Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 135,797	$ 112,265
Short-term investments	4,072
Receivable from collaboration partner	45,000
Prepaid expenses and other current assets	1,394	1,282
Total current assets	186,263	113,547
Property and equipment, net	2,758	2,744
Long-term investments	12,002
Other long term assets	283	289
Total assets	201,306	116,580
Current liabilities
Accounts payable	1,798	2,143
Accrued liabilities	8,690	5,633
Deferred revenue - current	22,500	14,199
Total current liabilities	32,988	21,975
Other long-term liabilities	436	732
Deferred revenue—noncurrent	22,500
Total liabilities	55,924	22,707
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 December 31, 2016 and 2015, respectively; 31,428,998 and 27,053,156 shares, issued and outstanding at December 31, 2016 and 2015, respectively	3	3
Additional paid-in capital	223,208	158,555
Accumulated other comprehensive income	8
Accumulated deficit	(77,837)	(64,685)
Total stockholders’ equity	145,382	93,873
Total liabilities and stockholders’ equity	$ 201,306	$ 116,580