CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (379,541)	$ (186,172)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash share-based compensation expense	34,855	12,438
Non-cash interest expense on mandatorily redeemable preferred shares	8,333	0
Non-cash interest expense on liability related to sale of future royalties	19,272	6,134
Non-cash expense related to license agreement	5,646	4,080
Change in fair value of derivative liability	2,980	0
Change in fair value of warrant liability	0	1,182
Loss from equity method investment	4,308	2,066
Other non-cash items	437	91
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,494	(9,598)
Other assets	(340)	(32)
Accounts payable	810	(63)
Accrued expenses	26,862	5,521
Other long-term liabilities	(2,000)	628
Net cash used in operating activities	(276,884)	(163,725)
Cash flows from investing activities:
Purchases of property and equipment	(1,637)	(2,634)
Purchase of equity method investment	0	(1,375)
Net cash used in investing activities	(1,637)	(4,009)
Cash flows from financing activities:
Proceeds from issuance of common shares	303,221	55,000
Proceeds from sale of future royalties	0	106,047
Proceeds from issuance of common stock related to sale of future royalties	0	43,953
Proceeds from issuance of mandatorily redeemable preferred shares	125,000	0
Proceeds from exercise of warrants	1,998	0
Payments of issuance costs	(1,150)	(2,987)
Proceeds from exercise of stock options	2,777	2,438
Net cash provided by financing activities	431,846	204,451
Net increase in cash and restricted cash	153,325	36,717
Cash and restricted cash at beginning of period	264,249	131,468
Cash and restricted cash at end of period	417,574	168,185
Supplemental disclosure of cash flow information:
Cash paid for interest	0	0
Cash paid for income taxes	835	273
Supplemental disclosure of non-cash investing and financing activities:
Offering costs included in accounts payable and accrued expenses	$ 0	$ 377