US Patent Granted To Cyclacel For Novel Cyclin Dependent Kinase Inhibitor Series

Dundee, U.K. - 18 February 2005 - Cyclacel Group plc (“Cyclacel”), the cell cycle-based biopharmaceutical company, announced today that it received a U.S. Patent (US6,699,854) covering a novel series of pyrimidine small molecules shown to control the progress of cells through the cancer cell cycle. One group of these novel compounds works by inhibiting Cyclin Dependent Kinases (CDK), drug targets that control cancer cell division. Further groups of compounds within the series work by inhibiting alternative CDK target profiles and other cell cycle kinases. The patented compounds may be useful as therapeutics for proliferative diseases such as cancer, inflammatory and autoimmune diseases, in which cells divide out of control, and certain viral infections.

Cell cycle inhibitors are an area of growing interest to the pharmaceutical industry because of the importance of CDK and cyclin drug targets in cancer biology. Cyclacel is a world leader in this field. Seliciclib, its lead CDK inhibitor drug, is currently the only orally available CDK inhibitor in Phase II clinical trials. Seliciclib is a patented purine molecule as opposed to the recently patented agents which were designed on a pyrimidine chemical scaffold. Lead compounds from the new series demonstrated highly potent inhibition of CDK activity, with many at the subnanomolar level. Several pyrimidine drugs have passed the proof of concept stage as they have been shown to be active in in vivo models when taken by mouth and are progressing into preclinical development.

Dr. Robert Jackson, Chief Scientific Officer, said, “This patent validates the talent of our scientists who invented another novel drug series with multiple mechanisms of action. We used state-of-the-art technology based on target protein structures to design compounds that hit a variety of cell cycle targets resulting in multiple product opportunities. We have achieved significant improvements in activity over previous generations and many of the new compounds have drug-like physicochemical properties. Our objective is to progress one or more of these molecules into clinical trials as soon as possible.”

About Cyclacel ( www.cyclacel.com )
Cyclacel is a biopharmaceutical company dedicated to the discovery, development and commercialization of novel, mechanism-targeted drugs to treat human cancers and other serious disorders. The company is currently evaluating seliciclib (CYC202), an orally-available Cyclin Dependent Kinase inhibitor, in Phase II clinical trials for the treatment of non-small cell lung cancer and B-cell hematological malignancies. CYC682 is an orally-available, cell cycle modulating nucleoside analog in Phase I clinical trials for the treatment of cancer. Cyclacel has eight additional programs at preclinical stages.

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