Unique Thermodynamic Response of Tipranavir to Human Immunodeficiency Virus Type 1 Protease Drug Resistance Mutations

Abstract

Drug resistance is a major problem affecting the clinical efficacy of antiretroviral agents, including protease inhibitors, in the treatment of infection with human immunodeficiency virus type 1 (HIV-1)/AIDS. Consequently, the elucidation of the mechanisms by which HIV-1 protease inhibitors maintain antiviral activity in the presence of mutations is critical to the development of superior inhibitors. Tipranavir, a nonpeptidic HIV-1 protease inhibitor, has been recently approved for the treatment of HIV infection. Tipranavir inhibits wild-type protease with high potency (K i ‫؍‬ 19 pM) and demonstrates durable efficacy in the treatment of patients infected with HIV-1 strains containing multiple common mutations associated with resistance. The high potency of tipranavir results from a very large favorable entropy change (؊T⌬S ‫؍‬ ؊14.6 kcal/mol) combined with a favorable, albeit small, enthalpy change (⌬H ‫؍‬ ؊0.7 kcal/mol, 25°C). Characterization of tipranavir binding to wild-type protease, active site mutants I50V and V82F/I84V, the multidrug-resistant mutant L10I/ L33I/M46I/I54V/L63I/V82A/I84V/L90M, and the tipranavir in vitro-selected mutant I13V/V32L/L33F/K45I/ V82L/I84V was performed by isothermal titration calorimetry and crystallography. Thermodynamically, the good response of tipranavir arises from a unique behavior: it compensates for entropic losses by actual enthalpic gains or by sustaining minimal enthalpic losses when facing the mutants. The net result is a small loss in binding affinity. Structurally, tipranavir establishes a very strong hydrogen bond network with invariant regions of the protease, which is maintained with the mutants, including catalytic Asp25 and the backbone of Asp29, Asp30, Gly48 and Ile50. Moreover, tipranavir forms hydrogen bonds directly to Ile50, while all other inhibitors do so by being mediated by a water molecule.

Structural and Thermodynamic Basis of Amprenavir/Darunavir and Atazanavir Resistance in HIV-1 Protease with Mutations at Residue 50

“…Interestingly, we found that this variant had a 7.7-fold enhanced binding affinity for ATV (K d ϭ 0.03 nM versus 0.23 nM for WT). This is in contrast to the reduced affinity reported for the mutant with the I50V single mutation (32). Thus, the I50V/A71Vdouble mutation causes a reduced affinity for APV and DRV, while rendering the protease more susceptible to ATV.…”

Potent Inhibition of HIV-1 Replication by Novel Non-peptidyl Small Molecule Inhibitors of Protease Dimerization

“…GRL-06579A and GRL-98065 are also potent against multidrug resistant HIV-1 strains, and molecular modeling indicates that for multidrug-resistant clinical isolates, these inhibitors maintain many of the interactions to critical active site residues (26,36). TPV, which is active against HIV-1 carrying multidrug-resistant protease, also maintains critical hydrogen bond interactions with backbone atoms in the catalytic active site of mutant protease (43).…”

Kinetic and Thermodynamic Analysis of Dimerization Inhibitors Binding to HIV Protease Monomers by Surface Plasmon Resonance

“…Внедрение в клиническую практику 9 конкурентных ингибиторов протеазы ВИЧ (пВИЧ) явилось существенным прогрессом в лечении СПИДа [1,2]. Оценка энтальпии и энтропии образования молекулярных комплексов с помощью методов поверхностного плазмонного резонанса и изотермического калориметрического титрования внесли заметный вклад в разработку более эффективных конкурентных ингибиторов и их прототипов [3][4][5][6][7][8]. Однако широкое применение в клинической практике конкурентных ингибиторов пВИЧ стало приводить к появлению устойчивых вирусных штаммов [9].…”