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, w hich 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 amou nt of the drug required to limit infection in vitro. In this study, ph ysiologically relevant concentrations of alpha(1) AGP and a radiolabel ed inhibitor, A-80987, were used to determine both the uptake and acti vity 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-80 987 were rapid (t1/2) <5 min). Uptake of the drug was linearly depende nt 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 proportio nal to the concentration of alpha(1) AGP (r(2), 0.99) and directly pro portional 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 directl y related to the amount of intracellular A-80987. This study demonstra tes that A-80987 binds to alpha(1) AGP, resulting in a free fraction b elow 10%. Cellular uptake of A-80987 is proportionally decreased in th e presence of alpha(1) AGP, which results in less-than-expected antivi ral activity, Importantly, we demonstrate for the first time that the inhibition of HIV protease is highly correlated with the amount of int racellular inhibitor.