This Amendment No. 2 to Schedule 14D-9 (the
“Amendment”) amends and supplements the Solicitation/Recommendation Statement on Schedule 14D-9 (as amended or supplemented from time to time, the “Schedule
14D-9”) previously filed by Synthorx, Inc., a Delaware corporation (“Synthorx” or the “Company”), with the Securities and Exchange Commission on December 23, 2019 relating to the
offer by Sanofi, a French société anonyme (“Sanofi”) and Thunder Acquisition Corp., a Delaware corporation and an indirect wholly owned subsidiary of Sanofi (“Purchaser”), to purchase all the issued and outstanding
shares of Synthorx’s common stock, $0.001 par value per share (the “Shares”), for a purchase price of $68.00 per Share in cash, without interest and subject to any required withholding of taxes, upon the terms and subject to the
conditions set forth in the Offer to Purchase, dated December 23, 2019, and in the related Letter of Transmittal, each of which may be amended or supplemented from time to time.
Except as otherwise set forth below, the information set forth in the Schedule 14D-9 remains unchanged
and is incorporated by reference as relevant to the items in this Amendment. Capitalized terms used and not defined herein shall have the meanings given to such terms in the Schedule 14D-9. This Amendment is
being filed to reflect certain updates as reflected below.
Explanatory Note
Following the announcement of the proposed acquisition of the Company by Sanofi (the “Proposed Transaction”) and as of the date of
this Amendment No. 2, two lawsuits have been filed by purported stockholders of the Company challenging the Proposed Transaction. The first lawsuit, a putative class action complaint, is captioned Kent v. Synthorx, Inc., et al., No.
1:20-cv-00010 (D. Del. filed Jan. 3, 2020). The second lawsuit, brought by the plaintiff individually, is captioned Blayer v. Synthorx, Inc., et al., No. 1:20-cv-00130 (E.D.N.Y. filed Jan. 7, 2020). The Blayer complaint names as
defendants the Company and each member of the Company’s board of directors. The Kent complaint additionally names as defendants Sanofi and Purchaser.
While the Company believes that the disclosures set forth in the Schedule 14D-9 comply fully with all
applicable law and denies the allegations in the pending actions described above, in order to moot plaintiffs’ disclosure claims, avoid nuisance and possible expense and business delays, and provide additional information to its stockholders,
the Company has determined voluntarily to supplement certain disclosures in the Schedule 14D-9 related to plaintiffs’ claims with the supplemental disclosures set forth below (the “Supplemental
Disclosures”). These Supplemental Disclosures should be read in conjunction with the rest of the Schedule 14D-9, as amended, which we urge you to read in its entirety. Nothing in the Supplemental
Disclosures shall be deemed an admission of the legal merit, necessity or materiality under applicable laws of any of the disclosures set forth herein. To the contrary, the Company specifically denies all allegations in the complaints described
above that any additional disclosure was or is required or material. All page references used herein refer to pages in the Schedule 14D-9 before any additions or deletions resulting from the Supplemental
Disclosures.
Item 4. The Solicitation or Recommendation.
Item 4 of the Schedule 14D-9 is hereby amended and restated by deleting the paragraph under the heading
“Summary of Centerview Financial Analysis” on page 29 of the Schedule 14D-9 and replacing it with the following paragraph:
“The following is a summary of the material financial analyses prepared and reviewed with the Board in connection with Centerview’s
opinion, dated December 6, 2019. The summary set forth below does not purport to be a complete description of the financial analyses performed or factors considered by, and underlying the opinion of, Centerview, nor does the order of the
financial analyses described represent the relative importance or weight given to those financial analyses by Centerview. Centerview may have deemed various assumptions more or less probable than other assumptions, so the reference ranges resulting
from any particular portion of the analyses summarized below should not be taken to be Centerview’s view of the actual value of Synthorx. Some of the summaries of the financial analyses set forth below include information presented in tabular
format. In order to fully understand the financial analyses, the tables must be read together with the text of each summary, as the tables alone do not constitute a complete description of the financial analyses performed by Centerview. Considering
the data in the tables below without considering all financial analyses or factors or the full narrative description of such analyses or factors, including the methodologies and assumptions underlying such analyses or factors, could create a
misleading or incomplete view of the processes underlying Centerview’s financial analyses and its opinion. In performing its analyses, Centerview made numerous assumptions with respect to industry performance, general business and economic
conditions and other matters, many of which are beyond the control of Synthorx or any other parties to the Transactions. None of Synthorx, Sanofi, Purchaser or Centerview or any other person assumes responsibility if future results are materially
different from those discussed. Any estimates contained in these analyses are not necessarily indicative of actual values or predictive of future results or values, which may be significantly more or less favorable than as set forth below. In
addition, analyses relating to the value of Synthorx do not purport to be appraisals or reflect the prices at which Synthorx may actually be sold. Accordingly, the assumptions and estimates used in, and the results derived from, the financial
analyses are inherently subject to substantial uncertainty. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on or before December 6, 2019
(the last trading day before the public announcement of the Transactions) and is not necessarily indicative of current market conditions. The implied per share equity value ranges described below were based on Synthorx’s fully diluted Shares
outstanding as of December 6, 2019, calculated based on approximately 32.4 million Shares outstanding and, using the treasury stock method, the dilutive impact of approximately 4.6 million options with a weighted average exercise
price of $7.83 as of December 6, 2019 as set forth in the Internal Data.”