LGR5

- Petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC interim clinical data selected for poster presentation - Conference call on Thursday, May 22 at 5:30 p.m. ET to discuss full ASCO® data set UTRECHT, The Netherlands and CAMBRIDGE, Mass., April 23, 2025 (GLOBE NEWSWIRE) -- Merus N.V. (Nasdaq: MRUS) (Merus, the Company, we, or our), an oncology company developing innovative, full-length multispecific antibodies and antibody drug conjugates (Biclonics®, Triclonics® and ADClonics®), today announced the acceptance of an abstract for presentation at the 2025 American Society of Clinical Oncology® (ASCO®) Annual Meeting, being held in Chicago, Illinois on May 30- June 3, 2025. An updated analysis of the interim clinical data from the phase 2 trial of petosemtamab with pembrolizumab as 1L treatment of PD-L1+ recurrent/metastatic (r/m) head and neck squamous cell carcinoma (HNSCC) will be presented in a poster at 2025 ASCO®. The presentation will include data on the entire 45 patient dataset and follows the early clinical efficacy and encouraging safety data previously presented at 2024 ASCO®. “We continue to believe that petosemtamab has the potential to be a first and best-in-class, practice-changing medicine for the treatment of r/m HNSCC. While the decision to have a poster presentation at 2025 ASCO® was based on the limited data included in the submitted abstract, we are very much looking forward to sharing the robust updated interim phase 2 data, on the entire 45 patient data set, on the upcoming investor conference call and in our presentation at the conference,” said Bill Lundberg, M.D., President, Chief Executive Officer of Merus. “We believe petosemtamab continues to demonstrate substantial clinical activity superior to historical controls, based on the magnitude and consistency of efficacy, not just on one endpoint, but across ORR, PFS and OS in the overall population and within important subgroups of HPV disease and PD-L1 expression levels. On the back of these data, and the strong execution of our phase 3 trials, we believe petosemtamab has the potential to become a new standard of care for r/m HNSCC.” Poster presentation: Title: Petosemtamab (MCLA-158) with pembrolizumab as first-line (1L) treatment of PD-L1+ recurrent/metastatic (r/m) head and neck squamous cell carcinoma (HNSCC): Phase 2 trial Abstract #: 6024 Poster Board: 432 Session Title: Head and Neck Cancer Session Date and Time: June 2, 2025, 9:00-12:00 CT The abstracts will be available on the ASCO® website on May 22, 2025 at 5:00 p.m. ET. The full presentation will be available on the Merus website at the start of the session. Company Conference Call and Webcast Information Merus will hold a conference call and webcast for investors on Thursday, May 22, 2025 at 5:30 p.m. ET. A replay will be available after the completion of the call in the Investors and Media section of our website for a limited time. Date & Time: May 22, 2025 at 5:30 p.m. ET Webcast link: Available on our website Dial-in: Toll Free: (800) 715-9871 / International: (646) 307-1963 Conference ID: 7517301 or Merus NV call About Petosemtamab Petosemtamab, or MCLA-158, is a Biclonics® low-fucose human full-length IgG1 antibody targeting the epidermal growth factor receptor (EGFR) and the leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5). Petosemtamab is designed to exhibit three independent mechanisms of action including inhibition of EGFR-dependent signaling, LGR5 binding leading to EGFR internalization and degradation in cancer cells, and enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) activity. About Head and Neck Cancer Head and neck squamous cell carcinoma (HNSCC) describes a group of cancers that develop in the squamous cells that line the mucosal surfaces of the mouth, throat, and larynx. These cancers begin when healthy cells change and grow in an unchecked manner, ultimately forming tumors. HNSCC is generally associated with tobacco consumption, alcohol use and/or HPV infections, depending on where they develop geographically. HNSCC is the sixth most common cancer worldwide and it is estimated that there were more than 930,000 new cases and over 465,000 deaths from HNSCC globally in 2020.1 The incidence of HNSCC continues to rise and is anticipated to increase by 30% to more than 1 million new cases annually by 2030.2 HNSCC is a serious and life-threatening disease with poor prognosis despite currently available standard of care therapies. 1 Sung et al. CA Cancer J Clin, 71:209-49, 2021; 2 Johnson, D.E., Burtness, B., Leemans, C.R. et al. Head and neck squamous cell carcinoma. Nat Rev Dis Primers 6(1):92, 2020 About LiGeR-HN1 LiGeR-HN1, a phase 3 trial, will evaluate the safety and efficacy of petosemtamab in combination with pembrolizumab, compared to pembrolizumab in 1L PD-L1+ r/m HNSCC patients. The trial is open to adult patients eligible to receive pembrolizumab as 1L monotherapy with tumors expressing PD-L1, CPS ≥1. The primary endpoints are overall response rate as assessed by BICR based on RECIST v1.1 and overall survival. Secondary endpoints are duration of response and progression free survival. Merus plans to enroll approximately 500 patients in the trial. About Merus N.V. Merus is an oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as Multiclonics®. Multiclonics® are manufactured using industry standard processes and have been observed in preclinical and clinical studies to have several of the same features of conventional human monoclonal antibodies, such as long half-life and low immunogenicity. For additional information, please visit Merus’ website and LinkedIn. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding the clinical development of our clinical candidates, including petosemtamab, future clinical trial results or interim data, clinical activity and safety profile, and development plans in the on-going trials and described in forthcoming posters or presentations; our belief that petosemtamab has the potential to be a first and best-in-class, practice-changing medicine for the treatment of r/m HNSCC; our sharing the robust updated interim phase 2 data, on the entire 45 patient data set, on the upcoming investor conference call and in our presentation at the conference; our belief that petosemtamab continues to demonstrate substantial clinical activity superior to historical controls, based on the magnitude and consistency of efficacy, not just on one endpoint, but across ORR, PFS and OS in the overall population and within important subgroups of HPV disease and PD-L1 expression levels; our execution of our phase 3 trials; and our belief that petosemtamab has the potential to become a new standard of care for r/m HNSCC. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our need for additional funding, which may not be available and which may require us to restrict our operations or require us to relinquish rights to our technologies or antibody candidates; potential delays in regulatory approval, which would impact our ability to commercialize our product candidates and affect our ability to generate revenue; the lengthy and expensive process of clinical drug development, which has an uncertain outcome; the unpredictable nature of our early stage development efforts for marketable drugs; potential delays in enrollment of patients, which could affect the receipt of necessary regulatory approvals; our reliance on third parties to conduct our clinical trials and the potential for those third parties to not perform satisfactorily; impacts of the volatility in the global economy, including global instability, including the ongoing conflicts in Europe and the Middle East; we may not identify suitable Biclonics® or bispecific antibody candidates under our collaborations or our collaborators may fail to perform adequately under our collaborations; our reliance on third parties to manufacture our product candidates, which may delay, prevent or impair our development and commercialization efforts; protection of our proprietary technology; our patents may be found invalid, unenforceable, circumvented by competitors and our patent applications may be found not to comply with the rules and regulations of patentability; we may fail to prevail in potential lawsuits for infringement of third-party intellectual property; and our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. These and other important factors discussed under the caption “Risk Factors” in our Annual Report on Form 10-K for the period ended December 31, 2024, filed with the Securities and Exchange Commission, or SEC, on February 27, 2025, and our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change, except as required under applicable law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. Multiclonics®, Biclonics® and Triclonics® are registered trademarks of Merus N.V. Source: Merus N.V.

- Phase 3 registrational trials evaluating petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC and petosemtamab monotherapy in 2/3L r/m HNSCC enrolling; expected to be substantially enrolled by YE25 - Petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC phase 2 trial ongoing with clinical data update planned for 1H25 - Petosemtamab evaluation in mCRC ongoing in combination with standard chemotherapy in 1L and 2L and monotherapy in 3L+; mCRC initial clinical data planned for 2H25 - Based on the Company’s current operating plan, existing cash, cash equivalents and marketable securities expected to fund Merus’ operations into 2028 UTRECHT, The Netherlands and CAMBRIDGE, Mass. , Feb. 27, 2025 (GLOBE NEWSWIRE) -- Merus N.V. (Nasdaq: MRUS) (Merus, the Company, we, or our), an oncology company developing innovative, full-length multispecific antibodies and antibody drug conjugates (Biclonics®, Triclonics® and ADClonics®), today announced financial results for the fourth quarter and full year and provided a business update. “We believe that petosemtamab’s receipt of two Breakthrough Therapy designations by the FDA – previously as monotherapy in the 2L+ treatment of r/m HNSCC and very recently, based on updated clinical efficacy, durability and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC, indicates the potential for these treatment regimens to demonstrate substantial improvement over available therapies,” said Bill Lundberg, M.D., President, Chief Executive Officer of Merus. “We look forward to sharing the updated clinical data, including durability, for petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC, for the full phase 2 cohort, in the first half of 2025.” Petosemtamab (MCLA-158: EGFR x LGR5 Biclonics®): Solid TumorsLiGeR-HN1 phase 3 trial in 1L PD-L1+ r/m head and neck squamous cell carcinoma (HNSCC) and LiGeR-HN2 phase 3 trial in 2/3L r/m HNSCC enrolling – we expect both trials to be substantially enrolled by YE25; clinical update on phase 2 trial in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC planned for 1H25; phase 2 trial in 1L, 2L and 3L+ metastatic colorectal cancer (mCRC) enrolling; mCRC initial clinical data planned for 2H25 In February 2025 , the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy designation (BTD) for petosemtamab in combination with pembrolizumab for the first-line treatment of adult patients with r/m PD-L1+ HNSCC with CPS ≥ 1. This designation was detailed in our press release, Petosemtamab granted Breakthrough Therapy designation by the U.S. FDA for 1L PD-L1 positive head and neck squamous cell carcinoma ( February 18 , 2025). In September 2024 , Merus announced the first patient was dosed in LiGeR-HN1, a phase 3 trial evaluating the efficacy and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC compared to pembrolizumab. In this trial, patients will be randomized to petosemtamab plus pembrolizumab or pembrolizumab monotherapy. This was detailed in our press release, Merus Announces First Patient Dosed in LiGeR-HN1, a Phase 3 Trial Evaluating Petosemtamab in Combination with Pembrolizumab in 1L r/m HNSCC ( September 30 , 2024). Merus provided an interim clinical update on petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC at the American Society of Clinical Oncology ® (ASCO®) Annual Meeting 2024, demonstrating a 67% response rate among 24 evaluable patients. The oral presentation was detailed in our press release, Merus’ Petosemtamab in Combination with Pembrolizumab Interim Data Demonstrates Robust Response Rate and Favorable Safety Profile in 1L r/m HNSCC ( May 28, 2024 ). A clinical update on this cohort is planned for 1H25. In July 2024 , Merus announced the first patient was dosed in LiGeR-HN2, a phase 3 trial evaluating the efficacy and safety of petosemtamab in 2/3L HNSCC compared to standard of care. In this trial, patients will be randomized to petosemtamab monotherapy or investigator’s choice of single agent chemotherapy or cetuximab. This was detailed in our press release, Merus Announces First Patient Dosed in LiGeR-HN2, a Phase 3 Trial Evaluating Petosemtamab in 2/3L r/m HNSCC - Merus ( July 24 , 2024). Merus provided updated interim clinical data on petosemtamab in 2L+ r/m HNSCC at the European Society for Medical Oncology Asia Congress , demonstrating a 36% response rate among 75 evaluable patients. The oral presentation was detailed in our press release, Merus’ Petosemtamab Monotherapy Interim Data Continues to Demonstrate Clinically Meaningful Activity in 2L+ r/m HNSCC ( Dec. 7 , 2024). In May 2024 , the FDA granted BTD for petosemtamab for the treatment of patients with recurrent or metastatic HNSCC whose disease has progressed following treatment with platinum based chemotherapy and an anti-programmed cell death receptor-1 (PD-1) or anti-programmed death ligand 1 (PD-L1) antibody. This designation was detailed in our press release, Petosemtamab granted Breakthrough Therapy Designation by the U.S. FDA ( May 13 , 2024). Merus believes a randomized registration trial in HNSCC with an overall response rate endpoint could potentially support accelerated approval and the overall survival results from the same study could potentially verify its clinical benefit to support regular approval. In the third quarter 2024, Merus announced the first patient was dosed in a phase 2 trial evaluating petosemtamab in combination with standard chemotherapy in 2L mCRC. This was detailed in our press release, Merus Announces First Patient Dosed in Phase 2 Trial of Petosemtamab in 2L CRC ( July 8, 2024 ). In the fourth quarter 2024, Merus announced the first patient was dosed in a phase 2 trial evaluating petosemtamab monotherapy in heavily pretreated (3L+) mCRC. This was detailed in our press release, Merus announces First Patient Dosed in Phase 2 Trial of Petosemtamab in 3L+ mCRC ( Dec. 16, 2024 ). In January 2025 , the first patient was dosed in a phase 2 trial evaluating petosemtamab in combination with standard chemotherapy in 1L mCRC. We expect to provide initial clinical data for petosemtamab in mCRC in 2H25. BIZENGRI® (zenocutuzumab-zbco: HER2 x HER3 Biclonics®)Approved by FDA for adults with pancreatic adenocarcinoma or non–small cell lung cancer (NSCLC) that are advanced unresectable or metastatic and harbor a neuregulin 1 (NRG1) gene fusion who have disease progression on or after prior systemic therapy In December 2024 , the FDA approved BIZENGRI® (zenocutuzumab-zbco), the first and only treatment indicated for adults with pancreatic adenocarcinoma or NSCLC that are advanced unresectable or metastatic and harbor a NRG1 gene fusion who have disease progression on or after prior systemic therapy. These indications are approved under accelerated approval based on overall response rate (ORR) and duration of response (DOR). Continued approval for these indications may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). BIZENGRI® has a Boxed WARNING for Embryo-Fetal Toxicity and warnings for infusion-related reactions (IRRs), hypersensitivity and anaphylactic reactions, interstitial lung disease (ILD)/pneumonitis, and left ventriculardysfunction.1 See Important Safety Information below. This was detailed in our press release, Merus Announces FDA Approval of BIZENGRI® (zenocutuzumab-zbco) for NRG1+ Pancreatic Adenocarcinoma and NRG1+ Non–Small Cell Lung Cancer (NSCLC) Based on Safety and Efficacy Data From the eNRGy Study ( December 4 , 2024). Merus has exclusively licensed to Partner Therapeutics the right to commercialize BIZENGRI® for the treatment of NRG1+ cancer in the U.S. This was detailed in our press release, Merus and Partner Therapeutics Announce License Agreement for the U.S. Commercialization of Zenocutuzumab in NRG1 Fusion-Positive Cancer ( December 2 , 2024). MCLA-129 (EGFR x c-MET Biclonics®): Solid Tumors Investigation of MCLA-129 is ongoing in METex14 NSCLC; phase 2 trial in combination with chemotherapy in 2L+ EGFR mutant (EGFRm) NSCLC enrolling In the third quarter 2024, Merus announced the first patients were dosed in the phase 2 trial evaluating MCLA-129 in combination with chemotherapy in 2L+ EGFRm NSCLC, with a cohort receiving MCLA-129 and paclitaxel and carboplatin, and another cohort receiving MCLA-129 and docetaxel. We remain interested in partnering MCLA-129 to sufficiently resource the development of MCLA-129 and the potential benefit it may have for patients. MCLA-129 is subject to a collaboration and license agreement with Betta Pharmaceuticals Co. Ltd. (Betta), which permits Betta to develop MCLA-129, and potentially commercialize exclusively in China, while Merus retains global rights outside of China. Collaborations Incyte CorporationSince 2017, Merus has been working with Incyte Corporation (Incyte) under a global collaboration and license agreement focused on the research, discovery and development of bispecific antibodies utilizing Merus’ proprietary Biclonics® technology platform. For each program under the collaboration, Merus receives reimbursement for research activities and is eligible to receive potential development, regulatory and commercial milestones and sales royalties for any products, if approved. Eli Lilly and CompanyIn January 2021, Merus and Eli Lilly and Company (Lilly) announced a research collaboration and exclusive license agreement to develop up to three CD3-engaging T-cell re-directing bispecific antibody therapies utilizing Merus’ Biclonics® platform and proprietary CD3 panel along with the scientific and rational drug design expertise of Lilly. The collaboration is progressing well with three programs advancing through preclinical development. Gilead SciencesIn March 2024, Merus and Gilead Sciences announced a collaboration to discover novel antibody based trispecific T-cell engagers using Merus’ patented Triclonics® platform. Under the terms of the agreement, Merus will lead early-stage research activities for two programs, with an option to pursue a third. Gilead will have the right to exclusively license programs developed under the collaboration after the completion of select research activities. If Gilead exercises its option to license any such program from the collaboration, Gilead will be responsible for additional research, development and commercialization activities for such program. Merus received an equity investment by Gilead of $25 million in Merus common shares and an upfront payment of $56 million. Ono PharmaceuticalIn 2018, the Company granted Ono Pharmaceutical Co., Ltd. (Ono) an exclusive, worldwide, royalty-bearing license, with the right to sublicense, research, test, make, use and market a limited number of bispecific antibody candidates based on Merus’ Biclonics® technology platform directed to an undisclosed target combination. During the third quarter of 2024, Merus achieved and received a milestone payment based on the filing of an Investigational New Drug (IND) application in Japan. BiohavenIn January 2025 , Merus and Biohaven announced a research collaboration and license agreement to co-develop three novel bispecific antibody drug conjugates (ADCs), leveraging Merus’ leading Biclonics® technology platform, and Biohaven’s next-generation ADC conjugation and payload platform technologies. Under the terms of the agreement, Biohaven is responsible for the preclinical ADC generation of three Merus bispecific antibodies under mutually agreed research plans. The agreement includes two Merus bispecific programs generated using the Biclonics® platform, and one program under preclinical research by Merus. Each program is subject to mutual agreement for advancement to further development, with the parties then sharing subsequent external development costs and commercialization, if advanced. Cash Runway, existing cash, cash equivalents and marketable securities expected to fund Merus’ operations into 2028 As of December 31, 2024, Merus had $724.0 million cash, cash equivalents and marketable securities. Based on the Company’s current operating plan, the existing cash, cash equivalents and marketable securities are expected to fund Merus’ operations into 2028. Full Year 2024 Financial Results Collaboration revenue for the year ended December 31, 2024 decreased $7.8 million as compared to the year ended December 31, 2023 , primarily as a result of decreases in Lilly revenue of $8.4 million and Incyte revenue of $6.4 million , offset by increases in Gilead revenue of $4.8 million , and Other revenue of $2.2 million . The decrease in Lilly revenue is primarily the result of decreases in upfront payment amortization of $4.8 million and reimbursement revenue of $3.6 million . The decrease in Incyte revenue is primarily the result of decreases in milestone revenue of $5.0 million and reimbursement revenue of $1.4 million . Gilead revenue increased due to the start of the collaboration agreement in 2024 which resulted in an increase in upfront payment amortization of $4.8 million . The increase in Other revenue is primarily the result of increases in milestone revenue of $2.1 million . Research and development expense for the year ended December 31, 2024 increased $84.7 million as compared to the year ended December 31, 2023 , primarily as a result of increases in external clinical services and drug manufacturing costs of $66.6 million , which primarily includes costs to advance our petosemtamab program and costs to fulfill our obligations under our collaboration agreements related to our programs, increases in personnel related expenses including share-based compensation of $11.8 million due to an increase in employee headcount and an increase in share price, consultancy expenses of $5.5 million , facilities expenses and other related expenses of $0.7 million , and consumables expenses of $0.2 million , offset by decreases in depreciation and amortization of $0.1 million . General and administrative expense for the year ended December 31, 2024 increased $23.0 million as compared to the year ended December 31, 2023 , primarily as a result of increases in personnel related expenses including share-based compensation of $12.6 million due to an increase in employee headcount and an increase in share price, consultancy expenses of $6.8 million , legal expenses of $1.8 million , facilities and depreciation expense of $1.2 million , and intellectual property and licenses expenses of $0.7 million . Other income, net consists of interest earned on our cash and cash equivalents held on account, accretion of investment earnings and net foreign exchange gains or losses on our foreign denominated cash, cash equivalents and marketable securities, and payables and receivables. Please see full Prescribing Information, including Boxed WARNING, at BIZENGRI.com/pi. Reference: 1. BIZENGRI. Prescribing information. Merus N.V. ; 2024. About Merus N.V. Merus is an oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as Multiclonics®. Multiclonics® are manufactured using industry standard processes and have been observed in preclinical and clinical studies to have several of the same features of conventional human monoclonal antibodies, such as long half-life and low immunogenicity. For additional information, please visit Merus’ website, and LinkedIn. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding the content and timing of clinical trials, data readouts and clinical, regulatory, strategy and development updates for our product candidates; our ongoing LiGeR-HN1, LiGeR-HN2 and phase 2 mCRC trials for petosemtamab, our planned update in the 1H 2025 on the phase 2 cohort of 1L r/m PD-L1+ HNSCC; our planned initial clinical data update on the phase 2 investigation of petosemtamab in mCRC; our belief that petosemtamab’s receipt of two BTDs by the FDA – previously as monotherapy in the 2L+ treatment of r/m HNSCC and very recently, based on updated clinical efficacy, durability and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC, indicates the potential for these treatment regimens to demonstrate substantial improvement over available therapies; the potential benefits of BTD for petosemtamab’s development, if any; our looking forward to sharing the updated clinical data, including durability, for petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC, for the full phase 2 cohort, in the first half of 2025; our expectation that the LiGeR-HN1 and LiGeR-HN2 studies will be substantially enrolled by year-end; our belief that a randomized registration trial in HNSCC with an overall response rate endpoint could potentially support accelerated approval and the overall survival results from the same study could potentially verify its clinical benefit to support regular approval; statements regarding the sufficiency of our cash, cash equivalents and marketable securities, and expectation that it will fund the Company into 2028; the continued investigation of MCLA-129 in monotherapy in Met ex14 NSCLC, and enrolling of patients in the investigation of MCLA-129 in combination with chemotherapy in 2L+ EGFRm NSCLC; our interest in partnering MCLA-129 to sufficiently resource the development of MCLA-129 and the potential benefit it may have for patients; the benefits of the license from Merus to PTx for the commercialization of Bizengri® in the US for NRG1+ cancer, collaborations between Incyte and Merus, Lilly and Merus, Gilead and Merus, Biohaven and Merus, and license agreement between Ono and Merus; and the potential of those licenses and collaborations for future value generation, including whether and when Merus will receive any future payments, including milestones or royalties, and the amounts of such payments; whether any programs under the collaboration will be successful; and our collaboration and license agreement with Betta, which permits Betta to develop MCLA-129 and potentially commercialize exclusively in China, while Merus retains full ex-China rights, including any future clinical development by Betta of MCLA-129. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our need for additional funding, which may not be available and which may require us to restrict our operations or require us to relinquish rights to our technologies or antibody candidates; potential delays in regulatory approval, which would impact our ability to commercialize our product candidates and affect our ability to generate revenue; the lengthy and expensive process of clinical drug development, which has an uncertain outcome; the unpredictable nature of our early stage development efforts for marketable drugs; potential delays in enrollment of patients, which could affect the receipt of necessary regulatory approvals; our reliance on third parties to conduct our clinical trials and the potential for those third parties to not perform satisfactorily; impacts of the volatility in the global economy, including global instability, including the ongoing conflicts in Europe and the Middle East; we may not identify suitable Biclonics® or bispecific antibody candidates under our collaborations or our collaborators may fail to perform adequately under our collaborations; our reliance on third parties to manufacture our product candidates, which may delay, prevent or impair our development and commercialization efforts; protection of our proprietary technology; our patents may be found invalid, unenforceable, circumvented by competitors and our patent applications may be found not to comply with the rules and regulations of patentability; we may fail to prevail in potential lawsuits for infringement of third-party intellectual property; and our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-K for the period ended December 31, 2024, filed with the Securities and Exchange Commission, or SEC, on February 27, 2025, and our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change, except as required under applicable law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. Bizengri®, Multiclonics®, Biclonics®, Triclonics® and ADClonics® are registered trademarks of Merus N.V. Source: Merus N.V.

UTRECHT, The Netherlands and CAMBRIDGE, Mass., Feb. 18, 2025 (GLOBE NEWSWIRE) -- Merus N.V. (Nasdaq: MRUS), a clinical-stage oncology company developing innovative, full-length multispecific antibodies and antibody drug conjugates (Biclonics®, Triclonics® and ADClonics®), for cancer, today announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy designation (BTD) to petosemtamab in combination with pembrolizumab for the first-line treatment of adult patients with recurrent or metastatic programmed death-ligand 1 (PD-L1) positive head and neck squamous cell carcinoma (r/m HNSCC) with combined positive score (CPS) ≥ 1. This second BTD designation follows the initial receipt of BTD and Fast Track designation for petosemtamab for the treatment of patients with r/m HNSCC whose disease has progressed following treatment with platinum-based chemotherapy and an anti-programmed cell death protein 1 (anti-PD-1) antibody announced in May 2024 and August 2023, respectively. BTD is supported by updated data from the ongoing phase 1/2 open-label, multicenter trial evaluating petosemtamab in combination with pembrolizumab in 1L HNSCC expressing PD-L1 (CPS≥1) (NCT03526835). Data for this cohort was initially presented at the American Society of Clinical Oncology® (ASCO®) Annual Meeting 2024, which demonstrated a 67% response rate among 24 evaluable patients. The oral presentation was detailed in our press release, Merus’ Petosemtamab in Combination with Pembrolizumab Interim Data Demonstrates Robust Response Rate and Favorable Safety Profile in 1L r/m HNSCC (May 28, 2024). In the BTD application, Merus provided updated interim clinical data on efficacy, durability and safety of the cohort of petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC. “We believe petosemtamab’s second BTD continues to validate its potential to become a new standard of care for patients with r/m HNSCC and underscores our commitment to accelerate development of petosemtamab for these patients,” said Fabian Zohren, M.D., Ph.D., Chief Medical Officer of Merus. “Importantly, this designation indicates the interim clinical data we shared with the FDA demonstrates petosemtamab’s potential for substantial improvement over available therapies in the 1L PD-L1+ setting.” BTD is intended to expedite the development and review of a medicine to treat a serious or life-threatening condition, where preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on clinically significant endpoints over available therapies. BTD allows for more intensive FDA guidance on an efficient drug development program, an organizational commitment involving senior managers, and experienced review staff, as appropriate, in a collaborative, cross-disciplinary review, and eligibility for rolling review and priority review. With this BTD, Merus plans to engage in these discussions with the FDA in an expedited manner as we move toward our goal of a potential Biologics License Application (BLA) submission. About LiGeR-HN1 LiGeR-HN1, a phase 3 trial, will evaluate the safety and efficacy of petosemtamab in combination with pembrolizumab, compared to pembrolizumab in 1L PD-L1+ r/m HNSCC patients. The trial is open to adult patients eligible to receive pembrolizumab as 1L monotherapy with tumors expressing PD-L1, CPS ≥1. The primary endpoints are overall response rate as assessed by BICR based on RECIST v1.1 and overall survival. Secondary endpoints are duration of response and progression free survival. Merus plans to enroll approximately 500 patients in the trial. About LiGeR-HN2 LiGeR-HN2, a phase 3 trial, will evaluate the safety and efficacy of petosemtamab compared to investigator’s choice of methotrexate, docetaxel, or cetuximab in 2/3L r/m HNSCC patients. The trial is open to adult patients that have progressed on or after anti-PD-1 therapy and platinum-containing therapy. The primary endpoints are overall response rate as assessed by BICR based on RECIST v1.1 and overall survival. Secondary endpoints are duration of response and progression free survival. Merus plans to enroll approximately 500 patients in the trial. About Head and Neck Cancer Head and neck squamous cell carcinoma (HNSCC) describes a group of cancers that develop in the squamous cells that line the mucosal surfaces of the mouth, throat, and larynx. These cancers begin when healthy cells change and grow in an unchecked manner, ultimately forming tumors. HNSCC is generally associated with tobacco consumption, alcohol use and/or HPV infections, depending on where they develop geographically. HNSCC is the sixth most common cancer worldwide and it is estimated that there were more than 930,000 new cases and over 465,000 deaths from HNSCC globally in 2020.1 The incidence of HNSCC continues to rise and is anticipated to increase by 30% to more than 1 million new cases annually by 2030.2 HNSCC is a serious and life-threatening disease with poor prognosis despite currently available standard of care therapies. 1 Sung et al. CA Cancer J Clin, 71:209-49, 2021; 2 Johnson, D.E., Burtness, B., Leemans, C.R. et al. Head and neck squamous cell carcinoma. Nat Rev Dis Primers 6(1):92, 2020 About Petosemtamab Petosemtamab, or MCLA-158, is a Biclonics® low-fucose human full-length IgG1 antibody targeting the epidermal growth factor receptor (EGFR) and the leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5). Petosemtamab is designed to exhibit three independent mechanisms of action including inhibition of EGFR-dependent signaling, LGR5 binding leading to EGFR internalization and degradation in cancer cells, and enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) activity. About Merus N.V. Merus is a clinical-stage oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as Multiclonics®. Multiclonics® are manufactured using industry standard processes and have been observed in preclinical and clinical studies to have several of the same features of conventional human monoclonal antibodies, such as long half-life and low immunogenicity. For additional information, please visit Merus’ website, Twitter and LinkedIn. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, the potential benefits of BTD for petosemtamab’s development for the first-line treatment of adult patients with recurrent or metastatic programmed death-ligand 1 (PD-L1) positive head and neck squamous cell carcinoma (R/M HNSCC) with CPS ≥ 1 ; Merus’ belief that petosemtamab’s second BTD continues to validate its potential to become a new standard of care for patients with r/m HNSCC; Merus’ commitment to accelerate development of petosemtamab for these patients; Merus’ belief that this designation indicates the interim clinical data shared with the FDA demonstrates petosemtamab’s potential for substantial improvement over available therapies in the 1L PD-L1+ setting; the potential for BTD to expedite the development and review of a medicine to treat a serious or life-threatening condition, where preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on clinically significant endpoints over available therapies; the potential of BTD to allow for more intensive FDA guidance on an efficient drug development program, an organizational commitment involving senior managers, and experienced review staff, as appropriate, in a collaborative, cross-disciplinary review, and eligibility for rolling review and priority review; and Merus’ plans to engage in these discussions with the FDA in an expedited manner as we move toward our goal of a potential Biologics License Application (BLA) submission. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our need for additional funding, which may not be available and which may require us to restrict our operations or require us to relinquish rights to our technologies or antibody candidates; potential delays in regulatory approval, which would impact our ability to commercialize our product candidates and affect our ability to generate revenue; the lengthy and expensive process of clinical drug development, which has an uncertain outcome; the unpredictable nature of our early stage development efforts for marketable drugs; potential delays in enrollment of patients, which could affect the receipt of necessary regulatory approvals; our reliance on third parties to conduct our clinical trials and the potential for those third parties to not perform satisfactorily; impacts of the volatility in the global economy, including global instability, including the ongoing conflicts in Europe and the Middle East; we may not identify suitable Biclonics® or bispecific antibody candidates under our collaborations or our collaborators may fail to perform adequately under our collaborations; our reliance on third parties to manufacture our product candidates, which may delay, prevent or impair our development and commercialization efforts; protection of our proprietary technology; our patents may be found invalid, unenforceable, circumvented by competitors and our patent applications may be found not to comply with the rules and regulations of patentability; we may fail to prevail in potential lawsuits for infringement of third-party intellectual property; and our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-Q for the period ended September 30, 2024, filed with the Securities and Exchange Commission, or SEC, on October 31, 2024, and our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change, except as required under applicable law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. Multiclonics®, Biclonics®, Triclonics® and ADClonics® are registered trademarks of Merus N.V. Source: Merus N.V.