Collaboration Agreements - Additional Information (Details)			1 Months Ended	3 Months Ended
	Jun. 17, 2020 USD ($) Target	Jan. 02, 2019 USD ($) Target Candidate Obligation	Apr. 30, 2021 Target	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 23, 2020 USD ($)
Collaboration Agreements [Line Items]
Number of performance obligations | Obligation		8
Total collaboration revenue				$ 13,191,000	$ 134,000
Deferred revenue				50,353,000
Up-front and non-refundable cash payments received				66,000,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited
Collaboration Agreements [Line Items]
Number of oncogene targets | Target		5
Number of targets | Target		4
Number of clinical trial candidates | Candidate		2
Number of remaining candidates | Candidate		3
Additional milestone payment related to regulatory approval of product		$ 20,000,000
Up-front payment		56,000,000
Preclinical development milestone payments eligible to receive		20,000,000
Collaboration target payment receivable due upon second initiation		10,000,000
Milestone payments eligible to receive		$ 200,000,000
Notice period for termination of agreement		180 days
Collaboration arrangement transaction price measured based on non-refundable and non creditable up-front payment				56,000,000
Variable consideration payable included in transaction price at inception				0
Remaining consideration comprised solely of transaction price							$ 55,000,000
Changes in estimate of variable consideration				0
Material rights outstanding either exercised or expired				0
Total collaboration revenue				100,000	11,600,000
Deferred revenue				43,400,000		$ 55,000,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Research and Development
Collaboration Agreements [Line Items]
Cost associated with obligations under arrangement				700,000	700,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Development and Commercialization License and Associated Research Services | ASU 2014-09
Collaboration Agreements [Line Items]
Option to include additional target additional cost		$ 0
Replacement target additional cost		0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Research Services | ASU 2014-09
Collaboration Agreements [Line Items]
Option to request additional research program additional cost		0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Non-GLP Toxicology Studies | ASU 2014-09
Collaboration Agreements [Line Items]
Per backup development candidate cost upon exercise		$ 0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | License and Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied				40,000,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | All Other Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied				4,100,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Subsequent Event
Collaboration Agreements [Line Items]
Number of oncogene targets discontinue work | Target			1
Sarepta Research Agreement
Collaboration Agreements [Line Items]
Up-front payment	$ 7,000,000
Milestone payments eligible to receive	$ 192,500,000
Material rights outstanding either exercised or expired				0
Total collaboration revenue				1,600,000	0
Deferred revenue				7,000,000
Research agreement period	2 years
Number of agreed targets | Target	5
Term of option exercise	Jun. 17, 2022
Extended term of option exercise	Dec. 17, 2022
Up-front and non-refundable cash payments received	$ 10,000,000
Up-front research services prepayment	3,000,000
Collaboration arrangement obligated to remit option exercise payment	12,500,000
Collaboration arrangement obligated options exercised	$ 62,500,000
Additional term of agreement	2 years
Sarepta Research Agreement | Research and Development
Collaboration Agreements [Line Items]
Cost associated with obligations under arrangement				1,600,000	$ 0
Sarepta Research Agreement | ASU 2014-09
Collaboration Agreements [Line Items]
Up-front payment	$ 7,000,000
Up-front research services prepayment	3,000,000
Aggregate transaction price	18,000,000
Estimation of cost reimbursements	$ 8,000,000
Sarepta Research Agreement | All Other Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied				7,000,000
Sarepta Research Agreement | Research License and Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied				$ 7,200,000