Leases - Narrative (Details)			3 Months Ended			9 Months Ended
	Nov. 30, 2022 USD ($)	Nov. 01, 2022 USD ($) lease	Jan. 31, 2023 USD ($)	Jan. 31, 2022 USD ($)	Jul. 31, 2020 USD ($)	Jan. 31, 2023 USD ($)	Jan. 31, 2022 USD ($)	Apr. 30, 2022 USD ($)	Oct. 01, 2021 USD ($)	Apr. 01, 2021 USD ($)	Jun. 01, 2020 USD ($)	Mar. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases, rent expense			$ 475,000	$ 469,000		$ 1,400,000	$ 1,400,000
Extension term												6 months
Operating lease right-of-use assets, net			7,590,000			7,590,000		$ 8,230,000
Operating lease, liability			$ 8,869,000			$ 8,869,000
Weighted average remaining lease term (in years)			5 years 11 months 15 days			5 years 11 months 15 days
Weighted average discount rate, percent			5.82%			5.82%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense			$ 20,000	24,000		$ 62,000	70,000
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense			422,000	422,000		1,300,000	1,300,000
Operating lease right-of-use assets, net					$ 118,000						$ 3,800,000
Operating lease, liability					125,000						$ 3,800,000
Incremental rent expense					$ 8,000
Additional Expansion Premises
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net										$ 3,300,000
Operating lease, liability										$ 3,300,000
Milan Italy
Lessee, Lease, Description [Line Items]
Operating leases, rent expense			34,000	$ 23,000		$ 81,000	$ 58,000
Operating lease right-of-use assets, net		$ 231,000							$ 205,000
Operating lease, liability		$ 231,000							$ 205,000
Number of leases replaced | lease		2
Milan Italy Office Space Lease
Lessee, Lease, Description [Line Items]
Right-of-use asset, decrease for lease termination	$ 40,700
Lease liability, decrease for lease termination	41,500
Gain (loss) on termination of lease	$ 1,000
Milan Italy Laboratory Lease
Lessee, Lease, Description [Line Items]
Right-of-use asset, decrease for lease termination			20,000
Lease liability, decrease for lease termination			$ 20,000