Astex Achieves Milestones in GSK Collaboration

CAMBRIDGE, England, May 3, 2011 - Astex Therapeutics, the UK-based biotechnology company
developing targeted therapies for oncology and virology, announced that it
has achieved multiple early milestones in its fragment-based drug discovery
collaboration with GlaxoSmithKline which commenced in November 2009. Total
milestone payments received under the collaboration have now reached GBP5.9
million.

The milestones relate to the application of Astex's
Pyramid(TM) fragment based screening platform, against a number of molecular
targets of interest to GSK. Following the identification of validated
fragment hits, the joint project teams prioritise fragments to be taken into
lead optimization with the intention of selecting clinical development
candidates for further development by GSK.

Commenting on the achievement of the early milestones, Dr Harren Jhoti,
Astex's Chief Executive Officer, said, "We are delighted to have
achieved these initial milestones within 18 months of beginning our
collaboration with GSK. This achievement is testament, not only to the power
of Astex's technology to rapidly deliver novel chemical start points against
challenging disease targets, but is also a reflection of how well the
Astex-GSK joint project teams are working together in the collaboration."

About Astex Therapeutics

Astex is a UK-based 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
molecularly-targeted oncology drugs, of which three are currently being
tested in clinical trials with others in discovery and pre-clinical
development.

In addition to its proprietary research programmes, Astex's productivity
in lead discovery has been endorsed through numerous partnerships with major
pharmaceutical companies, including AstraZeneca, Bayer-Schering, Boehringer
Ingelheim, GlaxoSmithKline, Novartis and Johnson & Johnson.

On April 6th 2011, Astex announced that it had entered into a
definitive merger agreement with SuperGen, Inc., a NASDAQ listed company, to
form a financially strong, oncology focused, company, to be called Astex
Pharmaceuticals, Inc.

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

    For more information, please contact:

    Astex Therapeutics Ltd
    Jeremy Carmichael, PhD
    Director of Business Development
    Tel: +44(0)1223-226200
    Email: j.carmichael@astex-therapeutics.com

    Press & Media Enquiries
    College Hill
    (Europe) Melanie Toyne Sewell / Daniel Gooch
    Tel: +44-20-7866-7866
    (US) Rebecca Skye Dietrich
    Tel: +1-857-241-0795
    Email: astex@collegehill.com

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