Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 17,417	$ 17,515
Prepaid expenses and other current assets	485	513
Total current assets	17,902	18,028
Property and equipment, net of accumulated depreciation of $1,919 and $1,561, respectively	1,470	1,489
Other assets	39	65
Total assets	19,411	19,582
Current liabilities:
Accounts payable	862	440
Related party payable	2,303	942
Accrued expenses	1,260	1,551
Warrant liability, current	0	54
Total current liabilities	4,425	2,987
Convertible promissory notes, net of debt discount of $18,003 and $18,088, respectively (see Note 7)	0	0
Accrued interest payable	967	228
Warrant liability, long term	1,073	5,980
Derivative liability	3,136	1,735
Deferred rent	803	791
Total liabilities	10,404	11,721
Commitments and contingencies (Note 16)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 8,000 shares issued and outstanding as of December 31, 2017; 5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2016; aggregate liquidation preference of $8,264 at December 31, 2017	0	0
Common stock, $0.001 par value; 150,000,000 shares authorized, 25,940,247 shares issued and outstanding as of December 31, 2017; 150,000,000 shares authorized, 14,688,135 shares issued and outstanding as of December 31, 2016	26	15
Additional paid-in capital	187,784	170,409
Accumulated deficit	(178,803)	(162,563)
Total stockholders’ equity	9,007	7,861
Total liabilities and stockholders’ equity	$ 19,411	$ 19,582