Background: LCCC1029 was a 2:1 randomized phase II trial of 2nd-line FOLFIRI plus either regorafenib or placebo in mCRC. The addition of regorafenib improved PFS (median PFS 6.1 vs 5.3 mo, HR 0.73, 95% CI 0.53-1.01). However, the effect of somatic mutations on regorafenib activity has not been tested. Methods: We performed whole exome sequencing on archival primary tumor tissue and paired normal tissue in 85 patients of LCCC1029. We compared PFS and OS using Kaplan-Meier method and log-rank tests, and hazard ratios (HR) were estimated using Cox proportional hazards method. Results: Among the 85 subjects, 54 (64%) had tumors wild-type (WT) for KRAS and BRAF, 26 (31%) had tumors with KRAS mutations in exons 2-4, and 5 (6%) had tumors with BRAF V600E. The addition of regorafenib to FOLFIRI improved PFS in the KRAS/BRAF WT subgroup (median PFS 8.0 vs 4.9 mo, HR 0.68, 95% CI 0.48-0.97, log-rank p=0.028), but not in the KRAS mutant subgroup (median PFS 6.8 vs 5.5 mo, HR 0.90, 95% CI 0.61-1.35, log-rank p=0.617) or the BRAF mutant subgroup (log-rank p=0.156). In all of these subgroups, the addition of regorafenib was not associated with significant difference in OS. BRAF V600E was prognostic and associated with significantly worse OS (median OS 8.4 vs 18.0 mo, HR 2.59, 95% CI 1.01-6.66, log-rank p=0.04). Conclusions: The addition of regorafenib to FOLFIRI improves PFS among the subgroup of patients with KRAS and BRAF dual WT CRC, but not among the KRAS mutant subgroup. These results indicate that the addition of anti-angiogenic therapy to second-line chemotherapy backbones may be more effective in KRAS/BRAF WT tumors in particular. More confirmatory studies are needed to corroborate this finding.