e14558 Background: Epithelial growth factor receptor (EGFR) inhibitors are not effective in KRAS mutant colorectal tumors. In these tumors the k-ras protein is activated by post-translational modification by binding farnesyl (C15) and geranylgeranyl (C17) moieties. Both are products of the mevalonate pathway, as is cholesterol. Statins (HMG-CoA-reductase inhibitors) not only inhibit synthesis of cholesterol, but also of C15 and C17 and thus may relevantly inhibit post-translational activation of ras proteins. Therefore, statins may inhibit the expression of the mutant KRAS phenotype and normalize the phenotype into KRAS wild type. In a phase II study we investigated whether simvastatin treatment renders KRAS mutant colorectal tumors sensitive to panitumumab. Methods: Major eligibility criteria were advanced or metastatic colorectal cancer failing prior 5FU, oxaliplatin and irinotecan containing regimens, with a mutation in codon 12, 13 or 61 of KRAS gene on tumor sample. Patients were treated with simvastatin 80mg once daily and panitumumab 6mg/kg every 2 weeks. Primary objective was to investigate the percentage of patients free from progression and alive 11 weeks after the first administration of panitumumab. This phase II study was performed in a Simon two stage design, performing an interim analysis after the enrolment of 15 patients. When at least 6 of these patients (i.e. 40%) were to be alive and free from progression free at 11 weeks after the first administration of panitumumab (similar to the results of the KRAS wild type population of the phase III study), another 31 patients would be included during stage 2. Results: Fifteen evaluable patients were enrolled by 4 study sites. Only one patient was free from progression 11 weeks after start of panitumumab treatment (6.7%). Mean progression free survival was 9.1 weeks (range 5-17 weeks). Most frequent reported side effect was skin toxicity (40%), one patient experienced myositis grade 3. Conclusions: Simvastatin 80mg once daily was not able to inhibit the KRAS mutant phenotype sufficiently to reach sensitivity to panitumumab in colorectal cancer patients with a mutation in the KRAS gene. Clinical trial information: NCT01110785.
Phase II study of high-sensitivity genotyping of KRAS, NRAS, BRAF and PIK3CA to ultra-select metastatic colorectal cancer patients for panitumumab plus FOLFIRI: the ULTRA trial
