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Sponsored Research, Collaboration and License Agreements - Additional Information (Details)	1 Months Ended					3 Months Ended		9 Months Ended
	Nov. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) Installment	Aug. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Milestone	Sep. 30, 2020 USD ($)
Sponsored Research, Collaboration and License Agreements [Line Items]
Research and development expense						$ 33,062,000	$ 17,182,000	$ 79,132,000	$ 32,906,000
CPRIT \| Non-commercial License Agreement
Sponsored Research, Collaboration and License Agreements [Line Items]
Maximum paid percentage of grant award proceeds until which revenue share is payable				400.00%
Royalty payments								0	0
CPRIT \| Grant
Sponsored Research, Collaboration and License Agreements [Line Items]
Revenue from grant				$ 9,000,000.0
Period of grant				3 years
Percentage of obligation of grant funds used				50.00%
Cost incurred to obtain or fulfill the contract				$ 0
Grant funds received returned amount		$ 2,600,000
Interest relating to grant funds returned		100,000
Deferred revenue balance		$ 0
A&R License Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Non-refundable license fee payments					$ 250,000
Milestone payments								$ 40,000,000.0
Minimum percentage of eligible to receive tiered royalties						1.00%		1.00%
Second License Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Non-refundable license fee payments	$ 125,000
Milestone payments								$ 30,000,000.0
Minimum percentage of eligible to receive tiered royalties						1.00%		1.00%
Non-refundable license fee payments, first year through fourth anniversary of effective date								$ 20,000
Non-refundable license fee payments fifth anniversary of effective date and continuing thereafter								40,000
SRA-2 \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Agreement for research activities, term			1 year
Agreement for research activities, additional term with written consent			1 year
Research activities performing fees			$ 1,000,000.0
Number of installment for research activities payments \| Installment			4
Research Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Agreement for research activities, term	3 years
Research activities performing fees	$ 2,000,000.0
Total research activities performing fees, over the term	$ 6,000,000.0
Collective Agreements \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Research and development expense						$ 700,000	$ 100,000	2,800,000	$ 900,000
Collective Agreements \| BCM \| Accrued Expenses
Sponsored Research, Collaboration and License Agreements [Line Items]
Accrued milestone expenses						$ 200,000		$ 200,000
Number of milestone events \| Milestone								3