On 18 February 2025, Merus announced that the FDA has granted Breakthrough Therapy Designation (BTD) to petosemtamab in combination with pembrolizumab for the first-line treatment of adults with recurrent or metastatic PD-L1 positive head and neck squamous cell carcinoma (r/m HNSCC).
This is the second BTD for petosemtamab following the same designation given in May 2024 for treatment of patients with r/m HNSCC whose disease has progressed following chemotherapy and an anti-PD-1 antibody. Petosemtamab received Fast Track designation for this indication in August 2023.