CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (124,731)	$ (57,193)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	8,696	4,549
Non-cash interest expense	0	569
Non-cash interest expense on liability related to sale of future royalties	501	0
Change in fair value of warrant liability	1,182	3,083
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	1,369	566
Other non-cash items	53	16
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(4,953)	(3,836)
Other assets	(11)	0
Accounts payable	(694)	3,271
Accrued expenses	3,643	3,697
Other long-term liabilities	(44)	6
Net cash used in operating activities	(114,989)	(32,702)
Cash flows from investing activities:
Purchases of property and equipment	(1,501)	(49)
Purchase of equity method investment	(1,375)	(2,999)
Net cash used in investing activities	(2,876)	(3,048)
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)
Payments of issuance costs	(2,987)	(3,053)
Proceeds from exercise of stock options	1,836	0
Net cash provided by financing activities	203,849	216,348
Net increase in cash	85,984	180,598
Cash at beginning of period	131,468	23,692
Cash at end of period	217,452	204,290
Supplemental disclosure of cash flow information:
Cash paid for interest	0	98
Cash paid for income taxes	23	450
Supplemental disclosure of non-cash investing and financing activities:
Offering costs included in accounts payable and accrued expenses	377	2,015
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