Oral Non-absorbable Polymer-Deferoxamine Conjugates for Reducing Dietary Iron Absorption

Hereditary hemochromatosis (HH) is a non-transfusional genetic iron overload (IO) disease wherein patients are not able to regulate dietary iron absorption, which ultimately leads to excess cellular iron accumulation. Preventative measures for HH mainly include phlebotomy and asking patients to minimize dietary iron intake. To investigate alternative iron reduction strategies, we report on prophylactic non-absorbable polymer-deferoxamine (DFO) conjugates capable of chelating and reducing excessive gut uptake of dietary iron. Three different sizes of the conjugates (56 nm, 256 nm, and 7.4 μm) were prepared, and their physicochemical properties, transit times in the gut under fed/fasted conditions, acute safety, and efficacy at reducing iron absorption in a dietary iron-overload mouse model were investigated. The conjugates were synthesized through reverse phase water-in-oil (w/o) emulsions, followed by conjugation of DFO to the resulting polymer scaffolds. In vitro studies using Caco-2 transwell assays showed that the conjugates could not permeate across the monolayer, were poorly endocytosed, and did not induce cellular toxicity. In vivo mouse studies via oral gavage demonstrated that polymer-DFO conjugates remained in the gastrointestinal (GI) tract for up to 12 h and significantly prevented escalation of serum ferritin levels and excess liver iron accumulation. Ex vivo images of the duodenum suggest that nanometer-sized conjugates (56 and 246 nm) perform better at chelating dietary iron based on longer retention times (i.e., entrapment in the villi of the duodenum) and an overall slower transit from the GI tract compared to larger micron-sized (7.4 μm) conjugates. Overall, nanometer-sized polymer-DFO conjugates were orally non-absorbable, appeared safe, and were more efficacious at reducing dietary iron absorption when taken with non-heme containing food.