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Collaborative and Other Relationships - Summary of Activity Related to BAN2401 and Elenbecestat Collaboration (Details) - Eisai - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022
E2609 and BAN2401 |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |
Total development expense incurred by the collaboration related to the advancement of LEQEMBI | $ 107.9 | $ 77.0
Expense reflected within statements of income | 54.0 | 38.5
Selling, general and administrative | E2609 and BAN2401 |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |
Expense reflected within statements of income | 5.3 | 8.0
Expense incurred by the collaboration | $ 10.5 | 15.9
Selling, general and administrative | ADUHELM |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |
Expense reflected within statements of income |  | 50.9
Expense incurred by the collaboration |  | $ 95.0

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