License Agreements - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
License Agreements [Line Items]
Research and development		$ 30,911,000	$ 15,455,000
Duke University
License Agreements [Line Items]
Sale of licensed products or services		0
Fees payment		300,000
Nonroyalty payment received		1,000,000
Wacker
License Agreements [Line Items]
Research and development		200,000
Maximum | Achievement of Clinical Development and Regulatory Milestones | Duke University
License Agreements [Line Items]
Milestone payments		2,200,000
Maximum | Commercial Milestones | Duke University
License Agreements [Line Items]
Milestone payments		400,000
Minimum | Duke University
License Agreements [Line Items]
Aggregate royalties payment		200,000
MedImmune Limited
License Agreements [Line Items]
License agreement upfront payment				$ 100,000
Milestone payments		$ 1,000,000
MedImmune Limited | Maximum | Achievement of Clinical Development and Regulatory Milestones
License Agreements [Line Items]
Milestone payments	$ 18,000,000
MedImmune Limited | Maximum | Commercial Milestones
License Agreements [Line Items]
Milestone payments	$ 50,000,000