Cell Pathways Announces Positive Results of Clinical Trial Investigating Aptosyn -- Exisulind -- in the Treatment of Sporadic Adenomatous Polyps of the Colon.

Business Editors/Health & Medical Writers

HORSHAM, Pa.--(BW HealthWire)--Aug. 27, 2001

Cell Pathways, Inc. (Nasdaq:CLPA) today announced the preliminary results of a double-blind, placebo-controlled clinical study of Aptosyn(TM) (exisulind) in the treatment of precancerous sporadic adenomatous polyps of the colon. The multi-national study, involving 114 adenomatous polyp patients who completed the full year of study at centers in the United States, Sweden and Israel, demonstrated that exisulind caused the regression of pre-existing adenomatous colon polyps and reduced their further growth in treated patients.

Investigators enrolled patients into the trial after identifying the presence of at least one polyp ranging from 4 mm to 10 mm within the sigmoid colon or rectum during colonoscopy. Experts estimate that approximately 50-60% of colon polyps are precancerous adenomatous polyps, while the remaining polyps are hyperplastic. Hyperplastic polyps are generally considered to be benign and to lack the potential to transform into cancer.

Since baseline biopsy of the polyps could not be performed without potentially altering the growth of the polyp, 281 patients were enrolled to ensure that an adequate number of patients with adenomatous polyps would be available for statistical analysis. Investigators placed tattoos near the index colonic polyps during the baseline colonoscopy, and the patients were randomized to placebo, exisulind 100 mg given twice daily (bid), or exisulind 200 mg bid (overall 186 patients received exisulind). Patients received a flexible sigmoidoscopy at 6 months and another colonoscopy upon exit from the study. Polyps remaining at the end of the study were removed and analyzed to determine whether they were adenomatous or hyperplastic. The 126 patients with hyperplastic polyps were excluded from all analyses of the effects of exisulind on adenomatous polyps.

Of the 155 adenomatous polyp patients entering the study, 41 discontinued prior to completion of the required one-year of therapy, 12 for adverse events (two patients in the placebo group and five patients in each exisulind group). The remaining 114 patients fulfilled the three prospectively defined criteria to be deemed evaluable: they completed the full year of the study, they completed three colonic endoscopies (baseline, six-month and study termination) and their remaining polyps were not hyperplastic.

The efficacy measurements for the evaluable patients in this one-year, single-agent study included: 1) the difference in the median change in adenomatous polyp size from baseline between the placebo-treated and exisulind-treated groups, 2) the number of patients that demonstrated a complete or partial response (a equal to/greater than 50% reduction in size of the index polyp) to treatment, and 3) the progression of disease (equal to/greater than 25% increase in size of the index polyp).

The results of analyses of all three of these efficacy parameters in patients on exisulind 200 mg bid showed improvement and were statistically significant compared to patients on placebo. The average polyp size was reduced by 35% on exisulind 200 mg bid, while patients on placebo demonstrated a 5% increase in polyp size. Exisulind 100 mg bid results were not different from placebo. Exisulind was generally well tolerated by the 186 patients treated with exisulind during the study. Consistent with previous studies, adverse events observed in the exisulind-treated patients included dyspepsia and reversible liver enzyme elevations, (both were lower in frequency than in the previously reported prostate cancer trial of exisulind), and abdominal pain, occasionally severe.

"I am pleased with these positive preliminary findings and look forward to the detailed presentations of the data from this trial in future scientific forums and peer-reviewed journals," commented Rifat Pamukcu, M.D., chief scientific officer of Cell Pathways, Inc. "These results, combined with the abundance of positive cell culture, animal and clinical studies, continue to support our SAANDs technology. We are encouraged to continue to advance our compounds through registration-directed studies in various cancer indications, both as a single agent and in combination with leading chemotherapeutic drugs."

Dr. Pamukcu continued, "While these results are scientifically promising, registration-directed trials in the sporadic adenomatous polyp indication would require the enrollment of a thousand or more patients and take many years to conduct. Also, these results should not be viewed as direct support for the product registration effort in familial adenomatous polyposis (FAP), an effort that would likely require additional clinical studies in FAP patients without guarantee of success in the registration effort. Our SAANDs clinical development program is currently focused on registration-directed trials in cancer indications -- where we believe we can more effectively and efficiently advance the company's compounds towards commercialization."

About Exisulind (Aptosyn(TM)) and other SAANDs

Exisulind (Aptosyn(TM)) is the first member of a new class of compounds called SAANDs (selective apoptotic antineoplastic drugs) that selectively trigger programmed cell death, or apoptosis, in precancerous and cancerous cells but not normal cells. Research by Cell Pathways and others has demonstrated that these drugs achieve their pro-apoptotic effect by inhibiting specific cyclic GMP phosphodiesterases, thus allowing death of the abnormal cells to occur through apoptosis. Both exisulind and a second-generation SAAND compound, CP461, are in human clinical development as potential treatments for a variety of cancers.

Cell Pathways, Inc. headquartered in Horsham, Pa., is a development stage pharmaceutical company focused on the research, development and commercialization of novel and unique medications to prevent and treat cancer. For additional information on Cell Pathways, Inc., visit the Company's web site at http://www.cellpathways.com.

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