This Amendment No. 2 (this “Amendment”) amends and supplements the Tender Offer
Statement on Schedule TO filed by (i) Thunder Acquisition Corp., a Delaware corporation (“Purchaser”) and a wholly owned indirect subsidiary of Sanofi, a French société anonyme (“Parent”),
(ii) Parent, and (iii) Aventis Inc., a Delaware corporation and a direct wholly owned subsidiary of Parent and direct parent of Purchaser (“Aventis”) on December 23, 2019 (together with any subsequent amendments or
supplements thereto, including this Amendment, the “Schedule TO”), relating to the offer by Purchaser to purchase all of the outstanding shares of common stock, par value, $0.001 per share (the “Shares”), of
Synthorx, Inc., a Delaware corporation (the “Company”), at a purchase price of $68.00 per Share (the “Offer Price”) net to the seller in cash, without any interest thereon and net of any applicable withholding
taxes, on the terms and subject to the conditions set forth in the Offer to Purchase and in the related Letter of Transmittal, copies of which are attached hereto as Exhibits (a)(1)(A) and (a)(1)(B), respectively.
All information set forth in the Offer to Purchase, including Schedule I thereto, is incorporated by reference herein in response to Items 1 through 9 and
Item 11 of this Schedule TO and is supplemented by the information specifically provided in this Amendment.
Items 1 through 9 and Item 11.
Items 1 through 9 and Item 11, to the extent such Item incorporates by reference the information contained in the Offer to Purchase, is hereby amended and
supplemented as set forth below:
1. The second paragraph of Section 15 “Conditions to the Offer” is hereby deleted in its entirety
and replaced with the following:
“The Offer is not subject to any financing condition. Purchaser will not be required to accept for payment or,
subject to any applicable rules and regulations of the SEC, including Rule 14e-l(c) under the Exchange Act (relating to Purchaser’s obligation to pay for or return tendered Shares promptly after the
termination or withdrawal of the Offer), to pay for, any Shares tendered pursuant to the Offer and may delay the acceptance for payment of or, subject to any applicable rules and regulations of the SEC, the payment for, any tendered Shares, and
(subject to the provisions of the Merger Agreement) may amend the Offer as otherwise permitted by the Merger Agreement if, at one minute past 11:59 p.m. Eastern Time on any scheduled Expiration Date (as it may be extended or subject to any
requirements to extend), (i) the Minimum Condition has not been satisfied, or (ii) any of the following other conditions shall not be satisfied or (to the extent permitted by applicable law) waived:”
2. The subsection “Legal Proceedings Relating to the Tender Offer” under Section 16 “Certain Legal Matters; Regulatory
Approvals” of the Offer to Purchase is hereby amended and supplemented by adding the following to the end of such section:
“On January 7,
2020, Norman Blayer, a purported stockholder of the Company, filed a lawsuit in the United States District Court for the Eastern District of New York captioned Norman Blayer v. Synthorx, Inc., et al., Case No. 1:20-cv-00130 (the “Blayer Action”). The Blayer Action names the Company and members of the Company Board as defendants. The Blayer Action alleges, among other things, that all defendants
violated Sections 14(e) and 14(d)(4) of the Exchange Act by omitting and/or misrepresenting certain material facts related to the transaction described in the Schedule 14D-9 filed by the Company. The Blayer
Action further alleges that the members of the Company Board violated Section 20(a) of the Exchange Act. As relief, the Blayer Action seeks, among other things, to enjoin the defendants from proceeding with, consummating or closing the Offer
and the Merger, rescinding the transaction or awarding rescissory damages should it not be enjoined, and an award of attorneys’ and experts’ fees.”