Background: Pmab has demonstrated significant improvement in progression-free survival (PFS) in pts with WT KRAS mCRC as 1st-line tx in a phase III trial comparing pmab + FOLFOX4 vs FOLFOX4 alone. Here, we describe the results of PEAK, a multicenter, randomized phase II study evaluating pmab + mFOLFOX6 and bev + mFOLFOX6 in pts with previously untreated WT KRASmCRC. Methods: Pts were randomized 1:1 to pmab 6.0 mg/kg + mFOLFOX6 Q2W or bev 5.0 mg/kg + mFOLFOX6 Q2W. Pt eligibility criteria included: WT KRASmCRC, ECOG performance status ≤ 1, and no prior chemotherapy, anti-VEGF tx, or anti-EGFR tx for mCRC. The primary endpoint was PFS; secondary endpoints included overall survival (OS), objective response rate (ORR), and safety. No formal hypothesis was tested. Results: 285 pts with WT KRASmCRC were randomized and 278 pts received tx. Demographics were balanced between arms. Intent-to-treat efficacy results are shown (Table). Worst grade 3/4 adverse events (AE) occurred in 86% of pts in the pmab + mFOLFOX6 arm vs 76% of pts in the bev + mFOLFOX6 arm. Grade 5 AEs occurred in 5% of pts in the pmab + mFOLFOX6 arm and 6% of pts in the bev + mFOLFOX6 arm. Tx discontinuation due to any AE was 24% in the pmab + mFOLFOX6 arm and 27% in the bev + mFOLFOX6 arm. Conclusions: In this estimation study of pts with WT KRASmCRC without any prior therapy for mCRC, PFS and ORR were similar between arms. The median OS was not reached in the pmab + mFOLFOX6 arm. The safety profile for both arms was consistent with previously reported studies of either combination. Tx discontinuation rates due to AEs were similar between arms. Clinical trial information: NCT00819780.

Abbreviation: NR, not reached. ^#Assessments based on investigator review per modified RECIST 1.0. Pts with measureable lesion were included in the ORR analysis.