Verrica Pharmaceuticals (VRCA) 10-K 7 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 04, 2019	Jun. 29, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	VRCA
Entity Registrant Name	Verrica Pharmaceuticals Inc.
Entity Central Index Key	1,660,334
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 244.6
Entity Common Stock, Shares Outstanding		25,707,256
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transaction Period	true

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 10,271	$ 8,663
Marketable securities	79,538
Prepaid expenses and other assets	1,343	420
Total current assets	91,152	9,083
Property and equipment, net	255
Deposits	499
Total assets	91,906	9,083
Current liabilities:
Accounts payable	922	153
Accrued expenses	1,517	449
Accounts payable and accrued expenses - related party	38	14
Total current liabilities	2,477	616
Total liabilities	2,477	616
Commitments and Contingencies (Note 6)
Convertible preferred stock		15,508
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 and December 31, 2017
Common stock, $0.0001 par value; 200,000,000 and 33,236,900 shares authorized as of December 31, 2018 and December 31, 2017, respectively; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018 and 3,804,643 shares issued and 3,699,499 shares outstanding as of December 31, 2017, respectively	3
Treasury stock, at cost, 105,144 shares as of December 31, 2018 and December 31, 2017	0	0
Additional paid-in capital	122,526	5,394
Accumulated deficit	(33,083)	(12,435)
Accumulated other comprehensive loss	(17)
Total stockholders’ equity (deficit)	89,429	(7,041)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 91,906	9,083
Series A Convertible Preferred Stock [Member]
Current liabilities:
Convertible preferred stock		10,508
Series B Convertible Preferred Stock [Member]
Current liabilities:
Convertible preferred stock		$ 5,000

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	33,236,900
Common stock, shares issued	25,809,900	3,804,643
Common stock, shares outstanding	25,704,756	3,699,499
Treasury stock, shares	105,144	105,144
Series A Convertible Preferred Stock [Member]
Convertible preferred stock, shares authorized	0	21,302,972
Convertible preferred stock, shares issued	0	21,302,972
Convertible preferred stock, shares outstanding	0	21,302,972
Series B Convertible Preferred Stock [Member]
Convertible preferred stock, shares authorized	0	1,937,984
Convertible preferred stock, shares issued	0	1,937,984
Convertible preferred stock, shares outstanding	0	1,937,984

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 12,826	$ 3,730
General and administrative	9,052	727
Total operating expenses	21,878	4,457
Loss from operations	(21,878)	(4,457)
Other income (expense):
Interest income	1,231
Other expense	(1)
Interest expense - related party		(2)
Total other income (expense)	1,230	(2)
Net loss	(20,648)	(4,459)
Net loss attributable to common stockholders	$ (20,648)	$ (9,759)
Net loss per share, basic and diluted	$ (1.41)	$ (1.56)
Net loss attributable to common stockholders	$ (1.41)	$ (3.42)
Weighted average common shares outstanding, basic and diluted	14,662,751	2,850,269
Net loss	$ (20,648)	$ (4,459)
Other comprehensive loss:
Unrealized loss on marketable securities	(17)
Comprehensive loss	$ (20,665)	(4,459)
Series A Preferred Stock [Member]
Other income (expense):
Deemed dividend on Series A preferred stock		$ (5,300)
Deemed dividend on Series A preferred stock		$ (1.86)

STATEMENTS OF CONVERTIBLE PREFE

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - 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 at Cost [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2016	$ (2,664)					$ 12	$ (2,676)
Beginning Balance (shares) at Dec. 31, 2016		21,302,972
Beginning Balance at Dec. 31, 2016		$ 2,789
Beginning Balance (shares) at Dec. 31, 2016					3,804,643			105,144
Stock-based compensation	82					82
Series A convertible preferred stock receivable		8,000
Issuance cost for preferred stock		(281)
Beneficial conversion feature for Series A preferred stock, temporary equity		(5,300)
Beneficial conversion feature for Series A preferred stock	5,300					5,300
Deemed dividend for Series A preferred stock, temporary equity		$ 5,300
Deemed dividend for Series A preferred stock	(5,300)						(5,300)
Convertible preferred stock			$ 5,000
Convertible preferred stock (shares)			1,937,984
Net loss	(4,459)						(4,459)
Ending Balance at Dec. 31, 2017	(7,041)					5,394	(12,435)
Ending Balance (shares) at Dec. 31, 2017		21,302,972	1,937,984
Ending Balance at Dec. 31, 2017	15,508	$ 10,508	$ 5,000
Ending Balance (shares) at Dec. 31, 2017					3,804,643			105,144
Stock-based compensation	2,251					2,251
Exercise of stock options	7					7
Exercise of stock options (in shares)					8,385
Issuance cost for preferred stock				$ (7)
Convertible preferred stock				$ 21,000
Convertible preferred stock (shares)				4,606,267
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	78,376				$ 1	78,375
Issuance of common stock in connection with IPO, net of offering costs (shares)					5,750,000
Net loss	(20,648)						(20,648)
Unrealized loss on marketable securities	(17)								$ (17)
Ending Balance at Dec. 31, 2018	$ 89,429				$ 3	$ 122,526	$ (33,083)		$ (17)
Ending Balance (shares) at Dec. 31, 2018		0	0
Ending Balance (shares) at Dec. 31, 2018					25,809,900			105,144

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (20,648,000)	$ (4,459,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,251,000	82,000
Accretion of discounts on marketable securities	(435,000)
Depreciation expense	20,294
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(923,000)	(403,000)
Accounts payable	769,000	86,000
Accrued expenses	1,068,000	133,000
Accounts payable and accrued expenses - related party	24,000	(22,000)
Net cash used in operating activities	(17,874,000)	(4,583,000)
Cash flows from investing activities
Purchases of marketable securities	(79,120,000)
Purchases of property, plant and equipment	(275,000)
Deposit for construction of equipment	(499,000)
Net cash used in investing activities	(79,894,000)
Cash flows from financing activities
Proceeds from the issuance of common stock in connection with IPO	86,250,000
Proceeds from exercise of stock options	7,000
Net cash provided by financing activities	99,376,000	12,719,000
Net increase in cash and cash equivalents	1,608,000	8,136,000
Cash and cash equivalents at the beginning of the year	8,663,000	527,000
Cash and cash equivalents at the end of the year	10,271,000	8,663,000
Supplemental disclosure of cash flow information:
Cash paid for interest		1,000
Supplemental disclosure of noncash investing and financing activities:
Change in unrealized loss on marketable securities	(17,000)
Conversion of preferred stock into common stock	36,501,000
IPO [Member]
Cash flows from financing activities
Payment of stock issuance costs	(7,874,000)
Series A Convertible Preferred Stock [Member]
Cash flows from financing activities
Payment of stock issuance costs		(281,000)
Proceeds received from subscription receivable / issuance of preferred stock		8,000,000
Series C Convertible Preferred Stock [Member]
Cash flows from financing activities
Payment of stock issuance costs	(7,000)
Proceeds received from subscription receivable / issuance of preferred stock	$ 21,000,000	$ 5,000,000

Organization and Description of

Organization and Description of Business Operations	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business Operations	Note 1—Organization and Description of Business Operations 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. Reverse Stock Split On June 4, 2018, the Company effected a 1.714-for-one reverse stock split of Company’s common stock. No fractional shares were issued in connection with the stock split. The par value and other terms of the common stock were not affected by the stock split. All share and per share amounts, including stock options, have been retroactively adjusted in these financial statements for all periods presented to reflect the 1.714-for-one reverse stock split. Further, exercise prices of stock options have been retroactively adjusted in these financial statements for all periods presented to reflect the 1.714-for-one reverse stock split. The number of shares of the Company’s preferred stock were not affected by the reverse stock split; however, the conversion ratios were adjusted to reflect the reverse stock split. 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 December 31, 2018, the Company had an accumulated deficit of $33.1 million. On February 20, 2018 and March 7, 2018, the Company issued an aggregate of 4,606,267 shares of Series C convertible preferred stock, at an issuance price of $4.559 per share, for gross proceeds of $21.0 million. On June 19, 2018, the Company completed an initial public offering (“IPO”) of its common stock, which resulted in the issuance and sale of 5,750,000 shares of its common stock at a public offering price of $15.00 per share, generating net proceeds of $78.4 million after deducting underwriting discounts and other offering costs. Upon the closing of the IPO, all outstanding shares of the Company’s Series A, Series B and Series C convertible preferred stock were automatically converted into 16,246,872 shares of the Company’s common stock. In addition, upon the closing of the IPO, the Company’s amended and restated certificate of incorporation authorized the Company to issue up to 200,000,000 shares of common stock, $0.0001 par value per share, and 10,000,000 shares of preferred stock, $0.0001 par value per share, all of which shares of preferred stock are undesignated.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2—Significant Accounting Policies Basis of Presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company’s functional currency is the U.S. dollar. 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. The most significant estimates in the Company’s financial statements relate to the valuation of common stock and stock options. 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. Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment. Cash, Cash Equivalents and Marketable Securities The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and money market mutual funds. The Company classifies its marketable securities as “available-for-sale”, pursuant to ASC 320 Investments—Debt and Equity Securities There were no marketable securities with a maturity of greater than one year as of December 31, 2018. The following table presents the Company’s marketable securities as of December 31, 2018 (in thousands): December 31, 2018 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value Commercial paper $ 48,623 $ 5 $ (4 ) $ 48,624 U.S. treasury securities 17,028 — (2 ) 17,026 Asset-backed securities 13,904 — (16 ) 13,888 Total marketable securities $ 79,555 $ 5 $ (22 ) $ 79,538 Concentrations of Credit Risk and Off-Balance Sheet Risk Cash, cash equivalents and marketable securities are financial instruments that are potentially subject to concentrations of credit risk. The Company’s deposits are in accounts at large financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the funds are held. The Company has no financial instruments with off-balance sheet risk of loss. Property and Equipment Property and equipment is recorded at cost less accumulated depreciation. Depreciation and amortization is calculated using the straight line method over the expected useful life of the asset, after the asset is placed in service. The Company generally uses the following depreciable lives for its major classifications of property and equipment: Description Useful Lives Equipment 5 years Leasehold Improvements Lease term Office Furniture and Fixtures 3 years Expenditures associated with upgrades and enhancements that improve, add functionality, or otherwise extend the life of property and equipment are capitalized, while expenditures that do not, such as repairs and maintenance, are expensed as incurred. The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. If the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount, an impairment loss would be recognized if the carrying value of the asset exceeds its fair value. Fair value is generally determined using discounted cash flows. No impairment losses have been recorded since inception. Research and Development Costs The Company’s research and development expenses consist primarily of costs associated with the Company’s clinical trials, salaries, payroll taxes, employee benefits, and equity-based compensation charges for those individuals involved in ongoing research and development efforts. Research and development costs are expensed as incurred. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Fair Value Measurement ASC 820, Fair Value Measurements The accounting guidance classifies fair value measurements in one of the following three categories for disclosure purposes: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Inputs other than Level 1 prices for similar assets or liabilities that are directly or indirectly observable in the marketplace. Level 3: Unobservable inputs which are supported by little or no market activity and values determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation. The following table presents fair value of the Company’s marketable securities as of December 31, 2018 (in thousands): Fair Value Measurement as of December 31, 2018 Level 1 Level 2 Level 3 Total Commercial paper $ — $ 48,624 $ — $ 48,624 U.S. treasury securities 17,026 — — 17,026 Asset-backed securities — 13,888 — 13,888 Total $ 17,026 $ 62,512 $ — $ 79,538 Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources. For the year ended December 31, 2018, comprehensive loss includes net loss and unrealized loss on marketable securities. Stock-Based Compensation The Company accounts for stock-based compensation awards in accordance with ASC 718, Compensation –Stock Compensation Non-employee options are remeasured to fair value each period and t . The use of the Black‑Scholes option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk‑free interest rates, and, for grants prior to the Company’s IPO, the value of the common stock. The expected life of stock options was estimated using the “simplified method,” as the Company has limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock options grants. The simplified method is based on the average of the vesting tranches and the contractual life of each grant. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies. The risk-free interest rate is based on U.S. Treasury notes with a term approximating the expected life of the option. Change in Accounting Principle - Stock-Based Compensation In the fourth quarter of 2018, the Company changed its policy for recognizing stock-based compensation expense for graded-vesting awards with service conditions only from the graded attribution method to the straight-line attribution method. The Company views these awards as single awards and believes that the straight-line attribution method more accurately reflects the pattern of service provided by the employees versus the graded attribution method which significantly front loads the stock-based compensation expense and does not appropriately match the expense with the services provided. In addition, based on research and analysis, the Company believes the straight-line attribution method for stock-based compensation expense for service condition-only awards is the predominant method used in its industry. The Company has concluded that the straight-line attribution method for stock-based compensation is a preferable accounting policy in accordance with ASC 250, Accounting Changes and Error Corrections and has applied this change retrospectively. The impact from the change in accounting policy for periods prior to January 1, 2018 was immaterial. The following tables present the effect of the change in accounting policy and its impact on key components of the Company’s 2018 financial statements (in thousands, except share and per share amounts): Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight- line Attribution Method Effect of Change Operating expenses: Research and development $ 12,939 $ 12,826 $ (113 ) General and administrative 10,441 9,052 (1,389 ) Total operating expenses 23,380 21,878 (1,502 ) Loss from operations (23,380 ) (21,878 ) 1,502 Other income (expense): Interest income 1,231 1,231 — Other expense (1 ) (1 ) — Total other income 1,230 1,230 — Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Net loss per common share, basic and diluted $ (1.51 ) $ (1.41 ) $ 0.10 Weighted average common shares outstanding, basic and diluted 14,662,751 14,662,751 Stock-based compensation expense included above: Research and development $ 472 $ 359 $ (113 ) General and administrative 3,281 1,892 (1,389 ) Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Other comprehensive loss: Unrealized loss on marketable securities (17 ) (17 ) — Comprehensive loss $ (22,167 ) $ (20,665 ) $ 1,502 As of December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Stockholders’ equity: Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 $ — $ — $ — Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2018; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018 3 3 — Treasury stock, at cost, 105,144 shares as of December 31, 2018 — — — Additional paid-in capital 124,028 122,526 (1,502 ) Accumulated deficit (34,585 ) (33,083 ) 1,502 Accumulated other comprehensive loss (17 ) (17 ) — Total stockholders’ equity $ 89,429 $ 89,429 $ — Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Cash flows from operating activities: Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Adjustments to reconcile net loss to net cash used in operating activities: Stock-based compensation 3,753 2,251 (1,502 ) Accretion of discounts on marketable securities (435 ) (435 ) — Depreciation expense 20 20 — Changes in operating assets and liabilities: Prepaid expenses and other assets (923 ) (923 ) — Accounts payable 769 769 — Accrued expenses 1,068 1,068 — Accounts payable and accrued expenses – related party 24 24 — Net cash used in operating activities $ (17,874 ) $ (17,874 ) $ — Income Taxes Income taxes are recorded in accordance with ASC 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. 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 Series A, Series B and Series C Preferred Stock, 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 December 31, 2018 2017 Shares issuable upon conversion of Series A Preferred — 12,428,773 Shares issuable upon conversion of Series B Preferred — 1,130,679 Shares issuable upon exercise of stock options 1,529,883 90,429 Non-vested shares under restricted stock grants 848,859 848,859 Recently Adopted Accounting Pronouncements In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In April 2016, the FASB issued ASU No. 2016-09, Share-Based Payment: Simplifying the Accounting for Share-Based Payments In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting Recently Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements The adoption of this standard is not expected to have a significant impact on the Company’s statements of operations and comprehensive loss and statements of cash flows. In June 2018, the FASB issued ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting Revenue from Contracts with Customers 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 will adopt this standard as of January 1, 2019 but In August 2018, the FASB issued ASU 2018-15, Intangibles–Goodwill and Other–Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	Note 3—Property and Equipment Property and equipment, net consisted of (in thousands): As of December 31, 2018 Leasehold improvements $ 68 Office furniture and fixtures 48 Office equipment 28 Construction in process 131 275 Accumulated depreciation (20 ) Total property and equipment, net $ 255 Depreciation expense for the years ended December 31, 2018 was $20,294. Prior to 2018, the Company did not hold any property or equipment. The Company has recorded an asset classified as construction in process

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Note 4—Related Party Transactions Prior to the IPO, the Company was controlled by PBM VP Holdings, LLC (“PBM VP Holdings”) an affiliate of PBM Capital Group, LLC (“PBM”). 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 shareholder on a collective basis. On December 2, 2015, the Company entered into a Services Agreement (a “SA”) with PBM. Pursuant to the terms of the SA, which had an initial term of twelve months (and was automatically renewable for successive monthly periods), PBM rendered advisory and consulting services to the Company. Services provided under the SA included certain business development, operations, technical, contract, accounting and back office support services. In consideration for these services, the Company was obligated to pay PBM a monthly management fee of $2,500. On March 29, 2018, the Company amended the SA with PBM, effective as of April 1, 2018, increasing the monthly fee to $50,000. 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. For the years ended December 31, 2018 and 2017, the Company incurred expenses under the SA of $457,500 and $30,000, respectively, which were primarily included in general and administrative expenses. As of December 31, 2018 and 2017, the Company had payables due to PBM and its affiliates of $38,000 and $14,000, respectively. These balances include amounts due for other miscellaneous expenses incurred by PBM and its affiliates.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued Expenses	Note 5—Accrued Expenses Accrued expenses consisted of the following (in thousands): As of December 31, 2018 2017 Compensation and related costs $ 1,261 $ 49 Clinical trials and drug development — 233 Consulting - former Chief Scientific Officer 190 — Professional fees 56 129 Other 10 38 Total accrued expenses $ 1,517 $ 449

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 6—Commitments and Contingencies Litigation As of December 31, 2018 and 2017, there was no litigation against the Company. Supply Agreement and Purchase Order On March 22, 2018, the Company executed a purchase order with a supplier, denominated in Chinese yuan, pursuant to which the Company agreed to purchase approximately $2.3 million of crude cantharidin material. As of December 31, 2018, the Company purchased approximately $1.5 million of crude cantharidin material under this purchase order. On July 16, 2018, the Company entered into a supply agreement with the supplier. The executed purchase order is covered under the terms of the supply agreement. Pursuant to the supply agreement, the supplier has agreed that it will not supply cantharidin, any beetles or other raw material from which cantharidin is derived to any other customer in North America, subject to specified minimum annual purchase orders and forecasts. The supply agreement has an initial five-year term, which is subject to automatic renewal absent termination by either party in accordance with the terms of the supply agreement. Each party also has the right to terminate the supply agreement for other customary reasons such as material breach or bankruptcy. Agreements with Former Chief Scientific Officer On May 31, 2018, the Company and the former Chief Scientific Officer (“CSO”) executed a transition agreement related to his resignation from employment as well as a Consulting Agreement (the “Consulting Agreement”) that began upon the closing of the IPO. The Consulting Agreement provides for cash payments to the former CSO of $29,375 per month for the first 12 months of the agreement. After the first 12 months, the former CSO will receive $300 per hour for each hour of consulting services provided. As of December 31, 2018, $0.2 million remained accrued under this Consulting Agreement. Facility Lease The Company has operations in a facility in West Chester, Pennsylvania pursuant to a sublease agreement that expires in May 2021 . Rent expense under this sublease was $97,503 in 2018 and future minimum lease payments are as follows (in thousands): 2019 $ 136 2020 139 2021 58 Total minimum lease payments $ 333

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Note 7—Stockholders’ Equity Common Stock The Company had authorized 200,000,000 and 33,236,900 shares of common stock, $0.0001 par value per share, as of December 31, 2018 and 2017, respectively. Each share of common stock is entitled to one voting right. Common stock owners are entitled to dividends when funds are legally available and declared by the Board. On June 19, 2018, the Company completed an IPO of its common stock, which resulted in the issuance and sale of 5,750,000 shares of its common stock at a public offering price of $15.00 per share, generating net proceeds of $78.4 million after deducting underwriting discounts and other offering costs. The shares commenced trading on the Nasdaq Global Market on June 15, 2018 under the ticker symbol “VRCA.” Restricted Stock Pursuant to an Amended and Restated Stock Purchase Agreement (the “Amended and Restated Agreement”) between the Company and the former CSO, 848,859 shares held by the former CSO are subject to repurchase by the Company 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. 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 December 31, 2018. See Note 8. Convertible Preferred Stock On December 2, 2015, the Company issued an aggregate of 21,302,972 shares of Series A Preferred Stock to fourteen investors for cash consideration of $1.9 million, conversion of previously outstanding notes payable and accrued interest of $0.5 million and a stock subscription receivable of $8.5 million. The Company incurred aggregate issuance costs of $0.4 million, related to the issuance of the Series A Preferred Stock and subsequent settlement of the stock subscription receivable. PBM VP Holdings paid the Company $0.5 million during the year ended December 31, 2016, and $8.0 million during the year ended December 31, 2017 to settle the stock subscription receivable. Upon the closing of the IPO on June 19, 2018, all outstanding shares of the Company’s Series A Preferred Stock were automatically converted into 12,428,773 shares of the Company’s common stock. On December 15, 2017, the Company issued and sold an aggregate of 1,937,984 shares of Series B Preferred Stock, at an issuance price of $2.58 per share, for gross proceeds of $5.0 million. The Company did not incur any issuance costs for the Series B Preferred Stock. Upon the closing of the IPO on June 19, 2018, all outstanding shares of the Company’s Series B Preferred Stock were automatically converted into 1,130,679 shares of the Company’s common stock. On February 20, 2018 and March 7, 2018, the Company issued and sold an aggregate of 4,606,267 shares of Series C Preferred Stock, at an issuance price of $4.559 per share, for aggregate gross proceeds of $21.0 million. Upon the closing of the IPO on June 19, 2018, all outstanding shares of the Company’s Series C Preferred Stock were automatically converted into 2,687,420 shares of the Company’s common stock. The Company classified its Convertible Preferred Stock outside of stockholders’ deficit because redemption of the Convertible Preferred Stock, upon a deemed liquidation event, was not solely within the Company’s control.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 8—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 19, 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 December 31, 2018, 1,958,033 shares were available for grant under the IPO Plan. Stock Options The Company’s employee stock options generally vest as follows: 25% after 12 months of continuous services and the remaining 75% on a ratable basis over a 36-month period from 12 months after the grant date. Stock options granted during the year ended December 31, 2018 have a maximum contractual term of 10 years. The stock options are subject to time vesting requirements through 2022, are nontransferable, and have term expiration dates set to expire through 2028. The grant date fair value of employee stock option awards is determined using the Black-Scholes option-pricing model. The following assumptions were used during the years ended December 31, 2018 and 2017 to estimate the fair value of employee stock option awards: For the Year Ended December 31, 2018 2017 Exercise price $6.52 - $16.32 $0.90 Risk-free rate of interest 2.58% - 3.13% 1.92% - 2.23% Expected term (years) 6.15 6.25 Expected stock price volatility 58.26% - 83.67% 79.02% - 79.12% Dividend yield — — Weighted average grant date fair value $6.95 $0.12 Non-employee options are remeasured to fair value each period through operations using a Black-Scholes option-pricing model until the options vest. There were no stock options granted to non-employees during the years ended December 31, 2018 and 2017. Key assumptions used to estimate the fair value of the non-employee stock options remeasured during the years ended December 31, 2018 and 2017 are as follows: For the Year Ended December 31, 2018 2017 Exercise price $0.90 $0.90 Risk-free rate of interest 2.33% - 3.06% 2.16% - 2.48% Expected term (years) 7.53 8.43 Expected stock price volatility 58.26% - 83.81% 77.59% - 79.12% Dividend yield — — Weighted average fair value $9.22 $3.37 The following table summarizes the Company’s employee stock option activity under the 2013 Plan and the IPO Plan for the year ended December 31, 2018: Weighted average Aggregate Weighted average remaining contractual Intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2017 17,502 $ 0.90 9.0 Options granted 1,451,839 8.34 Exercised (8,385 ) 0.90 Forfeited/Cancelled (4,000 ) 16.32 Outstanding as of December 31, 2018 1,456,956 $ 8.27 9.2 $ 1,739,581 Options vested and exercisable as of December 31, 2018 192,018 $ 6.52 9.1 $ 312,995 The following table summarizes the Company’s non-employee stock option activity under the 2013 Plan and the IPO Plan for the year ended December 31, 2018: Weighted average Aggregate Weighted average remaining contractual intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2017 72,927 $ 0.90 8.3 Granted — — Outstanding as of December 31, 2018 72,927 $ 0.90 7.3 $ 528,721 Options vested and exercisable as of December 31, 2018 55,910 $ 0.90 7.3 $ 405,348 The aggregate intrinsic value in the above table is calculated as the difference between fair value of the Company’s common stock price and the exercise price of the stock options. The weighted average grant date fair value per share for the employee stock option granted during the years ended December 31, 2018 and 2017 was $6.95 and $0.12, respectively. As of December 31, 2018, the total unrecognized compensation related to unvested employee and non-employee stock option awards granted was $8.1 million, which the Company expects to recognize over a weighted-average period of 3.1 years. Restricted Stock The following table summarizes restricted stock award activities for the year ended December 31, 2018: Weighted Average Grant Date Fair Number of Shares Value Nonvested at December 31, 2017 848,859 $ 0.33 Granted — — Nonvested at December 31, 2018 848,859 $ 0.33 As of December 31, 2018, 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 December 31, 2018. Stock-based compensation expense, which includes expense for both employees and non-employees, has been reported in the Company’s statements of operations for the years ended December 31, 2018 and 2017 as follows (in thousands): For the Year Ended December 31, 2018 2017 Research and development $ 359 $ 82 General and administrative 1,892 — Total stock-based compensation $ 2,251 $ 82

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 9–Income Taxes There is no provision for income taxes as the Company has historically incurred operating losses and maintains a full valuation allowance against its deferred tax assets. Differences between the provision (benefit) for income taxes and income taxes at the statutory federal income tax rate are as follows (in thousands): For the Year Ended December 31, 2018 2017 Tax computed at statutory federal income tax rate 1 $ (4,336 ) $ (1,560 ) State taxes, net of federal benefit (1,478 ) (255 ) Rate change — 898 Permanent items 409 — Other (5 ) — Change in valuation allowance 5,410 917 Income tax provision (benefit) $ — $ — 1. Statutory U.S. federal income tax rate of 21% in 2018 and 35% in 2017. Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2018 2017 Deferred tax assets: Net operating loss carryovers $ 6,909 $ 1,946 Accrued expenses and other 510 27 Total deferred tax assets 7,419 1,973 Less valuation allowance (7,383 ) (1,973 ) Deferred tax asset, net of valuation allowance 36 — Deferred tax liabilities: Fixed assets (36 ) — Total deferred tax liabilities (36 ) — Net deferred tax assets $ — $ — The Company has determined, based upon all available evidence, that it is more likely than not that the net deferred tax asset will not be realized and, accordingly, has provided a full valuation allowance against its net deferred tax asset. As of December 31, 2018, the Company had federal and state net operating loss carryforwards of approximately $24.1 million and $24.1 million, respectively. The federal and state net operating loss carryforwards that were generated prior to 2018 will begin to expire, if not utilized, by 2033. Under the 2017 federal income tax law changes, federal net operating losses incurred in 2018 and in future years may be carried forward indefinitely, but the deductibility of such federal net operating losses is limited. As of December 31, 2018, the Company has uncertain tax positions related to federal and state income credits for its research and development activities. The total amount of unrecognized tax benefits was $0.1 million as of December 31, 2018 and The 2015 and subsequent federal and state tax years for the Company remain open for the assessment of income taxes.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	Note 10–Selected Quarterly Financial Data (Unaudited) 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. See Note 2 - Change in Accounting Principle - Stock-Based Compensation. The impact from the change in accounting policy for periods prior to January 1, 2108 was immaterial. As a result, the quarterly periods in 2017 have not been adjusted for the change in accounting policy. 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 2018 quarters ended March 31, June 30, and September 30, 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 Quarter Ended As Computed Under Straight-line Attribution Method: March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Operating expenses: Research and development $ 927 $ 3,515 $ 3,467 $ 4,917 General and administrative 961 1,955 2,865 3,271 Total operating expenses 1,888 5,470 6,332 8,188 Loss from operations (1,888 ) (5,470 ) (6,332 ) (8,188 ) Total other income 41 153 426 610 Net loss $ (1,847 ) $ (5,317 ) $ (5,906 ) $ (7,578 ) Net loss per share, basic and diluted $ (0.65 ) $ (0.92 ) $ (0.24 ) $ (0.30 ) Weighted average common shares outstanding, basic and diluted 2,850,460 5,751,326 24,847,512 24,847,877 For the Quarter Ended As Previously Reported Under Graded Attribution Method: March 31, 2018 June 30, 2018 September 30, 2018 Operating expenses: Research and development $ 929 $ 3,609 $ 3,484 General and administrative 986 2,503 3,681 Total operating expenses 1,915 6,112 7,165 Loss from operations (1,915 ) (6,112 ) (7,165 ) Total other income 41 153 426 Net loss $ (1,874 ) $ (5,959 ) $ (6,739 ) Net loss per share, basic and diluted $ (0.66 ) $ (1.04 ) $ (0.27 ) Weighted average common shares outstanding, basic and diluted 2,850,640 5,751,326 24,847,512 The following table presents the quarterly results of operations for 2017 (in thousands, except share and per share amounts): For the Quarter Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Operating expenses: Research and development $ 515 $ 977 $ 1,120 $ 1,118 General and administrative 55 118 238 316 Total operating expenses 570 1,095 1,358 1,434 Loss from operations (570 ) (1,095 ) (1,358 ) (1,434 ) Total other income (expense) — — (1 ) (1 ) Net loss $ (570 ) $ (1,095 ) $ (1,359 ) $ (1,435 ) Net loss per share, basic and diluted $ (0.20 ) $ (0.38 ) $ (0.48 ) $ (0.50 ) Weighted average common shares outstanding, basic and diluted 2,849,305 2,850,471 2,850,640 2,850,640

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company’s functional currency is the U.S. dollar.
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. The most significant estimates in the Company’s financial statements relate to the valuation of common stock and stock options. 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.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Cash Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and money market mutual funds. The Company classifies its marketable securities as “available-for-sale”, pursuant to ASC 320 Investments—Debt and Equity Securities There were no marketable securities with a maturity of greater than one year as of December 31, 2018. The following table presents the Company’s marketable securities as of December 31, 2018 (in thousands): December 31, 2018 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value Commercial paper $ 48,623 $ 5 $ (4 ) $ 48,624 U.S. treasury securities 17,028 — (2 ) 17,026 Asset-backed securities 13,904 — (16 ) 13,888 Total marketable securities $ 79,555 $ 5 $ (22 ) $ 79,538
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Cash, cash equivalents and marketable securities are financial instruments that are potentially subject to concentrations of credit risk. The Company’s deposits are in accounts at large financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the funds are held. The Company has no financial instruments with off-balance sheet risk of loss.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost less accumulated depreciation. Depreciation and amortization is calculated using the straight line method over the expected useful life of the asset, after the asset is placed in service. The Company generally uses the following depreciable lives for its major classifications of property and equipment: Description Useful Lives Equipment 5 years Leasehold Improvements Lease term Office Furniture and Fixtures 3 years Expenditures associated with upgrades and enhancements that improve, add functionality, or otherwise extend the life of property and equipment are capitalized, while expenditures that do not, such as repairs and maintenance, are expensed as incurred. The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. If the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount, an impairment loss would be recognized if the carrying value of the asset exceeds its fair value. Fair value is generally determined using discounted cash flows. No impairment losses have been recorded since inception.
Research and Development Costs	Research and Development Costs The Company’s research and development expenses consist primarily of costs associated with the Company’s clinical trials, salaries, payroll taxes, employee benefits, and equity-based compensation charges for those individuals involved in ongoing research and development efforts. Research and development costs are expensed as incurred. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made.
Fair Value Measurement	Fair Value Measurement ASC 820, Fair Value Measurements The accounting guidance classifies fair value measurements in one of the following three categories for disclosure purposes: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Inputs other than Level 1 prices for similar assets or liabilities that are directly or indirectly observable in the marketplace. Level 3: Unobservable inputs which are supported by little or no market activity and values determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation. The following table presents fair value of the Company’s marketable securities as of December 31, 2018 (in thousands): Fair Value Measurement as of December 31, 2018 Level 1 Level 2 Level 3 Total Commercial paper $ — $ 48,624 $ — $ 48,624 U.S. treasury securities 17,026 — — 17,026 Asset-backed securities — 13,888 — 13,888 Total $ 17,026 $ 62,512 $ — $ 79,538
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources. For the year ended December 31, 2018, comprehensive loss includes net loss and unrealized loss on marketable securities.
Share Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation awards in accordance with ASC 718, Compensation –Stock Compensation Non-employee options are remeasured to fair value each period and t . The use of the Black‑Scholes option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk‑free interest rates, and, for grants prior to the Company’s IPO, the value of the common stock. The expected life of stock options was estimated using the “simplified method,” as the Company has limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock options grants. The simplified method is based on the average of the vesting tranches and the contractual life of each grant. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies. The risk-free interest rate is based on U.S. Treasury notes with a term approximating the expected life of the option. Change in Accounting Principle - Stock-Based Compensation In the fourth quarter of 2018, the Company changed its policy for recognizing stock-based compensation expense for graded-vesting awards with service conditions only from the graded attribution method to the straight-line attribution method. The Company views these awards as single awards and believes that the straight-line attribution method more accurately reflects the pattern of service provided by the employees versus the graded attribution method which significantly front loads the stock-based compensation expense and does not appropriately match the expense with the services provided. In addition, based on research and analysis, the Company believes the straight-line attribution method for stock-based compensation expense for service condition-only awards is the predominant method used in its industry. The Company has concluded that the straight-line attribution method for stock-based compensation is a preferable accounting policy in accordance with ASC 250, Accounting Changes and Error Corrections and has applied this change retrospectively. The impact from the change in accounting policy for periods prior to January 1, 2018 was immaterial. The following tables present the effect of the change in accounting policy and its impact on key components of the Company’s 2018 financial statements (in thousands, except share and per share amounts): Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight- line Attribution Method Effect of Change Operating expenses: Research and development $ 12,939 $ 12,826 $ (113 ) General and administrative 10,441 9,052 (1,389 ) Total operating expenses 23,380 21,878 (1,502 ) Loss from operations (23,380 ) (21,878 ) 1,502 Other income (expense): Interest income 1,231 1,231 — Other expense (1 ) (1 ) — Total other income 1,230 1,230 — Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Net loss per common share, basic and diluted $ (1.51 ) $ (1.41 ) $ 0.10 Weighted average common shares outstanding, basic and diluted 14,662,751 14,662,751 Stock-based compensation expense included above: Research and development $ 472 $ 359 $ (113 ) General and administrative 3,281 1,892 (1,389 ) Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Other comprehensive loss: Unrealized loss on marketable securities (17 ) (17 ) — Comprehensive loss $ (22,167 ) $ (20,665 ) $ 1,502 As of December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Stockholders’ equity: Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 $ — $ — $ — Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2018; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018 3 3 — Treasury stock, at cost, 105,144 shares as of December 31, 2018 — — — Additional paid-in capital 124,028 122,526 (1,502 ) Accumulated deficit (34,585 ) (33,083 ) 1,502 Accumulated other comprehensive loss (17 ) (17 ) — Total stockholders’ equity $ 89,429 $ 89,429 $ — Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Cash flows from operating activities: Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Adjustments to reconcile net loss to net cash used in operating activities: Stock-based compensation 3,753 2,251 (1,502 ) Accretion of discounts on marketable securities (435 ) (435 ) — Depreciation expense 20 20 — Changes in operating assets and liabilities: Prepaid expenses and other assets (923 ) (923 ) — Accounts payable 769 769 — Accrued expenses 1,068 1,068 — Accounts payable and accrued expenses – related party 24 24 — Net cash used in operating activities $ (17,874 ) $ (17,874 ) $ —
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC 740, Income Taxes The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances.
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 Series A, Series B and Series C Preferred Stock, 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 December 31, 2018 2017 Shares issuable upon conversion of Series A Preferred — 12,428,773 Shares issuable upon conversion of Series B Preferred — 1,130,679 Shares issuable upon exercise of stock options 1,529,883 90,429 Non-vested shares under restricted stock grants 848,859 848,859
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In April 2016, the FASB issued ASU No. 2016-09, Share-Based Payment: Simplifying the Accounting for Share-Based Payments In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements The adoption of this standard is not expected to have a significant impact on the Company’s statements of operations and comprehensive loss and statements of cash flows. In June 2018, the FASB issued ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting Revenue from Contracts with Customers 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 will adopt this standard as of January 1, 2019 but In August 2018, the FASB issued ASU 2018-15, Intangibles–Goodwill and Other–Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Marketable Securities	The following table presents the Company’s marketable securities as of December 31, 2018 (in thousands): December 31, 2018 Amortized Gross Unrealized Gross Unrealized Fair Cost Gains Losses Value Commercial paper $ 48,623 $ 5 $ (4 ) $ 48,624 U.S. treasury securities 17,028 — (2 ) 17,026 Asset-backed securities 13,904 — (16 ) 13,888 Total marketable securities $ 79,555 $ 5 $ (22 ) $ 79,538
Schedule of Depreciable Lives of Property and Equipment	The Company generally uses the following depreciable lives for its major classifications of property and equipment: Description Useful Lives Equipment 5 years Leasehold Improvements Lease term Office Furniture and Fixtures 3 years
Schedule of Fair Value of Marketable Securities	The following table presents fair value of the Company’s marketable securities as of December 31, 2018 (in thousands): Fair Value Measurement as of December 31, 2018 Level 1 Level 2 Level 3 Total Commercial paper $ — $ 48,624 $ — $ 48,624 U.S. treasury securities 17,026 — — 17,026 Asset-backed securities — 13,888 — 13,888 Total $ 17,026 $ 62,512 $ — $ 79,538
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 key components of the Company’s 2018 financial statements (in thousands, except share and per share amounts): Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight- line Attribution Method Effect of Change Operating expenses: Research and development $ 12,939 $ 12,826 $ (113 ) General and administrative 10,441 9,052 (1,389 ) Total operating expenses 23,380 21,878 (1,502 ) Loss from operations (23,380 ) (21,878 ) 1,502 Other income (expense): Interest income 1,231 1,231 — Other expense (1 ) (1 ) — Total other income 1,230 1,230 — Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Net loss per common share, basic and diluted $ (1.51 ) $ (1.41 ) $ 0.10 Weighted average common shares outstanding, basic and diluted 14,662,751 14,662,751 Stock-based compensation expense included above: Research and development $ 472 $ 359 $ (113 ) General and administrative 3,281 1,892 (1,389 ) Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Other comprehensive loss: Unrealized loss on marketable securities (17 ) (17 ) — Comprehensive loss $ (22,167 ) $ (20,665 ) $ 1,502 As of December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Stockholders’ equity: Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 $ — $ — $ — Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2018; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018 3 3 — Treasury stock, at cost, 105,144 shares as of December 31, 2018 — — — Additional paid-in capital 124,028 122,526 (1,502 ) Accumulated deficit (34,585 ) (33,083 ) 1,502 Accumulated other comprehensive loss (17 ) (17 ) — Total stockholders’ equity $ 89,429 $ 89,429 $ — Year ended December 31, 2018 As Computed Under Graded Attribution Method As Reported Under Straight-line Attribution Method Effect of Change Cash flows from operating activities: Net loss $ (22,150 ) $ (20,648 ) $ 1,502 Adjustments to reconcile net loss to net cash used in operating activities: Stock-based compensation 3,753 2,251 (1,502 ) Accretion of discounts on marketable securities (435 ) (435 ) — Depreciation expense 20 20 — Changes in operating assets and liabilities: Prepaid expenses and other assets (923 ) (923 ) — Accounts payable 769 769 — Accrued expenses 1,068 1,068 — Accounts payable and accrued expenses – related party 24 24 — Net cash used in operating activities $ (17,874 ) $ (17,874 ) $ —
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 December 31, 2018 2017 Shares issuable upon conversion of Series A Preferred — 12,428,773 Shares issuable upon conversion of Series B Preferred — 1,130,679 Shares issuable upon exercise of stock options 1,529,883 90,429 Non-vested shares under restricted stock grants 848,859 848,859

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of (in thousands): As of December 31, 2018 Leasehold improvements $ 68 Office furniture and fixtures 48 Office equipment 28 Construction in process 131 275 Accumulated depreciation (20 ) Total property and equipment, net $ 255

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands): As of December 31, 2018 2017 Compensation and related costs $ 1,261 $ 49 Clinical trials and drug development — 233 Consulting - former Chief Scientific Officer 190 — Professional fees 56 129 Other 10 38 Total accrued expenses $ 1,517 $ 449

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	future minimum lease payments are as follows (in thousands): 2019 $ 136 2020 139 2021 58 Total minimum lease payments $ 333

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Restricted Stock Awards Activities	The following table summarizes restricted stock award activities for the year ended December 31, 2018: Weighted Average Grant Date Fair Number of Shares Value Nonvested at December 31, 2017 848,859 $ 0.33 Granted — — Nonvested at December 31, 2018 848,859 $ 0.33
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 statements of operations for the years ended December 31, 2018 and 2017 as follows (in thousands): For the Year Ended December 31, 2018 2017 Research and development $ 359 $ 82 General and administrative 1,892 — Total stock-based compensation $ 2,251 $ 82
Employee Stock Options [Member]
Assumptions Used to Estimate Fair Value	The grant date fair value of employee stock option awards is determined using the Black-Scholes option-pricing model. The following assumptions were used during the years ended December 31, 2018 and 2017 to estimate the fair value of employee stock option awards: For the Year Ended December 31, 2018 2017 Exercise price $6.52 - $16.32 $0.90 Risk-free rate of interest 2.58% - 3.13% 1.92% - 2.23% Expected term (years) 6.15 6.25 Expected stock price volatility 58.26% - 83.67% 79.02% - 79.12% Dividend yield — — Weighted average grant date fair value $6.95 $0.12
Schedule of Stock Option Activity	The following table summarizes the Company’s employee stock option activity under the 2013 Plan and the IPO Plan for the year ended December 31, 2018: Weighted average Aggregate Weighted average remaining contractual Intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2017 17,502 $ 0.90 9.0 Options granted 1,451,839 8.34 Exercised (8,385 ) 0.90 Forfeited/Cancelled (4,000 ) 16.32 Outstanding as of December 31, 2018 1,456,956 $ 8.27 9.2 $ 1,739,581 Options vested and exercisable as of December 31, 2018 192,018 $ 6.52 9.1 $ 312,995
Non-Employee Stock Option [Member]
Assumptions Used to Estimate Fair Value	Key assumptions used to estimate the fair value of the non-employee stock options remeasured during the years ended December 31, 2018 and 2017 are as follows: For the Year Ended December 31, 2018 2017 Exercise price $0.90 $0.90 Risk-free rate of interest 2.33% - 3.06% 2.16% - 2.48% Expected term (years) 7.53 8.43 Expected stock price volatility 58.26% - 83.81% 77.59% - 79.12% Dividend yield — — Weighted average fair value $9.22 $3.37
Schedule of Stock Option Activity	The following table summarizes the Company’s non-employee stock option activity under the 2013 Plan and the IPO Plan for the year ended December 31, 2018: Weighted average Aggregate Weighted average remaining contractual intrinsic Number of shares exercise price life (in years) value Outstanding as of December 31, 2017 72,927 $ 0.90 8.3 Granted — — Outstanding as of December 31, 2018 72,927 $ 0.90 7.3 $ 528,721 Options vested and exercisable as of December 31, 2018 55,910 $ 0.90 7.3 $ 405,348

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	There is no provision for income taxes as the Company has historically incurred operating losses and maintains a full valuation allowance against its deferred tax assets. Differences between the provision (benefit) for income taxes and income taxes at the statutory federal income tax rate are as follows (in thousands): For the Year Ended December 31, 2018 2017 Tax computed at statutory federal income tax rate 1 $ (4,336 ) $ (1,560 ) State taxes, net of federal benefit (1,478 ) (255 ) Rate change — 898 Permanent items 409 — Other (5 ) — Change in valuation allowance 5,410 917 Income tax provision (benefit) $ — $ — 1. Statutory U.S. federal income tax rate of 21% in 2018 and 35% in 2017.
Schedule of Components of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2018 2017 Deferred tax assets: Net operating loss carryovers $ 6,909 $ 1,946 Accrued expenses and other 510 27 Total deferred tax assets 7,419 1,973 Less valuation allowance (7,383 ) (1,973 ) Deferred tax asset, net of valuation allowance 36 — Deferred tax liabilities: Fixed assets (36 ) — Total deferred tax liabilities (36 ) — Net deferred tax assets $ — $ —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The impact from the change in accounting policy for periods prior to January 1, 2108 was immaterial. As a result, the quarterly periods in 2017 have not been adjusted for the change in accounting policy. 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 2018 quarters ended March 31, June 30, and September 30, 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 Quarter Ended As Computed Under Straight-line Attribution Method: March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Operating expenses: Research and development $ 927 $ 3,515 $ 3,467 $ 4,917 General and administrative 961 1,955 2,865 3,271 Total operating expenses 1,888 5,470 6,332 8,188 Loss from operations (1,888 ) (5,470 ) (6,332 ) (8,188 ) Total other income 41 153 426 610 Net loss $ (1,847 ) $ (5,317 ) $ (5,906 ) $ (7,578 ) Net loss per share, basic and diluted $ (0.65 ) $ (0.92 ) $ (0.24 ) $ (0.30 ) Weighted average common shares outstanding, basic and diluted 2,850,460 5,751,326 24,847,512 24,847,877 For the Quarter Ended As Previously Reported Under Graded Attribution Method: March 31, 2018 June 30, 2018 September 30, 2018 Operating expenses: Research and development $ 929 $ 3,609 $ 3,484 General and administrative 986 2,503 3,681 Total operating expenses 1,915 6,112 7,165 Loss from operations (1,915 ) (6,112 ) (7,165 ) Total other income 41 153 426 Net loss $ (1,874 ) $ (5,959 ) $ (6,739 ) Net loss per share, basic and diluted $ (0.66 ) $ (1.04 ) $ (0.27 ) Weighted average common shares outstanding, basic and diluted 2,850,640 5,751,326 24,847,512 The following table presents the quarterly results of operations for 2017 (in thousands, except share and per share amounts): For the Quarter Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Operating expenses: Research and development $ 515 $ 977 $ 1,120 $ 1,118 General and administrative 55 118 238 316 Total operating expenses 570 1,095 1,358 1,434 Loss from operations (570 ) (1,095 ) (1,358 ) (1,434 ) Total other income (expense) — — (1 ) (1 ) Net loss $ (570 ) $ (1,095 ) $ (1,359 ) $ (1,435 ) Net loss per share, basic and diluted $ (0.20 ) $ (0.38 ) $ (0.48 ) $ (0.50 ) Weighted average common shares outstanding, basic and diluted 2,849,305 2,850,471 2,850,640 2,850,640

Organization and Description _2

Organization and Description of Business Operations - Additional Information (Detail) $ / shares in Units, $ in Thousands	Jun. 19, 2018USD ($)$ / sharesshares	Jun. 04, 2018shares	Mar. 07, 2018USD ($)$ / sharesshares	Feb. 20, 2018USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares
Description Of Business [Line Items]
Stock split conversion ratio		1.714
Stock split description					No fractional shares were issued in connection with the stock split.
Number of fractional shares issued		0
Accumulated deficit | $					$ (33,083)	$ (12,435)
Issuance of common stock in connection with IPO, net of offering costs | $					$ 86,250
Common stock, authorized	200,000,000				200,000,000	33,236,900
Common stock, par value | $ / shares	$ 0.0001				$ 0.0001	$ 0.0001
Preferred stock, authorized	10,000,000				10,000,000	10,000,000
Preferred stock, par value | $ / shares	$ 0.0001				$ 0.0001	$ 0.0001
IPO [Member]
Description Of Business [Line Items]
Convertible preferred stock share issued	5,750,000				2,198,198
Public offering price of common stock | $ / shares	$ 15
Issuance of common stock in connection with IPO, net of offering costs | $	$ 78,400
Conversion of preferred stock into common stock, shares	16,246,872
Series C Convertible Preferred Stock [Member]
Description Of Business [Line Items]
Convertible preferred stock share issued			4,606,267	4,606,267
Convertible preferred stock share issued price per share | $ / shares			$ 4.559	$ 4.559
Proceed from issuance of convertible preferred stock | $			$ 21,000	$ 21,000	$ 21,000	$ 5,000

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)Segment
Significant Accounting Policies [Line Items]
Number Of operating segments | Segment		1
Marketable securities with maturity of greater than one year		$ 0
Financial instruments with off-balance sheet risk of loss		0
Impairment losses		$ 0
Expected dividend yield		0.00%
Expected dividend payments		$ 0
Topic 842 [Member] | Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Right-of-use asset and corresponding lease liability	$ 300,000

Significant Accounting Polici_5

Significant Accounting Policies - Schedule of Marketable Securities (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Marketable Securities [Line Items]
Amortized Cost	$ 79,555
Gross Unrealized Gains	5
Gross Unrealized Losses	(22)
Fair Value	79,538
Commercial Paper [Member]
Marketable Securities [Line Items]
Amortized Cost	48,623
Gross Unrealized Gains	5
Gross Unrealized Losses	(4)
Fair Value	48,624
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	17,028
Gross Unrealized Gains
Gross Unrealized Losses	(2)
Fair Value	17,026
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	13,904
Gross Unrealized Gains
Gross Unrealized Losses	(16)
Fair Value	$ 13,888

Significant Accounting Polici_6

Significant Accounting Policies - Schedule of Depreciable Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2018
Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Lives	5 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Lives	Lease term
Office Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Lives	3 years

Significant Accounting Polici_7

Significant Accounting Policies - Schedule of Fair Value of Marketable Securities (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Marketable Securities [Line Items]
Marketable securities	$ 79,538
Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	17,026
Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	62,512
Commercial Paper [Member]
Marketable Securities [Line Items]
Marketable securities	48,624
Commercial Paper [Member] | Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	48,624
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Marketable securities	17,026
U.S. Treasury Securities [Member] | Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	17,026
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Marketable securities	13,888
Asset Backed Securities [Member] | Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	$ 13,888

Significant Accounting Polici_8

Significant Accounting Policies - Schedule of Effect of the Change in Accounting Policy and its Impact on Key Components of Statements of Operations and Comprehensive Loss (Detail) - USD ($) $ / shares in Units, $ in Thousands	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
Operating expenses:
Research and development	$ 4,917	$ 3,467	$ 3,515	$ 927	$ 1,118	$ 1,120	$ 977	$ 515	$ 12,826	$ 3,730
General and administrative	3,271	2,865	1,955	961	316	238	118	55	9,052	727
Total operating expenses	8,188	6,332	5,470	1,888	1,434	1,358	1,095	570	21,878	4,457
Loss from operations	(8,188)	(6,332)	(5,470)	(1,888)	(1,434)	(1,358)	(1,095)	(570)	(21,878)	(4,457)
Other income (expense):
Interest income									1,231
Other expense									(1)
Total other income (expense)	610	426	153	41	(1)	(1)			1,230	(2)
Net loss	$ (7,578)	$ (5,906)	$ (5,317)	$ (1,847)	$ (1,435)	$ (1,359)	$ (1,095)	$ (570)	$ (20,648)	$ (4,459)
Net loss per share, basic and diluted	$ (0.30)	$ (0.24)	$ (0.92)	$ (0.65)	$ (0.50)	$ (0.48)	$ (0.38)	$ (0.20)	$ (1.41)	$ (1.56)
Weighted average common shares outstanding, basic and diluted	24,847,877	24,847,512	5,751,326	2,850,460	2,850,640	2,850,640	2,850,471	2,849,305	14,662,751	2,850,269
Stock-based compensation expense included above:
Stock-based compensation									$ 2,251	$ 82
Net loss	$ (7,578)	$ (5,906)	$ (5,317)	$ (1,847)	$ (1,435)	$ (1,359)	$ (1,095)	$ (570)	(20,648)	(4,459)
Other comprehensive loss:
Unrealized loss on marketable securities									(17)
Comprehensive loss									(20,665)	(4,459)
As Computed Under Graded Attribution Method [Member]
Operating expenses:
Research and development		3,484	3,609	929					12,939
General and administrative		3,681	2,503	986					10,441
Total operating expenses		7,165	6,112	1,915					23,380
Loss from operations		(7,165)	(6,112)	(1,915)					(23,380)
Other income (expense):
Interest income									1,231
Other expense									(1)
Total other income (expense)		426	153	41					1,230
Net loss		$ (6,739)	$ (5,959)	$ (1,874)					$ (22,150)
Net loss per share, basic and diluted		$ (0.27)	$ (1.04)	$ (0.66)					$ (1.51)
Weighted average common shares outstanding, basic and diluted		24,847,512	5,751,326	2,850,640					14,662,751
Stock-based compensation expense included above:
Stock-based compensation									$ 3,753
Net loss		$ (6,739)	$ (5,959)	$ (1,874)					(22,150)
Other comprehensive loss:
Unrealized loss on marketable securities									(17)
Comprehensive loss									(22,167)
Effect of Change [Member]
Operating expenses:
Research and development									(113)
General and administrative									(1,389)
Total operating expenses									(1,502)
Loss from operations									1,502
Other income (expense):
Net loss									$ 1,502
Net loss per share, basic and diluted									$ 0.10
Stock-based compensation expense included above:
Stock-based compensation									$ (1,502)
Net loss									1,502
Other comprehensive loss:
Comprehensive loss									1,502
Research and Development [Member]
Stock-based compensation expense included above:
Stock-based compensation									359	$ 82
Research and Development [Member] | As Computed Under Graded Attribution Method [Member]
Stock-based compensation expense included above:
Stock-based compensation									472
Research and Development [Member] | Effect of Change [Member]
Stock-based compensation expense included above:
Stock-based compensation									(113)
General and Administrative [Member]
Stock-based compensation expense included above:
Stock-based compensation									1,892
General and Administrative [Member] | As Computed Under Graded Attribution Method [Member]
Stock-based compensation expense included above:
Stock-based compensation									3,281
General and Administrative [Member] | Effect of Change [Member]
Stock-based compensation expense included above:
Stock-based compensation									$ (1,389)

Significant Accounting Polici_9

Significant Accounting Policies - Schedule of Effect of the Change in Accounting Policy and its Impact on Key Components of Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 and December 31, 2017
Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2018; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018	3
Treasury stock, at cost, 105,144 shares as of December 31, 2018 and December 31, 2017	0	0
Additional paid-in capital	122,526	5,394
Accumulated deficit	(33,083)	(12,435)
Accumulated other comprehensive loss	(17)
Total stockholders’ equity (deficit)	89,429	$ (7,041)	$ (2,664)
As Computed Under Graded Attribution Method [Member]
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 and December 31, 2017
Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2018; 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018	3
Treasury stock, at cost, 105,144 shares as of December 31, 2018 and December 31, 2017	0
Additional paid-in capital	124,028
Accumulated deficit	(34,585)
Accumulated other comprehensive loss	(17)
Total stockholders’ equity (deficit)	89,429
Effect of Change [Member]
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2018 and December 31, 2017
Treasury stock, at cost, 105,144 shares as of December 31, 2018 and December 31, 2017	0
Additional paid-in capital	(1,502)
Accumulated deficit	$ 1,502

Significant Accounting Polic_10

Significant Accounting Policies - Schedule of Effect of the Change in Accounting Policy and its Impact on Key Components of Balance Sheets (Parenthetical) (Detail) - $ / shares	Dec. 31, 2018	Jun. 19, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	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	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000	33,236,900
Common stock, shares issued	25,809,900		3,804,643
Common stock, shares outstanding	25,704,756		3,699,499
Treasury stock, shares	105,144		105,144

Significant Accounting Polic_11

Significant Accounting Policies - Schedule of Effect of the Change in Accounting Policy and its Impact on Key Components of Statements of Cash Flows (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
Cash flows from operating activities
Net loss	$ (7,578,000)	$ (5,906,000)	$ (5,317,000)	$ (1,847,000)	$ (1,435,000)	$ (1,359,000)	$ (1,095,000)	$ (570,000)	$ (20,648,000)	$ (4,459,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation									2,251,000	82,000
Accretion of discounts on marketable securities									(435,000)
Depreciation expense									20,294
Changes in operating assets and liabilities:
Prepaid expenses and other assets									(923,000)	(403,000)
Accounts payable									769,000	86,000
Accrued expenses									1,068,000	133,000
Accounts payable and accrued expenses - related party									24,000	(22,000)
Net cash used in operating activities									(17,874,000)	$ (4,583,000)
As Computed Under Graded Attribution Method [Member]
Cash flows from operating activities
Net loss		$ (6,739,000)	$ (5,959,000)	$ (1,874,000)					(22,150,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation									3,753,000
Accretion of discounts on marketable securities									(435,000)
Depreciation expense									20,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets									(923,000)
Accounts payable									769,000
Accrued expenses									1,068,000
Accounts payable and accrued expenses - related party									24,000
Net cash used in operating activities									(17,874,000)
Effect of Change [Member]
Cash flows from operating activities
Net loss									1,502,000
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation									$ (1,502,000)

Significant Accounting Polic_12

Significant Accounting Policies - Schedule of Potential Shares Outstanding Excluded in Computation of Diluted Net Loss Per Common Share (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares issuable upon conversion of Series A Preferred [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities that could potentially dilute basic earnings per share		12,428,773
Shares issuable upon conversion of Series B Preferred [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities that could potentially dilute basic earnings per share		1,130,679
Employee Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities that could potentially dilute basic earnings per share	1,529,883	90,429
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

Property and Equipment - Schedu

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

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
Property Plant And Equipment [Abstract]
Depreciation expense	$ 20,294

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - PBM Capital Group, LLC [Member] - USD ($)	Jan. 01, 2019	Dec. 02, 2015	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Services agreement initial term		12 months
Expenses incurred under services agreement				$ 457,500	$ 30,000
Due to related party			$ 38,000	$ 38,000	$ 14,000
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			$ 50,000
Amended Service Agreement [Member] | Subsequent Event [Member]
Related Party Transaction [Line Items]
Monthly management fee payable	$ 26,333

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Compensation and related costs	$ 1,261	$ 49
Clinical trials and drug development	0	233
Consulting - former Chief Scientific Officer	190	0
Professional fees	56	129
Other	10	38
Total accrued expenses	$ 1,517	$ 449

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)claim$ / h	Dec. 31, 2017USD ($)claim	Mar. 22, 2018USD ($)
Loss Contingencies [Line Items]
Number of litigation against the company | claim	0	0
Accrued expenses	$ 1,517,000	$ 449,000
Facility Lease [Member]
Loss Contingencies [Line Items]
Sublease agreement expiry date	May 31, 2021
Rent expense	$ 97,503
Former Chief Executive Officer [Member]
Loss Contingencies [Line Items]
Consulting agreement required cash payment per month	$ 29,375
Consulting payment per hour | $ / h	300
Accrued expenses	$ 200,000
Crude Cantharidin Material [Member]
Loss Contingencies [Line Items]
Purchase Commitment	$ 1,500,000		$ 2,300,000
Purchase agreement term	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Rental Payments for Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 136
2,020	139
2,021	58
Total minimum lease payments	$ 333

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	Jun. 19, 2018USD ($)$ / sharesshares	Mar. 07, 2018USD ($)$ / sharesshares	Feb. 20, 2018USD ($)$ / sharesshares	Dec. 15, 2017USD ($)$ / sharesshares	Dec. 02, 2015USD ($)Investorshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
Stockholders Equity [Line Items]
Common stock, authorized | shares	200,000,000					200,000,000	33,236,900
Common stock, par value | $ / shares	$ 0.0001					$ 0.0001	$ 0.0001
Common stock, voting right						1
Proceeds from initial public offering						$ 86,250
Repurchase of stocks | shares						105,144	105,144
Stock-based compensation						$ 2,251	$ 82
Preferred stock shares issued | shares						0	0
Series A Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock shares issued | shares					21,302,972
Proceeds from issuance of convertible preferred stock					$ 1,900
Conversion of notes payable and accrued interest					500
Preferred stock subscription receivable					8,500
Stock issuance cost					$ 400		$ 281
Proceeds from stock subscription receivable							8,000
Number of investors | Investor					14
Gross proceed							8,000
Series A Convertible Preferred Stock [Member] | PBMVP Holdings [Member]
Stockholders Equity [Line Items]
Proceeds from stock subscription receivable								$ 500
Series B Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Common stock issued and sale | shares				1,937,984
Issuance price | $ / shares				$ 2.58
Gross proceed				$ 5,000
Series C Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Common stock issued and sale | shares		4,606,267	4,606,267
Stock issuance cost						$ 7
Issuance price | $ / shares		$ 4.559	$ 4.559
Gross proceed		$ 21,000	$ 21,000			$ 21,000	$ 5,000
Amended and Restated Agreement [Member]
Stockholders Equity [Line Items]
Repurchase of stocks | shares						848,859
Repurchase price | $ / shares						$ 0.0001
Stock-based compensation						$ 0
IPO [Member]
Stockholders Equity [Line Items]
Common stock issued and sale | shares	5,750,000					2,198,198
Offering price | $ / shares	$ 15
Proceeds from initial public offering	$ 78,400
Stock issuance cost						$ 7,874
Conversion of preferred stock into common stock, shares | shares	16,246,872
IPO [Member] | Series A Preferred Stock [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares | shares	12,428,773
IPO [Member] | Series B Preferred Stock [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares | shares	1,130,679
IPO [Member] | Series C Preferred Stock [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares | shares	2,687,420

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jun. 19, 2018	Dec. 31, 2018	Dec. 31, 2017
Employee Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted contractual term		10 years
Stock option vesting term, description		Through 2,022
Stock options expiration term, description		Through 2,028
Share based compensation arrangement by share based payment award stock option, shares granted		1,451,839
Weighted average grant date fair value		$ 6.95	$ 0.12
Employee Stock Options [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of stock subject to vesting (as a percent)		25.00%
Stock vesting period		12 months
Employee Stock Options [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of stock subject to vesting (as a percent)		75.00%
Stock vesting period		12 months
Non-Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award stock option, shares granted		0	0
Employee And Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation		$ 8.1
Weighted-average stock option recognize period		3 years 1 month 6 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation		$ 0.3
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for issuance		3,738,199
Shares issued	5,750,000	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		1,958,033

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used to Estimate Fair Value Employee Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Dividend yield	0.00%
Employee Stock Options [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	$ 8.34	$ 0.90
Risk-free rate of interest, minimum	2.58%	1.92%
Risk-free rate of interest, maximum	3.13%	2.23%
Expected term (years)	6 years 1 month 24 days	6 years 2 months 30 days
Expected stock price volatility, minimum	58.26%	79.02%
Expected stock price volatility, maximum	83.67%	79.12%
Dividend yield	0.00%	0.00%
Weighted average grant date fair value	$ 6.95	$ 0.12
Employee Stock Options [Member] | Minimum [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	6.52
Employee Stock Options [Member] | Maximum [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	$ 16.32

Stock-Based Compensation - As_2

Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Non-employee Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Dividend yield	0.00%
Non-Employee Stock Option [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	$ 0.90	$ 0.90
Risk-free rate of interest, minimum	2.59%	2.16%
Risk-free rate of interest, maximum	3.06%	2.48%
Expected term (years)	7 years 6 months 10 days	8 years 5 months 5 days
Expected stock price volatility, minimum	58.26%	77.59%
Expected stock price volatility, maximum	79.34%	79.12%
Dividend yield	0.00%	0.00%
Weighted average fair value	$ 9.22	$ 3.37

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Employee Stock Option Activity (Detail) - Employee Stock Options [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Outstanding Beginning Balance	17,502
Number of shares, Options granted	1,451,839
Number of shares, Exercised	(8,385)
Number of shares, Forfeited/Cancelled	(4,000)
Number of shares, Outstanding Ending Balance	1,456,956	17,502
Number of shares, Options vested and exercisable Ending Balance	192,018
Weighted average exercise price, Outstanding Beginning Balance	$ 0.90
Weighted average exercise price, Options granted	8.34	$ 0.90
Weighted average exercise price, Exercised	0.90
Weighted average exercise price, Forfeited/Cancelled	16.32
Weighted average exercise price, Outstanding Ending Balance	8.27	$ 0.90
Weighted average exercise price, Options vested and exercisable Ending Balance	$ 6.52
Weighted average remaining contractual life (in years), Outstanding	9 years 2 months 12 days	9 years
Weighted average remaining contractual life (in years), Options vested and exercisable	9 years 1 month 6 days
Aggregate intrinsic value, Outstanding Ending Balance	$ 1,739,581
Aggregate intrinsic value, Options vested and exercisable Ending Balance	$ 312,995

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Company's Non-Employee Stock Option Activity (Detail) - Non-Employee Stock Option [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Outstanding Beginning Balance	72,927
Number of shares, Options granted	0	0
Number of shares, Outstanding Ending Balance	72,927	72,927
Number of shares, Options vested and exercisable Ending Balance	55,910
Weighted average exercise price, Outstanding Beginning Balance	$ 0.90
Weighted average exercise price, Options granted	0
Weighted average exercise price, Outstanding Ending Balance	0.90	$ 0.90
Weighted average exercise price, Options vested and exercisable Ending Balance	$ 0.90
Weighted average remaining contractual life (in years), Outstanding	7 years 3 months 19 days	8 years 3 months 19 days
Weighted average remaining contractual life (in years), Options vested and exercisable	7 years 3 months 19 days
Aggregate intrinsic value, Outstanding Ending Balance	$ 528,721
Aggregate intrinsic value, Options vested and exercisable Ending Balance	$ 405,348

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Restricted Stock Awards Activities (Detail) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Number of Shares, Beginning Balance | shares	848,859
Nonvested, Number of Shares, Granted | shares	0
Nonvested, Number of Shares, Ending Balance | shares	848,859
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 0.33
Nonvested, Weighted Average Grant Date Fair Value, Granted | $ / shares	0
Nonvested, Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 0.33

Stock-Based Compensation - Sc_4

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 2,251	$ 82
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	359	$ 82
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 1,892

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes at U.S. Federal Statutory Rate to Provision for Income Taxes (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax computed at statutory federal income tax rate	[1]	$ (4,336)	$ (1,560)
State taxes, net of federal benefit		(1,478)	(255)
Rate change			898
Permanent items		409
Other		(5)
Change in valuation allowance		$ 5,410	$ 917
[1]	Statutory U.S. federal income tax rate of 21% in 2018 and 35% in 2017.

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of Income Taxes at U.S. Federal Statutory Rate to Provision for Income Taxes (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory U.S. federal income tax rate	21.00%	35.00%

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryovers	$ 6,909	$ 1,946
Accrued expenses and other	510	27
Total deferred tax assets	7,419	1,973
Less valuation allowance	(7,383)	$ (1,973)
Deferred tax asset, net of valuation allowance	36
Deferred tax liabilities:
Fixed assets	(36)
Total deferred tax liabilities	$ (36)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 100	$ 100
Accrued interest or penalties related to uncertain tax positions	0
Interest or penalties related to uncertain tax positions recognized in income tax expense	0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	24,100
State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 24,100
Net Operating Loss Carryforwards Generated Prior to 2018 [Member]
Operating Loss Carryforwards [Line Items]
Federal and state net operating loss carryforwards, expiration date	2,033

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	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
Operating expenses:
Research and development	$ 4,917	$ 3,467	$ 3,515	$ 927	$ 1,118	$ 1,120	$ 977	$ 515	$ 12,826	$ 3,730
General and administrative	3,271	2,865	1,955	961	316	238	118	55	9,052	727
Total operating expenses	8,188	6,332	5,470	1,888	1,434	1,358	1,095	570	21,878	4,457
Loss from operations	(8,188)	(6,332)	(5,470)	(1,888)	(1,434)	(1,358)	(1,095)	(570)	(21,878)	(4,457)
Total other income (expense)	610	426	153	41	(1)	(1)			1,230	(2)
Net loss	$ (7,578)	$ (5,906)	$ (5,317)	$ (1,847)	$ (1,435)	$ (1,359)	$ (1,095)	$ (570)	$ (20,648)	$ (4,459)
Net loss per share, basic and diluted	$ (0.30)	$ (0.24)	$ (0.92)	$ (0.65)	$ (0.50)	$ (0.48)	$ (0.38)	$ (0.20)	$ (1.41)	$ (1.56)
Weighted average common shares outstanding, basic and diluted	24,847,877	24,847,512	5,751,326	2,850,460	2,850,640	2,850,640	2,850,471	2,849,305	14,662,751	2,850,269
As Computed Under Graded Attribution Method [Member]
Operating expenses:
Research and development		$ 3,484	$ 3,609	$ 929					$ 12,939
General and administrative		3,681	2,503	986					10,441
Total operating expenses		7,165	6,112	1,915					23,380
Loss from operations		(7,165)	(6,112)	(1,915)					(23,380)
Total other income (expense)		426	153	41					1,230
Net loss		$ (6,739)	$ (5,959)	$ (1,874)					$ (22,150)
Net loss per share, basic and diluted		$ (0.27)	$ (1.04)	$ (0.66)					$ (1.51)
Weighted average common shares outstanding, basic and diluted		24,847,512	5,751,326	2,850,640					14,662,751