Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 51,463	$ 20,605
Short-term investments, available-for-sale	180,558	199,729
Accounts receivable	1,599	2,432
Prepaid expenses and other current assets	2,845	6,071
Total current assets	236,465	228,837
Long-term investments	47,407	124,040
Property and equipment, net of accumulated depreciation	2,843	3,045
Other long-term assets	55	70
Total assets	286,770	355,992
Current liabilities:
Accounts payable	3,890	10,458
Accrued liabilities	6,215	9,721
Total current liabilities	10,105	20,179
Lease-related obligations	441	354
Total liabilities	10,546	20,533
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized at December 31, 2016 and 2015; no shares issued and outstanding as of December 31, 2016 and 2015	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized at December 31, 2016 and 2015; 46,522,475 and 46,162,525 shares issued and outstanding at December 31, 2016 and 2015, respectively	46	46
Additional paid-in capital	692,422	675,591
Accumulated other comprehensive loss	(440)	(764)
Accumulated deficit	(415,804)	(339,414)
Total stockholders’ equity	276,224	335,459
Total liabilities and stockholders’ equity	$ 286,770	$ 355,992