Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		6 Months Ended
		Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss		$ (83,251)	$ (99,922)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation		23,125	14,736
Depreciation and amortization	[1]	1,536	1,146
Non-cash interest expense		1,210	0
Foreign currency transaction gain		0	(10,287)
Other		0	393
Changes in operating assets and liabilities:
Accounts receivable		(10,832)	0
Inventories		(3,530)	0
Prepaid expenses and other current assets		(4,414)	2,657
Other assets		1,798	(648)
Accounts payable		(9,519)	(8,326)
Interest payable (related party)		0	(15)
Accrued expenses and other current liabilities		1,722	11,081
Deferred revenue		28,652	(23,333)
Amounts due to Pfizer		18,003	0
Cost share advance from Pfizer		(38,304)	0
Operating lease liabilities		(869)	(728)
Amounts due to related parties		(209)	1,284
Other liabilities		(1,696)	1,386
Net cash used in operating activities		(76,578)	(110,576)
Cash flows from investing activities:
Purchases of marketable securities		(94,448)	(28,874)
Maturities of marketable securities		7,035	14,785
Purchases of property and equipment		(361)	(734)
Net cash used in investing activities		(87,774)	(14,823)
Cash flows from financing activities:
Proceeds from related party debt financing		0	140,000
Proceeds from stock option exercises		15,135	3,578
Net cash provided by financing activities		15,135	143,578
Net change in cash, cash equivalents and restricted cash		(149,217)	18,179
Cash, cash equivalents and restricted cash, beginning of period		677,480	78,018
Cash, cash equivalents and restricted cash, end of period		528,263	96,197
Non-cash financing activities:
Change in fair value of share-based awards recorded to additional paid-in capital		2,292	0
Equipment purchases included in accounts payable		352	0
Reclassification of share-based compensation liabilities to additional paid-in capital upon settlement of awards		18,159	0
Stock options exercised receivable, included in prepaid expenses and other current assets		$ 162	$ 0

[1] Includes amortization of operating lease right-of-use assets.