Cell Pathways

(CLPA)

shares collapsed after the

Food and Drug Administration

rejected its lead drug Aptopsyn, an experimental treatment for colon lesions that may lead to cancer.

Cell Pathways shares plunged $19, or 63%, Monday to $11. The company disclosed the FDA rejection Friday after the market closed.

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Cell Pathways said it is working with the agency to address deficiencies in its application for approval for Aptosyn, an older drug that the company said showed promise in treating familial polyposis, or FAP, a condition that can lead to colon cancer.

CEO Robert J. Towarnicki said "we remain confident of the promise of Aptosyn for the prevention and treatment of cancer and precancerous lesions. This is based on the laboratory, animal and human data we have gathered in a wide variety of indications."

Some analysts said that even if the drug was approved, the company would have a tough time competing against drug giant

Pharmacia

(PHA)

, whose blockbuster painkiller Celebrex is already approved for FAP. s