Human serum alpha(1) acid glycoprotein reduces uptake, intracellular concentration, and antiviral activity of A-80987, an inhibitor of the human immunodeficiency virus type 1 protease

The therapeutic utility of a human immunodeficiency virus type 1 (HIV-1) protease inhibitor may depend on its intracellular concentration, which is a property of its uptake, metabolism, and/or efflux. Previous studies in our laboratory indicated that the addition of alpha(1) acid glycoprotein (alpha(1) AGP) to the medium markedly increased the amount of the drug required to limit infection in vitro. In this study, physiologically relevant concentrations of alpha(1) AGP and a radiolabeled inhibitor, A-80987, were used to determine both the uptake and activity of the agent in HIV-1-infected human peripheral blood mononuclear cells and cell lines, Both the uptake and efflux of C-14-labeled A-80987 were rapid (t1/2) <5 min). Uptake of the drug was linearly dependent on the concentration but insensitive to the metabolic inhibitors KF, sodium cyanide, or CCCP (carbonyl cyanide m-chlorophenyl hydrazone), The amount of A-80987 which entered the cells was inversely proportional to the concentration of alpha(1) AGP (r(2), 0.99) and directly proportional to the amount of extracellular non-protein-bound drug (r(2), 0.99). Most importantly, the antiviral activity of the drug in HIV-l-infected peripheral blood mononuclear cells and MT-2 cells was directly related to the amount of intracellular A-80987. This study demonstrates that A-80987 binds to alpha(1) AGP, resulting in a free fraction below 10%. Cellular uptake of A-80987 is proportionally decreased in the presence of alpha(1) AGP, which results in less-than-expected antiviral activity, Importantly, we demonstrate for the first time that the inhibition of HIV protease is highly correlated with the amount of intracellular inhibitor.