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Gene therapy promising in Parkinson's patients

10 January 2014
Appeared in BioNews 737

Patients in a clinical trial to treat Parkinson's disease with a form of gene therapy have showed signs of significant improvements in their motor-function, according to a report published in the Lancet.

Fifteen advanced-stage Parkinson's patients (three from the UK and 12 from France) were followed up a year after being injected with low, mid and high doses of a modified virus containing genes required for brain cells to produce dopamine, as part of the phase I/II study. A lack of dopamine causes patients with Parkinson's to experience tremors and difficulty in coordinating their movement.

The researchers observed that after receiving the treatment the patients' scores on movement tests improved on average by 30 percent. The patients also reported having a better quality of life. Although the patients showed some side effects, overall the treatment was found to be safe and no serious side effects were observed.

Professor Stéphane Palfi, from the University of Paris and the lead author of the study, wrote that '[The treatment] was safe and well tolerated in patients with advanced Parkinson's disease', adding that, 'Improvement in motor behaviour was observed in all patients'. The researchers said scans have shown that dopamine was being produced in the patients where it wasn't before.

The treatment, called ProSavin, is a type of gene therapy and was developed by scientists working at Oxford BioMedica. Unlike more conventional therapies that involve taking a regime of pills to increase dopamine in the brain, ProSavin aims to offer a long-term treatment solution by getting brain cells to make their own dopamine. The modified virus transports three genes that code for a dopamine-producing enzyme into a part of the brain that controls movement.

Dr Kyriacos Mitrophanous, head of research at Oxford BioMedica, wrote in an email to Medical Daily that: 'This is the first gene therapy approach that delivers the three key enzymes in one vector required to convert cells in the brain to manufacture dopamine, the neurotransmitter that is depleted in Parkinson’s disease'. He added that, 'The long-lasting benefits we have seen to date give us great hope for this product and the underlying technology'.'

ProSavin was tested in only a small number of patients at this stage and the study lacked a placebo only control group to rule out a placebo effect. The absence of a placebo group means the results should be treated with caution, states a press release from Imperial College London. Further studies are required to demonstrate that it is more effective than current treatments and that the benefits are not due to the placebo effect.

Professor Nicholas Mazarakis, from Imperial College London and an author on the study, said: 'I'm very pleased that [ProSavin] has appeared to work in the clinic'.

He added: 'It has the potential to move to the next phase. It needs to be done in more people; we have to find the most effective dose, to further increase efficacy, and prove beyond doubt that this is not a placebo effect'.

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