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Collaborative and Other Relationships - Summary of Activity Related to BAN2401 and Elenbecestat Collaboration (Details) - E2609 and BAN2401 - Eisai - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |
Total development expense incurred by the collaboration related to the advancement of LEQEMBI | $ 90.6 | $ 86.2 | $ 177.9 | $ 194.1
Expense reflected within statements of income | 45.4 | 43.0 | 89.0 | 97.0
Selling, general and administrative |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |
Expense reflected within statements of income | 68.9 | 8.5 | 155.8 | 13.8
Expense incurred by the collaboration | $ 137.7 | $ 17.1 | $ 311.6 | $ 27.6

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