Protease inhibitors are a new class of anti-HIV drugs.
They work by blocking a part of HIV called protease. When protease is blocked, HIV makes copies of itself that can't infect new cells. Studies have shown that protease inhibitors can reduce the amount of virus in the blood and increase T4 cell counts. In some cases these drugs have improved T4 cell counts even when they were very low or zero. Studies have also shown that these effects can wear off over time.