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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	KRYS
Entity Registrant Name	Krystal Biotech, Inc.
Entity Central Index Key	0001711279
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		17,385,809
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-38210
Entity Tax Identification Number	82-1080209
Entity Address, Address Line One	2100 Wharton Street
Entity Address, Address Line Two	Suite 701
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15203
City Area Code	412
Local Phone Number	586-5830
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 180,225	$ 187,514
Short-term investments	6,479	6,171
Prepaid expenses and other current assets	1,625	2,195
Total current assets	188,329	195,880
Property and equipment, net	10,264	8,475
Long-term investments		497
Prepaid rent	2,400
Right-of-use asset	2,633	2,709
Other non-current assets	1,505	1,462
Total assets	205,131	209,023
Current liabilities
Accounts payable	636	724
Current portion of lease liability	509	480
Accrued expenses and other current liabilities	2,916	2,123
Total current liabilities	4,061	3,327
Lease liability	2,701	2,782
Total liabilities	6,762	6,109
Commitments and contingencies (Note 6)
Stockholders' equity
Preferred stock; $0.00001 par value; 20,000,000 shares authorized at March 31, 2020 (unaudited) and December 31, 2019; 2,061,773 shares issued, and no shares outstanding at March 31, 2020 (unaudited) and December 31, 2019	0	0
Common stock; $0.00001 par value; 80,000,000 shares authorized at March 31, 2020 (unaudited) and December 31, 2019; 17,370,564 and 17,354,310 shares issued and outstanding at March 31, 2020 (unaudited) and December 31, 2019, respectively	0	0
Additional paid-in capital	242,733	241,951
Accumulated other comprehensive income	24	10
Accumulated deficit	(44,388)	(39,047)
Total stockholders' equity	198,369	202,914
Total liabilities and stockholders' equity	$ 205,131	$ 209,023

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Expenses
Research and development	$ 3,525	$ 3,167
General and administrative	2,421	1,527
Total operating expenses	5,946	4,694
Loss from operations	(5,946)	(4,694)
Other Income
Interest and other income, net	605	583
Net loss	(5,341)	(4,111)
Unrealized gain on available-for-sale securities	14	14
Comprehensive loss	$ (5,327)	$ (4,097)
Net loss per common share: Basic and diluted	$ (0.31)	$ (0.29)
Weighted-average common shares outstanding: Basic and diluted	17,359,356	14,417,649

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2018	$ 113,226		$ 133,183	$ 2	$ (19,959)
Beginning Balance, shares at Dec. 31, 2018		14,428,916
Issuance of common stock, net	44		44
Issuance of common stock, net, shares		14,653
Stock-based compensation expense	313		313
Unrealized gain on investments	14			14
Net loss	(4,111)				(4,111)
Ending balance at Mar. 31, 2019	109,486		133,540	16	(24,070)
Ending Balance, shares at Mar. 31, 2019		14,443,569
Beginning balance at Dec. 31, 2019	202,914		241,951	10	(39,047)
Beginning Balance, shares at Dec. 31, 2019		17,354,310
Issuance of common stock, net	243		243
Issuance of common stock, net, shares		16,254
Stock-based compensation expense	539		539
Unrealized gain on investments	14			14
Net loss	(5,341)				(5,341)
Ending balance at Mar. 31, 2020	$ 198,369		$ 242,733	$ 24	$ (44,388)
Ending Balance, shares at Mar. 31, 2020		17,370,564

- Definition

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

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities
Net loss	$ (5,341)	$ (4,111)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	335	132
Stock-based compensation expense	539	313
(Increase) decrease in
Prepaid expenses and other current assets	108	(352)
Prepaid rent	(2,400)
Amortization of right-of-use asset, net	26	67
Accounts payable	244	583
Accrued expenses and other current liabilities	262	153
Net cash used in operating activities	(6,227)	(3,215)
Investing Activities
Purchases of property and equipment	(1,508)	(1,707)
Purchases of short-term investments	(1,967)	(512)
Proceeds from maturities of short-term investments	2,170
Purchase of other noncurrent assets		(263)
Net cash used in investing activities	(1,305)	(2,482)
Financing Activities
Issuance of common stock, net	243	40
Net cash provided by financing activities	243	40
Net decrease in cash and cash equivalents	(7,289)	(5,657)
Cash and cash equivalents at beginning of period	187,514	103,670
Cash and cash equivalents at end of period	180,225	98,013
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Unpaid purchases of property and equipment	1,302	375
Unpaid offering costs	$ 22	155
Initial recognition of right-of-use assets		$ 3,394

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of 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 or GAAP as found in the Accounting Standards Codification, or ASC, the Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB, and the rules and regulations of the US Securities and Exchange Commission, or SEC. All intercompany balances and transactions have been eliminated in consolidation.

Risks and Uncertainties

The pandemic caused by an outbreak of a new strain of coronavirus, or COVID-19, has resulted, and is likely to continue to result, in significant national and global economic disruption and may adversely affect our business. The Company is actively monitoring the impact of COVID-19 and the possible effects on its financial condition, liquidity, operations, suppliers, industry, and workforce. However, the full extent, consequences, and duration of the COVID-19 pandemic and the resulting impact on the Company cannot currently be predicted. The Company will continue to evaluate the impact that these events could have on the operations, financial position, and the results of operations and cash flows during fiscal year 2020.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the condensed consolidated financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements. Estimates are used in the following areas including stock-based compensation expense, accrued research and development expenses, the fair value of financial instruments, incremental borrowing rate for lease liability, and the valuation allowance included in deferred income tax calculation.

Segment and Geographical Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company and the Company’s chief operating decision maker view the Company’s operations and manage its business in one operating segment, which is the business of developing and commercializing pharmaceuticals.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject the Company to credit risk consist of cash, cash equivalents and investments. The Company’s policy is to invest its cash, cash equivalents and investments in money market funds, certificates of deposit and various other bank deposit accounts. The counterparties to the agreements relating to the Company’s investments consist of financial institutions of high credit standing. The Company is exposed to credit risk in the event of default by the financial institutions to the extent amounts recorded on the balance sheets are in excess of insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no financial instruments with off-balance sheet risk of loss.

Cash, Cash Equivalents and Investments

Cash and cash equivalents consist of money market funds and bank deposits. Cash equivalents are defined as short-term, highly liquid investments with original maturities of 90 days or less at the date of purchase.

Investments with maturities of greater than 90 days but less than one year are classified as short-term investments on the consolidated balance sheets and consist of US Treasury bills and certificates of deposit. Investments with maturities of greater than one year are classified as long-term investments on the consolidated balance sheets and consist of certificates of deposit. Accrued interest on US Treasury bills and certificates of deposit are also classified as short-term investments.

As our entire investment portfolio is considered available for use in current operations, we classify all investments as available-for-sale securities. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive loss, which is a separate component of stockholders’ equity in the consolidated balance sheets.

Fair Value of Financial Instruments

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. There is a three-level hierarchy that prioritizes the inputs used in determining fair value by their reliability and preferred use, as follows:

•

Level 1— Valuations based on quoted prices in active markets for identical assets or liabilities.

•

Level 2— Valuations based on quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3— Valuations based on inputs that are both significant to the fair value measurement and unobservable.

To the extent that a valuation is based on models or inputs that are less observable, or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized within Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

There have been no significant changes to the valuation methods utilized by the Company during the periods presented. There have been no transfers between Level 1, Level 2, and Level 3 in any periods presented.

The carrying amounts of financial instruments consisting of cash and cash equivalents, investments, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities included in the Company’s financial statements, are reasonable estimates of fair value, primarily due to their short maturities. Marketable securities are classified as long-term investments if the Company has the ability and intent to hold them and such holding period is longer than one year. The Company classifies all its investments as available-for-sale.

Our available-for-sale short-term investments, which consist of US Treasury bills and certificates of deposit, are considered to be level 2 valuations. The fair value of Level 2 financial assets is determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis.

Property and Equipment, net

Property and equipment, net, is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred, while costs of major additions and betterments are capitalized. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective assets, which are as follows:

Computer equipment and software

3 years

Lab equipment

Furniture and fixtures

Leasehold improvements

3-7 years

3 years

shorter of 8 years and remaining life of lease

Construction-in-progress is not depreciated until the asset is placed in service.

Impairment of Long-Lived Assets

The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. The Company has not recognized any impairment losses for the three months ended March 31, 2020 and 2019.

Leases

We have entered into two lease agreements for our laboratory, manufacturing and office space. On January 1, 2019, we adopted ASC 842 – Leases. Pursuant to ASC 842, all of our leases outstanding on January 1, 2019 continued to be classified as operating leases. With the adoption of ASC 842, we recorded an operating lease right-of-use asset of $1.1 million and an operating lease liability of $1.4 million on the condensed consolidated balance sheet. Right-of-use lease assets represent our right to use the underlying asset during the lease term and the lease obligation represents our commitment to make lease payments arising from the lease. Right-of-use lease assets and obligations were recognized based on the present value of remaining lease payments over the lease term. As the Company’s leases do not provide an implicit rate, we have used an estimated incremental borrowing rate based on the information available at our adoption date in determining the present value of lease payments. Operating lease expense is recognized on a straight-line basis over the lease term. The Company adopted the New Lease Standard as of the effective date of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. Comparative periods in the Company's financial statements will be presented in accordance with the previous guidance under ASC Topic 840, Leases. Upon adoption, the Company took advantage of the transition package of practical expedients permitted within ASC 842, which allowed the Company not to reassess previous accounting conclusions around whether arrangements are, or contain, leases, as well as to carry forward both the historical classification of leases and the treatment of initial direct costs for existing leases. In addition, the Company also has made an accounting policy election to exclude leases with an initial term of twelve months or less from its balance sheet.

Research and Development Expenses

Research and development costs are charged to expense as incurred in performing research and development activities. The costs include employee compensation costs, facilities and overhead, preclinical and clinical activities, related clinical manufacturing costs, regulatory and other related costs.

The Company estimates contract research and clinical trials materials manufacturing expenses based on the services performed pursuant to contracts with research and manufacturing organizations that manufacture materials used in the Company’s ongoing preclinical and clinical studies. Nonrefundable advanced payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed.

In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses using information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly.

Stock-Based Compensation Expense

The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation-Stock Compensation, or ASC 718. ASC 718 requires all stock-based payments, including grants of stock options and restricted stock, to be recognized in the statements of operations based on their grant-date fair values. Compensation expense is recognized on a straight-line basis based on the grant-date fair value over the associated service period of the award, which is generally the vesting term.

The Company estimates the fair value of its stock options using the Black-Scholes option pricing model, which requires the input of subjective assumptions, including: (i) the expected stock price volatility; (ii) the expected term of the award; (iii) the risk-free interest rate; and (iv) expected dividends. Due to the lack of sufficient history and trading volume of our Common Stock and a lack of Company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected term of the stock-based awards. The Company computes historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Due to the lack of Company-specific historical option activity, the Company has estimated the expected term of its employee stock options using the “simplified” method, whereby the expected term equals the arithmetic mean of the vesting term and the original contractual term of the option. The risk-free interest rates are based on the US Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid and does not expect to pay dividends in the foreseeable future. The Company is also required to estimate forfeitures at the time of grant and to revise those estimates in subsequent periods if actual forfeitures differ from its estimates. To the extent that actual forfeitures differ from the Company’s estimates, the differences are recorded as a cumulative adjustment in the period the estimates were revised.

Comprehensive Loss

Comprehensive loss is defined as the change in equity during a period from transactions from non-owner sources. Unrealized gains (losses) on available-for-sale securities is a component of other comprehensive gains (losses) and is presented net of taxes. We have not recorded any reclassifications from other comprehensive gains (losses) to net loss during any period presented.

Recent Accounting Pronouncements

In August 2018, the FASB issued ASU 2018-13 - Fair Value Measurement (Topic 820), or ASU 2018-13, which removes, modifies and adds disclosure requirements on fair value measurements. ASU 2018-13 removes disclosure requirements for transfers between Level 1 and Level 2 measurements and valuation processes for Level 3 measurements but adds new disclosure requirements including changes in unrealized gains/losses in other comprehensive income related to recurring Level 3 measurements. The amended guidance was effective for us commencing in the first quarter of 2020. Certain aspects may be applied prospectively while other aspects may be applied retrospectively upon the effective date. The adoption of the guidance resulted in us disclosing the Company’s cash, cash equivalents and available-for-sale securities by significant investment category as of March 31, 2020 and 2019.

Fair Value Instruments

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Instruments

4. Fair Value Instruments

The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category as of March 31, 2020 and December 31, 2019, respectively (in thousands):

	March 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate Fair Value		Cash and Cash Equivalents		Short-term Marketable Securities ⁽¹⁾		Long-term Marketable Securities ⁽²⁾
Level 1:
Cash	$	2	$	—	$	—	$	2	$	2	$	—	$	—
Money market instruments		180,223		—		—		180,223		180,223		—		—
Subtotal		180,225		—		—		180,225		180,225		—		—

Level 2:
U.S. government agency securities		1,501		12		—		1,513		—		1,513		—
Certificates of deposit		4,954		12		—		4,966		—		4,966		—
Subtotal		6,455		24		—		6,479		—		6,479		—

Total	$	186,680	$	24	$	—	$	186,704	$	180,225	$	6,479	$	—

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate Fair Value		Cash and Cash Equivalents		Short-term Marketable Securities ⁽¹⁾		Long-term Marketable Securities ⁽²⁾
Level 1:
Cash	$	3	$	—	$	—	$	3	$	3	$	—	$	—
Money market instruments		187,511		—		—		187,511		187,511		—		—
Subtotal		187,514		—		—		187,514		187,514		—		—

Level 2:
U.S. government agency securities		1,747		6		—		1,753		—		1,753		—
Certificates of deposit		4,911		4		—		4,915		—		4,418		497
Subtotal		6,658		10		—		6,668		—		6,171		497

Total	$	194,172	$	10	$	—	$	194,182	$	187,514	$	6,171	$	497

(1)

The Company’s short-term marketable securities mature in one year or less.

(2)

The Company’s long-term marketable securities mature between one and two years.

See Note 2 to these condensed consolidated financial statements for additional discussion regarding the Company’s fair value measurements.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Balance Sheet Components

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

5.	Balance Sheet Components

Property and Equipment, Net

Property and equipment, net consist of the following (in thousands):

	March 31, 2020			December 31, 2019
	(Unaudited)
Construction-in-progress	$	2,299		$	2,431
Leasehold improvements		4,681			3,179
Furniture & fixtures		440			99
Computer equipment and software		67			45
Laboratory equipment		3,958			3,571
Total property and equipment		11,445			9,325
Accumulated depreciation and amortization		(1,181	)		(850	)
Property and equipment, net	$	10,264		$	8,475

Depreciation expense was $335 thousand and $132 thousand for the three months ended March 31, 2020 and 2019, respectively.

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
	(Unaudited)
Accrued preclinical and clinical expenses	$	745	$	991
Accrued professional fees		76		72
Accrued payroll and benefits		812		510
Accrued taxes		50		40
Accrued construction in progress and laboratory equipment		1,020		491
Other current liabilities		213		19
Total	$	2,916	$	2,123

Commitments and Contingencies

3 Months Ended

Mar. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6.	Commitments and Contingencies

Significant Contracts and Agreements

Lease Agreements

In May 2016, the Company signed an operating lease for laboratory and office space that commenced in June 2016 and expired on October 31, 2017 (the “2016 Lease”). The 2016 Lease was amended to increase the area leased to approximately 31,000 square feet and to extend the expiration date to February 28, 2027, including 6,000 square feet relating to a month-to-month lease that we utilized through February 2020.

On December 26, 2019, we entered into a lease agreement for our second commercial gene therapy facility (i.e. ASTRA facility) in the Pittsburgh, Pennsylvania area. The 100,000 square foot facility is under construction and is expected to be completed by 1H 2021. The lease will commence when the space is available for access, which is anticipated to be in the second half of 2020, and has an initial term that expires on October 31, 2035. A cash contribution in the amount of $2.4 million was paid to escrow on January 21, 2020. The contribution was intended to reduce the amount of the building construction costs and had the effect of reducing the base rental rate of the lease and as such, is recorded as prepaid rent in the condensed consolidated balance sheet as of March 31, 2020.

As of March 31, 2020, future minimum commitments under the Company’s operating leases were as follows (in thousands):

	Operating Leases
2020 (remaining nine months)	$	513
2021		1,358
2022		1,385
2023		1,413
2024		1,441
Thereafter		11,316
Future minimum operating lease payments	$	17,426
Less: Operating lease payments for ASTRA	$	13,195
Less: Interest		1,021
Present value of lease liability	$	3,210
Current portion of lease liability	$	509
Long-term portion of lease liability	$	2,701

The Company recorded $178 thousand and $125 thousand in rent expense for the three months ended March 31, 2020 and 2019, respectively.

Clinical Supply Agreements

The Company has entered into various product manufacturing and clinical supply agreements with Contract Manufacturing Organizations, or CMOs. The product manufacturing and clinical supply agreements provide the terms and conditions under which the CMOs will formulate, fill, inspect, package, label and test our drug product candidates, B-VEC and KB105 for clinical supply. The Company is obligated to make milestone payments. Additionally, certain raw materials, supplies, outsourced testing and other services for the purposes of batch production will be invoiced separately by the CMOs. The estimated remaining commitment as of March 31, 2020 under these agreements for the manufacturing of our drug product is approximately $3.0 million. The Company is also responsible for the payment of a monthly service fee for project management services for the duration of any agreements. The Company has incurred expenses under these agreements of $634 thousand and $803 thousand for the three months ended March 31, 2020 and 2019, respectively.

Other Contractual Obligations

During the quarter, the Company contracted with various third parties to facilitate, coordinate and perform agreed upon market research activities relating to our lead product candidate, B-VEC. These contracts typically call for the payment of fees for services upon the achievement of certain milestones. Business activities being performed under these contracts primarily include market research and other related activities. The estimated remaining commitment as of March 31, 2020 is $530 thousand.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

8.	Stock-Based Compensation

Options granted to employees vest ratably over a four-year period and options granted to directors of the company vest ratably over one and four-year periods. Options have a life of ten years.

The Company granted 229,000 and 67,500 stock options to employees and directors of the Company during the three months ended March 31, 2020 and 2019, respectively.

The following table summarizes the Company’s stock option activity:

	Stock Options Outstanding			Weighted- average Exercise Price		Weighted- average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (In thousands) ⁽¹⁾
Outstanding at December 31, 2019		420,766		$	17.71		8.4	$	15,859
Granted		229,000		$	52.28
Exercised		(17,129	)	$	14.22			$	3,348
Cancelled or forfeited		(84,444	)	$	21.28
Outstanding at March 31, 2020		548,193		$	31.71		8.8	$	8,684
Exercisable at March 31, 2020		120,678		$	8.79		7.5	$	4,158

(1)	Aggregate intrinsic value represents the difference between the closing stock price of our common stock on March 31, 2020 and the exercise price of outstanding in-the-money options.

The weighted-average grant-date fair value per share of options granted to employees during the three months ended March 31, 2020 was $34.37.

There was $9.9 million of unrecognized stock-based compensation expense related to employees’ awards that is expected to be recognized over a weighted-average period of 3.4 years as of March 31, 2020.

The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards and restricted stock awards in the condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019 as follows (in thousands):

	Three Months Ended March 31,
	2020		2019

Research and development	$	189	$	117
General and administrative		350		196
Total stock-based compensation	$	539	$	313

Stock Options Granted. The Company recorded stock-based compensation expense of $539 thousand and $204 thousand for the three months ended March 31, 2020 and 2019, respectively. The fair value of options granted to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions for the three months ended March 31, 2020 and 2019:

	Three Months Ended March 31,
	2020			2019
Expected stock price volatility		74	%		71	%
Expected term of the award (years)		6.23			6.25
Risk-free interest rate		1.29	%		2.46	%
Weighted average exercise price	$	52.28		$	23.87
Forfeiture rate		6.42	%		10.00	%

Restricted Stock Awards. The Company granted 26,213 and 16,213 restricted stock awards, or RSAs, on June 1, 2018 to our Chief Executive Officer and Chief Operating Officer, respectively. The RSAs vested ratably over a one-year period and had completely vested as of May 31, 2019. No RSAs were outstanding as of March 31, 2020. The fair value of each restricted stock was $10.30 reflecting the closing price of our common stock on the grant date. The Company recorded stock-based compensation expense related to RSAs of zero and $109 thousand for the three months ended March 31, 2020 and 2019, respectively, within general and administrative expenses in the accompanying condensed consolidated statements of operations.

Shares remaining available for grant under the Company’s stock incentive plan were 2,070,912, with a sublimit for incentive stock options of 668,705, at March 31, 2020.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation

Risks and Uncertainties

Use of Estimates

Segment and Geographical Information

Concentrations of Credit Risk and Off-Balance Sheet Risk

Cash, Cash Equivalents and Investments

Fair Value of Financial Instruments

•

Level 1— Valuations based on quoted prices in active markets for identical assets or liabilities.

•

Level 3— Valuations based on inputs that are both significant to the fair value measurement and unobservable.

Property and Equipment, net

Computer equipment and software

3 years

Lab equipment

Furniture and fixtures

Leasehold improvements

3-7 years

3 years

shorter of 8 years and remaining life of lease

Construction-in-progress is not depreciated until the asset is placed in service.

Impairment of Long-Lived Assets

Leases

Research and Development Expenses

Stock-Based Compensation Expense

Comprehensive Loss

Recent Accounting Pronouncements

Fair Value Instruments (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Cash, Cash Equivalents and Available-for-Sale Securities

	March 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate Fair Value		Cash and Cash Equivalents		Short-term Marketable Securities ⁽¹⁾		Long-term Marketable Securities ⁽²⁾
Level 1:
Cash	$	2	$	—	$	—	$	2	$	2	$	—	$	—
Money market instruments		180,223		—		—		180,223		180,223		—		—
Subtotal		180,225		—		—		180,225		180,225		—		—

Level 2:
U.S. government agency securities		1,501		12		—		1,513		—		1,513		—
Certificates of deposit		4,954		12		—		4,966		—		4,966		—
Subtotal		6,455		24		—		6,479		—		6,479		—

Total	$	186,680	$	24	$	—	$	186,704	$	180,225	$	6,479	$	—

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate Fair Value		Cash and Cash Equivalents		Short-term Marketable Securities ⁽¹⁾		Long-term Marketable Securities ⁽²⁾
Level 1:
Cash	$	3	$	—	$	—	$	3	$	3	$	—	$	—
Money market instruments		187,511		—		—		187,511		187,511		—		—
Subtotal		187,514		—		—		187,514		187,514		—		—

Level 2:
U.S. government agency securities		1,747		6		—		1,753		—		1,753		—
Certificates of deposit		4,911		4		—		4,915		—		4,418		497
Subtotal		6,658		10		—		6,668		—		6,171		497

Total	$	194,172	$	10	$	—	$	194,182	$	187,514	$	6,171	$	497

(1)

The Company’s short-term marketable securities mature in one year or less.

(2)

The Company’s long-term marketable securities mature between one and two years.

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consist of the following (in thousands):

	March 31, 2020			December 31, 2019
	(Unaudited)
Construction-in-progress	$	2,299		$	2,431
Leasehold improvements		4,681			3,179
Furniture & fixtures		440			99
Computer equipment and software		67			45
Laboratory equipment		3,958			3,571
Total property and equipment		11,445			9,325
Accumulated depreciation and amortization		(1,181	)		(850	)
Property and equipment, net	$	10,264		$	8,475

Schedule of Accrued Expenses And Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
	(Unaudited)
Accrued preclinical and clinical expenses	$	745	$	991
Accrued professional fees		76		72
Accrued payroll and benefits		812		510
Accrued taxes		50		40
Accrued construction in progress and laboratory equipment		1,020		491
Other current liabilities		213		19
Total	$	2,916	$	2,123

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Schedule of Company's Stock Option Activity

The following table summarizes the Company’s stock option activity:

	Stock Options Outstanding			Weighted- average Exercise Price		Weighted- average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (In thousands) ⁽¹⁾
Outstanding at December 31, 2019		420,766		$	17.71		8.4	$	15,859
Granted		229,000		$	52.28
Exercised		(17,129	)	$	14.22			$	3,348
Cancelled or forfeited		(84,444	)	$	21.28
Outstanding at March 31, 2020		548,193		$	31.71		8.8	$	8,684
Exercisable at March 31, 2020		120,678		$	8.79		7.5	$	4,158

(1)	Aggregate intrinsic value represents the difference between the closing stock price of our common stock on March 31, 2020 and the exercise price of outstanding in-the-money options.

Summary of Stock Based Compensation Expense Related to Issuance of Stock Option Awards and Restricted Stock Awards

	Three Months Ended March 31,
	2020		2019

Research and development	$	189	$	117
General and administrative		350		196
Total stock-based compensation	$	539	$	313

Employee Stock Option [Member]

Fair Value of Stock Options, Valuation Assumptions

The fair value of options granted to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions for the three months ended March 31, 2020 and 2019:

	Three Months Ended March 31,
	2020			2019
Expected stock price volatility		74	%		71	%
Expected term of the award (years)		6.23			6.25
Risk-free interest rate		1.29	%		2.46	%
Weighted average exercise price	$	52.28		$	23.87
Forfeiture rate		6.42	%		10.00	%

Fair Value Instruments - Summary of Cash, Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 180,225	$ 187,514	$ 98,013	$ 103,670
Gross Unrealized Gains	24	10
Amortized Cost, Total	186,680	194,172
Aggregate Fair Value, Total	186,704	194,182
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	180,225	187,514
Cash and cash equivalents, Aggregate Fair Value	180,225	187,514
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	6,455	6,658
Gross Unrealized Gains	24	10
Aggregate Fair Value	6,479	6,668
Cash [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	2	3
Cash and cash equivalents, Aggregate Fair Value	2	3
Money Market Instruments [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	180,223	187,511
Cash and cash equivalents, Aggregate Fair Value	180,223	187,511
U.S. Government Agency Securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	1,501	1,747
Gross Unrealized Gains	12	6
Aggregate Fair Value	1,513	1,753
Certificates of Deposit [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	4,954	4,911
Gross Unrealized Gains	12	4
Aggregate Fair Value	4,966	4,915
Cash and Cash Equivalents [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value, Total	180,225	187,514
Cash and Cash Equivalents [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	180,225	187,514
Cash and Cash Equivalents [Member] \| Cash [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	2	3
Cash and Cash Equivalents [Member] \| Money Market Instruments [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	180,223	187,511
Short-term Marketable Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value, Total	6,479	6,171
Short-term Marketable Securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value	6,479	6,171
Short-term Marketable Securities [Member] \| U.S. Government Agency Securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value	1,513	1,753
Short-term Marketable Securities [Member] \| Certificates of Deposit [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value	$ 4,966	4,418
Long-term Marketable Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value, Total		497
Long-term Marketable Securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value		497
Long-term Marketable Securities [Member] \| Certificates of Deposit [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Fair Value		$ 497

Commitments and Contingencies - Schedule of Future Minimum Operating Lease Payments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Operating Leased Assets [Line Items]
2020 (remaining nine months)	$ 513
2021	1,358
2022	1,385
2023	1,413
2024	1,441
Thereafter	11,316
Future minimum operating lease payments	17,426
Less: Interest	1,021
Present value of lease liability	3,210		$ 1,400
Current portion of lease liability	509	$ 480
Long-term portion of lease liability	2,701	$ 2,782
ASTRA [Member]
Operating Leased Assets [Line Items]
Future minimum operating lease payments	$ 13,195

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option expiration period	10 years
Stock options granted	229,000	67,500
Stock-based compensation expense	$ 539	$ 313
Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for grant	2,070,912
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	4 years
Weighted-average grant-date fair value per share of options granted	$ 34.37
Unrecognized stock-based compensation expense	$ 9,900
Estimated weighted average period	3 years 4 months 24 days
Stock-based compensation expense	$ 539	204
Non-Employee Stock Option [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	1 year
Non-Employee Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	4 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	1 year
Weighted-average grant-date fair value per share of options granted	$ 10.30
Stock-based compensation expense	$ 0	$ 109
Restricted stock award outstanding	0
Restricted Stock [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock award granted	26,213	26,213
Restricted Stock [Member] \| Chief Operating Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock award granted	16,213	16,213
Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for grant	668,705

Stock-Based Compensation - Schedule of Company's Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options Outstanding, Beginning balance	420,766
Stock Options Outstanding, Granted	229,000	67,500
Stock Options Outstanding, Exercised	(17,129)
Stock Options Outstanding, Cancelled or forfeited	(84,444)
Stock Options Outstanding, Ending balance	548,193		420,766
Stock Options Outstanding, Exercisable at March 31, 2020	120,678
Weighted-average Exercise Price, Outstanding, Beginning balance	$ 17.71
Weighted-average Exercise Price, Granted	52.28
Weighted-average Exercise Price, Exercised	14.22
Weighted-average Exercise Price, Cancelled or forfeited	21.28
Weighted-average Exercise Price, Outstanding, Ending balance	31.71		$ 17.71
Weighted-average Exercise Price, Exercisable at March 31, 2020	$ 8.79
Weighted-average Remaining Contractual Life (Years)	8 years 9 months 18 days		8 years 4 months 24 days
Weighted-average Remaining Contractual Life (Years), Exercisable	7 years 6 months
Aggregate intrinsic value, Outstanding, Beginning balance	$ 15,859
Exercised	3,348
Aggregate intrinsic value, Outstanding, Ending balance	8,684		$ 15,859
Aggregate Intrinsic Value, Exercisable	$ 4,158

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	20,000,000	20,000,000
Convertible preferred stock, shares issued	2,061,773	2,061,773
Convertible preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	80,000,000	80,000,000
Common stock, shares issued	17,370,564	17,354,310
Common stock, shares outstanding	17,370,564	17,354,310

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (44,388)	$ (39,047)
Cash, cash equivalents and short-term investments	$ 186,700

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) Segment Agreement	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Significant Accounting Policies [Line Items]
Number of operating segment \| Segment	1
Number of lease agreements \| Agreement	2
Operating lease right-of-use asset	$ 2,633		$ 2,709	$ 1,100
Operating lease liability	3,210			$ 1,400
Equipment [Member]
Significant Accounting Policies [Line Items]
Recognized impairment losses for long lived assets	$ 0	$ 0

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Detail)	3 Months Ended
	Mar. 31, 2020
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	7 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	shorter of 8 years and remaining life of lease
Leasehold Improvements [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	8 years

Commitments and Contingencies - Additional Information (Detail) $ in Thousands		3 Months Ended
	May 31, 2016	Mar. 31, 2020 USD ($) ft²	Mar. 31, 2019 USD ($)	Jan. 21, 2020 USD ($)	Dec. 26, 2019 ft²
Operating Leased Assets [Line Items]
Lease expiration date		Feb. 28, 2027
Additional area of real estate property leased \| ft²		6,000
Rent expense		$ 178	$ 125
Estimated remaining commitment		530
Clinical Supply Agreements [Member]
Operating Leased Assets [Line Items]
Estimated remaining commitment		3,000
Project management service fee		$ 634	$ 803
2016 Lease Agreement [Member]
Operating Leased Assets [Line Items]
Lease expiration date	Oct. 31, 2017
Additional area of real estate property leased \| ft²		31,000
ASTRA Facility [Member]
Operating Leased Assets [Line Items]
Lease termination date		Oct. 31, 2035
Cash contribution				$ 2,400
ASTRA Facility [Member] \| Pennsylvania [Member]
Operating Leased Assets [Line Items]
Facility, square foot area \| ft²					100,000

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Detail) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Common share equivalents outstanding, excluded from the calculation of diluted net loss per common share	548,193	443,362

Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss Per Share and Per Unit (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss per common share	$ (5,341)	$ (4,111)
Denominator:
Weighted-average basic and diluted common shares	17,359,356	14,417,649
Basic and diluted net loss per common share	$ (0.31)	$ (0.29)

Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 11,445	$ 9,325
Accumulated depreciation and amortization	(1,181)	(850)
Property and equipment, net	10,264	8,475
Construction-in-progress [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	2,299	2,431
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	4,681	3,179
Furniture & Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	440	99
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	67	45
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 3,958	$ 3,571

Balance Sheet Components - Schedule of Accrued Expenses And Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued preclinical and clinical expenses	$ 745	$ 991
Accrued professional fees	76	72
Accrued payroll and benefits	812	510
Accrued taxes	50	40
Accrued construction in progress and laboratory equipment	1,020	491
Other current liabilities	213	19
Total	$ 2,916	$ 2,123

Capitalization - Additional Information (Detail) - USD ($)				3 Months Ended
	Jul. 03, 2019	Jun. 27, 2019	Nov. 01, 2017	Mar. 31, 2020	Mar. 31, 2019
Schedule of Capitalization, Equity [Line Items]
Proceeds from issue of common stock				$ 243,000	$ 40,000
Public Offering [Member]
Schedule of Capitalization, Equity [Line Items]
Number of additional shares issued and sold		2,500,000
Shares issued, price per share		$ 40.00
Proceeds from initial offering of shares		$ 93,800,000
Underwriting discounts and commissions		6,000,000
Offering expenses		216,000
Over-Allotment Option [Member]
Schedule of Capitalization, Equity [Line Items]
Number of additional shares issued and sold	353,946
Shares issued, price per share	$ 40.00
Underwriting discounts and commissions	$ 849,000
Proceeds from issue of common stock	$ 13,300,000
ATM Facilty [Member]
Schedule of Capitalization, Equity [Line Items]
Agreed sale price of shares					$ 50,000,000
Common stock value suspended		$ 16,800,000
Stock Purchase Agreement [Member]
Schedule of Capitalization, Equity [Line Items]
Number of additional shares issued and sold			70,000
Shares issued, price per share			$ 11.00

Related Party Transactions - Additional Information (Detail) $ in Thousands	1 Months Ended
	Dec. 31, 2019 USD ($)
Management [Member]
Related Party Transaction [Line Items]
Advance to management team	$ 420