ABSTRACT:
We report that GRL-0519, a novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI) containing
tris
-tetrahydrofuranylurethane (
tris
-THF) and a sulfonamide isostere, is highly potent against laboratory HIV-1 strains and primary clinical isolates (50% effective concentration [EC
50
], 0.0005 to 0.0007 μM) with minimal cytotoxicity (50% cytotoxic concentration [CC
50
], 44.6 μM). GRL-0519 blocked the infectivity and replication of HIV-1
NL4-3
variants selected by up to a 5 μM concentration of ritonavir, lopinavir, or atazanavir (EC
50
, 0.0028 to 0.0033 μM). GRL-0519 was also potent against multi-PI-resistant clinical HIV-1 variants isolated from patients who no longer responded to existing antiviral regimens after long-term antiretroviral therapy, highly darunavir (DRV)-resistant variants, and HIV-2
ROD
. The development of resistance against GRL-0519 was substantially delayed compared to other PIs, including amprenavir (APV) and DRV. The effects of nonspecific binding of human serum proteins on GRL-0519's antiviral activity were insignificant. Our analysis of the crystal structures of GRL-0519 (3OK9) and DRV (2IEN) with protease suggested that the
tris
-THF moiety, compared to the
bis
-THF moiety present in DRV, has greater water-mediated polar interactions with key active-site residues of protease and that the
tris
-THF moiety and paramethoxy group effectively fill the S2 and S2′ binding pockets, respectively, of the protease. The present data demonstrate that GRL-0519 has highly favorable features as a potential therapeutic agent for treating patients infected with wild-type and/or multi-PI-resistant variants and that the
tris
-THF moiety is critical for strong binding of GRL-0519 to the HIV protease substrate binding site and appears to be responsible for its favorable antiretroviral characteristics.