Alshammari K, Aung KL, Zhang T, et al. - A phase II trial was conducted to assess antitumor activity of trametinib (MEK1/2 inhibitor) with panitumumab [epidermal growth factor receptor (EGFR) monoclonal antibody] in patients with KRAS, NRAS, and BRAF wildtype (wt) metastatic colorectal cancer with prior 5-FU, irinotecan, oxaliplatin, +/- bevacizumab and no prior anti-EGFR therapy. Participants were administered trametinib 1.5mg oral daily and panitumumab 4.8mg/kg IV every 2 weeks. In this study with 14 patients, a clinical benefit rate of 38% (5/13) and a median progression free survival (PFS) of 4.4 months were obtained. Confirmed overall response rate was 38% (5/13). Findings revealed a high rate of tumor shrinkage was achieved with the addition of trametinib to panitumumab in the treatment of RAS/RAF wt metastatic colorectal cancer, however, high incidence of skin toxicity resulted in a poor tolerability. A median PFS similar to panitumumab alone was witnessed in historical control data.