Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 201,153	$ 182,069
Prepaid expenses and other current assets	4,152	2,542
Total current assets	205,305	184,611
Other assets		327
Property and equipment, net	265	389
Total assets	205,570	185,327
Current liabilities
Accounts payable	1,357	1,671
Accrued liabilities	12,899	7,156
Income taxes payable	247
Upfront payment from collaboration partner (Note 6)	40,000
Total liabilities	54,503	8,827
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock, $0.0001 par value, 5,000,000 shares authorized at December 31, 2016 and December 31, 2015; zero shares issued and outstanding at December 31, 2016 and December 31, 2015
Common stock, $0.0001 par value, 50,000,000 shares authorized at December 31, 2016 and December 31, 2015; 34,843,885 and 29,420,247 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	3	3
Additional paid-in capital	440,667	369,933
Accumulated other comprehensive loss	(350)
Accumulated deficit	(289,253)	(193,436)
Total stockholders' equity	151,067	176,500
Total liabilities and stockholders’ equity	$ 205,570	$ 185,327