Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 197,179,000	$ 30,915,000
Marketable securities	162,680,000	174,688,000
Prepaid expenses and other current assets	2,334,000	3,790,000
Total current assets	362,193,000	209,393,000
Property and equipment, net	11,863,000	11,664,000
Long-term investments		4,725,000
Restricted cash	600,000	480,000
Total assets	374,656,000	226,262,000
Current liabilities:
Accounts payable	2,741,000	2,161,000
Accrued expenses and other current liabilities	7,097,000	6,245,000
Current portion of long-term debt	9,967,000	9,134,000
Total current liabilities	19,805,000	17,540,000
Long-term debt, net	17,584,000	21,399,000
2024 convertible notes, net	133,484,000
Other long-term liabilities	404,000	291,000
Total liabilities	171,277,000	39,230,000
Commitments and contingencies
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2017 and December 31, 2016 and 0 shares issued and outstanding at June 30, 2017 and December 31, 2016
Stockholders’ equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 31,904,926 and 31,667,469 shares issued and outstanding, at June 30, 2017 and December 31, 2016, respectively	32,000	32,000
Additional paid-in capital	467,874,000	398,757,000
Accumulated other comprehensive income	(77,000)	(71,000)
Accumulated deficit	(264,450,000)	(211,686,000)
Total stockholders’ equity	203,379,000	187,032,000
Total liabilities and stockholders’ equity	$ 374,656,000	$ 226,262,000