Recently, new antiretroviral drugs called protease inhibitors have become available. These drugs interfere with protease , a different enzyme used by the virus. Protease inhibitors keep immature virus from maturing into particles that are capable of infecting new cells. Saquinavir, ritonavir, and indinavir are protease inhibitors, as is nelfinavir, an investigational drug currently under FDA review. Although reverse transcriptase inhibitors can greatly reduce the amount of HIV in the body, they are not powerful enough to eliminate the virus.
Protease inhibitors are much more effective.
Given in combination with reverse transcriptase inhibitors, they can reduce the virus in the blood to undetectable levels in many patients, at least for a period of time. However, the fact that the virus can't be detected doesn't mean that it has been eliminated. While antiretroviral drugs may control HIV infection, they do not provide a cure. If therapy is stopped or interrupted, most researchers believe the virus is likely to reappear. When an antiretroviral drug begins to lose its effect, it is usually because the virus has developed resistance to the drug.