Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 74,266	$ 91,060
Short-term investments	45,023	45,502
Prepaid expenses and other current assets	1,402	1,865
Total current assets	120,691	138,427
Long-term investments	11,480	13,808
Furniture, fixtures and equipment, net	3,993	3,816
Other assets, net	3,037	3,076
Total assets	139,201	159,127
Current liabilities
Accounts payable and other current liabilities	15,501	16,565
Interest payable	545	551
Total current liabilities	16,046	17,116
Convertible notes, net of discounts	123,310	123,236
Total liabilities	$ 139,356	$ 140,352
Commitments and contingencies
Stockholders’ (deficit) equity
Preferred stock, $0.001 par value; 15,000,000 shares authorized as of March 31, 2016 and December 31, 2015; None issued and outstanding	$ 0	$ 0
Common stock, $0.001 par value; 150,000,000 shares authorized as of March 31, 2016 and December 31, 2015; 26,518,449 and 26,458,495 shares issued and outstanding as of March 31, 2016 and December 31, 2015, respectively	27	26
Additional paid-in capital	240,154	236,492
Accumulated other comprehensive loss	(68)	(179)
Accumulated deficit	(240,268)	(217,564)
Total stockholders’ (deficit) equity	(155)	18,775
Total liabilities and stockholders’(deficit) equity	$ 139,201	$ 159,127