New antiretroviral drugs: a review of the efficacy, safety, pharmacokinetics, and resistance profile of tipranavir, darunavir, etravirine, rilpivirine, maraviroc, and raltegravir

Modelling the impact of treatment with individual antiretrovirals

PURPOSE OF REVIEW

The aim of this paper is to review the recent literature on HIV mathematical models that evaluate the effect of antiretroviral treatment on mortality, morbidity, HIV and other key outcomes. The focus of our attention is models which explicitly model specific effects of individual antiretroviral drugs.

RECENT FINDINGS

The number of studies that use mathematical models to evaluate the impact of antiretroviral drugs as a treatment or prevention strategy is increasing.Many mathematical models are deterministic compartmental models, and do not have the level of detail of specific effects of individual drugs. However, models that include specific antiretroviral drugs have been increasingly employed to assess the cost-effectiveness of prevention interventions, to evaluate benefits and harms (toxicities, side-effects, resistance development) of different regimens and different intervention timing and to predict long-term outcomes of randomized controlled trials (RCTs) that are not usually measured in the time frame of a trial.

SUMMARY

The number of models that consider specific antiretroviral drugs, with their own peculiarities, is limited. This factor is particularly the case for dynamic individual-based stochastic models. In order to address some research questions it is necessary to accurately take into consideration implications of toxicities, side-effects, and resistance acquisition, and hence to model specific drugs or at least specific drug classes.

Hypersensitivity reactions to HIV therapy

Many drugs used for the treatment of HIV disease (including the associated opportunistic infections) can cause drug hypersensitivity reactions, which vary in severity, clinical manifestations and frequency. These reactions are not only seen with the older compounds, but also with the newer more recently introduced drugs. The pathogenesis is unclear in most cases, but there is increasing evidence to support that many of these are mediated through a combination of immunologic and genetic factors through the major histocompatibility complex (MHC). Genetic predisposition to the occurrence of these allergic reactions has been shown for some of the drugs, notably abacavir hypersensitivity which is strongly associated with the class I MHC allele, HLA-B*5701. Testing before the prescription of abacavir has been shown to be of clinical utility, has resulted in a change in the drug label, is now recommended in clinical guidelines and is practiced in most Western countries. For most other drugs, however, there are no good methods of prevention, and clinical monitoring with appropriate (usually supportive and symptomatic) treatment is required. There is a need to undertake further research in this area to increase our understanding of the mechanisms, which may lead to better preventive strategies through the development of predictive genetic biomarkers or through guiding the design of drugs less likely to cause these types of adverse drug reactions.

Use of antineoplastic agents in patients with cancer who have HIV/AIDS

Highly active antiretroviral therapy (HAART) has substantially reduced morbidity and mortality of AIDS-related complications in patients with HIV; however, the prevalence of AIDS-defining cancers and non-AIDS-defining cancers has increased. In this Review we discuss the management of HAART pharmacotherapy in relation to cytotoxic chemotherapy or targeted antineoplastic agents. We will review potential pharmacological interactions between antiretroviral and antineoplastic therapies and consider how to combine antiretroviral and antineoplastic agents in patients with HIV who are receiving HAART therapy.

Safety, efficacy, and pharmacokinetics of rilpivirine: systematic review with an emphasis on resource-limited settings

The vast majority of people living with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome reside in the developing world, in settings characterized by limited health budgets, critical shortages of doctors, limited laboratory monitoring, a substantial burden of HIV in children, and high rates of coinfection, in particular tuberculosis. Therefore, the extent to which new antiretrovirals will contribute to improvements in the management of HIV globally will depend to a large extent on their affordability, ease of use, low toxicity profile, availability as pediatric formulations, and compatibility with tuberculosis and other common drugs. We undertook a systematic review of the available evidence regarding drug interactions, and the efficacy and safety of rilpivirine (also known as TMC-278), and assessed our findings in view of the needs and constraints of resource-limited settings. The main pharmacokinetic interactions relevant to HIV management reported to date include reduced bioavailability of rilpivirine when coadministered with rifampicin, rifabutin or acid suppressing agents, and reduced bioavailability of ketoconazole. Potential recommendations for dose adjustment to compensate for these interactions have not been elaborated. Trials comparing rilpivirine and efavirenz found similar outcomes up to 96 weeks in intent-to-treat analysis; failure of rilpivirine was mainly virological, whereas failure among those exposed to efavirenz was mainly related to the occurrence of adverse events. Around half of the patients who fail rilpivirine develop non-nucleoside reverse transcriptase inhibitor resistance mutations. The incidence of Grade 2–4 events was lower for rilpivirine compared with efavirenz. Grade 3–4 adverse events potentially related to the drugs were infrequent and statistically similar for both drugs. No dose-response relationship was observed for efficacy or safety, and the lowest dose (25 mg) was selected for further clinical development. The potential low cost and dose of the active pharmaceutical ingredient means that rilpivirine can potentially be manufactured at a low price. Moreover, its long half-life suggests the potential for monthly dosing via nonoral routes, with promising early results from studies of a long-acting injectable formulation. These characteristics make rilpivirine an attractive drug for resource-limited settings. Future research should assess the potential to improve robustness and assess the clinical significance of interaction with antituberculosis drugs.

HIV protease inhibitors and obesity

PURPOSE OF REVIEW

To review the current scientific literature and recent clinical trials on HIV protease inhibitors and their potential role in the pathogenesis of lipodystrophy and metabolic disorders.

RECENT FINDINGS

HIV protease inhibitor treatment may affect the normal stimulatory effect of insulin on glucose and fat storage. Further, chronic inflammation from HIV infection and protease inhibitor treatment trigger cellular homeostatic stress responses with adverse effects on intermediary metabolism. The physiologic outcome is such that total adipocyte storage capacity is decreased, and the remaining adipocytes resist further fat storage. This process leads to a pathologic cycle of lipodystrophy and lipotoxicity, a proatherogenic lipid profile, and a clinical phenotype of increased central body fat distribution similar to the metabolic syndrome.

SUMMARY

Protease inhibitors are a key component of antiretroviral therapy and have dramatically improved the life expectancy of HIV-infected individuals. However, they are also associated with abnormalities in glucose/lipid metabolism and body fat distribution. Further studies are needed to better define the pathogenesis of protease inhibitor-associated metabolic and body fat changes and their potential treatment.

Prevention of HIV protease inhibitor-induced dysregulation of hepatic lipid metabolism by raltegravir via endoplasmic reticulum stress signaling pathways

Hyperlipidemia associated with the HIV protease inhibitor (PI), the major component of highly active antiretroviral treatment (HAART) for HIV infection, has stimulated interest in developing new agents that minimize these side effects in the clinic. HIV integrase inhibitor is a new class of anti-HIV agents. Raltegravir is a first-in-its-class oral integrase inhibitor and has potent inhibitory activity against HIV-1 strains that are resistant to other antiretroviral regimens. Our previous studies have demonstrated that HIV PI-induced endoplasmic reticulum (ER) stress links to dysregulation of lipid metabolism. However, little information is available as to whether raltegravir would have similar effects as the HIV PIs. In this study, we examined the effect of raltegravir on lipid metabolism both in primary rat hepatocytes and in in vivo mouse models, and we further determined whether the combination of raltegravir with existing HIV PIs would potentially exacerbate or prevent the previously observed development of dyslipidemia. The results indicated that raltegravir did not induce ER stress or disrupt lipid metabolism either in vitro or in vivo. However, HIV PI-induced ER stress and lipid accumulation were significantly inhibited by raltegravir both in in vitro primary rat hepatocytes and in in vivo mouse liver. High-performance liquid chromatography analysis further demonstrated that raltegravir did not affect the uptake and metabolism of HIV PIs in hepatocytes. Thus, raltegravir has less hepatic toxicity and could prevent HIV PI-induced dysregulation of lipid metabolism by inhibiting ER stress. These results suggest that incorporation of this HIV integrase inhibitor may reduce the side effects associated with current HAART.

Nonnucleoside reverse transcriptase inhibitor resistance and the role of the second-generation agents

OBJECTIVE

To review the current state of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance, discuss the promising role of second-generation NNRTIs, and provide insight into their clinical utility.

DATA SOURCES

Articles were identified through searches of MEDLINE (May 2000-August 2009) and International Pharmaceutical Abstracts (May 1998-August 2009), using the key words etravirine, rilpivirine, TMC125, TMC278, diarylpyrimidine, NNRTI, and resistance.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials, resistance studies, and pharmacokinetic data were selected for review.

DATA SYNTHESIS

NNRTIs are an integral class of antiretroviral agents utilized for the treatment of HIV-1 infection. These agents have become preferred therapy options for treatment-naïve individuals per treatment guideline recommendations and have gained increased popularity over protease inhibitor-based antiretroviral therapy. However, available NNRTIs possess inherent characteristics, such as low genetic barrier to resistance and high degree of cross-resistance, that limit their use in HIV therapy. Due to the growing utilization of this highly efficacious antiretroviral class and the increased capability for resistance development, many HIV-infected patients have experienced treatment failure of an NNRTI. Cross-resistance makes other first-generation NNRTI agents unavailable for future use. Etravirine and rilpivirine are second-generation NNRTIs that are not significantly hampered by cross-resistance and possess potent antiretroviral activity against current NNRTI-resistant viral strains. These agents provide new and important therapy options for many HIV-infected patients.

CONCLUSIONS

NNRTI resistance is an increasing problem that may impair the chances for therapeutic success in HIV-infected patients. Novel agents such as etravirine and rilpivirine provide new, sensitive options for patients and significantly improve the rate of virologic suppression when appropriately applied.