Verrica Pharmaceuticals (VRCA) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 05, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	VRCA
Entity Registrant Name	Verrica Pharmaceuticals Inc.
Entity Central Index Key	0001660334
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		25,741,297
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transaction Period	true
Entity File Number	001-38529
Entity Tax Identification Number	463137900
Entity Address, Address Line One	10 North High Street
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	West Chester
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19380
City Area Code	484
Local Phone Number	453-3300

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 19,852,000	$ 10,271,000
Marketable securities	58,902,000	79,538,000
Prepaid expenses and other assets	985,000	1,343,000
Total current assets	79,739,000	91,152,000
Property, plant and equipment, net	1,252,000	255,000
Operating lease right-of-use asset	245,000
Deposits	14,000	499,000
Total assets	81,250,000	91,906,000
Current liabilities:
Accounts payable	1,467,000	922,000
Accrued expenses	2,684,000	1,517,000
Accounts payable and accrued expenses - related party	6,000	38,000
Operating lease liability	124,000
Total current liabilities	4,281,000	2,477,000
Operating lease liability	124,000
Total liabilities	4,405,000	2,477,000
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of June 30, 2019 and December 31, 2018
Common stock, $0.0001 par value; 200,000,000 authorized as of June 30, 2019 and December 31, 2018; 25,845,441 shares issued and 25,740,297 shares outstanding as of June 30, 2019 and 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018	3,000	3,000
Treasury stock, at cost, 105,144 shares as of June 30, 2019 and December 31, 2018	0	0
Additional paid-in capital	124,269,000	122,526,000
Accumulated deficit	(47,465,000)	(33,083,000)
Accumulated other comprehensive gain (loss)	38,000	(17,000)
Total stockholders’ equity	76,845,000	89,429,000
Total liabilities and stockholders’ equity	$ 81,250,000	$ 91,906,000

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	25,845,441	25,809,900
Common stock, shares outstanding	25,740,297	25,704,756
Treasury stock, shares	105,144	105,144

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 3,928	$ 3,515	$ 8,415	$ 4,442
General and administrative	3,593	1,955	7,132	2,916
Total operating expenses	7,521	5,470	15,547	7,358
Loss from operations	(7,521)	(5,470)	(15,547)	(7,358)
Other income (expense):
Interest income	523	153	1,070	194
Other expense	(3)		(3)
Total other income (expense)	520	153	1,067	194
Net loss	$ (7,001)	$ (5,317)	$ (14,480)	$ (7,164)
Net loss per share, basic and diluted	$ (0.28)	$ (0.92)	$ (0.58)	$ (1.66)
Weighted average common shares outstanding, basic and diluted	24,875,573	5,751,326	24,866,721	4,308,996
Net loss	$ (7,001)	$ (5,317)	$ (14,480)	$ (7,164)
Other comprehensive gain:
Unrealized gain on marketable securities	27		55
Comprehensive loss	$ (6,974)	$ (5,317)	$ (14,425)	$ (7,164)

CONDENSED STATEMENTS OF CONVERT

CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series C Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]
Beginning Balance at Dec. 31, 2017	$ (7,041)					$ 5,394	$ (12,435)
Beginning Balance (shares) at Dec. 31, 2017		21,302,972	1,937,984
Beginning Balance at Dec. 31, 2017		$ 10,508	$ 5,000
Beginning Balance (shares) at Dec. 31, 2017					3,804,643			105,144
Stock-based compensation	135					135
Series C convertible preferred stock				$ 21,000
Series C convertible preferred stock (shares)				4,606,267
Issuance costs for Series C preferred stock				$ (7)
Net loss	(1,847)						(1,847)
Ending Balance at Mar. 31, 2018	(8,753)					5,529	(14,282)
Ending Balance (Shares) at Mar. 31, 2018		21,302,972	1,937,984	4,606,267
Ending Balance at Mar. 31, 2018		$ 10,508	$ 5,000	$ 20,993
Ending Balance (Shares) at Mar. 31, 2018					3,804,643			105,144
Beginning Balance at Dec. 31, 2017	(7,041)					5,394	(12,435)
Beginning Balance (shares) at Dec. 31, 2017		21,302,972	1,937,984
Beginning Balance at Dec. 31, 2017		$ 10,508	$ 5,000
Beginning Balance (shares) at Dec. 31, 2017					3,804,643			105,144
Net loss	(7,164)
Ending Balance at Jun. 30, 2018	101,591				$ 3	121,187	(19,599)
Ending Balance (Shares) at Jun. 30, 2018					25,801,515			105,144
Beginning Balance at Mar. 31, 2018	(8,753)					5,529	(14,282)
Beginning Balance (shares) at Mar. 31, 2018		21,302,972	1,937,984	4,606,267
Beginning Balance at Mar. 31, 2018		$ 10,508	$ 5,000	$ 20,993
Beginning Balance (shares) at Mar. 31, 2018					3,804,643			105,144
Stock-based compensation	779					779
Conversion of preferred stock into common stock	36,501	$ (10,508)	$ (5,000)	$ (20,993)	$ 2	36,499
Conversion of preferred stock into common stock (shares)		(21,302,972)	(1,937,984)	(4,606,267)	16,246,872
Issuance of common stock in connection with IPO, net of offering costs	78,381				$ 1	78,380
Issuance of common stock in connection with IPO, net of offering costs (shares)					5,750,000
Net loss	(5,317)						(5,317)
Ending Balance at Jun. 30, 2018	101,591				$ 3	121,187	(19,599)
Ending Balance (Shares) at Jun. 30, 2018					25,801,515			105,144
Beginning Balance at Dec. 31, 2018	89,429				$ 3	122,526	(33,083)		$ (17)
Beginning Balance (shares) at Dec. 31, 2018					25,809,900			105,144
Stock-based compensation	780					780
Exercise of stock options	3					3
Exercise of stock options (in shares)					3,729
Unrealized gain on marketable securities	28								28
Net loss	(7,479)						(7,479)
Adoption of ASU 2018-07 (See Note 2)						(98)	98
Ending Balance at Mar. 31, 2019	82,761				$ 3	123,211	(40,464)		11
Ending Balance (Shares) at Mar. 31, 2019					25,813,629			105,144
Beginning Balance at Dec. 31, 2018	$ 89,429				$ 3	122,526	(33,083)		(17)
Beginning Balance (shares) at Dec. 31, 2018					25,809,900			105,144
Exercise of stock options (in shares)	35,541
Unrealized gain on marketable securities	$ 55
Net loss	(14,480)
Ending Balance at Jun. 30, 2019	76,845				$ 3	124,269	(47,465)		38
Ending Balance (Shares) at Jun. 30, 2019					25,845,441			105,144
Beginning Balance at Mar. 31, 2019	82,761				$ 3	123,211	(40,464)		11
Beginning Balance (shares) at Mar. 31, 2019					25,813,629			105,144
Stock-based compensation	846					846
Exercise of stock options	212					212
Exercise of stock options (in shares)					31,812
Unrealized gain on marketable securities	27								27
Net loss	(7,001)						(7,001)
Ending Balance at Jun. 30, 2019	$ 76,845				$ 3	$ 124,269	$ (47,465)		$ 38
Ending Balance (Shares) at Jun. 30, 2019					25,845,441			105,144

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net loss	$ (14,480)	$ (7,164)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,626	914
Accretion of discounts on marketable securities	(642)
Depreciation expense	22	5
Amortization on operating lease right-of-use asset	59
Changes in operating assets and liabilities:
Prepaid expenses and other assets	358	(1,035)
Accounts payable	33	573
Accrued expenses	1,147	851
Accounts payable and accrued expenses - related party	(32)	22
Operating lease liability	(58)
Net cash used in operating activities	(11,967)	(5,834)
Cash flows from investing activities
Sales and maturities of marketable securities	70,565
Purchases of marketable securities	(49,232)
Purchases of property, plant and equipment		(111)
Net cash provided by (used in) investing activities	21,333	(111)
Cash flows from financing activities
Proceeds from the issuance of common stock in connection with IPO		86,250
Proceeds from exercise of stock options	215
Net cash provided by financing activities	215	100,431
Net increase in cash and cash equivalents	9,581	94,486
Cash and cash equivalents at the beginning of the period	10,271	8,663
Cash and cash equivalents at the end of the period	19,852	103,149
Supplemental disclosure of noncash investing and financing activities:
Fixed asset and construction in process purchases payable or accrued at period end	534	6
Change in unrealized gain on marketable securities	55
Issuance costs included in accounts payable and accrued expenses		1,057
Conversion of preferred stock into common stock		36,501
IPO [Member]
Cash flows from financing activities
Proceeds from the issuance of common stock in connection with IPO	$ 123,200
Payment of stock issuance costs		(6,812)
Series C Convertible Preferred Stock [Member]
Cash flows from financing activities
Payment of stock issuance costs		(7)
Proceeds received from issuance of preferred stock		$ 21,000

Organization and Description of

Organization and Description of Business Operations	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	Note 1—Nature of Business Verrica Pharmaceuticals Inc. (the “Company”) was formed on July 3, 2013 and is incorporated in the State of Delaware. The Company is a medical dermatology company committed to the development and commercialization of novel treatments that provide meaningful benefit for people living with skin diseases. Liquidity and Capital Resources The Company has incurred substantial operating losses since inception and expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of June 30, 2019, the Company had an accumulated deficit of $47.5 million. Since inception, the Company has financed its operations through sales of convertible preferred stock and the sale of common stock in the Company’s initial public offering, with aggregate gross proceeds of $123.2 million and net proceeds of $114.9 million. As of June 30, 2019, the Company had cash, cash equivalents and marketable securities of $78.8 million.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2—Significant Accounting Policies Basis of Presentation The accompanying unaudited interim condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the unaudited interim condensed financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the balances and results for the periods presented. They may not include all of the information and footnotes required by GAAP for complete financial statements. Therefore, these financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto for the year ended December 31, 2018 filed with the Securities and Exchange Commission (the “SEC”) on March 7, 2019. The results of operations for any interim periods are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period. In the fourth quarter of 2018, the Company changed its policy for recognizing stock-based compensation expense for awards with service conditions only from the graded attribution method to the straight-line attribution method. The following tables present the effect of the change in accounting policy and its impact on the Company’s results of operations as previously reported for the three and six months ended June 30, 2018, as compared to the results of operations after the retrospective application of the change in accounting policy (in thousands, except share and per share amounts): For the Three Months Ended For the Six Months Ended June 30, 2018 June 30, 2018 As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: Operating expenses: Research and development $ 3,515 $ 3,609 $ 4,442 $ 4,538 General and administrative 1,955 2,503 2,916 3,489 Total operating expenses 5,470 6,112 7,358 8,027 Loss from operations (5,470 ) (6,112 ) (7,358 ) (8,027 ) Total other income 153 153 194 194 Net loss $ (5,317 ) $ (5,959 ) $ (7,164 ) $ (7,833 ) Net loss per share, basic and diluted $ (0.92 ) $ (1.04 ) $ (1.66 ) $ (1.82 ) Weighted average common shares outstanding, basic and diluted 5,751,326 5,751,326 4,308,996 4,308,996 Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially and adversely from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected. Significant Accounting Policies There have been no material changes in the Company’s significant accounting policies to those previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 other than the adoption of the FASB Accounting Standard Update (“ASU”) 2016-02, Leases (Topic 842) Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework–Changes to the Disclosure Requirements for Fair Value Measurement Net Loss Per Share Net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share excludes the potential impact of common stock options and unvested shares of restricted stock because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same. The table below provides potential shares outstanding that were not included in the computation of diluted net loss per common share, as the inclusion of these securities would have been anti-dilutive: As of June 30, 2019 2018 Shares issuable upon exercise of stock options 1,950,701 1,383,582 Non-vested shares under restricted stock grants 848,859 848,859

Investments In Marketable Secur

Investments In Marketable Securities	6 Months Ended
	Jun. 30, 2019
Investments [Abstract]
Investments in Marketable Securities	Note 3—Investments in Marketable Securities Investments in marketable securities consisted of the following as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury securities $ 10,933 $ 15 $ — $ 10,948 Commercial paper 33,072 10 — 33,082 Asset-backed securities 14,859 13 — 14,872 Total marketable securities $ 58,864 $ 38 $ — $ 58,902 December 31, 2018 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury securities $ 17,028 $ — $ (2 ) $ 17,026 Commercial paper 48,623 5 (4 ) 48,624 Asset-backed securities 13,904 — (16 ) 13,888 Total marketable securities $ 79,555 $ 5 $ (22 ) $ 79,538 There were no marketable securities with a maturity of greater than one year for either period presented. Unrealized gains and losses on marketable debt securities are recorded as a separate component of accumulated other comprehensive gain (loss) included in stockholders’ equity. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three categories: Level 1 — Quoted market prices in active markets for identical assets or liabilities. Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The following tables presents fair value of the Company’s marketable securities (in thousands): Fair Value Measurement as of June 30, 2019 Level 1 Level 2 Level 3 Total Assets U.S. treasury securities $ 10,948 $ — $ — $ 10,948 Commercial paper — 33,082 — 33,082 Asset-backed securities — 14,872 — 14,872 Total assets $ 10,948 $ 47,954 $ — $ 58,902 Fair Value Measurement as of December 31, 2018 Level 1 Level 2 Level 3 Total Assets U.S. treasury securities $ 17,026 $ — $ — $ 17,026 Commercial paper — 48,624 — 48,624 Asset-backed securities — 13,888 — 13,888 Total assets $ 17,026 $ 62,512 $ — $ 79,538

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	Note 4—Property, Plant and Equipment Property, plant and equipment, net consisted of (in thousands): As of As of June 30, December 31, 2019 2018 Leasehold improvements $ 68 $ 68 Office furniture and fixtures 48 48 Office equipment 28 28 Construction in process 1,150 131 1,294 275 Accumulated depreciation (42 ) (20 ) Total property, plant and equipment, net $ 1,252 $ 255 The Company has recorded an asset classified as construction in process

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Note 5—Related Party Transactions In December 2015, the Company entered into a services agreement (“SA”) with PBM Capital Group, LLC (“PBM”) an affiliate of PBM Capital Investments, LLC, to engage PBM for certain business development, operations, technical, contract, accounting and back office support services. Paul B. Manning, who is the Chairman and Chief Executive Officer of PBM and the current chairman of the Company’s Board of Directors, and certain entities affiliated with Mr. Manning, continue to be the Company’s largest stockholder on a collective basis. The Company agreed to pay PBM a fee of $2,500 per month for these services. The SA had an initial term of 12 months and automatically renewed monthly thereafter. In March 2018, the Company entered into an amendment to the SA with PBM effective as of April 1, 2018, which extended the term of the SA until March 31, 2019 (and is automatically renewable for successive monthly periods) and increased the management fee the Company is obligated to pay to PBM to $50,000 per month. On January 1, 2019, the SA was amended to reduce the monthly management fee to $26,333 as a result of a reduction in services provided by PBM. The SA, as amended, provides for termination by the Company with 30 days advance notice or a mutually agreed upon effective date for transition as individual services are cancelled with a corresponding reduction in the monthly management fee. For the three months ended June 30, 2019 and 2018, the Company incurred expenses under the SA of $79,000 and $150,000, respectively. For the six months ended June 30, 2019 and 2018, the Company incurred expenses under the SA of $158,000 and $157,500, respectively. As of June 30, 2019 and December 31, 2018, the Company had a payable due to PBM of $6,000 and $38,000, respectively. These balances include amounts for other miscellaneous expenses incurred by PBM and its affiliates.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses	Note 6—Accrued Expenses Accrued expenses consisted of the following (in thousands): As of June 30, 2019 As of December 31, 2018 Compensation and related costs $ 840 $ 1,261 Clinical and development 1,708 — Construction in process 21 — Consulting - former Chief Scientific Officer — 190 Professional fees 58 56 Other 57 10 Total accrued expenses $ 2,684 $ 1,517

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 7—Stock-Based Compensation In June 2018, the Board adopted and approved the 2018 Equity Incentive Plan (the “IPO Plan”), which amended and restated the Company’s prior 2013 Equity Incentive Plan (the “2013 Plan”) and became effective in connection with the IPO pricing on June 14, 2018. Prior to the effectiveness of the IPO Plan, the 2013 Plan provided for the grant of share-based awards to employees, directors and consultants of the Company. As a result of the effectiveness of the IPO Plan, no further grants may be made under the 2013 Plan. The IPO Plan provides for the grant of incentive stock options to employees, and for the grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards and other forms of stock awards to employees, including officers, consultants and directors. The IPO Plan also provides for the grant of performance-based cash awards to employees, including officers, consultants and directors. The Company has initially reserved 3,738,199 shares of common stock for issuance under the IPO Plan, which is the sum of (1) 2,198,198 new shares, plus (2) the number of shares reserved for issuance under the 2013 Plan at the time the IPO Plan became effective, plus (3) any shares subject to outstanding stock options or other stock awards that would have otherwise returned to the 2013 Plan (such as upon the expiration or termination of a stock award prior to exercise). The number of shares of common stock reserved for issuance under the IPO Plan will automatically increase on January 1 each year, for a period of ten years, from January 1, 2019 through January 1, 2028, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Board. As of June 30, 2019, 2,529,864 shares were available for grant under the IPO Plan. Stock-based compensation expense, which includes expense for both employees and non-employees, has been reported in the Company’s condensed statements of operations for the three and six months ended June 30, 2019 and 2018 as follows (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 144 $ 255 $ 284 $ 370 General and administrative 702 524 1,342 544 Total stock-based compensation $ 846 $ 779 $ 1,626 $ 914 Stock Options The grant date fair value of stock option awards is determined using the Black-Scholes option-pricing model. The following weighted-average assumptions were used during the three and six months ended June 30, 2019 and 2018 to estimate the fair value of stock option awards granted during the period: For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Exercise price $9.88 $10.01 $10.80 $7.64 Risk-free rate of interest 2.12% 2.86% 2.50% 2.68% Expected term (years) 5.7 6.1 6.0 6.1 Expected stock price volatility 75.24% 75.31% 77.42 72.65% Weighted average grant date fair value $6.48 $7.52 $7.36 $6.53 Dividend yield — — — — The following table summarizes the Company’s stock option activity under the 2013 Plan and the IPO Plan for the six months ended June 30, 2019: Weighted average Weighted average remaining contractual Aggregate intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2018 1,529,883 $ 8.03 Granted 607,575 10.80 Exercised (35,541 ) 6.07 Forfeitures (151,216 ) 8.87 Outstanding as of June 30, 2019 1,950,701 $ 8.86 8.9 $ 6,386,375 Options vested and exercisable as of June 30, 2019 474,727 $ 6.66 8.4 $ 2,490,858 As of June 30, 2019, the total unrecognized compensation related to unvested stock option awards granted was $9.9 million, which the Company expects to recognize over a weighted-average period of 3.0 years. Restricted Stock Pursuant to an Amended and Restated Stock Purchase Agreement (the “Amended and Restated Agreement”) between the Company and the former Chief Scientific Officer (“CSO”), 848,859 shares held by the former CSO are subject to repurchase at $0.0001 per share in the event the CSO ceases to be a consultant. These shares will be released from the repurchase option on the earliest to occur of (i) a change in control, (ii) regulatory approval of the Company’s new drug application for cantharidin, (iii) commercial sale of products and (iv) a covered termination, as defined in the Amended and Restated Agreement. As of June 30, 2019, the total unrecognized compensation expense related to the nonvested shares was $0.3 million. No compensation expense has been recognized for these nonvested shares as these shares are performance-based and the triggering event was not determined to be probable as of June 30, 2019. There was no activity related to restricted stock during the six months ended June 30, 2019

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Note 8—Leases Effective January 1, 2019, the Company accounts for its leases under ASC 842, Leases (Topic 842) In calculating the right of use asset and lease liability, the Company elects to combine lease and non-lease components. The Company excludes short-term leases having initial terms of 12 months or less from the new guidance as an accounting policy election and recognizes rent expense on a straight-line basis over the lease term. The Company continues to account for leases in the prior period financial statements under the previous guidance in ASC 840, Leases The Company leases office space in West Chester, Pennsylvania under an agreement classified as an operating lease that expires in May 2021. The Company does not act as a lessor or have any leases classified as financing leases. As of June 30, 2019, the Company had an operating lease liability of $248,000 of which $124,000 was classified as current and an operating right-of-use asset of $245,000, which were included in the condensed balance sheet. The components of lease expense are as follows (in thousands): For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Operating lease: Operating lease costs $ 47 $ 81 Short-term lease costs 5 10 Total rent expense $ 52 $ 91 The following summarizes additional information about the Company’s operating lease (dollars in thousands): For the Six Months Ended June 30, 2019 Operating cash outflows from operating lease $ 68 Operating lease right-of-use asset exchanged for operating lease liability $ 306 Weighted-average remaining lease term – operating lease 1.9 Weighted-average discount rate – operating lease 6.75 % Maturities of the Company’s operating lease, excluding short-term leases, as of June 30, 2019 are as follows (in thousands): Remainder of 2019 $ 68 2020 139 2021 58 Total lease payments 265 Less imputed interest (17 ) Operating lease liability $ 248 The following table presents the Company’s operating lease commitments as of December 31, 2018 under ASC 840 (in thousands): 2019 $ 136 2020 139 2021 58 Total $ 333

Subsequent Event

Subsequent Event	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Note 9—Subsequent Event On July 1, 2019, the Company entered into a lease for 5,829 square feet of office space located in West Chester, Pennsylvania that is expected to serve as the Company’s new headquarters beginning in . The initial term of the lease is seven years with one five-year renewal option and an ongoing right of first offer to lease up to approximately 5,000 square feet of additional space on the same floor of the building. Base rent over the initial lease term is $1.3 million, and the Company is also responsible for its share of the landlord’s operating expenses.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the unaudited interim condensed financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the balances and results for the periods presented. They may not include all of the information and footnotes required by GAAP for complete financial statements. Therefore, these financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto for the year ended December 31, 2018 filed with the Securities and Exchange Commission (the “SEC”) on March 7, 2019. The results of operations for any interim periods are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period. In the fourth quarter of 2018, the Company changed its policy for recognizing stock-based compensation expense for awards with service conditions only from the graded attribution method to the straight-line attribution method. The following tables present the effect of the change in accounting policy and its impact on the Company’s results of operations as previously reported for the three and six months ended June 30, 2018, as compared to the results of operations after the retrospective application of the change in accounting policy (in thousands, except share and per share amounts): For the Three Months Ended For the Six Months Ended June 30, 2018 June 30, 2018 As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: Operating expenses: Research and development $ 3,515 $ 3,609 $ 4,442 $ 4,538 General and administrative 1,955 2,503 2,916 3,489 Total operating expenses 5,470 6,112 7,358 8,027 Loss from operations (5,470 ) (6,112 ) (7,358 ) (8,027 ) Total other income 153 153 194 194 Net loss $ (5,317 ) $ (5,959 ) $ (7,164 ) $ (7,833 ) Net loss per share, basic and diluted $ (0.92 ) $ (1.04 ) $ (1.66 ) $ (1.82 ) Weighted average common shares outstanding, basic and diluted 5,751,326 5,751,326 4,308,996 4,308,996
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially and adversely from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.
Significant Accounting Policies	Significant Accounting Policies There have been no material changes in the Company’s significant accounting policies to those previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 other than the adoption of the FASB Accounting Standard Update (“ASU”) 2016-02, Leases (Topic 842) Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework–Changes to the Disclosure Requirements for Fair Value Measurement
Net Loss Per Share	Net Loss Per Share Net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share excludes the potential impact of common stock options and unvested shares of restricted stock because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same. The table below provides potential shares outstanding that were not included in the computation of diluted net loss per common share, as the inclusion of these securities would have been anti-dilutive: As of June 30, 2019 2018 Shares issuable upon exercise of stock options 1,950,701 1,383,582 Non-vested shares under restricted stock grants 848,859 848,859

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Schedule of Change in Accounting Policy and its Impact on Key Components of Financial Statements	The following tables present the effect of the change in accounting policy and its impact on the Company’s results of operations as previously reported for the three and six months ended June 30, 2018, as compared to the results of operations after the retrospective application of the change in accounting policy (in thousands, except share and per share amounts): For the Three Months Ended For the Six Months Ended June 30, 2018 June 30, 2018 As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: As Computed Under Straight-line Attribution Method: As Previously Reported Under Graded Attribution Method: Operating expenses: Research and development $ 3,515 $ 3,609 $ 4,442 $ 4,538 General and administrative 1,955 2,503 2,916 3,489 Total operating expenses 5,470 6,112 7,358 8,027 Loss from operations (5,470 ) (6,112 ) (7,358 ) (8,027 ) Total other income 153 153 194 194 Net loss $ (5,317 ) $ (5,959 ) $ (7,164 ) $ (7,833 ) Net loss per share, basic and diluted $ (0.92 ) $ (1.04 ) $ (1.66 ) $ (1.82 ) Weighted average common shares outstanding, basic and diluted 5,751,326 5,751,326 4,308,996 4,308,996
Schedule of Potential Shares Outstanding Excluded in Computation of Diluted Net Loss Per Common Share	The table below provides potential shares outstanding that were not included in the computation of diluted net loss per common share, as the inclusion of these securities would have been anti-dilutive: As of June 30, 2019 2018 Shares issuable upon exercise of stock options 1,950,701 1,383,582 Non-vested shares under restricted stock grants 848,859 848,859

Investments In Marketable Sec_2

Investments In Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2019
Investments [Abstract]
Schedule of Marketable Securities	Investments in marketable securities consisted of the following as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury securities $ 10,933 $ 15 $ — $ 10,948 Commercial paper 33,072 10 — 33,082 Asset-backed securities 14,859 13 — 14,872 Total marketable securities $ 58,864 $ 38 $ — $ 58,902 December 31, 2018 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury securities $ 17,028 $ — $ (2 ) $ 17,026 Commercial paper 48,623 5 (4 ) 48,624 Asset-backed securities 13,904 — (16 ) 13,888 Total marketable securities $ 79,555 $ 5 $ (22 ) $ 79,538
Schedule of Fair Value of Marketable Securities	The following tables presents fair value of the Company’s marketable securities (in thousands): Fair Value Measurement as of June 30, 2019 Level 1 Level 2 Level 3 Total Assets U.S. treasury securities $ 10,948 $ — $ — $ 10,948 Commercial paper — 33,082 — 33,082 Asset-backed securities — 14,872 — 14,872 Total assets $ 10,948 $ 47,954 $ — $ 58,902 Fair Value Measurement as of December 31, 2018 Level 1 Level 2 Level 3 Total Assets U.S. treasury securities $ 17,026 $ — $ — $ 17,026 Commercial paper — 48,624 — 48,624 Asset-backed securities — 13,888 — 13,888 Total assets $ 17,026 $ 62,512 $ — $ 79,538

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Schedule of Property, Plant and Equipment, Net	Property, plant and equipment, net consisted of (in thousands): As of As of June 30, December 31, 2019 2018 Leasehold improvements $ 68 $ 68 Office furniture and fixtures 48 48 Office equipment 28 28 Construction in process 1,150 131 1,294 275 Accumulated depreciation (42 ) (20 ) Total property, plant and equipment, net $ 1,252 $ 255

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands): As of June 30, 2019 As of December 31, 2018 Compensation and related costs $ 840 $ 1,261 Clinical and development 1,708 — Construction in process 21 — Consulting - former Chief Scientific Officer — 190 Professional fees 58 56 Other 57 10 Total accrued expenses $ 2,684 $ 1,517

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock Based Compensation Expense	Stock-based compensation expense, which includes expense for both employees and non-employees, has been reported in the Company’s condensed statements of operations for the three and six months ended June 30, 2019 and 2018 as follows (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 144 $ 255 $ 284 $ 370 General and administrative 702 524 1,342 544 Total stock-based compensation $ 846 $ 779 $ 1,626 $ 914
Assumptions Used to Estimate Fair Value	The grant date fair value of stock option awards is determined using the Black-Scholes option-pricing model. The following weighted-average assumptions were used during the three and six months ended June 30, 2019 and 2018 to estimate the fair value of stock option awards granted during the period: For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Exercise price $9.88 $10.01 $10.80 $7.64 Risk-free rate of interest 2.12% 2.86% 2.50% 2.68% Expected term (years) 5.7 6.1 6.0 6.1 Expected stock price volatility 75.24% 75.31% 77.42 72.65% Weighted average grant date fair value $6.48 $7.52 $7.36 $6.53 Dividend yield — — — —
Schedule of Stock Option Activity	The following table summarizes the Company’s stock option activity under the 2013 Plan and the IPO Plan for the six months ended June 30, 2019: Weighted average Weighted average remaining contractual Aggregate intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2018 1,529,883 $ 8.03 Granted 607,575 10.80 Exercised (35,541 ) 6.07 Forfeitures (151,216 ) 8.87 Outstanding as of June 30, 2019 1,950,701 $ 8.86 8.9 $ 6,386,375 Options vested and exercisable as of June 30, 2019 474,727 $ 6.66 8.4 $ 2,490,858

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Summary of Components of Lease Expense	The components of lease expense are as follows (in thousands): For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Operating lease: Operating lease costs $ 47 $ 81 Short-term lease costs 5 10 Total rent expense $ 52 $ 91 The following summarizes additional information about the Company’s operating lease (dollars in thousands): For the Six Months Ended June 30, 2019 Operating cash outflows from operating lease $ 68 Operating lease right-of-use asset exchanged for operating lease liability $ 306 Weighted-average remaining lease term – operating lease 1.9 Weighted-average discount rate – operating lease 6.75 %
Schedule of Maturities of Operating Lease	Maturities of the Company’s operating lease, excluding short-term leases, as of June 30, 2019 are as follows (in thousands): Remainder of 2019 $ 68 2020 139 2021 58 Total lease payments 265 Less imputed interest (17 ) Operating lease liability $ 248 The following table presents the Company’s operating lease commitments as of December 31, 2018 under ASC 840 (in thousands): 2019 $ 136 2020 139 2021 58 Total $ 333

Nature of Business - Additional

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Description Of Business [Line Items]
Accumulated deficit	$ (47,465)		$ (33,083)
Gross proceeds from issuance of common stock		$ 86,250
IPO [Member]
Description Of Business [Line Items]
Gross proceeds from issuance of common stock	123,200
Net proceeds from issuance of common stock	114,900
Cash, cash equivalents and marketable securities	$ 78,800

Significant Accounting Polici_4

Significant Accounting Policies - Schedule of Effect of Change in Accounting Policy and its Impact on Key Components on Statements of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 3,928		$ 3,515		$ 8,415	$ 4,442
General and administrative	3,593		1,955		7,132	2,916
Total operating expenses	7,521		5,470		15,547	7,358
Loss from operations	(7,521)		(5,470)		(15,547)	(7,358)
Total other income	520		153		1,067	194
Net loss	$ (7,001)	$ (7,479)	$ (5,317)	$ (1,847)	$ (14,480)	$ (7,164)
Net loss per share, basic and diluted	$ (0.28)		$ (0.92)		$ (0.58)	$ (1.66)
Weighted average common shares outstanding, basic and diluted	24,875,573		5,751,326		24,866,721	4,308,996
As Previously Reported Under Graded Attribution Method [Member]
Operating expenses:
Research and development			$ 3,609			$ 4,538
General and administrative			2,503			3,489
Total operating expenses			6,112			8,027
Loss from operations			(6,112)			(8,027)
Total other income			153			194
Net loss			$ (5,959)			$ (7,833)
Net loss per share, basic and diluted			$ (1.04)			$ (1.82)
Weighted average common shares outstanding, basic and diluted			5,751,326			4,308,996

Significant Accounting Polici_5

Significant Accounting Policies - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Jun. 30, 2019
Significant Accounting Policies [Line Items]
Operating lease right-of-use asset	$ 304,000	$ 245,000
Operating lease liability	306,000	$ 248,000
Deferred rent	2,000
Accumulated Deficit and Additional Paid-in Capital [Member]
Significant Accounting Policies [Line Items]
Adjustment to accumulated deficit and additional paid -in capital	$ 98,000

Significant Accounting Polici_6

Significant Accounting Policies - Schedule of Potential Shares Outstanding Excluded in Computation of Diluted Net Loss Per Common Share (Detail) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Shares issuable upon exercise of stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities that could potentially dilute basic earnings per share	1,950,701	1,383,582
Non-vested shares under restricted stock grants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities that could potentially dilute basic earnings per share	848,859	848,859

Investments in Marketable Sec_3

Investments in Marketable Securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Amortized Cost	$ 58,864	$ 79,555
Gross Unrealized Gains	38	5
Gross Unrealized Losses		(22)
Fair Value	58,902	79,538
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	10,933	17,028
Gross Unrealized Gains	15
Gross Unrealized Losses		(2)
Fair Value	10,948	17,026
Commercial Paper [Member]
Marketable Securities [Line Items]
Amortized Cost	33,072	48,623
Gross Unrealized Gains	10	5
Gross Unrealized Losses		(4)
Fair Value	33,082	48,624
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	14,859	13,904
Gross Unrealized Gains	13
Gross Unrealized Losses		(16)
Fair Value	$ 14,872	$ 13,888

Investments in Marketable Sec_4

Investments in Marketable Securities - Schedule of Fair Value of Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Marketable securities	$ 58,902	$ 79,538
Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	10,948	17,026
Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	47,954	62,512
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Marketable securities	10,948	17,026
U.S. Treasury Securities [Member] | Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	10,948	17,026
Commercial Paper [Member]
Marketable Securities [Line Items]
Marketable securities	33,082	48,624
Commercial Paper [Member] | Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	33,082	48,624
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Marketable securities	14,872	13,888
Asset Backed Securities [Member] | Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	$ 14,872	$ 13,888

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 1,294	$ 275
Accumulated depreciation	(42)	(20)
Total property, plant and equipment, net	1,252	255
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	68	68
Office Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	48	48
Office Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	28	28
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 1,150	$ 131

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - PBM Capital Group, LLC [Member] - USD ($)	Jan. 01, 2019	Dec. 02, 2015	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Services agreement initial term		12 months
Expenses incurred under services agreement				$ 79,000	$ 150,000	$ 158,000	$ 157,500
Due to related party				$ 6,000		$ 6,000		$ 38,000
Service Agreement [Member]
Related Party Transaction [Line Items]
Monthly management fee payable		$ 2,500
Amended Service Agreement [Member]
Related Party Transaction [Line Items]
Monthly management fee payable	$ 26,333		$ 50,000

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Compensation and related costs	$ 840	$ 1,261
Clinical and development	1,708
Construction in process	21
Consulting - former Chief Scientific Officer		190
Professional fees	58	56
Other	57	10
Total accrued expenses	$ 2,684	$ 1,517

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation related to unvested stock options	$ 9.9
Treasury stock, shares	105,144	105,144
Total unrecognized compensation related to nonvested restricted stock	$ 0.3
Amended and Restated Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Treasury stock, shares	848,859
Repurchase price	$ 0.0001
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average stock option recognize period	3 years
IPO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares reserved for issuance	3,738,199
Shares issued	2,198,198
Number of years reserved share increase	10 years
Annual Increase in number of common shares from January 1, 2019 through January 1, 2028	4.00%
Shares available for grant	2,529,864

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 846	$ 779	$ 1,626	$ 914
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	144	255	284	370
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 702	$ 524	$ 1,342	$ 544

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used to Estimate Fair Value Stock Options (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee Service Share Based Compensation Aggregate Disclosures [Abstract]
Exercise price	$ 9.88	$ 10.01	$ 10.80	$ 7.64
Risk-free rate of interest	2.12%	2.86%	2.50%	2.68%
Expected term (years)	5 years 8 months 12 days	6 years 1 month 6 days	6 years	6 years 1 month 6 days
Expected stock price volatility	75.24%	75.31%	77.42%	72.65%
Weighted average grant date fair value	$ 6.48	$ 7.52	$ 7.36	$ 6.53

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Stock Option Activity (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee Service Share Based Compensation Aggregate Disclosures [Abstract]
Number of shares, Outstanding Beginning Balance			1,529,883
Number of shares, Granted			607,575
Number of shares, Exercised			(35,541)
Number of shares, Forfeitures			(151,216)
Number of shares, Outstanding Ending Balance	1,950,701		1,950,701
Number of shares, Options vested and exercisable Ending Balance	474,727		474,727
Weighted average exercise price, Outstanding Beginning Balance			$ 8.03
Weighted average exercise price, Granted	$ 9.88	$ 10.01	10.80	$ 7.64
Weighted average exercise price, Exercised			6.07
Weighted average exercise price, Forfeitures			8.87
Weighted average exercise price, Outstanding Ending Balance	8.86		8.86
Weighted average exercise price, Options vested and exercisable Ending Balance	$ 6.66		$ 6.66
Weighted average remaining contractual life (in years), Outstanding			8 years 10 months 24 days
Weighted average remaining contractual life (in years), Options vested and exercisable			8 years 4 months 24 days
Aggregate intrinsic value, Outstanding Ending Balance	$ 6,386,375		$ 6,386,375
Aggregate intrinsic value, Options vested and exercisable Ending Balance	$ 2,490,858		$ 2,490,858

Leases - Additional Information

Leases - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Operating lease expiration	2021-05
Operating lease liability	$ 248,000	$ 306,000
Operating lease liability, current	124,000
Operating lease right-of-use asset	$ 245,000	$ 304,000

Leases - Summary of Components

Leases - Summary of Components of Lease Expense (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Leases [Abstract]
Operating lease costs	$ 47	$ 81
Short-term lease costs	5	10
Total rent expense	$ 52	91
Operating cash outflows from operating lease		68
Operating lease right-of-use asset exchanged for operating lease liability		$ 306
Weighted-average remaining lease term – operating lease	1 year 10 months 24 days	1 year 10 months 24 days
Weighted-average discount rate – operating lease	6.75%	6.75%

Leases -Schedule of Maturities

Leases -Schedule of Maturities of Operating Lease (Details) - USD ($)	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
Remainder of 2019	$ 68,000
2019			$ 136,000
2020	139,000		139,000
2021	58,000		58,000
Total lease payments	265,000		$ 333,000
Less imputed interest	(17,000)
Operating lease liability	$ 248,000	$ 306,000

Subsequent Event - Additional I

Subsequent Event - Additional Information (Details) - Subsequent Event [Member] - Pennsylvania [Member] $ in Millions	Jul. 01, 2019USD ($)ft²
Subsequent Event [Line Items]
Lease agreement commencement date	Jul. 1, 2019
Area of office space for lease	5,829
Operating lease, initial term of contract	7 years
Operating lease, renewal term	5 years
Operating lease, option to extend, description	The initial term of the lease is seven years with one five-year renewal option and an ongoing right of first offer to lease up to approximately 5,000 square feet of additional space on the same floor of the building.
Lessee operating lease existence of option to extend	true
Operating lease, base rent over initial lease term | $	$ 1.3
Additional area of office space available for lease	5,000