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Sponsored Research, Collaboration and License Agreements - Additional Information (Details)	1 Months Ended					3 Months Ended		6 Months Ended
	Nov. 30, 2020 USD ($)	May 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) Installment	Aug. 31, 2017 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) Milestone	Jun. 30, 2020 USD ($)
Sponsored Research, Collaboration and License Agreements [Line Items]
Research and development expense						$ 25,677,000	$ 8,885,000	$ 46,070,000	$ 15,724,000
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						$ 1,200,000	$ 500,000	2,100,000	$ 800,000
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