HIV protease inhibitors: their anti-HIV activity and potential role in treatment.

Researchers are continuing to uncover important new information about the life cycle of the human immunodeficiency virus (HIV) and are further elucidating the products of the viral genome in their efforts to develop anti-retroviral therapies that are more effective and safer than those currently available. Although much attention has been focused on inhibiting proviral DNA synthesis with nucleoside analogues, other classes of agents are being explored that may enable clinicians to inhibit HIV transmission in vivo by targeting other stages of the viral life cycle. Among the novel approaches under investigation is inhibition of HIV protease, the proteolytic enzyme that is responsible for the cleavage of large precursor proteins in the budding virion. Preclinical studies indicate that protease inhibitors prevent the maturation of immature viral particles into infectious virions and thereby limit the spread of HIV in cell cultures. Laboratory data have also shown that these agents have good toxic-effect profiles, and recent improvements have resulted in compounds that are more bioavailable. As phase I studies of this modality are undertaken, clinical researchers will be carefully monitoring them to determine whether these favorable in vitro characteristics of protease inhibitors will be evident in the clinical arena as well.