Astex Technology Patents Granted Covering The Use Of Key Human Cytochrome P450 Structures

CAMBRIDGE, England, Oct. 17 /PRNewswire/ -- Astex Therapeutics today announced the grant of two patents covering the use of the crystal structures of human cytochrome P450 enzymes. Cytochromes P450 are among the most significant proteins involved in the body's break-down of drug products and are widely used in pharmaceutical industry research and development. The two patents awarded to Astex are European patent EP1 438 337(1) covering the use of the crystal structure of human cytochrome P450 2C9 and GB 2 408 609(2) which covers the use of the crystal structure of human cytochrome P450 3A4. Astex now has three granted patents covering this family of enzymes.

Astex has been actively involved in human cytochrome P450 research since the company's formation and Astex scientists were the first group to successfully solve the crystal structures of human cytochromes P450, 3A4 and 2C9(3). This research has resulted in an extensive patent portfolio covering methods for purifying cytochrome P450 protein, preparing cytochrome P450 crystals, obtaining the crystal structure coordinates and their use in drug discovery and development. Astex's first patent covering the use of the crystal structure of cytochrome P450 3A4 issued in 2005(4). Astex has now established a program to offer licenses under its broad portfolio of intellectual property in this area. The first such license, granted to Pfizer, was announced in January 2006.

"Insights provided by the crystal structures of human cytochrome P450 enzymes help pharmaceutical researchers to design safer and more effective new medicines," said Leon Bushara, Chief Executive Officer of Astex. "Astex scientists were the first to solve these structures and publish them, and we are pleased that other research groups in the pharmaceutical industry have found them useful. The granting of these additional patents has extended significantly the scope and range of our coverage across Europe."

Contacts: Astex Therapeutics Leon Bushara Chief Executive Officer Tel +44 (0)1223 226200 Email: l.bushara@astex-therapeutics.com Web: www.astex-therapeutics.com Brunswick Group LLP Jon Coles / Justine McIlroy / Alex Tweed Tel. +44 (0) 207 404 5959 Email: astex@brunswickgroup.com Notes to Editors

Cytochromes P450 (CYP450) are the most significant group of drug- metabolising enzymes in humans and CYP450s 2C9 and 3A4 are generally regarded as among the most important members of this group. The action of these enzymes is the cause of adverse drug reactions to many marketed drugs and drug-combination therapies and many failures of novel drugs during their development have been attributed to their interactions with this class of enzymes. For example, drugs may be metabolized too rapidly by CYP450 before they have had time to be effective, or they may be broken down into smaller molecules which are toxic. Certain drugs may also inhibit the activity of a CYP450 enzyme which is involved in the metabolism of another drug that, given at the same time, can become elevated in the patient to levels which can cause side effects or become dangerous.

The insight provided by knowledge of the crystal structures of cytochrome P450s and how drugs bind to these enzymes allows for the design of drug compounds with more optimal drug metabolism properties thereby reducing attrition rates in drug development and resulting in safer and more effective new medicines.

About Astex Therapeutics

Astex Therapeutics is a UK-based biotechnology company producing novel small molecule therapeutics. Using its pioneering fragment-based drug discovery approach, Astex has rapidly established a broad pipeline of next- generation, molecularly-targeted oncology drugs. Astex's lead compound, AT7519, is currently in Phase I clinical trials in the US and in the UK while its second clinical-stage compound, AT9283 is currently in a phase I/IIa clinical study in the US. The Company has two further clinical candidates; AT9311, an oral cell cycle inhibitor and AT13387, an Hsp90 inhibitor, both of which are in formal pre-clinical development. All four of Astex's current drug products have been discovered internally using the Company's proprietary drug discovery approach.

Astex's leading position in fragment-based drug discovery derives from its integrated discovery engine, Pyramid(TM). High-throughput X-ray crystallography and other biophysical techniques are used to identify drug fragments bound to target proteins and to transform the fragments, using efficient medicinal chemistry, into potent, selective drug candidates. Pyramid(TM) has been successfully applied across a wide variety of therapeutic targets, including those regarded as "intractable" by the pharmaceutical industry, resulting in lead compounds for the potential treatment of cancer, inflammation and Alzheimer's disease.

Astex's unprecedented productivity in lead discovery has been endorsed by drug discovery and development alliances with major pharmaceutical companies including AstraZeneca, Astellas Pharma, Boehringer Ingelheim, Mitsubishi Pharma, Novartis, Sanofi-Aventis and Schering AG. These alliances have a total potential value in excess of US$1billion including the US$520m alliance signed with Novartis in December 2005 which is focused on the development of AT9311 and AT7519.

Astex Therapeutics was established in 1999 and is well financed by leading, blue chip US and European investors (Abingworth, Advent International, Alta Partners, Apax, GIMV, HypoVereinsbank, Oxford Bioscience Partners, Schering AG and the University of Cambridge).

For further information on Astex Therapeutics please visit the Company's website at http://www.astex-therapeutics.com.

(1) EP1438337 Astex Therapeutics Limited. Inventors: Williams, PA,; Cosme, JM,; Ward, A; Brewerton, SC; Hamilton, BJ,; Jhoti, H; Jones, MA,; Vuillard, L, Michel, M; Williams, MG; "Crystals of Cytochrome P450 2C9, Structures Thereof and Their Use."

(2) GB 2 408 509 Astex Therapeutics Limited Crystal structure of cytochrome P450 3A4 and its use.

(3) Williams et al (2004) 'Crystal structures of human cytochrome P450 3A4 bound to metyrapone and progesterone', Science Magazine, 2004 Jul 30:305 (5684): 683-686.

Williams et al (2003) 'Crystal structure of human cytochrome P450 2C9 with bound warfarin', Nature, 2003 July 24;424 (6947): 464-8

(4) GB2395718. Astex Therapeutics Limited. Inventors: Jhoti, H; Kirton, SB; Tickle, I; Vonrhein, C; Williams,PA. Crystal structure of cytochrome P450 3A4 and its use.

Astex Therapeutics

CONTACT: Leon Bushara, Chief Executive Officer of Astex Therapeutics,+44-0-1223-226200, l.bushara@astex-therapeutics.com; or Jon Coles, JustineMcIlroy, or Alex Tweed, all of Brunswick Group LLP, +44-0-207-404-5959,astex@brunswickgroup.com

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