Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss		$ (205,981)	$ (255,134)	$ (288,989)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Share-based compensation		38,928	53,676	40,251
Depreciation		1,378	988	673
Non-cash interest expense	[1]	2,413	635	1,486
Loss on extinguishment of debt		0	0	4,851
Foreign currency transaction gain		0	(16,176)	(1,621)
Amortization of operating lease right-of-use assets		1,694	1,491	1,092
Other		10	537	(359)
Changes in operating assets and liabilities:
Accounts receivable		(19,726)	(3,570)	0
Inventories		(4,973)	(2,611)	0
Prepaid expenses and other current assets		(8,962)	(5,267)	1,925
Amount due from related party		(580)	0	0
Income tax receivable		0	0	524
Other assets		(6,421)	(1,441)	(10)
Accounts payable		(5,617)	2,457	4,315
Interest payable		0	0	(1,077)
Accrued expenses and other current liabilities		23,982	15,552	(24,675)
Deferred revenue		(21,663)	457,933	40,000
Amounts due to Pfizer		30,609	1,954	0
Cost share advance from Pfizer		(90,457)	121,227	0
Operating lease liabilities		(1,807)	(1,516)	(882)
Deferred interest payable		0	0	(2,273)
Amounts due to related parties		(150)	528	15
Other liabilities		(1,236)	(635)	3,582
Net cash (used in) provided by operating activities		(268,559)	370,628	(221,172)
Cash flows from investing activities:
Purchases of marketable securities		(118,748)	(63,824)	(32,076)
Maturities of marketable securities		101,700	33,261	29,240
Sales of marketable securities		0	23,125	0
Purchases of property and equipment		(974)	(1,773)	(1,099)
Net cash used in investing activities		(18,022)	(9,211)	(3,935)
Cash flows from financing activities:
Capital contribution -other		1,280	0	0
Proceeds from issuance of common shares, net of issuance costs paid		0	0	137,004
Proceeds from related party debt financing		0	245,000	113,700
Proceeds from stock option exercises		24,625	6,709	942
Payment of tax withholding on net settlement of share awards		0	(13,664)	0
Payment of third-party debt financings and redemption and administration fees		0	0	(105,720)
Net cash provided by financing activities		25,905	238,045	145,926
Net change in cash, cash equivalents and restricted cash		(260,676)	599,462	(79,181)
Cash, cash equivalents and restricted cash, beginning of period		677,480	78,018	157,199
Cash, cash equivalents and restricted cash, end of period		416,804	677,480	78,018
Supplemental Disclosure of Non-Cash Financing and Investing Information:
Reclassification of share-based compensation awards from additional paid-in capital to current liabilities		0	17,473	0
Change in fair value of share-based awards recorded to additional paid-in capital		1,699	10,609	0
Reclassification of share-based compensation liabilities to additional paid-in capital upon settlement or maturity of awards		23,335	6,446	0
Equipment purchases included in accounts payable		58	18	0
Supplemental Disclosure of Cash Flow Information:
Income taxes paid		3,542	513	38
Interest paid		0	0	13,030
Interest (related party) paid		$ 11,551	$ 9,819	$ 1,426

[1] Includes imputed interest on cost share advance from Pfizer for the years ended March 31, 2022 and 2021. Includes amortization of debt discount and issuance costs for the year ended March 31, 2020.