Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 119,010	$ 62,944
Marketable securities	44,251	48,303
Accounts receivable	101	95
Prepaid expenses and other current assets	1,180	761
Total current assets	164,542	112,103
Property and equipment, net	11,286	7,442
Long-term investments		7,357
Other assets	90	157
Restricted cash	80	80
Total assets	175,998	127,139
Current liabilities:
Accounts payable	3,513	3,692
Accrued expenses and other current liabilities	3,052	4,367
Current portion of long-term debt	1,634
Total current liabilities	8,199	8,059
Long-term debt	13,520	15,002
Other long-term liabilities	253	91
Total liabilities	21,972	23,152
Commitments and contingencies
Preferred Stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2016 and December 31, 2015 and 0 shares issued and outstanding at June 30, 2016 and December 31, 2015
Stockholders’ equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 27,521,070 and 21,570,395 shares issued and outstanding, at June 30, 2016 and December 31, 2015, respectively	28	22
Additional paid-in capital	324,780	243,854
Accumulated other comprehensive income	10	(97)
Accumulated deficit	(170,792)	(139,792)
Total stockholders’ equity	154,026	103,987
Total liabilities and stockholders’ equity	$ 175,998	$ 127,139