Evidence of enhanced iron excretion during systemic phosphorothioate oligodeoxynucleotide treatment

Background: Phosphorothioate oligonucleotides, in general, possess properties that could be utilized in the development of therapeutic heavy metal chelators. Methods: Iron excretion was measured in 16 patients participating in studies to test the safety of OL(1)p53, a 20-mer phosphorothioate oligonucleotide complementary to p53 mRNA. Patients were given OL(1)p53 at doses of 0.05 to 0.25 mg/kg/h for 10 days by continuous intravenous infusion. Urine was collected during the study and analyzed for iron, copper, cadmium, and zinc. Results: We found that phosphorothioate oligonucleotides have a high affinity for iron as well as several other clinically relevant toxic metals. Analysis of patient urine following administration of OL(1)p53 reveals a 7.5-fold increase in iron excretion at low doses (0.05 mg/kg/h). Conclusions: Phosphorothioate oligonucleotides may have therapeutic potential as heavy metal chelators. Low doses of phosphorothioate oligonucleotide facilitated the excretion of iron. Renal clearance of iron-phosphorothioate oligonucleotide complexes most likely involves secretion into proximal tubules.