Petosemtamab (MCLA 158) is a highly potent monoclonal antibody against EGFR (Kd: 0.22 nM) and LGR5 (Kd: 0.86 nM). Petosemtamab promotes EGFR signaling disruption and receptor breakdown in LGR5+ cancer cells. Petosemtamab can be used in the study of solid tumors such as head and neck squamous cell carcinoma (HNSCC) and metastatic colorectal cancer (CRC).