Exploratory RAS analysis of the phase Ib/II 20060447 trial of rilotumumab (R) or ganitumab (G) plus panitumumab (pmab) versus pmab alone in patients (pts) with previously treated metastatic colorectal cancer (mCRC).

Abstract

694 Background: Pmab, R, and G are fully human monoclonal antibodies that target EGFR, HGF, and IGF-1R, respectively. In part 2 of this 3-part study in previously treated pts with wild-type (WT) KRAS mCRC, pmab+R met the pre-specified criterion for improvement in objective response rate (ORR) whereas pmab+G did not. We report an exploratory analysis of the treatment effect of pmab, R, and G in pts with activating RAS mutations beyond KRAS exon 2. Methods: Part 2 was a phase II, randomized, double-blinded trial of pmab+R or pmab+G vs. pmab+placebo, administered Q2W until disease progression or intolerance. The primary endpoint was ORR. Secondary endpoints included overall survival (OS), progression-free survival (PFS), and safety. Mutations in KRAS exon 3 (codons 59/61) and exon 4 (codons 117/146); NRAS exon 2 (codons 12/13), exon 3 (codons 59/61), and exon 4 (codons 117/146); and BRAF exon 15 (codon 600) were detected by bidirectional Sanger sequencing. Results: Of 142 pts randomized, 92 (65%) were evaluable for RAS. Of 92 evaluable pts, 79 (86%) were WT RAS (WT in KRAS and NRAS exons 2, 3, and 4) and 13 (14%) had RAS mutations beyond KRAS exon 2 (mutant in any KRAS exon 3 or 4 or NRAS exon 2, 3, or 4). None of the pts with RAS mutations had an objective response (Table). Of 93 pts evaluable for BRAF, 7 (8%) had V600E mutations (all 7 were WT RAS). Two pts with BRAF V600E tumors had a partial response and were in the pmab+R arm (n=3). No new safety signals were identified. Conclusions: In this small, retrospective study, ORR, PFS and OS were similar between the arms of R or G plus pmab vs pmab alone in pts with WT RAS mCRC tumors. Our findings indicate that RAS mutations beyond KRAS exon 2 impact ORR, PFS, and OS. Clinical trial information: NCT00788957. [Table: see text]