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Collaborative and Other Relationships Collaborative and Other Relationships (Tables) | 3 Months Ended
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Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Summary of Activity Related to BAN2401 and Elenbecestat Collaboration | A summary of development expenses related to the BAN2401 and Elenbecestat Collaboration is as follows:
| For the Three Months Ended March 31,
(In millions) | 2019 |  | 2018
Total development expense incurred by the collaboration related to the advancement of BAN2401 and Elenbecestat | $ | 68.0 |  |  | $ | 52.2 |
Biogen's share of BAN2401 and Elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income | $ | 34.0 |  |  | $ | 26.1 |
Summary of Activity Related to Aducanumab Collaboration | A summary of development and sales and marketing expenses related to the Aducanumab Collaboration Agreement is as follows:
| For the Three Months Ended March 31,
(In millions) | 2019 |  | 2018
Total aducanumab development expense | $ | 162.5 |  |  | $ | 63.6 |
Biogen's share of aducanumab development expense reflected in research and development expense in our condensed consolidated statements of income | $ | 89.4 |  |  | $ | 63.6 |
Total aducanumab sales and marketing expense incurred by the collaboration | $ | 20.9 |  |  | $ | 7.1 |
Biogen's share of aducanumab sales and marketing expense reflected in selling, general and administrative expense our condensed consolidated statements of income | $ | 11.6 |  |  | $ | 3.9 |

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