Licenses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
University of Alabama at Birmingham Research Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual license fee	$ 20,000
Type of Cost, Good or Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
License fee costs	$ 20,000	$ 20,000
Patent expiration date	Aug. 07, 2033
Janssen Vaccines and Prevention BV [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual license fee	$ 100,000
Type of Cost, Good or Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
License fee costs	$ 177,625	$ 200,000
Patent expiration date	Mar. 21, 2020
Auburn University [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual license fee	$ 5,000
Type of Cost, Good or Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Patent expiration date	Aug. 15, 2025
License fee costs	$ 5,000	$ 5,000
Upfront fee	$ 1,000