Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (95,002)	$ (61,766)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	8,243	6,781
Depreciation	167	9
Amortization of debt discount and issuance costs	390	0
Acquisition of in-process research and development	0	13,117
Changes in the fair value of the Takeda warrant liability	0	28,815
Foreign currency translation adjustment	(231)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,058)	(1,153)
Deferred tax assets	208	0
Income tax receivable	(502)	(15)
Other assets	(2,098)	(100)
Accounts payable	(1,238)	549
Accrued expenses	8,838	2,912
Due to Roivant Sciences Ltd. and Roivant Sciences, Inc.	653	3,301
Deferred rent	259	0
Deferred interest payable	105	0
Net cash used in operating activities	(82,266)	(7,550)
Cash flows from investing activities:
Purchases of furniture and equipment	(375)	(369)
Net cash used in investing activities	(375)	(369)
Cash flows from financing activities:
Cash proceeds from issuance of common shares in initial public offering, net of underwriting discount	0	202,275
Initial public offering costs paid	0	(2,091)
Cash proceeds from debt financings, net of financing costs	28,803	0
Cash proceeds from issuance of common shares to NovaQuest, net of issuance costs	1,857	0
Cash capital contribution from Roivant Sciences Ltd.	0	1,036
Stock option exercises	16	0
Due to Roivant Sciences Ltd. and Roivant Sciences, Inc. for amounts paid on behalf of the Company	0	(979)
Net cash provided by financing activities	30,676	200,241
Net change in cash	(51,965)	192,322
Cash—beginning of period	180,838	0
Cash—end of period	128,873	192,322
Non-cash investing and financing activities:
Deferred initial public offering costs, unpaid	0	220
Acquisition of in-process research and development	0	13,117
Deferred financing costs, unpaid	137	0
Warrant issued to Hercules	$ 481	$ 0