Antiretroviral Therapy and Drug Resistance

Use of Multiple Active Drugs

There were several important presentations related to the management of those highly-treatment experienced with antiretroviral therapy and who have developed resistance to many drugs. One study showed data from those treated with the recently approved protease inhibitor tipranavir (Aptivus™) with very high rates of viral suppression. This was particularly true when it was used with another active agent, enfuvirtide (T-20, Fuzeon™). The importance of using multiple active drugs in a new regimen had been shown before and demonstrates that the new protease inhibitor is an important option for those with drug resistance. For many with drug resistance starting a new regimen they will use enfuvirtide as a second active agent. Enfuvirtide works at a unique step in the virus's replication cycle and is administered with a small needle under the skin twice per day. While the drug is very effective its use is limited by the need for injection and the resultant local skin redness and pain that are occasionally associated with its use.

Another important presentation described the experience in those who had achieved undetectable levels of virus on an enfuvirtide-contain regimen that then either continued the same therapy or were followed after stopping the enfuvirtide part of the regimen. This was a very small study but did show a few more individuals experiencing viral rebound after stopping treatment than those who did not. Consequently, if undetectable levels of virus are achieved on such a regimen stopping the enfuvirtide should be done with caution.

Needleless System

There was another presentation at this meeting demonstrating that enfuvirtide can be used with a new needleless system that provides equivalent amounts of drug with less skin reaction. While preliminary, this might offer important new options for patients in the future.