Cell Pathways Initiates New Prostate Cancer Studies With Exisulind.

HORSHAM, Penn.--(BW HealthWire)--June 3, 1999--

Cell Pathways, Inc. (NASDAQ:CLPA) today announced that the company has started two additional Phase II clinical studies of the safety and efficacy of its lead investigational drug exisulind in prostate cancer.

The first study is a 12-month, open-label evaluation of exisulind in 15 post-prostatectomy patients who are receiving LHRH-agonist hormone therapy and whose PSA levels are rising. Investigators will determine the patients' PSA levels at monthly intervals and will check for disease progression or the appearance of metastatic lesions by various x-ray scans and other tests.

"Based on the encouraging results from the interim analysis of our ongoing Phase II/III study of exisulind in post-prostatectomy patients, we have initiated this additional study in men with more advanced disease," said Rifat Pamukcu, M.D., chief scientific officer of Cell Pathways.

The second trial is an open-label evaluation of the influence of exisulind on the rate of apoptosis (programmed cell death) and the expression of cyclic GMP-PDE (cGMP-PDE) in pre-malignant and malignant prostate tissue compared to normal prostate tissue. This study will enroll a total of 20 men who have histologically confirmed prostate cancer and are scheduled for a radical prostatectomy within two to eight weeks of diagnosis. Participants in the study will receive 500 mg exisulind for periods of two, four, six or eight weeks prior to surgery, starting at diagnosis. Investigators will evaluate the resected prostate tissue for apoptosis rates in premalignant, malignant and normal cells, and will measure the amount and expression of cGMP-PDE.

"This second study will help us directly evaluate the effect of exisulind on premalignant and malignant prostate cells, and will provide insight for the design of future studies of exisulind in the prevention or treatment of prostate cancer," said Dr. Pamukcu.

On May 6, 1999, Cell Pathways reported results from a planned, third-party interim analysis of the company's ongoing Phase II/III clinical trial of exisulind in patients with detectable PSA levels that were rising following radical prostatectomy. Among other things, the interim review reported a statistically significant difference in the mean rise in PSA levels between drug and placebo groups. Cell Pathways expects to complete this one year trial late in the third quarter of 1999, after which it will evaluate the results of the entire study on a detailed basis.

Exisulind represents the first of a novel class of potential therapeutic agents, called selective apoptotic anti-neoplastic drugs (SAANDs), that target a novel form of cyclic GMP phosphodiesterase (cGMP-PDE). Cell Pathways scientists believe that this enzyme, whose production appears to be selectively increased in precancerous and cancerous cells, interferes with the abnormal cells' ability to process the message telling them to die by apoptosis. By specifically inhibiting the action of the novel cGMP-PDE, exisulind and other SAANDs enable abnormal cells to process an apoptotic signal and commit suicide without affecting normal cells. Cell Pathways is currently conducting human clinical studies of exisulind in a variety of indications for the prevention or treatment of cancer, and recently began human safety studies with a second SAAND, CP461.

Cell Pathways, Inc., headquartered in Horsham, Pennsylvania, is a pharmaceutical company focused on the research, development and commercialization of products to prevent and treat cancer.

Note to Editors: Certain Statements made herein, and oral statements made in respect hereof, constitute "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements are those which express plan, anticipation, intent, estimation, belief, contingency or future development and/or otherwise are not statements of historical fact. These statements are subject to risks and uncertainties, known and unknown, which could cause actual results and developments to differ materially from those expressed or implied in such statements. Such risks and uncertainties relate to, among other factors, the costs, delays and uncertainties inherent in basic pharmaceutical research, drug development and clinical trials; the uncertainty of obtaining regulatory approval, and the timing and scope of any approval received; acceptance by providers of healthcare reimbursement; the validity, scope and enforceability of patents; the actions of competitors; dependence upon third parties; product liability; and other risks detailed in the Company's reports filed under the Securities and Exchange Act of 1934, including the sections entitled "Business" and "Risk Factors" in the Company's report on Form 10-K for the year ended December 31, 1998. The Company undertakes no obligation to update or revise the statements made herein.