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Several recent reports on ongoing clinical trials for gene therapies indicate that even preliminary studies with only a handful of patients can yield results with the potential to alter the course of the entire field. So after each description below, I offer a DNA Science lesson learned assessment: why the study is important.

INTO THE BRAIN PARKINSONS DISEASE

Gene therapy typically delivers a functioning version of a gene to cells needing it. Investigators Stphane Palfi MD of AP-HP, Groupe Henri-Mondor Albert-Chenevier in Crteil, France and Roger Barker, PhD, at Addenbrookes Hospital in Cambridge, UK, have expanded the reach of gene therapy by delivering the trio of genes whose encoded proteins enable cells to make dopamine, the neurotransmitter thats depleted as Parkinsons disease (PD) progresses. Preliminary results on the gene therapy appear inThe Lancet.Oxford Biomedica, a company developing gene-based medicines, is funding the trial of the triplo-gene therapy for Parkinsons, called ProSavin.

Gene therapy enables cells of the striatum to use the 3 genes that make dopamine.

In a healthy brain, neurons in the substantia nigra make dopamine. Their axons project to the striatum, where they release the neurotransmitter so neurons there can sop it up. Three enzymes control dopamine synthesis: two convert the amino acid tyrosine to levodopa, and a third converts the levodopa to dopamine.

Treating PD is an ever-changing question of balance. Oral levodopa can offset the dopamine deficit, but after a few years, motor symptoms develop. These include uncontrollable movements (tardive dyskinesia) and on-off phenomena, which are periods of improved mobility interspersed with periods of impairment, sometimes severe.

Where there are missing enzymes, gene therapy is an option, and several have been tried for Parkinsons disease. The safest gene therapy vector (a disabled virus that delivers the gene), adeno-associate virus (AAV), cant carry a very large payload, only one smallish gene at a time. So the researchers turned to a larger vehicle to deliver the trio of genes, the lentivirus that causes swamp fever in horses, equine infectious anemia (EIA) virus. Many gene therapy experiments use a more familiar lentivirus HIV.

A horse virus delivers Parkinsons gene therapy.

Excerpt from:
Gene Therapy News: Brain, Skin, Eye - DNA Science Blog

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