Merus N.V.'s novel bispecific antibody petosemtamab has received its second Breakthrough Therapy designation (BTD) from the U.S. Food and Drug Administration, marking a significant advancement in head and neck cancer treatment. The designation specifically covers the combination of petosemtamab with pembrolizumab for first-line treatment of adult patients with PD-L1 positive recurrent or metastatic head and neck squamous cell carcinoma (r/m HNSCC).
The FDA's decision was supported by compelling interim data from an ongoing phase 1/2 trial. Among 24 evaluable patients, the combination therapy demonstrated a remarkable 67% response rate, suggesting substantial improvement over existing treatment options for PD-L1 positive HNSCC patients.
"We believe petosemtamab's second BTD continues to validate its potential to become a new standard of care for patients with r/m HNSCC," stated Dr. Fabian Zohren, Chief Medical Officer of Merus. "This designation indicates the interim clinical data we shared with the FDA demonstrates petosemtamab's potential for substantial improvement over available therapies in the 1L PD-L1+ setting."
Mechanism of Action and Drug Design
Petosemtamab (MCLA-158) is engineered as a Biclonics® low-fucose human full-length IgG1 antibody. It targets two key proteins: the epidermal growth factor receptor (EGFR) and the leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5). The drug operates through three distinct mechanisms, including EGFR signaling inhibition, enhanced antibody-dependent cell-mediated activities, and LGR5-mediated EGFR degradation in cancer cells.
Advancing Clinical Development
Two pivotal phase 3 trials are currently underway:
LiGeR-HN1 is evaluating petosemtamab plus pembrolizumab against pembrolizumab alone in first-line PD-L1 positive r/m HNSCC patients. The trial aims to enroll approximately 500 patients, with overall response rate and overall survival as primary endpoints.
LiGeR-HN2 is comparing petosemtamab to standard treatment options in second- and third-line settings for patients who have progressed after anti-PD-1 and platinum-based therapies. This trial also plans to enroll about 500 patients.
Disease Impact and Unmet Need
Head and neck squamous cell carcinoma represents a significant global health burden as the sixth most common cancer worldwide. In 2020 alone, there were over 930,000 new cases and 465,000 deaths globally. The incidence is projected to rise by 30% to more than 1 million new cases annually by 2030, highlighting the urgent need for more effective treatment options.
The Breakthrough Therapy designation is expected to expedite petosemtamab's development and review process, potentially accelerating its path to market. This includes more intensive FDA guidance and eligibility for rolling review and priority review, as Merus works toward a potential Biologics License Application submission.
