Income Taxes - Summary of Changes in the Valuation Allowance for Deferred Tax Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes Disclosure [Line Items]
Valuation allowance as of the beginning of the year	$ 115,319	$ 11,735
Increases recorded to income tax provision	8,697	17,895
Valuation Allowance at end of Year	$ 124,016	115,319
Zafgen [Member]
Income Taxes Disclosure [Line Items]
Increases acquired as a result of the Merger with Zafgen		$ 85,689