Other Significant Agreements - Additional Information (Details)		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	63 Months Ended
	Nov. 06, 2018 USD ($) shares	Jan. 31, 2020 USD ($) shares	Nov. 30, 2015 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2020 USD ($) Milestone shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Feb. 01, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development				$ 30,640,000	$ 16,546,000	$ 60,653,000	$ 41,794,000
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock in connection with license agreement, shares | shares				177,318		177,318
Research Agreement | Series B Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expense recognized to estimate fair value of shares				$ 0		$ 0
MD Anderson Cancer Center | Patent and Technology License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining funding amount of patent-related costs under license agreement				800,000		$ 800,000
Number of days of prior written notice to terminate agreement						180 days
Number of milestones achieved | Milestone						0
Payments with respect to license agreement				0	$ 0	$ 0	$ 0
MD Anderson Cancer Center | Patent and Technology License Agreement | Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Obligated one-time payment based on acquisition or qualifying equity financing				20,000,000		20,000,000
Amount equal to or in excess of agreed upon price triggers equating to valuations				1,400,000,000		1,400,000,000
MD Anderson Cancer Center | Patent and Technology License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent future payments upon achievement of certain development and regulatory approval milestones			$ 11,900,000
Contingent payments in cash or through issuance of equity			4,400,000
Obligated one-time payment based on acquisition or qualifying equity financing				150,000,000		150,000,000
Amount equal to or in excess of agreed upon price triggers equating to valuations				5,800,000,000		$ 5,800,000,000
MD Anderson Cancer Center | Patent and Technology License Agreement | Maximum | Diagnostic Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent future payments upon achievement of certain development and regulatory approval milestones			2,400,000
MD Anderson Cancer Center | Patent and Technology License Agreement | Maximum | Therapeutic Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent future payments upon achievement of certain development and regulatory approval milestones			9,500,000
MD Anderson Cancer Center | Patent and Technology License Agreement | Scenario Forecast | Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Patent costs									$ 1,500,000
MD Anderson Cancer Center | Research Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research agreement extension of expiration year and month						2021-02
Research and development expense payment due year one			1,000,000
Research and development expense payment due year two through five			$ 1,250,000
Percentage of overhead charges on direct expenses			25.00%
Preferred stock shares issuable in year one under research agreement | shares			200,000
Preferred stock shares issuable in year two through five under research agreement | shares			20,833
Research agreement expiration date			Dec. 31, 2019
Research and development		$ 1,200,000
Research and development expense payment due				$ 0		$ 0
Preferred stock shares issuable under research agreement | shares				0		0
MD Anderson Cancer Center | Research Agreement | Series B Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock in connection with license agreement, shares | shares		62,500
MD Anderson Cancer Center | Research Agreement | Series B Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of shares of fair value estimated for research and development | shares					20,833		62,499
Expense recognized to estimate fair value of shares					$ 100,000		$ 300,000
Expenses for direct research and development expenses and overhead charges					$ 400,000		$ 1,200,000
Kayla Therapeutics S.A.S | Kayla License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development				$ 17,700,000		$ 17,700,000
Number of days of prior written notice to terminate agreement						30 days
Payments with respect to license agreement				0		$ 0
Non-refundable milestone payment in cash				15,000,000		$ 15,000,000
Upfront payment paid in cash	$ 6,500,000
Acquired in-process research and development expense								$ 8,100,000
Cash payment related to acquired in-process research and development								6,500,000
Royalty term determination period after first commercial sale of such product in such country						10 years
Number of days of notice to terminate agreement upon material breach						60 days
Kayla Therapeutics S.A.S | Kayla License Agreement | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued in consideration for license agreement | shares	118,212
Value of shares issued, acquired in process research and development								$ 1,600,000
Kayla Therapeutics S.A.S | Kayla License Agreement | Phase 1/2 Clinical Trial
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of milestones achieved | Milestone						0
Non-refundable milestone payment in cash				15,000,000		$ 15,000,000
Non-refundable milestone payment in common stock | shares						177,318
Milestone expense fair value of common stock issued				2,700,000		$ 2,700,000
Accrued milestone payment				$ 15,000,000		$ 15,000,000
Kayla Therapeutics S.A.S | Kayla License Agreement | Maximum | Phase 1/2 Clinical Trial
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Obligated to make cash payments upon achievement of clinical and regulatory milestones	$ 100,000,000
Value of common stock shares payable upon achievement of clinical and regulatory milestones	$ 13,000,000