INTERVIEW WITH DR BARRY SNOW
Dr Snow talks to The Parkinsonian about his ground breaking Clinical Trial In October the Minister of Health announced authorisation had been given for a Phase 1 clinical trial into the safety and clinical effect of pig cell transplants for people with Parkinson’s. The principal investigator of this trial is Dr Barry Snow. He recently spoke to The Parkinsonian about the trial. What is this new treatment? Deep within the brain is a structure known as the choroid plexus, which releases a natural mix of growth factors that make nerves grow. These growth factors can also protect the brain from injury and help repair damage. It is impossible to transplant human choroid plexus cells. However, Auckland Island Pig choroid plexus cells can be transplanted. Earlier research has shown that, once transplanted, the pig choroid plexus releases the right mix of growth factors and can reverse Parkinson’s-like symptoms in animals. Transplanting these pig choroid plexus cells has produced no adverse events, so the next step is to test them in humans.
The capsules are a little like Goretex in that they have perforations that let nutrients in and the growth factors out yet the perforations are too small to allow attack by the immune system. We know that the pig cells can last for years inside these capsules so the effect of this treatment is expected to be long term.
Is it safe to use pig cells? We have used pig tissue for medical treatments for many years, and they are particularly useful for heart valve replacements.
This sort of research is ground breaking. We know that in medical research we need to take major steps such as occurred when people were first given Deep Brain Stimulation for Parkinson’s or when heart patients were first given pig valve replacements. It is hoped that this treatment will be a major step in the treatment of Parkinson’s.
The main concern in transplanting cells from pigs is that the pigs may carry viruses that could be dangerous to humans. For the Parkinson’s study, the pigs will come from a herd that has lived in isolation on the Auckland Islands for over 200 years. The Auckland Islands are south of New Zealand near the Antarctic and the pigs have been tested and found to be free of dangerous viruses. They now live in special isolation near Invercargill and Auckland.
How does this new treatment work?
How do people get involved in the trial?
Nerves attract other nerves to grow towards them by releasing growth factors. In Parkinson’s the dopamine pathway nerves die back in the brain. The cause of this dieback is not known. The result is that the nerves become disconnected, and the person develops the symptoms of Parkinson’s. This new treatment aims to slow or stop the dieback of these nerves by transplanting pig cells that release growth factors.
We will approach patients already accepted for Deep Brain Stimulation surgery and offer the opportunity to have the capsules placed into the brain. We will assess the parkinsonism carefully. If there is no improvement after 6 months, then the person can have the Deep Brain Stimulation surgery they were originally offered.
The treatment involves surgically placing cells producing the growth factors into the brain to encourage the nerves that have died back to regrow. This type of treatment has been tried in humans, but the experiments so far have used only one particular growth factor. This trial will use the mix of multiple growth factors that are released by the part of the brain known as the choroid plexus. One of the problems of transplanting pig choroid plexus into humans is that the human immune system will destroy the foreign pig cells. This can be solved by putting the pig cells into tiny capsules that shield the pig cells from attack by the human immune system.
When will the trial be undertaken? Although the study has been approved by Medsafe and the Minister of Health, the next step is to present it to the Ethics Committee and the Auckland District Health Board Review Committee. Once approved has been gained, we will start the trials in 2013.
Dr Snow is a Neurologist and Medical Director of the Adult Healthcare Service Group, Auckland District Health Board. The team performing the study with Dr Snow are Mr Arnold Bok, Neurosurgeon, Drs David McAuley and Mark Simpson, Neurologists, Lorraine Macdonald, Parkinson’s nurse, Greg Finucane, Neuropsychiatrist and Jamie Macniven, Neuropsychologist. They will work closely with the theatre team for the operation. The encapsulated cells are produced by the NZ company, Living Cell Technology.