Consolidated Balance Sheets - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 294,233,000	$ 1,661,082,000
Marketable securities	1,448,063,000	438,467,000
Prepaid expenses and other current assets	39,841,000	22,821,000
Collaboration receivable - related party	18,506,000
Total current assets	1,800,643,000	2,122,370,000
Property and equipment, net	3,016,000	6,755,000
Restricted cash	1,269,000	1,716,000
Right-of-use operating asset	16,109,000	25,064,000
Other long-term assets	4,251,000	3,341,000
Total assets	1,825,288,000	2,159,246,000
Current liabilities:
Accounts payable	10,450,000	3,691,000
Accrued expenses	67,275,000	54,851,000
Operating lease liability, current portion	7,468,000	8,662,000
Total current liabilities	85,193,000	67,204,000
Operating lease liability, net of current portion	10,964,000	19,438,000
Other liabilities	100,000	270,000
Total liabilities	96,257,000	86,912,000
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at December 31, 2021 and December 31, 2020; no shares issued or outstanding at December 31, 2021 and December 31, 2020
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at December 31, 2021 and December 31, 2020; 58,940,083 and 58,311,444 shares issued at December 31, 2021 and December 31, 2020; 58,937,050 and 58,308,411 shares outstanding at December 31, 2021 and December 31, 2020	6,000	6,000
Treasury stock, at cost, 3,033 shares at December 31, 2021 and December 31, 2020	(400,000)	(400,000)
Additional paid-in capital	3,227,471,000	3,109,807,000
Accumulated deficit	(1,495,386,000)	(1,037,494,000)
Accumulated other comprehensive gain (loss)	(2,660,000)	415,000
Total stockholders’ equity	1,729,031,000	2,072,334,000
Total liabilities and stockholders’ equity	$ 1,825,288,000	$ 2,159,246,000