HIV-1 drug resistance in subjects with advanced HIV-1 infection in whom antiretroviral combination therapy is failing: a substudy of AIDS Clinical Trials Group Protocol 388

Compounds producing an effective combinatorial regimen for disruption of HIV-1 latency

Highly active antiretroviral therapy (HAART) has improved the outlook for the HIV epidemic, but does not provide a cure. The proposed “shock‐and‐kill” strategy is directed at inducing latent HIV reservoirs, which may then be purged via boosted immune response or targeting infected cells. We describe five novel compounds that are capable of reversing HIV latency without affecting the general T‐cell activation state. The new compounds exhibit synergy for reactivation of latent provirus with other latency‐reversing agents (LRAs), in particular ingenol‐3‐angelate/PEP005. One compound, designated PH02, was efficient at reactivating viral transcription in several cell lines bearing reporter HIV‐1 at different integration sites. Furthermore, it was capable of reversing latency in resting CD4⁺ T lymphocytes from latently infected aviremic patient cells on HAART, while producing minimal cellular toxicity. The combination of PH02 and PEP005 produces a strong synergistic effect for reactivation, as demonstrated through a quantitative viral outgrowth assay (qVOA), on CD4⁺ T lymphocytes from HIV‐1‐infected individuals. We propose that the PH02/PEP005 combination may represent an effective novel treatment for abrogating persistent HIV‐1 infection.

Clinical significance of human immunodeficiency virus type 1 replication fitness

The relative fitness of a variant, according to population genetics theory, is that variant's relative contribution to successive generations. Most drug-resistant human immunodeficiency virus type 1 (HIV-1) variants have reduced replication fitness, but at least some of these deficits can be compensated for by the accumulation of second-site mutations. HIV-1 replication fitness also appears to influence the likelihood of a drug-resistant mutant emerging during treatment failure and is postulated to influence clinical outcomes. A variety of assays are available to measure HIV-1 replication fitness in cell culture; however, there is no agreement regarding which assays best correlate with clinical outcomes. A major limitation is that there is no high-throughput assay that incorporates an internal reference strain as a control and utilizes intact virus isolates. Some retrospective studies have demonstrated statistically significant correlations between HIV-1 replication fitness and clinical outcomes in some patient populations. However, different studies disagree as to which clinical outcomes are most closely associated with fitness. This may be in part due to assay design, sample size limitations, and differences in patient populations. In addition, the strength of the correlations between fitness and clinical outcomes is modest, suggesting that, at present, it would be difficult to utilize these assays for clinical management.

Estimating the rate of accumulating drug resistance mutations in the HIV genome

OBJECTIVE

HIV mutation accumulation has great implications for pharmacoeconomics and clinical care, yet scarcity of data has hindered its representation in decision analytic models. Our objective is to determine the accuracy with which mutation accumulation and other unmeasured parameters could be estimated during model calibration.

METHODS

We used a second-order Monte Carlo simulation of HIV natural history that had been calibrated by varying two unmeasured parameters (mutation accrual rate and probability of adherence) to minimize differences between estimated and observed clinical outcomes (time to treatment failure and survival). We compared these estimated values first with only those results that had been already published at the time of model calibration, and second including results that were published after model calibration.

RESULTS

The value for mutation accrual rate assigned during calibration was 0.014 mutations per month for antiretroviral-naïve patients, at the lower bound of the results for nine heterogeneous studies published at the time of calibration (pooled 95% confidence interval [CI] 0.014-0.039 mutations per month). In contrast, this estimate accurately anticipated results from 11 larger and more homogeneous studies published after calibration (pooled 95% CI for antiretroviral-naïve patients, 0.012-0.015 mutations per month). The value for probability of adherence assigned during calibration (75%) was also within the range of published results (pooled 95% CI 62-76%).

CONCLUSION

Estimates for unobserved parameters derived during model calibration were not only within the range of clinical observations, but anticipated with accuracy clinical results that were not yet available. It may be feasible to use models to estimate unobserved parameters.

Neuropsychiatric side effects of efavirenz therapy

The non-nucleoside analogue inhibitor of the reverse transcriptase, efavirenz (EFV), has become commonly used in highly active antiretroviral combination therapy in the treatment of HIV infection. Although being effective in suppressing plasma viral load, neuropsychiatric side effects have been reported in individuals treated with EFV. There are early complications, such as acute psychosis resembling reactions to LSD intake, as well as nightmares occurring for several days up to 4 weeks after the start of therapy. Although LSD-like psychosis provokes the necessity of therapy discontinuation, the nightmares, as well as irritability and concentration problems in daily life, disappear after several weeks of treatment. Late complications are depressive episodes that must be carefully differentiated from pre-existing psychiatric disease and virus-induced brain damage. This review describes neuropsychiatric symptoms provoked by EFV, differential-diagnostic procedures and treatment options, and provides pro's and con's for EFV use in clinical practice with respect to drug safety.

Inhibition of human immunodeficiency virus type 1 reverse transcriptase, RNase H, and integrase activities by hydroxytropolones

Human immunodeficiency virus type I reverse transcriptase (RT) possesses distinct DNA polymerase and RNase H sites, whereas integrase (IN) uses the same active site to perform 3'-end processing and strand transfer of the proviral DNA. These four enzymatic activities are essential for viral replication and require metal ions. Two Mg2+ ions are present in the RT polymerase site, and one or two Mg2+ ions are required for the catalytic activities of RNase H and IN. We tested the possibility of inhibition of the RT polymerase and RNase H as well as the IN 3'-end processing and transfer activities of purified enzymes by a series of 3,7-dihydroxytropolones designed to target two Mg2+ ions separated by approximately 3.7 angstroms. The RT polymerase and IN 3' processing and strand transfer activities were inhibited at submicromolar concentrations, while the RNase H activity was inhibited in the low micromolar range. In all cases, the lack of inhibition by tropolones and O-methylated 3,7-dihydroxytropolones was consistent with the active molecules binding the metal ions in the active site. In addition, inhibition of the DNA polymerase activity was shown to depend on the Mg2+ concentration. Furthermore, selective inhibitors were identified for several of the activities tested, leaving some potential for design of improved inhibitors. However, all tested compounds exhibited cellular toxicity that presently limits their applications.