ASCO: Early peek at Merus' bispecific cancer data lives up to investors' expectations

Analysts have hailed Merus’ latest data drop in head and neck cancer as meeting investors’ expectations for the bispecific antibody.

The slim slice of efficacy data, which Merus presented at the 2024 American Society of Clinical Oncology, comes from just 10 evaluable patients from a phase 2 trial. But the dual American and Dutch biotech has still been able to demonstrate a 60% response rate.

The study is assessing petosemtamab, a bispecific antibody for EGFR x LGR5 cancers, in combination with Keytruda as a first-line treatment for recurrent/metastatic head and neck squamous cell carcinoma. By the Nov. 6, 2023, cutoff, 26 patients had been treated, with 24 continuing with their therapy.

Only 10 were evaluable for response at this point, with six of these individuals seeing a tumor response, Merus explained in its May 23 release. They included one confirmed complete response, two confirmed partial responses, and three unconfirmed partial responses.

In a note following the news, analysts at William Blair said they were “highly encouraged to see this level of efficacy, including a complete responder.”

“Overall, this does appear to meet the bar set by many investors going into the release of a 60% response rate,” they added.

Merus’ CEO Bill Lundberg, M.D., hinted at a further improved response rate that would be revealed when the biotech shares a “more mature clinical update from a later cutoff date” on a May 28 conference call.

When assessing all 26 patients who received the petosemtamab-Keytruda regimen, Merus said “no significant overlapping toxicities were observed.” While treatment-emergent adverse events were reported in all patients, “most” were grade 1 or 2 in severity.

Infusion-related reactions of various levels of severity were reported in 27% of patients, of which 3.8% were grade 3, and these all occurred during the first infusion before resolving, the company said.

“We believe petosemtamab continues to demonstrate potential best-in-class safety and efficacy in head and neck cancer,” Lundberg said. “We are encouraged with the well-tolerated safety profile of the combination of petosemtamab and pembrolizumab, particularly with a low rate of grade 3 or greater adverse events, and a low rate of infusion-related reactions observed.”

The biotech has already been laying out plans to kick off a phase 3 trial of the antibody in second-line head and neck cancer this year. A colorectal cancer study is also penciled in for this year.

Talking to Fierce Biotech at the European Society for Medical Oncology conference in Madrid in October last year, Lundberg said the development of petosemtamab would be fueled by a $150 million public offering secured earlier in 2023.

Leading Merus’ pipeline is the bispecific antibody zenocutuzumab, which has been submitted to the FDA for priority approval. Should the drug, which will be branded Zeno, get the green light from the regulator, it will be the first and only targeted therapy for patients with NRG1+ non-small cell lung cancer SCLC and pancreatic cancer, the company has said.

Yesterday’s sneak peek at the petosemtamab data has so far received a warmer response than a similar cancer conference readout at the end of last year. For the European Society for Medical Oncology's Asia Congress 2023, Merus' shares dipped after an interim update for a bispecific therapy called MCLA-129 revealed three deaths in the lung cancer portion of an ongoing trial.