Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 317,705	$ 327,214
Marketable securities	833,546	779,246
Prepaid expenses	37,472	32,888
Receivables and other current assets	26,814	12,826
Total current assets	1,215,537	1,152,174
Marketable securities	122,891	131,506
Property, plant and equipment, net	162,831	151,176
Intangible assets, net	10,041	14,326
Goodwill	13,128	13,128
Operating lease right-of-use assets	184,019	185,885
Restricted cash and other non-current assets	72,805	79,229
Total assets	1,781,252	1,727,424
Current liabilities:
Accounts payable	21,602	42,995
Accrued expenses and other current liabilities	145,406	141,556
Operating lease liability, current portion	25,024	20,175
Deferred revenue, current portion	2,320	8,474
Collaboration research advancement, current portion	9,236	10,380
Total current liabilities	203,588	223,580
Deferred revenue, net of current portion	25,762	9,791
Collaboration research advancement, net of current portion	21,581	27,834
Operating lease liability, net of current portion	167,997	170,812
Other non-current liabilities	7,268	10,414
Total liabilities	426,196	442,431
Commitments and contingencies Note 9
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and    outstanding at December 31, 2020 and December 31, 2019	0	0
Common stock, $0.01 par value, 125,000 shares authorized; 66,432 and 55,368 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively	665	554
Additional paid-in capital	4,260,443	3,568,184
Accumulated other comprehensive loss	(5,505)	(1,893)
Accumulated deficit	(2,900,547)	(2,281,852)
Total stockholders' equity	1,355,056	1,284,993
Total liabilities and stockholders' equity	$ 1,781,252	$ 1,727,424