Analysis of low-frequency mutations associated with drug resistance to raltegravir before antiretroviral treatment.

Raltegravir is highly efficacious in the treatment of HIV-1 infection. The prevalence and impact on virologic outcome of low-frequency resistant mutations among HIV-1-infected patients not previously treated with raltegravir have not been fully established. Samples from HIV treatment-experienced patients entering a clinical trial of raltegravir treatment were analyzed using a parallel allele-specific sequencing (PASS) assay that assessed six primary and six secondary integrase mutations. Patients who achieved and sustained virologic suppression (success patients, n = 36) and those who experienced virologic rebound (failure patients, n = 35) were compared. Patients who experienced treatment failure had twice as many raltegravir-associated resistance mutations prior to initiating treatment as those who achieved sustained virologic success, but the difference was not statistically significant. The frequency of nearly all detected resistance mutations was less than 1% of viral population, and the frequencies of mutations between the success and failure groups were similar. Expansion of pre-existing mutations (one primary and five secondary) was observed in 16 treatment failure patients in whom minority resistant mutations were detected at baseline, suggesting that they might play a role in the development of drug resistance. Two or more mutations were found in 13 patients (18.3%), but multiple mutations were not present in any single viral genome by linkage analysis. Our study demonstrates that low-frequency primary RAL-resistant mutations were uncommon, while minority secondary RAL-resistant mutations were more frequently detected in patients naïve to raltegravir. Additional studies in larger populations are warranted to fully understand the clinical implications of these mutations.

Long-term efficacy and safety of the HIV integrase inhibitor raltegravir in patients with limited treatment options in a Phase II study.

BACKGROUND: Raltegravir in combination therapy has demonstrated potent suppression of HIV-1 with a favorable safety profile. This report provides 96-week efficacy and safety data from Protocol 005, a Phase II study. METHODS: HIV-infected patients with very limited treatment options and failing antiretroviral therapy were randomized to raltegravir 200, 400, or 600 mg or placebo b.i.d., plus optimized background therapy for >or=24 weeks; all patients were then offered open-label raltegravir 400 mg b.i.d. Efficacy measurements included changes in viral load and CD4 count from baseline and percent of patients with HIV-1 RNA <400 and <50 copies/mL. RESULTS: One hundred and thirty-three patients received raltegravir and 45 received placebo. No dose-dependent differentiation in the safety or antiviral activity of raltegravir was observed during the double-blind phase. For the combined raltegravir groups, mean change in viral load from baseline was -1.60 log10 copies/mL at week 48 and -1.38 log10 copies/mL at week 96 (observed failure approach). At week 48, HIV-1 RNA levels were <400 copies/mL in 68% of raltegravir recipients and <50 copies/mL in 55%; these levels were maintained in 55% and 48% of raltegravir recipients, respectively, at week 96 (noncompleter = failure). There were few discontinuations of raltegravir (4%) due to adverse events. CONCLUSIONS: In patients with limited treatment options, raltegravir with OBT had a potent and sustained antiretroviral effect and was generally well tolerated through 96 weeks.

Loss of raltegravir susceptibility by human immunodeficiency virus type 1 is conferred via multiple nonoverlapping genetic pathways.

The human immunodeficiency virus type 1 (HIV-1) integrase mutations N155H and Q148R(H)(K) that reduce susceptibility to the integrase inhibitor raltegravir have been identified in patients failing treatment regimens containing raltegravir. Whether these resistance mutations occur individually or in combination within a single virus genome has not been defined, nor do we fully understand the impact of these primary mutations and other secondary mutations on raltegravir susceptibility and viral replication capacity. To address these important questions, we investigated the raltegravir susceptibility and replication capacity of viruses containing mutations at positions 155 and 148 separately or in combination with secondary mutations selected in subjects failing treatment regimens containing raltegravir. Clonal analysis demonstrated that N155H and Q148R(H)(K) occur independently, not in combination. Viruses containing a Q148R(H)(K) mutation generally displayed larger reductions in raltegravir susceptibility than viruses with an N155H mutation. Analysis of site-directed mutants indicated that E92Q in combination with N155H resulted in a higher level of resistance to raltegravir than N155H alone. Viruses containing a Q148R(H) mutation together with a G140S mutation were more resistant to raltegravir than viruses containing a Q148R(H) mutation alone; however, viruses containing G140S and Q148K were more susceptible to raltegravir than viruses containing a Q148K mutation alone. Both N155H and Q148R(H)(K) mutations reduced the replication capacity, while the addition of secondary mutations either improved or reduced the replication capacity depending on the primary mutation. This study demonstrates distinct genetic pathways to resistance in subjects failing raltegravir regimens and defines the effects of primary and secondary resistance mutations on raltegravir susceptibility and replication capacity.

Sustained antiretroviral effect of raltegravir after 96 weeks of combination therapy in treatment-naive patients with HIV-1 infection.

OBJECTIVES: The purpose of this study was to evaluate the safety and efficacy of raltegravir vs efavirenz-based antiretroviral therapy after 96 weeks in treatment-naive patients with HIV-1 infection. METHODS: Multicenter, double-blind, randomized study of raltegravir (100, 200, 400, or 600 mg twice a day) vs efavirenz (600 mg every day), both with tenofovir/lamivudine (TDF/3TC), for 48 weeks, after which raltegravir arms were combined and all dosed at 400 mg twice a day. Eligible patients had HIV-1 RNA > or =5000 copies per milliliter and CD4 T cells > or =100 cells per microliter. RESULTS: One hundred ninety-eight patients were randomized and treated; 160 received raltegravir and 38 received efavirenz. At week 96, 84% of patients in both groups achieved HIV-1 RNA <400 copies per milliliter; 83% in the raltegravir group and 84% in the efavirenz group achieved <50 copies per milliliter (noncompleter = failure). Both groups showed similar increases in CD4 T cells (221 vs 232 cells/uL, respectively). An additional 2 patients (1 in each group) met the protocol definition of virologic failure between weeks 48 and 96; no known resistance mutations were observed in the raltegravir recipient; the efavirenz recipient had nucleoside reverse transcriptase inhibitor and nonnucleoside reverse transcriptase inhibitor resistance mutations. Investigator reported drug-related clinical adverse events (AEs) were less frequent with raltegravir (51%) than efavirenz (74%). Drug-related AEs occurring in >10% of patients in either group were nausea in both groups and dizziness and headache in the efavirenz group. Laboratory AEs remained infrequent. Raltegravir had no adverse effect on total or low-density lipoprotein cholesterol or on triglycerides. Neuropsychiatric AEs remained less frequent with raltegravir (34%) than efavirenz (58%). There were no drug-related serious AEs in patients receiving raltegravir. CONCLUSIONS: In antiretroviral therapy-naive patients, raltegravir with TDF/3TC had potent antiretroviral activity, which was similar to efavirenz/TDF/3TC and was sustained to week 96. Raltegravir was generally well tolerated; drug-related AEs were less frequent in patients treated with raltegravir compared with efavirenz.

Selection and analysis of HIV-1 integrase strand transfer inhibitor resistant mutant viruses.

This report describes methods for the selection and analysis of antiretroviral resistance to HIV integrase strand transfer inhibitors (InSTIs) in cell culture. The method involves the serial passage of HIV-1 in the presence of increasing concentrations of test inhibitors, followed by the cloning and sequencing of the integrase coding region from the selected viruses. The identified mutations are subsequently re-engineered into a reference wild-type molecular clone, and the resulting replication capacity and level of drug resistance are determined relative to the wild-type virus. Here we describe examples of selection and analysis of InSTI-resistant viruses using four integrase inhibitors from three structurally distinct chemical classes; a diketo acid, two naphthyridines, and a pyrimidinecarboxamide. Each inhibitor selected an independent route to resistance. Interestingly, the shift in the IC50 required to suppress the re-engineered resistant mutant viruses closely matched the concentration of compound used during the selection of drug resistance.

Integrase inhibitors and cellular immunity suppress retroviral replication in rhesus macaques.

We describe the efficacy of L-870812, an inhibitor of HIV-1 and SIV integrase, in rhesus macaques infected with the simian-human immunodeficiency virus (SHIV) 89.6P. When initiated before CD4 cell depletion, L-870812 therapy mediated a sustained suppression of viremia, preserving CD4 levels and permitting the induction of virus-specific cellular immunity. L-870812 was also active in chronic infection; however, the magnitude and durability of the effect varied in conjunction with the pretreatment immune response and viral load. These studies demonstrate integrase inhibitor activity in vivo and suggest that cellular immunity facilitates chemotherapeutic efficacy in retroviral infections.

A naphthyridine carboxamide provides evidence for discordant resistance between mechanistically identical inhibitors of HIV-1 integrase.

The increasing incidence of resistance to current HIV-1 therapy underscores the need to develop antiretroviral agents with new mechanisms of action. Integrase, one of three viral enzymes essential for HIV-1 replication, presents an important yet unexploited opportunity for drug development. We describe here the identification and characterization of L-870,810, a small-molecule inhibitor of HIV-1 integrase with potent antiviral activity in cell culture and good pharmacokinetic properties. L-870,810 is an inhibitor with an 8-hydroxy-(1,6)-naphthyridine-7-carboxamide pharmacophore. The compound inhibits HIV-1 integrase-mediated strand transfer, and its antiviral activity in vitro is a direct consequence of this ascribed effect on integration. L-870,810 is mechanistically identical to previously described inhibitors from the diketo acid series; however, viruses selected for resistance to L-870,810 contain mutations (integrase residues 72, 121, and 125) that uniquely confer resistance to the naphthyridine. Conversely, mutations associated with resistance to the diketo acid do not engender naphthyridine resistance. Importantly, the mutations associated with resistance to each of these inhibitors map to distinct regions within the integrase active site. Therefore, we propose a model of the two inhibitors that is consistent with this observation and suggests specific interactions with discrete binding sites for each ligand. These studies provide a structural basis and rationale for developing integrase inhibitors with the potential for unique and nonoverlapping resistance profiles.

Treatment with indinavir, efavirenz, and adefovir after failure of nelfinavir therapy.

A prospective, open-label study was conducted to assess the response to indinavir, efavirenz, and adefovir in human immunodeficiency virus (HIV)-infected patients experiencing viral rebound while receiving therapy with nelfinavir-containing regimens, to determine whether the protease genotype influenced the outcome of the salvage regimen. Genotyping from 29 nelfinavir failures revealed D30N in 17 (59%) and L90M in 11 (38%) cases. Suppression to <400 viral RNA copies/mL was achieved at week 48 in 56% of patients with the D30N virus versus 18% of patients with the L90M virus.