Potent, Gut-Restricted Inhibitors of Divalent Metal Transporter 1: Preclinical Efficacy against Iron Overload and Safety Evaluation.

Divalent metal transporter 1 (DMT1) cotransports ferrous iron and protons and is the primary mechanism for uptake of nonheme iron by enterocytes. Inhibitors are potentially useful as therapeutic agents to treat iron overload disorders such as hereditary hemochromatosis or ß-thalassemia intermedia, provided that inhibition can be restricted to the duodenum. We used a calcein quench assay to identify human DMT1 inhibitors. Dimeric compounds were made to generate more potent compounds with low systemic exposure. Direct block of DMT1 was confirmed by voltage clamp measurements. The lead compound, XEN602, strongly inhibits dietary nonheme iron uptake in both rats and pigs yet has negligible systemic exposure. Efficacy is maintained for >2 weeks in a rat subchronic dosing assay. Doses that lowered iron content in the spleen and liver by >50% had no effect on the tissue content of other divalent cations except for cobalt. XEN602 represents a powerful pharmacological tool for understanding the physiologic function of DMT1 in the gut. SIGNIFICANCE STATEMENT: This report introduces methodology to develop potent, gut-restricted inhibitors of divalent metal transporter 1 (DMT1) and identifies XEN602 as a suitable compound for in vivo studies. We also report novel animal models to quantify the inhibition of dietary uptake of iron in both rodents and pigs. This research shows that inhibition of DMT1 is a promising means to treat iron overload disorders.

Discovery of benzylisothioureas as potent divalent metal transporter 1 (DMT1) inhibitors.

Inhibition of intestinal brush border DMT1 offers a novel therapeutic approach to the prevention and treatment of disorders of iron overload. Several series of diaryl and tricyclic benzylisothiourea compounds as novel and potent DMT1 inhibitors were discovered from the original hit compound 1. These compounds demonstrated in vitro potency against DMT1, desirable cell permeability properties and a dose-dependent inhibition of iron uptake in an acute rat model of iron hyperabsorption. Tricyclic compounds increased the in vitro potency by up to 16-fold versus the original hit. Diaryl compounds 6b and 14a demonstrated significant iron absorption inhibition in vivo with both 25 and 50 mg/kg doses. The diaryl and tricyclic compounds described in this report represent promising structural templates for further optimization.

Synthesis and biological evaluation of substituted pyrazoles as blockers of divalent metal transporter 1 (DMT1).

Three distinct series of substituted pyrazole blockers of divalent metal transporter 1 (DMT1) were elaborated from the high-throughput screening pyrazolone hit 1. Preliminary hit-to-lead efforts revealed a preference for electron-withdrawing substituents in the 4-amido-5-hydroxypyrazole series 6a-l. In turn, this preference was more pronounced in a series of 4-aryl-5-hydroxypyrazoles 8a-j. The representative analogs 6f and 12f were found to be efficacious in a rodent model of acute iron hyperabsorption. These three series represent promising starting points for lead optimization efforts aimed at the discovery of DMT1 blockers as iron overload therapeutics.