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

Abstract

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 in vitro and in vivo 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 in vitro and in vivo 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.

Keywords: Chemotherapy; RRx-001; colorectal cancer; regorafenib; tyrosine kinase inhibitor.

Figure 1

Cytotoxic effects of RRx-001 (black) and regorafenib (red) on (left panel) HCT-116 (right panel) HCT-15, expressed as the relative viability (percentage of untreated control), as determined by an MTT assay. Bars, mean + SE.

Figure 2

Tumor volume and body weight changes (BWC) in HCT-116 and HCT-15 xenografted mice after (A) control (no treatment) (B) RRx-001 alone twice per week for 2 weeks at 5 mg/kg (C) daily regorafenib alone 21/28 days for up to 16 weeks (D) RRx-001 twice per week for 2 weeks at 5 mg/kg followed by daily regorafenib 21/28 days for up to 16 weeks. Tumor volume changes and BWC in HCT-116 and HCT-15 xenografts are shown, respectively. Values indicate mean ± SD (n = 4).