pyridoxal-isonicotinoyl-hydrazone and Iron-Overload

Topics: Animals; Antioxidants; Drug Evaluation, Preclinical; Humans; In Vitro Techniques; Iron; Iron Chelating Agents; Iron Overload; Isoniazid; Molecular Structure; Pyridoxal

At present, the only iron (Fe) chelator in clinical use for the treatment of Fe overload disease is the tris-hydroxamate deferoxamine (DFO). However, DFO suffers from a number of disadvantages, including the need for subcutaneous infusion (12 to 24 hours a day, 5 or 6 times per week), its poor intestinal absorption, and high cost. Therefore, there is an urgent need for an efficient, economical, and orally effective Fe chelator. Pyridoxal isonicotinoyl hydrazone (PIH) is a tridentate Fe-chelating agent that shows high Fe chelation efficacy both in vitro in cell culture models and also in vivo in rats and mice. In addition, this chelator is relatively nontoxic, economical to synthesize, and orally effective, and it shows high selectivity and affinity for Fe. However, over the last 10 years the development of PIH and its analogs has largely been ignored because of justifiable interest in other ligands such as 1,2-dimethyl-3-hydroxypyrid-4-one (L1). Unfortunately, recent clinical trials have shown that significant complications occur with L1 therapy, and it is controversial whether this chelator is effective at reducing hepatic Fe levels in patients. Because of the current lack of a clinically useful Fe chelator to replace DFO, PIH and its analogs appear to be potential candidate compounds that warrant further investigation. In this review we will discuss the studies that have been performed to characterize these chelators at the chemical and biologic levels as effective agents for treating Fe overload. The evidence from the literature suggests that these ligands deserve further careful investigation as potential orally effective Fe chelators.

Topics: Animals; Iron Chelating Agents; Iron Overload; Isoniazid; Mice; Pyridoxal; Rats

Topics: Administration, Oral; Animals; Deferiprone; Ferritins; Iron; Iron Chelating Agents; Iron Overload; Isoniazid; Pyridones; Pyridoxal; Rats; Treatment Outcome

Topics: Aldehydes; Animals; Deferoxamine; Humans; Hydrazones; Iron Chelating Agents; Iron Overload; Isoniazid; Myocardial Reperfusion Injury; Neoplasms; Pyridines; Pyridoxal; Rats; Reactive Oxygen Species; Thiosemicarbazones

The design of novel Fe chelators with high Fe mobilization efficacy and low toxicity remains an important priority for the treatment of Fe overload disease. We have designed and synthesized the novel methyl pyrazinylketone isonicotinoyl hydrazone (HMPIH) analogs based on previously investigated aroylhydrazone chelators. The HMPIH series demonstrated high Fe mobilization efficacy from cells and showed limited to moderate antiproliferative activity. Importantly, this novel series demonstrated irreversible electrochemistry, which was attributed to the electron-withdrawing effects of the noncoordinating pyrazine N-atom. The latter functionality played a major role in forming redox-inactive complexes that prevent reactive oxygen species generation. In fact, the Fe complexes of the HMPIH series prevented the oxidation of ascorbate and hydroxylation of benzoate. We determined that the incorporation of electron-withdrawing groups is an important feature in the design of N, N, O-aroylhydrazones as candidate drugs for the treatment of Fe overload disease.

Topics: Antineoplastic Agents; Ascorbic Acid; Benzoates; Cell Line, Tumor; Cell Proliferation; Crystallography, X-Ray; Humans; Hydrazones; Hydroxylation; Iron; Iron Chelating Agents; Iron Overload; Iron Radioisotopes; Isonicotinic Acids; Ketones; Ligands; Oxidation-Reduction; Pyrazines; Structure-Activity Relationship

Iron (Fe) chelation therapy was initially designed to alleviate the toxic effects of excess Fe evident in Fe-overload diseases. However, the novel toxicological properties of some Fe chelator-metal complexes have shifted appreciable focus to their application in cancer chemotherapy. Redox-inactive Fe chelator complexes are well suited for the treatment of Fe-overload diseases, whereas Fe chelator complexes with high redox activity have shown promising results as chemotherapeutics against cancer. Within this perspective, we discuss the different modes of action and toxicological profiles of Fe chelators, including analogues of 2-pyridylcarboxaldehyde isonicotinoyl hydrazone, di-2-pyridylketone isonicotinoyl hydrazone, di-2-pyridylketone thiosemicarbazone, and the clinically trialed chelator 3-aminopyridine-2-carboxaldehyde thiosemicarbazone. The potential application of these agents in the changing face of Fe chelation therapy is discussed.

Topics: Chelation Therapy; Humans; Hydrazones; Iron Chelating Agents; Iron Overload; Isoniazid; Pyridines; Pyridoxal; Structure-Activity Relationship; Thiosemicarbazones; Toxicology

Although iron chelation therapy with deferoxamine (DFO) has changed life expectancy in thalassemic patients, compliance with the rigorous requirements of long-term subcutaneous DFO infusions is unsatisfactory. This problem underlines the current efforts for developing alternative, orally effective chelators to improve compliance and treatment results. For the patient with transfusional iron overload in whom results of DFO treatment are unsatisfactory, several orally effective agents are now available. The most important of the new generation of oral chelators are deferiprone and ICL670. Total iron excretion with deferiprone is less than with DFO, but deferiprone has a better ability to penetrate cell membranes and may have a better cardioprotective effect than DFO. Current studies of the clinical efficacy and tolerability of ICL670 indicate that at a single oral dose of 20 mg/kg daily, it may be as effective as parenteral DFO used at the standard dose of 40 mg/kg daily. Combined chelation treatment, employing a weak chelator that penetrates cells better, and a stronger chelator with efficient urinary excretion, may result in improved therapeutic effect through iron shuttling between the two compounds. The efficacy of combined chelation treatment is additive and offers an increased likelihood of success in patients previously failing DFO or deferiprone monotherapy.

Topics: Administration, Oral; Benzoates; beta-Thalassemia; Chelation Therapy; Chemical and Drug Induced Liver Injury; Deferasirox; Deferiprone; Deferoxamine; Drug Therapy, Combination; Humans; Infusions, Intravenous; Iron Chelating Agents; Iron Overload; Isoniazid; Pyridones; Pyridoxal; Survival; Triazoles

Pyridoxal isonicotinoyl hydrazone (PIH) is a new tridentate Fe-chelating agent that should be very promising in many pathological states resulting from both an iron-overload and formation of free radicals. The aim of our study was to investigate the effect of PIH on the cardiovascular system focusing to the regulatory protein -- cardiac troponin T (cTnT). The study was carried out in two groups of Chinchilla male rabbits: 1) PIH (50 mg/kg dissolved in 10 % Cremophor i.p., once a week, 10 administrations, n=8) and 2) Cremophor (2 ml/kg i.p. in the same schedule, n=7). Plasma concentrations of cTnT (as a marker of myocardial damage) were measured using a commercial kit (Roche). cTnT was within the physiological range (i.e. < 0.1 microg/l) during the whole experiment in the Cremophor group. In the PIH group, the cTnT levels were not significantly increased when compared with the control group or with the initial values (except with those before the 5th administration). Furthermore, we analyzed the cytosolic and myofibrillar fraction of cTnT in the left ventricular myocardium. Using SDS-PAGE and Western blot we resolved three isoforms. The profiling of TnT did not differ significantly between the PIH-treated group and the Cremophor-treated group. Our data concerning cTnT support the opinion that the possible cardiotoxicity of PIH is very low.

Topics: Animals; Cell Fractionation; Cytosol; Iron Chelating Agents; Iron Overload; Isoniazid; Male; Myocardium; Myofibrils; Pyridoxal; Rabbits; Troponin T