ABSTRACT:
Despite the current success in HIV treatment with protease inhibitors, the emergence of resistant virus strains limits effectiveness of such compounds. The acquisition of mutations in HIV protease, especially in the active site regions, resulted in a high degree of cross-resistance towards many different protease inhibitors, including all clinically approved drugs. Using structure-based approach approaches a novel flexible core was designed to target some of the active site mutants. Using a continuous fluorogenic assay, we measured the inhibition constants for one such inhibitor, RS-344, towards wild-type and seven different drug-resistant mutant enzymes.
Inhibition constants were compared with those obtained for saquinavir, indinavir, ritonavir, nelfinavir, ampremavir and ABT378 (RS346). Compared to clinically approved drugs, RS-344 exhibited similar potency in both enzymatic and cell culture assays KI approx. 10 pm, IC50+23 nM). Our study shows that several HIV protease mutants containing the V82A (V82A, M46F/V82A, G48V/V82A) substitution, which usually show cross-resistance to many inhibitors in biochemical assays, remained sensitive to RS-344. For example, double mutant G48V/V82A exhibits 15-50-fold increase of KI toward saquinavir, indinavir, ritonavir, and nelfinavir, but was much more sensitive to RS-344 (<4-fold increase of KI).
Significantly lower KI changes were also observed for RS-344 in comparisons to clinically approved inhibitors towards other active site mutants including 184V, V82F/184V and G48V/lL90M. Overall, the biochemical resistance profile of RS-344 supports our idea that core flexibility is important in the design of resistance repellent inhibitors for HIV-1 protease.
