Addex completes enrollment of first mid-stage clinical GERD trial

Geneva, Switzerland, 28 September 2009 - Addex Pharmaceuticals
(SWX:ADXN), the allosteric modulation company, announced the
completion of enrollment in the Phase IIb trial of ADX10059 as a
monotherapy in patients with gastroesophageal reflux disease (GERD),
the cause of heartburn and other symptoms. ADX10059 is a
first-in-class reflux inhibitor that works by reducing activation of
the metabotropic glutamate receptor 5 (mGluR5) through negative
allosteric modulation (NAM). This approach may lead to a new class of
drugs that addresses the causes of GERD rather than just the
symptoms. ADX10059 also is in clinical trials to treat GERD patients
who are partial responders to Proton Pump Inhibitors (PPIs) and
separately, as a migraine prophylaxis in patients with frequent
migraines.

Chief Medical Officer Charlotte Keywood said: "We are pleased that
all three Phase IIb trials of ADX10059 are progressing as planned. We
expect to communicate top-line data from study 204 late this year
before presenting more detailed data at a scientific conference next
year."

Study ADX10059-204 is a double-blind, placebo-controlled,
multi-center European Phase IIb trial in 90 GERD patients known to
respond well to proton pump inhibitors (PPIs). There is a two week
baseline symptom evaluation period followed by two weeks of
administration of ADX10059 120 mg twice daily. ADX10059 is used as a
monotherapy so patients in the study do not use PPIs or other acid
suppressant therapy during the baseline and study treatment periods.
The co-primary endpoints are patient reported symptom control
compared to baseline and the effects of ADX10059 on lower esophageal
sphincter (LES) function. Objective measures of the effects of
ADX10059 on LES function and acid reflux events will be made in a
subset of patients using esophageal manometry and pH impedance
monitoring. Data are expected to be communicated in late 2009.

Study ADX10059-205 is a double-blind, placebo-controlled,
multi-center U.S. and European Phase IIb trial in 280 GERD patients
who are partial responders to PPIs. In Study 205 ADX10059 is being
used as an add-on therapy to the patients´ existing PPI treatment.
There will be a baseline symptom evaluation period followed by four
weeks of administration of twice-daily ADX10059 (50mg, 100mg or
150mg). The primary endpoint is patient reported symptom control
compared to baseline. Enrollment is expected to complete in the
fourth quarter and data will be communicated in early 2010 or late
2009.

Study ADX10059-206 is a double-blind, placebo-controlled, dose range