Merus Announces Petosemtamab in Previously Treated Head and Neck Squamous Cell Carcinoma Abstract Selected for Plenary Session Oral Presentation at the AACR Annual Meeting 2023

– Plenary session oral presentation: Monday, April 17, 2023, 10:15 a.m.-12:15 p.m. ET

– Poster presentation on petosemtamab in advanced gastric/esophageal adenocarcinoma: Monday, April 17, 2023, 1:30-5:30 p.m. ET

– Investor call on Monday, April 17, 2023 at 6:30 p.m. ET

UTRECHT, The Netherlands and CAMBRIDGE, Mass., March 14, 2023 (GLOBE NEWSWIRE) -- N.V. (Nasdaq: MRUS) (Merus, the Company, we, or our), a clinical-stage oncology company developing innovative, full-length multispecific antibodies (Biclonics^® and Triclonics^®), today announced the selection of an abstract for a plenary session oral presentation that will highlight interim clinical data on the bispecific antibody petosemtamab in previously treated head and neck squamous cell carcinoma (HNSCC) along with the selection of a second abstract on petosemtamab in advanced gastric/esophageal adenocarcinoma for poster presentation at the American Association for Cancer Research (AACR) Annual Meeting 2023 taking place in Orlando, Florida April 14-19, 2023.

Petosemtamab is in clinical development in the expansion part of a phase 1 open-label, multicenter trial in advanced solid tumors, including previously treated HNSCC.

Presentation Details:

Petosemtamab (MCLA-158)

Title: Clinical activity of MCLA-158 (petosemtamab), an IgG1 bispecific antibody targeting EGFR and LGR5, in advanced head and neck squamous cell cancer (HNSCC)

Session Category: Clinical Trials Plenary Session

Session: Promising Novel Antitumor Strategies in Early Phase Clinical Trials

Date: Monday, April 17, 2023

Time: 10:15 a.m.-12:15 p.m. ET

Presentation #: CT012

Title: MCLA-158 (petosemtamab), an IgG1 bispecific antibody targeting EGFR and LGR5, in advanced gastric/esophageal adenocarcinoma (GEA)

Session: Phase II Clinical Trials 1

Date: Monday, April 17, 2023

Time: 1:30-5:30 p.m. ET

Poster #: 18

Abstract #: CT156

The abstracts will be available on the AACR at the start of the conference on Friday, April 14, 2023 at 1:00 p.m. ET. The presentations will be available on the Merus at the start of each session.

Company Conference Call and Webcast Information

Merus will hold a conference call and webcast for investors on April 17, 2023 at 6:30 p.m. ET. A replay will be available after the completion of the call in the section of our website for a limited time.

Date & Time: April 17, 2023 at 6:30 p.m. ET

Webcast link:

Dial-in: Toll Free: 1 (800) 715-9871 / International: 1 (646) 307-19631

Conference ID: 4032258

About MCLA-158

MCLA-158, or petosemtamab, is an ADCC-enhanced human IgG1 Biclonics^® designed to bind to cancer stem cells (CSCs) expressing leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) and epidermal growth factor receptor (EGFR). In preclinical models, MCLA-158 binding triggers EGFR degradation in LGR5+ CSCs and is designed to have two different mechanisms of action. The first entails blocking of growth and survival pathways in cancer initiating cells. The second exploits the recruitment and enhancement of immune effector cells to directly kill cancer initiating cells that persist in solid tumors and can cause relapse and metastasis.

About Merus N.V.

is a clinical-stage oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as . 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 .

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 petosemtamab, future clinical trial results or interim data, clinical activity and safety profile of petosemtamab, mechanisms of action and planned presentation and investor call. 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 Biclonics^®, Triclonics^® and multispecific 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 COVID-19 pandemic; 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 year ended December 31, 2022 filed with the Securities and Exchange Commission, or SEC, on February 28, 2023, 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.

Biclonics^®, Triclonics^® and Multiclonics^® are registered trademarks of Merus N.V.