Everolimus and Tivozanib

The combination of everolimus and tivozanib is a targeted therapy regimen used primarily in the treatment of renal cell carcinoma (RCC). This combination brings together two distinct mechanisms of action: everolimus as an mTOR inhibitor and tivozanib as a VEGF receptor tyrosine kinase inhibitor. ### Mechanism of Action The combination works through complementary pathways: - Tivozanib inhibits vascular endothelial growth factor receptors (VEGFR-1, VEGFR-2, and VEGFR-3), which blocks tumor angiogenesis, growth, and vascular permeability. It also inhibits other kinases such as c-kit and platelet-derived growth factor receptor beta (PDGFR β). - Everolimus inhibits mTOR (mammalian target of rapamycin), forming a complex with FK506 binding protein-12 (FKBP-12) that blocks cell progression from G1 to S phase, inducing cell growth arrest and apoptosis. This inhibition reduces cell proliferation, angiogenesis, and glucose uptake. ### Clinical Evidence A phase Ib/II multicenter study evaluated the combination in patients with refractory, metastatic colorectal cancer, with the phase II study meeting its primary endpoint. The recommended dosing from this study was oral tivozanib (1 mg daily for 3 of 4 weeks) and oral everolimus (10 mg daily continuously). Common grade 3-4 adverse events included thrombocytopenia and hypophosphatemia. ### Current Use While tivozanib alone is approved as a third-line or later therapy for advanced renal cell carcinoma, the combination is being considered for use in RCC. It is noted that tivozanib may offer better tolerability compared to lenvatinib when combined with everolimus, with lower rates of grade 3-4 fatigue and diarrhea.