Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company's mission description			The Company’s mission is to cure Duchenne muscular dystrophy (“Duchenne”), a genetic muscle-wasting disease predominantly affecting boys.
Medicine description			In March 2022, the Company reported two-year interim safety and efficacy data from the first three patients treated with SGT-001 in the 2E14 vg/kg dose cohort of IGNITE DMD, which results suggested durable benefit compared with natural history trajectories 24 months post-administration of SGT-001 across functional, pulmonary and patient reported outcome measures. In addition, no new drug-related safety findings have been identified in patients treated with SGT-001 in IGNITE DMD in post-dosing periods of approximately six months to four years. In April 2022, the Company announced that it had concluded enrollment in IGNITE DMD.
Development activity description			Development activities, including manufacturing scale-up, testing and regulatory discussions with the Food and Drug Administration (FDA) are ongoing. The company expects to continue dosing patients using SGT-001 in 2023 with product made using the new transient-based process. The company also expects to share additional data from IGNITE DMD in early 2023, including the study’s primary one-year analysis of all treated patients as well as three-year longitudinal data from Patients Four through Six.
Net loss	$ 25,092	$ 18,695	$ 50,420	$ 35,595
Accumulated deficit	527,177		527,177		$ 476,757
Net cash used in operating activities			43,068	$ 38,466
Cash, Cash Equivalents, and Short-Term Investments	$ 162,883		$ 162,883