License and Purchase Agreements - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2025	Feb. 28, 2025	Nov. 30, 2024	Apr. 30, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2016
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential Additional Cash Receipt					$ 65,000		$ 65,000
Research and development					5,011	$ 6,554	15,418	$ 24,961
Collaboration revenue					0	$ 602	0	$ 4,214
Kaken License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments				$ 15,000			15,000
Allievex Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Consideration paid			$ 5,000
Consideration assumed as certain liabilities							8,400
Contingent consideration paid							7,200
Consideration assumed as accrued expenses and other current liabilities					1,200		1,200
Estimated receivable					2,600		2,600
Transaction costs							300
Aggregate net acquisition cost							11,100		$ 15,100
Sales milestones					100,000		100,000
Allievex Purchase Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development and regulatory milestones					88,000		88,000
Allievex Purchase Agreement \| Maximum \| MPSIIIB
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development and regulatory milestones					25,500		25,500
HBM Alpha Therapeutics, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments		$ 5,000
Development and regulatory milestones					390,000		390,000
Payments to acquire in process research and development							5,000
Fair value of pre-funded warrants issued							700
Percentage of issued pre-funded warrants	4.99%
Pre-funded warrants, expiration period	Dec. 31, 2025
Eli Lilly And Company [Member] \| Lilly License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential Additional Payment					$ 23,000		23,000
Research and development arrangement, costs incurred							$ 0
Research and development										$ 800

SPRUCE BIOSCIENCES, INC. 10-Q