Genmab’s Petosemtamab–Keytruda Combination Improves Survival in Phase 3 Head and Neck Cancer Trial

Genmab’s investigational antibody petosemtamab has improved overall survival when added to Keytruda in a Phase 3 head and neck cancer trial. The findings announced on October 28 strengthen the clinical case for a candidate acquired through Genmab’s $8 billion purchase of Merus in 2025. (Fierce Biotech’s coverage of the petosemtamab Phase 3 results)

At the first interim analysis, LiGeR-HN1 met both primary endpoints: overall survival and objective response rate. The overall-survival hazard ratio was 0.50 (95% CI, 0.37–0.67), representing a 50% reduction in the relative hazard of death during follow-up. This does not mean that every patient can expect to live twice as long.

The randomized, open-label trial addresses whether adding petosemtamab improves outcomes over Keytruda alone. It does not directly establish superiority over chemotherapy-containing first-line regimens. That distinction matters when considering where this chemotherapy-free combination might eventually fit into treatment.

Petosemtamab brings several mechanisms into one antibody. It blocks EGFR signaling and, in tumor cells expressing both EGFR and LGR5, promotes EGFR internalization and degradation through LGR5. Its active Fc region also enables immune cells, including natural killer cells, to attack antibody-coated tumor cells through antibody-dependent cellular cytotoxicity, or ADCC.

Important details remain to be assessed. Genmab reported no new safety signals, but its topline announcement did not provide detailed adverse-event rates or median overall-survival figures. The company plans to discuss the findings with regulators and submit the full results for presentation at a future medical meeting. Petosemtamab remains investigational; this is a positive development milestone rather than an approval or an expansion of an existing label. (Genmab’s official announcement of the LiGeR-HN1 results)

The patient context gives these findings particular weight. Head and neck cancer and its treatment can interfere with eating, swallowing, speaking and breathing. (National Cancer Institute’s overview of head and neck cancers) Difficulty eating can contribute to malnutrition and weight loss, adding to the burden of treatment. Cancer cachexia can further complicate care, although it is a distinct syndrome involving metabolic and inflammatory changes, rather than simply a consequence of inadequate food intake. (National Cancer Institute’s explanation of cancer cachexia)

For me, this close connection between the disease and everyday function makes progress in head and neck cancer especially meaningful. These difficulties are not unique to this cancer, but they can affect some of the most basic parts of daily life. I welcome Genmab’s results and the attention they bring to this patient population. Alongside the survival benefit, I hope the fuller data will clarify tolerability and patients’ experiences during treatment. Preserving the ability to share a meal or hold a conversation is an outcome worth keeping in view, even though improvement in those functions has not yet been demonstrated by this topline announcement.

For another approach to cancer immunotherapy, you can read my previous analysis of Astellas and Audax’s tumor-focused IL-12 candidate DAX-044.