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).

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 evalua...