Cell Pathways Advances Clinical Development of Second-Generation SAANDs Drug, CP461.

Business Editors/Health & Medical Writers

HORSHAM, Pa.--(BW HealthWire)--Aug. 3, 2000

Cell Pathways, Inc.(Nasdaq:CLPA) today announced that the Company has completed Phase IB human testing of its second-generation selective apoptotic antineoplastic drug (SAAND), CP461, which the Company is developing as a potential treatment for cancer. Results of this safety trial demonstrated that CP461 can be chronically administered orally at doses that achieve or exceed targeted blood levels and are well tolerated by cancer patients.

"Based on these encouraging safety results, we are now actively planning Phase II studies of CP461 as a single agent in several different cancer indications," said Robert Bellet, M.D., senior vice president, clinical and regulatory affairs. "We plan to start enrollment to the first of these trials late in the fourth quarter of this year or early in the first quarter of 2001. Based on promising preclinical results with this drug in combination chemotherapy, we are also planning to initiate Phase I safety studies combining CP461 and other chemotherapeutic agents in the fourth quarter of this year."

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 prevent and treat cancer. The Company's lead product candidate, Aptosyn(TM) (exisulind), is currently under review by the U.S. Food and Drug Administration as a potential new therapy for the prevention and treatment of precancerous colon polyps in patients with familial adenomatous polyposis (FAP). The Company is also conducting further studies with Aptosyn(TM), both as a single agent and in combination with conventional chemotherapeutics, for the treatment of a variety of cancerous and precancerous indications including the prevention of recurrent prostate cancer. For additional information on Cell Pathways, Inc., visit the Company's website at http://www.cellpathways.com.

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, the absence of approved products; history of operating losses; early stage of development; the costs, delays and uncertainties inherent in basic pharmaceutical research, drug development, clinical trials and the regulatory approval process, with respect to both the Company's current product candidates and its future product candidates, if any; dependence on development of Aptosyn(TM) (exisulind); the 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; the uncertainty of obtaining regulatory approval, including uncertainty of approval of the New Drug Application submitted for Aptosyn(TM) (exisulind) for familial adenomatous polyposis) a rare disease that puts those afflicted at high risk of developing colon cancer,) whether in connection with the adequacy of the data generated in the clinical trials of Aptosyn(TM) (exisulind) or otherwise; the uncertainty of the effect of product approval, if achieved, on the market price of the Common Stock; the timing and scope of any approval which might be received for any compound for any indication in the future; acceptance by providers of healthcare reimbursement; the validity, scope and enforceability of patents; the actions of competitors; dependence upon third parties; product liability; and the need for further financing. These and other risks are detailed in the Company's reports filed from time to time under the Securities Act of 1933 and/or the Securities Exchange Act of 1934, including the sections entitled "Business," "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Other Events" in the Company's reports on Form 10-K for the year ended December 31, 1999, Form 10-Q for each of the first three quarters of 2000, Form 8-K for the month of August 1999, and Form S-3 filed in December 1999. You are encouraged to read these filings as they are made from time to time. They are available over the Internet from the SEC in its EDGAR database. Given the uncertainties affecting pharmaceutical companies in the development stage, current and prospective investors 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. The Company undertakes no obligation to update or revise the statements made herein or the factors which may relate thereto.