CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 49,940	$ 76,793
Grant and incentive receivables	2,178	1,608
Restricted cash	51
Prepaid expenses and other current assets	4,393	1,129
Total current assets	56,562	79,530
Property and equipment, net	353	421
Restricted cash	295	355
Other assets		948
Total assets	57,210	81,254
Current liabilities:
Accounts payable	2,137	1,893
Accrued expenses	3,879	5,779
Unearned income	712	694
Loans payable, net of discount	3,486	2,314
Total current liabilities	10,214	10,680
Loan payable, net of discount and current portion	7,706	9,922
Unearned income	1,519	1,936
Other long-term liabilities	7	9
Total liabilities	19,446	22,547
Commitments and contingencies (Note 10)
Stockholders’ equity:
Common stock, $0.001 par value; 200,000,000 shares authorized as of June 30, 2018 and December 31, 2017; 14,315,410 and 14,294,383 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	14	15
Additional paid-in capital	152,601	150,830
Accumulated other comprehensive income (loss)	177	127
Accumulated deficit	(115,028)	(92,265)
Total stockholders’ equity	37,764	58,707
Total liabilities and stockholders’ equity	$ 57,210	$ 81,254