Abstract: Antibodies to the enzyme matriptase-2 (MTP-2) are presented. Inhibiting MTP-2 reduces uptake of dietary iron and reduces the release of iron from cellular stores in the body. Inhibitors of MTP-2 (such as antibodies to the serine protease domain) can be used to treat iron overload, which is a feature of diseases such as beta-thalassaemia and which otherwise leads to toxic accumulation of iron. Combination of an MTP-2 inhibitor with an activin receptor ligand trap, or with erythropoietin, provides additional therapeutic effects.