Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 29,798	$ 80,042
Short-term investments	96,675	31,238
Prepaid expenses and other current assets	1,876	1,086
Total current assets	128,349	112,366
Property and equipment, net	1,130	812
Other assets	168	143
Total assets	129,647	113,321
Current liabilities:
Accounts payable	1,592	1,633
Accrued expenses and other current liabilities	4,416	2,508
Accrued interest	1,204
Total current liabilities	7,212	4,141
Other long-term liabilities	307	367
Total liabilities	56,479	4,508
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, 2016 and December 31, 2015; 26,986,318 shares and 26,423,394 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	270	264
Additional paid-in capital	311,829	304,583
Accumulated deficit	(238,877)	(196,023)
Accumulated other comprehensive loss	(54)	(11)
Total stockholders’ equity	73,168	108,813
Total liabilities and stockholders’ equity	129,647	$ 113,321
2021 Convertible Notes [Member]
Current liabilities:
2021 Convertible Notes, net of issuance costs	$ 48,960