Repurposing tirbanibulin as an orally active E2-targeting entry inhibitor against Chikungunya virus.

BACKGROUND AND PURPOSE: Chikungunya virus (CHIKV) causes severe acute and chronic disease, yet no approved specific antiviral treatment exists. To rapidly identify potential treatments, we aimed to screen an FDA-approved drug library for inhibitors of CHIKV infection. Tirbanibulin, a dual-microtubule polymerization and Src kinase inhibitor, was assessed for its potential anti-CHIKV activity. METHODS: We performed a high-throughput screen of an FDA-approved drug library. Mechanism-of-action studies included entry-step analysis, surface plasmon resonance (SPR) binding assays and molecular docking. In vivo efficacy was evaluated in lethal murine neuroinfection and CHIKV-induced arthritis models following oral administration of the candidate compound. EXPERIMENTAL APPROACH: Tirbanibulin exhibited nanomolar to low-micromolar antiviral activity (EC50 range: 0.035-75.64 μM) across multiple cell lines, with high selective indices in key target HT22 and Huh7 cells. It acted at a post-attachment entry step, inhibiting clathrin-mediated endocytosis and potentially viral fusion. Surface plasmon resonance confirmed direct, high-affinity binding to the CHIKV E1 and E2 glycoprotein complex (K_D = 73 nM). In the lethal neuroinfection model, oral tirbanibulin significantly improved survival and reduced brain viral loads; in the arthritis model, it markedly attenuated footpad swelling and inflammatory pathology. CONCLUSION AND IMPLICATIONS: Tirbanibulin is a novel, orally bioavailable entry-stage inhibitor that directly targets the E2 glycoprotein. Multiple preclinical and clinical studies have confirmed its favourable oral bioavailability and safety. Given its established clinical safety profile, it represents a promising repurposing candidate for clinical evaluation against Chikungunya fever.