Contributions
Abstract: EP842
Type: E-Poster Presentation
Session title: Iron metabolism, deficiency and overload
Background
Iron overload is a condition whereby excess iron is stored in peripheral tissues and can be caused by genetic mutations, or introduced via blood transfusions, hemolysis or diet. Excess deposition of iron in liver, heart and endocrine organs leads to toxicity and loss of function. Hepcidin, a key endocrine regulator of iron metabolism, mediates dietary iron uptake and iron levels in blood. Hepcidin circulates to tissues and binds to and activates the degradation of the iron exporter, ferroportin. Thus, when hepcidin is high, iron is sequestered within cells resulting in increased tissue iron levels and reduced serum iron availability. Likewise, when hepcidin expression is suppressed, ferroportin-mediated iron efflux results in the mobilization of iron out of tissues. Hepcidin is expressed, at least in part, in response to signaling through the ALK2 receptor, a type I TGF-β receptor, and inhibition of ALK2 results in reduced hepcidin expression and increased serum iron. We have shown in pre-clinical and clinical studies that ALK2 inhibition suppressed hepcidin expression. Indeed, we have previously reported in a Phase 1 clinical trial that inhibition of ALK2 with KER-047, a small molecule ALK2 kinase inhibitor, elicited rapid, robust and sustained dose-related increases in serum iron that were associated with decreases in hepcidin. The potential of ALK2 inhibition to aid export of iron from tissues may increase the available therapeutic modalities for the treatment of iron overload.
Aims
To test the efficacy of modulating ALK2 activity to regulate hepcidin and mobilize hepatic iron in an inducible model of iron overload.
Methods
To induce iron overload, CD1 mice were dosed QD via IP administration with 100mg/kg of iron dextran or vehicle. Post 20 days of iron loading, a subgroup of mice was used to confirm iron overload. The remaining iron loaded mice were dosed QD with either KTI-2338, a small molecule selective ALK2 kinase inhibitor (5 mg/kg) or vehicle. Iron dextran administration continued throughout. Mice were sacrificed 16hr post the 1st dose (16hr) and 12hr post the 3rd dose (63hr) of KTI-2338 and livers dissected and weighed. Non-heme tissue iron was extracted via acid hydrolysis and iron levels determined using the bathophenanthroline disulfonate method.
Results
Iron overload was confirmed in the mice dosed with iron dextran (ID-Veh) with a substantial 30-fold increase in hepatic iron compared to mice not receiving iron (Veh-Veh) (Veh-Veh: 648.4±36.01mg/g v ID-Veh: 19291±513.7mg/g, p<0.0001). No differences were observed in hepatic iron at 16hr post dose. By 63hr of KTI-2338 dosing, significant reductions in liver non-heme iron content was observed, resulting in a 62% decrease compared to vehicle treated mice (63hr ID-Veh: 25162±974.5mg/g v 63hr ID-2338: 9559±339.2mg/g, p<0.0001).
Conclusion
In this proof-of-concept study, ALK2 inhibition in a state of severe iron overload led to rapid and marked reductions in liver iron. In the clinic, chelation therapy is used to remove excess iron from circulation; however, due to the efficiency of iron cycling, this procedure can be ineffective or require a lengthy therapeutic regimen. We hypothesize that in conditions with iron overload, ALK2 inhibition may potentially be used to export excess iron from the liver, allowing for more effective chelation therapy. Future studies will assess the efficacy of KTI-2338 to reduce ectopic iron in sensitive tissues such as the heart and determine if this can be combined with chelation to rescue the pathologies of iron overload.
Keyword(s): Hepcidin, Iron metabolism, Iron overload
Abstract: EP842
Type: E-Poster Presentation
Session title: Iron metabolism, deficiency and overload
Background
Iron overload is a condition whereby excess iron is stored in peripheral tissues and can be caused by genetic mutations, or introduced via blood transfusions, hemolysis or diet. Excess deposition of iron in liver, heart and endocrine organs leads to toxicity and loss of function. Hepcidin, a key endocrine regulator of iron metabolism, mediates dietary iron uptake and iron levels in blood. Hepcidin circulates to tissues and binds to and activates the degradation of the iron exporter, ferroportin. Thus, when hepcidin is high, iron is sequestered within cells resulting in increased tissue iron levels and reduced serum iron availability. Likewise, when hepcidin expression is suppressed, ferroportin-mediated iron efflux results in the mobilization of iron out of tissues. Hepcidin is expressed, at least in part, in response to signaling through the ALK2 receptor, a type I TGF-β receptor, and inhibition of ALK2 results in reduced hepcidin expression and increased serum iron. We have shown in pre-clinical and clinical studies that ALK2 inhibition suppressed hepcidin expression. Indeed, we have previously reported in a Phase 1 clinical trial that inhibition of ALK2 with KER-047, a small molecule ALK2 kinase inhibitor, elicited rapid, robust and sustained dose-related increases in serum iron that were associated with decreases in hepcidin. The potential of ALK2 inhibition to aid export of iron from tissues may increase the available therapeutic modalities for the treatment of iron overload.
Aims
To test the efficacy of modulating ALK2 activity to regulate hepcidin and mobilize hepatic iron in an inducible model of iron overload.
Methods
To induce iron overload, CD1 mice were dosed QD via IP administration with 100mg/kg of iron dextran or vehicle. Post 20 days of iron loading, a subgroup of mice was used to confirm iron overload. The remaining iron loaded mice were dosed QD with either KTI-2338, a small molecule selective ALK2 kinase inhibitor (5 mg/kg) or vehicle. Iron dextran administration continued throughout. Mice were sacrificed 16hr post the 1st dose (16hr) and 12hr post the 3rd dose (63hr) of KTI-2338 and livers dissected and weighed. Non-heme tissue iron was extracted via acid hydrolysis and iron levels determined using the bathophenanthroline disulfonate method.
Results
Iron overload was confirmed in the mice dosed with iron dextran (ID-Veh) with a substantial 30-fold increase in hepatic iron compared to mice not receiving iron (Veh-Veh) (Veh-Veh: 648.4±36.01mg/g v ID-Veh: 19291±513.7mg/g, p<0.0001). No differences were observed in hepatic iron at 16hr post dose. By 63hr of KTI-2338 dosing, significant reductions in liver non-heme iron content was observed, resulting in a 62% decrease compared to vehicle treated mice (63hr ID-Veh: 25162±974.5mg/g v 63hr ID-2338: 9559±339.2mg/g, p<0.0001).
Conclusion
In this proof-of-concept study, ALK2 inhibition in a state of severe iron overload led to rapid and marked reductions in liver iron. In the clinic, chelation therapy is used to remove excess iron from circulation; however, due to the efficiency of iron cycling, this procedure can be ineffective or require a lengthy therapeutic regimen. We hypothesize that in conditions with iron overload, ALK2 inhibition may potentially be used to export excess iron from the liver, allowing for more effective chelation therapy. Future studies will assess the efficacy of KTI-2338 to reduce ectopic iron in sensitive tissues such as the heart and determine if this can be combined with chelation to rescue the pathologies of iron overload.
Keyword(s): Hepcidin, Iron metabolism, Iron overload