Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 58,519	$ 91,060
Short-term investments	48,512	45,502
Prepaid expenses and other current assets	1,171	1,865
Total current assets	108,202	138,427
Long-term investments	5,105	13,808
Furniture, fixtures and equipment, net	3,844	3,816
Other assets, net	2,979	3,076
Total assets	120,130	159,127
Current liabilities
Accounts payable and other current liabilities	13,598	16,565
Interest payable	545	551
Total current liabilities	14,143	17,116
Convertible notes, net of discounts	123,387	123,236
Total liabilities	137,530	140,352
Commitments and contingencies
Stockholders’ (deficit) equity
Preferred stock, $0.001 par value; 15,000,000 shares authorized as of June 30, 2016 and December 31, 2015; None issued and outstanding	0	0
Common stock, $0.001 par value; 150,000,000 shares authorized as of June 30, 2016 and December 31, 2015; 26,649,605 and 26,458,495 shares issued and outstanding as of June 30, 2016 and December 31, 2015, respectively	27	26
Additional paid-in capital	246,070	236,492
Accumulated other comprehensive loss	(10)	(179)
Accumulated deficit	(263,487)	(217,564)
Total stockholders’ (deficit) equity	(17,400)	18,775
Total liabilities and stockholders’(deficit) equity	$ 120,130	$ 159,127