Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 42,921,000	$ 30,915,000
Marketable securities	142,896,000	174,688,000
Prepaid expenses and other current assets	4,307,000	3,790,000
Total current assets	190,124,000	209,393,000
Property and equipment, net	11,841,000	11,664,000
Long-term investments	1,728,000	4,725,000
Restricted cash	600,000	480,000
Total assets	204,293,000	226,262,000
Current liabilities:
Accounts payable	2,210,000	2,161,000
Accrued expenses and other current liabilities	5,815,000	6,245,000
Current portion of long-term debt	9,967,000	9,134,000
Total current liabilities	17,992,000	17,540,000
Long-term debt	19,908,000	21,399,000
Other long-term liabilities	294,000	291,000
Total liabilities	38,194,000	39,230,000
Commitments and contingencies
Preferred Stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2017 and December 31, 2016 and 0 shares issued and outstanding at March 31, 2017 and December 31, 2016
Stockholders’ equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 31,752,692 and 31,667,469 shares issued and outstanding, at March 31, 2017 and December 31, 2016, respectively	32,000	32,000
Additional paid-in capital	401,694,000	398,757,000
Accumulated other comprehensive income	(62,000)	(71,000)
Accumulated deficit	(235,565,000)	(211,686,000)
Total stockholders’ equity	166,099,000	187,032,000
Total liabilities and stockholders’ equity	$ 204,293,000	$ 226,262,000