0001564590-21-010433 | 10-K | XBRL Viewer | Taysha Gene Therapies INC

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2020	Mar. 03, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	TSHA
Entity Registrant Name	Taysha Gene Therapies, Inc.
Entity Central Index Key	0001806310
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity File Number	001-39536
Entity Tax Identification Number	84-3199512
Entity Address, Address Line One	2280 Inwood Road
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75235
City Area Code	214
Local Phone Number	612-0000
Entity Common Stock, Shares Outstanding		37,761,435
Title of 12(b) Security	Common stock, par value $0.00001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Document Annual Report	true
Document Transition Report	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 0

Consolidated Balance Sheets - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 251,253,000
Prepaid expenses and other current assets	6,626,000
Deferred offering costs	0	$ 15,000
Total current assets	257,879,000	15,000
Deferred lease asset	715,000
Property and equipment, net	287,000
Total assets	258,881,000	15,000
Current liabilities
Accounts payable	1,994,000
Accrued expenses and other current liabilities	5,135,000	150,000
Total current liabilities	7,129,000	150,000
Other non-current liabilities	450,000
Total liabilities	7,579,000	150,000
Commitments and contingencies - Note 11
Stockholders' equity (deficit)
Preferred stock, $0.00001 par value per share; 10,000,000 shares authorized and no shares issued and outstanding as of December 31, 2020; no shares authorized, issued and outstanding as of December 31, 2019
Common stock, $0.00001 par value per share; 200,000,000 shares authorized and 37,761,435 issued and outstanding as of December 31, 2020; 10,895,000 shares authorized, 10,894,999 issued and outstanding as of December 31, 2019
Additional paid-in capital	312,428,000	980,000
Accumulated deficit	(61,126,000)	(1,115,000)
Total stockholders’ equity (deficit)	251,302,000	(135,000)
Total liabilities and stockholders' equity (deficit)	$ 258,881,000	$ 15,000

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Operating expenses:
Research and development	$ 987	$ 31,893
General and administrative	128	11,109
Total operating expenses	1,115	43,002
Loss from operations	(1,115)	(43,002)
Other expense:
Change in fair value of preferred stock tranche liability	0	(17,030)
Interest income		49
Interest expense		(28)
Total other expense, net		(17,009)
Net loss	$ (1,115)	$ (60,011)
Net loss per common share, basic and diluted	$ (0.12)	$ (3.40)
Weighted average common shares outstanding, basic and diluted	9,625,679	17,665,683

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	UT Southwestern License	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Common Stock UT Southwestern License	Additional Paid-in Capital	Additional Paid-in Capital UT Southwestern License	Accumulated Deficit
Balance at Sep. 20, 2019	$ 0				$ 0		$ 0		$ 0
Convertible preferred stock balance, shares at Sep. 20, 2019			0	0
Convertible preferred stock balance at Sep. 20, 2019			$ 0	$ 0
Balance, shares at Sep. 20, 2019					0
Issuance of Founders Shares, shares					8,715,999
Issuance of shares of common stock		$ 980						$ 980
Issuance of shares of common stock, shares						2,179,000
Net loss	(1,115)								(1,115)
Balance at Dec. 31, 2019	$ (135)						980		(1,115)
Balance, shares at Dec. 31, 2019	10,894,999				10,894,999
Issuance of convertible preferred stock			$ 28,345	$ 95,815
Issuance of convertible preferred stock, shares			10,000,000	5,647,048
Reclassification of preferred stock tranche liability upon issuance of Series A milestone shares			$ 18,080
Conversion of Series A and Series B convertible preferred stock to common stock			$ (46,425)	$ (95,815)
Conversion of Series A and Series B convertible preferred stock to common stock, shares			(10,000,000)	(5,647,048)
Conversion of Series A and Series B convertible preferred stock to common stock	$ 142,240						142,240
Conversion of convertible to common stock, shares					17,047,378
Issuance of shares of common stock	165,854						165,854
Issuance of shares of common stock, shares					9,050,000
Issuance of restricted stock award, shares					769,058
Stock-based compensation	3,354						3,354
Net loss	(60,011)								(60,011)
Balance at Dec. 31, 2020	$ 251,302						$ 312,428		$ (61,126)
Balance, shares at Dec. 31, 2020	37,761,435				37,761,435

Consolidated Statements of Cash Flows - USD ($)	3 Months Ended	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (1,115,000)	$ (60,011,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	0	9,000
Change in fair value of preferred stock tranche liability	0	17,030,000
Research and development license expense	980,000	9,000,000
Stock-based compensation	0	3,354,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	0	(6,585,000)
Accounts payable	0	1,961,000
Accrued expenses and other liabilities	135,000	4,513,000
Net cash used in operating activities	0	(30,729,000)
Cash flows from investing activities
Purchase of research and development licenses	0	(9,000,000)
Purchase of property and equipment	0	(82,000)
Net cash used in investing activities	0	(9,082,000)
Cash flows from financing activities
Proceeds from issuance of common stock in initial public offering, net of underwriting discounts and commission and other offering costs	0	165,854,000
Proceeds from notes payable to related party	0	1,673,000
Repayment of notes payable to related party	0	(1,673,000)
Net cash provided by financing activities	0	291,064,000
Net increase in cash and cash equivalents	0	251,253,000
Cash at the beginning of the period	0	0
Cash at the end of the period	0	251,253,000
Supplemental disclosure of cash flow information:
Cash paid for interest	0	28,000
Supplemental disclosure of noncash investing and financing activities:
Property and equipment in accounts payable and accrued expenses	0	214,000
Reclassification of preferred stock tranche liability upon share issuance	0	18,080,000
Allocation of preferred stock tranche liability	0	1,050,000
Conversion of Series A and Series B convertible preferred stock to common stock	0	142,240,000
Deferred offering costs not yet paid	15,000
Series A Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuances of convertible preferred stock, net of issuance costs	0	29,395,000
Series B Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuances of convertible preferred stock, net of issuance costs	$ 0	$ 95,815,000

Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Significant Accounting Policies

Note 2—Significant Accounting Policies

Basis of Presentation

The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented.

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Taysha and its inactive wholly owned U.S. subsidiaries that were incorporated during 2020. All intercompany transactions and balances have been eliminated in consolidation.

Emerging Growth Company

From time to time, new accounting pronouncements are issued by FASB, or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended, the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. The most significant estimates and assumptions in the Company’s financial statements relate to the determination of the fair value of the common stock prior to the IPO (as an input into stock-based compensation), estimating preclinical manufacturing accruals and accrued or prepaid research and development expenses, and the valuation of the preferred stock tranche liability. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.

Risks and Uncertainties

The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, development by the Company or its competitors of technological innovations, risks of failure of clinical studies, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and ability to transition from preclinical manufacturing to commercial production of products.

The Company’s product candidates require approvals from the FDA and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.

Segments

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as a single operating segment, which is the business of developing AAV-based gene therapies for the treatment of rare monogenic diseases of the CNS.

As of December 31, 2020 and 2019, the Company did not have assets located outside of the United States.

Cash and Cash Equivalents

Cash and cash equivalents consist of funds held in a standard checking account and a standard savings account. The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. As of December 31, 2020 and 2019, respectively, the Company had no cash equivalents.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash and cash equivalents. Periodically, the Company may maintain deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality. The Company has not experienced any losses on these deposits.

Fair Value of Financial Instruments

The Company’s financial assets and liabilities are accounted for in accordance with ASC 820, Fair Value Measurements and Disclosures which defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels:

Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities.

Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life.

Level 3—Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgement. Accordingly, the degree of judgement exercised by the Company in determining fair value is greatest for instruments categorized as 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.

The carrying values reported in the Company’s consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities are reasonable estimates of their fair values due to the short-term nature of these items.

Deferred Offering Costs

The Company capitalizes certain legal, professional, accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of additional paid-in capital generated as a result of an equity financing. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations. As of December 31, 2020 and 2019, there was $0 and $15,000, respectively, of deferred offering costs capitalized on the consolidated balance sheets. The $15,000 capitalized as of December 31, 2019 related to the Company’s Series A convertible preferred stock financing that closed in March 2020 (see Note 7).

Deferred offering costs, consisting of legal, accounting, and filing fees directly relating to the IPO and the Company’s Series A and Series B preferred stock financings, were capitalized and offset against the related proceeds upon the completion of the offerings in 2020. Upon completion of the IPO in September 2020, approximately $2.5 million of deferred offering costs were offset against the IPO proceeds in additional paid-in capital.

Property and Equipment, net

Property and equipment are stated at cost less accumulated depreciation and consist solely of computer equipment and laboratory equipment. Depreciation expense is recognized using the straight-line method over its estimated useful life of three to five years.

Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of Long-Lived Assets

The Company evaluates its long-lived assets, which consist of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment losses recognized during the year ended December 31, 2020 and the period from Inception to December 31, 2019.

Convertible Preferred Stock

The Company recorded shares of its convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The Company applied the guidance in ASC 480-10-S99-3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities and therefore classified the Series A convertible preferred stock as mezzanine equity. The convertible preferred stock was recorded outside of stockholders’ deficit because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets (a “Deemed Liquidation Event”), the convertible preferred stock would become redeemable at the option of the holders. In the event of a change of control of the Company, proceeds received from the sale of such shares would have been distributed in accordance with the liquidation preferences set forth in the Company’s Amended and Restated Certificate of Incorporation. The Company determined not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur. All shares of the Company’s previously issued and outstanding convertible preferred stock were converted into shares of common stock upon the closing of the IPO (see Note 7).

Preferred Stock Tranche Liability

The Company determined that its obligation to issue, and the Company’s investors’ right to purchase, additional shares of Series A convertible preferred stock pursuant to the milestone closings (see Note 7) represented a freestanding financial instrument (the “tranche liability”). The tranche liability was initially recorded at fair value. The proceeds from the sale of the convertible preferred stock were first allocated to the fair value of the tranche liability with the remaining proceeds from the sale of the convertible preferred stock allocated to the Series A convertible preferred stock. The tranche liability was remeasured at each reporting period and upon the exercise or expiration of the obligation, with gains and losses arising from subsequent changes in its fair value recognized in other expense in the consolidated statements of operations. At the time of the exercise or expiration of the tranche liability, any remaining value of the tranche liability was reclassified to convertible preferred stock on the consolidated balance sheets.

Research and Development

The Company has entered into research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the consolidated balance sheets as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs.

Research and development costs primarily consist of payroll, stock-based compensation, certain manufacturing costs, laboratory costs and other supplies, and the cost to acquire licenses.

Costs incurred in obtaining technology licenses through asset acquisitions are charged to research and development expense if the licensed technology has not reached technological feasibility and has no alternative future use.

Stock-Based Compensation

The Company accounts for all stock-based payments to employees and non-employees, including grants of stock options, restricted stock awards, or RSAs, and restricted stock units, or RSUs, based on their respective grant date fair values. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, which is affected principally by the estimated fair value of shares of the Company’s common stock and requires management to make a number of other assumptions, including the expected life of the option, the volatility of the underlying shares, the risk-free interest rate and expected dividends. Expected volatility is based on the historical share volatility of a set of comparable publicly traded companies over a period of time equal to the expected term of the options. Due to the lack of historical exercise history, the expected term of the Company’s stock options is determined using the “simplified” method. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

Prior to September 23, 2020, the fair value of common stock underlying the Company’s stock options, RSAs and RSUs was estimated by the Company’s board of directors considering, among other things, contemporaneous valuations of the Company’s common stock prepared by unrelated third-party valuation firms. After the IPO, the fair value of common stock is based on the closing price of the Company’s common stock on the Nasdaq Global Select Market as reported on the date of the grant.

The RSAs and RSUs are valued based on the fair value of the Company’s common stock on the date of grant. The Company expenses stock-based compensation related to stock options, RSAs and RSUs over the requisite service period using the straight-line method. All stock-based compensation costs are recorded in research and development expense or general and administrative expense in the consolidated statements of operations based upon the respective employee’s roles within the Company. Forfeitures are recorded as they occur.

Income Taxes

Income taxes are recorded in accordance with ASC 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse, and net operating loss (“NOL”) carryforwards and research and development tax credit (“R&D Credit”) carryforwards. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has recorded a full valuation allowance to reduce its net deferred income tax assets to zero. In the event the Company were to determine that it would be able to realize some or all its deferred income tax assets in the future, an adjustment to the deferred income tax asset valuation allowance would increase income in the period such determination was made.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. At December 31, 2019, the Company had no liability for income tax associated with uncertain tax positions. During the year ended December 31, 2020, the Company recorded gross unrecognized tax benefits that were not significant. The unrecognized tax benefits, if recognized, would not affect the effective income tax rate due to the valuation allowance that currently offsets deferred tax assets. The Company does not expect the unrecognized tax benefits to change significantly over the next 12 months. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred for the year ended December 31, 2020 or for the period from Inception to December 31, 2019.

Comprehensive Loss

Comprehensive loss is equal to net loss as presented in the accompanying consolidated statements of operations, as the Company did not have any other comprehensive income or loss for the periods presented.

Recently Adopted Accounting Pronouncements

In May 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (“ASC 606”). This guidance applies to any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance supersedes existing revenue recognition guidance, including most industry-specific guidance, as well as certain related guidance on accounting for contract costs. The Company early adopted ASC 606 upon its Inception. As the Company does not have any contracts with customers, the adoption of this guidance did not have any impact on the Company’s consolidated financial statements.

In June 2018, the FASB issued Accounting Standards Update (“ASU”) No. 2018-07, Compensation – Stock Compensation (Topic 718) (“ASU 2018-07”). This update is intended to reduce cost and complexity and to improve financial reporting for share-based payments issued to non-employees (for example, service providers, external legal counsel, suppliers, etc.). The ASU expands the scope of Topic 718, Compensation—Stock Compensation, which currently only includes share-based payments issued to employees, to also include share-based payments issued to non-employees for goods and services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. The Company early adopted ASU 2018-07 upon its Inception. The adoption of this ASU did not have a material effect on the Company’s consolidated financial statements at Inception. The Company applied this accounting pronouncement to the issuance of shares to the Board of Regents of the University of Texas System (see Note 5).

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (ASC Topic 820) (“ASU 2018-13”), which modifies, removes and adds certain disclosure requirements on fair value measurements based on the FASB Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements. The amendments on changes in unrealized gains and losses, the range and weighted-average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. The Company adopted ASU 2018-13 as of January 1, 2020 for the annual period. The adoption of the guidance did not have a material impact on the Company’s consolidated financial statements.

In November 2018, the FASB issued ASU No. 2018-18 – Collaborative Arrangements, which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. The Company early adopted this standard as of January 1, 2020 for the annual period and it will be applied to interim periods after December 31, 2020. This ASU requires retrospective adoption to the date the Company adopted ASC 606, which was upon its Inception, by recognizing a cumulative-effect adjustment to the opening balance of retained earnings of the earliest annual period presented. As the Company does not have any contracts with customers or collaborative arrangements, the adoption of this guidance did not have any impact on the Company’s consolidated financial statements.

Recently Issued Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as amended, with guidance regarding the accounting for and disclosure of leases. This update requires lessees to recognize the liabilities related to all leases, including operating leases, with a term greater than 12 months on the balance sheets. This update also requires lessees and lessors to disclose key information about their leasing transactions. This guidance will become effective for the Company for annual reporting periods beginning after December 15, 2021 and interim periods within fiscal years beginning after December 15, 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify various aspects related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. This guidance is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements.

Research, Collaboration, Grant and License Agreements

12 Months Ended

Dec. 31, 2020

Research Collaboration And License Agreements [Abstract]

Research, Collaboration, Grant and License Agreements

Note 5—Research, Collaboration, Grant and License Agreements

UT Southwestern Agreement

On November 19, 2019, the Company entered into a research, collaboration and license agreement (“UT Southwestern Agreement”) with the Board of Regents of the University of Texas System (“UT System”) on behalf of The University of Southwestern Medical Center (“UT Southwestern”). Under the UT Southwestern Agreement, UT Southwestern is primarily responsible for preclinical development activities with respect to licensed products for use in certain specified indications (up to IND-enabling studies), and the Company is responsible for all subsequent clinical development and commercialization activities with respect to the licensed products. UT Southwestern will conduct such preclinical activities for a two-year period under mutually agreed upon sponsored research agreements that were entered into beginning in April 2020. During the initial research phase, the Company has the right to expand the scope of specified indications under the UT Southwestern Agreement.

In connection with the UT Southwestern Agreement, the Company obtained an exclusive, worldwide, royalty-free license under certain patent rights of UT Southwestern and a non-exclusive, worldwide, royalty-free license under certain know-how of UT Southwestern, in each case to make, have made, use, sell, offer for sale and import licensed products for use in certain specified indications. Additionally, the Company obtained a non-exclusive, worldwide, royalty-free license under certain patents and know-how of UT Southwestern for use in all human uses, with a right of first refusal to obtain an exclusive license under certain of such patent rights and an option to negotiate an exclusive license under other of such patent rights. The Company is required to use commercially reasonable efforts to develop, obtain regulatory approval for, and commercialize at least one licensed product.

On April 2, 2020, the Company amended the UT Southwestern Agreement to include the addition of another licensed product and certain indications, and a right of first refusal to the Company over certain patient dosing patents. No additional consideration was transferred in connection with this amendment.

The UT Southwestern Agreement expires on a country-by-country and licensed product-by-licensed product basis upon the expiration of the last valid claim of a licensed patent in such country for such licensed product. After the initial research term, the Company may terminate the agreement, on an indication-by-indication and licensed product-by-licensed product basis, at any time upon specified written notice to UT Southwestern. Either party may terminate the agreement upon an uncured material breach of the agreement or insolvency of the other party.

In November 2019, as partial consideration for the license rights granted under the UT Southwestern Agreement, the Company issued 2,179,000 shares of its common stock, or 20% of its then outstanding fully-diluted common stock, to UT Southwestern. As additional consideration, UT Southwestern was entitled to receive additional shares if their holdings fell below 10% on a fully-diluted basis before or as a result of the completion of a qualified financing. In March 2020, following the initial closing of the Series A convertible preferred stock agreement, which met the definition of such qualified financing, the anti-dilution feature expired and no additional shares were issued. The Company does not have any future milestone or royalty obligations to UT Southwestern under the UT Southwestern Agreement other than costs related to maintenance of patents.

The Company also had the right of first refusal for any shares that UT Southwestern wishes to sell that officially expired upon the closing of the IPO. UT Southwestern did not sell any shares before the closing of the IPO.

The fair value of the shares issued was determined to be $980,000 which was recorded as an increase to common stock and additional paid-in capital and a corresponding research and development expense during the period from Inception through December 31, 2019. The cost to acquire this license is recorded within research and development expense in the consolidated statements of operations because the license relates to specific preclinical research and development activities that do not have an alternative future use. As the acquisition of the license was settled through the issuance of shares of the Company’s common stock, this transaction fell within the scope of ASC Topic 718 since equity was issued in exchange for goods (the license). Specifically, the Company recorded the cost of the license as a non-employee share based payment, measured at the grant date fair value of the common stock of $0.45 per share. The common shares were equity-classified. The anti-dilution provision was concluded to represent a performance condition tied to a future liquidity event, which was not considered probable of occurring at December 31, 2019 since it was deemed outside of the Company’s control.

Since there was an absence of a public trading market for the Company’s common stock during the period from Inception to December 31, 2019, the valuation of the common stock issued to UT System was performed using methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants Audit and Accounting Practice Aid Series: Valuation of Privately-Held-Company Equity Securities Issued as Compensation. The estimated fair value of the Company’s common stock was determined with the assistance of a third-party specialist using an Option-Pricing Method (“OPM”). Under the OPM, the Company used a backsolve method so that the enterprise value equaled the contemplated value of the Company determined by the Series A convertible preferred stock financing transaction which initially closed on March 4, 2020 (see Note 7), and giving consideration to any value-generating events that may have occurred between March 4, 2020 and the date the common shares were issued to UT System on November 19, 2019. A discount for lack of marketability (“DLOM”) of 20% was applied to derive the valuation price. The DLOM used was derived from the then-current estimates of the time to a liquidity event made by the Company’s board of directors, with input from the Company’s senior management. The estimates are based, in part, on subjective assumptions.

Queen’s Agreement

In late December 2019, the Company entered into a research grant agreement (“RGA”) with Queen’s University at Kingston (“Queen’s”), for certain research and development activities related to the generation of AAV9 vector. The Company committed to fund $3.8 million under the RGA with Queen’s. The Company agreed to issue Queen’s a promise-to-pay note whereby any amounts paid directly by Queen’s for the manufacture of the vector for use in the funded research activities, to the extent such amounts have not already been funded by the Company to Queen’s, become a loan obligation for the Company (the “Note”), subject to an interest rate of 6%. Any amounts outstanding under the Note were required to be repaid, along with any accrued interest, by or before June 30, 2020. In the event of default, any amount outstanding shall be deemed immediately payable by RA Session II, the Company’s President and Chief Executive Officer, as a personal guarantor (see Note 6). For the period from Inception through December 31, 2019, the Company did not incur any expenses associated with the Queen’s RGA, and no amounts were due or outstanding under the Note as of December 31, 2019. For the year ended December 31, 2020, the Company paid all expenses associated with the Queen’s RGA, thus no amounts were due or outstanding under the Note as of December 31, 2020, and the promise-to-pay has therefore expired.

On February 21, 2020, the Company entered into a license agreement with Queen’s (the “Queen’s Agreement”) to obtain the exclusive perpetual, royalty-bearing license, with the right to sublicense through multiple tiers, under certain patent rights and know-how of Queen’s, including certain improvements to such patent rights and know-how, to develop products in any field which use one or more valid claims of the patents licensed under the Queen’s Agreement (the “Licensed Patents”), or the technology, information and intellectual property related to the patents licensed under the Queen’s Agreement (together with the Licensed Patents, the “Licensed Products”), and to make, have made, use, sell, offer for sale, import and export Licensed Products and otherwise exploit such patents and know-how for use in certain specified indications. In exchange for the rights granted to the Company, the Company made a cash payment of $3.0 million in April 2020 which is recorded in research and development expenses in the consolidated statements of operations and included as an investing outflow in the consolidated statements of cash flows since the acquired license does not have an alternative future use. The Company is obligated to make aggregate cash payments of up to $10.0 million upon the completion of a combination of regulatory milestones and up to $10.0 million upon the completion of a combination of commercial milestones. In further consideration of the rights granted, beginning with the Company’s first commercial sale of the Licensed Products, the Company will also pay an annual earned royalty in the low single digits on net sales of Licensed Products, subject to certain customary reductions, and a percentage of non-royalty sublicensing revenue ranging in the low double digits. Royalties are payable, on a Licensed Products-by-Licensed Products and a country-by-country basis, until expiration of the last valid claim of a Licensed Patent covering such Licensed Products in such country and the expiration of any regulatory exclusivity for such Licensed Products in such country.

Abeona CLN1 Agreements

In August 2020, the Company entered into license and inventory purchase agreements with Abeona Therapeutics Inc. (“Abeona”) for worldwide exclusive rights to certain intellectual property rights and know-how relating to the research, development and manufacture of ABO-202, an AAV-based gene therapy for CLN1 disease (one of the forms of Batten disease). Under the terms of the agreements, the Company made initial cash payments to Abeona of $3.0 million for the upfront license fee and $4.0 million for purchase of clinical materials and reimbursement for previously incurred development costs in October 2020. In exchange for the license rights, the Company recorded an aggregate of $7.0 million within research and development expenses in the consolidated statements of operations and included the license fee of $3.0 million as an investing outflow in the consolidated statements of cash flows since the acquired license does not have an alternative future use. The Company is obligated to make up to $26.0 million in regulatory-related milestones and up to $30.0 million in sales-related milestones per licensed CLN1 product. The Company will also pay an annual earned royalty in the high single digits on net sales of any licensed CLN1 products. The license agreement expires on a country-by-country and licensed product-by-licensed product basis upon the expiration of the last royalty term of a licensed product. Either party may terminate the agreement upon an uncured material breach of the agreement or insolvency of the other party. The Company may terminate the license agreement for convenience upon specified prior written notice to Abeona.

Abeona Rett Agreement

On October 29, 2020, the Company entered into a license agreement (the “Abeona Rett Agreement”) with Abeona pursuant to which the Company obtained an exclusive, worldwide, royalty-bearing license, with the right to grant sublicenses under certain patents, know-how and materials originally developed by the University of North Carolina at Chapel Hill, the University of Edinburgh and Abeona to research, develop, manufacture, have manufactured, use, and commercialize licensed products for gene therapy and the use of related transgenes for Rett syndrome.

Subject to certain obligations of Abeona, the Company is required to use commercially reasonable efforts to develop at least one licensed product and commercialize at least one licensed product in the United States.

In connection with the Abeona Rett Agreement, the Company paid Abeona a one-time upfront license fee of $3.0 million which is recorded in research and development expenses in the consolidated statements of operations and included as an investing outflow in the consolidated statements of cash flows since the acquired license does not have an alternative future use. The Company is obligated to pay Abeona up to $26.5 million in regulatory-related milestones and up to $30.0 million in sales-related milestones per licensed Rett product and high single-digit royalties on net sales of licensed Rett products. Royalties are payable on a licensed product-by-licensed product and country-by-country basis until the latest of the expiration or revocation or complete rejection of the last licensed patent covering such licensed product in the country where the licensed product is sold, the loss of market exclusivity in such country where the product is sold, or, if no licensed product exists in such country and no market exclusivity exists in such country, ten years from first commercial sale of such licensed product in such country.

The Abeona Rett Agreement expires on a country-by-country and licensed product-by-licensed product basis upon the expiration of the last royalty term of a licensed product. Either party may terminate the agreement upon an uncured material breach of the agreement or insolvency of the other party. The Company may terminate the agreement for convenience upon specified prior written notice to Abeona.

Catalent Agreements

During October and November 2020, the Company entered into two agreements (the “Catalent Agreements”) with Catalent Maryland, Inc. (“Catalent”) to support the development and manufacturing of the Company’s gene therapies for CLN1 and Rett syndrome at Catalent’s Maryland-based gene therapy facilities. The Company engaged Catalent, which is a Contract Development and Manufacturing Organization (CDMO), to conduct services related to technology transfer, process development, analytical development, qualification, project administration and manufacture of CLN1 and Rett syndrome gene therapies suitable for use in nonclinical, United States and European Union Phase 1/2 clinical trials.

In connection with the Catalent Agreements, the Company paid Catalent an upfront project initiation fee of $2.0 million which is recorded as a prepaid expense in the consolidated balance sheets. The fee will be credited toward fees and expenses incurred under the Catalent Agreements. The Company therefore reduces the prepaid expense concurrently with expenses as they are incurred.

Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability

Note 7— Stockholders’ Equity (Deficit), Convertible Preferred Stock and Tranche Liability

At December 31, 2019, the Company was authorized to issue 10,895,000 shares of common stock with a par value of $0.00001 per share. RA Session II and one other individual were issued 8,661,524 and 54,475 shares of the Company’s common stock (“Founders Shares”), respectively, upon the formation of the Company on September 20, 2019. RA Session II and the other individual had not paid the Company for the aggregate par value, which approximated fair value at Inception, for these Founders Shares as of December 31, 2019. All amounts owed for the issuance of these Founders Shares were settled in July 2020.

On November 19, 2019, the Company issued 2,179,000 shares of the Company’s common stock to UT System in exchange for a license agreement. The fair value of the shares on the date of issuance was $980,000 in the aggregate. Except for the issuance of common stock to UT System in connection with the UT Southwestern Agreement, the Company did not grant any equity-based awards during the period from its Inception through December 31, 2019.

Authorized shares

The Company amended its certificate of incorporation on March 4, 2020, July 2, 2020 and again on July 28, 2020 such that the total number of shares of common stock authorized to be issued was increased to 32,685,000, and the total number of shares of preferred stock authorized to be issued was increased to 15,647,052, of which 10,000,000 preferred shares were designated Series A convertible preferred stock and 5,647,052 were designated Series B convertible preferred stock. On September 28, 2020, the Company amended its certificate of incorporation such that the total number of shares of common stock authorized to be issued was increased to 200,000,000, and the total number of shares of new preferred stock authorized to be issued was 10,000,000. As of December 31, 2020, no shares of preferred stock were issued or outstanding.

IPO

On September 28, 2020, the Company issued an aggregate of 7,869,566 shares of common stock in the IPO, and on September 29, 2020, the Company issued an aggregate of 1,180,434 shares of common stock upon the underwriters’ exercise in full of their option to purchase additional shares, each at the public offering price of $20.00 per share less underwriting discounts and commissions. In connection with the IPO, the Company received gross proceeds of $181.0 million, which was offset by issuance costs, including underwriters’ discounts and commissions, of approximately $15.1 million.

In connection with the closing of the IPO, 10,000,000 shares of Series A convertible preferred stock and 5,647,048 shares of Series B convertible preferred stock automatically converted into an aggregate of 17,047,378 shares of common stock with a conversion ratio of 1.0895 shares of common stock for each share of Series A and Series B convertible preferred stock then outstanding.

As a result of the IPO, the underwriters’ exercise of their option, and the conversions of the Series A and B convertible preferred stock, the Company’s total number of outstanding shares increased by 26,097,378 immediately following the closing of the IPO.

Series A and B convertible preferred stock

On March 4, 2020, the Company entered into a purchase agreement (the “Series A Purchase Agreement”) providing for a private placement of up to 10,000,000 shares of Series A convertible preferred stock at an original issuance price of $3.00 per share, subject to separate closings, including: (1) 6,000,000 shares at the initial closing on March 4, 2020, and (2) 2,000,000 shares at each of two subsequent closings triggered by the achievement of specific clinical milestones. The Series A Purchase Agreement obligated the Company to issue and sell and the Series A investors to purchase up to a total of 4,000,000 additional shares of Series A convertible preferred stock (the “Milestone Shares”) at the same price per share upon the achievement of certain defined clinical milestones (the “tranche liability”). The determination as to whether the milestone events had been met was subject to certification by the Board of Directors. Each Series A investor had the right, but not the obligation, to purchase all or any portion of the Milestone Shares at any time in its sole option and in its sole and absolute discretion, whether or not the Company had achieved the applicable clinical milestone.

On June 30, 2020, several affiliated Series A investors elected to exercise in full their options to purchase 200,000 shares, representing all of their remaining pro-rata portion of the Milestone Shares, prior to the Company’s achievement of the clinical milestones for gross proceeds of $0.6 million. The remainder of the Series A investors exercised in full their options to purchase 3,800,000 shares, representing all of their remaining pro-rata portion of the Milestone Shares, prior to the Company’s achievement of the clinical milestones, for gross proceeds of $11.4 million between July 1, 2020 and July 2, 2020. As part of this issuance, the Company issued and sold 3,266,667 shares to PBM TGT Holdings, LLC and 400,000 shares to Nolan Capital, LLC, which stockholders are controlled by certain members of the Company’s board of directors.

On July 2, 2020, the Company entered into a purchase agreement (the “Series B Purchase Agreement”), as later amended on July 28, 2020, providing for a private placement of up to 5,647,052 shares of Series B convertible preferred stock. The Company sold 5,647,048 shares of Series B convertible preferred stock at a price of $17.00 per share in multiple closings in July and August 2020 for gross proceeds of $96.0 million. The majority of investors that participated in the Series B Purchase Agreement were new investors.

As described above, in connection with the closing of the IPO, all shares of Series A and Series B convertible preferred stock were automatically converted into an aggregate of 17,047,378 shares of common stock with a conversion ratio, which was adjusted for the stock split, of 1.0895 shares of common stock for each share of Series A and Series B convertible preferred stock then outstanding.

Series A convertible preferred stock tranche liability

The Company concluded that the tranche liability met the definition of a freestanding financial instrument, as it was legally detachable and separately exercisable from the initial closing of the Series A convertible preferred stock.

The estimated fair value of the tranche liability was determined using a Monte Carlo simulation at the initial issuance date. As of March 4, 2020, the simulations occurred based on the implied aggregate equity value of the Company derived from the Series A convertible preferred stock offering price of $3.00 per share, along with, in part, the following subjective assumptions: risk-free rate of 0.59%, an expected volatility of 80%, the expected term to a liquidity event of 1 year, and a 60% probability of achieving the clinical milestones and timing thereof. Subsequently, the estimated fair value of the tranche liability was determined using a backsolve approach at June 30, 2020, immediately prior to the issuance of the Milestone Shares, which was calculated based on the aggregate equity value of the Company derived from the Series B convertible preferred stock offering price of $17.00 per share. The subsequent remeasurement also considered, in part, a risk-free rate of 0.17%, an expected volatility of 80%, and the expected term to a liquidity event of 0.5 years.

Based on the analysis, the Company recorded a preferred stock tranche liability of $1.1 million at the issue date to account for the obligation to issue the Milestone Shares at a predetermined fixed price at a future settlement date.

At June 30, 2020, ahead of the anticipated closing of the Series B Purchase Agreement for $17.00 per share that occurred on July 2, 2020, certain investors elected to exercise in full their options to their pro-rata portion of the Milestone Shares prior to the Company’s achievement of the clinical milestones and purchased 200,000 shares of Series A convertible preferred stock. The Company remeasured the fair value of the entire tranche liability at June 30, 2020 and recognized a non-cash expense of $17.0 million in the consolidated statements of operations. Between June 30, 2020 and July 2, 2020, all of the 4,000,000 Milestone Shares were issued and the related tranche liability was extinguished in its entirety, and the Company reclassified the entire tranche liability of $18.1 million to convertible preferred stock on the consolidated balance sheets.

The Company concluded that no beneficial conversion feature (“BCF”) existed as the effective conversion price of the Series A convertible preferred stock exceeded the fair value of the Company’s common stock at each of the commitment dates. Specifically, at the commitment date of June 30, 2020, when 200,000 Milestone Shares were issued, the deemed proceeds were equal to the cash proceeds received for the shares of Series A convertible preferred stock and the fair value of the tranche liability that related to the Milestone Shares, or $7.52 per share. As the effective conversion price exceeded the fair value of the Company’s common stock at the commitment date, no BCF existed.

The following table provides a reconciliation of the preferred stock tranche liability measured at fair value using Level 3 significant unobservable inputs (in thousands):

Balance at December 31, 2019	$	—
Fair value at issuance of Series A convertible preferred stock		1,050
Change in fair value		17,030
Settlement of preferred stock tranche liability due to issuance of Milestone Shares		(18,080	)
Balance at December 31, 2020	$	—

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 8—Stock-Based Compensation

On July 1, 2020, the Company’s board of directors approved the Existing Plan which permits the granting of incentive stock options, non-statutory stock options, stock appreciation rights, RSAs, RSUs and other stock-based awards to employees, directors, officers and consultants. On July 1, 2020, 3,529,412 shares of common stock were authorized for issuance under the Existing Plan. On September 16, 2020, the Company increased the number of shares of common stock authorized for issuance under the Existing Plan to 3,845,294.

On September 16, 2020, the Company’s stockholders approved the New Plan, which became effective upon the execution of the underwriting agreement in connection with the IPO. The number of shares available for future issuance under the New Plan is the sum of (1) 3,390,168 new shares of common stock, (2) 209,841 remaining shares of common stock reserved under the Existing Plan that became available for issuance upon the effectiveness of the New Plan and (3) the number of shares of common stock subject to outstanding awards under the Existing Plan when the New Plan became effective that thereafter expire or are forfeited, canceled, withheld to satisfy tax withholding or to purchase or exercise an award, repurchased by the Company or are otherwise terminated. At December 31, 2020, there were 2,941,509, shares available for future grant under the New Plan. The number of shares of common stock reserved for issuance under the New Plan will automatically increase on January 1 of each year, for a period of ten years, from January 1, 2021 continuing through January 1, 2030, by 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors.

Furthermore, on September 16, 2020, the Company’s stockholders approved the Employee Stock Purchase Plan (“ESPP”), which became effective upon the execution of the underwriting agreement in connection with the IPO. The maximum number of shares of common stock that may be issued under the ESPP will not exceed 362,000 shares of common stock, plus the number of shares of common stock that are automatically added on January 1st of each year for a period of up to ten years, commencing on the first January 1 following the IPO Date and ending on (and including) January 1, 2030, in an amount equal to the lesser of (i) one percent (1.0%) of the total number of shares of capital stock outstanding on December 31st of the preceding calendar year, and (ii) 724,000 shares of common stock. No issuances have been made under the ESPP as of December 31, 2020.

Stock Options

On July 1, 2020, options to purchase 2,896,782 shares of common stock under the Existing Plan were awarded to certain employees and consultants of the Company with an exercise price per share of $0.80, which were expected to vest over a four-year period, all of which were subsequently cancelled (the “Cancelled Options”). The grant date fair value of the Cancelled Options was $13.8 million at the original grant date. In exchange, the Company awarded 2,518,932 RSUs on September 2, 2020, which are expected to vest over a four-year term. The Company accounted for the changes in award terms as a modification in accordance with ASC 718 Compensation – Stock Compensation. The modification is accounted for as an exchange of the original award for a new award with total compensation cost equal to the grant-date fair value of the original award plus any incremental value measured on the modification date. The Company determined that there was no incremental value as the fair value of the original award immediately before the modification was greater than the fair value of the new award immediately after the modification. Accordingly, the Company will recognize the remaining compensation cost at the time of the modification of $13.2 million over the vesting period of the RSUs.

The estimated fair value of the Company’s common stock at July 1, 2020 was $5.28 per share, as determined using information derived from the issuance price of the Company’s Series B convertible preferred stock of $17.00 per share on July 2, 2020. The valuation of the common stock was determined using an option-pricing model under which shares are valued by creating a series of call options with exercise prices based on the liquidation preferences and conversion terms of each equity class, adjusted for a discount for the lack of marketability to account for a lack of access to an active public market.

The following assumptions were used to estimate the fair value of the Cancelled Options that were granted on July 1, 2020:

Risk-free interest rate	0.31	%
Expected dividend yield	—
Expected term in years	6.3
Expected volatility	80	%

During the year ended December 31, 2020, excluding the Cancelled Options, options to purchase 674,842 shares of common stock were granted with a weighted-average exercise price per share of $20.68. On September 2, 2020, options to purchase 16,342 shares of common stock under the Existing Plan were awarded to certain directors of the Company with an exercise price per share of $14.90, and on various dates beginning at the closing of the IPO through December 31, 2020, 658,500 shares of common stock under the New Plan were awarded with a weighted-average exercise price per share of $20.83. The stock options generally vest over three or four years and have a ten-year contractual term.

The following weighted-average assumptions were used to estimate the fair value of stock options, excluding the Cancelled Options, for the year ended December 31, 2020:

Risk-free interest rate	0.54	%
Expected dividend yield	—
Expected term in years	6.2
Expected volatility	77	%

The following table summarizes stock option activity, excluding the Cancelled Options, during the year ended December 31, 2020:

					Weighted
			Weighted		Average		Aggregate
			Average		Remaining		Intrinsic
	Stock		Exercise		Contractual		Value
	Options		Price		Life (in years)		(in thousands)
Outstanding at December 31, 2019		—	$	—		—	$	—
Options granted		674,842		20.68
Outstanding at December 31, 2020		674,842	$	20.68		9.8	$	3,953
Vested and expected to vest at December 31, 2020		674,842	$	20.68		9.8	$	3,953
Options exercisable at December 31, 2020		12,054	$	20.25		9.8	$	76

The aggregate intrinsic value in the above table is calculated as the difference between the fair value of the Company’s common stock as of December 31, 2020 and the exercise price of the stock options. The weighted-average grant date fair value per share for the stock option awards, excluding the Cancelled Options, granted during the year ended December 31, 2020 was $13.73. As of December 31, 2020, the total unrecognized compensation related to unvested stock option awards granted was $8.8 million, which the Company expects to recognize over a weighted-average period of approximately 3.6 years.

Restricted Stock Units

On September 2, 2020, the Company issued 331,121 RSUs to an employee under the Existing Plan; 25% of the shares of common stock underlying the RSUs vest at each anniversary over a four-year period. The RSUs are subject to a service-based vesting condition. The RSUs were also subject to a liquidity-based performance vesting condition that was met upon the closing of the IPO. The Company at any time may accelerate the vesting of the RSUs. Such shares are not accounted for as outstanding until they vest. As of December 31, 2020, the total unrecognized compensation related to unvested RSUs granted, including the remaining compensation cost associated with the RSUs granted on September 2, 2020 in exchange for the Cancelled Options, was $16.2 million which is expected to be amortized on a straight-line basis over the weighted-average remaining vesting period of approximately 2.1 years. The Company’s RSU activity for the year ended December 31, 2020 was as follows:

			Weighted
			Average
			Grant Date
	Number		Fair Value
	of Shares		per Share
Nonvested at January 1, 2020		—	$	—
Replacement restricted units granted		2,518,932		5.25
Restricted units granted		331,121		14.90
Vested		—		—
Nonvested at December 31, 2020		2,850,053	$	6.37

Restricted Stock Awards

RA Session II, the Company’s President and Chief Executive Officer, was awarded 769,058 RSAs under the Existing Plan on July 1, 2020, which are expected to vest over a three-year term, subject to continuous employment. As of December 31, 2020, the total unrecognized compensation related to unvested RSAs granted was $3.2 million which is expected to be amortized on a straight-line basis over the weighted-average remaining vesting period of approximately 2.3 years. The fair value of these RSAs at the grant date of July 1, 2020 was $5.28 per share.

The Company’s RSA activity for the year ended December 31, 2020 was as follows:

			Weighted
			Average
			Grant Date
	Number		Fair Value
	of Shares		per Share
Nonvested at December 31, 2019		—	$	—
Restricted stock granted		769,058		5.28
Vested		—		—
Nonvested at December 31, 2020		769,058	$	5.28

The following table summarizes the total stock-based compensation expense for the stock options, RSAs and RSUs recorded in the consolidated statements of operations for the year ended December 31, 2020 and for the period from Inception to December 31, 2019 (in thousands):

	For the Year Ended December 31, 2020		For the period from September 20, 2019 (date of inception) to December 31, 2019
Research and development expense	$	1,167	$	—
General and administrative expense		2,187		—
Total	$	3,354	$	—

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 10—Income Taxes

Provision for income taxes

There is no provision for income taxes because the Company has incurred operating losses and capitalized certain items for income tax purposes since its inception and maintains a full valuation allowance against its net deferred tax assets. The reported amount of income tax expense for the period differs from the amount that would result from applying the federal statutory tax rate to net loss before taxes primarily because of the change in valuation allowance.

On March 27, 2020, the CARES Act, an economic relief package in response to the COVID-19 pandemic, was signed into law. The CARES Act contains several corporate income tax provisions, including making remaining alternative minimum tax credits immediately refundable; providing a 5-year carryback of NOL carryforwards generated in tax years 2018, 2019, and 2020, and removing the 80% taxable income limitation on utilization of those NOLs if carried back to prior tax years or utilized in tax years beginning before 2021; and temporarily liberalizing the interest deductibility rules under Section 163(j) of the Tax Cuts and Jobs Act, by raising the adjusted taxable income limitation from 30% to 50% for tax years 2019 and 2020 and giving taxpayers the election of using 2019 adjusted taxable income for purposes of computing 2020 interest deductibility. The CARES Act did not have a material effect on the realizability of deferred income tax assets or tax expense in 2020.

The effective tax rate of the Company's provision (benefit) for income taxes differs from the federal statutory rate as follows:

	For the Year Ended December 31, 2020			For the Period from September 20, 2019 (date of inception) to December 31, 2019
Statutory rate		21.00	%		21.00	%
State tax		0.06	%		—
General business credits		1.06	%		—
Other permanent differences		(0.25	)%		—
Change in valuation allowance		(15.91	)%		(21.00	)%
Change in fair value of tranche liability		(5.96	)%		—
Income tax provision (benefit)		0.00	%		0.00	%

Deferred tax assets and valuation allowance

Deferred tax assets reflect the tax effects of NOLs, tax credit carryovers, and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. At December 31, 2020 and December 31, 2019, the significant components of the Company’s net deferred tax asset are as follows (in thousands):

	For the Year Ended December 31, 2020			For the Period from September 20, 2019 (date of inception) to December 31, 2019
Net operating loss carryforwards	$	5,810		$	—
Tax credit carryforwards		672			—
Accruals and reserves		334			—
Other		21			—
Intangibles		2,390			206
Organizational and start-up costs		—			28
Non-qualified stock options		555			—
Total deferred tax assets		9,782			234
Valuation allowance		(9,782	)		(234	)
Deferred tax asset, net of allowance	$	—		$	—

There are no deferred tax liabilities as of December 31, 2020 and December 31, 2019, respectively. The valuation allowance is equal to the total deferred tax asset amounts as of December 31, 2020 and December 31, 2019 as there are no deferred tax liabilities in the respective periods. ASC 740 requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is "more likely than not." Realization of the future tax benefits is dependent on the Company's ability to generate sufficient taxable income within the carryforward period. Because of the Company's recent history of operating losses, management believes that recognition of the deferred tax assets arising from the above-mentioned future tax benefits is currently not likely to be realized and, accordingly, has provided a valuation allowance.

The valuation allowance increased by $9.5 million during the year ended December 31, 2020 and by $0.2 million for the period from Inception to December 31, 2019.

There were no net operating loss and tax credit carryforwards as of December 31, 2019. As of December 31, 2020, there were net federal operating losses of $27.7 million, federal tax credit carryforward of $0.9 million, and state tax credit carryforward of less than $0.1 million. The net operating losses and state tax credit carryforward do not expire. The federal tax credit carryforward will expire in 2040. The Company files federal and state income tax returns and, in the normal course of business, the Company is subject to examination by these taxing authorities.

Pursuant to Section 382 of the Internal Revenue Code, certain substantial changes in the Company's ownership may result in a limitation on the amount of NOL carryforwards and tax credit carryforwards that may be used in future years. Utilization of the NOL and tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company has not completed a study to assess whether an ownership change has occurred, or whether there have been multiple ownership changes since its formation. There could also be additional ownership changes in the future which may result in additional limitations on the utilization of NOL carryforwards and credits.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Taysha and its inactive wholly owned U.S. subsidiaries that were incorporated during 2020. All intercompany transactions and balances have been eliminated in consolidation.
Emerging Growth Company	Emerging Growth Company From time to time, new accounting pronouncements are issued by FASB, or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended, the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. The most significant estimates and assumptions in the Company’s financial statements relate to the determination of the fair value of the common stock prior to the IPO (as an input into stock-based compensation), estimating preclinical manufacturing accruals and accrued or prepaid research and development expenses, and the valuation of the preferred stock tranche liability. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.
Risks and Uncertainties	Risks and Uncertainties The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, development by the Company or its competitors of technological innovations, risks of failure of clinical studies, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and ability to transition from preclinical manufacturing to commercial production of products. The Company’s product candidates require approvals from the FDA and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as a single operating segment, which is the business of developing AAV-based gene therapies for the treatment of rare monogenic diseases of the CNS. As of December 31, 2020 and 2019, the Company did not have assets located outside of the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of funds held in a standard checking account and a standard savings account. The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. As of December 31, 2020 and 2019, respectively, the Company had no cash equivalents.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash and cash equivalents. Periodically, the Company may maintain deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality. The Company has not experienced any losses on these deposits.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial assets and liabilities are accounted for in accordance with ASC 820, Fair Value Measurements and Disclosures which defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels: Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities. Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life. Level 3—Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgement. Accordingly, the degree of judgement exercised by the Company in determining fair value is greatest for instruments categorized as 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. The carrying values reported in the Company’s consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities are reasonable estimates of their fair values due to the short-term nature of these items.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes certain legal, professional, accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of additional paid-in capital generated as a result of an equity financing. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations. As of December 31, 2020 and 2019, there was $0 and $15,000, respectively, of deferred offering costs capitalized on the consolidated balance sheets. The $15,000 capitalized as of December 31, 2019 related to the Company’s Series A convertible preferred stock financing that closed in March 2020 (see Note 7). Deferred offering costs, consisting of legal, accounting, and filing fees directly relating to the IPO and the Company’s Series A and Series B preferred stock financings, were capitalized and offset against the related proceeds upon the completion of the offerings in 2020. Upon completion of the IPO in September 2020, approximately $2.5 million of deferred offering costs were offset against the IPO proceeds in additional paid-in capital.
Property and Equipment, net	Property and Equipment, net Property and equipment are stated at cost less accumulated depreciation and consist solely of computer equipment and laboratory equipment. Depreciation expense is recognized using the straight-line method over its estimated useful life of three to five years. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets, which consist of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment losses recognized during the year ended December 31, 2020 and the period from Inception to December 31, 2019.
Convertible Preferred Stock	Convertible Preferred Stock The Company recorded shares of its convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The Company applied the guidance in ASC 480-10-S99-3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities and therefore classified the Series A convertible preferred stock as mezzanine equity. The convertible preferred stock was recorded outside of stockholders’ deficit because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets (a “Deemed Liquidation Event”), the convertible preferred stock would become redeemable at the option of the holders. In the event of a change of control of the Company, proceeds received from the sale of such shares would have been distributed in accordance with the liquidation preferences set forth in the Company’s Amended and Restated Certificate of Incorporation. The Company determined not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur. All shares of the Company’s previously issued and outstanding convertible preferred stock were converted into shares of common stock upon the closing of the IPO (see Note 7).
Preferred Stock Tranche Liability	Preferred Stock Tranche Liability The Company determined that its obligation to issue, and the Company’s investors’ right to purchase, additional shares of Series A convertible preferred stock pursuant to the milestone closings (see Note 7) represented a freestanding financial instrument (the “tranche liability”). The tranche liability was initially recorded at fair value. The proceeds from the sale of the convertible preferred stock were first allocated to the fair value of the tranche liability with the remaining proceeds from the sale of the convertible preferred stock allocated to the Series A convertible preferred stock. The tranche liability was remeasured at each reporting period and upon the exercise or expiration of the obligation, with gains and losses arising from subsequent changes in its fair value recognized in other expense in the consolidated statements of operations. At the time of the exercise or expiration of the tranche liability, any remaining value of the tranche liability was reclassified to convertible preferred stock on the consolidated balance sheets.
Research and Development	Research and Development The Company has entered into research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the consolidated balance sheets as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Research and development costs primarily consist of payroll, stock-based compensation, certain manufacturing costs, laboratory costs and other supplies, and the cost to acquire licenses. Costs incurred in obtaining technology licenses through asset acquisitions are charged to research and development expense if the licensed technology has not reached technological feasibility and has no alternative future use.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for all stock-based payments to employees and non-employees, including grants of stock options, restricted stock awards, or RSAs, and restricted stock units, or RSUs, based on their respective grant date fair values. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, which is affected principally by the estimated fair value of shares of the Company’s common stock and requires management to make a number of other assumptions, including the expected life of the option, the volatility of the underlying shares, the risk-free interest rate and expected dividends. Expected volatility is based on the historical share volatility of a set of comparable publicly traded companies over a period of time equal to the expected term of the options. Due to the lack of historical exercise history, the expected term of the Company’s stock options is determined using the “simplified” method. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. Prior to September 23, 2020, the fair value of common stock underlying the Company’s stock options, RSAs and RSUs was estimated by the Company’s board of directors considering, among other things, contemporaneous valuations of the Company’s common stock prepared by unrelated third-party valuation firms. After the IPO, the fair value of common stock is based on the closing price of the Company’s common stock on the Nasdaq Global Select Market as reported on the date of the grant. The RSAs and RSUs are valued based on the fair value of the Company’s common stock on the date of grant. The Company expenses stock-based compensation related to stock options, RSAs and RSUs over the requisite service period using the straight-line method. All stock-based compensation costs are recorded in research and development expense or general and administrative expense in the consolidated statements of operations based upon the respective employee’s roles within the Company. Forfeitures are recorded as they occur.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse, and net operating loss (“NOL”) carryforwards and research and development tax credit (“R&D Credit”) carryforwards. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has recorded a full valuation allowance to reduce its net deferred income tax assets to zero. In the event the Company were to determine that it would be able to realize some or all its deferred income tax assets in the future, an adjustment to the deferred income tax asset valuation allowance would increase income in the period such determination was made. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. At December 31, 2019, the Company had no liability for income tax associated with uncertain tax positions. During the year ended December 31, 2020, the Company recorded gross unrecognized tax benefits that were not significant. The unrecognized tax benefits, if recognized, would not affect the effective income tax rate due to the valuation allowance that currently offsets deferred tax assets. The Company does not expect the unrecognized tax benefits to change significantly over the next 12 months. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred for the year ended December 31, 2020 or for the period from Inception to December 31, 2019.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is equal to net loss as presented in the accompanying consolidated statements of operations, as the Company did not have any other comprehensive income or loss for the periods presented.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (“ASC 606”). This guidance applies to any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards. The core principle of this guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance supersedes existing revenue recognition guidance, including most industry-specific guidance, as well as certain related guidance on accounting for contract costs. The Company early adopted ASC 606 upon its Inception. As the Company does not have any contracts with customers, the adoption of this guidance did not have any impact on the Company’s consolidated financial statements. In June 2018, the FASB issued Accounting Standards Update (“ASU”) No. 2018-07, Compensation – Stock Compensation (Topic 718) (“ASU 2018-07”). This update is intended to reduce cost and complexity and to improve financial reporting for share-based payments issued to non-employees (for example, service providers, external legal counsel, suppliers, etc.). The ASU expands the scope of Topic 718, Compensation—Stock Compensation, which currently only includes share-based payments issued to employees, to also include share-based payments issued to non-employees for goods and services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. The Company early adopted ASU 2018-07 upon its Inception. The adoption of this ASU did not have a material effect on the Company’s consolidated financial statements at Inception. The Company applied this accounting pronouncement to the issuance of shares to the Board of Regents of the University of Texas System (see Note 5). In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (ASC Topic 820) (“ASU 2018-13”), which modifies, removes and adds certain disclosure requirements on fair value measurements based on the FASB Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements. The amendments on changes in unrealized gains and losses, the range and weighted-average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. The Company adopted ASU 2018-13 as of January 1, 2020 for the annual period. The adoption of the guidance did not have a material impact on the Company’s consolidated financial statements. In November 2018, the FASB issued ASU No. 2018-18 – Collaborative Arrangements, which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. The Company early adopted this standard as of January 1, 2020 for the annual period and it will be applied to interim periods after December 31, 2020. This ASU requires retrospective adoption to the date the Company adopted ASC 606, which was upon its Inception, by recognizing a cumulative-effect adjustment to the opening balance of retained earnings of the earliest annual period presented. As the Company does not have any contracts with customers or collaborative arrangements, the adoption of this guidance did not have any impact on the Company’s consolidated financial statements.
Recently Issued Accounting Pronouncements Policy	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as amended, with guidance regarding the accounting for and disclosure of leases. This update requires lessees to recognize the liabilities related to all leases, including operating leases, with a term greater than 12 months on the balance sheets. This update also requires lessees and lessors to disclose key information about their leasing transactions. This guidance will become effective for the Company for annual reporting periods beginning after December 15, 2021 and interim periods within fiscal years beginning after December 15, 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify various aspects related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. This guidance is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements.

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Schedule of Restricted Stock Units Activity

The Company’s RSU activity for the year ended December 31, 2020 was as follows:

			Weighted
			Average
			Grant Date
	Number		Fair Value
	of Shares		per Share
Nonvested at January 1, 2020		—	$	—
Replacement restricted units granted		2,518,932		5.25
Restricted units granted		331,121		14.90
Vested		—		—
Nonvested at December 31, 2020		2,850,053	$	6.37

Schedule of Restricted Stock Awards Activity

The Company’s RSA activity for the year ended December 31, 2020 was as follows:

			Weighted
			Average
			Grant Date
	Number		Fair Value
	of Shares		per Share
Nonvested at December 31, 2019		—	$	—
Restricted stock granted		769,058		5.28
Vested		—		—
Nonvested at December 31, 2020		769,058	$	5.28

Schedule of Total Stock-Based Compensation Expense for Stock Options, RSAs and RSUs (Detail)

	For the Year Ended December 31, 2020		For the period from September 20, 2019 (date of inception) to December 31, 2019
Research and development expense	$	1,167	$	—
General and administrative expense		2,187		—
Total	$	3,354	$	—

Cancelled Options

Schedule of Assumptions Used to Estimate Fair Value of Stock Options and Cancelled Options

The following assumptions were used to estimate the fair value of the Cancelled Options that were granted on July 1, 2020:

Risk-free interest rate	0.31	%
Expected dividend yield	—
Expected term in years	6.3
Expected volatility	80	%

Stock Options

Schedule of Assumptions Used to Estimate Fair Value of Stock Options and Cancelled Options

The following weighted-average assumptions were used to estimate the fair value of stock options, excluding the Cancelled Options, for the year ended December 31, 2020:

Risk-free interest rate	0.54	%
Expected dividend yield	—
Expected term in years	6.2
Expected volatility	77	%

Schedule of Stock Option Activity, Excluding Cancelled Options

The following table summarizes stock option activity, excluding the Cancelled Options, during the year ended December 31, 2020:

					Weighted
			Weighted		Average		Aggregate
			Average		Remaining		Intrinsic
	Stock		Exercise		Contractual		Value
	Options		Price		Life (in years)		(in thousands)
Outstanding at December 31, 2019		—	$	—		—	$	—
Options granted		674,842		20.68
Outstanding at December 31, 2020		674,842	$	20.68		9.8	$	3,953
Vested and expected to vest at December 31, 2020		674,842	$	20.68		9.8	$	3,953
Options exercisable at December 31, 2020		12,054	$	20.25		9.8	$	76

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Federal Statutory Income Tax Rate

The effective tax rate of the Company's provision (benefit) for income taxes differs from the federal statutory rate as follows:

	For the Year Ended December 31, 2020			For the Period from September 20, 2019 (date of inception) to December 31, 2019
Statutory rate		21.00	%		21.00	%
State tax		0.06	%		—
General business credits		1.06	%		—
Other permanent differences		(0.25	)%		—
Change in valuation allowance		(15.91	)%		(21.00	)%
Change in fair value of tranche liability		(5.96	)%		—
Income tax provision (benefit)		0.00	%		0.00	%

Schedule of Significant Components of Net Deferred Tax Asset

At December 31, 2020 and December 31, 2019, the significant components of the Company’s net deferred tax asset are as follows (in thousands):

	For the Year Ended December 31, 2020			For the Period from September 20, 2019 (date of inception) to December 31, 2019
Net operating loss carryforwards	$	5,810		$	—
Tax credit carryforwards		672			—
Accruals and reserves		334			—
Other		21			—
Intangibles		2,390			206
Organizational and start-up costs		—			28
Non-qualified stock options		555			—
Total deferred tax assets		9,782			234
Valuation allowance		(9,782	)		(234	)
Deferred tax asset, net of allowance	$	—		$	—

Organization and Description of Business Operations - Additional Information (Details) $ / shares in Units, $ in Thousands				2 Months Ended	3 Months Ended	5 Months Ended	12 Months Ended
	Sep. 29, 2020 shares	Sep. 28, 2020 USD ($) $ / shares shares	Sep. 16, 2020 shares	Aug. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($)	Jul. 31, 2020 USD ($) shares	Dec. 31, 2020 USD ($) $ / shares shares	Jul. 01, 2020 shares	Jun. 30, 2020 $ / shares
Organization and Description of Business Operations [Line Items]
Date of incorporation							Feb. 13, 2020
Share issue price per share \| $ / shares									$ 7.52
Accumulated deficit \| $					$ (1,115)		$ (61,126)
Series A Convertible Preferred Stock
Organization and Description of Business Operations [Line Items]
Conversion of convertible preferred stock to common stock, shares		10,000,000					10,000,000
Aggregate shares sold						10,000,000
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $					0	$ 30,000	$ 29,395
Series B Convertible Preferred Stock
Organization and Description of Business Operations [Line Items]
Conversion of convertible preferred stock to common stock, shares		5,647,048					5,647,048
Aggregate shares sold				5,647,048
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $				$ 96,000	$ 0		$ 95,815
IPO
Organization and Description of Business Operations [Line Items]
Issuance of shares of common stock, shares		7,869,566					9,050,000
Share issue price per share \| $ / shares		$ 20.00					$ 20.00
Net proceeds from issuance of common stock \| $		$ 165,900
Increase in outstanding shares		26,097,378
Underwriters’ Option to Purchase Additional Shares
Organization and Description of Business Operations [Line Items]
Issuance of shares of common stock, shares	1,180,434	1,180,434
2020 Equity Incentive Plan
Organization and Description of Business Operations [Line Items]
Number of common stock authorized for issuance			3,845,294
Common Stock
Organization and Description of Business Operations [Line Items]
Conversion ratio		1.0895	1.0895
Issuance of shares of common stock, shares							9,050,000
Conversion of convertible to common stock, shares		17,047,378					17,047,378
Common Stock \| 2020 Equity Incentive Plan
Organization and Description of Business Operations [Line Items]
Number of common stock authorized for issuance			3,845,294					3,529,412

Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Sep. 30, 2020
Significant Accounting Policies [Line Items]
Assets	$ 15,000	$ 258,881,000
Cash equivalents	0	0
Deferred offering costs	15,000	0
Impairment losses	0	0
Liability for income tax associated with uncertain tax positions	0
Unrecognized tax benefits to change significantly over next 12 months		0
Interest and penalties associated with income tax positions	0	$ 0
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, useful life		3 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment, useful life		5 years
Series A Convertible Preferred Stock
Significant Accounting Policies [Line Items]
Deferred offering costs	15,000
IPO
Significant Accounting Policies [Line Items]
Deferred offering costs			$ 2,500,000
United States
Significant Accounting Policies [Line Items]
Assets	$ 0	$ 0

Research, Collaboration, Grant and License Agreements - Additional Information (Details)		1 Months Ended				2 Months Ended	3 Months Ended	12 Months Ended
	Oct. 29, 2020 USD ($)	Oct. 31, 2020 USD ($)	Aug. 31, 2020 USD ($)	Apr. 30, 2020 USD ($) Product	Dec. 31, 2019 USD ($) $ / shares shares	Nov. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) shares	Jun. 30, 2020 $ / shares	Mar. 31, 2020 shares	Feb. 21, 2020 USD ($)	Nov. 30, 2019 shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued \| shares					10,894,999		10,894,999	37,761,435
Stock price per share \| $ / shares									$ 7.52
Research and development							$ 987,000	$ 31,893,000
UT Southwestern Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preclinical activities period under sponsored research agreements				2 years
Minimum licensed product to develop obtain regulatory approval for and commercialize \| Product				1
Common stock, shares issued \| shares										0		2,179,000
Percentage of fully diluted common stock shares outstanding												20.00%
Percentage of entitled to receive additional shares on fully diluted basis												10.00%
UT Southwestern Agreement \| Discount for Lack of Marketability
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Measurement input					20		20
UT Southwestern Agreement \| Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Share issued an increase to common stock and additional paid in capital							$ 980,000
Stock price per share \| $ / shares					$ 0.45		$ 0.45
Queen's Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research grant of committed fund amount					$ 3,800,000
Percentage of interest rate					6.00%		6.00%
Research grant outstanding fund amount								0
Queen's Agreement \| Research and Development Expense
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash payment to acquire license agreement				$ 3,000,000
Queen's Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement regulatory milestones payment											$ 10,000,000
License agreement commercial milestones payment											$ 10,000,000
Abeona CLN1 Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee payment			$ 3,000,000
Purchase of clinical materials and reimbursement incurred development costs		$ 4,000,000
Research and development								7,000,000
License fee								$ 3,000,000
Abeona CLN1 Agreements \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License and inventory purchase agreement regulatory related milestones payment			26,000,000
License and inventory purchase agreement sales related milestones payment			$ 30,000,000
Abeona \| Abeona Rett Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of one-time upfront license fee	$ 3,000,000
Abeona \| Maximum \| Abeona Rett Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory related milestones obligation payable	26,500,000
Sale-related milestones per licensed product and royalties on net sales of licensed products payable	$ 30,000,000
Catalent Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of upfront project initiation fee						$ 2,000,000

Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability - Additional Information (Details)										2 Months Ended	3 Months Ended	5 Months Ended	12 Months Ended
	Sep. 29, 2020 shares	Sep. 28, 2020 USD ($) $ / shares shares	Sep. 16, 2020	Jul. 28, 2020 $ / shares shares	Jul. 02, 2020 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 05, 2020 shares	Mar. 04, 2020 USD ($) $ / shares shares	Nov. 19, 2019 USD ($) shares	Aug. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Jul. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized		200,000,000		32,685,000							10,895,000		200,000,000
Common stock, par value per share \| $ / shares											$ 0.00001		$ 0.00001
Issuance of shares of common stock \| $													$ 165,854,000
Equity-based awards \| $													$ 3,354,000
Convertible preferred stock, shares authorized				15,647,052
Convertible preferred stock, shares authorized		10,000,000									0		10,000,000
Preferred stock, shares issued											0		0
Preferred stock, shares outstanding											0		0
Share issue price per share \| $ / shares						$ 7.52
Preferred stock tranche liability \| $								$ 1,100,000
Non cash expenses due to remeasured fair value of tranche liability \| $						$ 17,000,000					$ 0		$ (17,030,000)
Mile stone shares issued during the period					4,000,000	200,000
Tranche liability amount reclassified to convertible preferred stock \| $					$ 18,100,000
IPO
Class Of Stock [Line Items]
Shares issued during period		7,869,566											9,050,000
Share issue price per share \| $ / shares		$ 20.00											$ 20.00
Gross proceeds from issuance of common stock \| $		$ 181,000,000
Stock issuance costs, including underwriters’ discounts and commissions \| $		$ 15,100,000
Increase in outstanding shares		26,097,378
Underwriters’ Option to Purchase Additional Shares
Class Of Stock [Line Items]
Shares issued during period	1,180,434	1,180,434
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares authorized				10,000,000
Conversion of convertible preferred stock to common stock, shares		10,000,000											10,000,000
Number of share options exercised					3,800,000	200,000
Clinical milestones for gross proceeds \| $					$ 11,400,000	$ 600,000
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $											0	$ 30,000,000	$ 29,395,000
Convertible preferred stock tranche liability, offering price \| $ / shares								$ 3.00
Convertible preferred stock tranche liability, term								1 year
Milestone pro-rate shares issued during the period						200,000
Series A Convertible Preferred Stock \| Risk Free Rate
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.0059
Series A Convertible Preferred Stock \| Expected Volatility
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.80
Series A Convertible Preferred Stock \| Probability of Achieving Clinical Milestones and Timing
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.60
Series A Convertible Preferred Stock \| Private Placement \| Series A Purchase Agreement
Class Of Stock [Line Items]
Share issue price per share \| $ / shares								$ 3.00
Series A Convertible Preferred Stock \| Private Placement \| Series A Purchase Agreement \| Maximum
Class Of Stock [Line Items]
Shares issued during period								10,000,000
Series A Convertible Preferred Stock \| Private Placement \| Initial Closing
Class Of Stock [Line Items]
Shares issued during period								6,000,000
Series A Convertible Preferred Stock \| Private Placement \| Achievement of Specific Clinical Milestone One
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Series A Convertible Preferred Stock \| Private Placement \| Achievement of Specific Clinical Milestone Two
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Series A Convertible Preferred Stock \| Private Placement \| Upon Achievement of Certain Defined Clinical Milestones
Class Of Stock [Line Items]
Shares issued during period								4,000,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares authorized				5,647,052
Conversion of convertible preferred stock to common stock, shares		5,647,048											5,647,048
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $										$ 96,000,000	0		$ 95,815,000
Convertible preferred stock tranche liability, offering price \| $ / shares						$ 17.00
Convertible preferred stock tranche liability, term						6 months
Series B Convertible Preferred Stock \| Risk Free Rate
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input						0.0017
Series B Convertible Preferred Stock \| Expected Volatility
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input						0.80
Series B Convertible Preferred Stock \| Series B Purchase Agreement
Class Of Stock [Line Items]
Share issue price per share \| $ / shares					$ 17.00
Series B Convertible Preferred Stock \| Private Placement \| Series B Purchase Agreement
Class Of Stock [Line Items]
Shares issued during period				5,647,048
Share issue price per share \| $ / shares				$ 17.00
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $										$ 96,000,000
Series B Convertible Preferred Stock \| Private Placement \| Series B Purchase Agreement \| Maximum
Class Of Stock [Line Items]
Shares issued during period				5,647,052
UT System in Connection with UT Southwestern Agreement
Class Of Stock [Line Items]
Shares issued during period									2,179,000
Issuance of shares of common stock \| $									$ 980,000
Equity-based awards \| $											$ 0
PBM TGT Holdings, LLC \| Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Shares issued during period						3,266,667
Nolan Capital, LLC \| Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Shares issued during period						400,000
Common Stock
Class Of Stock [Line Items]
Shares issued during period													9,050,000
Amount owed for issuance settled month and year													2020-07
Conversion of stock, shares issued		17,047,378											17,047,378
Conversion ratio		1.0895	1.0895
RA Session II \| Common Stock
Class Of Stock [Line Items]
Shares issued during period											8,661,524
One Other Individual \| Common Stock
Class Of Stock [Line Items]
Shares issued during period											54,475

Stock-Based Compensation - Additional Information (Details) - USD ($)				4 Months Ended	12 Months Ended
	Sep. 16, 2020	Sep. 02, 2020	Jul. 01, 2020	Dec. 31, 2020	Dec. 31, 2020	Jul. 02, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock per share			$ 5.28
Series B Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock, issuing price per share						$ 17.00
Employee Stock Purchase Plan (“ESPP”)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	724,000
Share-based payment award, expiration period	10 years
Share-based payment award, expiration date	Jan. 01, 2030
Percentage of automatic increase every year in common stock shares reserved for future issuance	1.00%
Share-based payment award, terms of award issuance					The number of shares of common stock that are automatically added on January 1st of each year for a period of up to ten years, commencing on the first January 1 following the IPO Date and ending on (and including) January 1, 2030, in an amount equal to the lesser of (i) one percent (1.0%) of the total number of shares of capital stock outstanding on December 31st of the preceding calendar year, and (ii) 724,000 shares of common stock
Number of shares of common stock issued under ESPP	0
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares awarded					2,518,932
Share-based payment award, compensation cost not yet recognized, weighted-average period of recognition					2 years 1 month 6 days
Share-based payment award, RSU/RSA granted					331,121
Share-based payment award, unvested RSU/RSA granted, compensation cost not yet recognized				$ 16,200,000	$ 16,200,000
Share-based payment award, RSU/RSA granted, weighted average grant date fair value					$ 14.90
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, expiration period					10 years
Share-based payment award, options granted					674,842
Share-based payment award, options granted, exercise price per share					$ 20.68
Share-based payment award, options, weighted-average grant date fair value					$ 13.73
Share-based payment award, options, compensation cost not yet recognized				8,800,000	$ 8,800,000
Share-based payment award, compensation cost not yet recognized, weighted-average period of recognition					3 years 7 months 6 days
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, compensation cost not yet recognized, weighted-average period of recognition					2 years 3 months 18 days
Share-based payment award, RSU/RSA granted					769,058
Share-based payment award, unvested RSU/RSA granted, compensation cost not yet recognized				3,200,000	$ 3,200,000
Share-based payment award, RSU/RSA granted, weighted average grant date fair value			$ 5.28		$ 5.28
Maximum \| Employee Stock Purchase Plan (“ESPP”)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance	362,000
Maximum \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period					4 years
Minimum \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period					3 years
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance	3,845,294
Common stock reserved for future issuance	209,841
Share-based payment award, plan modification, incremental cost					$ 0
Share-based payment award, compensation cost not yet recognized				$ 13,200,000	$ 13,200,000
2020 Equity Incentive Plan \| Cancelled Options \| Certain Employees and Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, options granted			2,896,782
Share-based payment award, options granted, exercise price per share			$ 0.80
Award vesting period			4 years
Share-based payment award, options grant date fair value			$ 13,800,000
2020 Equity Incentive Plan \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
Number of shares awarded		2,518,932
Share-based payment award, RSU/RSA granted		331,121
2020 Equity Incentive Plan \| Restricted Stock Units \| Share-based Payment Arrangement, Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, vesting rights percentage		25.00%
2020 Equity Incentive Plan \| Restricted Stock Units \| Share-based Payment Arrangement, Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, vesting rights percentage		25.00%
2020 Equity Incentive Plan \| Restricted Stock Units \| Share-based Payment Arrangement, Tranche Three
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, vesting rights percentage		25.00%
2020 Equity Incentive Plan \| Restricted Stock Units \| Share-based Payment Arrangement, Tranche Four
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, vesting rights percentage		25.00%
2020 Equity Incentive Plan \| Stock Options \| Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, options granted		16,342
Share-based payment award, options granted, exercise price per share		$ 14.90
2020 Equity Incentive Plan \| Restricted Stock Awards \| RA Session II
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, RSU/RSA granted			769,058
Award requisite service vesting period			3 years
2020 Equity Incentive Plan \| Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance	3,845,294		3,529,412
New Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	3,390,168			2,941,509	2,941,509
Share-based payment award, expiration period	10 years
Share-based payment award, commencement date	Jan. 01, 2021
Share-based payment award, expiration date	Jan. 01, 2030
Percentage of automatic increase every year in common stock shares reserved for future issuance	5.00%
Share-based payment award, terms of award issuance					At December 31, 2020, there were 2,941,509, shares available for future grant under the New Plan. The number of shares of common stock reserved for issuance under the New Plan will automatically increase on January 1 of each year, for a period of ten years, from January 1, 2021 continuing through January 1, 2030, by 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors.
New Plan \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award, options granted				658,500
Share-based payment award, options granted, exercise price per share				$ 20.83

Stock-Based Compensation - Schedule of Stock Option Activity, Excluding Cancelled Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding. Stock Options, Beginning Balance
Options granted, Stock Options	674,842
Outstanding. Stock Options, Ending Balance	674,842
Vested and expected to vest at December 31, 2020, Stock Options	674,842
Options exercisable at December 31, 2020, Stock Options	12,054
Outstanding, Weighted Average Exercise Price, Beginning balance
Options granted, Weighted Average Exercise Price	$ 20.68
Outstanding, Weighted Average Exercise Price, Ending balance	20.68
Vested and expected to vest at December 31, 2020, Weighted Average Exercise Price	20.68
Options exercisable at December 31, 2020, Weighted Average Exercise Price	$ 20.25
Outstanding, Weighted Average Remaining Contractual Life	9 years 9 months 18 days
Vested and expected to vest at December 31, 2020, Weighted Average Remaining Contractual Life	9 years 9 months 18 days
Weighted Average Remaining Contractual Life, Options exercisable at December 31, 2020	9 years 9 months 18 days
Outstanding, Aggregate Intrinsic Value, Beginning Balance
Outstanding, Aggregate Intrinsic Value, Ending Balance	$ 3,953
Vested and expected to vest at December 31, 2020, Aggregate Intrinsic Value	3,953
Options exercisable at December 31, 2020, Aggregate Intrinsic Value	$ 76

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Issuance of shares of common stock in initial public offering, net of offering costs and underwriting discounts and commissions	$ 15,145
Issuance of preferred stock tranche liability	1,050
Series A Convertible Preferred Stock
Issuance of convertible preferred stock, offering costs	605
Series B Convertible Preferred Stock
Issuance of convertible preferred stock, offering costs	$ 185

Property and Equipment - Schedule of Property and Equipment (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 296
Accumulated depreciation	(9)
Property and equipment, net	287
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	95
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 201

Supplemental Financial Information - Schedule of Accrued Expenses And Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued research and development	$ 2,106	$ 7
Accrued compensation	1,766
Accrued professional fees	999	122
Other	264	21
Total accrued expenses and other current liabilities	$ 5,135	$ 150

Supplemental Financial Information - Schedule of Prepaid Expenses And Other Current Assets (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Balance Sheet Related Disclosures [Abstract]
Prepaid insurance	$ 2,480
Prepaid research and development	2,462
Prepaid clinical trial	944
Other	740
Total prepaid expenses and other current assets	$ 6,626

Related Party Transactions - Additional Information (Details)	1 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Jan. 31, 2020 USD ($) PromissoryNote	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
PBM Capital Group, LLC \| Services Agreement
Related Party Transaction [Line Items]
Accounting and other administrative and management services fee per month	$ 2,500
Due to related party			$ 9,800
PBM TGT Holdings, LLC
Related Party Transaction [Line Items]
Additional consideration payable under operating agreement				$ 0
RA Session II
Related Party Transaction [Line Items]
Number of secured promissory notes \| PromissoryNote		2
Paul B. Manning \| Services Agreement
Related Party Transaction [Line Items]
Ownership percentage more than capital stock	5.00%
Secured Promissory Notes \| RA Session II
Related Party Transaction [Line Items]
Aggregate amount, related party transaction		$ 1,670,000
Percentage of interest rate		10.00%
Interest expense related party			$ 28,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value per share	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.00001	$ 0.00001
Common stock, shares authorized	200,000,000	10,895,000
Common stock, shares issued	37,761,435	10,894,999
Common stock, shares outstanding	37,761,435	10,894,999

Property and Equipment - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 0	$ 9,000

Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability - Reconciliation of Preferred Stock Tranche Liability Measured at Fair Value (Details) - Preferred Stock Tranche Liability $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value at issuance of Series A convertible preferred stock	$ 1,050
Change in fair value	17,030
Settlement of preferred stock tranche liability due to issuance of Milestone Shares	$ (18,080)

Stock-Based Compensation - Schedule of Restricted Stock Units Activity (Details) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Replacement restricted units granted, Number of Shares \| shares	2,518,932
Restricted units/stock granted, Number of Shares \| shares	331,121
Nonvested, Number of Shares, Ending Balance \| shares	2,850,053
Replacement restricted units granted, Weighted Average Grant Date Fair Value per Share \| $ / shares	$ 5.25
Restricted units/stock granted, Weighted Average Grant Date Fair Value per Share \| $ / shares	14.90
Nonvested, Weighted Average Grant Date Fair Value per Share, Ending Balance \| $ / shares	$ 6.37

Stock-Based Compensation - Schedule of Total Stock-Based Compensation Expense for Stock Options, RSAs and RSUs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,354
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,167
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,187

Net Loss Per Common Share - Schedule of Calculation of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Earnings Per Share [Abstract]
Net loss	$ (1,115)	$ (60,011)
Weighted average common shares outstanding, basic and diluted	9,625,679	17,665,683
Net loss per common share, basic and diluted	$ (0.12)	$ (3.40)

Net Loss Per Common Share - Schedule of Common Stock Equivalents Outstanding Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details)	12 Months Ended
	Dec. 31, 2020 shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	4,293,953
Unvested RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	2,850,053
Unvested RSAs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	769,058
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	674,842

Income Taxes - Schedule of Significant Components of Net Deferred Tax Asset (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Components Of Deferred Tax Assets [Abstract]
Net operating loss carryforwards	$ 5,810,000
Tax credit carryforwards	672,000	$ 0
Accruals and reserves	334,000
Other	21,000
Intangibles	2,390,000	206,000
Organizational and start-up costs		28,000
Non-qualified stock options	555,000
Total deferred tax assets	9,782,000	234,000
Valuation allowance	(9,782,000)	(234,000)
Deferred tax asset, net of allowance

Commitments and Contingencies - Additional Information (Details) $ in Millions		12 Months Ended
	Dec. 17, 2020 ft²	Dec. 31, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Number of operating lease landlord square feet manufacturing facility \| ft²	187,500
Operating lease commencement date	Apr. 01, 2021
Operating lease term of contract	15 years 6 months
Operating lease extend term of contract	5 years
Operating leases initial direct costs \| $		$ 0.8

Commitments and Contingencies - Schedule of Lease Commitments (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2021	$ 314
2022	1,282
2023	1,317
2024	1,354
2025	1,391
Thereafter	17,599
Total Lease Commitments	$ 23,257

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Jan. 11, 2021 USD ($) ft²	Mar. 31, 2021 $ / shares shares	Dec. 31, 2020 USD ($)	Dec. 17, 2020
Subsequent Event [Line Items]
Term of lease period				15 years 6 months
Total future minimum lease payments			$ 23,257
Subsequent Event
Subsequent Event [Line Items]
Options granted for purchase an aggregate share of common stock \| shares		1,621,900
Weighted-average exercise price \| $ / shares		$ 28.81
Subsequent Event \| Dallas Lease \| Pegasus Park, LLC
Subsequent Event [Line Items]
Office space area under lease agreement \| ft²	15,000
Term of lease period	10 years
Lease, option to extend description	Company has an option to extend the term of the Dallas Lease for one additional period of five years.
Lease, option to extend	true
Extending term of lease	5 years
Total future minimum lease payments	$ 4,900