Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Cash flows from operating activities:
Net loss	$ (82,339)	$ (46,244)	$ (29,116)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	564	537	512
Stock-based compensation expense	11,086	7,118	4,448
Realized loss (gain) from sale of marketable securities	581	(153)	(300)
Non-cash operating lease expense	179	114	13
Amortization of premium on available for sale securities	2,565	685	193
Foreign currency exchange loss (gain)	1,552	(574)	74
Changes in operating assets and liabilities:
Research and development tax credit receivable	(5,201)	7,457	(5,781)
Prepaid expenses and other assets	(9,280)	(244)	(1,117)
Accounts payable	1,687	150	(1,004)
Accrued expenses	472	983	(48)
Deferred revenue			(12,690)
Net cash used in operating activities	(78,134)	(30,171)	(44,816)
Cash flows from investing activities:
Purchases of available for sale securities	(136,920)	(201,210)	(49,797)
Sales and maturities of available for sale securities	195,711	53,638	66,770
Acquisition of property and equipment	(931)	(82)	(220)
Net cash provided by (used in) investing activities	57,860	(147,654)	16,753
Cash flows from financing activities:
Issuance of common stock, net of offering expenses		210,582	11,422
Issuance of common stock from equity incentive plans	1,581	1,535	216
Finance lease principal payments			(54)
Net cash provided by financing activities	1,581	212,117	11,584
Effect of exchange rate changes on cash and cash equivalents	(1,167)	511	262
Net (decrease) increase in cash and cash equivalents	(19,860)	34,803	(16,217)
Cash and cash equivalents, beginning year	50,592	15,789	32,006
Cash and cash equivalents, end of year	30,732	50,592	15,789
Supplemental disclosures of cash flow information:
Right of use assets obtained in exchange for operating lease liabilities	3,185	$ 4,784	$ 309
Property and equipment included in accounts payable and accrued expenses:	$ 149