The small molecule NLRP3 inhibitor RRx-001 potentiates regorafenib activity and attenuates regorafenib-induced toxicity in mice bearing human colorectal cancer xenografts.

The multi-kinase inhibitor Regorafenib, approved for the treatment of metastatic colorectal cancer, is poorly tolerated with a Grade 3/4 drug related adverse event rate of 54% resulting in frequent dose reductions and discontinuations. RRx-001 is a minimally toxic NLRP3 inhibitor small molecule with macrophage-repolarizing properties in Phase 3 clinical trials. Studies have demonstrated the inhibitory impact of M2 macrophages on the activity of tyrosine kinases, suggesting that the repolarization of macrophages by RRx-001 may enhance the activity of TKIs. The purpose of these experiments was to determine whether RRx-001 demonstrated and synergy with regorafenib in colorectal cancer and whether RRx-001 attenuated the toxicity of regorafenib. Tumor-bearing mice were randomized into four cohorts: RRx-001 alone, regorafenib alone, RRx-001 + regorafenib and control. RRx-001 demonstrated and synergy with regorafenib with attenuation of toxicity in colorectal cancer cell lines. These results provide a rationale to treat colorectal cancer with RRx-001 plus another tyrosine kinase inhibitor like regorafenib.