Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 439,714	$ 317,705
Marketable securities	572,722	833,546
Prepaid expenses	42,258	37,472
Receivables and other current assets	24,762	16,116
Inventory	18,079	10,698
Total current assets	1,097,535	1,215,537
Marketable securities	81,115	122,891
Property, plant and equipment, net	165,198	162,831
Intangible assets, net	11,469	10,041
Goodwill	13,128	13,128
Operating lease right-of-use assets	197,970	184,019
Restricted cash and other non-current assets	70,864	72,805
Total assets	1,637,279	1,781,252
Current liabilities:
Accounts payable	20,232	21,602
Accrued expenses and other current liabilities	146,791	145,406
Operating lease liability, current portion	28,063	25,024
Deferred revenue, current portion	1,330	2,320
Collaboration research advancement, current portion	9,899	9,236
Total current liabilities	206,315	203,588
Deferred revenue, net of current portion	25,762	25,762
Collaboration research advancement, net of current portion	19,399	21,581
Operating lease liability, net of current portion	177,702	167,997
Other non-current liabilities	7,768	7,268
Total liabilities	436,946	426,196
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at March 31, 2021 and December 31, 2020	0	0
Common stock, $0.01 par value, 125,000 shares authorized; 67,422 and 66,432 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	675	665
Additional paid-in capital	4,311,462	4,260,443
Accumulated other comprehensive loss	(5,449)	(5,505)
Accumulated deficit	(3,106,355)	(2,900,547)
Total stockholders’ equity	1,200,333	1,355,056
Total liabilities and stockholders’ equity	$ 1,637,279	$ 1,781,252