A Pilot Clinical Trial With the Iron Chelator Deferiprone in Parkinson's Disease

BACKGROUND Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects approximately 2% of the population aged over 60 years. The common clinical motor control features are tremor, bradykinesia, postural abnormality and rigidity. However, in many patients non-motor features such as cognitive decline, depression, autonomic disturbances also occur as the disease progresses. The principal pathology is the degeneration of the nigrostriatal dopaminergic system which plays a major role in movement control through the release of dopamine in the striatum. Current therapeutic approach focus on dopamine replacement strategies either through the dopamine precursor L-DOPA or the use of dopamine agonists, and/or the use of monoamine oxidase inhibitors or catecholamine transferase inhibitors which prevent the breakdown of dopamine or facilitate L-DOPA entry into the brain. However, such therapeutic approaches are associated with declining efficacy and long term complications e.g. dyskinesias. Additionally, such therapeutic approaches only treat the clinical symptoms of PD and due not protect the neurons against degeneration hence the disease continues to progress with the patient experiencing increasing disability. Hence there is a chronic need for the development of neuroprotective drugs which prevent further neuronal loss and thus prevent the progression of the disease.

RATIONALE FOR CURRENT STUDY Hypothesis: Increased iron and oxidative stress play a major role in the neurodegenerative process in PD and iron chelation therapy can be effective in removing excess iron from the brain and potentially slowing the neurodegenerative process.

Research question: Can iron chelation therapy with Deferiprone remove excess iron in the substantia nigra in PD patients without toxic side effects. What effect does Deferiprone therapy have on the severity of PD and other brain function e.g. cognition, depression etc.

Increased iron levels have been heavily implicated in the neurodegenerative process in PD. Although many of our cellular processes require iron, when in excessive amounts it can trigger the formation of toxic chemicals called free radicals, of which there is extensive evidence of their increased formation in the PD brain. Hence removal of excess iron by iron chelation (drugs which bind and detoxify iron) represents a potential drug target.

Iron chelators e.g. Deferiprone in doses around 100mg/kg/day, are extensively utilised to treat peripheral iron overload disorders such as beta thalassaemia, where the patients requires regular blood transfusions but iron accumulates in the body when the red blood cells are removed from the circulation. Iron chelation therapy in such patients is associated with minimal side effects with long term use. Recently, in animal models of brain iron overload, we have demonstrated iron chelators can enter the brain removing excess iron. Additionally, we have recently shown that iron chelation therapy protects neurons against toxins in animal models of PD.