Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment Institution	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Accounting Policies
Number of operating segments | segment			1
Number of financial institutions | Institution			2
Operating lease right-of-use asset	$ 1,054		$ 1,054
Operating lease liability, net of current portion	899		899
Charges incurred			0
Uncertain tax positions	0		0		$ 0	$ 0
Prepaid expenses research and development	$ 2,800		$ 2,800		$ 600
Practical Expedient, Financing Component			true
Employees
Accounting Policies
Stock options, vesting period			4 years
Board of Director
Accounting Policies
Stock options, vesting period			1 year
Minimum
Accounting Policies
Equipment depreciation period			3 years
Maximum
Accounting Policies
Equipment depreciation period			5 years
BioCryst
Accounting Policies
Fixed expense reimbursement		$ 6,000
Exton Facility
Accounting Policies
Term of lease commitment (years)	5 years		5 years
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Operating lease right-of-use asset				$ 300