A drug interaction study investigating the effect of Rifabutin on the pharmacokinetics of Maraviroc in healthy subjects

Effects of steady-state rifabutin on the pharmacokinetics of steady-state maraviroc were investigated in fourteen healthy adult female and male volunteers. Maraviroc 300 mg twice daily (BID) was given orally with food for fifteen days. On day six, rifabutin 300 mg once daily (QD, P.O.) was added to the regimen. Formal pharmacokinetic (PK) sampling was performed on days five and fifteen. Individual plasma drug concentration-time data for maraviroc, and rifabutin on day fifteen, were obtained using validated High Performance Liquid Chromatography (HPLC) tandem Mass Spectrometry (MS/MS). Rifabutin steady state exposure was comparable to data in the literature. Maraviroc area under the curve (AUC) and minimum plasma concentration (C_last or C_min) were reduced by 17% and 30% respectively when co-administered with rifabutin. No unexpected or serious adverse eventsoccurred. Based on the reduced exposure of maraviroc observed in this study, increasing the dose of maraviroc may be studied to normalize its moderately reduced exposure following rifabutin co-administration, a moderate inducer of CYP3A4.

Chemokine receptor CCR5 antagonist maraviroc: medicinal chemistry and clinical applications

The human immunodeficiency virus (HIV) causes acquired immumodeficiency syndrome (AIDS), one of the worst global pandemic. The virus infects human CD4 T cells and macrophages, and causes CD4 depletion. HIV enters target cells through the binding of the viral envelope glycoprotein to CD4 and the chemokine coreceptor, CXCR4 or CCR5. In particular, the CCR5-utilizing viruses predominate in the blood during the disease course. CCR5 is expressed on the surface of various immune cells including macrophages, monocytes, microglia, dendric cells, and active memory CD4 T cells. In the human population, the CCR5 genomic mutation, CCR5Δ32, is associated with relative resistance to HIV. These findings paved the way for the discovery and development of CCR5 inhibitors to block HIV transmission and replication. Maraviroc, discovered as a CCR5 antagonist, is the only CCR5 inhibitor that has been approved by both US FDA and the European Medicines Agency (EMA) for treating HIV/AIDS patients. In this review, we summarize the medicinal chemistry and clinical studies of Maraviroc.

Ageing with HIV: a multidisciplinary review

INTRODUCTION

After the introduction of highly active antiretroviral treatment, the course of HIV infection turned into a chronic disease and most of HIV-positive patients will soon be over 50 years old.

MATERIAL AND METHODS

This paper reviews the multiple aspects that physicians have to face while taking care of HIV-positive ageing patients including the definitions of frailty and the prevalence and risk factors of concomitant diseases. From a therapeutic point of view pharmacokinetic changes and antiretroviral-specific toxicities associated with ageing are discussed; finally therapeutic approaches to frailty are reviewed both in HIV-positive and negative patients.

CONCLUSION AND DISCUSSION

We conclude by suggesting that the combined use of drugs with the least toxicity potential and the promotion of healthy behaviours (including appropriate nutrition and exercise) might be the best practice for ageing HIV-positive subjects.

Safety, efficacy and indications of prescription of maraviroc in clinical practice: Factors associated with clinical outcomes

Maraviroc is approved for treatment-experienced HIV+ adults in twice-daily administration. Limited data are available on safety, efficacy and use in routine clinical practice, outside of restrictive clinical trials. This retrospective multicenter (27 centers) study included 667 subjects starting a regimen with maraviroc. The primary endpoint was plasma HIV-RNA <50copies/mL and CD4(+) cell count change at 48 and 96weeks (FDA snapshot analysis). 94.4% had CCR5 tropism (58.3% Trofile™, 29.2% population genotype, and 12% genotyping proviral DNA). Half of the subjects received the drug in scenarios or dosages outside the initial approval. Maraviroc was prescribed for salvage in 346 (51.9%) individuals, as a switch strategy due to toxicity in 135 (38.7%), for immune discordance in 75 (11.2%), and for simplification in 48 (7.2%). After salvage therapy, 223 (64.5%) subjects had HIV-RNA <50copies/mL at 48weeks, and 178 (51.4%) at 96weeks. Darunavir/r was included in 224 (64.7%) subjects and associated with higher rates of virological and immunologic efficacy (p<0.001). In multivariate analysis MSM (OR 2.25; 95%CI 1.29-3.94) and baseline HIV-RNA <100,000copies/mL (OR 1.96; 1.06-3.70) were associated with virological suppression. An increase in CD4(+) counts was seen at 48 and 96weeks in subjects with immune discordance (p<0.001). Maraviroc was used once-daily in 142 (21.3%) subjects overall, and 68 (57.4%) in switch/simplification. No new safety signals were identified. Besides in salvage regimens, maraviroc was frequently used in switch due to toxicity, simplification, and immune discordance. The efficacy in salvage in clinical practice was higher than in phase III clinical trials, likely due to availability of new active drugs in the regimen. These results increase our understanding of the efficacy, safety, and conditions of prescription of maraviroc beyond the initial registrational trials and the early manufacturer pharmacovigilance programs.

Maraviroc 150 mg daily plus lopinavir/ritonavir, a nucleoside/nucleotide reverse transcriptase inhibitor-sparing regimen for HIV-infected naive patients: 48-week final results of VEMAN study

Non-conventional strategies with nucleoside/nucleotide reverse transcriptase inhibitor-sparing regimens in antiretroviral naive human immunodeficiency virus (HIV) -infected patients have been explored in clinical trials. A prospective, open-label, randomized (1:1), multicentre, proof-of-concept trial (VEMAN study, EUDRACT number 2008-006287-11) was conducted assigning HIV-infected naive patients to once-daily maraviroc plus lopinavir/ritonavir (MVC group) or to tenofovir/emtricitabine plus lopinavir/ritonavir (TDF/FTC group). Clinical and laboratory data were collected at baseline, and after 4, 12, 24, 36 and 48 weeks with the objective to evaluate the 48-week virological and immunological efficacy. HIV-1 DNA load and CD4(+) T-cell subsets were analysed on frozen peripheral blood mononuclear cells collected at baseline, 4 and 48 weeks to explore the trend in HIV reservoirs. Fifty patients were randomized and included in the analysis. During follow up, HIV-1 RNA decreased similarly in both groups and, at week 48, all patients in the MVC group and 22/24 (96%) in the TDF/FTC group had < 50 copies/ml of HIV-1 RNA. CD4(+) trend during follow up was higher in maraviroc-treated patients (MVC group: 286 (183-343) versus TDF/FTC group: 199 (125-285); Mann-Whitney U-test: p 0.033). A significant 48-week increase of CCR5(+) CD4(+) T cells and CD4(+) effector memory cells was observed among maraviroc-treated patients (Wilcoxon signed rank test: p 0.016 and p 0.007, respectively). No significant variations were found in naive and central memory CD4(+) T cells. Among naive patients with an R5 virus, treatment with maraviroc and lopinavir/ritonavir was shown to provide a virological response compared to a triple therapy and a greater immunological benefit.

Intracellular accumulation of atazanavir/ritonavir according to plasma concentrations and OATP1B1, ABCB1 and PXR genetic polymorphisms

OBJECTIVES

The rate of accumulation of atazanavir and ritonavir within cells is still debated due to methodological limitations. Our aim was to measure peripheral blood mononuclear cell (PBMC) concentrations of atazanavir and ritonavir and investigate whether single-nucleotide polymorphisms of OATP, ABCB1, CYP3A4 and PXR genes are involved in intracellular drug penetration.

METHODS

HIV-positive patients administered 300 mg of atazanavir/100 mg of ritonavir were enrolled. Blood sampling was performed at the end of the dosing interval (Ctrough). PBMC-associated and plasma atazanavir and ritonavir concentrations were measured by validated HPLC coupled with a single mass detector (HPLC-MS) and HPLC-photodiode array (PDA) methods, respectively. Cell count and mean cellular volume were determined using a Coulter counter. Genotyping was conducted using real-time PCR.

RESULTS

Thirty-five patients were enrolled. Median atazanavir and ritonavir intracellular concentrations were 1844 and 716 ng/mL, respectively. Median plasma concentrations were 645 ng/mL for atazanavir and 75 ng/mL for ritonavir, while median intracellular/plasma concentration ratios were 2.4 and 9.2, respectively. Median ritonavir intracellular concentrations were higher for OATP1B1 521 T→C TC or CC carriers and for PXR 44477 A→G AG or GG carriers. Atazanavir intracellular/plasma concentration ratios were higher in patients GG for the ABCB1 2677 G→T single-nucleotide polymorphism (SNP) compared with GT and TT groups.

CONCLUSIONS

Our study showed a higher intracellular ritonavir accumulation than previously reported. Ritonavir intracellular concentrations were associated with OATP1B1 521 and PXR 44477 SNPs while intracellular atazanavir exposure was associated with the ABCB1 2677 SNP. Further clinical studies are necessary in order to confirm these data.