Significant Agreements – Related Parties (Details) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 24, 2020	Jul. 23, 2019	Sep. 30, 2021	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2023
Related Party Transaction [Line Items]
Research and development				$ 15,900,000	$ 6,900,000	$ 43,700,000	$ 20,100,000
Current liabilities				14,481,000		14,481,000			$ 15,085,000
Prepaid expenses and other assets				756,000		756,000			633,000
Other assets				2,115,000		2,115,000			2,094,000
Related Party
Related Party Transaction [Line Items]
Research and development				2,310,000	2,271,000	7,400,000	6,511,000
Accrued expenses and other current liabilities				1,801,000		1,801,000			3,561,000
Accounts payable				431,000		431,000			1,044,000
Master Services Agreement | Related Party
Related Party Transaction [Line Items]
Research and development				0	0	0	0
Accrued expenses and other current liabilities				0.0		0.0			1,600,000
BBL Agreements | Related Party
Related Party Transaction [Line Items]
Research and development				700,000	300,000	1,100,000	700,000
Accrued expenses and other current liabilities				1,100,000		1,100,000			1,700,000
Related party agreement, term		5 years
Syngene Agreement, Manufacturing | Related Party
Related Party Transaction [Line Items]
Related party agreement, term		6 years
Syngene Agreement, Master Contract Services | Related Party
Related Party Transaction [Line Items]
Related party agreement, term	2 years
Syngene Agreements | Related Party
Related Party Transaction [Line Items]
Research and development				2,000,000.0	$ 1,600,000	6,300,000	$ 5,800,000
Accrued expenses and other current liabilities				800,000		800,000			1,900,000
Current liabilities				1,200,000		1,200,000			2,900,000
Accounts payable				$ 400,000		$ 400,000			1,000,000.0
Biofusion Agreement | Related Party
Related Party Transaction [Line Items]
Research and development								$ 4,100,000
Accrued expenses and other current liabilities								$ 7,700,000
Promissory Note | Chief Financial Officer
Related Party Transaction [Line Items]
Promissory note loan amount			$ 274,000
Interest rate			0.86%
Number of shares pledged as collateral (in shares)			616,320
Prepaid expenses and other assets									68,000
Other assets									$ 68,000