VY-AADC is a gene therapy for Parkinson’s disease that is being developed by Voyager Therapeutics. The treatment is aimed at increasing the patient’s ability to produce dopamine, a signaling molecule that helps regulate movement and emotional responses, which improves motor function and reduces the need for other Parkinson’s disease medications.

How VY-AADC works 

Parkinson’s disease is caused by the dysfunction or death of dopamine-producing neurons in an area of the brain called the substantia nigra. This brain region is involved in controlling movement and balance. Scientists do not know yet what causes the impairment or death of these neurons, but they know the loss of the dopamine they produce leads to the motor and cognitive symptoms associated with Parkinson’s.

Parkinson’s disease patients are commonly treated with a medication called levodopa. The active ingredient of levodopa is a chemical precursor of dopamine. This means that enzymes inside brain cells convert levodopa into dopamine. This helps boost patients’ dopamine levels and alleviate symptoms of the disease.

However, as Parkinson’s progresses, levodopa often becomes less effective for patients. Scientists think this may be because, as the disease progresses, patients also produce less of an enzyme called 1-amino acid decarboxylase (AADC). This is the enzyme that converts levodopa to dopamine. If patients do not produce enough AADC, they will be unable to convert enough levodopa into dopamine for the medication to be effective.

VY-AADC is a gene therapy. Gene therapy uses a vector, typically a virus, to introduce genetic material into patients’ cells. Viruses often are used because they are very effective in injecting their own genetic material into cells. The viruses used in gene therapy are modified to be harmless and to deliver only the desired genetic material into the cell.

VY-AADC gene therapy introduces the gene encoding for the AADC enzyme into cells in the putamen region of the brain. The putamen region is connected with the substantia nigra, the region that is affected by Parkinson’s, but the neurons in the putamen do not degenerate. Scientists think that if neurons in the putamen can make their own AADC enzyme, they can convert levodopa into dopamine and this should reduce symptoms of the disease.

VY-AACD in clinical trials

VY-AACD has been tested in a Phase 1 clinical trial (NCT01973543) evaluating its safety for the treatment of Parkinson’s. The results of this trial showed that a single administration of VY-AADC was sufficient to increase the activity of the AADC enzyme and the effectiveness of levodopa treatment. Patients also showed improvements in motor function.

Another Phase 1 trial (NCT03065192), currently recruiting participants in the U.S., is evaluating the effectiveness and safety of using an alternate administration technique to deliver VY-ADCC into the brain.

Voyager Therapeutics announced in January 2018 it has received clearance from the U.S. Food and Drug Administration (FDA) to initiate a Phase 2/3 clinical trial of VY-ADCC, which will include larger numbers of Parkinson’s disease patients at multiple sites.

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