Press Release: Astex Grants Cytochrome P450 License to Glaxosmithkline

Astex Grants Cytochrome P450 License to Glaxosmithkline CAMBRIDGE, April 24, 2007 -- Astex Therapeutics today announced that it has granted a non-exclusive, worldwide license to its cytochrome P450 intellectual property to GlaxoSmithKline. Under the terms of the agreement, GlaxoSmithKline will pay an up-front fee to Astex in return for a license under Astex's portfolio of granted and pending cytochrome P450 patents. The specific financial terms and other details of the license were not disclosed. "This agreement is another example of Astex's commitment to making its human cytochrome P450 technology available to other companies who could benefit or are already benefiting from its application in the discovery and development of novel drugs with reduced metabolic liabilities. We expect that the application of Astex's groundbreaking research, which was published in Nature and Science, will benefit many companies' drug discovery and development programmes", said Leon Bushara, Chief Executive Officer. Astex is continuing to strategically leverage its cytochrome P450 intellectual property. A license to its human cytochrome P450 technology was granted to Pfizer Inc. in 2006 and further non-exclusive licenses to the technology are available. Note to News Editors Cytochromes P450 (CYP450) are the most significant group of drug-metabolising enzymes in humans. 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. Astex was the first group in the world to successfully determine the 3-dimensional crystal structure of a human cytochrome P450 enzyme and has a number of granted patent in the UK, Europe and in the US including: GB 2 395 718 B covering the use of the crystal structure of human cytochrome P450 3A4 granted on 19th January 2005 EP 1 438 337 B1 covering the use of the crystal structure of human cytochrome P450 2C9 granted on 20th September 2006 GB 2 408 509 B covering the use of the crystal structure of human cytochrome P450 3A4 granted on 1st November 2006 US 7,148,046 B2 covering crystals of human cytochrome P450 3A4 granted on 12th December 2006. Astex scientists have published on the crystal structures of human isoforms 2C9 and 3A4 in the world-leading scientific journals Nature and Science(1). The insight provided by knowledge of the crystal structures of cytochromes P450 and how drugs bind to these enzymes allows for the design of drug candidates with improved drug metabolism properties thereby reducing attrition rates in drug development and resulting in safer and more effective new medicines. About Astex Astex Therapeutics is a biotechnology company that discovers and develops novel small molecule therapeutics. Using its pioneering fragment-based drug discovery platform Pyramid(TM), Astex has built a pipeline of four molecularly-targeted oncology drugs, of which two are currently being tested in clinical trials and two are in pre-clinical development. In addition to its proprietary research programmes, Astex's unprecedented productivity in lead discovery has been endorsed through numerous partnerships with major pharmaceutical companies, including Novartis, AstraZeneca, and Boehringer Ingelheim. (1) 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 For further information on Astex Therapeutics please visit the Company's website at CONTACT: Contacts: Astex Therapeutics Limited, Leon Bushara, ChiefExecutive Officer, Email: , Tel:+44(0)1223-226200 [email protected]