Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 521,396	$ 436,575
Short-term investments	211,636	300,286
Restricted cash and cash equivalents, current	8,601	7,993
Receivable from collaboration	112,500
Contract asset	112,500
Prepaid expenses and other current assets	26,481	27,511
Total current assets	993,114	772,365
Intangible assets, net	33,687	33,820
Goodwill	16,937	16,937
Property and equipment, net	17,291	17,946
Operating right-of-use assets	60,461	61,947
Restricted cash and cash equivalents, noncurrent	6,998	6,919
Other assets	7,096	8,827
TOTAL ASSETS	1,135,584	918,761
CURRENT LIABILITIES:
Accounts payable	3,701	5,077
Accrued and other liabilities	70,069	76,936
Deferred revenue, current portion	262,929	6,451
Contingent consideration, current portion	24,400	10,600
Total current liabilities	361,099	99,064
Deferred revenue, noncurrent	3,815	3,815
Operating lease liabilities, noncurrent	66,615	66,556
Contingent consideration, noncurrent	46,036	25,374
Deferred tax liability	3,253	3,253
Other long-term liabilities	3,815	3,847
TOTAL LIABILITIES	484,633	201,909
Commitments and contingencies (Note 8)
STOCKHOLDERS’ EQUITY:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of March 31, 2021 and December 31, 2020; no shares issued and outstanding as of March 31, 2021 and December 31, 2020
Common stock, $0.0001 par value; 300,000,000 shares authorized as of March 31, 2021 and December 31, 2020; 129,891,856 and 127,416,740 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	13	13
Additional paid-in capital	1,488,337	1,385,301
Accumulated other comprehensive loss	(1,304)	(1,278)
Accumulated deficit	(836,095)	(667,184)
TOTAL STOCKHOLDERS’ EQUITY	650,951	716,852
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 1,135,584	$ 918,761