UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to MERUS N.V. (Exact name of Registrant as specified in its Charter) The Netherlands Not Applicable (State or other jurisdiction of incorporation or organization) ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of inco ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of inc ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-37773 MERUS N.V. (Exact name of Registrant as specified in its Charter) The Netherlands Not Applicable (State or other jurisdiction o ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of inco ...

Company Overview - Merus is developing multispecific antibody therapies for oncology, based on the human IgG format[6, 46] - The company's Multiclonics® platform enables high-throughput discovery and engineering of Biclonics® and Triclonics™[6, 9, 45, 46] - Merus has strategic collaborations and license agreements with Incyte, Betta, Simcere, and Ono[6, 43, 46] - Zenocutuzumab (Zeno) NRG-1 phase 1/2 clinical data update is expected by the end of 2020[6, 23, 46] Zenocutuzumab (MCLA-128) Program - Zenocutuzumab (HER3 x HER2 bispecific) shows promising early clinical activity in patients with NRG1+ cancers[6, 12] - In a pancreatic cancer patient, Zeno treatment resulted in a 44% decrease in CA19-9 levels and a 54% reduction in size[17] - Clinical data reported by MSKCC at the 2019 AACR-NCI-EORTC International Conference showed a 54% partial response (PR) in pancreatic cancer and 25% stable disease (SD) and 41% PR in lung cancer[19] - The eNRGy clinical trial and Early Access Program for Zeno in NRG1+ cancers are ongoing[12, 22, 23] Other Pipeline Programs - MCLA-158 (Lgr5 x EGFR bispecific) is in a global phase 1 clinical trial for solid tumors and demonstrates superior selectivity for tumor-derived organoids[11, 29, 31] - MCLA-145 (CD137 x PD-L1 bispecific) is in a global phase 1 trial in partnership with Incyte, targeting PD-L1 positive tumor cells[11, 32, 34, 35]

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2020 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37773 MERUS N.V. (Exact name of registrant as specified in its charter) The Netherlands Not Applicable (State or other jurisdiction of incorp ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-37773 MERUS N.V. (Exact name of Registrant as specified in its Charter) The Netherlands Not Applicable (State or other jurisdiction o ...