Detailed Results of Cell Pathways' Study of Exisulind in the Treatment of Sporadic Adenomatous Colon Polyps Presented at Meeting of the American Gastroenterology Association.

Business Editors & Health/Medical Writers

BIOWIRE2K

HORSHAM, Pa.--(BW HealthWire)--May 22, 2002

Daily treatment with 400 mg of exisulind (Aptosyn(R)) significantly reduced the size of precancerous adenomatous colon polyps and prevented further polyp growth compared to placebo in a study of Cell Pathways, Inc.'s (Nasdaq:CLPA) investigational drug. Detailed results of the randomized, double-blind, placebo-controlled trial were reported today by principal investigator Nadir Arber, M.D., of Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel, at the American Gastroenterology Association meeting.

"Previous clinical studies with exisulind showed this investigational drug's ability to reduce the formation of precancerous colon polyps in patients with familial adenomatous polyposis (FAP) by 25% after 12 months of treatment and by an additional 54% at 24 months," said Dr. Arber. "Since the precancerous, adenomatous polyps formed sporadically by individuals at known risk of colon cancer are histologically and genetically similar to FAP polyps, we studied the efficacy and safety of exisulind in stimulating the regression of these polyps."

In a double-blind trial conducted at 24 multinational sites, patients with at least one sporadic colon polyp of 4-10 mm diameter were randomized to receive either exisulind at 200 mg/day or 400 mg/day, or placebo. Patients received a baseline colonoscopy, during which an existing polyp was tattooed and its dimensions measured. At months six and 12 of the study, the marked polyps were again measured, and then surgically removed at the 12-month visit.

Of 281 patients enrolled in the study, 125 patients with hyperplastic polyps (a form of colonic polyp known not to develop into cancer) and one patient who consented but withdrew before starting treatment were excluded from the efficacy analysis per the study protocol. Of the 155 patients who met the "intention-to-treat" requirements of one or more adenomatous polyps and one or more doses of study medication, 114 patients (74%) completed a full year of therapy and were thus evaluable for efficacy.

Investigators reported that 33 of the efficacy evaluable patients treated with exisulind 400 mg/day experienced a median shrinkage in their measured polyp of approximately 10 mm squared, a 50% reduction in polyp size. This polyp shrinkage was significantly greater (p=0.03) than the shrinkage experienced by either the 43 patients receiving placebo (-4 mm squared or 25% change from baseline) or the 38 patients receiving 200 mg/day exisulind (-4 mm squared or 20% change from baseline).

The number of patients in the 400 mg exisulind group achieving either a complete or partial therapeutic response (greater than 50% reduction in polyp size) was significantly higher (p=0.038) than in the placebo or 200 mg exisulind groups. Eighteen or 54.6% of patients in the 400 mg group responded to treatment, versus 30.2% or 13 patients in the placebo group and 34.2% or 13 patients in the 200 mg exisulind group. At the same time, the number of patients in the 400 mg exisulind group whose disease progressed was significantly lower (6.1%, p=0.017) than for either the placebo (27.9%) or 200 mg exisulind (21.1%) groups.

Treatment with exisulind was generally well tolerated by most patients, with drug-related adverse events including abdominal pain, mild, reversible liver enzyme elevations, and biliary events.

"Exisulind given at 400 mg/day was clearly superior to placebo in inducing regression and preventing the further growth of sporadic colon adenomas," concluded Dr. Arber. "Based on these results, we believe this drug clearly merits further investigation as a possible treatment to prevent precancerous colon polyps in people known to be significantly at risk for developing colon cancer."

"The results of this study continue to support clinical proof-of-principle for exisulind, a cyclic GMP phosphodiesterase inhibitor, in the prevention of growth of precancerous adenomatous polyps of the colon," said Rifat Pamukcu, MD, chief scientific officer of Cell Pathways, Inc. "Recent public guidance from an FDA advisory panel, as well as our own discussions with the agency, suggests that demonstrating a drug's ability to benefit those at risk of colon cancer due to sporadic polyps would require a study of at least five years duration, involving up to several thousand patients."

"Based on this input, we have concluded that a polyp prevention trial of this sort is too large and costly for a company of Cell Pathways' size to achieve on its own," he continued. "However, Cell Pathways would be very pleased to collaborate with others, such as a strategic partner or the National Institute of Health (NIH), to study exisulind or our other selective apoptotic antineoplastic drugs (SAANDs) in this indication."

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.

The company is currently studying exisulind (Aptosyn(R)) in combination with Taxotere(R) in a Phase III registration-directed trial in patients with advanced non-small cell lung cancer, with a clinical endpoint of one-year and overall survival. Studies of exisulind in combination with other chemotherapeutic agents are also planned or underway in a variety of indications, both under the company's sponsorship and under the sponsorship of others.

In addition to the company's studies with exisulind, the company is investigating CP461, a more potent, second-generation SAAND, 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, Pa., is a development stage pharmaceutical company focused on the research and development of novel and unique medications to treat and prevent cancer, the commercialization of these compounds and the marketing and selling of oncology-related products manufactured 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.

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, 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: early stage of development; the costs, delays and uncertainties inherent in scientific research, basic pharmaceutical research, drug development, clinical trials and the regulatory approval process, with respect to both our current product candidates and our future product candidates, if any; limitations on, or absence of, the predictive value of data obtained in laboratory tests, animal models and human clinical trials when planning additional steps in product development; uncertainty that additional studies, if any, may not be positive; uncertainty of obtaining regulatory approval of any compound for any disease indication whether due to adequacy of the development program, changing regulatory requirements or otherwise; the absence of approved products; history of operating losses and the need for further financing; dependence on the development, regulatory approval and market acceptance of one or more of our product candidates for one or more significant disease indications; the risk that the Company does not conduct the clinical studies it may have planned to conduct or does not pursue development plans it may have planned to pursue; the risk that clinical studies do not result in the safety and efficacy necessary to obtain regulatory approvals; the risks of conducting clinical trials, including the risk of conducting clinical trials of our drugs in combination with other drug therapies; the commercial risk and risk of liability in marketing and selling Gelclair(TM) Concentrated Oral Gel; and providing marketing services promoting Nilandron(R) (nilutamide) manufactured by Aventis Pharmaceuticals, Inc.; the risk that the Company may enter into, or may fail to enter into, licensing, partnership or collaborative arrangements or strategic alliances which accord to other companies rights with respect to one or more Company compounds, technologies or programs or in which the Company acquires new rights and obligations; the volatility of the market price of our Common Stock; our ability to sell securities registered under the shelf registration statement; acceptance of any product candidates by physicians and providers of healthcare reimbursement; the actions of competitors; the pace of technological changes in the biopharmaceutical industry; dependence upon third parties; the validity, scope and enforceability of patents; the risk of pending or future class action securities litigation; potential product liability claims; and availability and adequacy of insurance. These and other risks are detailed in our reports filed from time to time under the Securities Act and/or the Securities Exchange Act, including the sections entitled "Business," "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Other Events" in our annual reports on Form 10-K, quarterly reports on Form 10-Q and periodic reports on Form 8-K and in such registration statements on Form S-3 as we may file from time to time. You are encouraged to read these filings as they are made. They are available over the Internet from the SEC in its EDGAR database at http://www.sec.gov and from the Company. Given the uncertainties affecting pharmaceutical companies in the development stage, you are cautioned not to place undue reliance on any such forward-looking statements, any of which may turn out to be wrong due to inaccurate assumptions, unknown risks, uncertainties or other factors. No forward-looking statement can be guaranteed; actual future results may vary materially. Both forward-looking statements and statements of historic fact must be understood in the context of the risks referred to above which characterize our development stage business. We undertake no obligation to update or revise the statements made herein or the risk factors that may relate thereto.