CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (22,636)	$ (12,310)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation and amortization expense	698	813
Stock compensation expense	6,810	3,807
Change in fair value of warrants	0	2,944
Loss on sale of fixed assets	0	23
Foreign currency translation loss	13	49
Amortization of premiums and discounts on marketable securities	(408)	0
Non-cash lease cost	1,139	0
Change in operating assets and liabilities:
Inventory	(1,230)	68
Accounts receivable	2,370	771
Prepaid and other current assets	680	254
Accounts payable	(2,238)	(1,049)
Accrued expenses	(2,229)	(462)
Operating lease liabilities	(1,007)	0
Other assets and liabilities, net	(187)	56
Net cash used in operating activities	(18,225)	(5,036)
Investing activities:
Purchases of short-term investments	(32,402)	0
Maturities of short-term investments	45,477	0
Expenditures for property, plant and equipment	(1,224)	(979)
Net cash provided by (used in) investing activities	11,851	(979)
Financing activities:
Net proceeds from equity offering	0	70,090
Net proceeds from common stock issuance due to stock option exercises	2,059	2,096
Proceeds from exercise of warrants	0	1,965
Other	(9)	(29)
Net cash provided by financing activities	2,050	74,122
Net increase (decrease) in cash and cash equivalents	(4,324)	68,107
Cash and cash equivalents at beginning of period	18,286	26,862
Cash and cash equivalents at end of period	$ 13,962	$ 94,969