Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 142,025	$ 30,376
Short-term investments	484,175	108,935
Receivable from collaboration partner	150,000
Other prepaid expenses and current assets	5,607	2,483
Total current assets	781,807	141,794
Long-term investments	0	2,499
Property and equipment, net	912	248
Other assets	723	771
Total assets	783,442	145,312
Current liabilities:
Accounts payable	3,996	1,061
Accrued expenses and other current liabilities	22,537	14,083
Current portion of deferred revenue	195,037
Total current liabilities	221,570	15,144
Non-current portion of deferred revenue	183,662
Total liabilities	405,232	15,144
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; no shares issued and outstanding at December 31, 2017 and 2016, respectively
Common stock, $0.0001 par value; 125,000,000 shares authorized; 29,991,884 and 21,681,236 shares issued and outstanding at December 31, 2017 and 2016, respectively	3	2
Additional paid-in capital	666,891	269,423
Accumulated deficit	(288,112)	(139,236)
Accumulated other comprehensive loss	(572)	(21)
Total stockholders' equity	378,210	130,168
Total liabilities and stockholders' equity	$ 783,442	$ 145,312