be injected - it 'jams' the mechanism HIV uses to enter cells.
T-20 is also more difficult to make than other drugs and is likely to be more expensive. It will be marketed by Roche Products under the brand name Fuzeon.
Roche warned this month that demand for T-20 might outstrip supply during its launch in 2003. "The success of T-20 will lead to a potentially faster and greater demand for Fuzeon than initially foreseen," a spokesman said.
The TORO 1 and 2 studies of T-20 used it as a 'salvage' drug for a total of

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T-20 (yellow arrow) jams infection

almost 1,000 patients who had been failed by all three current classes of HIV drugs - nukes, non-nukes, and protease inhibitors. Two-thirds of patients were put on T-20 plus the best combo of oral drugs doctors could devise (based on drug resistance tests), while one-third did without it.
In the TORO 2 study, the T-20 patients experienced an average 27-fold viral load drop, whereas the patients on oral drugs alone only had an average 4.5-fold drop. Unsurprisingly in such a treatment-experienced group the proportion reaching viral undetectability was small, with only 12 per cent on T-20 achieving a viral load under 50, and 5.3 per cent not on T-20. The T-20 patients saw an average CD4 increase of 65, compared with 38 in the other group.
In the trial group, only three per cent of the T-20 patients couldn't tolerate the injections, but virtually all of them had 'injection site reactions'. This means reddening, itching or lumps around the injection sites in the skin of the stomach, thighs or arms - and in a quarter these lumps were persistent.
Another fusion inhibitor, T-1249, is following in T-20's wake, and Danny Bolognesi, managing director of manufacturers Trimeris, said that this so far appeared more potent, less likely to cause HIV resistance, and can be injected much less often.