Release issued 17th December 2001

Cambridge, UK, 17 December 2001. Astex Technology, the structure-based drug discovery company pioneering the use of high throughput X-ray crystallography (HTX (tm)) technology, today announced that it has solved the first 3-dimensional crystal structure of a human cytochrome P450 enzyme. This important discovery will enable drugs to be rationally designed to reduce metabolic and toxicity problems.

Cytochrome P450s are the most prominent group of drug-metabolising enzymes in humans. The action of these proteins is the cause of adverse reactions to many marketed drugs and drug-combination therapies. The administration of certain drugs may also be ineffective or even harmful as a result of patient-specific variations in cytochrome P450s. In addition, many failures in drug development have been attributed to this class of proteins. The insight provided by this P450 structure should improve the success rates and economics of drug discovery and result in safer and more effective new medicines.

Dr Harren Jhoti, Co-Founder and Chief Scientific Officer, said, "We are delighted to announce the resolution of the first crystal structure of a human cytochrome P450. This is one of the most difficult types of protein structures to solve, as the proteins are large, complex structures, partly embedded within lipid membranes. By understanding how these proteins recognise drug molecules at the atomic level, we will rationally design drugs with better metabolic and toxicity profiles and thus an improved chance of making it to the market."

"This breakthrough further demonstrates the effectiveness of our proprietary technology and the excellence of our scientific team in resolving the structure of even the most difficult of protein target classes. We will build on this success and continue our progress with the other key members of this protein family," said Timothy Haines, Chief Executive of Astex. "This initial cytochrome P450 crystal structure will be invaluable to enhancing the properties of the lead compounds that Astex is developing. It will also be made available to a limited number of pharmaceutical company partners."

Astex Technology is a structure-based drug discovery company pioneering the use of high throughput X-ray crystallography for the rapid identification of novel drug candidates. The company's unique structural screening approach utilizes protein crystal structures to detect the binding of drug fragments, which are then optimized into potent lead compounds. Facilitating this approach is the company's integrated drug discovery platform of HTX(tm) technologies, which covers all aspects of structure-based research, including protein production, crystallization, structure determination, bioinformatics and computational and medicinal chemistry. Astex is focusing its drug discovery approaches on protein targets from families and/or pathways, including validated kinases, phosphatases and proteases implicated in human disease. Astex has two research agreements with Janssen Research Foundation, a division of Johnson & Johnson, and a cytochrome P450 structural biology research agreement with AstraZeneca AB.

(26th May 2009) Astex reports positive data from its Phase I study of AT9283 at the ASCO Annual Meeting 2009

(24th March 2009) Astex Awarded £2 Million from Wellcome Trust for Pioneering HCV Research

(2nd March 2009) Astex Receives Award from the Multiple Myeloma Research Foundation to Support Clinical Development of AT7519

(11th February 2009) Astex and Cancer Research UK Collaborate on Clinical Studies of AT9283 in Childhood Cancers

(1st December 2008) Astex Presents Updates on AT7519 and AT9283 at the American Society of Hematology (ASH) Conference