Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax [Line Items]
Provision for income taxes	$ 0	$ 0
Operating loss carryforwards, federal	482,100,000	466,000,000
Operating loss carryforwards, state	457,800,000	434,400,000
Increase in valuation allowance	9,100,000
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	260,900,000
United States | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	12,700,000	11,700,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	4,000,000	$ 3,600,000
State and Local Jurisdiction | Not Subject to Expiration | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	$ 2,900,000