This Amendment No. 3 (this “Amendment”) amends and supplements the Tender Offer
Statement on Schedule TO (together with any amendments and supplements thereto, including this Amendment, the “Schedule TO”) filed by (i) GSK plc, a public limited company organized under the laws of England and Wales
(“Ultimate Parent”), (ii) GlaxoSmithKline LLC, a Delaware limited liability company and an indirect wholly-owned subsidiary of Ultimate Parent (“Parent”), and (iii) Harmony Row Acquisition Co., a Delaware
corporation (“Purchaser”) and a direct wholly-owned subsidiary of Parent. The Schedule TO relates to the offer by Purchaser to purchase all of the issued and outstanding shares of the Class A Common Stock, par value $0.0001
per share (the “Class A Shares”), and Class B Common Stock, par value $0.0001 per share (the “Class B Shares” and, together with the Class A Shares, the
“Shares”), of Nuvalent, Inc., a Delaware corporation (the “Company”), for $124.00 per Share, net to the seller in cash, without interest (such consideration as it may be increased from time to time pursuant to
the terms of the Merger Agreement (as defined below), the “Offer Price”), subject to any applicable withholding taxes, and upon the terms and subject to the conditions set forth in the Offer to Purchase, dated June 24, 2026
(together with any amendments or supplements thereto, the “Offer to Purchase”) and in the accompanying letter of transmittal (together with any amendments or supplements thereto, the “Letter of Transmittal”
which, together with the Offer to Purchase and other related materials, as they may be amended or supplemented from time to time, collectively constitute the “Offer”), copies of which are annexed to and filed with the Schedule TO
as Exhibits (a)(1)(A) and (a)(1)(B), respectively.

All information contained in the Offer to Purchase (including Schedule I to the Offer to Purchase) and
the accompanying Letter of Transmittal is hereby expressly incorporated herein by reference in response to Items 1 through 9 and Item 11 of the Schedule TO and is supplemented by the information specifically provided in this Amendment. This
Amendment should be read together with the Schedule TO. Capitalized terms used and not otherwise defined in this Amendment have the meanings given to such terms in the Offer to Purchase.

Item 1 through 9; Item 11.

The Offer to
Purchase and Items 1 through 9 and Item 11 of the Schedule TO, to the extent such Items incorporate by reference the information contained in the Offer to Purchase, are hereby amended and supplemented as follows:

The second paragraph of the subsection entitled “U.S. Antitrust Compliance” in Section 16 – “Certain Legal Matters; Regulatory
Approvals” is amended and supplemented by replacing the second paragraph with the following:

“Under the HSR Act, the purchase of Shares in
the Offer may not be completed until the expiration of a 15-calendar-day waiting period following the filing of certain required information and documentary
material concerning the Offer (and the Merger) with the FTC and the Antitrust Division, unless the waiting period is earlier terminated by the FTC. The waiting period under the HSR Act expired, effective July 9, 2026, at 11:59 P.M. Eastern
Time. Accordingly, the HSR Condition to the Offer has been satisfied.”

 

2