Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (31,054)	$ (25,777)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	176	186
Stock-based compensation expense	3,317	2,903
Amortization of debt issuance costs	255	232
Amortization of premium/discount on investments	(62)	76
Change in fair value of foreign currency derivative	(406)	1,804
Changes in operating assets and liabilities:
Receivables	(709)	423
Inventory	1,049	(7)
Prepaid expenses and other assets	321	(1,015)
Accounts payable and accrued expenses	(1,429)	152
Interest payable	1,544	1,370
Net cash used in operating activities	(26,998)	(19,653)
Investing activities
Acquisitions of property and equipment	(93)	(35)
Purchases of investments	(3,018)	(4,327)
Sales and maturities of investments	18,992	20,289
Net cash provided by investing activities	15,881	15,927
Financing activities
Payment of senior credit facility		(1,725)
Proceeds from senior credit facility	19,477
Net proceeds from common stock issued under stock-based compensation plans	563	268
Decrease in lease financing obligation		(19)
Net cash provided by (used in) financing activities	20,040	(1,476)
Increase (decrease) in cash, cash equivalents and restricted cash	8,923	(5,202)
Cash, cash equivalents and restricted cash at beginning of period	28,275	53,568
Cash, cash equivalents and restricted cash at end of period	$ 37,198	$ 48,366