Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 324,164	$ 327,214
Marketable securities	906,091	779,246
Prepaid expenses	35,422	32,888
Receivables and other current assets	27,517	12,826
Total current assets	1,293,194	1,152,174
Marketable securities	207,615	131,506
Property, plant and equipment, net	157,681	151,176
Intangible assets, net	11,112	14,326
Goodwill	13,128	13,128
Operating lease right-of-use assets	188,450	185,885
Restricted cash and other non-current assets	74,304	79,229
Total assets	1,945,484	1,727,424
Current liabilities:
Accounts payable	25,309	42,995
Accrued expenses and other current liabilities	138,274	141,556
Operating lease liability, current portion	22,218	20,175
Deferred revenue, current portion	1,061	8,474
Collaboration research advancement, current portion	10,045	10,380
Total current liabilities	196,907	223,580
Deferred revenue, net of current portion	25,762	9,791
Collaboration research advancement, net of current portion	21,968	27,834
Operating lease liability, net of current portion	173,075	170,812
Other non-current liabilities	4,751	10,414
Total liabilities	422,463	442,431
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at September 30, 2020 and December 31, 2019	0	0
Common stock, $0.01 par value, 125,000 shares authorized; 66,339 and 55,368 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	663	554
Additional paid-in capital	4,227,254	3,568,184
Accumulated other comprehensive loss	(4,223)	(1,893)
Accumulated deficit	(2,700,673)	(2,281,852)
Total stockholders’ equity	1,523,021	1,284,993
Total liabilities and stockholders’ equity	$ 1,945,484	$ 1,727,424