ABSTRACT
Divalent metal transporter 1 (DMT1) cotransports ferrous iron and protons and is the primary mechanism for uptake of non-heme iron by enterocytes. Inhibitors are potentially useful as therapeutic agents to treat iron overload disorders such as hereditary hemochromatosis or β-thalassemia intermedia, provided that inhibition can be restricted to the duodenum. We used a calcein quench assay to identify human DMT1 (hDMT1) inhibitors. Dimeric constructs 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 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 physiological function of DMT1.
SIGNIFICANCE STATEMENT This report introduces methodology to develop potent, gut-restricted inhibitors of 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.
Competing Interest Statement
All authors are or were employees of Xenon Pharmaceuticals Inc. The do or did receieve salaries from Xenon and may hold stock or stock options in the company.
Nonstandard abbreviations
- ANOVA
- analysis of variance
- aPTT
- activated partial thromboplastin time
- BCECF
- 2’,7’-bis-(2-carboxyethyl)-5-(And-6)-carboxyfluorescein, a pH indicator dye
- CFTR
- cystic fibrosis transmembrane conductance regulator
- CHO
- Chinese hamster ovary
- CYP3A4
- cytochrome P450 3A4, an enzyme important for drug metabolism
- DMT1
- divalent metal transporter 1
- GI
- gastrointestinal
- hDMT1
- human DMT1
- HEK
- human embryonic kidney
- HH
- hereditary hemochromatosis
- IV
- intravenous
- MES
- 4-morpholineethanesulfonic acid
- Papp
- apparent permeability coefficient
- p.o.
- per os (orally)
- PT
- prothrombin time
- Tet
- tetracycline