Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 101,436	$ 246,122
Short-term investments	314,691	68,564
Prepaid expenses and other current assets	7,709	4,760
Total current assets	423,836	319,446
Property and equipment, net	15,743	5,138
Operating lease right-of-use assets	417
Long-term investments	14,153	80,148
Restricted cash and other	1,945	2,521
Total assets	456,094	407,253
Current liabilities
Accounts payable	6,237	2,946
Accrued liabilities	41,292	20,758
Prepayment from collaboration partner		12,973
Operating lease liabilities - current	383
Total current liabilities	47,912	36,677
Other long-term liabilities	1,908	9
Total liabilities	49,820	36,686
Commitments and contingencies (Note 7)
Stockholders’ equity
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; none issued and outstanding	0	0
Common stock, $0.0001 par value, 150,000,000 shares authorized at December 31, 2019 and 2018; 46,379,073 and 40,288,949 shares issued and outstanding at December 31, 2019 and 2018, respectively	5	4
Additional paid-in capital	884,486	573,183
Accumulated other comprehensive income (loss)	549	(67)
Accumulated deficit	(478,766)	(202,553)
Total stockholders’ equity	406,274	370,567
Total liabilities and stockholders’ equity	$ 456,094	$ 407,253