Extravirologic modulation of immune response by an NRTI-sparing antiretroviral regimen including darunavir and maraviroc

Dual therapies, including protease inhibitor + maraviroc (MVC), may represent an alternative to traditional regimens for management of HIV infection. The aim of this in vitro study was to assess the effects of darunavir (DRV) alone or in combination with MVC on cell apoptosis and chemotaxis. A significant decrease of cell apoptosis was found after DRV treatment. The addition of MVC to DRV also had an in vitro down-regulating effect on cell migration. The combination of an NRTI-sparing regimen including DRV+ MVC may have a potential role in immune system modulation by the direct down regulation of apoptosis and chemotaxis.

Effect of maraviroc intensification on HIV-1-specific T cell immunity in recently HIV-1-infected individuals

Background

The effect of maraviroc on the maintenance and the function of HIV-1-specific T cell responses remains unknown.

Methods

Subjects recently infected with HIV-1 were randomized to receive anti-retroviral treatment with or without maraviroc intensification for 48 weeks, and were monitored up to week 60. PBMC and in vitro-expanded T cells were tested for responses to the entire HIV proteome by ELISpot analyses. Intracellular cytokine staining assays were conducted to monitor the (poly)-functionality of HIV-1-specific T cells. Analyses were performed at baseline and week 24 after treatment start, and at week 60 (3 months after maraviroc discontinuation).

Results

Maraviroc intensification was associated with a slower decay of virus-specific T cell responses over time compared to the non-intensified regimen in both direct ex-vivo as well as in in-vitro expanded cells. The effector function profiles of virus-specific CD8⁺ T cells were indistinguishable between the two arms and did not change over time between the groups.

Conclusions

Maraviroc did not negatively impact any of the measured parameters, but was rather associated with a prolonged maintenance of HIV-1-specific T cell responses. Maraviroc, in addition to its original effect as viral entry inhibitor, may provide an additional benefit on the maintenance of virus-specific T cells which may be especially important for future viral eradication strategies.

Pharmacokinetic interaction between maraviroc and fosamprenavir-ritonavir: an open-label, fixed-sequence study in healthy subjects

This open-label, fixed-sequence, phase 1 study evaluated the pharmacokinetic interaction between maraviroc (MVC) and ritonavir-boosted fosamprenavir (FPV/r) in healthy subjects. In period 1, subjects received 300 mg of MVC twice daily (BID; cohort 1) or once daily (QD; cohort 2) for 5 days. In period 2, cohort 1 subjects received 700/100 mg of FPV/r BID alone on days 1 to 10 and then FPV/r at 700/100 mg BID plus MVC at 300 mg BID on days 11 to 20; cohort 2 subjects received FPV/r at 1,400/100 mg QD alone on days 1 to 10 and then FPV/r at 1,400/100 mg QD plus MVC at 300 mg QD on days 11 to 20. Pharmacokinetic parameters, assessed on day 5 of period 1 and on days 10 and 20 of period 2, included the maximum plasma concentration (Cmax), the concentration at end of dosing interval (Cτ), and the area under the curve over dosing interval (AUCτ). Safety and tolerability were also assessed. MVC geometric mean AUCτ, Cmax, and Cτ were increased by 149, 52, and 374%, respectively, after BID dosing with FPV/r, and by 126, 45, and 80%, respectively, after QD dosing. Amprenavir (the active form of the prodrug fosamprenavir) and ritonavir exposures were decreased in the presence of MVC with amprenavir AUCτ, Cmax, and Cτ decreased by 34 to 36% in the presence of FPV/r plus maraviroc BID and by 15 to 30% with FPV/r plus MVC QD both compared to FPV/r alone. The overall all-causality adverse-event (AE) incidence rate was 96.4%; all AEs were of mild or moderate severity. Commonly reported treatment-related AEs (>20% of patients overall) included diarrhea, fatigue, abdominal discomfort, headache, and nausea. No serious AEs or deaths occurred. In summary, maraviroc exposure increased in the presence of FPV/r, whereas MVC coadministration decreased amprenavir and ritonavir exposures. MVC dosed at 300 mg BID with FPV/r is not recommended due to concerns of lower amprenavir exposures; however, no dose adjustment is warranted with MVC at 150 mg BID in combination with FPV/r based on the available clinical data. MVC plus FPV/r was generally well tolerated; no new safety signals were detected.

Neuroprotective maraviroc monotherapy in simian immunodeficiency virus-infected macaques: reduced replicating and latent SIV in the brain

OBJECTIVE

HIV-associated neurocognitive deficits remain a challenge despite suppressive combined antiretroviral therapy. Given the association between HIV-induced central nervous system (CNS) disease and replication of HIV in immune-activated macrophages, CCR5 antagonists may attenuate CNS disease by modulating inflammatory signaling and by limiting viral replication.

DESIGN

To establish whether initiating CCR5 inhibition during early infection altered CNS disease progression, outcomes were compared between simian immunodeficiency virus (SIV)-infected macaques treated with maraviroc (MVC) versus untreated SIV-infected macaques.

METHODS

Six SIV-infected rhesus macaques were treated with MVC monotherapy for 5 months beginning 24 days postinoculation; 22 SIV-infected animals served as untreated controls. SIV RNA levels in plasma, cerobrospinal fluid, and brain, and CNS expression of TNFα and CCL2 were measured by qRT-PCR. Immunostaining for CD68 and amyloid precursor protein in the brain was measured by image analysis. Plasma sCD163 was measured by ELISA.

RESULTS

SIV RNA and proviral DNA levels in brain were markedly lower with MVC treatment, demonstrating CCR5 inhibition reduces CNS replication of SIV and may reduce the CNS latent viral reservoir. MVC treatment also lowered monocyte and macrophage activation, represented by CNS CD68 immunostaining and plasma sCD163 levels, and reduced both TNFα and CCL2 RNA expression in brain. Treatment also reduced axonal amyloid precursor protein immunostaining to levels present in uninfected animals, consistent with neuroprotection.

CONCLUSION

CCR5 inhibitors may prevent neurologic disorders in HIV-infected individuals by reducing inflammation and by limiting viral replication in the brain. Furthermore, CCR5 inhibitors may reduce the latent viral reservoir in the CNS. Adding CCR5 inhibitors to combined antiretroviral regimens may offer multiple neuroprotective benefits.

Maraviroc as intensification strategy in HIV-1 positive patients with deficient immunological response: an Italian randomized clinical trial

BACKGROUND

Immunological non-responders (INRs) lacked CD4 increase despite HIV-viremia suppression on HAART and had an increased risk of disease progression. We assessed immune reconstitution profile upon intensification with maraviroc in INRs.

METHODS

We designed a multi-centric, randomized, parallel, open label, phase 4 superiority trial. We enrolled 97 patients on HAART with CD4+<200/µL and/or CD4+ recovery ≤ 25% and HIV-RNA<50 cp/mL. Patients were randomized 1:1 to HAART+maraviroc or continued HAART. CD4+ and CD8+ CD45+RA/RO, Ki67 expression and plasma IL-7 were quantified at W0, W12 and W48.

RESULTS

By W48 both groups displayed a CD4 increase without a significant inter-group difference. A statistically significant change in CD8 favored patients in arm HAART+maraviroc versus HAART at W12 (p=.009) and W48 (p=.025). The CD4>200/µL and CD4>200/µL + CD4 gain ≥ 25% end-points were not satisfied at W12 (p=.24 and p=.619) nor at W48 (p=.076 and p=.236). Patients continuing HAART displayed no major changes in parameters of T-cell homeostasis and activation. Maraviroc-receiving patients experienced a significant rise in circulating IL-7 by W48 (p=.01), and a trend in temporary reduction in activated HLA-DR+CD38+CD4+ by W12 (p=.06) that was not maintained at W48.

CONCLUSIONS

Maraviroc intensification in INRs did not have a significant advantage in reconstituting CD4 T-cell pool, but did substantially expand CD8. It resulted in a low rate of treatment discontinuations.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00884858 http://clinicaltrials.gov/show/NCT00884858.

Frequency and predictors of HIV-1 co-receptor switch in treatment naive patients

Background

Determination of HIV-1 co-receptor use is a necessity before initiation of a CCR5 antagonist but the longevity of a CCR5-use prediction remains unknown.

Methods

Genotypic co-receptor tropism determination was performed in 225 newly diagnosed individuals consulting an AIDS Reference Centre. Samples were collected at diagnosis and at initiation of antiretroviral therapy or just before closure of the study for patients who did not initiate therapy. For individuals with a discordant tropism prediction on the two longitudinal samples, analysis of intermediate samples and single genome sequencing of proviral DNA was performed to confirm the tropism switch. Deep sequencing was done to identify minor CXCR4 or CCR5-using populations in the initial sample.

Results

Overall, tropism switches were rare (7.6%). Only a geno2pheno false positive rate of <50% at baseline was retained as predictive for a subsequent switch from CCR5-use only to predicted CXCR4-use. Minor CXCR4-using virus populations were detected in the first sample of 9 of the 14 R5-to-X4 switchers but the subsequent outgrowth of these minor populations was documented in only 3.

Conclusions

With the current guidelines for treatment initiation at CD4⁺ T cell counts of <500 cells/mm³, co-receptor switch between diagnosis and starting antiretroviral therapy is rare. Patients with R5 viruses and a geno2pheno FPR of <50% are more prone to subsequent co-receptor switch than patients with an FPR of >50% and will need repeat tropism testing if initiation of maraviroc is considered and previous testing dates from more than a year before.

Maraviroc attenuates trauma-hemorrhage-induced hepatic injury through PPAR gamma-dependent pathway in rats

Maraviroc is a CC-chemokine receptor 5 (CCR5) antagonist with potent antiviral and cancer preventive effects. Recent evidence suggests that the co-existence of CCR5 in various cell types is involved in inflammation. However, the effects that CCR5 antagonists produce in trauma-hemorrhage remain unknown. The peroxisome proliferator-activated receptor gamma (PPAR_γ) pathway exerts anti-inflammatory effects in injury. In this study, we hypothesized that maraviroc administration in male rats, after trauma-hemorrhage, decreases cytokine production and protects against hepatic injury through a PPAR_γ-dependent pathway. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure maintained at approximately 35-40 mmHg for 90 minutes), followed by fluid resuscitation. During resuscitation, a single dose of maraviroc (3 mg/kg, intravenously) with and without a PPAR_γ antagonist GW9662 (1 mg/kg, intravenously), GW9662 or vehicle was administered. Plasma alanine aminotransferase (ALT) with aspartate aminotransferase (AST) concentrations and various hepatic parameters were measured (n=8 rats/group) at 24 hours after resuscitation. The results showed that trauma-hemorrhage increased hepatic myeloperoxidase activity, intercellular adhesion molecule-1 and interleukin-6 levels, and plasma ALT and AST concentrations. These parameters were significantly improved in the maraviroc-treated rats subjected to trauma-hemorrhage. Maraviroc treatment also increased hepatic PPAR_γ expression compared with vehicle-treated trauma-hemorrhaged rats. Co-administration of GW9662 with maraviroc abolished the maraviroc-induced beneficial effects on the above parameters and hepatic injury. These results suggest that the protective effect of maraviroc administration on alleviation of hepatic injury after trauma-hemorrhage, which is, at least in part, through PPAR_γ-dependent pathway.

Dissimilarities in the metabolism of antiretroviral drugs used in HIV pre-exposure prophylaxis in colon and vagina tissues

Attempts to prevent HIV infection through pre-exposure prophylaxis (PrEP) include topical application of anti-HIV drugs to the mucosal sites of infection; however, a potential role for local drug metabolizing enzymes in modulating the exposure of the mucosal tissues to these drugs has yet to be explored. Here we present the first report that enzymes belonging to the cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) families of drug metabolizing enzymes are expressed and active in vaginal and colorectal tissue using biopsies collected from healthy volunteers. In doing so, we discovered that dapivirine and maraviroc, a non-nucleoside reverse transcriptase inhibitor and an entry inhibitor currently in development as microbicides for HIV PrEP, are differentially metabolized in colorectal tissue and vaginal tissue. Taken together, these data should help to guide the optimization of small molecules being developed for HIV PrEP.

Structure and dynamics of the gp120 V3 loop that confers noncompetitive resistance in R5 HIV-1(JR-FL) to maraviroc

Maraviroc, an (HIV-1) entry inhibitor, binds to CCR5 and efficiently prevents R5 human immunodeficiency virus type 1 (HIV-1) from using CCR5 as a coreceptor for entry into CD4(+) cells. However, HIV-1 can elude maraviroc by using the drug-bound form of CCR5 as a coreceptor. This property is known as noncompetitive resistance. HIV-1(V3-M5) derived from HIV-1(JR-FLan) is a noncompetitive-resistant virus that contains five mutations (I304V/F312W/T314A/E317D/I318V) in the gp120 V3 loop alone. To obtain genetic and structural insights into maraviroc resistance in HIV-1, we performed here mutagenesis and computer-assisted structural study. A series of site-directed mutagenesis experiments demonstrated that combinations of V3 mutations are required for HIV-1(JR-FLan) to replicate in the presence of 1 µM maraviroc, and that a T199K mutation in the C2 region increases viral fitness in combination with V3 mutations. Molecular dynamic (MD) simulations of the gp120 outer domain V3 loop with or without the five mutations showed that the V3 mutations induced (i) changes in V3 configuration on the gp120 outer domain, (ii) reduction of an anti-parallel β-sheet in the V3 stem region, (iii) reduction in fluctuations of the V3 tip and stem regions, and (iv) a shift of the fluctuation site at the V3 base region. These results suggest that the HIV-1 gp120 V3 mutations that confer maraviroc resistance alter structure and dynamics of the V3 loop on the gp120 outer domain, and enable interactions between gp120 and the drug-bound form of CCR5.

HIV-1 tropism determination using a phenotypic Env recombinant viral assay highlights overestimation of CXCR4-usage by genotypic prediction algorithms for CRF01_AE and CRF02_AG [corrected]

BACKGROUND

Human Immunodeficiency virus type-1 (HIV) entry into target cells involves binding of the viral envelope (Env) to CD4 and a coreceptor, mainly CCR5 or CXCR4. The only currently licensed HIV entry inhibitor, maraviroc, targets CCR5, and the presence of CXCX4-using strains must be excluded prior to treatment. Co-receptor usage can be assessed by phenotypic assays or through genotypic prediction. Here we compared the performance of a phenotypic Env-Recombinant Viral Assay (RVA) to the two most widely used genotypic prediction algorithms, Geno2Pheno[coreceptor] and webPSSM.

METHODS

Co-receptor tropism of samples from 73 subtype B and 219 non-B infections was measured phenotypically using a luciferase-tagged, NL4-3-based, RVA targeting Env. In parallel, tropism was inferred genotypically from the corresponding V3-loop sequences using Geno2Pheno[coreceptor] (5-20% FPR) and webPSSM-R5X4. For discordant samples, phenotypic outcome was retested using co-receptor antagonists or the validated Trofile® Enhanced-Sensitivity-Tropism-Assay.

RESULTS

The lower detection limit of the RVA was 2.5% and 5% for X4 and R5 minority variants respectively. A phenotype/genotype result was obtained for 210 samples. Overall, concordance of phenotypic results with Geno2Pheno[coreceptor] was 85.2% and concordance with webPSSM was 79.5%. For subtype B, concordance with Geno2pheno[coreceptor] was 94.4% and concordance with webPSSM was 79.6%. High concordance of genotypic tools with phenotypic outcome was seen for subtype C (90% for both tools). Main discordances involved CRF01_AE and CRF02_AG for both algorithms (CRF01_AE: 35.9% discordances with Geno2Pheno[coreceptor] and 28.2% with webPSSM; CRF02_AG: 20.7% for both algorithms). Genotypic prediction overestimated CXCR4-usage for both CRFs. For webPSSM, 40% discordance was observed for subtype A.

CONCLUSIONS

Phenotypic assays remain the most accurate for most non-B subtypes and new subtype-specific rules should be developed for non-B subtypes, as research studies more and more draw conclusions from genotypically-inferred tropism, and to avoid unnecessarily precluding patients with limited treatment options from receiving maraviroc or other entry inhibitors.

Efficient single tobamoviral vector-based bioproduction of broadly neutralizing anti-HIV-1 monoclonal antibody VRC01 in Nicotiana benthamiana plants and utility of VRC01 in combination microbicides

Broadly neutralizing monoclonal antibodies (bnMAbs) may offer powerful tools for HIV-1 preexposure prophylaxis, such as topical microbicides. However, this option is hampered due to expensive MAb biomanufacturing based on mammalian cell culture. To address this issue, we developed a new production system for bnMAb VRC01 in Nicotiana benthamiana plants using a tobamovirus replicon vector. Unlike conventional two-vector-based expression, this system was designed to overexpress full-length IgG1 from a single polypeptide by means of kex2p-like enzyme recognition sites introduced between the heavy and light chains. An enzyme-linked immunosorbent assay (ELISA) revealed that gp120-binding VRC01 IgG1 was maximally accumulated on 5 to 7 days following vector inoculation, yielding ~150 mg of the bnMAb per kg of fresh leaf material. The plant-made VRC01 (VRC01p) was efficiently purified by protein A affinity followed by hydrophobic-interaction chromatography. ELISA, surface plasmon resonance, and an HIV-1 neutralization assay demonstrated that VRC01p has gp120-binding affinity and HIV-1-neutralization capacity virtually identical to the human-cell-produced counterpart. To advance VRC01p's use in topical microbicides, we analyzed combinations of the bnMAb with other microbicide candidates holding distinct antiviral mechanisms in an HIV-1 neutralization assay. VRC01p exhibited clear synergy with the antiviral lectin griffithsin, the CCR5 antagonist maraviroc, and the reverse transcriptase inhibitor tenofovir in multiple CCR5-tropic HIV-1 strains from clades A, B, and C. In summary, VRC01p is amenable to robust, rapid, and large-scale production and may be developed as an active component in combination microbicides with other anti-HIV agents such as antiviral lectins, CCR5 antagonists, and reverse transcriptase inhibitors.

Hepatoxicity of new antiretrovirals: a systematic review

There has been a major paradigm shift in the management of HIV infected patients, with earlier initiation of antiretroviral treatment and lifelong exposure to drugs for which long-term safety issues must be faced by clinicians. Within the past 5 years, new drugs from both previously established and novel therapeutic classes have been released that tend to be safer and more efficient than their former combinations. Although hepatotoxicity was one of the most common side effects from initial antiretrovirals, phase II/III safety data regarding liver tolerance from more recent drugs are reassuring. However, data on the long-term exposure to these therapeutic options are needed, and a handful of case reports are emerging, reporting rare but potentially life-threatening adverse hepatic events in patients with hepatitis co-infection or taking other hepatotoxic drugs.

Long-term suppressive combined antiretroviral treatment does not normalize the serum level of soluble CD14

Levels of soluble CD14 (sCD14) were longitudinally measured in 85 human immunodeficiency virus (HIV)-infected subjects during long-term receipt of suppressive combined antiretroviral therapy (cART) and compared to those in young and elderly HIV-negative control subjects. cART did not normalize sCD14 levels; rather, the HIV-infected group displayed a significantly higher sCD14 level at baseline (ie, before cART initiation), 1 year after cART initiation, and 5 years after cART initiation, compared with both control groups. Furthermore, the baseline CD4(+) T-cell count was inversely associated with the baseline sCD14 level. Our results point to the necessity of complementary therapies to treat the activated/inflamed status associated with chronic HIV infection and to the benefits of early initiation of cART.

Maraviroc, a CCR5 antagonist, prevents development of hepatocellular carcinoma in a mouse model

Chronic liver disease may result in a sequential progression through fibrosis, cirrhosis and lead, eventually, to hepatocellular carcinoma (HCC). Hepatic stellate cells (HSC) seem to be responsible for the fibrogenic response through the activation of an autocrine loop involving the chemokine receptor, CCR5. However, the role of CCR5 in HCC remains poorly understood. Since this receptor is also one of the main ports of entry for the human immunodeficiency virus (HIV), several CCR5 inhibitors are being used in the clinic to reduce viral load. We used one of these inhibitors, maraviroc (MVC), in a mouse model of diet-induced HCC to investigate whether this intervention would reduce disease progression. Animals treated with MVC on top of a normal control diet did not present any evidence of toxicity or any morphological change when compared with non-treated mice. Animals treated with MVC presented higher survival, less liver fibrosis, lower levels of liver injury markers and chemokines, less apoptosis, lower proliferation index, and lower tumor burden than their counterparts receiving only the hepatotoxic diet. In addition, MVC inhibits HSC activation markers such as phosphorylation of p38 and ERK, and increases hepatocyte survival. This study suggests that MVC, a well tolerated and clinically characterized drug, may be used as a preventative treatment for HCC. Clinical studies are needed to demonstrate the efficacy of this drug, or other CCR5 inhibitors, in patients with high risk of developing HCC.

HIV-2 susceptibility to entry inhibitors

Currently, there is a growing interest in using entry inhibitors to treat HIV-2-infected patients because, among the available drugs, few are fully active against HIV-2. Recent studies indicate that maraviroc and other experimental entry inhibitors, including new CCR5 and CXCR4 antagonists, inhibit primary isolates of HIV-2 as well as HIV-1 and may, therefore, expand the existing therapeutic armamentarium against HIV-2. There are, however, significant differences between the evolution of HIV-1 and HIV-2 envelope glycoproteins during infection that can lead to differences in the response to therapy with entry inhibitors over the course of the infection. Here, we review the available data on the susceptibility of HIV-2 to entry inhibitors in the context of the evolution of the sequence, structure, and function of envelope glycoproteins during infection.

[Use of maraviroc, the first CCR5 receptor antagonist, in HIV treatment regimens]

The paper gives the results of international trials of and guidelines for the use of maraviroc, the first CCR5 receptor antagonist, in treatment regimens for HIV-infected patients. The trials have convincingly shown that the maraviroc-containing antiretroviral therapy (ART) regimens are highly effective and safe for R5-tropic HIV-infected patients regardless of previous ART, baseline HIV RNA levels, and CD4+ lymphocyte count. Maraviroc can be recommended for HIV-infected patients who have previously received ART and who have been found to have a R5-tropic virus. The changes in the ART regimen and inclusion of maraviroc may be associated with both an ineffective previous treatment regimen and therapy-induced adverse events. In 2012, Russia's first reagent kit for the determination of HIV tropism was put to tests and registered at the Russian Inspectorate for the Protection of Consumer Rights and Human Welfare.

Stochastic model of in-vivo X4 emergence during HIV infection: implications for the CCR5 inhibitor maraviroc

The emergence of X4 tropic viral strains throughout the course of HIV infection is associated with poorer prognostic outcomes and faster progressions to AIDS than for patients in whom R5 viral strains predominate. Here we investigate a stochastic model to account for the emergence of X4 virus via mutational intermediates of lower fitness that exhibit dual/mixed (D/M) tropism, and employ the model to investigate whether the administration of CCR5 blockers in-vivo is likely to promote a shift towards X4 tropism. We show that the proposed stochastic model can account for X4 emergence with a median time of approximately 4 years post-infection as a result of: 1.) random stochastic mutations in the V3 region of env during the reverse transcription step of infection; 2.) increasing numbers of CXCR4-expressing activated naive CD4+ T cells with declining total CD4+ T cell counts, thereby providing increased numbers of activated target cells for productive infection by X4 virus. Our model indicates that administration of the CCR5 blocker maraviroc does not promote a shift towards X4 tropism, assuming sufficient efficacy of background therapy (BT). However our modelling also indicates that administration of maraviroc as a monotherapy or with BT of suboptimal efficacy can promote emergence of X4 tropic virus, resulting in accelerated progression to AIDS. Taken together, our results demonstrate that maraviroc is safe and effective if co-administered with sufficiently potent BT, but that suboptimal BT may promote X4 emergence and accelerated progression to AIDS. These results underscore the clinical importance for careful selection of BT when CCR5 blockers are administered in-vivo.

Blockade of lymphocyte chemotaxis in visceral graft-versus-host disease

BACKGROUND

Graft-versus-host disease (GVHD) is a major barrier to successful allogeneic hematopoietic stem-cell transplantation (HSCT). The chemokine receptor CCR5 appears to play a role in alloreactivity. We tested whether CCR5 blockade would be safe and limit GVHD in humans.

METHODS

We tested the in vitro effect of the CCR5 antagonist maraviroc on lymphocyte function and chemotaxis. We then enrolled 38 high-risk patients in a single-group phase 1 and 2 study of reduced-intensity allogeneic HSCT that combined maraviroc with standard GVHD prophylaxis.

RESULTS

Maraviroc inhibited CCR5 internalization and lymphocyte chemotaxis in vitro without impairing T-cell function or formation of hematopoietic-cell colonies. In 35 patients who could be evaluated, the cumulative incidence rate (±SE) of grade II to IV acute GVHD was low at 14.7±6.2% on day 100 and 23.6±7.4% on day 180. Acute liver and gut GVHD were not observed before day 100 and remained uncommon before day 180, resulting in a low cumulative incidence of grade III or IV GVHD on day 180 (5.9±4.1%). The 1-year rate of death that was not preceded by disease relapse was 11.7±5.6% without excessive rates of relapse or infection. Serum from patients receiving maraviroc prevented CCR5 internalization by CCL5 and blocked T-cell chemotaxis in vitro, providing evidence of antichemotactic activity.

CONCLUSIONS

In this study, inhibition of lymphocyte trafficking was a specific and potentially effective new strategy to prevent visceral acute GVHD. (Funded by Pfizer and others; ClinicalTrials.gov number, NCT00948753.).

Update on clinical and methodological recommendations for genotypic determination of HIV tropism to guide the usage of CCR5 antagonists

The genotypic determination of HIV tropism to guide the use of maraviroc, the first CCR5 antagonist with specific antiviral activity against CCR5 (R5)-tropic HIV variants, has been widespread in the last two years. Retrospective analyses from maraviroc clinical trials (MOTIVATE and MERIT) demonstrated that specific genotypic tools and the phenotypic assay TrofileTM are comparable in predicting virologic response to maraviroc. Moreover, recent studies performed in cohorts of patients outside clinical trials have reported overall rates of virologic response to maraviroc up to 82% in patients harboring HIV R5-tropic variants according to genotypic tools. Specific technical requirements as well as recommendations for proper HIV tropism determination in the clinical setting have been improving, according to new data reported in several studies related with this issue. This review updates clinical and methodological recommendations for genotypic determination of HIV tropism to guide therapeutic decisions using CCR5 antagonists, considering the most recently reported data.

A highly intensified ART regimen induces long-term viral suppression and restriction of the viral reservoir in a simian AIDS model

Stably suppressed viremia during ART is essential for establishing reliable simian models for HIV/AIDS. We tested the efficacy of a multidrug ART (highly intensified ART) in a wide range of viremic conditions (10³-10⁷) viral RNA copies/mL) in SIVmac251-infected rhesus macaques, and its impact on the viral reservoir. Eleven macaques in the pre-AIDS stage of the disease were treated with a multidrug combination (highly intensified ART) consisting of two nucleosidic/nucleotidic reverse transcriptase inhibitors (emtricitabine and tenofovir), an integrase inhibitor (raltegravir), a protease inhibitor (ritonavir-boosted darunavir) and the CCR5 blocker maraviroc. All animals stably displayed viral loads below the limit of detection of the assay (i.e. <40 RNA copies/mL) after starting highly intensified ART. By increasing the sensitivity of the assay to 3 RNA copies/mL, viral load was still below the limit of detection in all subjects tested. Importantly, viral DNA resulted below the assay detection limit (<2 copies of DNA/5*10⁵ cells) in PBMCs and rectal biopsies of all animals at the end of the follow-up, and in lymph node biopsies from the majority of the study subjects. Moreover, highly intensified ART decreased central/transitional memory, effector memory and activated (HLA-DR⁺) effector memory CD4⁺ T-cells in vivo, in line with the role of these subsets as the main cell subpopulations harbouring the virus. Finally, treatment with highly intensified ART at viral load rebound following suspension of a previous anti-reservoir therapy eventually improved the spontaneous containment of viral load following suspension of the second therapeutic cycle, thus leading to a persistent suppression of viremia in the absence of ART. In conclusion, we show, for the first time, complete suppression of viral load by highly intensified ART and a likely associated restriction of the viral reservoir in the macaque AIDS model, making it a useful platform for testing potential cures for AIDS.

Susceptibility of HIV type 2 primary isolates to CCR5 and CXCR4 monoclonal antibodies, ligands, and small molecule inhibitors

Human immunodeficiency virus (HIV) entry into susceptible cells involves the interaction between viral envelope glycoproteins with CD4 and a chemokine receptor (coreceptor), namely CCR5 and CXCR4. This interaction has been studied to enable the discovery of a new class of antiretroviral drugs that targets the envelope glycoprotein-coreceptor interaction. However, very few data exist regarding HIV-2 susceptibility to these coreceptor inhibitors. With this work we aimed to identify this susceptibility in order to assess the potential use of these molecules to treat HIV-2-infected patients and to further understand the molecular basis of HIV-2 envelope glycoprotein interactions with CCR5 and CXCR4. We found that CCR5-using HIV-2 isolates are readily inhibited by maraviroc, TAK-779, and PF-227153, while monoclonal antibody 2D7 shows only residual or no inhibitory effects. The anti-HIV-2 activity of CXCR4-targeted molecules reveals that SDF-1α/CXCL12 inhibited all HIV-2 tested except one, while mAb 12G5 inhibited the replication of only two isolates, showing residual inhibitory effects with all the other CXCR4-using viruses. A major conclusion from our results is that infection by HIV-2 primary isolates is readily blocked in vitro by maraviroc, at concentrations similar to those required for HIV-1. The susceptibility to maraviroc was independent of CD4(+) T cell counts or clinical stage of the patient from which the virus was obtained. These findings indicate that maraviroc could constitute a reliable therapeutic alternative for HIV-2-infected patients, as long as they are infected with CCR5-using variants, and this may have direct implications for the clinical management of HIV-2-infected patients.

Structural insights from binding poses of CCR2 and CCR5 with clinically important antagonists: a combined in silico study

Chemokine receptors are G protein-coupled receptors that contain seven transmembrane domains. In particular, CCR2 and CCR5 and their ligands have been implicated in the pathophysiology of a number of diseases, including rheumatoid arthritis and multiple sclerosis. Based on their roles in disease, they have been attractive targets for the pharmaceutical industry, and furthermore, targeting both CCR2 and CCR5 can be a useful strategy. Owing to the importance of these receptors, information regarding the binding site is of prime importance. Structural studies have been hampered due to the lack of X-ray crystal structures, and templates with close homologs for comparative modeling. Most of the previous models were based on the bovine rhodopsin and β2-adrenergic receptor. In this study, based on a closer homolog with higher resolution (CXCR4, PDB code: 3ODU 2.5 Å), we constructed three-dimensional models. The main aim of this study was to provide relevant information on binding sites of these receptors. Molecular dynamics simulation was done to refine the homology models and PROCHECK results indicated that the models were reasonable. Here, binding poses were checked with some established inhibitors of high pharmaceutical importance against the modeled receptors. Analysis of interaction modes gave an integrated interpretation with detailed structural information. The binding poses confirmed that the acidic residues Glu291 (CCR2) and Glu283 (CCR5) are important, and we also found some additional residues. Comparisons of binding sites of CCR2/CCR5 were done sequentially and also by docking a potent dual antagonist. Our results can be a starting point for further structure-based drug design.

Intensification of antiretroviral therapy with a CCR5 antagonist in patients with chronic HIV-1 infection: effect on T cells latently infected

OBJECTIVE

The primary objective was to assess the effect of MVC intensification on latently infected CD4(+) T cells in chronically HIV-1-infected patients receiving antiretroviral therapy.

METHODS

We performed an open-label pilot phase II clinical trial involving chronically HIV-1-infected patients receiving stable antiretroviral therapy whose regimen was intensified with 48 weeks of maraviroc therapy. We analyzed the latent reservoir, the residual viremia and episomal 2LTR DNA to examine the relationship between these measures and the HIV-1 latent reservoir, immune activation, lymphocyte subsets (including effector and central memory T cells), and markers associated with bacterial translocation.

RESULTS

Overall a non significant reduction in the size of the latent reservoir was found (p = 0.068). A mean reduction of 1.82 IUPM was observed in 4 patients with detectable latent reservoir at baseline after 48 weeks of intensification. No effect on plasma residual viremia was observed. Unexpectedly, all the patients had detectable 2LTR DNA circles at week 24, while none of them showed those circles at the end of the study. No changes were detected in CD4(+) or CD8(+) counts, although a significant decrease was found in the proportion of HLA-DR(+)/CD38(+) CD4(+) and CD8(+) T-cells. LPS and sCD14 levels increased.

CONCLUSIONS

Intensification with MVC was associated with a trend to a decrease in the size of the latent HIV-1 reservoir in memory T cells. No impact on residual viremia was detected. Additional studies with larger samples are needed to confirm the results.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00795444.

SHIV-162P3 infection of rhesus macaques given maraviroc gel vaginally does not involve resistant viruses

Maraviroc (MVC) gels are effective at protecting rhesus macaques from vaginal SHIV transmission, but breakthrough infections can occur. To determine the effects of a vaginal MVC gel on infecting SHIV populations in a macaque model, we analyzed plasma samples from three rhesus macaques that received a MVC vaginal gel (day 0) but became infected after high-dose SHIV-162P3 vaginal challenge. Two infected macaques that received a placebo gel served as controls. The infecting SHIV-162P3 stock had an overall mean genetic distance of 0.294±0.027%; limited entropy changes were noted across the envelope (gp160). No envelope mutations were observed consistently in viruses isolated from infected macaques at days 14-21, the time of first detectable viremia, nor selected at later time points, days 42-70. No statistically significant differences in MVC susceptibilities were observed between the SHIV inoculum (50% inhibitory concentration [IC(50)] 1.87 nM) and virus isolated from the three MVC-treated macaques (MVC IC(50) 1.18 nM, 1.69 nM, and 1.53 nM, respectively). Highlighter plot analyses suggested that infection was established in each MVC-treated animal by one founder virus genotype. The expected Poisson distribution of pairwise Hamming Distance frequency counts was observed and a phylogenetic analysis did not identify infections with distinct lineages from the challenge stock. These data suggest that breakthrough infections most likely result from incomplete viral inhibition and not the selection of MVC-resistant variants.

Resistance to the CCR5 inhibitor 5P12-RANTES requires a difficult evolution from CCR5 to CXCR4 coreceptor use

Viral resistance to small molecule allosteric inhibitors of CCR5 is well documented, and involves either selection of preexisting CXCR4-using HIV-1 variants or envelope sequence evolution to use inhibitor-bound CCR5 for entry. Resistance to macromolecular CCR5 inhibitors has been more difficult to demonstrate, although selection of CXCR4-using variants might be expected. We have compared the in vitro selection of HIV-1 CC1/85 variants resistant to either the small molecule inhibitor maraviroc (MVC) or the macromolecular inhibitor 5P12-RANTES. High level resistance to MVC was conferred by the same envelope mutations as previously reported after 16–18 weeks of selection by increasing levels of MVC. The MVC-resistant mutants were fully sensitive to inhibition by 5P12-RANTES. By contrast, only transient and low level resistance to 5P12-RANTES was achieved in three sequential selection experiments, and each resulted in a subsequent collapse of virus replication. A fourth round of selection by 5P12-RANTES led, after 36 weeks, to a “resistant” variant that had switched from CCR5 to CXCR4 as a coreceptor. Envelope sequences diverged by 3.8% during selection of the 5P12-RANTES resistant, CXCR4-using variants, with unique and critical substitutions in the V3 region. A subset of viruses recovered from control cultures after 44 weeks of passage in the absence of inhibitors also evolved to use CXCR4, although with fewer and different envelope mutations. Control cultures contained both viruses that evolved to use CXCR4 by deleting four amino acids in V3, and others that maintained entry via CCR5. These results suggest that coreceptor switching may be the only route to resistance for compounds like 5P12-RANTES. This pathway requires more mutations and encounters more fitness obstacles than development of resistance to MVC, confirming the clinical observations that resistance to small molecule CCR5 inhibitors very rarely involves coreceptor switching.

A topical microbicide gel formulation of CCR5 antagonist maraviroc prevents HIV-1 vaginal transmission in humanized RAG-hu mice

For prevention of HIV infection many currently licensed anti-HIV drugs and new ones in the pipeline show potential as topically applied microbicides. While macaque models have been the gold standard for in vivo microbicide testing, they are expensive and sufficient numbers are not available. Therefore, a small animal model that facilitates rapid evaluation of potential candidates for their preliminary efficacy is urgently needed in the microbicide field. We previously demonstrated that RAG-hu humanized mouse model permits HIV-1 mucosal transmission via both vaginal and rectal routes and that oral pre-exposure chemo-prophylactic strategies could be tested in this system. Here in these proof-of-concept studies, we extended this system for topical microbicide testing using HIV-1 as the challenge virus. Maraviroc, a clinically approved CCR5 inhibitor drug for HIV treatment, was formulated as a microbicide gel at 5 mM concentration in 2.2% hydroxyl ethyl cellulose. Female RAG-hu mice were challenged vaginally with HIV-1 an hour after intravaginal application of the maraviroc gel. Our results showed that maraviroc gel treated mice were fully protected against vaginal HIV-1 challenge in contrast to placebo gel treated mice which all became infected. These findings highlight the utility of the humanized mouse models for microbicide testing and, together with the recent data from macaque studies, suggest that maraviroc is a promising candidate for future microbicide clinical trials in the field.

Estimating the threshold surface density of Gp120-CCR5 complexes necessary for HIV-1 envelope-mediated cell-cell fusion

Reduced expression of CCR5 on target CD4⁺ cells lowers their susceptibility to infection by R5-tropic HIV-1, potentially preventing transmission of infection and delaying disease progression. Binding of the HIV-1 envelope (Env) protein gp120 with CCR5 is essential for the entry of R5 viruses into target cells. The threshold surface density of gp120-CCR5 complexes that enables HIV-1 entry remains poorly estimated. We constructed a mathematical model that mimics Env-mediated cell-cell fusion assays, where target CD4⁺CCR5⁺ cells are exposed to effector cells expressing Env in the presence of a coreceptor antagonist and the fraction of target cells fused with effector cells is measured. Our model employs a reaction network-based approach to describe protein interactions that precede viral entry coupled with the ternary complex model to quantify the allosteric interactions of the coreceptor antagonist and predicts the fraction of target cells fused. By fitting model predictions to published data of cell-cell fusion in the presence of the CCR5 antagonist vicriviroc, we estimated the threshold surface density of gp120-CCR5 complexes for cell-cell fusion as ∼20 µm⁻². Model predictions with this threshold captured data from independent cell-cell fusion assays in the presence of vicriviroc and rapamycin, a drug that modulates CCR5 expression, as well as assays in the presence of maraviroc, another CCR5 antagonist, using sixteen different Env clones derived from transmitted or early founder viruses. Our estimate of the threshold surface density of gp120-CCR5 complexes necessary for HIV-1 entry thus appears robust and may have implications for optimizing treatment with coreceptor antagonists, understanding the non-pathogenic infection of non-human primates, and designing vaccines that suppress the availability of target CD4⁺CCR5⁺ cells.

Cost-effectiveness of optimized background therapy plus maraviroc for previously treated patients with R5 HIV-1 infection from the perspective of the Spanish health care system

OBJECTIVE

The aim of this work was to evaluate the cost-effectiveness, from the perspective of the Spanish health care system, of optimized background therapy (OBT) plus maraviroc 300 mg BID versus OBT plus placebo in previously treated patients with R5 HIV-1 infection.

METHODS

A lifetime cohort model was developed, based on 24- and 48-week pooled results from the Maraviroc Versus Optimized Therapy in Viremic Antiretroviral Treatment-Experienced Patients (MOTIVATE) studies 1 and 2, to reflect the Spanish health care system's perspective. Treatment duration was based on clinical trial follow-up from MOTIVATE 1 and 2. Clinical data, cohort characteristics, success probability, CD4 increase rate, CD4 cell status link to disease states, and adverse-event probability were taken from the MOTIVATE trials and other published literature. Other input parameters were taken from published sources. Antiretroviral (ARV) costs were derived from local sources. Non-ARV drug costs were obtained from published literature and a cost database. All costs were calculated as year-2009 euros. The annual discount rate was set at 3.0%. The main outcomes were cost per life-year gained (LYG) and cost per quality-adjusted life-year (QALY) gained. Uncertainty was assessed with one-way and probabilistic sensitivity analyses.

RESULTS

In the model analysis, adding maraviroc to OBT was associated with an increase of 0.952 LYG and 0.909 QALY. Total costs were €275,970 for maraviroc plus OBT and €254,655 for placebo plus OBT (difference: €21,315). The incremental cost per LYG was €22,398 and the incremental cost per QALY gained was €23,457. The model appeared to be robust for variations in key parameters. Results from the probabilistic sensitivity analyses indicated that the probability of the cost per QALY being below €30,000 was 99%.

CONCLUSION

Despite the limitations of the model, our analysis suggested that OBT plus maraviroc 300 mg BID is a clinically valuable option, and cost-effective from the perspective of the Spanish health care system, for previously treated patients with R5 HIV-1 infection.

[Analysis of the prevalence of CCR5 coreceptor antagonist resistance mutations among HIV-1 variants in Russia]

The authors studied the prevalence of mutations associated with resistance to the CCRS coreceptor antagonists maraviroc and vicriviroc in Russia. Most (93.6%) patients infected with HIV-1 genetic subtype A (IDU-A), predominant in the CIS countries, were found to have maraviroc resistance mutations. These mutations appear to reflect the natural genome polymorphism characteristic of the variant IDU-A. Maraviroc resistance mutations were of limited occurrence (2.8%) among the samples of virus subtype B in Russia. There were no vicriviroc resistance mutations in both the HIV-1 genetic variant IDU-A and the samples of virus subtype B. There is a need for further clinical studies evaluating the real impact of these mutations on the efficacy of maraviroc in patients infected with the HIV-1 genetic variant IDU-A.

Direct measurement of thermal stability of expressed CCR5 and stabilization by small molecule ligands

The inherent instability of heptahelical G protein-coupled receptors (GPCRs) during purification and reconstitution is a primary impediment to biophysical studies and to obtaining high-resolution crystal structures. New approaches to stabilizing receptors during purification and screening reconstitution procedures are needed. Here we report the development of a novel homogeneous time-resolved fluorescence assay (HTRF) to quantify properly folded CC-chemokine receptor 5 (CCR5). The assay permits high-throughput thermal stability measurements of femtomole quantities of CCR5 in detergent and in engineered nanoscale apolipoprotein-bound bilayer (NABB) particles. We show that recombinantly expressed CCR5 can be incorporated into NABB particles in high yield, resulting in greater thermal stability compared with that of CCR5 in a detergent solution. We also demonstrate that binding of CCR5 to the HIV-1 cellular entry inhibitors maraviroc, AD101, CMPD 167, and vicriviroc dramatically increases receptor stability. The HTRF assay technology reported here is applicable to other membrane proteins and could greatly facilitate structural studies of GPCRs.

Update on microbicide research and development - seeking new HIV prevention tools for women

Women and girls are especially vulnerable to HIV infection in sub-Saharan Africa, and in some of those countries, prevalence among young women can be up to 3 times higher than among men of the same age. Effective HIV prevention options for women are clearly needed in this setting. Several ARV-based vaginal microbicides are currently in development for prevention of HIV transmission to women and are discussed here. The concept of pre-exposure prophylaxis for the prevention of HIV transmission to women is introduced.

[Our experience with maraviroc treatment in HIV positive patients]

BACKGROUND; Although antiretroviral therapy has changed the clinical course of HIV infection, AIDS remains an incurable disease. Virus entry inhibitors, including maraviroc as the only registered representative of the class, represent a newly emerged group of anti-retrovirals with novel mechanism of action. The primary endpoint is to evaluate the clinical efficacy parameter of maraviroc by measuring viral load at the end of the 4 week treatment period. The secondary endpoint is to evaluate the effectiveness of the drug by monitoring the changes of the viral load values and CD4+ cell counts during the period of 125 weeks. Drug safety was also assessed.

METHODS AND RESULTS

Data of 23 subjects were collected, 21 patients were from the Czech Republic and 2 patients from France. Decrease in viral load in the 4th, 24th and 48th week was more than two orders of magnitude (-2.136; -2.448; -2.452 log10 copies/ml). The CD4+ cell count increased (71.71, 143.00, 196.43 cells/mm3). Drug safety was assessed by monitoring the frequency of adverse effects. The data obtained were compared with the III. phase of clinical trials.

CONCLUSIONS

Our experience with maraviroc was positive. Maraviroc proved to be an effective antiretroviral agent for a combination therapy of HIV infection.

Indications for the use of next-generation antiretroviral drugs in current clinical practice

OBJECTIVE

To describe the indications for use, in medical practice, of next-generation antiretroviral drugs (NGA): darunavir, raltegravir, maraviroc and etravirine.

METHOD

An observational, transversal and descriptive study conducted in adult patients who have started to receive a NGA between May 2008 and April 2009. The variables associated with the use of NGA were defined as follows: a) Variables related to efficacy: resistance confirmed by geno/phenotype tests or potencial resistance as a result of extensive exposure to antiretroviral agents, and/or severe immunological deterioration (CD4 less than 200 cells/mcl). b) Variables related to safety: prior toxicity to classic antiretroviral drugs and/or comorbidity which compromises their use. c) Combined efficacy and safety variable (main variable): prioritizing the variables which were detected, the patients were classified into three groups: multiresistant geno/phenotype (multi-G/P), multiresistant as a result of treatment history and other situations. Data was obtained from electronic medical records, laboratory tests, and records of interviews and drugs dispensed by the Pharmacy Service.

RESULTS

Seventy three patients, 40% of whom had an undetectable viral load and 38.4% who showed severe immunological deterioration, were included in the study. Multi-G/P occurred in 45% and multiresistance as a result of treatment history was found in 33% of patients. Patients classified as belonging to the "other situations" category were characterized by having a greater viral load and a poorer immunological status. In 90% of the patients without multi-G/P two or more variables associated with the use of NGA were detected.

DISCUSSION

The medical reality of using NGA shows that they play a role in clinical situations which are very different, specific and difficult to manage.

Oral pre-exposure prophylaxis by anti-retrovirals raltegravir and maraviroc protects against HIV-1 vaginal transmission in a humanized mouse model

Sexual HIV-1 transmission by vaginal route is the most predominant mode of viral transmission, resulting in millions of new infections every year. In the absence of an effective vaccine, there is an urgent need to develop other alternative methods of pre-exposure prophylaxis (PrEP). Many novel drugs that are currently approved for clinical use also show great potential to prevent viral sexual transmission when administered systemically. A small animal model that permits rapid preclinical evaluation of potential candidates for their systemic PrEP efficacy will greatly enhance progress in this area of investigation. We have previously shown that RAG-hu humanized mouse model permits HIV-1 mucosal transmission via both vaginal and rectal routes and displays CD4 T cell loss typical to that seen in the human. Thus far systemic PrEP studies have been primarily limited to RT inhibitors exemplified by tenofovir and emtricitabine. In these proof-of-concept studies we evaluated two new classes of clinically approved drugs with different modes of action namely, an integrase inhibitor raltegravir and a CCR5 inhibitor maraviroc as potential systemically administered chemo-prophylactics. Our results showed that oral administration of either of these drugs fully protects against vaginal HIV-1 challenge in the RAG-hu mouse model. Based on these results both these drugs show great promise for further development as orally administered PrEPs.

The evolutionary analysis of emerging low frequency HIV-1 CXCR4 using variants through time--an ultra-deep approach

Large-scale parallel pyrosequencing produces unprecedented quantities of sequence data. However, when generated from viral populations current mapping software is inadequate for dealing with the high levels of variation present, resulting in the potential for biased data loss. In order to apply the 454 Life Sciences' pyrosequencing system to the study of viral populations, we have developed software for the processing of highly variable sequence data. Here we demonstrate our software by analyzing two temporally sampled HIV-1 intra-patient datasets from a clinical study of maraviroc. This drug binds the CCR5 coreceptor, thus preventing HIV-1 infection of the cell. The objective is to determine viral tropism (CCR5 versus CXCR4 usage) and track the evolution of minority CXCR4-using variants that may limit the response to a maraviroc-containing treatment regimen. Five time points (two prior to treatment) were available from each patient. We first quantify the effects of divergence on initial read k-mer mapping and demonstrate the importance of utilizing population-specific template sequences in relation to the analysis of next-generation sequence data. Then, in conjunction with coreceptor prediction algorithms that infer HIV tropism, our software was used to quantify the viral population structure pre- and post-treatment. In both cases, low frequency CXCR4-using variants (2.5-15%) were detected prior to treatment. Following phylogenetic inference, these variants were observed to exist as distinct lineages that were maintained through time. Our analysis, thus confirms the role of pre-existing CXCR4-using virus in the emergence of maraviroc-insensitive HIV. The software will have utility for the study of intra-host viral diversity and evolution of other fast evolving viruses, and is available from http://www.bioinf.manchester.ac.uk/segminator/.

Two-year safety and virologic efficacy of maraviroc in treatment-experienced patients with CCR5-tropic HIV-1 infection: 96-week combined analysis of MOTIVATE 1 and 2

BACKGROUND

Maraviroc, the first approved CCR5 antagonist, demonstrated 48-week safety and virologic efficacy in CCR5-tropic HIV-infected, treatment-experienced patients; however, critical longer-term safety and durability of responses are unknown.

METHODS

Two-year follow-up of 2 prospective, randomized, blinded studies of maraviroc once daily or twice daily, or placebo in treatment-experienced patients with R5-tropic HIV-1 receiving an optimized background regimen. Unblinding occurred after the week-48 visit of the last enrolled patient. Safety and virologic parameters were assessed through week 96.

RESULTS

One thousand forty-nine patients were randomized and received study drugs. HIV-1 RNA was <50 copies per milliliter at week 96 in 39% and 41% of patients receiving maraviroc every day or twice a day, respectively. Among patients with HIV-1 RNA <50 copies per milliliter at week 48, 81% and 87% of patients receiving maraviroc every day or twice a day, respectively, maintained this response at week 96. At week 96, median CD4+ T-cell counts increased from baseline by 89 and 113 cells per cubic millimeter with maraviroc every day and twice a day, respectively. Exposure-adjusted rates of adverse events were similar with maraviroc or placebo. No new or unexpected events were observed after week 48.

CONCLUSIONS

Maraviroc-containing antiretroviral regimens maintained durable responses in treatment-experienced patients with R5 HIV-1 through 96 weeks of treatment with a safety profile similar to placebo.

C-C chemokine receptor type 5 (CCR5) utilization of transmitted and early founder human immunodeficiency virus type 1 envelopes and sensitivity to small-molecule CCR5 inhibitors

The envelope glycoprotein (Env) of human immunodeficiency virus is key to viral entry of susceptible target cells and is therefore a major target for the design of vaccines and antiviral drugs. C-C chemokine receptor type 5 (CCR5)-using (R5) Env is the predominant phenotype associated with early transmission and acute infection. This study investigated the mechanism of CCR5 use and the sensitivity to CCR5 inhibitors of a panel of transmitted or early founder (T/F) Envs. The data showed that the majority of T/F Envs used CCR5 and that many also used CCR3, although less efficiently. Despite a similar ability to use wild-type CCR5, individual Envs differed significantly in their sensitivity to the CCR5 inhibitors maraviroc, CMPD-167 and SCH-412147. Inhibitor mapping experiments demonstrated that maraviroc, CMPD-167 and SCH-412147 interfered with the binding of CCR5 mAb to the C-terminal half of the second extracellular loop 2 of CCR5. Interestingly, Envs resistant to maraviroc, CMPD167 and SCH-412147 remained sensitive to TAK-779. Further studies indicated that the sensitivity of Envs to CCR5 inhibitors correlated with the molecular anatomy of CCR5 use, revealing that the inhibitor-sensitive Envs barely used the CCR5 N terminus, whereas resistant Envs showed a marked increase in its use. Taken together, these findings demonstrate that T/F R5 Envs are heterogeneous with respect to the mechanisms of CCR5 utilization. These data may have implications for therapeutic and prophylactic use of CCR5-based antiretrovirals.

Cost-effectiveness of maraviroc for antiretroviral treatment-experienced HIV-infected individuals in Mexico

OBJECTIVE

Maraviroc is the first approved drug in a new class of antiretrovirals, the CCR5 antagonists. The objective of this study was to predict the long-term clinical impact and cost-effectiveness of maraviroc in treatment-experienced adults with HIV/AIDS in Mexico.

METHODS

The AntiRetroviral Analysis by Monte Carlo Individual Simulation (ARAMIS) model was adapted to the Mexican context to predict clinical and economic outcomes of treating with optimized background therapy (OBT) versus testing for viral tropism status and treating with OBT ± maraviroc accordingly in treatment-experienced adults in Mexico. Baseline characteristics and efficacy were from the MOTIVATE trials' screening cohort. Costs and population mortality data were specific to Mexico. Results were reported from the perspective of health care payers in 2008 Mexican pesos (converted to 2008 US$ in parentheses).

RESULTS

Compared to treatment with OBT alone, treatment with OBT ± maraviroc contingent on tropism test result increased projected undiscounted life expectancy and discounted quality-adjusted life expectancy from 7.54 to 8.71 years and 4.42 to 4.92 quality-adjusted life years (QALYs), respectively, at an incremental cost of $228,215 (US$21,329). The resultant incremental cost-effectiveness ratio (ICER) was $453,978 (US$42,429) per QALY gained. The ICER was somewhat lower when maraviroc was modeled in individuals susceptible to ≤ 2 components of OBT ($407,329; US$38,069), while the ICER was higher in individuals susceptible to ≥3 OBT components ($718,718; US$67,171).

CONCLUSION

In treatment-experienced individuals with HIV/AIDS in Mexico, maraviroc may be cost-effective, particularly in individuals with limited options for active antiretroviral therapy (ART).

Maraviroc first-line therapy for HIV infection. Too risky

First-line treatment for HIV infection currently comprises a combination of antiretroviral drugs, including a non-nucleoside reverse transcriptase inhibitor such as efavirenz, or one or two protease inhibitors.The choice is based on the results of initial clinical trials of antiretroviral drugs with morbidity and mortality endpoints, and, since the 1990s, on trials with surrogate markers (viral load and the CD4+ T lymphocyte count). Maraviroc is the only CCR5 antagonist currently on the market. Drugs belonging to this class are designed to prevent HIV entry into CD4 T lymphocytes. Maraviroc is reserved for patients with multiple treatment failure, but has also been proposed for first-line treatment. Clinical evaluation of maraviroc in first-line treatment is limited to a single comparative trial designed to show the virological and immunological "non-inferiority" of the maraviroc + zidovudine + lamivudine combination versus efavirenz + zidovudine + lamivudine, after 96 weeks of treatment, in 721 patients with CCR5-tropic HIV strains. A more sensitive version of the test used to determine CCR5 tropism became available during the trial, leading to the exclusion of 107 patients who were infected by strains capable of using other coreceptors. This trial fails to answer important questions regarding the adverse effects of maraviroc, such as hepatotoxicity, infections, cancer, and cardiovascular disorders. Tests used to identify exclusively CCR5-tropic HIV strains are difficult to implement and their results are unreliable. This means that some patients in whom maraviroc will not be effective may receive this drug, and will thus be at risk of developing viral resistance to other drugs in their antiretroviral regimen. In practice, first-line use of maraviroc is imprudent, as it depends on a test of uncertain reliability. Furthermore, there is no evidence to suggest that maraviroc combination therapy has a better risk-benefit balance than regimens with well-documented and long established efficacy.