, Exercisable at end of year	$ 2.16
Weighted Average Remaining Contractual Term (Years), Outstanding at end of year	5 years 4 months 20 days
Weighted Average Remaining Contractual Term (Years), Exercisable at end of year	4 years
Aggregate Intrinsic value, Outstanding at end of year	$ 2,239,500
Aggregate Intrinsic value, Exercisable at end of year	$ 1,679,297

Stock Compensation Plans - Sche

Stock Compensation Plans - Schedule of Other Information Pertaining to Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-average fair value of granted stock options	$ 1.93	$ 0.91
Total fair value of vested stock options	$ 2,193,294	$ 2,016,992
Total intrinsic value of exercised stock options	$ 274,864	$ 2,296,100

Stock Compensation Plans - Su_2

Stock Compensation Plans - Summary of Company's Stock Options Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	$ 0.79	$ 0.47
Range of Exercise Prices Upper Range	$ 4.64	$ 4.64
Number Outstanding, Options Outstanding	10,532,500
Weighted Average Remaining Contractual Life (Years), Options Outstanding	5 years 4 months 20 days
Weighted Average Exercise Price, Options Outstanding	$ 2.54
Number Exercisable Options Exercisable	4,349,996
Weighted Average Remaining Contractual Life (Years), Options Exercisable	4 years
Weighted Average Exercise Price, Options Exercisable	$ 2.16
$0.79 to $1.13 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	0.79
Range of Exercise Prices Upper Range	$ 1.13
Number Outstanding, Options Outstanding	2,385,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 9 months 10 days
Weighted Average Exercise Price, Options Outstanding	$ 0.99
Number Exercisable Options Exercisable	1,686,664
Weighted Average Remaining Contractual Life (Years), Options Exercisable	4 years 8 months 8 days
Weighted Average Exercise Price, Options Exercisable	$ 0.93
$1.14 to $2.28 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	1.14
Range of Exercise Prices Upper Range	$ 2.28
Number Outstanding, Options Outstanding	2,440,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	6 years 10 months 13 days
Weighted Average Exercise Price, Options Outstanding	$ 2.22
Number Exercisable Options Exercisable	209,999
Weighted Average Remaining Contractual Life (Years), Options Exercisable	6 years 2 months 19 days
Weighted Average Exercise Price, Options Exercisable	$ 2.07
$2.29 to $3.07 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	2.29
Range of Exercise Prices Upper Range	$ 3.07
Number Outstanding, Options Outstanding	1,765,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 10 months 2 days
Weighted Average Exercise Price, Options Outstanding	$ 2.60
Number Exercisable Options Exercisable	1,098,333
Weighted Average Remaining Contractual Life (Years), Options Exercisable	3 years 8 months 19 days
Weighted Average Exercise Price, Options Exercisable	$ 2.53
$3.08 to $3.75 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	3.08
Range of Exercise Prices Upper Range	$ 3.75
Number Outstanding, Options Outstanding	2,005,000
Weighted Average Remaining Contractual Life (Years), Options Outstanding	4 years 7 months 2 days
Weighted Average Exercise Price, Options Outstanding	$ 3.30
Number Exercisable Options Exercisable	995,000
Weighted Average Remaining Contractual Life (Years), Options Exercisable	2 years 8 months 15 days
Weighted Average Exercise Price, Options Exercisable	$ 3.14
$3.76 to $4.64 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices Lower Range	3.76
Range of Exercise Prices Upper Range	$ 4.64
Number Outstanding, Options Outstanding	1,937,500
Weighted Average Remaining Contractual Life (Years), Options Outstanding	5 years 7 months 13 days
Weighted Average Exercise Price, Options Outstanding	$ 4.03
Number Exercisable Options Exercisable	360,000
Weighted Average Remaining Contractual Life (Years), Options Exercisable	3 years 11 months 1 day
Weighted Average Exercise Price, Options Exercisable	$ 4.11

Stock Compensation Plans - Su_3

Stock Compensation Plans - Summary of Stock Options Awards Based on Certain Assumptions (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, Minimum	2.09%	1.66%
Risk free interest rate, Maximum	2.88%	2.25%
Expected volatility	82.00%	104.00%
Expected dividend yield	0.00%	0.00%
Expected forfeiture rate	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	0 years	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	7 years	7 years

Stock Compensation Plans - Su_4

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

Benefit Plan - Additional Infor

Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
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	$ 123,000	$ 84,000

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) - Schedule of Quarterly Financial Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 500,000								$ 500,000	$ 0
Loss from operations	(14,843,267)	$ (8,182,603)	$ (6,335,855)	$ (5,933,440)	$ (5,511,786)	$ (4,306,708)	$ (4,181,271)	$ (4,679,871)	(35,295,165)	(18,679,636)
Change in fair value of warrants liability							210,331	(397,235)		(186,904)
Net loss	$ (14,499,609)	$ (7,838,873)	$ (5,965,140)	$ (5,699,892)	$ (5,387,698)	$ (4,177,649)	$ (3,879,901)	$ (4,967,129)	$ (34,003,514)	$ (18,412,377)
Net loss per share - basic and diluted	$ (0.14)	$ (0.08)	$ (0.06)	$ (0.06)	$ (0.06)	$ (0.05)	$ (0.05)	$ (0.06)	$ (0.33)	$ (0.21)