Company: SNY
Filing Date: 2025-10-29
Form Type: 424B5
Source: 0001193125-25-255563
Chunk: 12

Company: Sanofi
Filing Date: 2025-10-29
Form: 424B5
Chunk 12
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 share, the total equity value of Vigil represented approximately $470 million (on a fully diluted basis). In addition, Vigil’s shareholders received one CVR per Vigil share entitling the holder to receive a
deferred cash payment of $2.00, contingent upon the first commercial sales of VG-3927.

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On September 24, 2025, Sanofi Ventures announced an additional $625 million
multi-year capital commitment from Sanofi, increasing its total assets under management to over $1.4 billion. Sanofi Ventures is the corporate venture capital arm of Sanofi, investing in biotech and artificial intelligence/digital health
companies.

Our registered office is located at 46, avenue de la Grande Armée, 75017 Paris, France, and we can be contacted at the
following email address: investor.relations@sanofi.com; or the following telephone number: +33 1 53 77 40 00.

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THE OFFERING Please refer to “Description of the Notes” on page S-23of this prospectus supplement and “Description of Debt Securities We May Offer” in the attached prospectus for more information about the notes.

| Issuer | Sanofi |

| Notes Offered | $500,000,000 in principal amount of floating rate notes due 2027 (the “2027 floating rate notes”) |

| $500,000,000 in principal amount of floating rate notes due 2028 (the “2028 floating rate notes”) |

| $400,000,000 in principal amount of 3.750% notes due 2027 (the “2027 fixed rate notes”) |

| $400,000,000 in principal amount of 3.800% notes due 2028 (the “2028 fixed rate notes”) |

| $1,200,000,000 in principal amount of 4.200% notes due 2032 (the “2032 fixed rate notes”) |

| In this prospectus supplement, we refer to the 2027 floating rate notes and 2028 floating rate notes collectively as the “floating rate notes”. We refer to the 2027 fixed rate notes, the 2028 fixed rate 
 notes and the 2032 fixed rate notes collectively as the “fixed rate notes.” The floating rate notes and the fixed rate notes are collectively referred to as the “notes.”                                  |

PROVISIONS APPLICABLE TO THE FIXED RATE NOTES

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