Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	$ 1,900	$ 1,900
Operating lease right-of-use assets, net	7,318	8,230
Present value of minimum lease payments	8,599
Operating lease right-of-use assets	952	786
Operating lease liabilities	$ (907)	(631)
Weighted average remaining lease term	5 years 8 months 12 days
Weighted average discount rate	5.82%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	$ 83	88
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	1,700	1,700
Milan, Italy
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	98	$ 81
Operating lease right-of-use assets, net	231
Present value of minimum lease payments	231
Milan, Italy (Office Space)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	41
Operating lease liabilities	41
Milan, Italy (Laboratory Space)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	20
Operating lease liabilities	$ 20