July 13, 2000
For those who have taken all three classes of available antivirals, there is an urgent need both for medications that can still be active in these classes, as well as the development of drugs that work by completely new actions. The lead in the development for a new class of drugs is a fusion inhibitor known as T-20. Fusion inhibitors work by preventing HIV from attaching and fusing onto a cell membrane, which prevents HIV from injecting its RNA into the cell. Because it works by a new mechanism, it can be expected to be fully potent even in those who have taken medications in all of the available classes. Earlier studies have shown that this agent is active, initially achieving up to about a 1.4 log drop in viral load when added as a single agent to a regimen. This presentation reviewed the experience after one year for those who were in the dose-finding study of T-20, results of which were presented at the ICAAC meeting in 1999.
These patients were all very heavily experienced in all of the available antivirals, having taken many of the available medications already in all three classes. In all, 70 people entered this study on which they received T-20 along with other available antiviral medications, with the choice guided by a genotype.
T-20 is given at a dose of 50mg twice a day by subcutaneous self injection, (similar to how insulin is taken). Importantly, a quality-of-life survey was done in this group, and around 75% of the participants in this study found no significant impact on their quality of life from having to prepare and administer this medication. No one discontinued for reasons of side effects attributed to T-20 during this one year follow-up. After one year, 40 of the 70 were still taking T-20. Fourteen had stopped at some point due to less than a half log drop in the viral load, and 16 others stopped during the year for other reasons. In the group of 40 still on T-20 at one year there was a mean drop in viral load of 1.4 logs, with 39% having a viral load below detection at the 400 copy limit. Side effects were largely limited to small nodules at the injection site seen in 71%, but none led to treatment discontinuation, as they were noted to be transient.
These results demonstrate the long-term safety of T-20, a key finding in the development of a new class of medications. As all of the participants received T-20 here, it is not possible to define what contribution was made by T-20 in the degree of viral suppression observed. However, as the group was heavily pretreated, it is noteworthy that nearly 40% had an undetectable viral load by the 400-copy assay. Further controlled studies of T-20 in this population are planned to begin later this year to better define the contribution of T-20 in patients most in need of treatment options.
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