This Amendment No. 2 (this “Amendment”) amends and supplements the Tender Offer
Statement on Schedule TO filed with the Securities and Exchange Commission on October 12, 2021 (together with any subsequent amendments and supplements thereto, the “Schedule TO”), by Astros Merger Sub, Inc., a Delaware
corporation (“Purchaser”) and a wholly owned subsidiary of Merck Sharp & Dohme Corp., a New Jersey corporation (“Parent”), and Parent. The Schedule TO relates to the offer by Purchaser to purchase all of
the outstanding shares of common stock, par value $0.001 per share (the “Shares”), of Acceleron Pharma Inc., a Delaware corporation (“Acceleron”), at a purchase price of $180.00 per Share (the “Offer
Price”), net to the seller in cash, without interest and less any applicable tax withholding, 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 to the Schedule TO as Exhibits (a)(1)(A) and (a)(1)(B), respectively.
Except as otherwise set forth in this Amendment, the information set forth
in the Schedule TO 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 TO.
Item 11. Additional Information.
The
disclosure in the Offer to Purchase and Item 11 of the Schedule TO is hereby further amended and supplemented by adding the following new paragraph after the second paragraph in Section 16—“Certain Legal Matters; Regulatory
Approvals – Foreign Regulatory Filings in Germany and Austria” of the Offer to Purchase:
“On November 5, 2021, the FCO issued an
unconditional phase 1 clearance letter with respect to the Offer and the Merger, and the relevant review period for the Austrian competition authorities expired on the same day. Accordingly, the condition to the Offer relating to the receipt of
approvals under antitrust laws in Germany and Austria applicable to the transactions under the Merger Agreement has been satisfied.”
The disclosure
in the Offer to Purchase and Item 11 of the Schedule TO is hereby amended and supplemented by deleting the first and second paragraphs of the subsection titled “Certain Litigation” in Section 16—“Certain Legal
Matters; Regulatory Approvals” of the Offer to Purchase and replacing them with the following paragraphs:
“Between October 13, 2021
and November 5, 2021, ten complaints were filed in the United States District Court for the Southern District of New York, the United States District Court for the District of Delaware, the United States District Court for the Eastern District
of Pennsylvania and the United States District Court for the Eastern District of New York by putative stockholders of Acceleron: Wang v. Acceleron Pharma Inc. et al., No.
1:21-cv-08430, filed October 13, 2021 (S.D.N.Y.); Finger v. Acceleron Pharma Inc. et al., No.
1:21-cv-08615, filed October 20, 2021 (S.D.N.Y.); Wilson v. Acceleron Pharma Inc. et al., No.
1:21-cv-01473, filed October 20, 2021 (D. Del.); Ciccotelli v. Acceleron Pharma Inc. et al, No.
1:21-cv-08638, filed October 21, 2021 (S.D.N.Y) (the “Ciccotelli Action”); Nagel v. Acceleron Pharma Inc. et al., No. 1:21-cv-08644, filed October 21, 2021 (S.D.N.Y.); Whitfield v. Acceleron Pharma Inc. et al., No.
2:21-cv-04628, filed October 21, 2021 (E.D. Pa.); Combs v. Acceleron Pharma Inc. et al., No.
1:21-cv-05874, filed October 21, 2021 (E.D.N.Y.); Kulish v. Acceleron Pharma Inc. et al., No.
1:21-cv-08676, filed October 22, 2021 (S.D.N.Y.); Kent v. Acceleron Pharma Inc. et al., No.
1:21-cv-08861, filed October 29, 2021 (S.D.N.Y.); and Reed v. Acceleron Pharma Inc. et al., No.
1:21-cv-09189, filed November 5, 2021 (S.D.N.Y) (collectively, the “Complaints”). All of the Complaints name Acceleron and the members of the
Acceleron Board as defendants, and the complaint in the Ciccotelli Action also names Parent and Purchaser as defendants. The Complaints assert claims under the federal securities laws in connection with the Schedule
14D-9 that was filed with the SEC by Acceleron on October 12, 2021, alleging that the document contains materially incomplete and misleading information. The Complaints seek, among other relief,
injunctive relief to prevent consummation of the transactions contemplated by the Merger Agreement until the alleged disclosure violations are cured, as well as damages and attorneys’ fees and costs.
If additional similar complaints are filed, absent new or different allegations that are material, we will not necessarily announce such additional
filings.”