ASCO: Early Merus bispecific cancer data meets investor expectations

Merus is preparing to initiate a phase 3 clinical trial for its bispecific antibody, petosemtamab, targeting second-line treatment of head and neck cancer within the year. This development follows a promising data presentation at the 2024 American Society of Clinical Oncology, which showcased significant clinical responses among patients receiving the therapy.

Merus' latest findings, focused on petosemtamab combined with Keytruda, a first-line treatment for recurrent or metastatic head and neck squamous cell carcinoma, reported a 60% response rate among 10 evaluable patients in a phase 2 trial. This data set, although limited, included one complete response, two partial responses, and three unconfirmed partial responses. The trial had, by November 6, 2023, enrolled 26 patients, with 24 continuing their treatment.

This level of efficacy met investor expectations and was positively received by analysts, including those from William Blair, who expressed encouragement upon seeing the complete response among the patients. Merus' CEO, Bill Lundberg, indicated that further updates could show an even higher response rate when the company releases more mature data.

Safety data from the trial were also reassuring. No significant overlapping toxicities were noted in patients undergoing the petosemtamab-Keytruda treatment. While treatment-emergent adverse events were common, they were mostly mild (grade 1 or 2). Infusion-related reactions occurred in 27% of patients, with only 3.8% experiencing more severe grade 3 reactions, which resolved after the first infusion.

Lundberg expressed confidence in the combination's safety and efficacy, emphasizing the low incidence of severe adverse events and infusion reactions. He highlighted petosemtamab's potential to offer a best-in-class safety profile for head and neck cancer treatments.

In addition to the ongoing head and neck cancer studies, Merus is also planning to conduct a colorectal cancer study within the year. This expansion of their clinical pipeline is bolstered by a $150 million public offering secured earlier in 2023, which Lundberg discussed at the European Society for Medical Oncology conference in Madrid.

Beyond petosemtamab, Merus is advancing its bispecific antibody, zenocutuzumab, which has been submitted to the FDA for priority review. If approved, zenocutuzumab, branded as Zeno, will become the first targeted therapy for patients with NRG1+ non-small cell lung cancer and pancreatic cancer.

The recent positive reception of petosemtamab data stands in contrast to Merus' previous year's challenges. At the European Society for Medical Oncology's Asia Congress 2023, the company's stock dipped following an interim update for their bispecific therapy, MCLA-129, which reported three deaths in the lung cancer trial segment.

In summary, Merus is advancing its bispecific antibody programs with significant clinical progress and a robust pipeline. The promising phase 2 trial results for petosemtamab, alongside a strong safety profile, have set the stage for a pivotal phase 3 trial. Meanwhile, the FDA review of zenocutuzumab could potentially provide new targeted therapy options for specific cancer patients.