Protease inhibitors (PIs)
Protease inhibitors prevent cleavage of protein precursors essential for HIV maturation, infection of new cells and viral replication. Use of a protease inhibitor in combination with other drugs has led to marked clinical improvement and prolonged survival even in patients with advanced HIV infection. Most protease inhibitors potently suppress HIV in vivo. Combinations of two protease inhibitors are increasingly being used; one is usually ritonavir, which inhibits the metabolism and increases serum concentrations of other PIs.