The new and less toxic protease inhibitor saquinavir-NO maintains anti-HIV-1 properties in vitro indistinguishable from those of the parental compound saquinavir

Although, the antiviral activity, tolerability and convenience of protease inhibitors have improved significantly in recent years, toxicity-associated adverse events including diarrhea, lipid alterations, disturbance of glucose homeostasis and liver enzyme elevations still remain a major concern during treatment of HIV-1 patients. We have recently shown that the covalent attachment of the NO moiety to the HIV-1 protease inhibitor saquinavir (Sag-NO) reduces its toxicity. In this study, we evaluated in vitro the anti-HIV activity of Sag-NO vs. its parental compound Sag. Site directed mutants with the most frequently identified Sag associated resistance mutations and their combinations were generated on proviral ADS-based backbones. Phenotypic assays were conducted using wild type clinical isolates and fully replicating recombinant viruses with Saq and Sag-NO in parallel on purified CD4+ T cells. The following recombinant viruses were generated and tested: L33F, M461, G48V, I54V, I84V + L90M, M46I + L90M, G48V + L90M, M46I + I54V + L90M, L33F + M46I + L90M. The fold change resistance compared to the wild type viruses was between 1.3 and 7 for all single mutants, between 3.4 and 20 for double mutants and between 16.7 and 28.5 for viruses carrying three mutations for both compounds. The results clearly demonstrate that Sag-NO maintains an anti-HIV-1 profile very similar to that of Sag. The possibility to reduce Sag associated side effects and to increase the concentration of the drug in vivo may allow a higher and possibly more effective dosage of Sag-NO in HIV-1-infected patients and to increase the genetic barrier of this PI thus impairing the selection of resistant clones. (C) 2011 Elsevier B.V. All rights reserved.