New Gene Therapy Trial for Parkinson's Disease

Oxford Biomedica is planning a gene therapy trial for parkinson's patients. In this trial, researchers will introduce a virus (Lentivector) that will deliver a total of three different genes. These genes encode for three seperate enzymes (tyrosine hydroxylase, GTP-cyclohydrolase 1 and aromatic amino acid decarboxylase) that are involved in the synthesis of the neurotransmitter dopamine. In parkinson's disease, neurons that produce dopamine in an area of the brain called the substantia nigra slowly die off. Parkinson's patients thus have a deficiency of dopamine leading to the symptoms of parkinson's disease such as muscle rigidity, tremor and a slowing of physical movement.

Another successful gene therapy trial had already taken place in the past. In that trial, parkinson's patients had a gene encoding for a protein called glutamic acid decarboxylase (GAD) introduced into their brain via a virus. This specific enzyme synthesizes the neurotransmitter GABA. By increasing GABA in a brain area called the subthalamic nucleus, researchers we're able to reduce specific parkinson's symptoms like uncontrollable tremor. However, GABA deficiency is only a downstream effect of the dopamine deficiency. Increasing GABA in that area of the brain does not get to the source of the problem in parkinson's patients, which is lack of dopamine. So this new trial gets to the source of the problem and may lead to a more robust and long lasting improvement for treatment resistant parkinson's patients. In the future, gene therapy may be used for a variety of other brain based disorders.