Axonyx Reports Data on Stabilized Brain Volumes in Alzheimer's Disease Patients Treated with Phenserine; Analysis of Brain Scan

Axonyx Inc. (NASDAQ: AXYX) today reported an analysis of
results suggesting stabilization of total brain volume and brain
parenchymal fraction of mild-to-moderate Alzheimer's disease (AD)
patients treated with Phenserine 10mg or 15mg twice daily (BID) for
26-weeks. The data will be presented in their entirety as a poster in
Geneva on Thursday, April 20, 2006 at the 9th International
Geneva/Springfield Symposium on Advances in Alzheimer Therapy.
   A sub-study, using Magnetic Resonance Imaging (MRI), examined the
effects of Phenserine treatment on the brains of 16 AD patients
(Phenserine 15mg BID, 8 patients; Phenserine 10mg BID, 7 patients; and
placebo, 1 patient). The primary aim of this sub-study was to
investigate the potential effect of Phenserine treatment on the volume
of different anatomical regions of the brain (brain parenchymal
fraction, whole brain and the hippocampus). These patients were part
of an earlier reported Phase III, 26-week, double blind,
placebo-controlled clinical trial that recruited 377 patients. This
sub-study was recently completed to provide further data to potential
licensing partners for Phenserine.
   Following Phenserine treatment, patients' mean total brain volume
and parenchymal fraction remained stable from baseline but decreased
in the one placebo patient. Mean changes in brain volume were +0.99%
(Phenserine 15mg BID), +2.68% (Phenserine 10mg BID) and -5.15%
(placebo) and mean parenchymal fraction changed from baseline by
+0.21%, +0.46% and -2.97% respectively. Although not statistically
significant, the mean percentage changes of brain volumes seen in the
treated groups suggests a preservation of volume compared with the
brain atrophy (loss of brain volume) seen in the placebo patient.
There was no notable effect in the hippocampal area of the brain;
however this may have been due to the difficulty associated with
measurements of this small brain structure.
   It is well known that Alzheimer's disease is associated with an
acceleration of brain atrophy that is generally greater than expected
for non-demented persons of similar age. Brain atrophy as measured by
MRI has emerged as a potential outcome measure of AD treatments and
marker of disease severity and progression. The possible
neuro-protection seen in this sub-study may potentially reflect the
effects of Phenserine on amyloid beta (A beta) - a protein thought to
be a potential cause of Alzheimer's disease and its progression.
Phenserine's effects are associated with reductions of A beta levels
in pre-clinical studies, as well as a correlation seen between
Phenserine levels and a reduction of plasma A beta in
Phenserine-treated human volunteers. While the signal from this
sub-study of a potential effect of Phenserine on the brains of AD
patients is encouraging, the Company notes that MRI brain studies are
generally of longer duration and include more patients, particularly
in the placebo group. Nevertheless, the absence of brain atrophy in
Phenserine treated AD patients in this sub-study is contrary to what
would be expected to occur and may justify a definitive MRI evaluation
of the effects of Phenserine on brain atrophy in patients with
Alzheimer's disease.

   About Phenserine

   Phenserine is a highly selective inhibitor of acetylcholinesterase
(AchE-I), an enzyme that breaks down the neurotransmitter
acetylcholine, a neurotransmitter important to memory and cognitive
function. Unlike other AchE-I's, which only suppress the activity of
the enzyme, Phenserine has been shown to have two mechanisms of
action: (1) the inhibition of the AChE enzyme, and (2) inhibition of
the synthesis of A beta - a protein thought to be a potential cause of
Alzheimer's disease and its progression.

   About Axonyx

   Axonyx Inc. is a U.S.-based biopharmaceutical company engaged in
the acquisition and development of proprietary pharmaceutical
compounds for the treatment of Central Nervous System disorders. The
Company currently has three compounds in development for Alzheimer's
disease; Phenserine - a potential symptomatic and disease progression
treatment of mild to moderate Alzheimer's Disease (AD); Posiphen(TM) -
a potential disease progression treatment for AD now in Phase I; and
BisNorCymcerine (BNC) - a potential symptomatic treatment of severe AD
in the pre-Investigational New Drug (IND) stage.

   This press release may contain forward-looking statements or
predictions. These statements represent our judgment to date, and are
subject to risks and uncertainties that could materially affect the
Company, including those risks and uncertainties described in the
documents Axonyx files from time to time with the SEC, specifically
Axonyx's annual report on Form 10-K. Specifically, with respect to our
drug candidates Phenserine, Posiphen(TM) and BisNorCymserine, Axonyx
cannot assure that: any preclinical studies or clinical trials,
whether ongoing or conducted in the future, will prove successful, and
if successful, that the results can be replicated; safety and efficacy
profiles of any of its drug candidates will be established, or if
established, will remain the same, be better or worse in future
clinical trials, if any; pre-clinical results related to cognition and
the regulation of beta-APP and/or amyloid beta will be substantiated
by ongoing or future clinical trials, if any, or that any of its drug
candidates will be able to improve the signs or symptoms of their
respective clinical indication or slow the progression of Alzheimer's
disease; any of its drug candidates will support an NDA filing, will
be approved by the FDA or its equivalent, or if approved, will prove
competitive in the market; Axonyx will be able to successfully
out-license any of its drug candidates; Axonyx will be able to
successfully in-license any additional compounds; or that Axonyx will
have or obtain the necessary financing to support its drug development
programs. Axonyx cannot assure that it will be successful with regard
to identifying a (sub-) licensing partner for any of its compounds.
Axonyx undertakes no obligation to publicly release the result of any
revisions to such forward-looking statements that may be made to
reflect events or circumstances after the date hereof or to reflect
the occurrence of unanticipated events.