Drug repurposing reveals Posaconazole as a CYP11A1 inhibitor enhancing anti-tumour immunity

Steroid hormones regulate cell physiology and immune function, with dysregulated steroidogenesis promoting cancer progression by supporting tumour growth and suppressing anti-tumour immunity. Targeting CYP11A1, the first and rate-limiting enzyme in steroid biosynthesis, has shown promise in cancer therapy, but safe and effective inhibitors remain an unmet need. Undertaking in silico structure-based drug repurposing approach, we found Posaconazole as an inhibitor of CYP11A1. The docking pose analysis showed that Posaconazole can form multiple hydrogen bonds and hydrophobic interactions with the key residues at the binding site and the cofactor, stabilising the protein-ligand complex. We validated its inhibition efficiency in cell-based assays. In a mouse model of lung metastasis, we demonstrated that Posaconazole restricts metastatic cancer growth by stimulating anti-tumour immunity. These findings highlight Posaconazole’s potential as a research tool to study steroidogenesis and as a candidate for further preclinical and clinical evaluation in pathological conditions associated with local steroid production, such as steroidogenic tumours.