Collaborative and Other Relationships (Tables)

9 Months Ended

Sep. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Activity Related to BAN2401 and Elenbecestat Collaboration

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2020		2019		2020		2019
Total development expense incurred by the collaboration related to the advancement of BAN2401 and elenbecestat	$	75.7	$	168.7	$	153.2	$	305.3
Biogen's share of BAN2401 and elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income	37.9		84.3		76.6		152.6
Total sales and marketing expense incurred by the collaboration	nm		10.2		6.3		24.8
Biogen's share of BAN2401 and elenbecestat sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	nm		5.1		3.2		12.4

Summary of Activity Related to Aducanumab Collaboration

A summary of development, sales and marketing and milestone expense related to the Aducanumab Collaboration Agreement is as follows:

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2020		2019		2020		2019
Total aducanumab development expense	$	37.5	$	4.7	$	92.5	$	170.5
Biogen's share of aducanumab development expense reflected in research and development expense in our condensed consolidated statements of income	20.6		2.6		50.9		93.8
Total aducanumab sales and marketing expense incurred by the collaboration	90.9		0.1		158.8		21.3
Biogen's share of aducanumab sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	51.3		—		88.8		11.7
Total aducanumab collaboration third party milestone expense	—		—		75.0		—
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income	—		—		33.8		—