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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Mar. 06, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Trading Symbol	VRCA
Entity Interactive Data Current	Yes
Entity Registrant Name	Verrica Pharmaceuticals Inc.
Entity Central Index Key	0001660334
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 181.4
Entity Common Stock, Shares Outstanding		25,814,493
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transaction Period	true
Entity File Number	001-38529
Entity Tax Identification Number	46-3137900
Title of 12(b) Security	Common Stock, $0.0001 par value
Security Exchange Name	NASDAQ
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	10 North High Street
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	West Chester
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19380
City Area Code	484
Local Phone Number	453-3300

BALANCE SHEETS - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 9,241,000	$ 10,271,000
Marketable securities	52,776,000	79,538,000
Prepaid expenses and other assets	2,966,000	1,343,000
Total current assets	64,983,000	91,152,000
Property and equipment, net	2,090,000	255,000
Operating lease right-of-use asset	111,000
Deposits	1,240,000	499,000
Total assets	68,424,000	91,906,000
Current liabilities:
Accounts payable	1,185,000	922,000
Accrued expenses	2,036,000	1,517,000
Operating lease liability	130,000
Accounts payable and accrued expenses - related party		38,000
Total current liabilities	3,351,000	2,477,000
Operating lease liability	58,000
Total liabilities	3,409,000	2,477,000
Commitments and Contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2019 and 2018
Common stock, $0.0001 par value; 200,000,000 authorized as of December 31, 2019 and 2018; 25,912,137 shares issued and 25,786,330 shares outstanding as of December 31, 2019 and 25,809,900 shares issued and 25,704,756 shares outstanding as of December 31, 2018	3,000	3,000
Treasury stock, at cost, 105,144 shares as of December 31, 2019 and 2018	0	0
Additional paid-in capital	126,594,000	122,526,000
Subscription receivable	(410,000)
Accumulated deficit	(61,192,000)	(33,083,000)
Accumulated other comprehensive gain/(loss)	20,000	(17,000)
Total stockholders’ equity	65,015,000	89,429,000
Total liabilities and stockholders’ equity	$ 68,424,000	$ 91,906,000

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	25,912,137	25,809,900
Common stock, shares outstanding	25,786,330	25,704,756
Treasury stock, shares	105,144	105,144

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 15,436	$ 12,826
General and administrative	14,644	9,052
Total operating expenses	30,080	21,878
Loss from operations	(30,080)	(21,878)
Other income (expense):
Interest income	1,877	1,231
Other expense	(4)	(1)
Total other income	1,873	1,230
Net loss	$ (28,207)	$ (20,648)
Net loss per share, basic and diluted	$ (1.13)	$ (1.41)
Weighted average common shares outstanding, basic and diluted	24,897,889	14,662,751
Other comprehensive loss:
Unrealized gain/(loss) on marketable securities	$ 37	$ (17)
Comprehensive loss	$ (28,170)	$ (20,665)

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]	Subscription Receivable [Member]	Accumulated Deficit [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2017	$ (7,041)					$ 5,394		$ (12,435)
Beginning Balance (shares) at Dec. 31, 2017		21,302,972	1,937,984
Beginning Balance at Dec. 31, 2017		$ 10,508	$ 5,000
Beginning Balance (shares) at Dec. 31, 2017					3,804,643				105,144
Stock-based compensation	2,251					2,251
Exercise of stock options	7					7
Exercise of stock options (shares)					8,385
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 gain (loss) on marketable securities	(17)									$ (17)
Series C convertible preferred stock				$ 21,000
Series C convertible preferred stock (shares)				4,606,267
Issuance costs for Series C preferred				$ (7)
Ending Balance at Dec. 31, 2018	89,429				$ 3	122,526		(33,083)		(17)
Ending Balance (shares) at Dec. 31, 2018					25,809,900				105,144
Stock-based compensation	3,333					3,333
Exercise of stock options	423					423
Exercise of stock options (shares)					74,908
Subscription receivable						410	$ (410)
Subscription receivable (shares)					27,329
Adoption of ASU 2018-07 (Note 2)						(98)		98
Net loss	(28,207)							(28,207)
Unrealized gain (loss) on marketable securities	37									37
Ending Balance at Dec. 31, 2019	$ 65,015				$ 3	$ 126,594	$ (410)	$ (61,192)		$ 20
Ending Balance (shares) at Dec. 31, 2019					25,912,137				105,144

STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (28,207,000)	$ (20,648,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,333,000	2,251,000
Accretion of discounts on marketable securities	(1,063,000)	(435,000)
Depreciation expense	64,200	20,300
Amortization on operating lease right-of-use asset	193,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,621,000)	(923,000)
Accounts payable	263,000	769,000
Accrued expenses	(213,000)	1,068,000
Accounts payable and accrued expenses - related party	(38,000)	24,000
Operating lease liability	(119,000)
Net cash used in operating activities	(27,408,000)	(17,874,000)
Cash flows from investing activities
Purchases of marketable securities	(89,854,000)	(79,120,000)
Sales and maturities of marketable securities	117,715,000
Purchases of property, plant and equipment	(682,000)	(774,000)
Increase in deposits	(1,224,000)
Net cash provided by (used in) investing activities	25,955,000	(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	423,000	7,000
Net cash provided by financing activities	423,000	99,376,000
Net (decrease) increase in cash and cash equivalents	(1,030,000)	1,608,000
Cash and cash equivalents at the beginning of the year	10,271,000	8,663,000
Cash and cash equivalents at the end of the year	9,241,000	10,271,000
Supplemental disclosure of noncash investing and financing activities:
Change in unrealized gain/(loss) on marketable securities	37,000	(17,000)
Subscription receivable on exercise of options	410,000
Conversion of preferred stock into common stock		36,501,000
Accrual for purchases of property, plant and equipment	$ 733,000
IPO [Member]
Cash flows from financing activities
Payment of stock issuance costs		(7,874,000)
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

Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

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, carries them at fair market value and classifies them as current assets on its balance sheets. There were no marketable securities with a maturity of greater than one year as of December 31, 2019. Unrealized gains and losses on marketable debt securities are recorded as a separate component of accumulated other comprehensive loss included in stockholders’ equity.

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, provides guidance on the development and disclosure of fair value measurements. Under this accounting guidance, fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability.

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.

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, 2019, comprehensive loss includes net loss and unrealized gain (loss) on marketable securities.

Stock-Based Compensation

The Company accounts for stock-based compensation awards in accordance with ASC 718, Compensation –Stock Compensation. The Company uses the Black-Scholes option-pricing model to value its stock option awards. For stock-based awards granted to employees, non-employees and to members of the board of directors for their services, the Company estimates the grant date fair value of each option award and recognizes employee compensation expense on a straight-line basis over the vesting period of the award.

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. Expected dividend yield is zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The fair value of restricted stock awards are based on the closing price of the Company’s common stock on the grant date.

Income Taxes

Income taxes are recorded in accordance with ASC 740, Income Taxes, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

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 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,
	2019		2018
Shares issuable upon exercise of stock options		1,914,545		1,529,883
Non-vested shares under restricted stock grants		1,148,859		848,859

Recently Adopted Accounting Pronouncements

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments granted to nonemployees for goods and services. Under the ASU, most of the guidance on such payments to nonemployees would be aligned with the requirements for share-based payments granted to employees. The changes take effect for public companies for fiscal years starting after December 15, 2018, including interim periods within that fiscal year. The Company adopted this ASU as of January 1, 2019 and recorded an adjustment to accumulated deficit and additional paid-in capital of $98,000.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by, among other provisions, recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous GAAP. For public companies, ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) using a modified retrospective approach and early adoption is permitted. In transition, entities may also elect a package of practical expedients that must be applied in its entirety to all leases commencing before the adoption date, unless the lease is modified, and permits entities to not reassess (a) the existence of a lease, (b) lease classification or (c) determination of initial direct costs, as of the adoption date, which effectively allows entities to carryforward accounting conclusions under previous GAAP. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, which provides entities an optional transition method to apply the guidance under Topic 842 as of the adoption date, rather than as of the earliest period presented. The Company adopted Topic 842 on January 1, 2019, using the optional transition method to apply the new guidance as of January 1, 2019, rather than as of the earliest period presented, and elected the package of practical expedients described above. Based on the analysis, on January 1, 2019, the Company recorded an operating lease right-of-use asset of $304,000 and an operating lease liability of $306,000 and eliminated deferred rent of $2,000. See Note 10 for additional information.

Recently Issued Accounting Pronouncements Not Yet Adopted

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework–Changes to the Disclosure Requirements for Fair Value Measurement, which makes a number of changes meant to add, modify or remove certain disclosure requirements associated with the movement amongst or hierarchy associated with Level 1, Level 2 and Level 3 fair value measurements. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted upon issuance of the update. The Company does not expect the adoption of this guidance to have a material impact on its financial statements.

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, which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The guidance also requires the entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement, which includes reasonably certain renewals. The guidance becomes effective for the Company in the year ending December 31, 2020 and early adoption is permitted. The Company does not expect the adoption of this guidance to have a material impact on its financial statements.

Investments In Marketable Securities

12 Months Ended

Dec. 31, 2019

Investments [Abstract]

Investments in Marketable Securities

Note 3—Investments in Marketable Securities

Investments in marketable securities consisted of the following as of December 31, 2019 and 2018 (in thousands):

	December 31, 2019
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
U.S. treasury securities	$	7,397	$	3	$	—		$	7,400
Commercial paper		31,913		7		(1	)		31,919
Asset-backed securities		13,446		11		—			13,457
Total marketable securities	$	52,756	$	21	$	(1	)	$	52,776

	December 31, 2018
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
U.S. treasury securities	$	17,028	$	—	$	(2	)	$	17,026
Commercial paper		48,623		5		(4	)		48,624
Asset-backed securities		13,904		—		(16	)		13,888
Total marketable securities	$	79,555	$	5	$	(22	)	$	79,538

Unrealized gains and losses on marketable securities are recorded as a separate component of accumulated other comprehensive gain (loss) included in stockholders’ equity. Realized gains (losses) are included in interest income (expense) in the statement of operations and comprehensive loss on a specific identification basis. The Company did not record any realized gains or losses during the years ended December 31, 2019 and 2018. To date, the Company has not recorded any impairment charges on marketable securities related to other-than-temporary declines in market value.

Accretion of bond discount on marketable securities and interest income on marketable securities is recorded as interest income on the statement of operations and comprehensive loss.

There were no marketable securities with a maturity of greater than one year for either period presented. Unrealized gains and losses on marketable debt securities are recorded as a separate component of accumulated other comprehensive gain (loss) included in stockholders’ equity.

The following tables presents fair value by level in accordance with ASC 820 (see Note 2) of the Company’s marketable securities (in thousands):

	Fair Value Measurement as of December 31, 2019
	Level 1		Level 2		Level 3		Total
U.S. treasury securities	$	7,400	$	—	$	—	$	7,400
Commercial paper		—		31,919		—		31,919
Asset-backed securities		—		13,457		—		13,457
Total	$	7,400	$	45,376	$	—	$	52,776

	Fair Value Measurement as of December 31, 2018
	Level 1		Level 2		Level 3		Total
U.S. treasury securities	$	17,026	$	—	$	—	$	17,026
Commercial paper		—		48,624		—		48,624
Asset-backed securities		—		13,888		—		13,888
Total	$	17,026	$	62,512	$	—	$	79,538

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 9—Stock-Based Compensation

In June 2018, the Board adopted and approved the 2018 Equity Incentive Plan (the “2018 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 2018 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 2018 Plan, no further grants may be made under the 2013 Plan.

The 2018 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 2018 Plan also provides for the grant of performance-based cash awards to employees, including officers, consultants and directors. The Company initially reserved 3,738,199 shares of common stock for issuance under the 2018 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 2018 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 2018 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, 2019, 2,199,325 shares were available for grant under the 2018 Plan.

Stock Options

The Company’s employee and non-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, 2019 have a maximum contractual term of 10 years. The stock options are subject to time vesting requirements through 2023, are nontransferable, and have term expiration dates set to expire through 2029.

The grant date fair value of employee and non-employee stock option awards is determined using the Black-Scholes option-pricing model. The following assumptions were used during the years ended December 31, 2019 and 2018 to estimate the fair value of employee and non-employee stock option awards:

	For the Year Ended December 31,
	2019	2018
Exercise price	$7.95 - $14.65	$6.52 - $16.32
Risk-free rate of interest	1.42% - 2.56%	2.58% - 3.13%
Expected term (years)	5.98	6.15
Expected stock price volatility	72.1% - 78.3%	58.3% - 83.7%
Dividend yield	—	—
Weighted average grant date fair value	$7.84	$6.95

The following table summarizes the Company’s employee and non-employee stock option activity under the 2013 Plan and 2018 Plan for the years ended December 31, 2019 and 2018:

						Weighted average
				Weighted average		remaining contractual		Aggregate intrinsic
	Number of shares			exercise price		life (in years)		value
Outstanding as of December 31, 2017		90,429		$	0.90
Options granted		1,451,839			8.34
Exercised		(8,385	)		0.90
Forfeited		(4,000	)		16.32
Outstanding as of December 31, 2018		1,529,883			8.03
Options granted		830,918			11.57
Exercised		(102,237	)		8.15
Forfeited		(344,019	)		10.37
Outstanding as of December 31, 2019		1,914,545		$	9.14		8.5	$	12,953,956
Options vested and exercisable as of December 31, 2019		616,994		$	7.21		7.9	$	5,362,458

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 and non-employee stock options granted during the years ended December 31, 2019 and 2018 was $7.84 and $6.95, respectively. As of December 31, 2019, the total unrecognized compensation related to unvested employee and non-employee stock option awards granted was $8.7 million, which the Company expects to recognize over a weighted-average period of 2.8 years.

The Company utilizes a designated broker to process exercises of stock options. In late December 2019, there was an exercise of 27,329 vested stock options for which the Company did not receive the net proceeds from the designated broker until early January 2020. The net proceeds have been reflected as a stock subscription receivable as of December 31, 2019 in the balance sheet.

Restricted Stock

Pursuant to an Amended and Restated Agreement between the Company and the former CSO, 848,859 shares held by the former CSO are subject to repurchase at $0.0001 per share in the event the CSO ceases to be a consultant. See Note 8.

The following table summarizes restricted stock awards related to the Amended and Restated Agreement:

			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
Granted		—		—
Nonvested at December 31, 2019		848,859	$	0.33

On November 27, 2019, the Company granted 300,000 restricted stock units to its executive officers to key executives. The restricted stock units vest 50% upon receipt of regulatory approval of the Company’s new drug application for VP-102 for the treatment of molluscum (the “Approval Date”) and 50% shall vest on the one year anniversary of the Approval Date subject to the holders’ continuous service through each applicable date.

No compensation expenses has been recognized for these nonvested restricted stock units and the shares subject to the Amended and Restated Agreement as these shares are performance based and the triggering event was not determined to be probable as of December 31, 2019. As of December 31, 2019, the total unrecognized compensation expense related to the restricted stock units and shares subject to the Amended and Restated Agreement was $5.0 million.

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, 2019 and 2018 as follows (in thousands):

	For the Year Ended December 31,
	2019		2018
Research and development	$	609	$	359
General and administrative		2,724		1,892
Total stock-based compensation	$	3,333	$	2,251

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

Note 10—Leases

Effective January 1, 2019, the Company accounts for its leases under ASC 842, Leases (Topic 842). Under this guidance, arrangements meeting the definition of a lease are classified as operating or financing leases and are recorded on the balance sheet as both a right-of-use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease, if available, otherwise at the Company’s incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right-of-use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right-of-use asset result in straight-line rent expense over the lease term. Variable lease expenses, if any, are recorded when incurred.

In calculating the right-of-use asset and lease liability, the Company elected to combine lease and non-lease components. The Company excludes short-term leases having initial terms of 12 months or less from the new guidance as an accounting policy election and recognizes rent expense on a straight-line basis over the lease term. The Company continues to account for leases in the prior period financial statements under the previous guidance in ASC 840, Leases.

The Company leases office space in West Chester, Pennsylvania under an agreement classified as an operating lease that expires in May 2021. The Company does not act as a lessor or have any leases classified as finance leases. On July 1, 2019, the Company entered into a lease for 5,829 square feet of office space located in West Chester, Pennsylvania that is expected to serve as the Company’s new headquarters. The initial term of the lease is seven years and the base rent over the initial term is $1.3 million. The Company plans to vacate its existing headquarters space as soon as the new space is available which is currently expected on or around June 1, 2020. As a result, amortization of the right-of-use asset associated with the current property lease is now being amortized over the revised remaining useful life. In addition, the useful life of associated leasehold improvements has been accelerated to reflect the expected abandonment of the property, such that they will be fully amortized when the property is vacated.

As of December 31, 2019, the Company had an operating lease liability of $188,000, of which $130,000 was classified as current, and an operating right-of-use asset of $111,000.

The components of lease expense are as follows (in thousands):

	For the Year Ended December 31,
	2019		2018
Operating lease:
Operating lease costs	$	211	$	98
Short-term lease costs		17		—
Total rent expense	$	228	$	98

Maturities of the Company’s operating lease excluding short-term leases as of December 31, 2018:

2019	$	136
2020		139
2021		58
Total lease payments	$	333

Maturities of the Company’s operating lease as of December 31, 2019, excluding short-term leases and the new headquarters lease in West Chester, which is estimated to commence in June 2020, are as follows (in thousands):



2020	$	139
2021		58
Total lease payments		197
Less imputed interest		(9	)
Total rent expense	$	188

The remaining term of the Company’s operating lease was 1.4 years and the discount rate used to measure the present value of the Company’s operating lease liability was 6.75% as of December 31, 2019.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

Note 11–Income Taxes

There is no provision for income taxes as the Company has incurred operating losses since inception 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,
	2019			2018
Tax computed at statutory federal income tax rate	$	(5,923	)	$	(4,336	)
State taxes, net of federal benefit		(2,312	)		(1,478	)
Permanent items		70			409
Other		(285	)		(5	)
Change in valuation allowance		8,450			5,410
Income tax provision (benefit)	$	—		$	—

Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands):

	As of December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryovers	$	14,370		$	6,909
Other		1,483			510
Total deferred tax assets		15,853			7,419
Less valuation allowance		(15,835	)		(7,383	)
Deferred tax asset, net of valuation allowance		18			36
Deferred tax liabilities:
Fixed assets		(18	)		(36	)
Total deferred tax liabilities		(18	)		(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, 2019, the Company had federal and state net operating loss carryforwards of approximately $49.9 million and $50.2 million, respectively. The federal net operating loss carryforwards included in the foregoing totals that were generated prior to 2018 (federal of approximately $6.9 million) 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. In addition, under Section 382 of the Internal Revenue Code of 1986, as amended, and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which is generally defined as a greater than 50% change, by value, in its equity ownership over a three-year period, the corporation’s ability to use its pre-change net operating loss carryforwards may be limited.

As of December 31, 2019 and 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 $1.5 million and $0.1 million as of December 31, 2019 and 2018. The Company will recognize interest and penalties, if any, related to uncertain tax positions in income tax expense. As of December 31, 2019 and 2018, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations. The Company does not anticipate a material change to unrecognized tax benefits in the next twelve months.

The 2016 and subsequent federal and state tax years for the Company remain open for the assessment of income taxes.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

Note 12–Selected Quarterly Financial Data (Unaudited)

The following tables present the quarterly results of operations for 2019 and 2018 (in thousands, except share and per share amounts):

	For the Quarter Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Operating expenses:
Research and development	$	4,487		$	3,928		$	3,049		$	3,972
General and administrative		3,539			3,593			3,494			4,018
Total operating expenses		8,026			7,521			6,543			7,990
Loss from operations		(8,026	)		(7,521	)		(6,543	)		(7,990	)
Total other income		547			520			453			353
Net loss	$	(7,479	)	$	(7,001	)	$	(6,090	)	$	(7,637	)
Net loss per share, basic and diluted	$	(0.30	)	$	(0.28	)	$	(0.24	)	$	(0.31	)
Weighted average common shares outstanding, basic and diluted		24,857,771			24,875,573			24,893,036			24,922,080


	For the Quarter Ended
	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

Subsequent Event

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Event

Note 13–Subsequent Event

On March 10, 2020 (the “Effective Date”), the Company entered into (i) a mezzanine loan and security agreement (the “Mezzanine Loan Agreement”) with Silicon Valley Bank, as administrative agent and collateral agent (the “Agent”), and Silicon Valley Bank and West River Innovation Lending Fund VIII, L.P., as lenders (the “Mezzanine Lenders”), pursuant to which the Mezzanine Lenders have agreed to lend the Company up to $50.0 million in a series of term loans, and (ii) a loan and security agreement (the “Senior Loan Agreement”, and together with the Mezzanine Loan Agreement, the “Loan Agreements”) with Silicon Valley Bank, as lender (the “Senior Lender”, and together with the Mezzanine Lenders, the “Lenders”), pursuant to which the Senior Lender has agreed to provide the Company a revolving line of credit of up to $5.0 million. Upon entering into the Loan Agreements, the Company borrowed $35.0 million in term loans from the Mezzanine Lenders (the “Term A Loan”).

Under the terms of the Mezzanine Loan Agreement, the Company may, at its sole discretion, borrow from the Mezzanine Lenders up to an additional $15.0 million in term loans (the “Term B Loan”, and together with the Term A Loan, the “Term Loans”) upon the Company’s achievement of (i) a specified amount in trailing six-month net revenue and (ii) an equity raise of at least $40.0 million (the foregoing clauses (i) and (ii), collectively, the “Term B Milestone”). The Company may draw the Term B Loan during the period commencing on the date of the occurrence of the Term B Milestone and ending on the earliest of (i) December 31, 2021 and (ii) the occurrence of an event of default.

Under the terms of the Senior Loan Agreement, the Company may, at its sole discretion, borrow from the Senior Lender one or more advances on the revolving credit line (the “Revolving Loans”, and together with the Term Loans, the “Loans”) in an aggregate amount not to exceed the lesser of (i) 85% of the aggregate amount then-contained in the Company’s eligible accounts receivable and (ii) $5.0 million.

The Company’s obligations under the Senior Loan Agreement and the Mezzanine Loan Agreement are secured by, respectively, a first priority perfected security interest and second priority perfected security interest in substantially all of the Company’s current and future assets, other than its intellectual property (except rights to payment from the sale, licensing or disposition of such intellectual property). The Company has also agreed not to encumber its intellectual property assets, except as permitted by the Loan Agreements.

All of the Loans mature on March 1, 2024 (the “Maturity Date”). The Term Loans will be interest-only through March 31, 2022, followed by 24 equal monthly payments of principal and interest; provided that if the Company draws the Term B Loan, the Term Loans will be interest-only through September 30, 2022, followed by 18 equal monthly payments of principal and interest. The Term Loans will bear interest at a floating per annum rate equal to the greater of (i) 7.25% and (ii) the sum of (a) the prime rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 2.50%. The Revolving Loans will bear interest at a floating per annum rate equal to the greater of (i) 6.00% and (ii) the sum of (a) the prime rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 1.25%.

The Company will be required to make a final payment of 7.50% of the original principal amount of the Term Loans drawn payable on the earlier of (i) the Maturity Date, (ii) the acceleration of any Term Loans, or (iii) the prepayment of the Term Loans (the “Final Payment”). The Company may prepay all, or any portion (in increments of at least $1.0 million), of the Term Loans upon 5 business days’ advance written notice to the Agent, provided that the Company will be obligated to pay a prepayment fee equal to (i) 3.00% of the principal amount of the applicable Term Loan prepaid on or before the first anniversary of the Effective Date, (ii) 2.00% of the principal amount of the applicable Term Loan prepaid between the first and second anniversary of the Effective Date, and (iii) 1.00% of the principal amount of the applicable Term Loan prepaid thereafter, and prior to the third anniversary of the Effective Date (each, a “Prepayment Fee”).

The Company may terminate the revolving credit line under the Senior Loan Agreement at any time upon 3 business days’ advance written notice to the Senior Lender. If the Company terminates the revolving credit line prior to the Maturity Date, it must pay to the Senior Lender an early termination fee of $50,000 (the “Termination Fee”).

The Company is subject to a number of affirmative and restrictive covenants pursuant to the Loan Agreements, including covenants regarding achieving minimum product revenues, delivery of financial statements, maintenance of inventory, payment of taxes, maintenance of insurance, protection of intellectual property rights, dispositions of property, business combinations or acquisitions, incurrence of additional indebtedness or liens, investments and transactions with affiliates, among other customary covenants.

Upon the occurrence of certain events, including but not limited to the Company’s failure to satisfy its payment obligations under the Loan Agreements, the breach of certain of its other covenants under the Loan Agreements, or the occurrence of a material adverse change, cross defaults to other indebtedness or material agreements, judgment defaults and defaults related to failure to maintain governmental approvals failure of which to maintain could result in a material adverse effect, the Agent and the Lenders will have the right, among other remedies, to declare all principal and interest immediately due and payable, to exercise secured party remedies, to receive the Final Payment and Termination Fee and, if the payment of principal and interest is due prior to the Maturity Date, to receive the applicable Prepayment Fee.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Segments

Cash Cash Equivalents and Marketable Securities

Cash, Cash Equivalents and Marketable Securities

Concentrations of Credit Risk and Off-Balance Sheet Risk

Property and Equipment

Description		Useful Lives
Equipment		5 years
Leasehold Improvements		Lease term
Office Furniture and Fixtures		3 years

Research and Development Costs

Fair Value Measurement

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:

Comprehensive Loss

Share Based Compensation

Stock-Based Compensation

The fair value of restricted stock awards are based on the closing price of the Company’s common stock on the grant date.

Income Taxes

Net Loss Per Share

	As of December 31,
	2019		2018
Shares issuable upon exercise of stock options		1,914,545		1,529,883
Non-vested shares under restricted stock grants		1,148,859		848,859

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements Not Yet Adopted

Investments In Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments [Abstract]

Schedule of Marketable Securities

Investments in marketable securities consisted of the following as of December 31, 2019 and 2018 (in thousands):

	December 31, 2019
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
U.S. treasury securities	$	7,397	$	3	$	—		$	7,400
Commercial paper		31,913		7		(1	)		31,919
Asset-backed securities		13,446		11		—			13,457
Total marketable securities	$	52,756	$	21	$	(1	)	$	52,776

	December 31, 2018
	Amortized		Gross Unrealized		Gross Unrealized			Fair
	Cost		Gains		Losses			Value
U.S. treasury securities	$	17,028	$	—	$	(2	)	$	17,026
Commercial paper		48,623		5		(4	)		48,624
Asset-backed securities		13,904		—		(16	)		13,888
Total marketable securities	$	79,555	$	5	$	(22	)	$	79,538

Schedule of Fair Value by Level in Accordance with ASC 820 of Marketable Securities

The following tables presents fair value by level in accordance with ASC 820 (see Note 2) of the Company’s marketable securities (in thousands):

	Fair Value Measurement as of December 31, 2019
	Level 1		Level 2		Level 3		Total
U.S. treasury securities	$	7,400	$	—	$	—	$	7,400
Commercial paper		—		31,919		—		31,919
Asset-backed securities		—		13,457		—		13,457
Total	$	7,400	$	45,376	$	—	$	52,776

	Fair Value Measurement as of December 31, 2018
	Level 1		Level 2		Level 3		Total
U.S. treasury securities	$	17,026	$	—	$	—	$	17,026
Commercial paper		—		48,624		—		48,624
Asset-backed securities		—		13,888		—		13,888
Total	$	17,026	$	62,512	$	—	$	79,538

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of Restricted Stock Awards Activities

The following table summarizes restricted stock awards related to the Amended and Restated Agreement:

			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
Granted		—		—
Nonvested at December 31, 2019		848,859	$	0.33

Schedule of Stock Based Compensation Expense

	For the Year Ended December 31,
	2019		2018
Research and development	$	609	$	359
General and administrative		2,724		1,892
Total stock-based compensation	$	3,333	$	2,251

Employee and Non-Employee Stock Options [Member]

Assumptions Used to Estimate Fair Value

	For the Year Ended December 31,
	2019	2018
Exercise price	$7.95 - $14.65	$6.52 - $16.32
Risk-free rate of interest	1.42% - 2.56%	2.58% - 3.13%
Expected term (years)	5.98	6.15
Expected stock price volatility	72.1% - 78.3%	58.3% - 83.7%
Dividend yield	—	—
Weighted average grant date fair value	$7.84	$6.95

Schedule of Stock Option Activity

The following table summarizes the Company’s employee and non-employee stock option activity under the 2013 Plan and 2018 Plan for the years ended December 31, 2019 and 2018:

						Weighted average
				Weighted average		remaining contractual		Aggregate intrinsic
	Number of shares			exercise price		life (in years)		value
Outstanding as of December 31, 2017		90,429		$	0.90
Options granted		1,451,839			8.34
Exercised		(8,385	)		0.90
Forfeited		(4,000	)		16.32
Outstanding as of December 31, 2018		1,529,883			8.03
Options granted		830,918			11.57
Exercised		(102,237	)		8.15
Forfeited		(344,019	)		10.37
Outstanding as of December 31, 2019		1,914,545		$	9.14		8.5	$	12,953,956
Options vested and exercisable as of December 31, 2019		616,994		$	7.21		7.9	$	5,362,458

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Summary of Components of Lease Expense

The components of lease expense are as follows (in thousands):

	For the Year Ended December 31,
	2019		2018
Operating lease:
Operating lease costs	$	211	$	98
Short-term lease costs		17		—
Total rent expense	$	228	$	98

Schedule of Maturities of Operating Lease

Maturities of the Company’s operating lease excluding short-term leases as of December 31, 2018:

2019	$	136
2020		139
2021		58
Total lease payments	$	333



2020	$	139
2021		58
Total lease payments		197
Less imputed interest		(9	)
Total rent expense	$	188

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

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,
	2019			2018
Tax computed at statutory federal income tax rate	$	(5,923	)	$	(4,336	)
State taxes, net of federal benefit		(2,312	)		(1,478	)
Permanent items		70			409
Other		(285	)		(5	)
Change in valuation allowance		8,450			5,410
Income tax provision (benefit)	$	—		$	—

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,
	2019			2018
Deferred tax assets:
Net operating loss carryovers	$	14,370		$	6,909
Other		1,483			510
Total deferred tax assets		15,853			7,419
Less valuation allowance		(15,835	)		(7,383	)
Deferred tax asset, net of valuation allowance		18			36
Deferred tax liabilities:
Fixed assets		(18	)		(36	)
Total deferred tax liabilities		(18	)		(36	)
Net deferred tax assets	$	—		$	—

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The following tables present the quarterly results of operations for 2019 and 2018 (in thousands, except share and per share amounts):

	For the Quarter Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Operating expenses:
Research and development	$	4,487		$	3,928		$	3,049		$	3,972
General and administrative		3,539			3,593			3,494			4,018
Total operating expenses		8,026			7,521			6,543			7,990
Loss from operations		(8,026	)		(7,521	)		(6,543	)		(7,990	)
Total other income		547			520			453			353
Net loss	$	(7,479	)	$	(7,001	)	$	(6,090	)	$	(7,637	)
Net loss per share, basic and diluted	$	(0.30	)	$	(0.28	)	$	(0.24	)	$	(0.31	)
Weighted average common shares outstanding, basic and diluted		24,857,771			24,875,573			24,893,036			24,922,080


	For the Quarter Ended
	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

Organization and Description of Business Operations - Additional Information (Detail) $ / shares in Units, $ in Thousands					12 Months Ended
	Jun. 19, 2018 USD ($) $ / shares shares	Jun. 04, 2018 shares	Mar. 07, 2018 USD ($) $ / shares shares	Feb. 20, 2018 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
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 \| $					$ (61,192)	$ (33,083)
Issuance of common stock in connection with IPO, net of offering costs \| $						$ 86,250
Common stock, authorized	200,000,000				200,000,000	200,000,000
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
Public offering price of common stock \| $ / shares	$ 15.00
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

Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) 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
Operating lease right-of-use asset	$ 304,000	111,000
Operating lease liability	306,000	$ 188,000
Deferred rent	2,000
Accumulated Deficit and Additional Paid-in Capital [Member]
Significant Accounting Policies [Line Items]
Adjustment to accumulated deficit and additional paid -in capital	$ 98,000

Stockholders' Equity - Additional Information (Detail) - USD ($)					12 Months Ended
	Nov. 27, 2019	Jun. 19, 2018	Mar. 07, 2018	Feb. 20, 2018	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity [Line Items]
Common stock, authorized		200,000,000			200,000,000	200,000,000
Common stock, par value		$ 0.0001			$ 0.0001	$ 0.0001
Common stock, voting right					one
Treasury stock, shares					105,144	105,144
Compensation expense					$ 3,333,000	$ 2,251,000
IPO [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares		16,246,872
Common stock issued and sale		5,750,000
Series B Preferred Stock [Member] \| IPO [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares		1,130,679
Series A Preferred Stock [Member] \| IPO [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares		12,428,773
Series C Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Common stock issued and sale			4,606,267	4,606,267
Issuance price			$ 4.559	$ 4.559
Gross proceeds			$ 21,000,000	$ 21,000,000		$ 21,000,000
Series C Preferred Stock [Member] \| IPO [Member]
Stockholders Equity [Line Items]
Conversion of preferred stock into common stock, shares		2,687,420
Restricted Stock Units (RSUs) [Member]
Stockholders Equity [Line Items]
Description of awards vested					The restricted stock units vest 50% upon receipt of regulatory approval of the Company’s new drug application for VP-102 for the treatment of molluscum (the “Approval Date”) and 50% shall vest on the one year anniversary of the Approval Date subject to the holders’ continuous service through each applicable date.
Vesting period	1 year
Restricted Stock Units (RSUs) [Member] \| Executive Officers [Member]
Stockholders Equity [Line Items]
Shares granted to key executives	300,000
Restricted Stock Units (RSUs) [Member] \| One Year Anniversary [Member]
Stockholders Equity [Line Items]
Vesting percentage	50.00%
Restricted Stock Units (RSUs) [Member] \| New Drug Application [Member]
Stockholders Equity [Line Items]
Vesting percentage	50.00%
Amended and Restated Agreement [Member]
Stockholders Equity [Line Items]
Treasury stock, shares					848,859
Repurchase price					$ 0.0001
Compensation expense					$ 0

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Nov. 27, 2019	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Treasury stock, shares		105,144	105,144
Amended and Restated Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Treasury stock, shares		848,859
Repurchase price		$ 0.0001
Employee and Non-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 2023
Stock options expiration term, description		Through 2029
Weighted average grant date fair value per share		$ 7.84	$ 6.95
Total unrecognized compensation		$ 8.7
Weighted-average stock option recognize period		2 years 9 months 18 days
Employee and Non-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 and Non-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
Employee Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of exercise shares vested stock options		27,329
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	1 year
Restricted Stock Units (RSUs) [Member] \| Executive Officers [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted	300,000
Restricted Stock Units (RSUs) [Member] \| New Drug Application [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock subject to vesting (as a percent)	50.00%
Restricted Stock Units (RSUs) [Member] \| Amended and Restated Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation related to nonvested restricted stock units		$ 5.0
Restricted Stock Units (RSUs) [Member] \| One Year Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock subject to vesting (as a percent)	50.00%
2018 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares reserved for issuance		3,738,199
Shares issued		2,198,198
Number of years reserved share increase		10 years
Annual Increase in number of common shares from January 1, 2019 through January 1, 2028		4.00%
Shares available for grant		2,199,325

Stock-Based Compensation - Assumptions Used to Estimate Fair Value Employee Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Dividend yield	0.00%
Employee and Non-Employee Stock Options [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Risk-free rate of interest, minimum	1.42%	2.58%
Risk-free rate of interest, maximum	2.56%	3.13%
Expected term (years)	5 years 11 months 23 days	6 years 1 month 24 days
Expected stock price volatility, minimum	72.10%	58.30%
Expected stock price volatility, maximum	78.30%	83.70%
Dividend yield	0.00%	0.00%
Weighted average grant date fair value	$ 7.84	$ 6.95
Employee and Non-Employee Stock Options [Member] \| Minimum [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	7.95	6.52
Employee and Non-Employee Stock Options [Member] \| Maximum [Member]
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Exercise price	$ 14.65	$ 16.32

Stock-Based Compensation - Schedule of Employee Stock Option Activity (Detail) - 2013 and 2018 Equity Incentive Plan [Member] - Employee and Non-Employee Stock Options [Member] - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, Outstanding Beginning Balance	1,529,883	90,429
Number of shares, Options granted	830,918	1,451,839
Number of shares, Exercised	(102,237)	(8,385)
Number of shares, Forfeited	(344,019)	(4,000)
Number of shares, Outstanding Ending Balance	1,914,545	1,529,883
Number of shares, Options vested and exercisable Ending Balance	616,994
Weighted average exercise price, Outstanding Beginning Balance	$ 8.03	$ 0.90
Weighted average exercise price, Options granted	11.57	8.34
Weighted average exercise price, Exercised	8.15	0.90
Weighted average exercise price, Forfeited	10.37	16.32
Weighted average exercise price, Outstanding Ending Balance	9.14	$ 8.03
Weighted average exercise price, Options vested and exercisable Ending Balance	$ 7.21
Weighted average remaining contractual life (in years), Outstanding	8 years 6 months
Weighted average remaining contractual life (in years), Options vested and exercisable	7 years 10 months 24 days
Aggregate intrinsic value, Outstanding Ending Balance	$ 12,953,956
Aggregate intrinsic value, Options vested and exercisable Ending Balance	$ 5,362,458

Leases - Additional Information (Detail)		12 Months Ended
Leases - Additional Information (Detail)	Jul. 01, 2019 ft²	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Lessee Lease Description [Line Items]
Operating lease expiration		2021-05
Operating lease, initial term of contract		7 years
Operating lease, base rent		$ 1,300,000
Operating lease liability		188,000	$ 306,000
Operating lease liability, current		130,000
Operating lease right-of-use asset		$ 111,000	$ 304,000
Remaining lease term		1 year 4 months 24 days
Discount rate		6.75%
Pennsylvania [Member]
Lessee Lease Description [Line Items]
Lease agreement commencement date	Jul. 01, 2019
Area of office space for lease \| ft²	5,829

Leases - Schedule of Maturities of Operating Lease (Detail) - USD ($)	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
2019			$ 136,000
2020			139,000
2021			58,000
Total lease payments			$ 333,000
2020	$ 139,000
2021	58,000
Total lease payments	197,000
Less imputed interest	(9,000)
Total rent expense	$ 188,000	$ 306,000

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryovers	$ 14,370	$ 6,909
Other	1,483	510
Total deferred tax assets	15,853	7,419
Less valuation allowance	(15,835)	(7,383)
Deferred tax asset, net of valuation allowance	18	36
Deferred tax liabilities:
Fixed assets	(18)	(36)
Total deferred tax liabilities	$ (18)	$ (36)

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 3,972	$ 3,049	$ 3,928	$ 4,487	$ 4,917	$ 3,467	$ 3,515	$ 927	$ 15,436	$ 12,826
General and administrative	4,018	3,494	3,593	3,539	3,271	2,865	1,955	961	14,644	9,052
Total operating expenses	7,990	6,543	7,521	8,026	8,188	6,332	5,470	1,888	30,080	21,878
Loss from operations	(7,990)	(6,543)	(7,521)	(8,026)	(8,188)	(6,332)	(5,470)	(1,888)	(30,080)	(21,878)
Total other income	353	453	520	547	610	426	153	41	1,873	1,230
Net loss	$ (7,637)	$ (6,090)	$ (7,001)	$ (7,479)	$ (7,578)	$ (5,906)	$ (5,317)	$ (1,847)	$ (28,207)	$ (20,648)
Net loss per share, basic and diluted	$ (0.31)	$ (0.24)	$ (0.28)	$ (0.30)	$ (0.30)	$ (0.24)	$ (0.92)	$ (0.65)	$ (1.13)	$ (1.41)
Weighted average common shares outstanding, basic and diluted	24,922,080	24,893,036	24,875,573	24,857,771	24,847,877	24,847,512	5,751,326	2,850,460	24,897,889	14,662,751

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Subsequent Event - Additional Information (Details) - USD ($)		12 Months Ended
	Mar. 10, 2020	Dec. 31, 2019
Senior Loan Agreement [Member]
Subsequent Event [Line Items]
Term loans, payment terms		The Term Loans will be interest-only through March 31, 2022, followed by 24 equal monthly payments of principal and interest; provided that if the Company draws the Term B Loan, the Term Loans will be interest-only through September 30, 2022, followed by 18 equal monthly payments of principal and interest.
Loans, interest rate terms		The Term Loans will bear interest at a floating per annum rate equal to the greater of (i) 7.25% and (ii) the sum of (a) the prime rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 2.50%.
Senior Loan Agreement [Member] \| Revolving Loans [Member]
Subsequent Event [Line Items]
Loans, interest rate terms		The Revolving Loans will bear interest at a floating per annum rate equal to the greater of (i) 6.00% and (ii) the sum of (a) the prime rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 1.25%.
Subsequent Event [Member]
Subsequent Event [Line Items]
Term loans, frequency of periodic payments	24 equal monthly
Subsequent Event [Member] \| Mezzanine Loan Agreement [Member] \| Term B Loan [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 15,000,000
Subsequent Event [Member] \| Mezzanine Loan Agreement [Member] \| Term B Loan [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Proceeds from equity financing	40,000,000
Subsequent Event [Member] \| Mezzanine Loan Agreement [Member] \| Mezzanine Lenders [Member] \| Term Loans [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	50,000,000
Subsequent Event [Member] \| Mezzanine Loan Agreement [Member] \| Mezzanine Lenders [Member] \| Term A Loan [Member]
Subsequent Event [Line Items]
Borrowed amount	35,000,000
Subsequent Event [Member] \| Mezzanine Loan Agreement [Member] \| Silicon Valley Bank (Senior Lender) [Member] \| Revolving Loans [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	5,000,000
Subsequent Event [Member] \| Senior Loan Agreement [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 5,000,000
Line of credit, maximum borrowing base percentage of eligible accounts receivable	85.00%
Loans, maturity date	Mar. 01, 2024
Loans, interest rate	7.25%
Term loans, final payment percentage of original principal amount	7.50%
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Term Loan Prepaid on or Before First Anniversary of Effective Date [Member]
Subsequent Event [Line Items]
Debt instrument, prepayment fee percentage	3.00%
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Term Loan Prepaid Between First and Second Anniversary of Effective Date [Member]
Subsequent Event [Line Items]
Debt instrument, prepayment fee percentage	2.00%
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Term Loan Prepaid Thereafter, and Prior to Third Anniversary of Effective Date [Member]
Subsequent Event [Line Items]
Debt instrument, prepayment fee percentage	1.00%
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Prime Rate [Member]
Subsequent Event [Line Items]
Loans, variable rate	2.50%
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Term A and B Loan [Member]
Subsequent Event [Line Items]
Term loans, frequency of periodic payments	18 equal monthly
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Repayments of term loans increments amount	$ 1,000,000
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Revolving Loans [Member]
Subsequent Event [Line Items]
Loans, interest rate	6.00%
Credit line, early termination fee amount	$ 50,000
Subsequent Event [Member] \| Senior Loan Agreement [Member] \| Revolving Loans [Member] \| Prime Rate [Member]
Subsequent Event [Line Items]
Loans, variable rate	1.25%

Significant Accounting Policies - Schedule of Depreciable Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2019
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

Property and Equipment - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,174	$ 275
Accumulated depreciation	(84)	(20)
Total property and equipment, net	2,090	255
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	68	68
Office Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	48	48
Office Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	31	28
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,027	$ 131

Related Party Transactions - Additional Information (Detail) - PBM Capital Group, LLC [Member] - USD ($)				1 Months Ended	12 Months Ended
	Oct. 01, 2019	Jan. 01, 2019	Dec. 02, 2015	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Services agreement initial term			12 months
Expenses incurred under services agreement					$ 252,000	$ 457,500
Due to related party					$ 0	$ 38,000
Service Agreement [Member]
Related Party Transaction [Line Items]
Monthly management fee payable			$ 2,500
Amended Service Agreement [Member]
Related Party Transaction [Line Items]
Monthly management fee payable	$ 5,000	$ 26,333		$ 50,000

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Compensation and related costs	$ 1,195	$ 1,261
Clinical trials and drug development	733
Consulting - former Chief Scientific Officer		190
Professional fees	89	56
Other	19	10
Total accrued expenses	$ 2,036	$ 1,517

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) claim $ / h	Dec. 31, 2018 USD ($) claim	Jan. 31, 2020 USD ($)	Mar. 22, 2018 USD ($)
Loss Contingencies [Line Items]
Number of litigation against the company \| claim	0	0
Accrued expenses	$ 2,036,000	$ 1,517,000
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	$ 0	$ 200,000
Crude Cantharidin Material [Member]
Loss Contingencies [Line Items]
Purchase agreement term	5 years
Purchase Commitment	$ 1,800,000			$ 2,300,000
Purchase commitment remaining obligation	0
Purchase commitment prepayment	$ 1,100,000
Crude Cantharidin Material [Member] \| Subsequent Event [Member]
Loss Contingencies [Line Items]
Purchase commitment remaining obligation			$ 700,000

Investments in Marketable Securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Amortized Cost	$ 52,756	$ 79,555
Gross Unrealized Gains	21	5
Gross Unrealized Losses	(1)	(22)
Fair Value	52,776	79,538
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	7,397	17,028
Gross Unrealized Gains	3
Gross Unrealized Losses		(2)
Fair Value	7,400	17,026
Commercial Paper [Member]
Marketable Securities [Line Items]
Amortized Cost	31,913	48,623
Gross Unrealized Gains	7	5
Gross Unrealized Losses	(1)	(4)
Fair Value	31,919	48,624
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	13,446	13,904
Gross Unrealized Gains	11
Gross Unrealized Losses		(16)
Fair Value	$ 13,457	$ 13,888

Investments in Marketable Securities - Schedule of Fair Value by Level in Accordance with ASC 820 of Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Marketable securities	$ 52,776	$ 79,538
Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	7,400	17,026
Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	45,376	62,512
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Marketable securities	7,400	17,026
U.S. Treasury Securities [Member] \| Level 1 [Member]
Marketable Securities [Line Items]
Marketable securities	7,400	17,026
Commercial Paper [Member]
Marketable Securities [Line Items]
Marketable securities	31,919	48,624
Commercial Paper [Member] \| Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	31,919	48,624
Asset Backed Securities [Member]
Marketable Securities [Line Items]
Marketable securities	13,457	13,888
Asset Backed Securities [Member] \| Level 2 [Member]
Marketable Securities [Line Items]
Marketable securities	$ 13,457	$ 13,888

Property and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 64,200	$ 20,300

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,333	$ 2,251
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	609	359
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 2,724	$ 1,892

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Equity ownership period	3 years
Unrecognized tax benefits	$ 1,500,000	$ 100,000
Unrecognized tax benefits, income tax penalties and interest accrued	0	0
Unrecognized tax benefits, income tax penalties and interest expense	$ 0	$ 0
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Ownership percentage	50.00%
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 49,900,000		$ 6,900,000
State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 50,200,000
Net Operating Loss Carryforwards Generated in 2016 and 2017 [Member]
Operating Loss Carryforwards [Line Items]
Federal and state net operating loss carryforwards, expiration date	2033