Subsequent Events	12 Months Ended
Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Note 13—Subsequent Events License Agreement for CLN7 In March 2022, the Company entered into a license agreement with UT Southwestern to which the Company obtained an exclusive worldwide, royalty-bearing license with right to grant sublicenses to develop, manufacture, use, and commercialize licensed products for gene therapy for CLN7, a form of Batten Disease. In connection with the license agreement, the Company will pay a one-time up-front license fee of $0.3 million. The Company is obligated to pay UT Southwestern up to $7.7 million in regulatory-related milestones and up to $7.5 million in sales-related milestones, as well as a low, single-digit royalty on net sales upon commercialization of the product. TSHA-102 for the Treatment of Rett Syndrome In March 2022, the Company received a No Objection letter from Health Canada on the Company’s Clinical Trial Application (CTA) for TSHA-102 for treatment of Rett Syndrome. Strategic Prioritization In March 2022, the Company implemented changes to the Company’s organizational structure as well as a broader operational cost reduction plan to enable the Company to focus on specific clinical-stage programs for GAN and Rett syndrome. The Company will conduct small proof-of-concept studies in CLN1 disease and SLC13A5 deficiency. Development of the CLN7 program will continue in collaboration with existing partners with future clinical development to focus on the first-generation construct. All other research and development activities will be paused to increase operational efficiency. In connection with prioritization of programs, the Company reduced headcount by approximately 35% across all functions. The Company estimates that the severance and termination-related costs will total approximately $1.4 million and will be recorded in the first quarter of 2022. The Company expects that the payment of these costs will be substantially complete by the end of the second quarter of 2022. Equity Grants In January, February, and March 2022, the Company granted options to purchase an aggregate of 1,874,100 shares of its common stock at a weighted-average exercise price of $6.23 per share.

Subsequent Events

12 Months Ended

Dec. 31, 2021

Note 13—Subsequent Events

License Agreement for CLN7

In March 2022, the Company entered into a license agreement with UT Southwestern to which the Company obtained an exclusive worldwide, royalty-bearing license with right to grant sublicenses to develop, manufacture, use, and commercialize licensed products for gene therapy for CLN7, a form of Batten Disease. In connection with the license agreement, the Company will pay a one-time up-front license fee of $0.3 million. The Company is obligated to pay UT Southwestern up to $7.7 million in regulatory-related milestones and up to $7.5 million in sales-related milestones, as well as a low, single-digit royalty on net sales upon commercialization of the product.

TSHA-102 for the Treatment of Rett Syndrome

In March 2022, the Company received a No Objection letter from Health Canada on the Company’s Clinical Trial Application (CTA) for TSHA-102 for treatment of Rett Syndrome.

Strategic Prioritization

In March 2022, the Company implemented changes to the Company’s organizational structure as well as a broader operational cost reduction plan to enable the Company to focus on specific clinical-stage programs for GAN and Rett syndrome. The Company will conduct small proof-of-concept studies in CLN1 disease and SLC13A5 deficiency. Development of the CLN7 program will continue in collaboration with existing partners with future clinical development to focus on the first-generation construct. All other research and development activities will be paused to increase operational efficiency.

In connection with prioritization of programs, the Company reduced headcount by approximately 35% across all functions. The Company estimates that the severance and termination-related costs will total approximately $1.4 million and will be recorded in the first quarter of 2022. The Company expects that the payment of these costs will be substantially complete by the end of the second quarter of 2022.

Equity Grants

In January, February, and March 2022, the Company granted options to purchase an aggregate of 1,874,100 shares of its common stock at a weighted-average exercise price of $6.23 per share.