License and Collaboration Agreements - Summary of Research and Development Costs Related to Collaboration and License Agreements (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs		$ 11,778	$ 12,496	$ 24,193	$ 16,669	[1]
Collaboration and License Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs		71	658	3,071	898
Collaboration and License Agreements | Cullinan Management - Adimab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs			214		318
Collaboration and License Agreements | Apollo - Wistar
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs			168		304
Collaboration and License Agreements | Pearl - Taiho
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs	$ 3,000			3,000
Collaboration and License Agreements | Amber - MIT
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs		$ 71	$ 276	$ 71	$ 276

[1] The shares and per share amounts for the six months ended June 30, 2020 were derived from the unaudited consolidated financial statements as of that date and were retroactively adjusted as a result of the Reorganization and Reverse Stock Split. See Note 3 to the unaudited consolidated financial statements for additional details.