Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended			12 Months Ended
	Dec. 31, 2019	May 31, 2018	Apr. 30, 2018	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Lessee, operating lease, description		The Company amended the lease term to expire in April 2022, with an option to renew for an additional 12 months.
Operating lease, payments		$ 4,200
Lessee, operating lease term of contract		12 months
Operating leases, rent expense				$ 290,000	$ 273,000
Teva Agreements
Loss Contingencies [Line Items]
Nonrefundable upfront payment			$ 6,000,000.0
Payment upon achievement of certain clinical and commercial milestones			135,000,000.0
Asset transfer and license agreement, termination period after written notice				120 days
Asset transfer and license agreement, termination period notice of breach				60 days
Asset transfer and license agreement termination notice period if bankruptcy petition filed				60 days
Teva Agreements | Research and Development Expenses
Loss Contingencies [Line Items]
Milestone payments				$ 0	0
Teva Agreements | Teva's GlycoPEGylated FGF21 Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones			67,500,000
Teva Agreements | Teva's Development Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones			$ 67,500,000
Restricted Cash And Other Assets Member
Loss Contingencies [Line Items]
Security deposit				$ 95,000	95,000
San Francisco Office
Loss Contingencies [Line Items]
Lessee, operating lease, description	with a lease term that was due to expire in January 2022. In July 2021, the Company amended the lease agreement to extend the term of the lease to January 2023, with an option to renew the term for one year.
Operating lease, payments					$ 18,000
Lessee,operating lease, renewal term				1 year