Krystal Biotech (KRYS) 10-Q 9 Aug 21 2021 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2021	Jul. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-38210
Entity Registrant Name	Krystal Biotech, Inc.
Entity Incorporation, State or Country Code	DE
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
Trading Symbol	KRYS
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		22,205,642
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001711279
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 329,527	$ 268,269
Short-term investments	38,203	2,993
Prepaid expenses and other current assets	2,197	3,796
Total current assets	369,927	275,058
Property and equipment, net	44,972	30,876
Long-term investments	21,411	0
Right-of-use assets	7,136	3,298
Other non-current assets	110	1,612
Total assets	443,556	310,844
Current liabilities
Accounts payable	1,265	2,105
Current portion of lease liability	934	638
Accrued expenses and other current liabilities	15,920	5,109
Build to suit lease liability	0	7,600
Total current liabilities	18,119	15,452
Lease liability	6,897	3,308
Total liabilities	25,016	18,760
Commitments and contingencies (Note 6)
Stockholders' equity
Preferred stock; $0.00001 par value; 20,000,000 shares authorized at    June 30, 2021 (unaudited) and December 31, 2020; 2,061,773    shares issued, and no shares outstanding at June 30, 2021    (unaudited) and December 31, 2020	0	0
Common stock; $0.00001 par value; 80,000,000 shares authorized at    June 30, 2021 (unaudited) and December 31, 2020; 22,205,032    and 19,714,220 shares issued and outstanding at June 30, 2021    (unaudited) and December 31, 2020, respectively	0	0
Additional paid-in capital	521,950	363,292
Accumulated other comprehensive income (expense)	(21)	6
Accumulated deficit	(103,389)	(71,214)
Total stockholders' equity	418,540	292,084
Total liabilities and stockholders' equity	$ 443,556	$ 310,844

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	2,061,773	2,061,773
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized	80,000,000	80,000,000
Common stock, shares issued	22,205,032	19,714,220
Common stock, shares outstanding	22,205,032	19,714,220

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Expenses
Research and development	$ 6,594	$ 3,639	$ 12,795	$ 7,164
General and administrative	9,799	3,315	17,951	5,735
Total operating expenses	16,393	6,954	30,746	12,899
Loss from operations	(16,393)	(6,954)	(30,746)	(12,899)
Other Income (Expense)
Interest and other income, net	30	121	64	725
Interest expense	0	0	(1,492)	0
Net loss	(16,363)	(6,833)	(32,174)	(12,174)
Unrealized gain (loss) on available-for-sale securities	(24)	16	(27)	30
Comprehensive loss	$ (16,387)	$ (6,817)	$ (32,201)	$ (12,144)
Net loss per common share: basic (in dollars per share)	$ (0.74)	$ (0.37)	$ (1.48)	$ (0.68)
Net loss per common share: diluted (in dollars per share)	$ (0.74)	$ (0.37)	$ (1.48)	$ (0.68)
Weighted-average common shares outstanding: basic	22,204,659	18,383,941	21,731,711	17,871,648
Weighted-average common shares outstanding: diluted	22,204,659	18,383,941	21,731,711	17,871,648

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 202,914		$ 241,951	$ 10	$ (39,047)
Beginning balance (in shares) at Dec. 31, 2019		17,354,310
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Issuance of common stock, net	243		243
Issuance of common stock, net, (in shares)		16,254
Stock-based compensation expense	539		539
Unrealized gain (loss) 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 (in shares) at Mar. 31, 2020		17,370,564
Beginning balance at Dec. 31, 2019	202,914		241,951	10	(39,047)
Beginning balance (in shares) at Dec. 31, 2019		17,354,310
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Unrealized gain (loss) on investments	30
Net loss	(12,174)
Ending balance at Jun. 30, 2020	309,696		360,877	40	(51,221)
Ending balance (in shares) at Jun. 30, 2020		19,664,059
Beginning balance at Mar. 31, 2020	198,369		242,733	24	(44,388)
Beginning balance (in shares) at Mar. 31, 2020		17,370,564
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Issuance of common stock, net	117,337		117,337
Issuance of common stock, net, (in shares)		2,293,495
Stock-based compensation expense	807		807
Unrealized gain (loss) on investments	16			16
Net loss	(6,833)				(6,833)
Ending balance at Jun. 30, 2020	309,696		360,877	40	(51,221)
Ending balance (in shares) at Jun. 30, 2020		19,664,059
Beginning balance at Dec. 31, 2020	292,084		363,292	6	(71,214)
Beginning balance (in shares) at Dec. 31, 2020		19,714,220
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Issuance of common stock, net	152,033		152,033
Issuance of common stock, net, (in shares)		2,489,837
Stock-based compensation expense	2,350		2,350
Unrealized gain (loss) on investments	(3)			(3)
Net loss	(15,812)				(15,812)
Ending balance at Mar. 31, 2021	430,652		517,675	3	(87,026)
Ending balance (in shares) at Mar. 31, 2021		22,204,057
Beginning balance at Dec. 31, 2020	292,084		363,292	6	(71,214)
Beginning balance (in shares) at Dec. 31, 2020		19,714,220
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Unrealized gain (loss) on investments	(27)
Net loss	(32,174)
Ending balance at Jun. 30, 2021	418,540		521,950	(21)	(103,389)
Ending balance (in shares) at Jun. 30, 2021		22,205,032
Beginning balance at Mar. 31, 2021	430,652		517,675	3	(87,026)
Beginning balance (in shares) at Mar. 31, 2021		22,204,057
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Issuance of common stock, net	14		14
Issuance of common stock, net, (in shares)		975
Stock-based compensation expense	4,261		4,261
Unrealized gain (loss) on investments	(24)			(24)
Net loss	(16,363)				(16,363)
Ending balance at Jun. 30, 2021	$ 418,540		$ 521,950	$ (21)	$ (103,389)
Ending balance (in shares) at Jun. 30, 2021		22,205,032

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating Activities
Net loss	$ (32,174)	$ (12,174)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	1,202	884
Stock-based compensation expense	6,508	1,346
Loss on disposals of fixed assets	0	3
Non-cash interest expense	1,492	0
Changes in operating assets and liabilities
Prepaid expenses and other current assets	1,366	378
Prepaid rent	0	(2,400)
Lease liability	(175)	(105)
Accounts payable	(680)	706
Accrued expenses and other current liabilities	2,678	81
Net cash used in operating activities	(19,783)	(11,281)
Investing Activities
Purchases of property and equipment	(6,462)	(3,454)
Purchases of short-term investments	(38,103)	(3,205)
Proceeds from maturities of short-term investments	2,959	4,392
Purchases of long-term investments	(21,458)	0
Net cash used in investing activities	(63,064)	(2,267)
Financing Activities
Issuance of common stock, net	152,065	117,712
Repayment of ASTRA build to suit liability	(7,960)	0
Net cash provided by financing activities	144,105	117,712
Net increase in cash and cash equivalents	61,258	104,164
Cash and cash equivalents at beginning of period	268,269	187,514
Cash and cash equivalents at end of period	329,527	291,678
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Unpaid purchases of property and equipment	10,143	2,675
Unpaid offering costs	36	132
Initial recognition of right-of-use assets and modification	$ 4,060	$ 0

Organization

Organization	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Organization	Organization Krystal Biotech, Inc. (the “Company,” or “we” or other similar pronouns) commenced operations on April 15, 2016. On March 31, 2017, the Company converted from a California limited liability company to a Delaware C-corporation, and changed its name from Krystal Biotech LLC to Krystal Biotech, Inc. On June 19, 2018, the Company incorporated Krystal Australia Pty Ltd., an Australian proprietary limited company, for the purpose of undertaking preclinical and clinical studies in Australia. On April 24, 2019, the Company incorporated Jeune Aesthtics, Inc., formerly known as Jeune, Inc. ("Jeune"), in Delaware, a wholly-owned subsidiary, for the purpose of undertaking preclinical and clinical studies for aesthetic skin conditions. We are a clinical stage biotechnology company leading the field of redosable gene therapy for the treatment of serious rare diseases. Using our patented platform that is based on engineered herpes simplex virus type 1 ("HSV-1"), we create vectors that efficiently deliver therapeutic transgenes to cells of interest in multiple organ systems. The cell’s own machinery then transcribes and translates the encoded effector to treat or prevent disease. We formulate our vectors for non-invasive or minimally invasive routes of administration at a doctor’s office or potentially in the patient’s home by a healthcare professional. Our goal is to develop easy to use, medicines to dramatically improve the lives of patients living with rare diseases. Our innovative technology platform is supported by in-house, commercial scale current good manufacturing practices ("cGMP") manufacturing capabilities. Liquidity As of June 30, 2021, the Company had an accumulated deficit of $103.4 million. With the net proceeds raised from its public and private securities offerings, including the public offering of its common stock completed on February 1, 2021, the Company believes that its cash, cash equivalents and short-term investments of approximately $367.7 million as of June 30, 2021 will be sufficient to allow the Company to fund its planned operations for at least the next 12 months from the date of this Quarterly Report on Form 10-Q. As the Company continues to incur losses, a transition to profitability is dependent upon the successful development, approval and commercialization of its product candidates and the achievement of a level of revenues adequate to support the Company’s cost structure. The Company may never achieve profitability and unless and until it does, the Company will continue to need to raise additional capital or obtain financing from other sources. Management intends to fund future operations through the sale of equity and debt financings and may also seek additional capital through arrangements with strategic partners or other sources. There can be no assurance that additional funding will be available on terms acceptable to the Company, if at all. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to the failure of product candidates in clinical and preclinical studies, the development of competing product candidates or other technological innovations by competitors, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to c ommercialize product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”), as found in the Accounting Standards Codification (“ASC”), the Accounting Standards Update (“ASU”), of the Financial Accounting Standards Board (“FASB”), and the rules and regulations of the US Securities and Exchange Commission (“SEC”). All intercompany balances and transactions have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform to the current period presentation. The reclassified amounts have no impact on the Company’s previously reported financial position or results of operation. These unaudited interim condensed financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020, as filed with the SEC on March 1, 2021. Risks and Uncertainties The novel coronavirus ("COVID-19") pandemic has resulted, and is likely to continue to result, in significant national and global economic uncertainty and may adversely affect our business. The Company is continuing to actively monitor the impact of the COVID-19 pandemic and the related 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 2021. Use of Estimates The preparation of financial statements in conformity with 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 expenses, the fair value of financial instruments, the incremental borrowing rate for lease liabilities, and the valuation allowance included in the 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, corporate bonds, commercial paper, government agency securities 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 certificates of deposit, commercial paper, corporate bonds, and government agency securities. Investments with maturities of greater than one year are classified as long-term investments on the consolidated balance sheets and consist of corporate bonds and government agency securities. Accrued interest on corporate bonds and government agency securities 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.it 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 of its investments as available-for-sale. Our available-for-sale, short-term and long-term investments, which consist of certificates of deposit, commercial paper, corporate bonds, and government agency securities 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 3 -7 years Furniture and fixtures 3 years Leasehold improvement lesser of remaining useful life or remaining lease term Construction in progress ("CIP") 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 and six months ended June 30, 2021 and 2020. Leases The Company accounts for its lease agreements in accordance with FASB ASC Topic 842, Leases ("ASC 842"). Right-of-use lease assets represent our right to use an underlying asset during the lease term and the lease obligations represent our commitment to make lease payments arising from the lease. Right-of-use lease assets and obligations are recognized based on the present value of remaining lease payments over the lease term. As the Company’s lease agreements do not provide an implicit rate and as the Company does not have any external borrowings, we have used an estimated incremental borrowing rate based on the information available at lease commencement in determining the present value of lease payments. Operating lease expense is recognized on a straight-line basis over the lease term. Variable lease expense is recognized in the period in which the obligation for the payment is incurred. 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 and to account for lease and non-lease components of its operating leases as a single component. For lease arrangements where it has been determined that the Company has control over an asset that is under construction and is thus considered the accounting owner of the asset during the construction period, the Company records a construction in progress asset and corresponding financial obligation on the condensed consolidated balance sheet. Once the construction is complete, an assessment is performed to determine whether the lease meets certain "sale-leaseback" criteria. If the sale-leaseback criteria are determined to be met, the Company will remove the asset and related financial obligation from the condensed consolidated balance sheet and treat the lease as either an operating or finance lease based on our assessment of the guidance. If, upon completion of construction, the project does not meet the "sale-leaseback" criteria, the lease will be treated as a financing obligation and the Company will depreciate the asset over its estimated useful life for financial reporting purposes once the asset has been placed into service. Research and Development Expenses Research and development costs are charged to expense as incurred in performing research and development activities. These costs include employee compensation costs, facilities and overhead, preclinical and clinical activities, related clinical manufacturing costs, contract management services, 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 organizations and manufacturing organizations that manufacture materials used in the Company’s ongoing preclinical and clinical studies. Non-refundable 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 (“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 accounts for forfeitures as they occur. Stock-based compensation expense recognized in the financial statements is based on awards for which service conditions are expected to be satisfied. Comprehensive Loss Comprehensive loss is defined as the change in equity during a period from transactions from non-owner sources. Unrealized gains or losses on available-for-sale securities is a component of other comprehensive gains or losses and is presented net of taxes. We have not recorded any reclassifications from other comprehensive gains or losses to net loss during any period presented. Recent Accounting Pronouncements ASU No. 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs In October 2020, the FASB issued ASU 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs ("ASU 2020-08") to provide further clarification and update the previously issued guidance in ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20: Premium Amortization on Purchased Callable Debt Securities) ("ASU 2017-08"). ASU 2017-08 shortened the amortization period for certain callable debt securities purchased at a premium by requiring that the premium be amortized to the earliest call date. ASU 2020-08 requires that at each reporting period, to the extent that the amortized cost of an individual callable debt security exceeds the amount repayable by the issuer at the next call date, the excess premium shall be amortized to the next call date. The new standard was effective beginning January 1, 2021 and should be applied on a prospective basis as of the beginning of the period of adoption for existing or newly purchased callable debt securities. The adoption of ASU 2020-08 did not have a material impact on the Company's financial position or results of operations upon adoption.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss by the weighted-average number of shares of common stock and common share equivalents outstanding for the period. Common share equivalents consist of common stock issuable upon exercise of stock options and vesting of restricted stock awards. There were 1,688,965 and 831,110 common share equivalents outstanding as of June 30, 2021 and 2020, respectively, in the form of stock options and unvested restricted stock awards, that have been excluded from the calculation of diluted net loss per common share as their effect would be anti-dilutive for all periods presented. Three Months Ended Six Months Ended 2021 2020 2021 2020 (In thousands, except shares and per share data) (Unaudited) (Unaudited) Numerator: Net loss per common share $ (16,363) $ (6,833) $ (32,174) $ (12,174) Denominator: Weighted-average basic and diluted common shares 22,204,659 18,383,941 21,731,711 17,871,648 Basic and diluted net loss per $ (0.74) $ (0.37) $ (1.48) $ (0.68)

Fair Value Instruments

Fair Value Instruments	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Instruments	Fair Value Instruments The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category as of June 30, 2021 and December 31, 2020, respectively (in thousands): June 30, 2021 (unaudited) Amortized Cost Gross Gross Aggregate Fair Cash and Cash Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash and cash equivalents $ 329,527 $ — $ — $ 329,527 $ 329,527 $ — $ — Subtotal 329,527 — — 329,527 329,527 — — Level 2: Commercial paper 17,483 3 — 17,486 — 17,486 — Corporate bonds 30,588 1 (22) 30,567 — 18,209 12,358 U.S. government agency securities 11,567 — (6) 11,561 — 2,508 9,053 Subtotal 59,638 4 (28) 59,614 — 38,203 21,411 Total $ 389,165 $ 4 $ (28) $ 389,141 $ 329,527 $ 38,203 $ 21,411 December 31, 2020 Amortized Cost Gross Gross Aggregate Fair Cash and Cash Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash and cash equivalents $ 268,269 $ — $ — $ 268,269 $ 268,269 $ — $ — Subtotal 268,269 — — 268,269 268,269 — — Level 2: Certificates of deposit 2,986 7 — 2,993 — 2,993 — Subtotal 2,986 7 — 2,993 — 2,993 — Total $ 271,255 $ 7 $ — $ 271,262 $ 268,269 $ 2,993 $ — (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 year and two years. See Note 2 to these unaudited condensed consolidated financial statements for additional discussion regarding the Company’s fair value measurements.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components Property and Equipment, Net Property and equipment, net consist of the following (in thousands): June 30, December 31, (Unaudited) Construction in progress $ 36,180 $ 23,031 Leasehold improvements 5,725 4,631 Furniture and fixtures 891 870 Computer equipment and software 82 82 Laboratory equipment 5,376 4,630 Total property and equipment 48,254 33,244 Accumulated depreciation and amortization (3,282) (2,368) Property and equipment, net $ 44,972 $ 30,876 Depreciation expense was $475 thousand and $914 thousand for the three and six months ended June 30, 2021 and $394 thousand and $729 thousand three and six months ended June 30, 2020, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, December 31, (Unaudited) Accrued preclinical and clinical expenses $ 2,970 $ 1,735 Accrued professional fees 2,119 642 Accrued payroll and benefits 1,273 1,486 Accrued taxes 22 40 Accrued construction in progress 9,170 1,049 Accrued financing costs 36 131 Other current liabilities 330 26 Total $ 15,920 $ 5,109

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Significant Contracts and Agreements Lease Agreements On May 26, 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 has been amended several times to increase the area leased, which currently consists of approximately 41,000 square feet. As a result of the lease amendments, the lease expiration date was extended to October 31, 2031. On December 26, 2019, we entered into a lease agreement for our second commercial gene therapy facility ("ASTRA") in the Pittsburgh, Pennsylvania area ("ASTRA lease") with Northfield I, LLC (the "Landlord" or "Northfield") with an initial lease term that expired on October 31, 2035. The ASTRA lease contained an option ("Purchase Option") to purchase the building, related improvements and take corresponding assignment of the Landlord's rights under its existing Ground Lease (the "Ground Lease"). 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, was recorded as prepaid rent in the consolidated balance sheet at the time of payment. On October 5, 2020, the Company was provided with notice that the initial delivery conditions of the building had been met, including completion of the building shell, interior slab, and exterior doors, and on October 15, 2020, the Company gave the Landlord notice of its intent to purchase ASTRA for approximately $9.4 million, subject to the parties entering into a commercially reasonable purchase and sale agreement. As a result of the Company's ability to exercise its option to purchase ASTRA, the Company obtained control over the construction in progress of ASTRA as of October 5, 2020. The Company recorded a $10.0 million CIP asset and a corresponding build to suit lease liability related to the costs incurred by the Landlord, offset by the previous cash contribution of $2.4 million. On January 29, 2021, the Company entered into a Purchase and Sale Agreement ("PSA") for ASTRA with Northfield related to the purchase option exercised by the Company on October 15, 2020, for a purchase price of $9.4 million. The Company held approximately $1.5 million on deposit with Northfield under the existing lease agreement and applied this deposit as a credit against the purchase price at closing. On February 1, 2021, Northfield delivered the space as substantially complete and made the space available for access by the Company, thus triggering lease commencement. As a result, the Company concluded that this transaction did not qualify for sale-leaseback accounting because it did not meet the definition of a sale. As control did not transfer to the Lessor at lease commencement, the transaction continued to be accounted for as construction in progress and a financing obligation. On March 5, 2021, the purchase closed and the Company determined that reclassification of the construction in progress to buildings and leasehold improvements was not appropriate as the interior of the building was not yet ready for its intended use. The building continues to be held under construction in progress as of June 30, 2021. The interior of the building is currently under construction and is expected to be completed and validated in 2022. From construction completion to the closing of the purchase, the Company recognized interest expense to accrete the financial obligation to a balance that equaled the cash consideration that was paid upon the close of purchase. For more information about the expected construction costs associated with ASTRA, see "ASTRA Contractual Obligation" below. As part of the transaction, the Company also became the accounting owner of the Ground Lease, due to obtaining control over ASTRA, and recorded the applicable operating right-of-use asset and corresponding lease liability as of October 5, 2020. When the PSA was finalized, the Company took assignment of the Lessor's Ground Lease, in accordance with the Purchase Option, of which lease payments are based on annual payments of $82 thousand, and are subject to a cumulative 10% escalation clause every 5 years through 2071. As of June 30, 2021, future minimum commitments under the Company’s operating leases were as follows (in thousands): Operating 2021 (remaining six months) $ 457 2022 1,048 2023 1,067 2024 1,087 2025 1,113 Thereafter 12,480 Future minimum operating lease payments $ 17,252 Less: Interest 9,421 Present value of lease liability $ 7,831 Supplemental condensed consolidated balance sheet information related to leases is as follows: (unaudited) June 30, 2021 December 31, 2020 Operating leases: Right-of-use assets $ 7,136 $ 3,298 Current portion of lease liability 934 638 Lease liability 6,897 3,308 Total lease liability $ 7,831 $ 3,946 Weighted average remaining lease term, in years 15.0 16.4 Weighted average discount rate 9.3 % 9.4 % The Company recorded operating lease costs of $278 thousand and $497 thousand for the three and six months ended June 30, 2021 and $145 thousand and $310 thousand for the three and six months ended June 30, 2020, respectively, and variable lease costs of $81 thousand and $118 thousand for the three and six months ended June 30, 2021 and $15 thousand and $28 thousand for the three and six months ended June 30, 2020, respectively. Agreements with Contract Manufacturing Organizations and Contract Research Organizations The Company has entered into various agreements with Contract Manufacturing Organizations (“CMOs”) for the manufacture of sterile excipients that are formulated with in-house produced vectors as part of the final drug product applied in certain of our clinical trials. The Company has also entered into agreements with third-party Contract Research Organizations ("CROs") to provide research and development services to further the Company’s analysis of its product candidates. The agreements entered into with the CMOs and CROs provide the terms and conditions for their respective services, which may include research and development activities, storage, packaging, labelling, and/or testing of our preclinical and clinical-stage products. The Company is obligated to make milestone payments under certain of these agreements. The estimated remaining commitment as of June 30, 2021 under these agreements is approximately $3.8 million. The Company may also be 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 $718 thousand and $2.5 million for the three and six months ended June 30, 2021 and $330 thousand and $964 thousand for the three and six months ended June 30, 2020, respectively. Other Contractual Obligations The Company has 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 June 30, 2021 is $4.0 million. The Company has incurred expenses under these activities of $974 thousand and $2.3 million for the three and six months ended June 30, 2021 and $489 thousand for the three and six months ended June 30, 2020, respectively. ASTRA Contractual Obligations The Company has contracted with various third parties to construct our second cGMP facility, ASTRA. Additionally, we have entered into various non-cancellable purchase agreements for long-lead materials to help avoid potential schedule disruptions or material shortages. These contracts typically call for the payment of fees for services or materials upon the achievement of certain milestones. The estimated remaining commitment as of June 30, 2021 is $38.0 million. The Company has included costs incurred to-date associated with ASTRA within construction in progress as of June 30, 2021. On June 30, 2021, the Company entered into a Standard Form of Contract for Construction and the corresponding General Conditions of the Contract for Construction (collectively, the “Agreement”) with The Whiting-Turner Contracting Company (“Whiting-Turner”), pursuant to which Whiting-Turner is constructing and managing the construction of ASTRA. Subject to certain conditions in the Agreement, the Company will pay Whiting-Turner a contract price consisting of the cost of work plus a fee equal to 1.75% of the cost of work, subject to a guaranteed maximum price to be agreed upon in an amendment to the Agreement at a later date. Legal Proceedings On May 1, 2020, a complaint was filed against us in the United States District Court for the Western District of Pennsylvania by PeriphaGen, Inc., which also named our Chief Executive Officer and Chief Operating Officer, Krish Krishnan and Suma Krishnan, respectively. The complaint alleges breach of contract and misappropriation of trade secrets, which secrets the plaintiff asserts were used to develop our product candidates, including the vector backbones, and our STAR-D platform. We answered the complaint on June 26, 2020 by denying the allegations and brought a counterclaim asking the court to declare that we did not misappropriate PeriphaGen’s trade secrets or confidential information, and to further declare that we are the rightful and sole owner of our product candidates and STAR-D platform. In addition, we filed a third-party complaint against two principals of PeriphaGen, James Wechuck and David Krisky, alleging breach of contract and seeking contribution and indemnification from them in the event PeriphaGen is awarded damages. On July 29, 2020, PeriphaGen filed its response to our answer and counterclaim, denying the allegations in the counterclaim. On the same day, Messrs Wechuck and Krisky filed a motion to dismiss the third-party complaint on various grounds, and we opposed the motion. On December 1, 2020, the court ruled on Messrs. Wechuck and Krisky's motion to dismiss our third-party complaint. The court determined that our claims for contribution and indemnification based on PeriphaGen's state law claims for unfair competition and misappropriation of trade secrets can proceed. Our breach of contract claim will also go forward in full. Fact discovery is ongoing. While we are unable to provide any assurances as to the ultimate outcome of the case, we believe the allegations in the complaint are without merit, and we intend to vigorously defend against them. We are currently unable to estimate the costs and timing of any litigation, including any potential damages if PeriphaGen were to prevail on its claims.

Capitalization

Capitalization	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Capitalization	Capitalization Sale of Common Stock On February 1, 2021, the Company completed a public offering of 2,211,538 shares of its common stock, including 288,461 shares purchased by the underwriters, at $65.00 per share. Net proceeds to the Company from the offering were $134.9 million after deducting underwriting discounts and commissions of approximately $8.6 million, and other offering expenses payable by the Company of $198 thousand. On December 31, 2020, the Company entered into a sales agreement (the "Sales Agreement") with Cowen and Company, LLC ("Cowen") with respect to an at-the-market equity offering program ("ATM Program"), under which Cowen will act as the Company's agent and/or principal and may issue and sell from time to time, during the term of the Sales Agreement, shares of our common stock, par value $0.0001 per share, having an aggregate offering price up to $150.0 million ("Placement Shares"). Related offering expenses payable by the Company were $172 thousand. The issuance and sale of the Placement Shares by the Company under the Sales Agreement will be made pursuant to the Company's effective "shelf" registration statement on Form S-3. During the six months ended June 30, 2021, 262,500 shares of common stock were issued pursuant to the ATM Program at a weighted average price of $66.50 per share for net proceeds of $17.5 million, resulting in a remaining $132.5 million available for issuance under the ATM Program. On May 21, 2020, the Company completed a public offering of 2,275,000 shares of its common stock to the public at $55.00 per share. Net proceeds to the Company from the offering were $117.2 million after deducting underwriting discounts and commissions of approximately $7.5 million, and other offering expenses payable by the Company of approximately $463 thousand.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock Options Stock options granted to employees vest ratably over four-year periods and options granted to directors of the company vest ratably over one year to four-year periods. Stock options have a life of ten years. The Company granted 297,500 and 799,950 stock options to employees and directors of the Company during the three and six months ended June 30, 2021, respectively, and 315,400 and 544,400 stock options to employees and directors of the Company during the three and six months ended June 30, 2020, respectively. The following table summarizes the Company’s stock option activity: Stock Weighted- Weighted- Aggregate Intrinsic Value (In thousands) (1) Outstanding at December 31, 2020 853,614 $ 40.31 9.0 $ 16,804 Granted 799,950 $ 73.42 Exercised (16,874) $ 21.41 Cancelled or forfeited (46,525) $ 53.79 Outstanding at June 30, 2021 1,590,165 $ 56.77 9.0 $ 22,838 Exercisable at June 30, 2021 253,189 $ 29.73 6.9 $ 9,690 (1) Aggregate intrinsic value represents the difference between the closing stock price of our common stock on June 30, 2021 and the exercise price of outstanding in-the-money options. The total intrinsic value (the amount by which the fair market value exceed the exercise price) of stock options exercised during the three and six months ended June 30, 2021 was $808 thousand and $872 thousand, respectively, and during the three and six months ended June 30, 2020 was $656 thousand and $1.2 million, respectively. The weighted-average grant-date fair value per share of options granted to employees during the three and six months ended June 30, 2021 was $42.53 and $47.25, respectively, and during the three and six months ended June 30, 2020 was $29.78 and $31.71, respectively. There was $49.0 million of unrecognized stock-based compensation expense related to employees’ option awards that is expected to be recognized over a weighted-average period of 3.4 years as of June 30, 2021. The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards in the condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (unaudited) (unaudited) Research and development $ 1,084 $ 181 $ 1,600 $ 370 General and administrative 2,625 626 4,240 976 Total stock-based compensation $ 3,709 $ 807 $ 5,840 $ 1,346 We capitalize the portion of stock-based compensation that relates to work performed on the construction of new buildings. There was $66 thousand and $103 thousand of stock-based compensation that was capitalized in the three and six months ended June 30, 2021, respectively, and zero of stock-based compensation that was capitalized in the three and six months ended June 30, 2020, respectively. The Company recorded stock-based compensation expense of $3.7 million and $5.8 million for the three and six months ended June 30, 2021, respectively, and $807 thousand and $1.3 million for the three and six months ended June 30, 2020, respectively. The fair value of options was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions for the three and six months ended June 30, 2021 and 2020: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Expected stock price volatility 72 % 76 % 72 % 75 % Expected term of the award (years) 6.10 6.18 6.18 6.20 Risk-free interest rate 1.05 % 0.41 % 1.02 % 0.78 % Weighted average exercise price $ 66.58 $ 45.07 $ 73.42 $ 48.09 Forfeiture rate — % 6.42 % — % 6.42 % Restricted Stock Awards Restricted stock awards ("RSAs") granted to employees vest ratably over a four-year period. Restricted stock awards have a life of ten years. The Company granted zero and 98,800 RSAs to employees of the Company during the three and six months ended June 30, 2021, respectively, and zero RSAs to employees of the Company during the three and six months ended June 30, 2020, respectively. The following table summarizes the Company’s RSA activity: Number of Shares Weighted Average Non-vested RSAs as of December 31, 2020 — $ — Granted 98,800 $ 78.89 Vested — $ — Forfeited — $ — Non-vested RSAs as of June 30, 2021 98,800 $ 78.89 As of June 30, 2021, 98,800 RSAs were outstanding. The fair value of each restricted stock was $78.89 reflecting the closing price of our common stock on the grant date. The Company recorded stock-based compensation expense related to RSAs of $486 thousand and $668 thousand for the three and six months ended June 30, 2021 and zero for the three and six months ended June 30, 2020, respectively, within general and administrative expenses in the accompanying condensed consolidated statements of operations (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (unaudited) (unaudited) General and administrative $ 486 $ — $ 668 $ — Total stock-based compensation $ 486 $ — $ 668 $ — Shares remaining available for grant under the Company’s stock incentive plan were 1,626,006, with a sublimit for incentive stock options of 379,566, at June 30, 2021.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsIn December 2019, the Company advanced $420 thousand to a member of our management team to cover the personal payroll and income taxes on their taxable income from NSO exercises. This employee repaid the Company in full in January 2020.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company evaluates events or transactions that occur after the balance sheet date, but prior to the issuance of the financial statements, to identify matters that require disclosure. The Company concluded that no subsequent events have occurred that would require recognition or disclosure in the condensed consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”), as found in the Accounting Standards Codification (“ASC”), the Accounting Standards Update (“ASU”), of the Financial Accounting Standards Board (“FASB”), and the rules and regulations of the US Securities and Exchange Commission (“SEC”). All intercompany balances and transactions have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform to the current period presentation. The reclassified amounts have no impact on the Company’s previously reported financial position or results of operation. These unaudited interim condensed financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020, as filed with the SEC on March 1, 2021.
Risks and Uncertainties	Risks and Uncertainties The novel coronavirus ("COVID-19") pandemic has resulted, and is likely to continue to result, in significant national and global economic uncertainty and may adversely affect our business. The Company is continuing to actively monitor the impact of the COVID-19 pandemic and the related 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 2021.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts 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 expenses, the fair value of financial instruments, the incremental borrowing rate for lease liabilities, and the valuation allowance included in the deferred income tax calculation.
Segment and Geographical Information	Segment and Geographical InformationOperating 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	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, corporate bonds, commercial paper, government agency securities 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, 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 certificates of deposit, commercial paper, corporate bonds, and government agency securities. Investments with maturities of greater than one year are classified as long-term investments on the consolidated balance sheets and consist of corporate bonds and government agency securities. Accrued interest on corporate bonds and government agency securities are also classified as short-term investments.
Fair Value of Financial Instruments	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 of its investments as available-for-sale. Our available-for-sale, short-term and long-term investments, which consist of certificates of deposit, commercial paper, corporate bonds, and government agency securities 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 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 3 -7 years Furniture and fixtures 3 years Leasehold improvement lesser of remaining useful life or remaining lease term Construction in progress ("CIP") is not depreciated until the asset is placed in service.
Impairment of Long-Lived Assets	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 and six months ended June 30, 2021 and 2020.
Leases	Leases The Company accounts for its lease agreements in accordance with FASB ASC Topic 842, Leases ("ASC 842"). Right-of-use lease assets represent our right to use an underlying asset during the lease term and the lease obligations represent our commitment to make lease payments arising from the lease. Right-of-use lease assets and obligations are recognized based on the present value of remaining lease payments over the lease term. As the Company’s lease agreements do not provide an implicit rate and as the Company does not have any external borrowings, we have used an estimated incremental borrowing rate based on the information available at lease commencement in determining the present value of lease payments. Operating lease expense is recognized on a straight-line basis over the lease term. Variable lease expense is recognized in the period in which the obligation for the payment is incurred. 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 and to account for lease and non-lease components of its operating leases as a single component. For lease arrangements where it has been determined that the Company has control over an asset that is under construction and is thus considered the accounting owner of the asset during the construction period, the Company records a construction in progress asset and corresponding financial obligation on the condensed consolidated balance sheet. Once the construction is complete, an assessment is performed to determine whether the lease meets certain "sale-leaseback" criteria. If the sale-leaseback criteria are determined to be met, the Company will remove the asset and related financial obligation from the condensed consolidated balance sheet and treat the lease as either an operating or finance lease based on our assessment of the guidance. If, upon completion of construction, the project does not meet the "sale-leaseback" criteria, the lease will be treated as a financing obligation and the Company will depreciate the asset over its estimated useful life for financial reporting purposes once the asset has been placed into service.
Research and Development Expenses	Research and Development Expenses Research and development costs are charged to expense as incurred in performing research and development activities. These costs include employee compensation costs, facilities and overhead, preclinical and clinical activities, related clinical manufacturing costs, contract management services, 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 organizations and manufacturing organizations that manufacture materials used in the Company’s ongoing preclinical and clinical studies. Non-refundable 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	Stock-Based Compensation Expense The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation-Stock Compensation (“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.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity during a period from transactions from non-owner sources. Unrealized gains or losses on available-for-sale securities is a component of other comprehensive gains or losses and is presented net of taxes. We have not recorded any reclassifications from other comprehensive gains or losses to net loss during any period presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements ASU No. 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs In October 2020, the FASB issued ASU 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs ("ASU 2020-08") to provide further clarification and update the previously issued guidance in ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20: Premium Amortization on Purchased Callable Debt Securities) ("ASU 2017-08"). ASU 2017-08 shortened the amortization period for certain callable debt securities purchased at a premium by requiring that the premium be amortized to the earliest call date. ASU 2020-08 requires that at each reporting period, to the extent that the amortized cost of an individual callable debt security exceeds the amount repayable by the issuer at the next call date, the excess premium shall be amortized to the next call date. The new standard was effective beginning January 1, 2021 and should be applied on a prospective basis as of the beginning of the period of adoption for existing or newly purchased callable debt securities. The adoption of ASU 2020-08 did not have a material impact on the Company's financial position or results of operations upon adoption.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Estimated Useful Lives of Assets	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 3 -7 years Furniture and fixtures 3 years Leasehold improvement lesser of remaining useful life or remaining lease term

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Net Loss Per Share Attributable to Common Stockholders	Three Months Ended Six Months Ended 2021 2020 2021 2020 (In thousands, except shares and per share data) (Unaudited) (Unaudited) Numerator: Net loss per common share $ (16,363) $ (6,833) $ (32,174) $ (12,174) Denominator: Weighted-average basic and diluted common shares 22,204,659 18,383,941 21,731,711 17,871,648 Basic and diluted net loss per $ (0.74) $ (0.37) $ (1.48) $ (0.68)

Fair Value Instruments (Tables)

Fair Value Instruments (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Cash, Cash Equivalents and Available-for-Sale Securities	The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category as of June 30, 2021 and December 31, 2020, respectively (in thousands): June 30, 2021 (unaudited) Amortized Cost Gross Gross Aggregate Fair Cash and Cash Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash and cash equivalents $ 329,527 $ — $ — $ 329,527 $ 329,527 $ — $ — Subtotal 329,527 — — 329,527 329,527 — — Level 2: Commercial paper 17,483 3 — 17,486 — 17,486 — Corporate bonds 30,588 1 (22) 30,567 — 18,209 12,358 U.S. government agency securities 11,567 — (6) 11,561 — 2,508 9,053 Subtotal 59,638 4 (28) 59,614 — 38,203 21,411 Total $ 389,165 $ 4 $ (28) $ 389,141 $ 329,527 $ 38,203 $ 21,411 December 31, 2020 Amortized Cost Gross Gross Aggregate Fair Cash and Cash Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash and cash equivalents $ 268,269 $ — $ — $ 268,269 $ 268,269 $ — $ — Subtotal 268,269 — — 268,269 268,269 — — Level 2: Certificates of deposit 2,986 7 — 2,993 — 2,993 — Subtotal 2,986 7 — 2,993 — 2,993 — Total $ 271,255 $ 7 $ — $ 271,262 $ 268,269 $ 2,993 $ — (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 year and two years.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consist of the following (in thousands): June 30, December 31, (Unaudited) Construction in progress $ 36,180 $ 23,031 Leasehold improvements 5,725 4,631 Furniture and fixtures 891 870 Computer equipment and software 82 82 Laboratory equipment 5,376 4,630 Total property and equipment 48,254 33,244 Accumulated depreciation and amortization (3,282) (2,368) Property and equipment, net $ 44,972 $ 30,876
Schedule of Accrued Expenses And Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, December 31, (Unaudited) Accrued preclinical and clinical expenses $ 2,970 $ 1,735 Accrued professional fees 2,119 642 Accrued payroll and benefits 1,273 1,486 Accrued taxes 22 40 Accrued construction in progress 9,170 1,049 Accrued financing costs 36 131 Other current liabilities 330 26 Total $ 15,920 $ 5,109

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Operating Lease Payments	As of June 30, 2021, future minimum commitments under the Company’s operating leases were as follows (in thousands): Operating 2021 (remaining six months) $ 457 2022 1,048 2023 1,067 2024 1,087 2025 1,113 Thereafter 12,480 Future minimum operating lease payments $ 17,252 Less: Interest 9,421 Present value of lease liability $ 7,831
Schedule of Supplemental Condensed Consolidated Balance Sheet Information Related to Leases	Supplemental condensed consolidated balance sheet information related to leases is as follows: (unaudited) June 30, 2021 December 31, 2020 Operating leases: Right-of-use assets $ 7,136 $ 3,298 Current portion of lease liability 934 638 Lease liability 6,897 3,308 Total lease liability $ 7,831 $ 3,946 Weighted average remaining lease term, in years 15.0 16.4 Weighted average discount rate 9.3 % 9.4 %

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Company's Stock Option Activity	The following table summarizes the Company’s stock option activity: Stock Weighted- Weighted- Aggregate Intrinsic Value (In thousands) (1) Outstanding at December 31, 2020 853,614 $ 40.31 9.0 $ 16,804 Granted 799,950 $ 73.42 Exercised (16,874) $ 21.41 Cancelled or forfeited (46,525) $ 53.79 Outstanding at June 30, 2021 1,590,165 $ 56.77 9.0 $ 22,838 Exercisable at June 30, 2021 253,189 $ 29.73 6.9 $ 9,690 (1) Aggregate intrinsic value represents the difference between the closing stock price of our common stock on June 30, 2021 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	The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards in the condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (unaudited) (unaudited) Research and development $ 1,084 $ 181 $ 1,600 $ 370 General and administrative 2,625 626 4,240 976 Total stock-based compensation $ 3,709 $ 807 $ 5,840 $ 1,346 As of June 30, 2021, 98,800 RSAs were outstanding. The fair value of each restricted stock was $78.89 reflecting the closing price of our common stock on the grant date. The Company recorded stock-based compensation expense related to RSAs of $486 thousand and $668 thousand for the three and six months ended June 30, 2021 and zero for the three and six months ended June 30, 2020, respectively, within general and administrative expenses in the accompanying condensed consolidated statements of operations (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (unaudited) (unaudited) General and administrative $ 486 $ — $ 668 $ — Total stock-based compensation $ 486 $ — $ 668 $ —
Fair Value of Stock Options, Valuation Assumptions	The fair value of options was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions for the three and six months ended June 30, 2021 and 2020: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Expected stock price volatility 72 % 76 % 72 % 75 % Expected term of the award (years) 6.10 6.18 6.18 6.20 Risk-free interest rate 1.05 % 0.41 % 1.02 % 0.78 % Weighted average exercise price $ 66.58 $ 45.07 $ 73.42 $ 48.09 Forfeiture rate — % 6.42 % — % 6.42 %
Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity	The following table summarizes the Company’s RSA activity: Number of Shares Weighted Average Non-vested RSAs as of December 31, 2020 — $ — Granted 98,800 $ 78.89 Vested — $ — Forfeited — $ — Non-vested RSAs as of June 30, 2021 98,800 $ 78.89

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Accumulated deficit	$ 103,389	$ 71,214
Cash, cash equivalents and short-term investments	$ 367,700

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segment	Jun. 30, 2020USD ($)
Significant Accounting Policies [Line Items]
Number of operating segment | segment			1
Equipment
Significant Accounting Policies [Line Items]
Recognized impairment losses for long lived assets | $	$ 0	$ 0	$ 0	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Detail)	6 Months Ended
	Jun. 30, 2021
Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	7 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Detail) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Common share equivalents outstanding, excluded from the calculation of diluted net loss per common share	1,688,965	831,110

Net Loss Per Share Attributab_4

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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss per common share	$ (16,363)	$ (15,812)	$ (6,833)	$ (5,341)	$ (32,174)	$ (12,174)
Denominator:
Weighted-average common shares outstanding: basic	22,204,659		18,383,941		21,731,711	17,871,648
Weighted-average common shares outstanding: diluted	22,204,659		18,383,941		21,731,711	17,871,648
Net loss per common share: basic (in dollars per share)	$ (0.74)		$ (0.37)		$ (1.48)	$ (0.68)
Net loss per common share: diluted (in dollars per share)	$ (0.74)		$ (0.37)		$ (1.48)	$ (0.68)

Fair Value Instruments - Summar

Fair Value Instruments - Summary of Cash, Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 329,527	$ 268,269
Gross Unrealized Gains	4	7
Gross Unrealized Losses	(28)
Amortized Cost	389,165	271,255
Aggregate fair value, total	389,141	271,262
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate fair value, total	329,527	268,269
Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate fair value, total	38,203	2,993
Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate fair value, total	21,411	0
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	329,527	268,269
Aggregate Fair Value	329,527	268,269
Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	329,527	268,269
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	59,638	2,986
Gross Unrealized Gains	4	7
Gross Unrealized Losses	(28)
Aggregate Fair Value	59,614	2,993
Level 2 | Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	$ 38,203	2,993
Debt securities, available-for-sale, term	1 year
Level 2 | Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	$ 21,411	0
Debt securities, available-for-sale, term	2 years
Money market instruments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 329,527
Aggregate Fair Value	329,527
Money market instruments | Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	329,527
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	17,483
Gross Unrealized Gains	3
Aggregate Fair Value	17,486
Commercial paper | Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	17,486
Commercial paper | Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	0
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	30,588
Gross Unrealized Gains	1
Gross Unrealized Losses	(22)
Aggregate Fair Value	30,567
Corporate bonds | Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	18,209
Corporate bonds | Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	12,358
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	11,567
Gross Unrealized Losses	(6)
Aggregate Fair Value	11,561
U.S. government agency securities | Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	2,508
U.S. government agency securities | Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value	$ 9,053
Cash and cash equivalents | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		268,269
Aggregate Fair Value		268,269
Cash and cash equivalents | Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		268,269
Certificates of deposit | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		2,986
Gross Unrealized Gains		7
Aggregate Fair Value		2,993
Certificates of deposit | Level 2 | Short-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value		2,993
Certificates of deposit | Level 2 | Long-term Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Fair Value		$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 48,254	$ 33,244
Accumulated depreciation and amortization	(3,282)	(2,368)
Property and equipment, net	44,972	30,876
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	36,180	23,031
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	5,725	4,631
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	891	870
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	82	82
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,376	$ 4,630

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 475	$ 394	$ 914	$ 729

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Expenses And Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued preclinical and clinical expenses	$ 2,970	$ 1,735
Accrued professional fees	2,119	642
Accrued payroll and benefits	1,273	1,486
Accrued taxes	22	40
Accrued construction in progress	9,170	1,049
Accrued financing costs	36	131
Other current liabilities	330	26
Total	$ 15,920	$ 5,109

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) ft² in Thousands, $ in Thousands	Oct. 15, 2020USD ($)	Jun. 30, 2021USD ($)ft²	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)ft²	Jun. 30, 2020USD ($)	Oct. 05, 2020USD ($)	Jan. 21, 2020USD ($)
Operating Leased Assets [Line Items]
Cash contribution						$ 2,400	$ 2,400
Purchase price of potential purchase	$ 9,400
Finance lease, liability						10,000
Construction in progress, gross						$ 10,000
Escrow deposit	$ 1,500
Lessor, operating lease, liability, annual lease payments				$ 82
Cumulative escalation clause				0.10
Cumulative escalation clause, term				5 years
Operating lease costs		$ 278	$ 145	$ 497	$ 310
Variable lease costs		81	15	118	28
Clinical Supply Agreements
Operating Leased Assets [Line Items]
Estimated remaining commitment		3,800		3,800
Project management service fee		718	330	2,500	964
Other Contractual Obligations
Operating Leased Assets [Line Items]
Estimated remaining commitment		4,000		4,000
Project management service fee		974	$ 489	2,300	$ 489
ASTRA Facility
Operating Leased Assets [Line Items]
Estimated remaining commitment		$ 38,000		$ 38,000
Cost of work, percentage		0.0175		0.0175
2016 Lease Agreement
Operating Leased Assets [Line Items]
Additional area of real estate property leased | ft²		41		41

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Operating Lease Payments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
2021 (remaining nine months)	$ 457
2022	1,048
2023	1,067
2024	1,087
2025	1,113
Thereafter	12,480
Future minimum operating lease payments	17,252
Less: Interest	9,421
Present value of lease liability	$ 7,831	$ 3,946

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Supplemental Condensed Consolidated Balance Sheet Information Related to Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Right-of-use assets	$ 7,136	$ 3,298
Current portion of lease liability	934	638
Lease liability	6,897	3,308
Present value of lease liability	$ 7,831	$ 3,946
Weighted average remaining lease term, in years	15 years	16 years 4 months 24 days
Weighted average discount rate	9.30%	9.40%

Capitalization - Additional Inf

Capitalization - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 01, 2021	May 21, 2020	Jun. 30, 2021	Dec. 31, 2020
Schedule of Capitalization, Equity [Line Items]
Offering expenses	$ 198
Common stock, par value (in dollars per share)			$ 0.00001	$ 0.00001
Public Offering
Schedule of Capitalization, Equity [Line Items]
Issuance of common stock, net, (in shares)	2,211,538	2,275,000
Shares issued, price per share (in dollars per share)	$ 65	$ 55
Proceeds from initial offering of shares	$ 134,900	$ 117,200
Underwriting discounts and commissions	$ 8,600	7,500
Offering expenses		$ 463
ATM Program
Schedule of Capitalization, Equity [Line Items]
Sale of stock, number of shares issued in transaction			262,500
Sale of stock, price per share			$ 66.50
Sale of stock, consideration received on transaction			$ 17,500
Sale of stock, remaining available issuance amount			$ 132,500
Over-Allotment Option
Schedule of Capitalization, Equity [Line Items]
Issuance of common stock, net, (in shares)	288,461
Stock Sale Agreement | Placement Shares
Schedule of Capitalization, Equity [Line Items]
Offering expenses				$ 172
Common stock, par value (in dollars per share)				$ 0.0001
Sale of stock, aggregate offering price				$ 150,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option expiration period			10 years
Stock options granted (in shares)	297,500	315,400	799,950	544,400
Intrinsic value of options exercised	$ 808,000	$ 656,000	$ 872,000	$ 1,200,000
Share-based payment arrangement, amount capitalized	$ 66,000	$ 0	103,000	0
Stock-based compensation expense			$ 5,840,000	$ 1,346,000
Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for grant	1,626,006		1,626,006
Share-based Payment Arrangement, Option
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 (in dollars per share)	$ 42.53	$ 29.78	$ 47.25	$ 31.71
Unrecognized stock-based compensation expense	$ 49,000,000		$ 49,000,000
Estimated weighted average period			3 years 4 months 24 days
Stock-based compensation expense	$ 3,709,000	$ 807,000	$ 5,800,000	$ 1,300,000
Non-Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period			1 year
Non-Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period			4 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock award granted (in shares)	0	0	98,800	0
Restricted stock award outstanding (in shares)	98,800		98,800		0
Weighted-average grant-date fair value per share of options granted (in dollars per share)	$ 78.89
Stock-based compensation expense	$ 486,000	$ 0	$ 668,000	$ 0
Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period			4 years
Incentive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for grant	379,566		379,566

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Company's Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Stock Options Outstanding
Beginning balance (in shares)			853,614
Granted (in shares)	297,500	315,400	799,950	544,400
Exercised (in shares)			(16,874)
Cancelled or forfeited (in shares)			(46,525)
Ending balance (in shares)	1,590,165		1,590,165		853,614
Exercisable end of period (in shares)	253,189		253,189
Weighted- average Exercise Price
Beginning balance (in dollars per share)			$ 40.31
Granted (in dollars per share)			73.42
Exercised (in dollars per share)			21.41
Cancelled or forfeited (in dollars per share)			53.79
Ending balance (in dollars per share)	$ 56.77		56.77		$ 40.31
Exercisable end of period (in dollars per share)	$ 29.73		$ 29.73
Weighted- average Remaining Contractual Life (Years)
Weighted-average remaining contractual life (Years)			9 years		9 years
Weighted-average remaining contractual life (Years), exercisable			6 years 10 months 24 days
Aggregate Intrinsic Value
Aggregate intrinsic value, outstanding	$ 22,838		$ 22,838		$ 16,804
Exercisable at June 30, 2021	$ 9,690		$ 9,690

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Based Compensation Expense Related to Issuance of Stock Option Awards and Restricted Stock Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation			$ 5,840	$ 1,346
Share-based Payment Arrangement, Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 3,709	$ 807	5,800	1,300
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	486	0	668	0
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation			1,600	370
Research and development | Share-based Payment Arrangement, Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,084	181
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation			4,240	976
General and administrative | Share-based Payment Arrangement, Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	2,625	626
General and administrative | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 486	$ 0	$ 668	$ 0

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value of Stock Options, Valuation Assumptions (Detail) - Share-based Payment Arrangement, Option - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility	72.00%	76.00%	72.00%	75.00%
Expected term of the award (years)	6 years 1 month 6 days	6 years 2 months 4 days	6 years 2 months 4 days	6 years 2 months 12 days
Risk-free interest rate	1.05%	0.41%	1.02%	0.78%
Weighted average exercise price (in dollars per share)	$ 66.58	$ 45.07	$ 73.42	$ 48.09
Forfeiture rate	0.00%	6.42%	0.00%	6.42%

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Company's Restricted Stock Activity (Details) - Restricted Stock - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Number of Shares
Beginning balance (in shares)			0
Granted (in shares)	0	0	98,800	0
Vested (in shares)			0
Forfeited (in shares)			0
Ending balance (in shares)	98,800		98,800
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)			$ 0
Granted (in dollars per share)			78.89
Vested (in dollars per share)			0
Forfeited (in dollars per share)			0
Ending balance (in dollars per share)	$ 78.89		$ 78.89

Related Party Transactions - Ad

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