Outcomes of multidrug-resistant patients switched from enfuvirtide to raltegravir within a virologically suppressive regimen

Short communication: Effectiveness at 48 weeks of switching from enfuvirtide to raltegravir in virologically suppressed multidrug-resistant HIV type 1-infected patients in a Brazilian cohort

The effectiveness of switching from enfuvirtide to raltegravir in HIV-1-infected patients on a suppressive antiretroviral regimen has been poorly studied in the clinical practice of developing countries. We conducted a multicenter retrospective cohort study in HIV-1-infected, multidrug-experienced adults (≥18 years old) with plasma HIV-1-RNA <400 copies/ml for at least 4 months on an enfuvirtide-containing therapy between 2005 and 2010, in whom the attending physician switched from enfuvirtide to raltegravir. Effectiveness endpoints were measured at week 48 after switch. Analyses were conducted on an intent-to-treat basis and two strategies for handling missing outcome data were used (hereafter, strategies 1 and 2). Overall, 87 patients were eligible for analysis. At baseline, the median CD4(+) T cell count was 400 cells/μl and 91.9% of patients had <50 HIV-1-RNA copies/ml. At week 48, the proportions of patients with plasma HIV-1-RNA <50 and <400 copies/ml were, respectively, 86.2% (95% CI=77.1; 92.7%) and 88.5% (95% CI=79.9; 94.3%) (strategies 1 and 2) and 89.7% (95% CI=81.3; 95.2%) and 90.8% (95% CI=82.7; 95.9%) (strategies 1 and 2). This was a -10.3% (95% CI=-2.8; -17.9%) and -9.2% (95% CI=-2; -16.4%) difference from baseline in the proportion of patients with plasma HIV-1-RNA <400 copies/ml. The median increase in CD4(+) T cell counts was 41 and 64 cells/μl (p<0.001) (strategies 1 and 2). No patient withdrew raltegravir or developed opportunistic infections, but one was diagnosed with HIV-related dementia. In conclusion, switching from enfuvirtide to raltegravir in patients on a virologically suppressive regimen is an effective strategy even in a Brazilian clinical setting.

[Consensus Statement by GeSIDA/National AIDS Plan Secretariat on antiretroviral treatment in adults infected by the human immunodeficiency virus (Updated January 2013)]

OBJECTIVE

This consensus document is an update of combined antiretroviral therapy (cART) guidelines for HIV-1 infected adult patients.

METHODS

To formulate these recommendations a panel composed of members of the GeSIDA/National AIDS Plan Secretariat (Grupo de Estudio de Sida and the Secretaría del Plan Nacional sobre el Sida) reviewed the efficacy and safety advances in clinical trials, cohort and pharmacokinetic studies published in medical journals (PubMed and Embase) or presented in medical scientific meetings. The strength of the recommendations and the evidence which support them are based on a modification of the criteria of Infectious Diseases Society of America.

RESULTS

cART is recommended in patients with symptoms of HIV infection, in pregnant women, in serodiscordant couples with high risk of transmission, in hepatitisB co-infection requiring treatment, and in HIV nephropathy. cART is recommended in asymptomatic patients if CD4 is <500cells/μl. If CD4 are >500cells/μl cART should be considered in the case of chronic hepatitisC, cirrhosis, high cardiovascular risk, plasma viral load >100.000 copies/ml, proportion of CD4 cells <14%, neurocognitive deficits, and in people aged >55years. The objective of cART is to achieve an undetectable viral load. The first cART should include 2 reverse transcriptase inhibitors (RTI) nucleoside analogs and a third drug (a non-analog RTI, a ritonavir boosted protease inhibitor, or an integrase inhibitor). The panel has consensually selected some drug combinations, for the first cART and specific criteria for cART in acute HIV infection, in tuberculosis and other HIV related opportunistic infections, for the women and in pregnancy, in hepatitisB or C co-infection, in HIV-2 infection, and in post-exposure prophylaxis.

CONCLUSIONS

These new guidelines update previous recommendations related to first cART (when to begin and what drugs should be used), how to monitor, and what to do in case of viral failure or adverse drug reactions. cART specific criteria in comorbid patients and special situations are similarly updated.

Clinical use of HIV integrase inhibitors: a systematic review and meta-analysis

Background

Optimal regimen choice of antiretroviral therapy is essential to achieve long-term clinical success. Integrase inhibitors have swiftly been adopted as part of current antiretroviral regimens. The purpose of this study was to review the evidence for integrase inhibitor use in clinical settings.

Methods

MEDLINE and Web-of-Science were screened from April 2006 until November 2012, as were hand-searched scientific meeting proceedings. Multiple reviewers independently screened 1323 citations in duplicate to identify randomized controlled trials, nonrandomized controlled trials and cohort studies on integrase inhibitor use in clinical practice. Independent, duplicate data extraction and quality assessment were conducted.

Results

48 unique studies were included on the use of integrase inhibitors in antiretroviral therapy-naive patients and treatment-experienced patients with either virological failure or switching to integrase inhibitors while virologically suppressed. On the selected studies with comparable outcome measures and indication (n = 16), a meta-analysis was performed based on modified intention-to-treat (mITT), on-treatment (OT) and as-treated (AT) virological outcome data. In therapy-naive patients, favorable odds ratios (OR) for integrase inhibitor-based regimens were observed, (mITT OR 0.71, 95% CI 0.59–0.86). However, integrase inhibitors combined with protease inhibitors only did not result in a significant better virological outcome. Evidence further supported integrase inhibitor use following virological failure (mITT OR 0.27; 95% CI 0.11–0.66), but switching to integrase inhibitors from a high genetic barrier drug during successful treatment was not supported (mITT OR 1.43; 95% CI 0.89–2.31). Integrase inhibitor-based regimens result in similar immunological responses compared to other regimens. A low genetic barrier to drug-resistance development was observed for raltegravir and elvitegravir, but not for dolutegravir.

Conclusion

In first-line therapy, integrase inhibitors are superior to other regimens. Integrase inhibitor use after virological failure is supported as well by the meta-analysis. Careful use is however warranted when replacing a high genetic barrier drug in treatment-experienced patients switching successful treatment.

Cost-Effectiveness of Antiretroviral Therapy for Multidrug-Resistant HIV: Past, Present, and Future

In the early years of the highly active antiretroviral therapy (HAART) era, HIV with resistance to two or more agents in different antiretroviral classes posed a significant clinical challenge. Multidrug-resistant (MDR) HIV was an important cause of treatment failure, morbidity, and mortality. Treatment options at the time were limited; multiple drug regimens with or without enfuvirtide were used with some success but proved to be difficult to sustain for reasons of tolerability, toxicity, and cost. Starting in 2006, data began to emerge supporting the use of new drugs from the original antiretroviral classes (tipranavir, darunavir, and etravirine) and drugs from new classes (raltegravir and maraviroc) for the treatment of MDR HIV. Their availability has enabled patients with MDR HIV to achieve full and durable viral suppression with more compact and cost-effective regimens including at least two and often three fully active agents. The emergence of drug-resistant HIV is expected to continue to become less frequent in the future, driven by improvements in the convenience, tolerability, efficacy, and durability of first-line HAART regimens. To continue this trend, the optimal rollout of HAART in both rich and resource-limited settings will require careful planning and strategic use of antiretroviral drugs and monitoring technologies.

Virologic suppression in treatment-experienced patients after virologic rebound or failure of therapy

PURPOSE OF REVIEW

To discuss factors related to virologic failure and review data from recent clinical trials evaluating re-suppression of viremia in extensively-treated HIV-infected patients with resistance.

RECENT FINDINGS

Factors associated with virologic failure can be related to the virus (e.g. resistance), the patient (e.g. adherence) or HIV therapy (e.g. availability) and must be analyzed to minimize the likelihood of a new failure. Recent clinical trials have shown that it is now possible to achieve virologic suppression in a large proportion of treatment-experienced patients with extensive drug resistance, with several newer agents demonstrating favorable potency, tolerability and long-term efficacy.

SUMMARY

The benefits of highly active antiretroviral treatment are well recognized, and adding at least two (preferably three) new active drugs to an optimized background regimen can provide effective suppression of viremia even in multidrug-experienced patients. Changing drugs or regimen simplification should be considered when treatment is inadequate, poorly tolerated or associated with poor adherence, and is made easier by the newer agents and formulations now available. Newer antiretrovirals may contribute to a better quality of life and life expectancy in patients with few or no therapy options, although adherence is paramount in ensuring their continued effectiveness.

Cost-effectiveness of raltegravir in HIV/AIDS

Raltegravir is a first-in-class HIV-1 integrase inhibitor with established antiviral efficacy in treatment-naive and treatment-experienced patients with multidrug-resistant HIV-1 infection. In this article, we summarize pharmacoeconomic evaluations of raltegravir-based treatment regimens, compared with alternative therapies, in the treatment of patients with HIV infection and/or AIDS. Cost-effectiveness evaluations of raltegravir in treatment-experienced patients conducted using a continuous-time, state-transition Markov cohort model suggest that raltegravir, combined with optimized background therapy, falls within the range that would generally be considered cost effective compared with optimized therapy alone in Spanish, Swiss and UK health systems. In treatment-naive populations, raltegravir was evaluated using a three-stage continuous-time state-transition cohort model. Raltegravir-based initiation treatment strategies (first-line raltegravir) were compared with protease inhibitor and non-nucleoside reverse-transcriptase inhibitor initiation strategies, in which raltegravir was retained for salvage therapy. First-line raltegravir was cost-effective versus retaining raltegravir for salvage therapy in several European populations. A separate economic model was used to evaluate first-line raltegravir against two alternative initiation regimens representing standard clinical practice in Australia; raltegravir proved to be cost effective in both scenarios. In all studies examined, results were sensitive to factors including treatment duration, mortality rate, analytic time horizon, health utility weights, cost of raltegravir and optimized therapy, incidence of opportunistic infection and discount rates. Nonetheless, raltegravir remained cost effective under most scenarios.

Efficacy and safety of raltegravir in treatment-experienced HIV-1-infected patients switching from enfuvirtide-based regimens: 48 week results of the randomized EASIER ANRS 138 trial

OBJECTIVES

To assess the sustainable efficacy and safety of a switch from enfuvirtide to raltegravir in patients with multidrug-resistant HIV infection.

METHODS

One hundred and seventy patients with multidrug-resistant HIV infection and suppressed plasma HIV RNA levels < 400 copies/mL under an enfuvirtide-based regimen were randomized to maintain their regimen or to switch to a raltegravir-based regimen (immediate group) in a 48 week prospective, randomized, open-label trial. At week 24, patients in the maintenance arm also switched to raltegravir (deferred group). Baseline genotypic susceptibility scores (GSSs) were calculated using available historical resistance tests. Efficacy was assessed by the cumulative proportion of patients with virological failure, defined as a confirmed plasma HIV RNA ≥ 400 copies/mL up to week 48. The EASIER ANRS 138 trial is registered at ClinicalTrials.gov (NCT00454337).

RESULTS

At baseline, 86% of patients had plasma HIV RNA levels <50 copies/mL and 86% had a GSS ≥ 1. Through to week 48, in the on-treatment analysis, only one patient in the immediate group, with a GSS of 0, developed virological failure. At week 48, 90% of patients in both the immediate and deferred groups had plasma HIV-1 RNA levels <50 copies/mL. Median CD4 cell counts remained stable during follow-up. Of note, 12 of 66 (18.2%) patients receiving a regimen combining raltegravir and ritonavir-boosted tipranavir experienced alanine aminotransferase elevations, which led to a switch from tipranavir to darunavir in 8 cases, without discontinuation of raltegravir.

CONCLUSIONS

In well-suppressed patients with multidrug-resistant HIV infection, a switch from enfuvirtide to raltegravir is generally well tolerated and has sustained antiviral efficacy when combined with a potent background regimen.

Enfuvirtide: from basic investigations to current clinical use

IMPORTANCE OF THE FIELD

Drug resistance is a major challenge in the treatment of HIV infection. Enfuvirtide is the first entry inhibitor to have been approved for clinical use.

AREAS COVERED IN THIS REVIEW

Relevant information through searches of MEDLINE (1998 to June 2010) and meeting abstracts of major HIV/AIDS conferences (2003 - June 2010) using the search terms 'enfuvirtide', 'T-20' and 'fusion inhibitor'.

WHAT THE READER WILL GAIN

Enfuvirtide blocks HIV fusion to host cells. It works against the different HIV-1 variants but is not active against HIV-2. The recommended dosage of enfuvirtide is 90 mg b.i.d. subcutaneously. The two large Phase III pivotal clinical trials TORO 1 and 2 showed that enfuvirtide is an effective therapeutic option as rescue therapy in combination with other active antiretroviral drugs. Resistance to enfuvirtide is conferred by mutations in the HR1 region of gp41. Single and double mutations have been shown to result in high-level resistance to enfuvirtide. Postmarketing studies have been helpful to define more precisely the place of enfuvirtide in the sequence of antiretroviral therapy.

TAKE HOME MESSAGE

The emergence of new compounds and new classes of drugs, highly active against multiresistant virus but more convenient to administer than enfuvirtide, will probably prevent the extensive use of enfuvirtide. This drug remains attractive in some subgroups of patients because of its excellent systemic tolerance and the lack of interactions with the major cytochrome P450 isoenzymes.

Novel integrase inhibitors for HIV

IMPORTANCE OF THE FIELD

Integrase inhibitors are the newest class of antiretroviral agents developed to treat HIV-1 infection. Raltegravir (RAL), the only integrase inhibitor (INI) currently approved for the treatment of HIV-infected patients, has proven to be a potent and well-tolerated antiretroviral (ARV) agent. It is currently approved and used for the treatment of both ARV-experienced and ARV-naive patients. Nevertheless, the relatively low genetic barrier for resistance of RAL encourages the search for new INIs with different mechanisms of actions and resistance profiles.

AREAS COVERED IN THIS REVIEW

Here we review the data available about INI that are currently being tested in clinical trials or are in preclinical development: elvitegravir (EVG), S/GSK1349572, S/GSK1265744 and LEDGINs. We focus on their clinical efficacy, pharmacokinetic, safety and resistance profiles.

WHAT THE READER WILL GAIN

Up-to-date overview on the currently available, clinically relevant INIs and promising preclinical inhibitors at all phases of development.

TAKE HOME MESSAGE

Integrase inhibitors represent the newest therapeutic class available to treat HIV-1 infection. There are a variety of compounds either available in the clinic (RAL), advancing to Phase III trials (EVG), or in earlier phases of development. Taken together, this class offers new treatment options for the HIV-infected individual.

Impact on health-related quality of life of a switch from enfuvirtide to raltegravir among multidrug-resistant HIV-1-infected patients: a randomized open-label trial (EASIER-ANRS 138)

BACKGROUND

among multidrug-resistant HIV-1-infected patients, enfuvirtide has demonstrated sustained efficacy, but long-term use is inconvenient due to twice-daily subcutaneous injections which often induce injection-site reactions. We investigated whether a switch from enfuvirtide to raltegravir, an orally available HIV-integrase inhibitor, may improve health-related quality of life (HRQoL).

METHODS

170 multidrug-resistant HIV-1-infected patients who were receiving enfuvirtide-based regimens were randomised to the maintenance of enfuvirtide or the switch to raltegravir at day 0. At week 24, all patients received raltegravir up to week 48. HRQoL was assessed at baseline and weeks 24 and 48 using a self-report MOS-HIV questionnaire. HRQoL scores were compared between arms using analysis of covariance (ANCOVA) models.

RESULTS

at week 24, least-squares means changes from baseline for the maintenance and the substitution arms were -5.3 and +5.8 (P = .001) for the pain score, -4.7 and +4.8 (P = .02) for the social functioning score, and -1.3 and +2.0 (P = .003) for the physical summary score, respectively.

CONCLUSION

among multidrug-resistant HIV-1-infected patients, a switch from enfuvirtide to raltegravir resulted in statistically significant improvements in multiple HRQoL dimensions over 24 weeks in comparison to the maintenance under enfuvirtide.

Raltegravir: The evidence of its therapeutic value in HIV-1 infection

Introduction:

The antiretroviral treatment paradigm for human immunodeficiency virus-1 (HIV-1) infection has undergone a significant change with the addition of a new class of therapeutic agents targeting HIV-1 integrase (IN). IN inhibitors prevent the integration of viral DNA into the human genome and terminate the viral life cycle. As the first member of this new class of anti-HIV drugs, raltegravir has shown promising results in the clinic.

Aims:

To review the emerging evidence for the use of the IN inhibitor raltegravir in the treatment of HIV-1 infection.

Evidence review:

Strong evidence shows that raltegravir is effective in reducing the viral load to less than 50 copies/mL and increasing CD4 cell count in treatment-experienced patients with triple-drug class-resistant HIV-1 infection. Substantial evidence also indicates that while raltegravir is able to achieve treatment response in patients with drug-resistant HIV-1, it is susceptible to development of resistance. Raltegravir should be used with at least one other active drug. In addition to its use in salvage therapy upon failure of first-line antiretroviral treatment, a raltegravir-based treatment regimen may also be effective as initial therapy. Substantial evidence also shows that raltegravir-based treatment regimen is well tolerated with minimal clinically severe adverse events and toxicities. Modeling studies suggest a cost-effectiveness of US$21,339 per quality-adjusted life year gained with raltegravir use, though further direct evidence on quality of life and cost-effectiveness is needed.

Place in therapy:

Raltegravir shows significant and sustained virologic and immunologic response in combination with other antiretrovirals in treatment-experienced HIV-1 infected patients who show evidence of viral replication or multidrug-resistant HIV-1 strains, without any significant tolerability issues.

The use of integrase inhibitors in treatment-experienced patients

Raltegravir, the first approved HIV-1 integrase inhibitor, is able to block the strand transfer step of the HIV proviral DNA integration process into the cellular host DNA. The selected dosage for the pivotal phase III studies (subsequently approved by the regulatory agencies) was 400 mg bid by oral route with or without food. Raltegravir has a week effect (either inhibition or induction) on the hepatic cytochrone P450 activity. There is not need of dose adjustments in renal insufficiency or in mild-to-moderate hepatic impairment.

The emerging paradigm in the field of salvage therapy was to achieve a viral load below limit of detection in almost all patients. Pretty soon it became apparent that this was feasible in more than 70-90% of patients.

Raltegravir proved to be pivotal for this new paradigm. Raltegravir vs placebo both with an optimized background therapy has been tested for salvage therapy in the 005 and in the BENCHMRK studies (018 and 019). In all three studies proved to be superior to the placebo at 24, 48 and 96 weeks. Tolerance was remarkably good and virological failure was often associated with selection of integrase gene resistance mutations following the Y143C/H/R, Q148H/K/R o less frequently the NI55H paths.

Finally, in the two SWITCHMRK studies non-inferiority vs Lopinavir/r could not be demonstrated in virogically suppressed patients with an stable cART containing Lopinavir/r. Most likely explanation was the presence of archived resistance mutationts to background therapy leading to a functional monotherapy with raltegravir.

Efficacy and safety of switching from enfuvirtide to raltegravir in patients with virological suppression

OBJECTIVE

To assess the Efficacy and safety of switching from HAART containing enfuvirtide to raltegravir as a simplification strategy in patients with viral suppression and intolerance to enfuvirtide.

METHODS

Thirty-six patients with sustained plasma HIV RNA levels <50 copies/mL for at least 3 months with injection site reactions and/or injection fatigue while receiving an enfuvirtide-containing optimized background regimen switched from enfuvirtide to raltegravir (400 mg bid).

RESULTS

Patientshad received enfuvirtide for a median of 96 weeks and had sustained HIV RNA <50 copies/ mL for a median of 95 weeks. One patient discontinued raltegravir due to the appearance of cutaneous rash (grade 2) unresponsive to antihistamines after 19 days of starting raltegravir. The remaining 35 patients were followed for 24 weeks and 18 of them for 48 weeks. All patients maintained virological suppression <50 copies/mL at Weeks 24 and 48. No patient had blips in their viral load after switching to raltegravir. There were no grade 3 or 4 adverse events related to raltegravir.

CONCLUSIONS

A switch from enfuvirtide to raltegravir in virologically suppressed patients who are highly treatment-experienced maintained both virologic and immunologic efficacy up to 48 weeks.

Implementation of raltegravir in routine clinical practice: selection criteria for choosing this drug, virologic response rates, and characteristics of failures

BACKGROUND

Raltegravir (RAL) achieved remarkable virologic suppression rates in randomized-clinical trials, but today efficacy data and factors for treatment failures in a routine clinical care setting are limited.

METHODS

First, factors associated with a switch to RAL were identified with a logistic regression including patients from the Swiss HIV Cohort Study with a history of 3 class failure (n = 423). Second, predictors for virologic outcome were identified in an intent-to-treat analysis including all patients who received RAL. Last observation carried forward imputation was used to determine week 24 response rate (HIV-1 RNA >or= 50 copies/mL).

RESULTS

The predominant factor associated with a switch to RAL in patients with suppressed baseline RNA was a regimen containing enfuvirtide [odds ratio 41.9 (95% confidence interval: 11.6-151.6)]. Efficacy analysis showed an overall response rate of 80.9% (152/188), whereas 71.8% (84/117) and 95.8% (68/71) showed viral suppression when stratified for detectable and undetectable RNA at baseline, respectively. Overall CD4 cell counts increased significantly by 42 cells/microL (P < 0.001). Characteristics of failures were a genotypic sensitivity score of the background regimen <or=1, very low RAL plasma concentrations, poor adherence, and high viral load at baseline.

CONCLUSIONS

Virologic suppression rates in our routine clinical care setting were promising and comparable with data from previously published randomized-controlled trials.

Integrase inhibitors in salvage therapy regimens for HIV-1 infection

PURPOSE OF REVIEW

To review current knowledge and the role of integrase inhibitors in the setting of HIV salvage therapy. We will discuss results from recent studies and literature and comment on the potential for integrase inhibitors in defined clinical settings.

RECENT FINDINGS

Raltegravir has been studied most intensively in treatment-experienced patients and is the first integrase inhibitor that has been licensed for use in this patient group. Most studies have shown good tolerability data and very potent virus suppression. In patients with limited treatment options, switching from enfuvirtide appears to be well tolerated, whereas switching from a protease inhibitor-based regimen may increase the rates of viral failure. Elvitegravir also showed good results in early phase clinical trials and is currently undergoing phase III clinical trials.

SUMMARY

Given that integrase inhibitors belong to a new class of antiretroviral agents with a diverse drug resistance profile, and are active against both chemokine (C-C motif) receptor 5 and chemokine (C-X-C motif) receptor 4 strains, they are exciting additions to salvage therapy regimen. Raltegravir and elvitegravir are metabolized via different pathways, which will affect their respective use. The major limitation for the use of integrase inhibitors is a potentially low threshold for viral drug resistance, so functional monotherapy must be avoided.

Switch to a raltegravir-based regimen versus continuation of a lopinavir-ritonavir-based regimen in stable HIV-infected patients with suppressed viraemia (SWITCHMRK 1 and 2): two multicentre, double-blind, randomised controlled trials

BACKGROUND

To reduce lipid abnormalities and other side-effects associated with antiretroviral regimens containing lopinavir-ritonavir, patients might want to switch one or more components of their regimen. We compared substitution of raltegravir for lopinavir-ritonavir with continuation of lopinavir-ritonavir in HIV-infected patients with stable viral suppression on lopinavir-ritonavir-based combination therapy.

METHODS

The SWITCHMRK 1 and 2 studies were multicentre, double-blind, double-dummy, phase 3, randomised controlled trials. HIV-infected patients aged 18 years or older were eligible if they had documented viral RNA (vRNA) concentration below the limit of assay quantification for at least 3 months while on a lopinavir-ritonavir-based regimen. 707 eligible patients were randomly allocated by interactive voice response system in a 1:1 ratio to switch from lopinavir-ritonavir to raltegravir (400 mg twice daily; n=353) or to remain on lopinavir-ritonavir (two 200 mg/50 mg tablets twice daily; n=354), while continuing background therapy consisting of at least two nucleoside or nucleotide reverse transcriptase inhibitors. Primary endpoints were the mean percentage change in serum lipid concentrations from baseline to week 12; the proportion of patients with vRNA concentration less than 50 copies per mL at week 24 (with all treated patients who did not complete the study counted as failures) with a prespecified non-inferiority margin of -12% for each study; and the frequency of adverse events up to 24 weeks. Analyses were done according to protocol. These trials are registered with ClinicalTrials.gov, numbers NCT00443703 and NCT00443729.

FINDINGS

702 patients received at least one dose of study drug and were included in the efficacy and safety analyses for the combined trials (raltegravir, n=350; lopinavir-ritonavir, n=352). Percentage changes in lipid concentrations from baseline to week 12 were significantly greater (p<0.0001) in the raltegravir group than in the lopinavir-ritonavir group in each study, yielding combined results for total cholesterol -12.6%vs 1.0%, non-HDL cholesterol -15.0%vs 2.6%, and triglycerides -42.2%vs 6.2%. At week 24, 293 (84.4%, 95% CI 80.2-88.1) of 347 patients in the raltegravir group had vRNA concentration less than 50 copies per mL compared with 319 (90.6%, 87.1-93.5) of 352 patients in the lopinavir-ritonavir group (treatment difference -6.2%, -11.2 to -1.3). Clinical and laboratory adverse events occurred at similar frequencies in the treatment groups. There were no serious drug-related adverse events or deaths. The only drug-related clinical adverse event of moderate to severe intensity reported in 1% or more of either treatment group was diarrhoea, which occurred in ten patients in the lopinavir-ritonavir group (3%) and no patients in the raltegravir group. The studies were terminated at week 24 because of lower than expected virological efficacy in the raltegravir group compared with the lopinavir-ritonavir group.

INTERPRETATION

Although switching to raltegravir was associated with greater reductions in serum lipid concentrations than was continuation of lopinavir-ritonavir, efficacy results did not establish non-inferiority of raltegravir to lopinavir-ritonavir.

FUNDING

Merck.

Integrase inhibitors: a novel class of antiretroviral agents

OBJECTIVE

To review the pharmacology, efficacy, safety, and resistance profiles of the integrase inhibitors raltegravir and elvitegravir.

DATA SOURCES

A search of PubMed was conducted (2000-August 2009) using the following key words: raltegravir, MK-0518, elvitegravir, and GS-9137. Articles were evaluated for content and bibliographies were reviewed. Data available exclusively in abstracts from major infectious diseases and HIV conferences were also evaluated for inclusion.

STUDY SELECTION AND DATA EXTRACTION

Studies included were in vitro investigations; Phase 1, 2, and 3 clinical trials; retrospective analyses including case reports; and pharmacokinetic and pharmacodynamic evaluations.

DATA SYNTHESIS

Raltegravir is currently approved by the Food and Drug Administration for the management of HIV-1 infection in treatment-naïve or-experienced adults as part of an optimized combination regimen. When combined with other active agents, it has demonstrated similar virologic efficacy after 96 weeks to the combination of efavirenz, tenofovir, and emtricitabine in treatment-naïve patients. Unlike many antiretrovirals, raltegravir does not enter cytochrome P450 metabolism and instead undergoes glucuronidation. Elvitegravir is in the late stages of clinical development. A Phase 2 study has demonstrated virologic efficacy in treatment-experienced patients comparable to protease inhibitor-based regimens after 24 weeks. Boosting of elvitegravir through inhibition of CYP3A4 metabolism has been investigated and suggests a pharmacokinetic profile conducive to once-daily-dosing. Phase 2 and 3 clinical trials evaluating boosted elvitegravir are in process. The Phase 2 trial combines elvitegravir with a non-ritonavir boosting agent plus tenofovir/emtricitabine given once daily as a "quad-pill" formulation. The Phase 3 trial compares once-daily ritonavir-boosted elvitegravir with twice-daily raltegravir, each given with an optimized background regimen. Both integrase inhibitors are well tolerated and raltegravir has few drug-drug interactions. Resistance mutations have been identified in patients experiencing virologic failure and cross resistance between raltegravir and elvitegravir has been confirmed.

CONCLUSIONS

The integrase inhibitors provide a novel target for antiretroviral therapy and provide an option for patients harboring resistance to other antiretrovirals.

Switch from enfuvirtide to raltegravir in virologically suppressed HIV-1 infected patients: effects on level of residual viremia and quality of life

BACKGROUND

Raltegravir is a potential treatment option for virologically suppressed HIV-1 infected patients on enfuvirtide with injection site reactions.

OBJECTIVES

To characterize safety and efficacy of an enfuvirtide to raltegravir switch including changes in T-cells, quality of life, and residual viremia.

STUDY DESIGN

In patients with viral load <50 copies/mL and injection site reactions, enfuvirtide was switched to raltegravir without additional changes to the antiretroviral regimen. Virologic failure was defined as a viral load >1000 copies/mL or two consecutive viral load measurements between 50 and 1000 copies/mL (low-level viremia). Over the 24 week study, we compared changes in T-cells, injection site reactions, quality of life, and residual viremia, as measured through the single-copy assay which can detect plasma virus down to a single copy, using paired t-tests.

RESULTS

Fourteen patients with a median CD4+ T-cell count of 420 cells/microL were enrolled. After the switch, two patients experienced virologic failure due to confirmed low-level viremia. However, both patients subsequently were re-suppressed, one without any changes to his regimen. There was no change in CD4+ T-cell count. Injection site reactions resolved. However, there was little reported change in quality of life. The baseline median level of residual viremia was 6 copies/mL and did not change after the switch to raltegravir.

CONCLUSIONS

A switch to raltegravir in virologically suppressed patients on enfuvirtide is effective in maintaining immunologic and virologic control at 24 weeks but did not result in a change in residual viremia.

Virologic outcomes of changing enfuvirtide to raltegravir in HIV-1 patients well controlled on an enfuvirtide based regimen: 24-week results of the CHEER study

OBJECTIVES

To determine the safety and efficacy of changing enfuvirtide to raltegravir in HIV-1-infected patients with HIV-1 RNA below the level of quantification for at least 6 months on an enfuvirtide-containing antiretroviral regimen.

DESIGN

Prospective, nonrandomized, historical control study.

METHODS

Patients were recruited from 11 Kaiser Permanente HIV clinics in California. Those patients eligible for inclusion (>or=18 years old, well controlled on antiretroviral medications) had enfuvirtide changed to raltegravir 400 mg, given twice daily orally; all other background antiretrovirals remained unchanged. The primary end point was percentage of patients with HIV-1 RNA below the limit of quantification after 24 weeks of raltegravir therapy. Analyses were by intention to treat.

RESULTS

Fifty-two patients were enrolled in the trial. After 24 weeks of therapy with raltegravir, 49 (94.2%, confidence interval: 1.2% to 15.9%) patients had HIV-1 RNA levels below the limit of quantification. Patients had a median CD4 cell increase of 32 cells per cubic millimeter after 24 weeks of raltegravir therapy. Treatment satisfaction as measured by patient questionnaires improved with the raltegravir-containing regimen. Adverse events were infrequent and generally mild in nature.

CONCLUSIONS

In treatment-experienced patients on a stable virologically suppressive enfuvirtide-containing regimen, raltegravir can safely be substituted for enfuvirtide.

The fusion inhibitor enfuvirtide in recent antiretroviral strategies

PURPOSE OF REVIEW

The purpose of this review is to discuss recent pharmacological, virological, and clinical data that concern enfuvirtide usage in different antiretroviral combinations.

RECENT FINDINGS

Randomized, recent trials in multidrug-experienced patients suggest that antiretroviral combinations with enfuvirtide have excellent virological responses with new antiretroviral compounds, including darunavir, etravirine, raltegravir, vicriviroc, and maraviroc. Trials confirm long-term safety, in spite of moderate injection-site reactions or pain, and lack of significant interactions. Preliminary data suggest that switching from enfuvirtide to raltegravir is effective and using enfuvirtide in prophylaxis of mother-to-child transmission is well tolerated. To administer enfuvirtide in an intensification strategy in antiretroviral-naïve or experienced populations may accelerate virological decline.

SUMMARY

Dosage adaptations to renal insufficiency are not necessary with enfuvirtide. Spinal fluid concentrations and ombilic cord passage are negligible. Durability of virological responses with enfuvirtide in combinations has been confirmed, in spite of injection-site reactions and twice daily subcutaneous administration. Enfuvirtide should be used with at least one other fully active drug in optimized background therapy in multidrug-experienced populations, a possible exception being with entry inhibitors, which may further benefit from the addition of a third active drug. Data concerning enfuvirtide in antiretroviral combinations show accelerated viral load decline, and the possibility of switching from enfuvirtide to raltegravir without modification of optimized background therapy.

Raltegravir in the management of HIV-infected patients

Raltegravir has recently been licensed for the treatment of HIV-1 infection. Currently its use is limited to treatment-experienced patients and subjects with resistant virus. In addition to its activity in the setting of resistance and treatment failure, it appears to have great potential for first-line therapy and as a switch option for subjects with intolerance to other agents, as well. Overall tolerability in clinical trials was excellent, and the toxicity profile is non-overlapping with other agents, with no clear neuropsychiatric, gastrointestinal, or metabolic toxicity. Its metabolization occurs mainly via UGT1A1 rather than by the CYP450 system, resulting in a relatively unproblematic drug interaction profile. The independence of the compound from “boosting” of drug levels with ritonavir is an attractive feature for many patients suffering from ritonavir-associated side effects. However, it has to be dosed twice daily.

The unique effect of raltegravir on the establishment of viral latency makes it a logical component of treatment attempts aiming at reducing and controlling this viral sanctuary.

This review summarizes the clinical view on the role of this novel compound in HIV therapy.

Raltegravir: first integrase inhibitor for the treatment of HIV infection

Raltegravir is the first of the integrase inhibitors to have been approved for treating HIV-1-infected adult patients who have evidence of viral replication and HIV-resistant strains to multiple antiretroviral agents, in combination with other antiretroviral agents. Raltegravir is an inhibitor of strand transfer of reverse-transcribed viral DNA into the host genome, and is administered orally twice daily without boosting. Clinical and pharmacokinetic studies showed strong virological responses, with as yet unmet antiretroviral potency, as well as excellent metabolic tolerance, and a favorable drug drug interaction profile. Further evaluation of possible indications and strategies are needed in terms of long-term tolerability, resistance, penetration in different anatomical compartments, effect on reservoirs, new antiretroviral combinations, first-line treatment, and switching to and treatment intensifications with raltegravir.

Optimal use of raltegravir (Isentress(R)) in the treatment of HIV-infected adults - Canadian consensus guidelines

BACKGROUND AND OBJECTIVES

A meeting of a Canadian group with significant experience and knowledge in HIV management, consisting of five physicians, a pharmacist and an AIDS researcher, was convened. Their goal was to develop guidance for Canadian HIV-treating physicians on the appropriate use of raltegravir (MK-0518, Isentress(R), Merck Frosst Canada Inc) in HIV-infected adults.

METHODS

Evidence from the published literature and conference presentations, as well as expert opinions of the group members, was considered and evaluated to develop the recommendations. Feedback on the draft recommendations was obtained from this core group, as well as from five other physicians and scientists across Canada with expertise in HIV treatment and antiretroviral drug resistance, and experience in the use of raltegravir. The final recommendations represent the core group's consensus agreement once all feedback was considered.

RESULTS/CONCLUSIONS

Recommendations were developed to guide physicians in the optimal use of raltegravir. The issues considered included raltegravir's role in overall treatment strategy, efficacy, durability of effect, rate of viral load reduction, resistance, safety/toxicity, pharmacokinetics and drug interactions.

Reassessment of enfuvirtide's role in the management of HIV-1 infection

BACKGROUND

The development of new protease inhibitors, new non-nucleoside reverse transcriptase inhibitors and novel therapeutic drug classes has dramatically changed the approach to managing HIV-1 patients with multidrug resistant virus. This has led many clinicians to reevaluate the clinical utility of enfuvirtide.

OBJECTIVES

To summarize recent literature on enfuvirtide and to reassess enfuvirtide's role in the management of HIV-1 infection.

METHODS

MEDLINE (1990 to February Week 2 2008) and EMBASE (1990 to 2008 week 8) databases were searched using the following terms: 'enfuvirtide', 'Fuzeon', 'T20', 'HIV fusion inhibitors', and 'HIV entry inhibitor'; limits: English language. Reference lists of articles deemed relevant were hand searched for additional publications. Significant abstracts from recent international HIV conferences were also identified.

CONCLUSION

Enfuvirtide can optimize the response to new combinations of HIV-1 drug regimens in multiresistant patients. Its inclusion as an active agent is effective but use is impacted by its high cost, inconvenient route of administration and cosmetic side-effect profile.

Perspectives on antiviral drug development

The 21st International Conference on Antiviral Research provided novel insights and approaches to drug discovery across a wide array of virologic fields. Topics ranged from the chemical synthesis of new compounds against the human immunodeficiency virus (HIV) to the long-term use of established drugs against influenza. A session on novel targets for HIV therapy focused on the importance of Apobec3G, LEDGF/p75 and other cellular factors as innovative ways to control infection. New targets for hepatitis B and C viruses were surveyed. There were also discussions as to how the development of new antiviral compounds might lead to novel mechanisms of drug resistance by HIV, herpesviruses and hepatitis viruses. These covered such issues as transmission dynamics, viral fitness, the acquisition of differential resistance patterns depending on viral subtype, and clinical outcomes. Drug efficacy, toxicity, patient adherence, treatment interruption and the importance of generic drugs in resource-poor settings were also extensively discussed. These topics will all play a pivotal role in drug development and the management of viral infections in the years to come.