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Revenues - Revenues from Anti-CD20 Therapeutic Programs (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Disaggregation of Revenue [Line Items] |  |
Total revenues from anti-CD20 therapeutic programs | $ 2,290.5 | $ 2,463.0
Genentech |  |
Disaggregation of Revenue [Line Items] |  |
Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA | 87.1 | 112.5
Other revenues from anti-CD20 therapeutic programs | 4.2 | 3.4
Revenue from anti-CD20 therapeutic programs |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues from anti-CD20 therapeutic programs | 394.0 | 399.5
Royalty Attributed To OCREVUS |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues from anti-CD20 therapeutic programs | $ 302.7 | $ 283.6

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- Definition Other revenues from anti-CD20 therapeutic programs consists of revenue on sales of RITUXAN outside the U.S., which consist of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of Ocrevus. + References No definition available. + Details
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