Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating Activities
Net loss	$ (13,994)	$ (16,091)
Adjustments to reconcile net loss to net cash used in operating activities:
(Loss)/Gain from change in fair value of derivative warrant liability	3,040	(5,519)
(Loss)/Gain from change in fair value of 2020 Notes embedded derivative	(2,347)	1,662
Loss from the change in fair value of the 2017 Notes		339
Loss on exchange of debt	2,202	4,933
Stock-based compensation	237	225
Depreciation and amortization	3,285	3,341
Non-cash interest expense	884	196
Other non-cash expense	6
Changes in operating assets and liabilities:
Accounts receivable	(389)	(242)
Inventories	516	(838)
Prepaid expenses and other current assets	(416)	(114)
Accounts payable, accrued expenses, and long-term liabilities	(829)	(1,276)
Net cash used in operating activities	(7,805)	(13,384)
Investing Activities
Acquisitions of property, plant and equipment	(97)	(1,315)
Net cash used in investing activities	(97)	(1,315)
Financing Activities
Payments on secured debt		(9,616)
Debt and equity offering costs	(299)	(931)
Proceeds from issuance of common stock	22,415	11,044
Proceeds from the exercise of common stock warrants	1,263	6
Net cash provided by financing activities	23,379	503
Net (decrease) in cash and cash equivalents	15,477	(14,196)
Beginning of period	11,553	30,499
End of period	27,030	16,303
Cash paid for interest, net of interest capitalized	850	2,116
Non-cash purchase of property, plant and equipment	16	189
Exchange or conversion of convertible debt into common stock	3,701	8,653
Accrued debt and equity issuance costs	61	126
Discount due to exchange of 2017 Notes for 2020 Notes		3,009
Fair value of 2020 Notes embedded derivative upon exchange		6,975
Fair value of 2020 Notes embedded derivative liability upon conversion into common stock	2,193
Fair value of warrants at issuance and upon exercise, net	4,905	5,213
Shares of common stock sold but not paid at June 30, 2018	$ 14,130