Petosemtamab Phase 3 Results: Genmab Head and Neck Cancer Drug Cuts Death Risk 50% With Keytruda
Petosemtamab Phase 3 results released on Wednesday, Oct. 28, 2026, show that adding Genmab’s investigational bispecific antibody to Merck’s Keytruda (pembrolizumab) cut the risk of death by 50% compared with Keytruda alone in people with newly diagnosed recurrent or metastatic head and neck cancer whose tumors express PD-L1. Genmab (Nasdaq: GMAB) said the LiGeR-HN1 trial met both of its primary goals—overall survival and tumor response—at a first interim analysis.
The topline results are company-reported and have not yet been presented at a medical meeting or published in a peer-reviewed journal. Below is what was announced, what the science means in plain language, who could benefit, and what comes next.
Key Takeaways
- What happened: Genmab said the Phase 3 LiGeR-HN1 trial of petosemtamab plus pembrolizumab met its co-primary endpoints of overall survival (OS) and objective response rate (ORR) at a first interim analysis.
- Headline number: Overall survival hazard ratio of 0.50 (95% CI, 0.37–0.67; p<0.0001), which the company describes as a 50% reduction in the risk of death.
- Who was studied: Adults receiving first-line treatment for recurrent or metastatic, PD-L1-positive head and neck squamous cell carcinoma (HNSCC).
- Safety: Genmab said the combination was generally well tolerated, with no new safety signals.
- Next steps: Full data will be submitted to a future medical meeting; Genmab plans to engage with regulators worldwide.
What Genmab Announced: The LiGeR-HN1 Phase 3 Results
Verified facts from the trial disclosure
According to Genmab’s Oct. 28 announcement, LiGeR-HN1 (NCT06525220) is a randomized, open-label, global Phase 3 study. Patients were assigned 1:1 to receive either petosemtamab plus pembrolizumab or pembrolizumab alone. The co-primary endpoints are overall survival and objective response rate; key secondary endpoints include progression-free survival, duration of response, time to response, safety and patient-reported outcomes.
An independent data monitoring committee reviewed the first interim analysis. The company reported:
| Endpoint | Result reported by Genmab |
|---|---|
| Overall survival | Hazard ratio 0.50 (95% CI, 0.37–0.67); p<0.0001 |
| Objective response | Odds ratio 3.17 (95% CI, 2.06–4.89); p<0.0001 |
| HPV status | Benefit observed regardless of HPV status (per company) |
| Safety | Consistent with known profiles of each drug; no new safety signals (per company) |
The announcement did not disclose the number of patients enrolled, median survival in each arm, or the actual response rates in each group. Those details are expected when full results are presented.
Company statements
Genmab CEO Jan van de Winkel, Ph.D., called the results “a defining milestone for Genmab.” Everett E. Vokes, M.D., of University of Chicago Medicine, who was quoted in the company’s release, said the trial has “the potential to redefine care.” These are statements issued through the company’s announcement, not independent peer review.
The Science in Plain Language
Petosemtamab is a bispecific antibody—a single engineered protein designed to grab two different targets at once. According to Genmab, it binds to:
- EGFR (epidermal growth factor receptor), a growth signal receptor found at high levels on many head and neck cancers; and
- LGR5, a protein associated with cancer cells that behave like stem cells and may help tumors regrow.
The company describes three ways the drug is designed to work: blocking EGFR growth signaling, triggering the breakdown of EGFR in cells that carry both targets, and recruiting the immune system’s natural killer cells to destroy tumor cells (a process called antibody-dependent cell-mediated cytotoxicity). Its antibody backbone is “low-fucose,” a modification intended to strengthen that immune-cell recruitment.
Pembrolizumab (Keytruda) works differently: it is a checkpoint inhibitor that releases a brake (PD-1) on T cells so they can attack cancer. The trial tested whether attacking the tumor from both directions improves outcomes compared with Keytruda alone, which is an established first-line option for PD-L1-positive recurrent or metastatic HNSCC.
How to read a hazard ratio of 0.50
A hazard ratio compares the rate of an event—here, death—between two groups over the study period. A ratio of 0.50 means that, at any given time during follow-up, patients in the combination arm were dying at about half the rate of those in the Keytruda-alone arm. It does not mean that half as many patients died overall, and it does not by itself show how many extra months of life patients gained. The 95% confidence interval (0.37–0.67) indicates the range in which the true effect most plausibly lies.
Who Could Benefit
Head and neck squamous cell carcinoma arises in the lining of the mouth, throat and voice box. When it returns after initial treatment or spreads to other parts of the body, it is generally considered incurable, and treatment aims to extend life and control symptoms. If the results hold up in full review and the drug is approved, the combination could become a new first-line option for patients whose tumors test positive for PD-L1. Genmab reported benefit regardless of HPV status—relevant because HPV-linked throat cancers can behave differently from tobacco- and alcohol-linked cancers.
The Evidence So Far
Earlier Phase 2 data
The Phase 3 result follows earlier signals from smaller studies run by Merus, the Dutch biotech that originally developed petosemtamab. At the 2024 ASCO Annual Meeting, Merus reported a 67% response rate (16 of 24 evaluable patients) for the combination in first-line patients. In that early cohort, infusion-related reactions occurred in 38% of patients (7% Grade 3), mostly at the first infusion. Small, single-arm studies like that one can overstate benefit, which is why the randomized Phase 3 comparison matters.
Regulatory status
Petosemtamab already holds two FDA Breakthrough Therapy Designations: one for first-line PD-L1-positive recurrent or metastatic HNSCC with pembrolizumab, and one for HNSCC that has progressed after platinum chemotherapy and anti-PD-1 therapy, according to Genmab. The designation is meant to speed development and review; it is not an approval.
Corporate background
Genmab agreed to acquire Merus for about $8 billion ($97 per share) in late September 2025, a deal built largely around petosemtamab, pharmaphorum reported at the time. Merus had previously said it hoped for a 2027 launch.
Important Caveats
- Interim, topline data: These are early results from a pre-planned interim analysis, announced by press release. Effect sizes can shift with longer follow-up.
- Open-label design: Patients and doctors knew which treatment was given. That has less influence on overall survival than on response assessments.
- Missing details: Enrollment size, median survival, absolute response rates and full side-effect tables have not been released.
- Not yet peer reviewed: Independent experts will be able to evaluate the data only once it is presented or published.
What Comes Next
- Medical meeting presentation: Genmab said full results will be submitted to an upcoming medical congress (no date announced).
- Regulatory filings: The company said it plans to engage global health authorities.
- Second Phase 3 trial: LiGeR-HN2 (NCT06496178), testing petosemtamab in previously treated head and neck cancer, is ongoing.
- Colorectal cancer: Phase 3 studies LiGeR-CRC1 and LiGeR-CRC2 are evaluating the drug in previously treated metastatic colorectal cancer.
Patients with head and neck cancer who are interested in this research should talk with their oncology team about whether clinical trials or current standard treatments are appropriate for them.
Related Coverage on Vanderbiltreport.com
- Admilparant Phase 3 Results: BMS IPF Drug Meets Primary Goal at 60 mg, Misses at 120 mg
- Vaxcyte VAX-31 Phase 3 Results: 31-Valent Pneumococcal Vaccine Meets All Primary Endpoints
- FDA Approves Hibsago: A New Chronic Hepatitis B Treatment Aims for a “Functional Cure”
- FDA Panel Backs GRAIL’s Galleri Multi-Cancer Early Detection Test
Sources
- Genmab A/S — LiGeR-HN1 topline results announcement (Oct. 28, 2026)
- ClinicalTrials.gov — LiGeR-HN1 (NCT06525220)
- ClinicalTrials.gov — LiGeR-HN2 (NCT06496178)
- Merus — Phase 2 interim data, ASCO 2024 (via BioSpace)
- pharmaphorum — Genmab agrees $8bn takeover of Merus (Sept. 2025)
This article is for general information only and is not medical advice. It does not constitute an investment recommendation regarding any company mentioned.
Publisher Disclaimer: Vanderbiltreport.com publishes news and information for general informational and educational purposes. Information is compiled from sources believed to be reliable, but Vanderbiltreport.com does not guarantee the accuracy, completeness, or timeliness of all information presented. Readers should independently verify information and conduct their own research before making financial, investment, business, or other decisions.
