CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (4,405)	$ (6,865)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	196	291
Stock-based compensation	185	605
Amortization of intangible assets	28	28
Amortization of debt issuance costs	11
Accrued interest	210	33
Changes in assets and liabilities:
Accounts receivable	(151)	(69)
Inventories	396	129
Prepaid expenses and other assets	173	(238)
Accounts payable	(219)	(721)
Accrued expenses and other liabilities	(602)	(411)
Net cash used in operating activities	(4,178)	(7,218)
Cash flows from investing activities:
Purchases of property and equipment		(200)
Proceeds from sales and maturities of marketable securities	2,364	12,429
Purchases of marketable securities	(1,602)	(8,197)
Net cash provided by investing activities	762	4,032
Cash flows from financing activities:
Net proceeds from issuance of common stock	(20)	197
Proceeds from the issuance of notes payable, net of issuance costs		7,879
Payments on capital lease obligations		(27)
Net cash provided by (used in) financing activities	(20)	8,049
Net increase (decrease) in cash and cash equivalents	(3,436)	4,863
Cash and cash equivalents at beginning of period	8,766	5,640
Cash and cash equivalents at end of period	5,330	$ 10,503
Supplemental disclosure:
Issuance of convertible notes in settlement of accrued interest	$ 420