GRL-079, a novel HIV-1 protease inhibitor, is extremely potent against multidrug-resistant HIV-1 variants and has a high genetic barrier against the emergence of resistant variants

We identified four novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs), GRL-078, -079, -077, and -058, containing an alkylamine at the C-5 position of P2 tetrahydropyrano-tetrahydrofuran (Tp-THF) and a P2= cyclopropyl (Cp) (or isopropyl)-aminobenzothiazole (Abt) moiety. Their 50% effective concentrations (EC₅₀s) were 2.5 to 30 nM against wild-type HIV-1_NL4-3, 0.3 to 6.7 nM against HIV-2_EHO, and 0.9 to 90 nM against laboratory-selected PI-resistant HIV-1 and clinical HIV-1 variants resistant to multiple FDA-approved PIs (HIV_MDR). GRL-078, -079, -077, and -058 also effectively blocked the replication of HIV-1 variants highly resistant to darunavir (DRV) (HIV_DRV^r_p51), with EC₅₀s of 38, 62, 61, and 90 nM, respectively, while four FDA-approved PIs examined (amprenavir, atazanavir, lopinavir [LPV], and DRV) had virtually no activity (EC₅₀s of >1,000 nM) against HIV_DRV^r_p51. Structurally, GRL-078, -079, and -058 form strong hydrogen bond interactions between Tp-THF modified at C-5 and Asp29/Asp30/Gly48 of wild-type protease, while the P2= Cp-Abt group forms strong hydrogen bonds with Asp30=. The Tp-THF and Cp-Abt moieties also have good nonpolar interactions with protease residues located in the flap region. For selection with LPV and DRV by use of a mixture of 11 HIV_MDR strains (HIV_11MIX), HIV_11MIX became highly resistant to LPV and DRV over 13 to 32 and 32 to 41 weeks, respectively. However, for selection with GRL-079 and GRL-058, HIV_11MIX failed to replicate at >0.08 μM and >0.2 μM, respectively. Thermal stability results supported the highly favorable anti-HIV-1 potency of GRL-079 as well as other PIs. The present data strongly suggest that the P2 Tp-THF group modified at C-5 and the P2= Abt group contribute to the potent anti-HIV-1 profiles of the four PIs against HIV-1_NL4-3 and a wide spectrum of HIV_MDR strains.