In vitro and in vivo activity of a novel sorafenib derivative SC5005 against MRSA

Objectives: The emergence of MRSA strains resistant to most antibiotics is a serious threat to public health. Based on our discovery that the tyrosine kinase inhibitor sorafenib exhibits inhibitory activity against Staphylococcus species, the objective of this study is to exploit this unique antibacterial activity of sorafenib to develop novel antibacterial agents against MRSA. Methods: A sorafenib-based focused compound library was synthesized by substituting the pyridinyl and phenyl groups with different functional groups. The resulting sorafenib derivatives were screened for growth-suppressive activities against Staphylococcus aureus and Staphylococcus epidermidis following CLSI guidelines and for cytotoxicity towards human cells using MTT cell viability assays. Compounds with high selectivity for bacterial inhibition over cytotoxicity were further evaluated by time-kill assay and Caenorhabditis elegans and mice survival assays to evaluate their efficacy in vitro and in vivo. Results: The screening of sorafenib derivatives led to the identification of compound SC5005 as a lead compound with high potency in killing different clinical strains of MRSA with an MIC₉₀ of 0.5 mg/L and with low cytotoxicity, as demonstrated by IC₅₀-to-MIC ratios of up to 40. In addition, SC5005 showed a significant protective effect in MSSA- or MRSA-infected C. elegans. Intraperitoneal administration of SC5005 at 10 mg/kg significantly improved the survival of MRSA-infected C57BL/6 mice. Conclusions: In light of its high potency in suppressing MRSA in both in vitro and in vivo models, SC5005 represents a potential lead agent for continued preclinical development as a therapeutic intervention against MRSA.