License Agreements - Additional Information (Details)	1 Months Ended		3 Months Ended
	Nov. 30, 2017 USD ($)	Feb. 01, 2016	Mar. 31, 2019 USD ($) Milestone	Dec. 31, 2018 USD ($)
Duke University
License Agreements [Line Items]
Sublicensable agreement term		20 years
Sale of licensed products or services			$ 0
Fees payment			300,000
Nonroyalty payment received			$ 1,000,000
Nonroyalty agreement term			The Company must pay Duke the first $1.0 million of non-royalty payments it receives from a sublicensee, and thereafter a specified percentage of any additional nonroyalty payments it receives. If Duke receives revenue as a result of a license or sublicense to a third-party in the field of small-molecule oncologics, it will pay the Company a specified percentage of the amount of such revenue in excess of $0.1 million.
Maximum | Achievement Of Clinical Development And Regulatory Milestones | Duke University
License Agreements [Line Items]
Potential milestones payment			$ 2,200,000
Maximum | Commercial Milestones | Duke University
License Agreements [Line Items]
Potential milestones payment			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
Number of milestones met | Milestone			0
Reimbursement of costs incurred to product storage costs				$ 500,000
MedImmune Limited | Maximum | Achievement Of Clinical Development And Regulatory Milestones
License Agreements [Line Items]
Potential milestones payment	18,000,000
MedImmune Limited | Maximum | Commercial Milestones
License Agreements [Line Items]
Potential milestones payment	$ 50,000,000