License and collaboration agreements - Additional Information (Detail) - USD ($)		1 Months Ended					3 Months Ended			6 Months Ended		11 Months Ended	12 Months Ended
	Jun. 25, 2020	Mar. 31, 2024	Jan. 31, 2022	Dec. 31, 2020	Jun. 30, 2020	Apr. 30, 2020	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2019	Dec. 19, 2018	Jun. 30, 2018
Revenue recognized from collaborative arrangements							$ 0		$ 0
Revenue recognized from collaborative arrangements on upfront payment										$ (292,000)	$ (5,175,000)
KU Leuven [Member]
Collaboration expire period	2 years 6 months
Katholieke Universiteit Leuven [Member]
Payments for royalties and milestones							0			$ 0
Emory license agreement [Member] | Emory university [Member]
Non-refundable payment					$ 200,000
Long term purchase commitment additional obligation to be paid					35,000
Long term purchase commitment period description										The research plan was set to terminate one year from the effective date of June 2020 but the Company exercised its option to extend it for a second year
Royalties or milestones payments made							0		0	$ 0	0
Payments for royalties							0		0	0	0
Expense or accruals recognized related to royalties							0		0	0	0
Emory license agreement [Member] | Emory university [Member] | Maximum [Member]
Funding related to collaboration agreement extension					$ 300,000
Aggregate payments																	$ 125,000,000.0
Luxna license agreement [Member] | Luxna biotech Co Ltd [Member]
Royalties or milestones payments made							0		0	0	0
Payments for royalties							0		0	$ 0	0
Luxna license agreement [Member] | Luxna biotech Co Ltd [Member] | Maximum [Member]
Aggregate payments																$ 55,500,000
Katholieke Universiteit Leuven License Agreement [Member] | Katholieke Universiteit Leuven [Member]
Non-refundable payment	$ 30,000,000.0
Long term purchase commitment period description										Unless terminated earlier by either party, the agreement shall continue until the expiration of the last to expire royalty term, which is the later of the expiration or termination of the last valid patent claim covering the manufacture, use, sale or importation of the licensed product in a particular country or 10 years after the first commercial sale of a licensed product.
First commercial sale of a licensed product period	10 years
Katholieke Universiteit Leuven License Agreement [Member] | Katholieke Universiteit Leuven [Member] | Maximum [Member]
Non-refundable payment	$ 32,000,000.0
Merck License and Research Collaboration | Merck
Upfront payment received			$ 15,000,000	$ 12,000,000
Merck License and Research Collaboration | Merck | Maximum [Member]
Milestone payments and royalties receivable			$ 460,000,000	$ 458,000,000
Merck License and Research Collaboration First Amendment [Member] | Merck
Revenue recognized from collaborative arrangements							0		0	$ 0	$ 0
Revenue recognized from collaborative arrangements on upfront payment							$ 300,000		$ 5,200,000
Research and Development [Member] | Luxna license agreement [Member] | Luxna biotech Co Ltd [Member]
Upfront license fees paid												$ 600,000			$ 600,000
Non-refundable payment						$ 200,000
Grant by the National Institute of Health (NIH) for Research to Target Coronaviruses
Government grants / contract awarded										$ 1,500,000			$ 1,400,000	$ 1,100,000
Grant by the National Institute of Allergies and Infectious Diseases (NIAID) for Research to Target Coronaviruses
Government grants / contract awarded		$ 1,300,000						$ 9,800,000					$ 8,500,000
Government contract end year								2026