Genmab Reports 50% Death-Risk Cut For Petosemtamab Combo, Validating Its $8 Billion Merus Bet

Genmab said the first interim analysis of its phase 3 LiGeR-HN1 trial showed that adding petosemtamab to Merck & Co.'s Keytruda cut the risk of death by 50% compared with Keytruda alone in patients with PD-L1-positive recurrent or metastatic head and neck squamous cell carcinoma.

The company said the study met both primary endpoints, delivering statistically significant improvements in overall survival and objective response rate. That matters beyond a single readout: petosemtamab came to Genmab through its $8 billion acquisition of Merus last year, so the result is an early test of whether that deal can produce a first-in-class oncology product with major commercial weight.

The Data

Genmab reported an overall survival hazard ratio of 0.50 for the combination and said the odds of achieving an objective response were 3.17 times higher than with Keytruda alone. The company also said the combination's safety profile was consistent with previous findings for the individual drugs, with no new safety signals identified.

Petosemtamab is an immunoglobulin G1 bispecific antibody that binds epidermal growth factor receptor and leucine-rich repeat-containing G-protein-coupled receptor 5, which the source describes as a novel oncology target. The phase 3 result followed earlier data disclosed this week from a midstage trial in recurrent or metastatic HNSCC, where petosemtamab plus Keytruda produced an objective response rate of 63% among 43 evaluable patients and median progression-free survival of nine months.

The Commercial Picture

The immediate signal is that Genmab now has late-stage evidence for a program that William Blair analysts projected could reach $4 billion in peak sales in HNSCC alone. A 50% reduction in the risk of death against Keytruda alone sets a high bar for relevance in a difficult-to-treat cancer and gives Genmab a stronger footing as it prepares regulatory discussions.

Genmab said it plans to discuss the results with global regulators and submit the full dataset for presentation at a future medical meeting. The company is also evaluating petosemtamab in second- and third-line recurrent or metastatic HNSCC, as well as colorectal cancer, across three additional phase 3 studies, which means the current win could become the lead edge of a broader franchise rather than a one-indication asset.