Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 83,004	$ 80,042
Short-term investments	54,579	31,238
Prepaid expenses and other current assets	1,341	1,086
Total current assets	138,924	112,366
Property and equipment, net	1,045	812
Other assets	170	143
Total assets	140,139	113,321
Current liabilities:
Accounts payable	1,777	1,633
Accrued expenses and other current liabilities	3,716	2,508
Accrued interest	451
Total current liabilities	5,944	4,141
Other long-term liabilities	321	367
Total liabilities	55,085	4,508
Commitments and Contingencies (Note 7)
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 September 30, 2016 and December 31, 2015; 26,930,730 shares and 26,423,394 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	269	264
Additional paid-in capital	310,686	304,583
Accumulated deficit	(225,903)	(196,023)
Accumulated other comprehensive income (loss)	2	(11)
Total stockholders’ equity	85,054	108,813
Total liabilities and stockholders’ equity	140,139	$ 113,321
2021 Convertible Notes [Member]
Current liabilities:
2021 Convertible Notes, net of issuance costs	$ 48,820