SC 14D9/A

This Amendment No. 1 (this “Amendment”) amends and supplements the Solicitation/Recommendation Statement on Schedule 14D-9 (as amended or supplemented from time to time, the “Schedule 14D-9”) filed by Merus N.V., a public limited liability company (naamloze vennootschap) organized under the laws of The Netherlands (“Merus”), with the U.S. Securities and Exchange Commission (the “SEC”) on October 21, 2025, relating to the tender offer by Genmab Holding II B.V., a private limited liability company (besloten vennootschap met beperkte aansprakelijkheid) organized under the laws of The Netherlands (“Purchaser”) and a wholly owned subsidiary of Genmab A/S, a public limited liability company (Aktieselskab) organized under the laws of Denmark (“Genmab”), to purchase all of the issued and outstanding common shares, nominal value €0.09 per share (each, a “Common Share,” and collectively, the “Common Shares”), in the capital of Merus in exchange for an amount in cash equal to $97.00 per Common Share (such amount, the “Offer Consideration”), less any applicable withholding taxes and without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated October 21, 2025 (as it may be amended or supplemented from time to time, the “Offer to Purchase”) and in the letter of transmittal that accompanies the Offer to Purchase (the “Letter of Transmittal,” and together with the Offer to Purchase and other related materials, as each may be amended or supplemented from time to time, the “Offer”). The Offer is described in a Tender Offer Statement on Schedule TO (as amended, supplemented or otherwise modified from time to time, the “Schedule TO”) filed by Genmab and Purchaser with the SEC on October 21, 2025. The Offer to Purchase and Letter of Transmittal are filed as Exhibits (a)(1)(A) and (a)(1)(B), respectively, to the Schedule 14D-9.

Except to the extent specifically provided in this Amendment, the information set forth in the Schedule 14D-9 remains unchanged. Capitalized terms used, but not otherwise defined, in this Amendment shall have the meanings ascribed to them in the Schedule 14D-9.

Item 8 (Additional Information).

Item 8 (Additional Information) of the Schedule 14D-9 is hereby amended and supplemented by adding the following paragraph to the end of the subsection entitled “Regulatory and Other Approvals – Antitrust”:

On October 28, 2025, each of Purchaser and Merus filed Premerger Notification and Report Forms under the HSR Act with the FTC and the Antitrust Division in connection with Purchaser’s proposed acquisition of Common Shares pursuant to the Offer. As a result, the required fifteen (15) calendar-day waiting period under the HSR Act with respect to the Offer will expire at 11:59 p.m., New York City time, on November 12, 2025, unless Purchaser withdraws its Premerger Notification and Report Forms before the expiration of the initial fifteen (15) calendar-day waiting period and refiles it thereafter, or the FTC or the Antitrust Division shortens or extends the waiting period by granting Early Termination or issuing a Second Request, respectively, prior to expiry of the initial waiting period.


MERUS N.V.

By:		/s/ Sven A. Lundberg
		Name: Sven (Bill) Ante Lundberg, M.D.
		Title: President and Chief Executive Officer
		Dated: October 31, 2025