Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 3,568	$ 1,412
Marketable securities	674	695
Accounts receivable	35	24
Assets held for sale		764
Prepaid expenses and other current assets	1,008	610
Total current assets	5,285	3,505
Property and equipment, net	8,142	8,586
Patent and trademark rights, net	886	858
Other assets	1,372	1,258
Total assets	15,685	14,207
Current liabilities:
Accounts payable	689	741
Accrued expenses	1,193	1,966
Current portion of financing obligation	195
Total current liabilities	2,077	2,707
Long-term liabilities:
Note Payable		1,835
Financing obligation arising from sale leaseback transaction (Note 13)	2,417
Redeemable warrants	2,095	962
Commitments and contingencies
Stockholders' equity:
Preferred stock, par value $0.01 per share, authorized 5,000,000; issued and outstanding; none
Common stock, par value $0.001 per share, authorized 350,000,000 shares; issued and outstanding 46,817,965 and 32,884,786, respectively	47	33
Additional paid-in capital	322,946	317,419
Accumulated other comprehensive (loss) income	(9)	11
Accumulated deficit	(313,888)	(308,760)
Total stockholders' equity	9,096	8,703
Total liabilities and stockholders' equity	$ 15,685	$ 14,207