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Related party transaction expenses from transactions with related party advisory fees.

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Research and development service agreement aggregate payment.

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Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2015	Dec. 31, 2020
Related Party Transaction [Line Items]
Research and development expense	$ 14,521	$ 13,968	$ 41,427	$ 38,725
Accrued expenses	13,963		13,963			$ 16,589
M.D. Anderson Cancer Center
Related Party Transaction [Line Items]
Due from Related Parties, Current	1,100		1,100			4,700
Accrued expenses	2,100		2,100			$ 1,400
MD Anderson License and the Research and Development Agreement [Member]
Related Party Transaction [Line Items]
Cash resources on hand	0		0
License Agreement \| M.D. Anderson Cancer Center
Related Party Transaction [Line Items]
Issuance of common stock in licensing agreement (in shares)					11,722,163
Research and development expense					$ 67,300
Cooperative Research and Development Agreement \| M.D. Anderson Cancer Center
Related Party Transaction [Line Items]
Research and development service agreement aggregate payments			41,900
Vineti Inc [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Related Party Transaction Expenses From Transactions With Related Party Advisory Fees	$ 100		400
Eden Biocell [Member]
Related Party Transaction [Line Items]
Payments to Fund Long-term Loans to Related Parties			$ 10,000