Genmab intends to acquire all the shares of Merus and its late-stage, first-in-class cancer drug petosemtamab for approximately $8 billion. Petosemtamab, with pembrolizumab, is in Phase III development for head and neck squamous cell (HNSCC) and has two breakthrough therapy designations. The drug is a human, common light chain, IgG1 bispecific antibody targeting EGFR and LGR5 and developed on Merus’ proprietary Multiclonics platform.
Genmab expects this acquisition will help shift the company to a wholly owned model, expanding and diversifying its revenue and driving sustained growth into the next decade. In a press release, Genmab said it sees petosemtamab, Merus’ lead asset, as a compelling strategic fit with Genmab’s portfolio that aligns with Genmab’s expertise in antibody therapy development and commercialization in oncology. Following the closing of the transaction, Genmab will have four proprietary programs expected to drive multiple new drug launches by 2027.
The world market for head and neck cancer was estimated at approximately $2.27 billion in 2024, and projected to reach $6.25 billion by 2033. The monoclonal antibody cetuximab (an EGFR inhibitor) is the most established approved therapy for HNSCC. Other strategies under investigation include PI3K/AKT/mTOR pathway inhibitors and HER2-targeted therapies for salivary gland cancers. Bicara Therapeutics has presented positive Phase I/Ib data for its ficerafusp alfa in first-line HNSCC.
“The proposed acquisition of Merus clearly aligns with our long-term strategy. It has the potential to significantly accelerate our evolution into a global biotechnology leader by providing durable growth for the company well into the next decade,” said Jan van de Winkel, PhD, president and chief executive officer of Genmab. “Petosemtamab has the potential to be a transformational therapy for patients living with head and neck cancer. With our proven track record of success, both in clinical development and in commercialization, we are confident that we will be able to unlock the promise of petosemtamab.”
Head and neck cancer is genetically complex and difficult to treat. It is the sixth most frequently occurring cancer, with tobacco, alcohol and human papillomavirus (HPV) being major risk factors. Epigenetic data suggests it is remarkably heterogeneous, and treatment has been challenging leading to a lack of significant improvement in survival and quality of life in patients. Over half of patients experience locoregional recurrence or distal metastasis despite the use of multiple traditional therapeutic strategies and immunotherapy. In addition, resistance to chemotherapy, radiotherapy and some targeted therapies is common.
Compelling Phase II data was presented on the drug at the American Society for Clinical Oncology (ASCO) 2025 Annual Meeting showing both an overall response rate and median progression free survival that were substantially higher than standard of care.
Merus is currently running two Phase III trials in first- and second/third- line head and neck cancer, with topline interim readout of one or both trials anticipated in 2026. Genmab anticipates the potential for the initial launch of petosemtamab in 2027 and intends to broaden and accelerate petosemtamab’s development with potential expansion into earlier lines of therapy. Following approval, Genmab believes that petosemtamab will generate at least one-billion-dollar annual sales potential by 2029, with multi-billion-dollar annual revenue potential thereafter.
Merus’ Multiclonics therapeutics are produced from their proprietary technology platforms, which can generate a diverse array of antibody binding domains against “virtually any target.” Multiple binding domains can be combined to produce novel bispecific and trispecific antibodies.
