An immunometabolic prodrug strategy overcomes DHODH inhibitor resistance in refractory melanoma

Metabolic reprogramming, particularly upregulated de novo pyrimidine biosynthesis, drives cancer progression and immune evasion. Dihydroorotate dehydrogenase (DHODH), a key enzyme in this pathway, is a promising therapeutic target, but its inhibitors often face resistance in immune-refractory melanoma, linked to low basal stimulator of interferon genes (STING) expression.

To overcome this limitation, we designed H62, a tumor-selective prodrug conjugating the DHODH inhibitor EA6 with the STING agonist MSA-2 via a cathepsin B-cleavable linker. Mechanistic studies evaluated mitochondrial disruption, pyroptosis (caspase-3/GSDME), and STING-mediated interferon signaling, alongside natural killer (NK) cell recruitment. Efficacy was tested in multiple melanoma models, including standard and neoadjuvant settings.

H62 synergistically induced mitochondrial dysfunction and pyroptosis while activating STING/type I interferon responses, enhancing NK cell cytotoxicity. In melanoma models, it significantly suppressed tumor growth, reduced postoperative recurrence, and improved survival.

This dual-targeting strategy overcomes DHODH inhibitor resistance by coupling metabolic interference with innate immune activation, offering translational potential for melanoma and other treatment-resistant cancers.