Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 514,158	$ 1,661,082
Marketable securities	1,397,157	438,467
Prepaid expenses and other current assets	28,846	22,821
Collaboration receivable - related party	48,438
Total current assets	1,988,599	2,122,370
Property and equipment, net	3,280	6,755
Restricted cash	1,269	1,716
Right-of-use operating asset	18,728	25,064
Other long-term assets	3,599	3,341
Total assets	2,015,475	2,159,246
Current liabilities:
Accounts payable	2,917	3,691
Accrued expenses	61,623	54,851
Operating lease liability, current portion	7,358	8,662
Total current liabilities	71,898	67,204
Operating lease liability, net of current portion	13,964	19,438
Other liabilities	101	270
Total liabilities	85,963	86,912
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at June 30, 2021 and December 31, 2020; no shares issued or outstanding at June 30, 2021 and December 31, 2020
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at June 30, 2021 and December 31, 2020; 58,773,397 and 58,311,444 shares issued at June 30, 2021 and December 31, 2020; 58,770,364 and 58,308,411 shares outstanding at June 30, 2021 and December 31, 2020	6	6
Treasury stock, at cost, 3,033 shares at June 30, 2021 and December 31, 2020	(400)	(400)
Additional paid-in capital	3,170,694	3,109,807
Accumulated deficit	(1,240,503)	(1,037,494)
Accumulated other comprehensive gain (loss)	(285)	415
Total stockholders’ equity	1,929,512	2,072,334
Total liabilities and stockholders’ equity	$ 2,015,475	$ 2,159,246