Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 227,184	$ 135,797
Short-term investments	19,993	4,072
Receivable from collaboration partner		45,000
Prepaid expenses and other current assets	1,545	1,394
Total current assets	248,722	186,263
Property and equipment, net	2,633	2,758
Long-term investments	36,003	12,002
Other long-term assets	432	283
Total assets	287,790	201,306
Current liabilities
Accounts payable	2,030	1,798
Accrued liabilities	10,634	8,690
Deferred revenue - current	22,500	22,500
Total current liabilities	35,164	32,988
Other long-term liabilities	246	436
Deferred revenue - noncurrent	5,625	22,500
Total liabilities	41,035	55,924
Commitments and contingencies (Note 6)
Stockholders’ equity
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; none issued and outstanding
Common stock, $0.0001 par value, 150,000,000 and 150,000,000 shares authorized at September 30, 2017 and December 31, 2016, respectively; 35,733,002 and 31,428,998 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	4	3
Additional paid-in capital	363,205	223,208
Accumulated other comprehensive (loss) income	(52)	8
Accumulated deficit	(116,402)	(77,837)
Total stockholders’ equity	246,755	145,382
Total liabilities and stockholders’ equity	$ 287,790	$ 201,306