Alzheimer’s gene therapy trial takes another step

Those who take care of someone with Alzheimer’s or follow
developments in the field are well aware that there are no good treatments for
the disease. The handful of drugs that have been approved for use in
patients—such as donepezil, sold under the name Aricept—only
manage symptoms; they do not reverse or even slow the loss of nerve cells that ultimately
leads to death.

Now scientists are testing
a treatment that does show promise for arresting the progression of
Alzheimer’s. Twelve sites around the country are recruiting patients for a
Phase II trial of CERE-110,
a gene therapy treatment. In this approach, doctors perform surgery to implant
a virus into the brain; the virus then inserts new genetic material into nerve
cells that stimulates them to overproduce nerve growth factor (NGF). This
protein promotes nerve growth survival; increased levels of NGF have reversed
nerve cell degeneration in monkeys and rats.

Phase I trials,
conducted over the past five years, have shown that the gene therapy is safe for
people and does not cause side effects such as cancer or immune reactions,
which had occurred in prior gene therapy trials. Because Phase I trials test
primarily for safety, however, information on how well or if the treatment
works is pretty sparse. The Phase II trial will test the effectiveness of the
therapy in a total of 50 people with mild to moderate Alzheimer’s, with half
receiving the treatment and the other half serving as controls by getting
“sham” surgeries. If the trial were successful, the latter group would be
eligible to receive the full treatment.

Directly tackling the
underlying causes of Alzheimer’s has proven extremely difficult. Last year, for
instance, a highly touted and 1,700-subject Phase III trial
of flurizan
, a drug
that targets the amyloid protein clumps that form in Alzheimer’s, failed to
show a significant benefit. Bapineuzumab, an experimental vaccine against
amyloid proteins, showed positive effects
only in a select group of patients
in a recent Phase II trial.

It will be several years before the results of this trial
are reported, but scientists and patients have a good reason for optimism, as this has been a breakthrough year for gene
therapy. Recently researchers restored
color vision
in two color-blind monkeys using gene therapy. Earlier this
month, scientists also announced that they had halted the
progression
of a devastating brain disease,
X-linked
adrenoleukodystrophy, in two young boys.

-Aalok Mehta

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