TRIPLE-DRUG THERAPY

This is the name given to a radically new treatment for AIDS which involves a cocktail of three drugs. Two are AZT (zidovudine) and 3TC (lamivudine), older reverse transcriptase inhibitors, which reduce the rate at which the RNA in the virus can be transformed into its DNA equivalent, essential if the virus is to copy itself. The third drug is a new type, a protease inhibitor, of which three have just been licensed in the US and Europe with generic names indinavir, saquinavir and ritonavir. The new protease inhibitors stop a later stage of reproduction, when the DNA has been used as a template to make new molecules but an enzyme called HIV protease is needed to break them into useful bits. Some startling results have been reported in initial trials, suggesting that a combination of the three drugs can sometimes be much more effective than any alone or in pairs. A few individuals in an advanced stage of the disease have had the amount of virus in their bloodstreams (the viral load), reduced to virtually undetectable levels. The major problem remaining is the expense of the therapy, a year’s treatment costing about $10,000 (6,600 pounds sterling), which makes it inaccessible to poor patients. The treatment is also known as combination therapy.

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