Discovery of a novel miconazole analogue as a dual apo-IDO1 inhibitor and ABCB1 modulator for cancer immunotherapy...

Indoleamine 2,3-dioxygenase 1 (IDO1) facilitates tumoral immune evasion via the kynurenine (Kyn) pathway, while ABCB1-mediated efflux drives multidrug resistance. Previously, miconazoles were reported as potent IDO1 inhibitors and some azole antifungals inhibit efflux pumps. Herein, we report a miconazole analogue, 1g, which inhibits both mechanisms. An in-house library of miconazole analogues, incorporating oxime ether derivatives with imidazole and pyrazole rings, was screened against Kyn production in IDO1-expressing SK-OV-3 and HeLa cells, yielding the hit pyrazole derivative 1g (IC_50(Kyn) = ∼5.8 µM). In vitro LDH assay showed minimal cytotoxicity for 1g and it was well tolerated by in vivo zebrafish model at 2 × IC_{50(Kyn-SK-OV-3)} concentrations. Molecular modelling and biochemical assays indicated apo-form preference for 1g, which suppressed Kyn production without affecting IDO1 protein levels or inducing apoptosis. In indirect co-cultured models, 1g reversed Kyn-mediated immunosuppression, significantly restoring pro-IL1B and TNF levels in LPS-induced THP-1 macrophages. Furthermore, 1g restored Jurkat T cell proliferation, aggregate formation, and PDCD1 expression independent of direct 1g exposure, confirming a Kyn-dependent mechanism. Finally, 1g inhibited ABCB1 function in a dose-dependent manner and enhanced the sensitivity of ABCB1-expressing cells to paclitaxel, demonstrating its efficacy as a multidrug resistance (MDR) reversal agent. Our findings characterised 1g as a promising low-micromolar dual inhibitor of apo-IDO1 and ABCB1 with minimal cytotoxicity. It simultaneously disrupts the immunosuppressive Kyn axis and modulates ABCB1-mediated efflux, which provides a robust pharmacological basis for further development of next-generation combinatorial therapies.