Amersham Biosciences' OligoProcess Assists Isis Pharmaceuticals in Achieving World's Largest Antisense Oligonucleotide Synthesis Scale per Run.

Business Editors/Health/Medical Writers

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PISCATAWAY, NJ--(BUSINESS WIRE)--Sept. 4, 2003

the life sciences business of Amersham (LSE:, NYSE:, OSE: AHM), today announced that Isis Pharmaceuticals recently completed the world's largest antisense oligonucleotide synthesis scale per single run. Isis accomplished this pharmaceutical industry manufacturing first by using OligoProcess(TM) from Amersham Biosciences, combined with its proprietary synthesis methods and custom reactor column.

The OligoProcess synthesizer produced more than 4 kilograms (600-millimole scale) of high-quality crude 20mer oligonucleotide in approximately 5.3 hours. The synthesis demonstrates the utility of OligoProcess and Isis' synthesis methods as well as the ability to produce a metric ton of crude oligonucleotide on an annual basis.

Amersham Biosciences designed a custom OligoProcess, according to Isis' functional specifications, which accommodated the antisense leaders' proprietary synthesis methods. OligoProcess operates on the Unicorn(TM) platform and is an automated system of pumps that delivers the precise levels of solvents at appropriate intervals with high capacity, through a column packed with solid support, called Primer Support(TM) 200. The solid support used by Isis to achieve the single run consisted of beads of polystyrene cross linked with divinylbenzene, with the first nucleoside attached at a density of 200 micromoles per gram. The high density of nucleoside loading on this solid support resulted in an elevated scale of synthesis per reaction volume. The advantage of this high synthesis scale is a reduction in the quantity of reagents consumed per run and an increased yield of full-length oligonucleotide.

"Amersham Biosciences continues to demonstrate its leadership in the supply of cGMP compliant, highly customized oligonucleotide synthesizers and reagents, " said Anthony Scozzari, Vice President, Drug Substance Manufacturing and Process Chemistry of Isis. "Amersham Biosciences' base knowledge of oligonucleotide synthesizer design, developed over the past 15 years, has been critical to our synthesis and process development successes."

The synergy of the OligoProcess, Primer Support 200 and Isis' synthesis methods has the potential to produce up to 10 kilograms of crude oligonucleotide (1.5 Molar scale) every 6.3 hours or 6800Kg per year. Isis is currently planning to initiate an 800-millimole scale run later this year.

Amersham Biosciences, the life sciences business of Amersham (LSE: NYSE: OSE: AHM), is a world leader in developing and providing integrated systems and solutions for disease research, drug development and manufacture. Our systems are used to uncover the function of genes and proteins, for the discovery and development of drugs and for the manufacture of biopharmaceuticals. The customers for Amersham Biosciences' products and technology are pharmaceutical and biotechnology companies and research and academic institutions, principally in North America, Europe, Latin America and Asia. More information about Amersham Biosciences is available at www.amershambiosciences.com Amersham Biosciences--enabling molecular medicine