Genmab announced that its experimental antibody petosemtamab, combined with Merck's Keytruda, reduced death risk by 50% in a Phase 3 head and neck cancer trial. Following the readout, Genmab's U.S. shares jumped 28% and its market capitalization surpassed $35 billion. Acquired via an $8 billion deal for Merus, petosemtamab is key to Genmab's strategy to offset upcoming Darzalex royalty losses and reach $10 billion in annual revenue.
Phase 3 trial results for petosemtamab
- ▪Genmab has not disclosed median overall survival figures for either treatment arm in the petosemtamab Phase 3 head and neck cancer study
- ▪The combination regimen of petosemtamab and Keytruda met dual main objectives on overall response rates and survival in first-line head and neck squamous cell carcinoma
- ▪Genmab's experimental antibody petosemtamab combined with Merck's Keytruda reduced the risk of death by half in PD-L1-positive head and neck cancer
- ▪Genmab's Phase 3 trial of petosemtamab combined with Keytruda evaluated patients with recurrent or metastatic head and neck cancer who had not yet received prior systemic treatment for that stage
Stock market reaction to trial results
- ▪Genmab's market valuation increased by more than $7 billion following the petosemtamab trial results, pushing its total market value past $35 billion
- ▪U.S.-traded shares of Genmab rose 28% on October 28, 2026, following the announcement of petosemtamab's Phase 3 trial results
Financial outlook and revenue drivers
- ▪Genmab generated approximately $3.7 billion in revenue in 2025, heavily driven by royalties from Johnson & Johnson's sales of Darzalex
- ▪Genmab projected that petosemtamab could reach blockbuster status by 2029 if late-stage study results replicated Phase 2 findings
- ▪William Blair analyst Matt Phipps noted that positive late-stage trial readouts for petosemtamab, Epkinly and rinatabart sesutecan position Genmab to surpass $10 billion in total annual revenue
- ▪Genmab is relying on new drug launches to offset the impending loss of patent exclusivity and royalties from multiple myeloma drug Darzalex
Other clinical trials for petosemtamab
- ▪Petosemtamab is currently undergoing evaluation in a Phase 3 trial as a treatment for colorectal cancer
- ▪Genmab is testing petosemtamab in separate Phase 3 clinical trials for second-line and third-line recurrent head and neck cancer
Genmab's acquisitions of biotech companies
- ▪Genmab acquired the antibody-drug conjugate rinatabart sesutecan through a 2024 acquisition of biotechnology startup ProfoundBio
- ▪Genmab acquired the bispecific antibody petosemtamab through an $8 billion acquisition of Dutch biotechnology company Merus
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