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The big earners in a lucrative medical market

Drugs made by the techniques of genetic engineering have been licensed for more than 13 years and now bring in revenues of more than $3bn a year in the US alone.

According to John Hodgson, European publishing manager of Bio/technology magazine, some 26 genetically engineered pharmaceuticals have now been licensed for use around the world - 20 of which have been accepted in the UK.

Amgen, the American start-up biotechnology company, has the two top- selling genetically engineered drugs in the US. The company's Neupogen, which is used to stimulate the production of white blood cells following cancer treatment, had US sales of more than $719m last year.

In the rankings of revenue earners, Neupogen is closely followed by Epogen, an Amgen drug to stimulate the production of red blood cells. This generated US revenues of $587m last year. Such drugs are needed to treat cases of serious anaemia, which particularly afflicts people who have to undergo kidney dialysis. Amgen markets Epogen itself, but has an agreement with Ortho-Biotech to market a related red-blood cell stimulating product, known as Procrit, which is worth $500m a year in the US market.

Perhaps the most widely-used drug is human insulin for the treatment of diabetes which, produced by Genentech and marketed by Eli Lilly, has US revenues of around $560m a year. Insulin was one of the first "recombinant DNA" (genetically engineered) drugs to be approved for medicinal use, in 1982. Genentech also produces recombinant human growth hormone which is used to treat pituitary dwarfism and has annual US sales of $217m.