against HIV highly resistant to most of the currently-used PIs. The correct dose, however, still has to be formulated: tipranavir's current formulation produces diarrhoea and nausea in up to a quarter of patients, which could make it difficult to take.
Schering-Plough's SCH-C is the first 'Chemokine Receptor Antagonist' to be tested on humans. It gets in the way of HIV when it tries to attach to a cell, but works at a different stage to the 'Fusion Inhibitors' already being used, T-20 and T-1249. Unlike those drugs, it can be taken by mouth. One potential drawback is that SCH-C only works with a type of HIV that tends to predominant in early infection.
Scientists at Bristol-Myers Squibb have developed BMS 806. This also stops HIV attaching itself to cells, but it works at an earlier stage of the process, placing a barrier between the CD4 molecules on the surface of T-cells and the protein which forms the 'knobs' on HIV that first contact the cells. About 20 per cent of naturally-occurring HIV, however, carries pre-existing resistance, so its knobs cannot be 'gummed up' by the drug. BMS 806 has only got to the test-tube stage of evaluation.
In Japan, a team has finally found a potentially useful integrase inhibitor. Integrase is the third enzyme HIV uses to build copies of itself, and a drug that works against it has been sought after for many years - presenter Tamio Fujiwara told delegates he
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started working on HIV integrase in 1987. The drug, S1360, has so far
