Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (24,185)		$ (17,120)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts	32
Depreciation and amortization	334		188
Stock-based compensation	1,529		827
Fair value of common stock issued	256		260
Non-cash interest expense	776		489
Loss from minority interest in limited liability company	407
Changes in assets and liabilities:
Accounts receivable	(1,060)		(1,709)
Inventory	(1,930)		352
Prepaid expenses and other current assets	(283)		(822)
Other noncurrent assets	14		4
Accounts payable	68		258
Accrued and other liabilities	635		(5)
Other noncurrent liabilities	173		(53)
Net cash used in operating activities	(23,234)		(17,331)
Cash flows from investing activities:
Purchase of property and equipment	(803)		(400)
Net cash used in investing activities	(803)		(400)
Cash flows from financing activities:
Proceeds from sale of common stock, net of issuance costs	33,396		31,440
Proceeds from note payable			19,214
Repayments of note payable			(10,000)
Proceeds from issuance of common shares from employee stock purchase plan	124
Proceeds from exercise of stock options			31
Proceeds from exercise of warrant			20
Net cash provided by financing activities	33,520		40,705
Net increase in cash and cash equivalents	9,483		22,974
Cash and cash equivalents - beginning of period	20,730	[1]	8,086
Cash and cash equivalents - end of period	30,213		31,060
Supplemental disclosure:
Cash paid for interest	1,315		1,183
Cash paid for income taxes	2
Supplemental disclosure of cash flow information as of end of period:
Issuance of warrants in connection with note payable			940
Issuance of note payable in settlement of accrued interest	616
Net transfer of equipment between inventory and property and equipment	$ 159		$ 292

[1] The condensed consolidated balance sheet as of December 31, 2017 has been derived from the audited consolidated financial statements as of that date.