☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIESEXCHANGE ACT OF 1934 For the quarterly period endedSeptember 30,2025OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIESEXCHANGE ACT OF 1934 For the transition period fromtoCommission File Number:001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) TheNetherlands(State or other jurisdiction ofincorporation or organization) NotApplicable(I.R.S. EmployerIdentification No.) Uppsalalaan 173rd and 4th Floor3584 CTUtrechtTheNetherlands(Address of principal executive offices) +31 85016 2500(Registrant’s telephone number, including area code) N/A Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the SecuritiesExchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and(2) has been subject to such filing requirements for the past 90 days.Yes☒No☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submittedpursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that theregistrant was required to submit such files).Yes☒No☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smallerreporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reportingcompany,” and “emerging growth company” in Rule 12b-2 of the Exchange Act. Large accelerated filer☒Non-accelerated filer☐ Accelerated filer☐Smaller reporting company☐Emerging growth company☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period forcomplying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act).☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).Yes☐No☒ As of October 26, 2025, the registrant had75,844,579common shares, nominal value €0.09 per share, outstanding. PART I — FINANCIAL INFORMATION Item 1. Financial Statements 2Condensed Consolidated Balance Sheetsas of September 30, 2025 and December 31, 20242Condensed Consolidated Statements of Operations and Comprehensive Lossfor the three and nine months ended September 30, 2025 and 20243Condensed Consolidated Statements of Cash Flowsfor the nine months ended September 30, 2025 and 20244Condensed Consolidated Statements of Changes in Shareholders’ Equityfor the three and nine months ended September 30, 2025 and 20245Notes to Condensed Consolidated Financial Statements6Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations23Item 3. Quantitative and Qualitative Disclosures About Market Risk32Item 4. Controls and Procedures32PART II — OTHER INFORMATIONItem 1. Legal Proceedings33Item 1A. Risk Factors33Item 5. Other Information89Item 6. Exhibits89Signatures91 CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS This Quarterly Report on Form 10-Q contains forward-looking statements within the meaning of the safe harbor provisions ofSection 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of1934, as amended, or the Exchange Act. All statements other than statements of historical facts contained in this Quarterly Reporton Form 10-Q are forward-looking statements. In some cases, you can identify forward-looking statements by terms such as “may,”“will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,”“predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-lookingstatements contain these words. Forward-looking statements contained in this Quarterly Report on Form 10-Q, including withoutlimitation statements regarding the planned completion of the transactions contemplated by the transaction agreement, dated as ofSeptember 29, 2025, entered into with Genmab A/S (Genmab) and Genmab Holding II B.V., a wholly owned subsidiary ofGenmab (Purchaser), and related timing, and the potential benefits and effects of the proposed transactions, our plans to developand commercialize our product candidates, the timing of our ongoing or planned clinical trials, the planned announcement of datafrom our clinical trials and related timing, the timing of and our ability to obtain and maintain regulatory approvals, the potentialimpact of any economic conditions and the global geopolitical landscape, including global instability due to United States politicalenvironment, disruptions and extreme volatility in th