Core Insights - Merus N.V. announced interim clinical data for petosemtamab, a bispecific antibody, showing promising response rates in metastatic colorectal cancer (mCRC) patients [1][2][3] Group 1: Clinical Data Summary - In the ongoing phase 2 trial, petosemtamab demonstrated a 100% response rate in first-line (1L) left-sided mCRC patients (n=8) and a 62% response rate in second-line (2L) mCRC patients (n=13) [1][3] - The trial included 54 patients with left- and/or right-sided, KRAS, NRAS, and BRAF wildtype microsatellite stable mCRC, treated with petosemtamab in combination with FOLFOX/FOLFIRI or as monotherapy [3] - In the 1L treatment group, 10 patients were efficacy evaluable, with 8 left-sided patients showing an 80% response rate, including 1 confirmed complete response and 7 partial responses [3][7] Group 2: Mechanism of Action and Potential Impact - Petosemtamab targets both EGFR and LGR5, which may provide a new treatment option for patients with EGFR inhibitor-naïve mCRC [2] - The early results suggest that petosemtamab could become a transformational treatment and a new standard of care for various solid tumors [2] Group 3: Safety Profile - The safety profile of petosemtamab in mCRC appears consistent with its established profile in recurrent/metastatic head and neck squamous cell carcinoma, with no significant overlapping toxicities identified [7] - Infusion-related reactions were managed effectively, with no discontinuations due to these reactions [7]