Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (199,469)	$ (114,803)	$ (78,185)
Adjustments to reconcile net loss to net cash used for operating activities:
Share-based compensation expense	35,151	21,795	14,546
Depreciation expense	4,405	1,268	730
Loss on disposal of equipment	236	199	75
Non-cash interest expense	6,797	0	0
Changes in operating assets and liabilities:
Accounts receivable, net	(1,381)	0	0
Inventory	(2,020)	0	0
Prepaid expenses and other current assets	(1,964)	(1,642)	(664)
Other assets	0	219	(149)
Accounts payable	(2,912)	4,832	3,600
Accrued expenses	5,451	(202)	227
Accrued payroll and related expenses	2,514	2,918	987
Deferred rent	824	335	124
Net cash used for operating activities	(152,368)	(85,081)	(58,709)
Investing activities
Purchase of property and equipment	(2,340)	(9,194)	(2,218)
Net cash used for investing activities	(2,340)	(9,194)	(2,218)
Financing activities
Net proceeds from royalty financing	124,289	0	0
Net proceeds from the issuance of common stock	109,809	117,480	0
Net proceeds from the exercise of stock options for common stock	1,908	2,693	149
Proceeds from issuance of common stock under ESPP	391	0	0
Net cash provided by financing activities	236,397	120,173	149
Net increase (decrease) in cash, cash equivalents and restricted cash	81,689	25,898	(60,778)
Cash, cash equivalents and restricted cash at beginning of period	91,824	65,926	126,704
Cash, cash equivalents and restricted cash at end of period	173,513	91,824	65,926
Supplemental disclosure of cash flow information
Interest paid	506	0	0
Capitalized landlord funded tenant improvements	0	13,696	0
Reconciliation of cash, cash equivalents and restricted cash to the consolidated balance sheets
Total cash, cash equivalents and restricted cash	$ 91,824	$ 65,926	$ 126,704