Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 58,903	$ 62,944
Marketable securities	39,456	48,303
Accounts receivable	56	95
Prepaid expenses and other current assets	1,217	761
Total current assets	99,632	112,103
Property and equipment, net	9,083	7,442
Long-term investments	3,006	7,357
Other assets	270	157
Restricted cash	80	80
Total assets	112,071	127,139
Current liabilities:
Accounts payable	3,083	3,692
Accrued expenses and other current liabilities	4,792	4,367
Current portion of long-term debt	384
Total current liabilities	8,259	8,059
Long-term debt	14,688	15,002
Other long-term liabilities	222	91
Total liabilities	$ 23,169	$ 23,152
Commitments and contingencies
Preferred Stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2016 and December 31, 2015 and 0 shares issued and outstanding at March 31, 2016 and December 31, 2015
Stockholders' equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 21,570,395 and 21,570,395 shares issued and outstanding, at March 31, 2016 and December 31, 2015, respectively	$ 22	$ 22
Additional paid-in capital	245,495	243,854
Accumulated other comprehensive income	(8)	(97)
Accumulated deficit	(156,607)	(139,792)
Total stockholders' equity	88,902	103,987
Total liabilities and stockholders' equity	$ 112,071	$ 127,139