ORGANIZATION, BASIS OF PRESENTATION, AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - (Tables)

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Schedule of Revenue from Strategic Partnering Collaboration Agreements and Research Activity Grants as a Percentage of Total Revenues

Revenues from major collaboration agreements and research activity grants as a percentage of total revenues were as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Biogen	38	%	—		24	%	—
Kite Pharma, Inc.	34	%	52	%	42	%	61	%
Pfizer	18	%	26	%	21	%	16	%
Sanofi	8	%	17	%	7	%	18	%

Schedule of Cash and Cash Equivalents

A reconciliation of cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets to the amounts reported within the accompanying Condensed Consolidated Statements of Cash Flows was as follows (in thousands):

	June 30, 2020		December 31, 2019		June 30, 2019		December 31, 2018
Cash and cash equivalents	$	467,443	$	80,428	$	169,222	$	140,418
Current restricted cash	—		—		2,000		—
Non-current restricted cash	1,500		1,500		1,500		3,500
Cash, cash equivalents and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows	$	468,943	$	81,928	$	172,722	$	143,918

Restrictions on Cash and Cash Equivalents

A reconciliation of cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets to the amounts reported within the accompanying Condensed Consolidated Statements of Cash Flows was as follows (in thousands):

	June 30, 2020		December 31, 2019		June 30, 2019		December 31, 2018
Cash and cash equivalents	$	467,443	$	80,428	$	169,222	$	140,418
Current restricted cash	—		—		2,000		—
Non-current restricted cash	1,500		1,500		1,500		3,500
Cash, cash equivalents and restricted cash as reported within the accompanying Condensed Consolidated Statements of Cash Flows	$	468,943	$	81,928	$	172,722	$	143,918