Genmab's petosemtamab cuts death risk by 50% in Phase 3 HNSCC trial
Genmab has reported positive topline results from its Phase 3 LiGeR-HN1 trial, in which the investigational bispecific antibody petosemtamab combined with Merck's checkpoint inhibitor pembrolizumab demonstrated a statistically significant and clinically meaningful improvement in both overall survival and objective response rate versus pembrolizumab alone in patients with first-line PD-L1-positive recurrent or metastatic head and neck squamous cell carcinoma (HNSCC).
The combination reduced the risk of death by 50% compared with pembrolizumab monotherapy, producing a hazard ratio of 0.50 (95% CI, 0.37–0.67; p less than 0.0001). The objective response rate odds ratio was 3.17 (95% CI, 2.06–4.89; p less than 0.0001). Crucially, the benefit was observed regardless of human papillomavirus status, a distinction that broadens the potential eligible patient population. The independent data monitoring committee assessed the first interim analysis and the trial met both co-primary endpoints.
The drug and the data
Petosemtamab is a low-fucose IgG1 bispecific antibody that targets two distinct receptors: the epidermal growth factor receptor (EGFR) and LGR5, a marker expressed on cancer stem-like cells associated with treatment resistance and disease recurrence. By simultaneously engaging both targets, the molecule is designed to block EGFR signalling, trigger receptor internalisation and degrade EGFR in co-expressing tumour cells, and recruit natural killer cells through antibody-dependent cell-mediated cytotoxicity. The combination of these mechanisms is what Genmab positions as a differentiated, chemotherapy-free approach.
The safety profile in the combination arm was reported as generally well tolerated and consistent with the previously known profiles of each agent individually. No new safety signals were identified, though full safety data will follow at a future medical conference.
Everett Vokes, chair of the Department of Medicine at the University of Chicago Medicine and a named investigator, described LiGeR-HN1 as "the first positive Phase 3 study in this patient population in several years" and said the results "could reshape the treatment of this devastating disease by establishing a new therapeutic option."
Regulatory path and competitive context
Genmab said it plans to engage regulatory authorities globally, with full data to be presented at a forthcoming scientific meeting. The company has not stated a filing timeline, but petosemtamab already holds FDA Breakthrough Therapy Designation for first-line recurrent or metastatic PD-L1-positive HNSCC in combination with pembrolizumab, which may expedite the review process.
HNSCC is the seventh most common cancer worldwide, and recurrent or metastatic disease carries a median overall survival of approximately 10 to 12 months with current treatments. Pembrolizumab monotherapy, approved in this setting since 2019, has been the standard of care for PD-L1-positive patients. The LiGeR-HN1 data directly challenges that standard by showing the combination markedly improves upon pembrolizumab alone without adding chemotherapy.
The competitive landscape for first-line HNSCC has seen limited successful late-stage readouts in recent years, making a positive Phase 3 dataset in this indication a relatively rare event. A number of EGFR-targeting strategies have previously failed to deliver Phase 3 wins in head and neck cancer, which lends additional weight to petosemtamab's dual-mechanism design and its LGR5 targeting component.
Beyond HNSCC, Genmab is evaluating petosemtamab in second- and third-line HNSCC through the LiGeR-HN2 trial, and in metastatic colorectal cancer via two further Phase 3 studies. Investors will be focused on the timeline to regulatory submission and whether the benefit seen at this first interim analysis is sustained in the final dataset.