Development of Bioprocesses for the Generation of Anti-Inflammatory, Anti-Viral and Anti-Leukaemic Agents

Abstract

This chapter is based on a lecture presented at the 9th European Congress on Biotechnology held in Belgium, Brussels (11–15th July 1999) and gives an overview of several bioprocesses that have recently been developed at Glaxo Wellcome. Three bioprocesses, to produce key chiral intermediates for the synthesis of drug candidates, are described. 1) The nucleoside oxidase from Stenotrophomonas maltophilia was used to generate 5′-carboxylic acid derivatives of nucleoside analogues as key intermediates in the synthesis of a novel group of compounds with broad anti-inflammatory properties. The synthetic utility of the enzyme was exploited to produce 5′-carboxylates of several purine nucleoside analogues, including the carbocyclic nucleosides aristeromycin and neplanocin A on a preparative scale. The enzyme was found to have surprisingly wide substrate specificity toward unnatural nucleosides especially in the base moiety. 2) A serine-type protease from an alkalophilic Bacillus sp. was used to resolve racemic N-substituted lactams as key intermediates in the synthesis of abacavir (Ziagen™), a selective and potent reverse transcriptase inhibitor which was recently approved by the FDA for the treatment of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections in adults and children. A simple and efficient process, using commercially available hydrolytic enzymes, was developed to produce enantiomerically pure N-substituted α-lactams. 3) A co-immobilised uridine phosphorylase and purine nucleoside phosphorylase preparation from recombinant E. coli strains was used in the production of the anti-leukaemic agent 506U78. Fermentation and bioconversion conditions were optimised and scaled up with up to 200g/L of substrate input and the coimmobilised enzymes could be re-used several times in bioreactors. In a parallel process an immobilised preparation of Candida antarctica lipase was used to produce esters of 506U78 which were shown to have a better water solubility and bioavailability. Vinyl acetate was used as an acyl donor and reactions were carried out in anhydrous 1,4-dioxane with up to 100g/L of substrate input.