This Amendment No. 1 (this “Amendment”) to Schedule
14D-9 amends and supplements the Solicitation/ Recommendation Statement on Schedule 14D-9 previously filed by Day One Biopharmaceuticals, Inc., a Delaware corporation
(“Day One” or the “Company”) with the Securities and Exchange Commission (the “SEC”) on March 26, 2026 (the “Schedule 14D-9”),
relating to the cash tender offer (the “Offer”) by Servier Detroit Inc. (“Purchaser”), a Delaware corporation and a direct wholly owned subsidiary of Servier Pharmaceuticals LLC, a Delaware limited liability
company (“Parent”), which is an indirect wholly owned subsidiary of Servier S.A.S., a French société par actions simplifiée (“Servier”
and together with Purchaser and Parent, the “Servier Parties”), to purchase all of the issued and outstanding shares of Day One’s common stock, par value $0.001 per share (“Shares”), at a purchase price of
$21.50 per Share (the “Offer Price”), net to the seller in cash, without interest thereon, and less any applicable tax withholding, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated as of
March 26, 2026 (as may be amended or supplemented from time to time, the “Offer to Purchase”) and the related Letter of Transmittal (as may be amended or supplemented from time to time, the “Letter of
Transmittal”), and pursuant to the Agreement and Plan of Merger, dated as of March 6, 2026 (as it may be amended from time to time, the “Merger Agreement,” and the transactions contemplated therein, the
“Transactions”), by and among Day One, Parent, Purchaser, and Servier.
Except as otherwise set forth in this Amendment, the
information set forth in the Schedule 14D-9 remains unchanged and is incorporated herein by reference to the extent relevant to the items in this Amendment. Capitalized terms used but not defined herein have
the meanings ascribed to them in the Schedule 14D-9.
Item 8. Additional Information
The subsection of Item 8 of the Schedule 14D-9 entitled “Regulatory Approvals—U.S. Antitrust
Compliance” is hereby amended as follows:
On page 51, the final full paragraph is amended and restated as follows (new language underlined;
deleted language struck through):
Parent and Day One expect to filed their respective Premerger Notification and Report Forms
with the FTC and Antitrust Division on March 26, 2026.
On April 7, 2026, the FTC granted a request for the early termination of the waiting
period under the HSR Act, effective April 7, 2026 at 1:37 p.m., Eastern Time. Accordingly, the condition to the Offer requiring that the waiting period (or any extension thereof) applicable to the Offer under the HSR Act shall have expired or
been terminated has been satisfied. The Offer continues to be subject to the remaining conditions set forth in Section 15 of the Offer to Purchase.
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