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# Merus Breakthrough Status for Petosemtamab
- URL: https://www.fdaweb.com/merus-breakthrough-status-for-petosemtamab/
- Published: 2024-05-13T12:00:00.000Z
- Updated: 2026-09-14T14:30:40.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5156966

FDA has granted Merus a breakthrough therapy designation for petosemtamab for treating patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) whose disease has progressed following treatment with platinum-based chemotherapy and an anti-programmed cell death receptor-1 or anti-programmed death ligand 1 antibody. The designation is based on data from an ongoing Phase 1/2 open-label, multicenter trial evaluating petosemtamab monotherapy in patients with advanced solid tumors, including previously treated (recurrent or metastatic) HNSCC. Merus plans to provide updated efficacy, durability and safety data from the study in the second half of this year.

“We look forward to continued constructive conversations with the FDA as we move forward in our plan to initiate a Phase 3 trial in previously treated HNSCC mid-2024 and prepare for a potential Phase 3 trial evaluating the combination of petosemtamab and pembrolizumab in previously untreated patients,” the company says.

Petosemtamab, or MCLA-158, is described as a biclonics low-fucose human full-length IgG1 antibody targeting the epidermal growth factor receptor (EGFR) and the leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5). “Petosemtamab is designed to exhibit three independent mechanisms of action including inhibition of EGFR-dependent signaling, LGR5 binding leading to EGFR internalization and degradation in cancer cells, and enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) activity,” Merus says.