0001564590-20-053602 | 10-Q | XBRL Viewer | Taysha Gene Therapies INC

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Stock-Based Compensation - Schedule of Total Stock-Based Compensation Expense for Stock Options, RSAs and RSUs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,341	$ 1,341
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	399	399
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 942	$ 942

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 278,634
Prepaid expenses	604
Deferred offering costs		$ 15
Total current assets	279,238	15
Property and equipment, net	28
Total assets	279,266	15
Current liabilities
Accounts payable	8,837
Accrued expenses	2,727	150
Due to related party	60
Total current liabilities	11,624	150
Total liabilities	11,624	150
Commitments and contingencies - Note 10
Stockholders' equity (deficit)
Preferred stock, $0.00001 par value per share; 10,000,000 shares authorized and no shares issued and outstanding as of September 30, 2020; no shares authorized, issued and outstanding as of December 31, 2019
Additional paid-in capital	310,450	980
Accumulated deficit	(42,808)	(1,115)
Total stockholders’ equity (deficit)	267,642	(135)
Total liabilities and stockholders' equity (deficit)	$ 279,266	$ 15

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Sep. 20, 2019	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Convertible preferred stock balance, shares at Sep. 20, 2019		0	0
Balance, shares at Sep. 20, 2019				0
Issuance of Founders Shares, shares				8,715,999
Net loss	(31)					(31)
Balance at Sep. 30, 2019	(31)	$ 0	$ 0	$ 0	0	(31)
Convertible preferred stock balance, shares at Sep. 30, 2019		0	0
Balance, shares at Sep. 30, 2019				8,715,999
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	165,889				165,889
Issuance of shares of common stock, shares				9,050,000
Issuance of restricted stock award, shares				769,058
Stock-based compensation	1,341				1,341
Net loss	(41,693)					(41,693)
Balance at Sep. 30, 2020	$ 267,642				310,450	(42,808)
Balance, shares at Sep. 30, 2020	37,761,435			37,761,435
Balance at Jun. 30, 2020	$ (26,786)				980	(27,766)
Convertible preferred stock balance, shares at Jun. 30, 2020		6,200,000
Convertible preferred stock balance at Jun. 30, 2020		$ 18,014
Balance, shares at Jun. 30, 2020				10,894,999
Issuance of convertible preferred stock		$ 11,235	$ 95,815
Issuance of convertible preferred stock, shares		3,800,000	5,647,048
Reclassification of preferred stock tranche liability upon issuance of Series A milestone shares		$ 17,176
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	165,889				165,889
Issuance of shares of common stock, shares				9,050,000
Issuance of restricted stock award, shares				769,058
Stock-based compensation	1,341				1,341
Net loss	(15,042)					(15,042)
Balance at Sep. 30, 2020	$ 267,642				$ 310,450	$ (42,808)
Balance, shares at Sep. 30, 2020	37,761,435			37,761,435

Organization and Description of Business Operations

9 Months Ended

Sep. 30, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Description of Business Operations

Note 1—Organization and Description of Business Operations

Taysha Gene Therapies, Inc. (the “Company” or “Taysha”) was originally formed under the laws of the State of Texas on September 20, 2019 (“Inception”). Taysha converted to a Delaware corporation on February 13, 2020, which had no impact to the Company’s par value or issued and authorized capital structure.

Taysha is a patient-centric gene therapy company focused on developing and commercializing AAV-based gene therapies for the treatment of monogenic diseases of the central nervous system in both rare and large patient populations.

Stock Split

On September 16, 2020, the Company effected a 1.0895-for-one stock split of its authorized, issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company’s convertible preferred stock as discussed in Note 5. Accordingly, all share and per share amounts for the periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this stock split and adjustment of the convertible preferred stock conversion ratios. On September 16, 2020, the Company also increased the number of shares of common stock authorized for issuance under the 2020 Equity Incentive Plan (the “Existing Plan”) to 3,845,294.

Initial Public Offering

On September 23, 2020, the Company’s registration statement on Form S-1 (File No. 333-248559) related to the initial public offering (“IPO”) of its common stock became effective and on September 28, 2020, the IPO closed. Pursuant to the IPO, the Company issued and sold 9,050,000 shares of common stock at a public offering price of $20.00 per share, which included 1,180,434 shares of common stock issued upon the exercise in full of the underwriters’ option to purchase additional shares. The Company received net proceeds of $165.9 million after deducting underwriting discounts and commissions and other offering costs of $2.4 million. The shares began trading on the Nasdaq Global Select Market on September 24, 2020.

On September 28, 2020, in connection with the closing of the IPO, 10,000,000 shares of Series A 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.

As a result of the IPO, including the underwriters’ exercise in full of their option to purchase additional shares, 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.

Upon the effectiveness of the Company’s registration statement related to the IPO, the Company’s 2020 Stock Incentive Plan (the “New Plan”) and 2020 Employee Stock Purchase Plan became effective. At that time, all shares reserved for issuance under the Existing Plan ceased to be available for issuance under such plan and became available for issuance under the New Plan.

Liquidity and Capital Resources

The Company has incurred operating losses since inception, and expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of September 30, 2020, the Company had an accumulated deficit of $42.8 million.

Prior to the closing of the Company’s IPO, between March and July 2020, the Company closed on the sale of an aggregate of 10,000,000 shares of Series A convertible preferred stock for gross proceeds of $30.0 million. Between July and August 2020, the Company closed on the sale of an aggregate of 5,647,048 shares of Series B convertible preferred stock for gross proceeds of $96.0 million.

Due to the proceeds received from the IPO and the sale of its Series A and Series B convertible preferred stock, management believes that its existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these interim condensed consolidated financial statements. Future capital requirements will depend on many factors, including the timing and extent of spending on research and development and the market acceptance of the Company’s products. The Company will need to obtain additional financing in order to complete clinical studies and launch and commercialize any product candidates for which it receives regulatory approval. There can be no assurance that such financing will be available or will be on terms acceptable to the Company.

In December 2019, the novel coronavirus (“COVID-19”) emerged and has subsequently spread worldwide. The World Health Organization has declared COVID-19 a global pandemic, resulting in federal, state and local governments and private entities implementing various restrictions, including travel restrictions, restrictions on public gatherings, stay at home orders, and advisories and quarantining people who may have been exposed to the virus. The Company has been actively monitoring COVID-19 and its impact globally. Management believes the financial results for the nine months ended September 30, 2020 were not significantly impacted by COVID-19. In addition, management believes the remote working arrangements and travel restrictions imposed by various governmental jurisdictions have had limited impact on the Company’s ability to maintain internal operations during the nine months ended September 30, 2020. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19.

Related Party Transactions

9 Months Ended

Sep. 30, 2020

Related Party Transactions

Note 8—Related Party Transactions

RA Session II, President and Chief Executive Officer and a member of the Company’s board of directors, is a guarantor under the Guaranty and Security Agreement between himself, Queen’s and the Company, and in the event of the Company’s failure to fund its obligations under the RGA with Queen’s, has personally guaranteed payments due by the Company to Queen’s.

In January 2020, the Company entered into two secured promissory notes with a related party, its President and Chief Executive Officer, RA Session II, for an aggregate of $1.67 million, with 10% interest. The Company secured the notes with a first priority security interest in certain assets of the Company. As of September 30, 2020, the Company had repaid the notes in full. As a result, Mr. Session released his security interest in the collateral.

In March 2020, the Company entered into a services agreement with PBM Capital Group, LLC (“PBM”), an affiliate of PBM TGT Holdings, LLC (a beneficial owner of greater than 5% of the Company’s common stock), whereby PBM provides accounting and other administrative and management services related to payroll administration, human resources, bookkeeping, preparation of financial statements and tax returns, accounts payable and receivable, and other similar functions for a fee of $2,500 per month. As of September 30, 2020, inclusive of certain pass-through direct costs, the Company has approximately $60,000 due to PBM, which is included in due to related party in the condensed consolidated balance sheet.

Organization and Description of Business Operations - Additional Information (Details) $ / shares in Units, $ in Thousands					2 Months Ended	3 Months Ended	5 Months Ended	9 Months Ended
	Sep. 29, 2020 shares	Sep. 28, 2020 USD ($) $ / shares shares	Sep. 16, 2020 shares	Sep. 30, 2019 USD ($)	Aug. 31, 2020 USD ($) shares	Sep. 30, 2020 USD ($) $ / shares shares	Jul. 31, 2020 USD ($) shares	Sep. 30, 2020 USD ($) $ / shares shares	Jul. 01, 2020 shares	Jun. 30, 2020 $ / shares	Dec. 31, 2019 USD ($)
Organization and Description of Business Operations [Line Items]
Date of incorporation								Feb. 13, 2020
Share issue price per share \| $ / shares										$ 7.52
Accumulated deficit \| $						$ (42,808)		$ (42,808)			$ (1,115)
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		10,000,000
Aggregate shares sold							10,000,000
Gross proceeds from sale of convertible preferred stock \| $				$ 0			$ 30,000	$ 29,569
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		5,647,048
Aggregate shares sold					5,647,048
Gross proceeds from sale of convertible preferred stock \| $				$ 0	$ 96,000			$ 95,815
Underwriters’ Option to Purchase Additional Shares
Organization and Description of Business Operations [Line Items]
Issuance of shares of common stock, shares	1,180,434
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		$ 20.00
Net proceeds from issuance of common stock \| $		$ 165,900
Underwriting discounts and commissions and other offering costs \| $		$ 2,400
Increase in outstanding shares		26,097,378
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		9,050,000
Conversion of stock, shares issued		17,047,378				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

Net Loss Per Common Share (Tables)

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Schedule of Common Stock Equivalents Outstanding Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders

The following common stock equivalents outstanding as of September 30, 2020 were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been anti‑dilutive:

	For the Three Months Ended September 30, 2020
Unvested RSUs		2,850,053
Unvested RSAs		769,058
Stock options		185,342
Total		3,804,453

Subsequent Events

9 Months Ended

Sep. 30, 2020

Subsequent Events [Abstract]

Subsequent Events

Note 11—Subsequent Events

Partnership with Catalent, Inc.

On November 5, 2020, the Company announced a partnership with Catalent, Inc. (“Catalent”) to support the development and manufacturing of the Company’s gene therapies at Catalent’s Maryland-based gene therapy facilities.

License Agreement with Abeona Therapeutics Inc. (Rett)

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. 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.

Partnership with Invitae Corporation

On October 6, 2020, the Company announced a partnership with Invitae Corporation (“Invitae”) to support Invitae’s Detect Lysosomal Storage Diseases (Detect LSDs) and Behind the Seizure® programs. The partnership is intended to help identify individuals who are eligible for the Company’s Phase 1/2 clinical trial evaluating TSHA-101 in patients with GM2 gangliosidosis and patient identification across the Company’s gene therapy pipeline.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 6—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. 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. No future issuances were made under the Existing Plan upon the effectiveness of the New Plan.

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 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 three months ended September 30, 2020, options to purchase 185,342 shares of common stock were granted with a weighted-average exercise price per share of $19.55. 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 September 23, 2020, 169,000 shares of common stock under the New Plan were awarded with an exercise price per share of $20.00. 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 nine months ended September 30, 2020:

Risk-free interest rate	0.46%
Expected dividend yield		-
Expected term in years	6.7
Expected volatility		80	%

The following table summarizes stock option activity, excluding the Cancelled Options, during the nine months ended September 30, 2020:

	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020		-	$	-		-	$	-
Options granted		185,342		19.55		10.0		528
Outstanding at September 30, 2020		185,342	$	19.55		10.0	$	528
Vested and expected to vest at September 30, 2020		185,342	$	19.55		10.0	$	528
Options exercisable at September 30, 2020		-	$	-		-	$	-

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 September 30, 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 nine months ended September 30, 2020 was $13.73. As of September 30, 2020, the total unrecognized compensation related to unvested stock option awards granted was $2.5 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 September 30, 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 $17.8 million which is expected to be amortized on a straight-line basis over the weighted-average remaining vesting period of approximately 2.2 years. The Company’s RSU activity for the nine months ended September 30, 2020 was as follows:

	Number of Shares		Weighted Average Grant Date Fair Value 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 September 30, 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 September 30, 2020, the total unrecognized compensation related to unvested RSAs granted was $3.7 million which is expected to be amortized on a straight-line basis over the weighted-average remaining vesting period of approximately 1.4 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 nine months ended September 30, 2020 was as follows:

	Number of Shares		Weighted Average Grant Date Fair Value per Share
Nonvested at January 1, 2020		-	$	-
Restricted stock granted		769,058		5.28
Vested		-		-
Nonvested at September 30, 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 condensed consolidated statements of operations for the three and nine months ended September 30, 2020 (in thousands):

	For the Three Months Ended September 30, 2020		For the Nine Months Ended September 30, 2020
Research and development expense	$	399	$	399
General and administrative expense		942		942
Total	$	1,341	$	1,341

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

9 Months Ended

Sep. 30, 2020

Equity [Abstract]

Reconciliation of Preferred Stock Tranche Liability Measured at Fair Value

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 January 1, 2020	$	-
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 September 30, 2020	$	-

Net Loss Per Common Share

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Net Loss Per Common Share

Note 7—Net Loss Per Common Share

Basic net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. Since the Company had a net loss in the period presented, basic and diluted net loss per common share are the same.

	For the Three Months Ended September 30, 2020
Unvested RSUs		2,850,053
Unvested RSAs		769,058
Stock options		185,342
Total		3,804,453

Stock-Based Compensation - Schedule of Restricted Stock Awards Activity (Details) - Restricted Stock Awards - $ / shares		9 Months Ended
	Jul. 01, 2020	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted units/stock granted, Number of Shares		769,058
Nonvested, Number of Shares, Ending Balance		769,058
Restricted units/stock granted, Weighted Average Grant Date Fair Value per Share	$ 5.28	$ 5.28
Nonvested, Weighted Average Grant Date Fair Value per Share, Ending Balance		$ 5.28

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2020	Nov. 12, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
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	No
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 Quarterly Report	true
Document Transition Report	false

Stock-Based Compensation - Schedule of Assumptions Used to Estimate Fair Value of Stock Options and Cancelled Options (Details)		9 Months Ended
	Jul. 01, 2020	Sep. 30, 2020
Cancelled Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.31%
Expected term in years	6 years 3 months 18 days
Expected volatility	80.00%
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		0.46%
Expected term in years		6 years 8 months 12 days
Expected volatility		80.00%

Supplemental Financial Information (Tables)

9 Months Ended

Sep. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):

	September 30, 2020		December 31, 2019
Accrued research and development	$	767	$	7
Accrued issuance costs		752		-
Accrued compensation		544		-
Accrued professional fees		462		122
Other		202		21
Total accrued expenses	$	2,727	$	150

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 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

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020
Cash flows from operating activities
Net loss	$ (31)	$ (41,693)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	0	3
Change in fair value of preferred stock tranche liability	0	17,030
Research and development license expense	0	6,000
Stock-based compensation	0	1,341
Changes in operating assets and liabilities:
Prepaid expenses	0	(604)
Accounts payable	0	5,403
Accrued expenses	31	1,579
Due to related party	0	60
Net cash used in operating activities	0	(10,881)
Cash flows from investing activities
Purchase of research and development license	0	(3,000)
Purchase of property and equipment	0	(31)
Net cash used in investing activities	0	(3,031)
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	167,162
Proceeds from notes payable to related party	0	1,673
Repayment of notes payable to related party	0	(1,673)
Net cash provided by financing activities	0	292,546
Net increase in cash and cash equivalents	0	278,634
Cash at the beginning of the period	0
Cash at the end of the period	0	278,634
Supplemental disclosure of cash flow information:
Cash paid for interest	0	28
Supplemental disclosure of noncash investing and financing activities:
Reclassification of preferred stock tranche liability upon share issuance	0	18,080
Allocation of preferred stock tranche liability	0	1,050
Conversion of Series A and Series B convertible preferred stock to common stock	0	142,240
Purchase of research and development license not yet paid	0	3,000
Series A Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuances of convertible preferred stock, net of issuance costs	0	29,569
Supplemental disclosure of noncash investing and financing activities:
Issuance costs for issuances of stock not yet paid	0	174
Series B Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuances of convertible preferred stock, net of issuance costs	0	95,815
Common Stock
Supplemental disclosure of noncash investing and financing activities:
Issuance costs for issuances of stock not yet paid	$ 0	$ 1,273

Subsequent Events - Additional Information (Details) - Abeona Rett Agreement - Abeona - Subsequent Event	Oct. 29, 2020 USD ($)
Subsequent Event [Line Items]
Payment of one-time upfront license fee	$ 3,000,000
Maximum
Subsequent Event [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

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Significant Accounting Policies [Line Items]
Cash equivalents	$ 0
Deferred offering costs		$ 15,000
Property and equipment, useful life	3 years
Impairment losses	$ 0
IPO
Significant Accounting Policies [Line Items]
Deferred offering costs	$ 2,400,000

Stock-Based Compensation - Schedule of Restricted Stock Units Activity (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 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

Commitments and Contingencies

9 Months Ended

Sep. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 10—Commitments and Contingencies

Litigation

The Company is not a party to any material legal proceedings and is not aware of any pending or threatened claims. From time to time, the Company may be subject to various legal proceedings and claims that arise in the ordinary course of its business activities.

Commitments

As of September 30, 2020, the Company was not a party to any leasing agreements.

In the normal course of business, the Company enters into contracts that contain a variety of indemnifications with its employees, licensors, suppliers and service providers. The Company’s maximum exposure under these arrangements is unknown at September 30, 2020. The Company does not anticipate recognizing any significant losses relating to these arrangements.

Supplemental Financial Information - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued research and development	$ 767	$ 7
Accrued issuance costs	752
Accrued compensation	544
Accrued professional fees	462	122
Other	202	21
Total accrued expenses	$ 2,727	$ 150

Income Taxes

9 Months Ended

Sep. 30, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 9—Income Taxes

Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. Based on its history of operating losses, the Company believes that it is more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for its deferred tax assets as of September 30, 2020 and December 31, 2019.

On March 27, 2020, the U.S. President signed into law the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”), an economic relief package in response to the COVID-19 global pandemic. The CARES Act contains several corporate income tax provisions, including making remaining alternative minimum tax credits immediately refundable; providing a 5-year carryback of net operating loss carryforwards (“NOLs”) 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 Company is still evaluating the impact but does not currently expect the provisions of the CARES Act to have a material effect on the realizability of deferred income tax assets or tax expense.

As of September 30, 2020, there were no material changes to either the nature or the amounts of the uncertain tax positions previously determined for the period from September 20, 2019 (date of inception) through December 31, 2019.

- 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

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Schedule of Restricted Stock Units Activity

The Company’s RSU activity for the nine months ended September 30, 2020 was as follows:

	Number of Shares		Weighted Average Grant Date Fair Value 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 September 30, 2020		2,850,053	$	6.37

Schedule of Restricted Stock Awards Activity

The Company’s RSA activity for the nine months ended September 30, 2020 was as follows:

	Number of Shares		Weighted Average Grant Date Fair Value per Share
Nonvested at January 1, 2020		-	$	-
Restricted stock granted		769,058		5.28
Vested		-		-
Nonvested at September 30, 2020		769,058	$	5.28

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

	For the Three Months Ended September 30, 2020		For the Nine Months Ended September 30, 2020
Research and development expense	$	399	$	399
General and administrative expense		942		942
Total	$	1,341	$	1,341

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 nine months ended September 30, 2020:

Risk-free interest rate	0.46%
Expected dividend yield		-
Expected term in years	6.7
Expected volatility		80	%

Schedule of Stock Option Activity, Excluding Cancelled Options

The following table summarizes stock option activity, excluding the Cancelled Options, during the nine months ended September 30, 2020:

	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020		-	$	-		-	$	-
Options granted		185,342		19.55		10.0		528
Outstanding at September 30, 2020		185,342	$	19.55		10.0	$	528
Vested and expected to vest at September 30, 2020		185,342	$	19.55		10.0	$	528
Options exercisable at September 30, 2020		-	$	-		-	$	-

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2020
Operating expenses:
Research and development		$ 11,057	$ 19,633
General and administrative	$ 31	3,984	5,002
Total operating expenses	31	15,041	24,635
Loss from operations	(31)	(15,041)	(24,635)
Other expense:
Change in fair value of preferred stock tranche liability			(17,030)
Interest expense		(1)	(28)
Total other expense		(1)	(17,058)
Net loss	$ (31)	$ (15,042)	$ (41,693)
Net loss per common share, basic and diluted	$ 0.00	$ (1.28)	$ (3.73)
Weighted average common shares outstanding, basic and diluted	8,715,999	11,733,170	11,176,429

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the balances and results for the periods presented. Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with GAAP have been condensed or omitted. These condensed consolidated financial statement results are not necessarily indicative of results to be expected for the full fiscal year or any future period. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements and notes thereto for the period from September 20, 2019 (date of inception) through December 31, 2019 included in the Company’s final prospectus dated September 23, 2020 and filed with the Securities and Exchange Commission on September 25, 2020, pursuant to Rule 424(b)(4).
Principles of Consolidation	Principles of Consolidation The accompanying interim condensed 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.
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. These estimates and assumptions are based on current facts, historical experience as well as other pertinent industry and regulatory authority information, including the potential future effects of COVID-19, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially and adversely from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of funds held in a standard checking 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 September 30, 2020, the Company does not have any 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 condensed consolidated balance sheet for cash and cash equivalents, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short-term nature of these items.
Deferred Offering Costs	Deferred Offering Costs 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. Upon completion of the IPO, approximately $2.4 million of deferred offering costs were offset against the IPO proceeds in additional paid-in capital.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and consist solely of computer equipment. Depreciation expense is recognized using the straight-line method over its estimated useful life of 3 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 nine months ended September 30, 2020.
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 5) 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 condensed consolidated statement 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 condensed consolidated balance sheet.
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 (“RSAs”) and restricted stock units (“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 condensed consolidated statements of operations based upon the respective employee’s roles within the Company. Forfeitures are recorded as they occur.
Recently Issued Accounting Pronouncements	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 sheet. 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 interim condensed 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, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the impact of this standard on its interim condensed consolidated financial statements.

Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability - Additional Information (Details) $ / shares in Units, $ in Thousands										2 Months Ended	3 Months Ended	5 Months Ended	9 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	Sep. 30, 2019 USD ($)	Aug. 31, 2020 USD ($)	Sep. 30, 2020 $ / shares shares	Jul. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 shares
Class Of Stock [Line Items]
Share issue price per share \| $ / shares						$ 7.52
Common stock, shares authorized		200,000,000		32,685,000							200,000,000		200,000,000	10,895,000
Convertible preferred stock, shares authorized				15,647,052
Convertible preferred stock, shares authorized		10,000,000									10,000,000		10,000,000	0
Preferred stock, shares issued											0		0	0
Preferred stock, shares outstanding											0		0	0
Preferred stock tranche liability \| $								$ 1,100
Non cash expenses due to remeasured fair value of tranche liability \| $						$ 17,000			$ 0				$ (17,030)
Mile stone shares issued during the period					4,000,000	200,000
Amount reclassified to convertible preferred stock \| $					$ 18,100
Common Stock
Class Of Stock [Line Items]
Shares issued during period											9,050,000		9,050,000
Conversion of stock, shares issued		17,047,378									17,047,378		17,047,378
Conversion ratio		1.0895	1.0895
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock to common stock, shares		10,000,000									10,000,000		10,000,000
Convertible preferred stock, shares authorized				10,000,000
Number of share options exercised					3,800,000	200,000
Clinical milestones for gross proceeds \| $					$ 11,400	$ 600
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $									0			$ 30,000	$ 29,569
Convertible preferred stock tranche liability, offering price \| $ / shares								$ 3.00
Convertible preferred stock tranche liability, term								1 year
Mile stone 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 \| PBM TGT Holdings, LLC
Class Of Stock [Line Items]
Shares issued during period						3,266,667
Series A Convertible Preferred Stock \| Nolan Capital, LLC
Class Of Stock [Line Items]
Shares issued during period						400,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock to common stock, shares		5,647,048									5,647,048		5,647,048
Convertible preferred stock, shares authorized				5,647,052
Proceeds from issuances of convertible preferred stock, net of issuance costs \| $									$ 0	$ 96,000			$ 95,815
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
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		$ 20.00
Gross proceeds from issuance of common stock \| $		$ 181,000
Stock issuance costs, including underwriters’ discounts and commissions \| $		$ 15,100
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
Private Placement \| Series A Convertible Preferred Stock \| Series A Purchase Agreement
Class Of Stock [Line Items]
Share issue price per share \| $ / shares								$ 3.00
Private Placement \| Series A Convertible Preferred Stock \| Series A Purchase Agreement \| Maximum
Class Of Stock [Line Items]
Shares issued during period								10,000,000
Private Placement \| Series A Convertible Preferred Stock \| Initial Closing
Class Of Stock [Line Items]
Shares issued during period								6,000,000
Private Placement \| Series A Convertible Preferred Stock \| Achievement of Specific Clinical Milestone One
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Private Placement \| Series A Convertible Preferred Stock \| Achievement of Specific Clinical Milestone Two
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Private Placement \| Series A Convertible Preferred Stock \| Upon Achievement of Certain Defined Clinical Milestones
Class Of Stock [Line Items]
Shares issued during period								4,000,000
Private Placement \| Series B Convertible Preferred Stock \| 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
Private Placement \| Series B Convertible Preferred Stock \| Series B Purchase Agreement \| Maximum
Class Of Stock [Line Items]
Shares issued during period				5,647,052

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2—Summary of Significant Accounting Policies

Basis of Presentation

The condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as determined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the balances and results for the periods presented. Certain information and note disclosures normally included in the Company’s annual financial statements prepared in accordance with GAAP have been condensed or omitted. These condensed consolidated financial statement results are not necessarily indicative of results to be expected for the full fiscal year or any future period. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements and notes thereto for the period from September 20, 2019 (date of inception) through December 31, 2019 included in the Company’s final prospectus dated September 23, 2020 and filed with the Securities and Exchange Commission on September 25, 2020, pursuant to Rule 424(b)(4).

Principles of Consolidation

The accompanying interim condensed 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.

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. These estimates and assumptions are based on current facts, historical experience as well as other pertinent industry and regulatory authority information, including the potential future effects of COVID-19, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially and adversely from these estimates. To the extent there are material differences between the estimates and actual results, the Company’s future results of operations will be affected.

Significant Accounting Policies

There have been no changes in the Company’s significant accounting policies as disclosed in the audited financial statements as of December 31, 2019, except as noted below.

Cash and Cash Equivalents

Cash and cash equivalents consist of funds held in a standard checking 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 September 30, 2020, the Company does not have any 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 condensed consolidated balance sheet for cash and cash equivalents, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short-term nature of these items.

Deferred Offering Costs

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. Upon completion of the IPO, approximately $2.4 million of deferred offering costs were offset against the IPO proceeds in additional paid-in capital.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and consist solely of computer equipment. Depreciation expense is recognized using the straight-line method over its estimated useful life of 3 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 nine months ended September 30, 2020.

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 5) 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 condensed consolidated statement 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 condensed consolidated balance sheet.

Stock-Based Compensation

The Company accounts for all stock-based payments to employees and non-employees, including grants of stock options, restricted stock awards (“RSAs”) and restricted stock units (“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 condensed consolidated statements of operations based upon the respective employee’s roles within the Company. Forfeitures are recorded as they occur.

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 sheet. 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 interim condensed 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, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the impact of this standard on its interim condensed consolidated financial statements.

Research, Collaboration and License Agreements

9 Months Ended

Sep. 30, 2020

Research Collaboration And License Agreements [Abstract]

Research, Collaboration and License Agreements

Note 4—Research, Collaboration 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 on behalf of The University of Texas 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 investigational new drug application-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 a right of first refusal for any shares that UT Southwestern wished to sell that expired upon the closing of the IPO.

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 issued 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 had not already been funded by the Company to Queen’s, would become a loan obligation for the Company (the “Note”), subject to an interest rate of 6%. For the nine months ended September 30, 2020, the Company paid all expenses associated with the Queen’s RGA, thus no amounts were due or outstanding under the Note as of September 30, 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 condensed consolidated statement of operations and included as an investing outflow in the statement 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 (also known as infantile Batten disease). Under the terms of the agreements, the Company made initial cash payments to Abeona of $3.0 million for the 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 condensed consolidated statement of operations since the acquired license or acquired inventory do not have an alternative future use, all of which was recorded in accounts payable as of September 30, 2020. 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.

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	9 Months Ended
	Sep. 30, 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)

Research, Collaboration and License Agreements - Additional Information (Details)	1 Months Ended				3 Months Ended	9 Months Ended
	Oct. 31, 2020 USD ($)	Aug. 31, 2020 USD ($)	Apr. 30, 2020 USD ($) Product	Dec. 31, 2019 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) 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	37,761,435	37,761,435
Research and development					$ 11,057,000	$ 19,633,000
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%
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%
Research grant outstanding fund amount					$ 0	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
Research and development						$ 7,000,000
Abeona CLN1 Agreements \| Subsequent Event
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Purchase of clinical materials and reimbursement incurred development costs	$ 4,000,000
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

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Issuance of shares of common stock in initial public offering, net of offering costs and underwriting discounts and commissions	$ 15,111	$ 15,111
Issuance of preferred stock tranche liability		1,050
Series A Convertible Preferred Stock
Issuance of convertible preferred stock, offering costs	165	605
Series B Convertible Preferred Stock
Issuance of convertible preferred stock, offering costs	$ 185	$ 185

Stock-Based Compensation - Schedule of Stock Option Activity, Excluding Cancelled Options (Details) - Stock Options $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted, Stock Options \| shares	185,342	185,342
Outstanding. Stock Options, Ending Balance \| shares	185,342	185,342
Vested and expected to vest at September 30, 2020, Stock Options \| shares	185,342	185,342
Options granted, Weighted Average Exercise Price \| $ / shares	$ 19.55	$ 19.55
Outstanding, Weighted Average Exercise Price, Ending balance \| $ / shares	19.55	19.55
Vested and expected to vest at September 30, 2020, Weighted Average Exercise Price \| $ / shares	$ 19.55	$ 19.55
Outstanding, Weighted Average Remaining Contractual Life		10 years
Options Granted, Weighted Average Remaining Contractual Life,		10 years
Vested and expected to vest at September 30, 2020, Weighted Average Remaining Contractual Life		10 years
Options granted, Aggregate Intrinsic Value \| $		$ 528
Outstanding, Aggregate Intrinsic Value, Ending Balance \| $	$ 528	528
Vested and expected to vest at September 30, 2020, Aggregate Intrinsic Value \| $	$ 528	$ 528

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)	3 Months Ended
	Sep. 30, 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	3,804,453
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	185,342

Supplemental Financial Information

9 Months Ended

Sep. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Supplemental Financial Information

Note 3—Supplemental Financial Information

Accrued expenses consisted of the following (in thousands):

	September 30, 2020		December 31, 2019
Accrued research and development	$	767	$	7
Accrued issuance costs		752		-
Accrued compensation		544		-
Accrued professional fees		462		122
Other		202		21
Total accrued expenses	$	2,727	$	150

Related Party Transactions - Additional Information (Details)	1 Months Ended
	Mar. 31, 2020 USD ($)	Jan. 31, 2020 USD ($) PromissoryNote	Sep. 30, 2020 USD ($)
Related Party Transaction [Line Items]
Due to related party			$ 60,000
PBM Capital Group, LLC \| Services Agreement
Related Party Transaction [Line Items]
Beneficial owner of greater than company’s common stock, percentage	5.00%
Accounting and other administrative and management services fee per month	$ 2,500
Due to related party			$ 60,000
RA Session II
Related Party Transaction [Line Items]
Number of secured promissory notes \| PromissoryNote		2
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%

Stock-Based Compensation - Additional Information (Details) - USD ($)					3 Months Ended	9 Months Ended
	Sep. 23, 2020	Sep. 16, 2020	Sep. 02, 2020	Jul. 01, 2020	Sep. 30, 2020	Sep. 30, 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
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 2 months 12 days
Share-based payment award, RSU/RSA granted						331,121
Share-based payment award, unvested RSU/RSA granted, compensation cost not yet recognized					$ 17,800,000	$ 17,800,000
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					185,342	185,342
Share-based payment award, options granted, exercise price per share					$ 19.55	$ 19.55
Share-based payment award, options, weighted-average grant date fair value						$ 13.73
Share-based payment award, options, compensation cost not yet recognized					$ 2,500,000	$ 2,500,000
Share-based payment award, compensation cost not yet recognized, weighted-average period of recognition						3 years 7 months 6 days
Stock Options \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period						3 years
Stock Options \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period						4 years
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						1 year 4 months 24 days
Share-based payment award, RSU/RSA granted						769,058
Share-based payment award, unvested RSU/RSA granted, compensation cost not yet recognized					3,700,000	$ 3,700,000
Share-based payment award, RSU/RSA granted, weighted average grant date fair value				$ 5.28		$ 5.28
Existing 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
Existing 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
Existing 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
Existing 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%
Existing 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%
Existing 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%
Existing 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%
Existing 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
Existing 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
Existing 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
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						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	169,000
Share-based payment award, options granted, exercise price per share	$ 20.00

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

9 Months Ended

Sep. 30, 2020

Equity [Abstract]

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

Note 5—Stockholders’ Equity (Deficit), Convertible Preferred Stock and Tranche Liability

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.

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 September 30, 2020, no shares of preferred stock were issued or outstanding.

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 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 condensed consolidated statement 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 $18.1 million to convertible preferred stock on the condensed consolidated balance sheet. 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 January 1, 2020	$	-
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 September 30, 2020	$	-