- 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.

¹Sung et al. CA Cancer J Clin, 71:209-49, 2021; ²Johnson, 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.

Investor and Media Inquiries:

Sherri Spear
Merus N.V.
SVP Investor Relations and Strategic Communications
617-821-3246
s.spear@merus.nl

Kathleen Farren
Merus N.V.
Director Investor Relations and Corporate Communications
617-230-4165
k.farren@merus.nl

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