Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 78,720	$ 29,798
Short-term investments	21,294	96,675
Prepaid expenses and other current assets	1,033	1,876
Total current assets	101,047	128,349
Property and equipment, net	563	1,130
Other assets	168	168
Total assets	101,778	129,647
Current liabilities:
Accounts payable	451	1,592
Accrued expenses and other current liabilities	2,373	4,246
Accrued interest	1,246	1,204
Total current liabilities	4,070	7,042
Other long-term liabilities	403	477
Total liabilities	54,014	56,479
Commitments and Contingencies (Note 9)
Stockholders’ equity:
Preferred Stock, $0.001 par value: 5,000,000 shares authorized and no shares issued or outstanding
Common stock, $0.01 par value: 120,000,000 shares authorized at December 31, 2017 and December 31, 2016; 6,805,686 shares and 6,746,579 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	68	67
Additional paid-in capital	316,086	312,032
Accumulated deficit	(268,374)	(238,877)
Accumulated other comprehensive loss	(16)	(54)
Total stockholders’ equity	47,764	73,168
Total liabilities and stockholders’ equity	101,778	129,647
2021 Convertible Notes [Member]
Current liabilities:
2021 Convertible Notes, net of issuance costs	$ 49,541	$ 48,960