CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (186,172)	$ (100,108)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	12,438	10,805
Non-cash interest expense	0	784
Non-cash interest expense on liability related to sale of future royalties	6,134	0
Non-cash expense related to license agreement	4,080	0
Change in fair value of warrant liability	1,182	5,509
Change in fair value of derivative liability	0	(512)
Change in fair value of contingent equity liability	0	13,082
Loss from equity method investment	2,066	1,204
Other non-cash items	91	50
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(9,598)	(3,282)
Deferred tax assets	0	9
Other assets	(32)	0
Accounts payable	(63)	7,978
Accrued expenses	5,521	10,371
Other long-term liabilities	628	62
Net cash used in operating activities	(163,725)	(54,048)
Cash flows from investing activities:
Purchases of property and equipment	(2,634)	(253)
Purchase of equity method investment	(1,375)	(2,999)
Net cash used in investing activities	(4,009)	(3,252)
Cash flows from financing activities:
Proceeds from issuance of common shares	55,000	179,996
Proceeds from sale of future royalties	106,047	0
Proceeds from issuance of common stock related to sale of future royalties	43,953	0
Proceeds from issuance of Series A preferred shares	0	40,000
Payments of related party notes payable	0	(595)
Repayment of notes payable	0	(5,000)
Payments of issuance costs	(2,987)	(5,039)
Proceeds from exercise of stock options	2,438	0
Net cash provided by financing activities	204,451	209,362
Net increase in cash	36,717	152,062
Cash at beginning of period	131,468	23,692
Cash at end of period	168,185	175,754
Supplemental disclosure of cash flow information:
Cash paid for interest	0	122
Cash paid for income taxes	273	450
Supplemental disclosure of non-cash investing and financing activities:
Offering costs included in accounts payable and accrued expenses	377	29
Beneficial conversion feature on Series A preferred shares	0	12,006
Accretion of beneficial conversion feature on Series A preferred shares	0	12,006
Issuance of Series A preferred shares as payment of offering costs	0	1,242
Issuance of common shares as payment of equity investment	$ 0	$ 352