Print

---

I read with considerable interest the announcement from Cell Genesys
"Cell Genesys Reports Encouraging Results in Preclinical Studies of
Parkinson's Disease Gene Therapy", "Single Gene Therapy Treatment
Eliminates the Need for Daily L-dopa Treatment" as reported by
www.PRSNewswire.com.  I believe that the focus on PD in the report
invites misinterpretation, and that the method of gene therapy
method described in the report has no application to idiopatic PD in
humans.

As I read the report, the mice in the study were first rendered
genetically unable to produce dopamine. "The mouse model used in
this study was created in Dr. Palmiter's laboratory using
gene-targeting techniques. The genetically modified mice are unable
to make tyrosine hydroxylase, a critical enzyme for dopamine
synthesis in the brain."

This seems to be quite a different condition than PD, in which we
have a dopamine deficency owing to the destruction of dopamine
-producing cells.

Then genes were transported by specially developed viruses to the
striatum, where they caused cells which did not produce dopamine to
begin doing so. "An adeno-associated viral (AAV) gene delivery
system was used to deliver the genes required for the production of
L-dopa to specific regions of the brain where L-dopa production could
be detected throughout the observation period."

Weren't these the same cells in which dopamine production was turned
off?

There could be no analogous treatment for PD in humans, since the
mice did not have real PD, and the corresponding cells which were
caused to begin producing dopamine in the mice would have been
destroyed by PD in humans.

The real purpose of the experiment appears to be to provide an
illustration of how a genetic defect might be corrected. "... stated
Mitchell H. Finer, Ph.D., vice president, research at Cell
Genesys..[:] "These studies are among the first observation that gene
therapy with AAV vectors can be used to correct a genetic defect in
specific regions of the brain."

This is different from creating a way to treat PD.

Phil Tompkins
Hoboken NJ
age 61/dx 1990