- Petosemtamab combined with FOLFOX/FOLFIRI shows antitumor activity in mCRC.
- 36 patients received petosemtamab in combination or as monotherapy.
- Updated data to be presented on October 24 at 10:20 a.m. ET.
- No fatal treatment-related adverse events observed.
Clinical Trial Overview
Merus N.V. announced interim data from a phase 2 trial of petosemtamab, a bispecific antibody, in combination with FOLFOX/FOLFIRI for first and second-line metastatic colorectal cancer (mCRC) and as monotherapy for third-line and beyond mCRC. The data cutoff was April 28, 2025, and updated results will be presented at the AACR-NCI-EORTC conference.
Patient and Treatment Details
The trial involved 36 patients with left- and/or right-sided, KRAS, NRAS, and BRAF wildtype microsatellite stable mCRC. Patients received petosemtamab 1500 mg biweekly, either with FOLFOX/FOLFIRI or as monotherapy. In the first-line group, 7 patients were treated, with 6 ongoing, and 3 were efficacy evaluable. In the second-line group, 10 patients were treated, with 8 ongoing, and 8 were efficacy evaluable. In the third-line and beyond group, 19 patients were treated, with 12 ongoing, and 14 were efficacy evaluable.
Results and Observations
In the first-line group, 1 unconfirmed complete response and 2 partial responses were observed. In the second-line group, 4 partial responses, 3 stable diseases, and 1 clinical deterioration were noted. In the third-line and beyond group, 1 unconfirmed partial response, 6 stable diseases, and 6 progressive diseases were observed. No fatal treatment-related adverse events were reported across all cohorts.
Safety Profile
Common treatment-emergent adverse events included dermatitis acneiform, constipation, fatigue, and peripheral neuropathy for petosemtamab plus FOLFOX, and diarrhea, mucosal inflammation, and fatigue for petosemtamab plus FOLFIRI. For petosemtamab monotherapy, rash and nausea were the most frequent adverse events.
