Cell Pathways' Exisulind Continues to Slow PSA Rise in Men At High Risk of Prostate Cancer Recurrence.

Business Editors & Health/Medical Writers

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HORSHAM, Pa.--(BW HealthWire)--May 28, 2002

Results of 12-Month Clinical Extension Study Presented at

American Urological Association Meeting

Results of a 12-month open-label extension study of Cell Pathways, Inc.'s (Nasdaq:CLPA) investigational drug exisulind (Aptosyn(R)), in men at high risk of prostate cancer recurrence, continue to show significant benefit for slowing the rise of prostate specific antigen (PSA). In addition, the long-term use of exisulind (up to 24 months) was generally well tolerated by most patients, with the drug demonstrating a safety profile consistent with that reported by investigators in May 2000 for the initial one-year double-blind, placebo-controlled Phase II/III trial of exisulind in prostate cancer.

Data from the extension study, led by Erik T. Goluboff, M.D. of the Columbia Presbyterian Medical Center of New York-Presbyterian Hospital and Diane Prager, M.D. of the UCLA Medical Center, was the subject of a podium presentation by Dr. Goluboff at the American Urological Association meeting in Orlando, Florida.

A rising PSA level is widely accepted by the medical community as a marker of disease progression in men who have had their prostate removed following a diagnosis of prostate cancer, and is used by many physicians to determine treatment. An increase in PSA doubling time suggests a delay in disease progression, consequently delaying the need for hormone deprivation therapies. Results of the original one-year, double-blind, placebo-controlled study showed an increase in median PSA doubling time from 5.6 to 8.8 months in high-risk patients receiving exisulind and a decrease from 4.9 to 2.4 months in high-risk patients receiving placebo.

Sixty men who participated in the original placebo-controlled trial enrolled in the 12-month open-label extension trial of single-agent, oral exisulind. The two study groups for the open-label trial consisted of patients who crossed over from placebo to exisulind (PE group) and those who continued on exisulind therapy (EE group). The investigators evaluated the patients' PSA levels monthly. The results were analyzed for the overall groups and for prospectively determined risk groups (i.e. low, intermediate, high) for recurrence of metastatic disease.

Forty three (71%) of the men completed 12 months of the extension study, receiving doses of exisulind ranging from 300 to 600 mg/day based on their tolerance of the drug. Median PSA doubling time increased from 5.6 months, prior to entry into the one-year, double-blind, placebo-controlled study, to 12.6 months in the extension study at 24 months in the patients at high risk for recurrence in the EEtreatment group (p=0.041). No significant changes were observed in other risk classifications within the EE treatment group. However, PSA doubling times were generally prolonged, with trends toward significance for intermediate risk EE patients (13.3 to 19.6 months; p=0.067) and for patients overall in the PE treatment group (14.7 to 26.9 months; p=0.094). Frequent adverse events included weakness, abdominal pain, diarrhea and reversible rises in liver enzymes, with most adverse events being mild in severity and manageable with adjustments in exisulind dosing.

"These results suggest that exisulind as a single-agent is capable of prolonging PSA doubling time over 24 months, with manageable toxicity in patients at high risk of prostate cancer progression," said Dr. Goluboff. "Moreover, we observed that men in both PE and EE groups who had short pre-study PSA doubling times (less than 10 months), regardless of their risk group ranking, responded well to exisulind."

"We are very encouraged by these results, which continue to support the value of our selective apoptotic antineoplastic drugs (SAANDs) as potential treatments for prostate cancer," said Rifat Pamukcu, M.D., Cell Pathways chief scientific officer. "Dr. Celestia Higano at the University of Washington is conducting a Phase II study of exisulind in patients with prostate cancer who are being treated with intermittent androgen suppression. This study is investigating whether exisulind can extend the 'off-treatment' period of androgen therapy. We are also evaluating our second-generation SAAND, CP461, in patients with hormone-refractory prostate cancer. It is our hope that CP461, which as previously reported has a dual mechanism of action, may provide clinical benefit as a single-agent therapy in this patient population."

About Exisulind (Aptosyn(R)) and other SAANDs

Exisulind represents a first-generation compound in a family of drugs discovered and developed by Cell Pathways, Inc. called selective apoptotic antineoplastic drugs (SAANDs). SAANDs selectively trigger apoptosis in cancerous and precancerous cells by inhibiting certain cyclic GMP phosphodiesterases that company scientists and collaborators have shown to be over-expressed in a variety of tumor types. This cGMP PDE inhibition leads to activation of another intracellular signaling molecule, protein kinase G (PKG), triggering a cascade of downstream events leading to apoptosis.

Cell Pathways is currently conducting a Phase III human clinical study of Aptosyn(R) (exisulind) in advanced non-small cell lung cancer, in combination with Taxotere(R). CP461, a second-generation SAAND with a dual mechanism of action, is currently under study as a single-agent for the potential treatment of chronic lymphocytic leukemia, hormone-refractory prostate cancer, and advanced kidney cancer.

About Cell Pathways

Cell Pathways, Inc., headquartered in Horsham, Pennsylvania, is a development stage pharmaceutical company focused on the research and development of novel and unique medications to treat and prevent cancer and to treat certain inflammatory diseases. The company additionally markets and sells oncology-related products made by others. The company's initial drug candidates in clinical development are Aptosyn(R) (exisulind) and CP461. For additional information on Cell Pathways, Inc., visit the Company's web site at http://www.cellpathways.com.

Editors Note: Aptosyn(R)is a registered trademark of Cell Pathways, Inc. and Taxotere(R)is a registered trademark of Aventis Pharmaceuticals, Inc.

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