Cell Pathways Receives Notice of Allowance for Broad Patent Applying Its Core Technology to the Treatment of Inflammatory Bowel Disease.

Business Editors/Health & Medical Writers

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HORSHAM, Pa.--(BUSINESS WIRE)--Sept. 25, 2002

Cell Pathways, Inc. (Nasdaq:CLPA) today announced it has received a Notice of Allowance from the U.S. Patent and Trademark Office generally covering cyclic GMP phosphodiesterase 2 and 5 inhibition to treat inflammatory bowel diseases (IBD) including ulcerative colitis and Crohn's disease. A pilot multi-center Phase II clinical study with the cGMP PDE inhibitor CP461, as a potential treatment for Crohn's disease, is currently underway at the University of Chicago Medical Center and other sites.

"When this patent issues, it will broaden our cGMP PDE patent estate and expand it beyond cancer," said Robert J. Towarnicki, president and chief executive officer of Cell Pathways. "In our research efforts, we have found that administering an inhibitor of cGMP PDE 2 and 5 improved clinical signs in dogs with chronic and refractory inflammatory bowel disease."

"The clinical signs of IBD started to resolve in all animals by day 10 of treatment with CP461, and 86% of the dogs were free of disease symptoms by day 30," said Rifat Pamukcu, M.D., chief scientific officer of Cell Pathways, Inc. "Since IBD in dogs is similar to the disease in humans, these positive preclinical results with a cGMP PDE inhibitor in dogs prompted us to initiate our pilot Phase II study in humans with Crohn's disease."

Cell Pathways also reported previously that intestinal biopsies from the dogs and humans with confirmed IBD contained activated macrophages that expressed high levels of PDE 2 and 5. Such macrophages are known to release tumor necrosis factor-alpha (TNF-alpha), an immune modulatory cytokine that plays a central role in IBD. "Our researchers demonstrated in a cell culture model of activated macrophages that inhibition of PDE 2 and 5 induces apoptosis (programmed cell death) of the cells and inhibits the production of TNF-alpha. These findings further support the hypothesis that PDE 2 and 5 inhibition may provide a novel approach to the treatment of IBD," stated Dr. Pamukcu.

"With this patent, we will have patent protection beyond CP461 in this indication, including PDE 2 and 5 inhibitors generally," said Mr. Towarnicki.

In related news, Cell Pathways also received Notices of Allowance for patent applications covering the use of PDE 2 and 5 inhibitors generally in the treatment of type I diabetes and in the treatment of cystic fibrosis. "These patent applications were the result of our unpublished preclinical findings that activated macrophages in the affected tissues in these diseases express high levels of PDE 2 and 5, as we found in IBD," said Dr. Pamukcu.

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 manufactured by others. Cell Pathways' initial drug candidates in clinical development are Aptosyn(R) (exisulind) and CP461.

Certain statements 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. Statements of historic fact must also be understood in the context of, and subject to, these risks. Such risks and uncertainties relate to, among other factors: early stage of development; absence of approved products; history of operating losses; the need for further financing, whether through issuance of equity or debt, corporate collaborations or strategic alliances, or revenues generated from the marketing and/or distribution of in-licensed products; the risk that our technology may not prove effective in inflammatory bowel disease or any other non-cancer area; risks associated with the scope, validity, enforceability and utility of patents described above; the risk of 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 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; the risks that CP461 will not exhibit safety and efficacy in its current and future clinical trials in cancer indications, in Crohn's disease or in any other disease indication; the risks that accrual of our Phase III trial of Aptosyn(R) and Taxotere(R) is not completed within a reasonable time and that safety and efficacy are not demonstrated by this combination therapy in this trial; 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, of Aptosyn(R), CP461 or any other compound may not be positive; uncertainty of obtaining regulatory approval of any compound for any disease indication whether due to adequacy of the development program, adequacy of evidence of safety and efficacy, changing regulatory requirements or otherwise; the risk that the U.S. Food and Drug Administration may stop or delay any clinical study for reasons of safety or otherwise; the risk that a registration strategy for CP461 in cancer is not fully developed within a reasonable time, whether due to the nature or timing of further clinical results or otherwise; the risks 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; the commercial risk and risk of liability in 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 in exchange for financing and operational assistance, or in which the Company acquires rights and obligations; the volatility of the market price of our Common Stock; our ability to sell securities registered under the shelf registration statement or otherwise; the risk of dilution through the effects of further financings or strategic alliances; 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, enforceability and utility of patents on our technology and compounds; the risk of 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, and subject to, 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.