Antiviral and resistance studies of AG1343, an orally bioavailable inhibitor of human immunodeficiency virus protease

AG1343 ([3S-(3R*, 4aR*, 8aR*, 2'S*, 3'S*)]-2-[2' hydroxy-3'-phenylthiomethyl-4'-aza-5'-oxo-5'-(2 ''-methyl-3 ''-hydroxy-phenyl)pentyl]-decahydroiso-quinoline-3-N-t-butylcarboxamide methanesulfonic acid) is a selective, nonpeptidic inhibitor of human immunodeficiency virus (HIV) protease (K-i = 2 nM) that was discovered by protein structure-based drug design methodologies, AG1343 was effective against the replication of several laboratory and clinical HIV type 1 (HIV-1) or HIV-2 isolates including pyridinone- and zidovudine-resistant strains, with 50% effective concentrations ranging from 9 to 60 nM, In reversibility studies, inhibition of gag (p55) proteolytic processing in HIV-1 particles from cells treated with AG1343 was maintained for up to 36 h after drug removal, The ability of virus to develop resistance to AG1343 was studied by serial passage of HIV-1 NL4.3 in the presence of increasing concentrations of drug, After 28 passages, a variant with a 30-fold reduction in susceptibility to AG1343 was isolated, Molecular analysis of the protease from this variant indicated a double change from a Met to Ile at residue 46 and an Ile to Val or Ala at residue 84 (M46I + I84V A), Consistent with these findings, reductions in susceptibility were observed for recombinant viruses constructed to contain the single I84V change or the double M46I + I84V substitutions, Resistance, however, was not detected for recombinant viruses containing other key mutations in HIV-1 protease, including a Val to Ile change at residue 32 or a Val to Ala or Phe at residue 82, The potent anti-HIV activity of AG1343 against several isolates suggests that AG1343 should perform well during ongoing human phase II clinical trials.