Company: SNY
Filing Date: 2025-10-29
Form Type: 424B5
Source: 0001193125-25-255563
Chunk: 70

Company: Sanofi
Filing Date: 2025-10-29
Form: 424B5
Chunk 70
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 notes are subscribed or purchased under Section 275 of the SFA by a relevant person, which is:

| • |     | a corporation (which is not an accredited investor) (as defined in Section 4A of the SFA) the sole business                                           
 of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or |

| • |     | a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each 
 beneficiary is an individual who is an accredited investor,                                                  |

securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferable for six months after that corporation or that trust has acquired the notes under Section 275 of the SFA except:

| (i) | to an institutional investor or to a relevant person defined in Section 275(2) of the SFA, or to any 
 person arising from an offer referred to in Section 275(1A) or Section 276(4)(i) of the SFA;         |

| (ii) | where no consideration is or will be given for the transfer; |

| (iii) | where the transfer is by operation of law; or |

| (iv) | pursuant to Section 276(7) of the Securities and Futures Act. |

S-47

Switzerland

This prospectus supplement is not intended to constitute an offer or solicitation to purchase or invest in the notes. The notes may not be
publicly offered, sold or marketed, directly or indirectly, in Switzerland within the meaning of the Swiss Financial Services Act (“FinSA”), except to any investor that qualifies as a professional client within the meaning of the FinSA,
and no application has or will be made to admit the notes to trading on any trading venue (exchange or multilateral trading facility) in Switzerland. Neither this prospectus supplement nor any other offering or marketing material relating to the
notes constitutes a prospectus or a key information document (or an equivalent document) as such terms are understood pursuant to the FinSA, and neither this prospectus supplement nor any other offering or marketing material relating to the notes
may be publicly distributed or otherwise made publicly available in Switzerland, except to any investor that qualifies as a professional client within the meaning of the FinSA.

Neither this prospectus supplement nor any other