Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Line Items]
Deferred tax assets and valuation allowance increase during period	$ 8,600,000
Provision for income taxes	0	$ 0
Operating loss carryforwards, federal	466,000,000.0	452,400,000
Operating loss carryforwards, state	434,400,000	394,100,000
Legacy Millendo
Income Tax [Line Items]
Operating loss carryforwards, federal	455,800
Orphan Drug Credit
Income Tax [Line Items]
Tax credit carryforwards	7,400,000
Not Subject to Expiration
Income Tax [Line Items]
Operating loss carryforwards, federal	244,800,000
United States | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	11,700,000	10,200,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	3,600,000	$ 3,200,000
State and Local Jurisdiction | Not Subject to Expiration | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	$ 2,500,000