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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 |

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