Company: SNY
Filing Date: 2025-10-29
Form Type: 424B5
Source: 0001193125-25-255563
Chunk: 9

Company: Sanofi
Filing Date: 2025-10-29
Form: 424B5
Chunk 9
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 and information previously incorporated by reference herein and therein. |

The information that we incorporate by reference is an important part of this prospectus supplement and the attached prospectus. Each document incorporated by reference is current only as of the date of such document, and the incorporation by reference of such documents shall not create any implication that there has been no change in our affairs since the date thereof or that the information contained therein is current as of any time subsequent to its date. Any statement contained in such incorporated documents shall be deemed to be modified or superseded for the purpose of this prospectus supplement and the attached prospectus to the extent that a subsequent statement contained in another document we incorporate by reference at a later date modifies or supersedes that statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus. We incorporate herein by reference:

| • |     | Our Annual Report on Form                                                                                      
 20-F for the year ended December 31, 2024 filed with the SEC on February 13, 2025 (the “2024 Form 20-F”) (File 
 No. 001-31368);                                                                                                |

| • |     | Any document filed in the future with the SEC under Sections 13(a) and 13(c) or 15(d) of the Exchange Act after                                                                                                                                           
 the date of this prospectus supplement and the attached prospectus and until this offering is completed. Any report on Form 6-K that we furnish to the SEC on or after the date of this prospectus supplement (or                                         
 portions thereof) is incorporated by reference in this prospectus supplement and the attached prospectus only to the extent that the report expressly states that we incorporate it (or such portions) by reference in this prospectus supplement and the 
 attached prospectus and that it is not subsequently superseded.                                                                                                                                                                                           |

The consolidated financial statements contained in the 2024 Form 20-Fhave been prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB) and with IFRS as endorsed by the European Union, as of December 31, 2024. S-4

You may request a copy of documents incorporated by reference at no cost, by contacting us
by telephone or in writing at the following address and telephone number: Investor Relations, 46, avenue de la Grande Armée, 75017 Paris, France, email: investor.relations@