Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 106,084	$ 200,404
Short-term investments	264,984	300,255
Restricted cash - short-term	194	194
Accounts receivable	986	1,250
Prepaid expenses and other current assets	12,373	21,170
Total current assets	384,621	523,273
Property and equipment, net	53,780	50,517
Operating lease assets	26,159	12,303
Restricted cash - long-term	1,200	1,200
Other assets	2,367	827
Total assets	468,127	588,120
Current liabilities:
Accounts payable	17,368	7,118
Accrued compensation	25,150	20,458
Accrued research and development expenses	13,451	15,813
Deferred revenue	40,760	33,455
Other current liabilities	9,057	6,057
Total current liabilities	105,786	82,901
Deferred revenue - long-term	55,708	27,795
Operating lease liabilities - long-term	25,518	13,041
Other long-term liabilities	1,501	2,044
Total liabilities	188,513	125,781
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock—$0.0001 par value, 500,000 shares authorized as of December 31, 2021 and 2020, respectively; 91,671 and 83,372 shares issued and outstanding as of December 31, 2021 and 2020, respectively	9	8
Additional paid-in capital	1,744,695	1,586,616
Accumulated other comprehensive (loss) income	(368)	296
Accumulated deficit	(1,464,722)	(1,124,581)
Total stockholders’ equity	279,614	462,339
Total liabilities and stockholders’ equity	$ 468,127	$ 588,120