Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 776	$ 2,408
Marketable securities	2,973	3,460
Accounts receivable	41
Assets held for sale	764	764
Prepaid expenses and other current assets	636	309
Total current assets	5,190	6,941
Property and equipment, net	9,257	9,514
Patent and trademark rights, net	870	872
Other assets	1,546	1,546
Total assets	16,863	18,873
Current liabilities:
Accounts payable	927	887
Accrued expenses	1,709	1,548
Total current liabilities	2,636	2,435
Redeemable warrants	1,279	940
Commitments and contingencies (Note 6)
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 26,186,998 and 24,202,921, respectively	26	24
Additional paid-in capital	316,238	315,980
Accumulated other comprehensive income (loss)	6	(5)
Accumulated deficit	(303,322)	(300,501)
Total stockholders' equity	12,948	15,498
Total liabilities and stockholders' equity	$ 16,863	$ 18,873