Mechanism of virologic failure after substitution of a protease inhibitor by nevirapine in patients with suppressed plasma HIV-1 RNA

Evaluation of nevirapine-switch strategies for HIV treatment

Despite the benefits of protease inhibitor (PI)-based HIV treatment, issues of tolerability, dosing frequency, pill count and long-term metabolic complications necessitate evaluation of alternate treatment strategies. The weight of evidence demonstrates that a switch from a PI-based regimen to one containing nevirapine can be accomplished safely while maintaining virological suppression. There is no immunological cost. There is probably an overall benefit in terms of the metabolic milieu.

Improvement in Dyslipidaemia after Switching Stavudine to Tenofovir and Replacing Protease Inhibitors with Efavirenz in HIV-Infected Children

Objective

To assess the impact on immunological, virological and metabolic parameters of replacing protease inhibitors (PIs) with efavirenz and replacing stavudine with tenofovir in HIV-infected children.

Methods

A 48-week prospective evaluation of 28 HIV-infected children, with stable undetectable HIV-1 loads, who were taking highly active antiretroviral therapy (HAART) containing lamivudine, stavudine and a PI. Individuals were randomized to switch PI to efavirenz and stavudine to tenofovir at baseline (Group 1) or at week 24 (Group 2). Patient assessment included: clinical evaluation, viral load, CD4+ T-cell count, fasting blood levels and urine samples.

Results

All individuals maintained HIV RNA <50 copies/ml and unchanged CD4+ T-cell count through week 48. In Group 1 individuals, a significant decrease in cholesterol ( P<0.05), cholesterol:high-density lipoprotein (HDL) ratio ( P<0.01) and triglycerides ( P<0.05) was observed 24 and 48 weeks after the switch of HAART. The percentage of Group 1 children with increased cholesterol and triglycerides markedly decreased over the study period (from 43% to 0% and from 36% to 7%, respectively). In Group 2 individuals, unchanged lipids in the 24 weeks prior to the switch of HAART and a significant improvement on cholesterol ( P<0.05), cholesterol:HDL ratio ( P<0.01) and triglycerides ( P<0.05) were observed 24 weeks after the switch of HAART. The percentage of Group 2 children with increased cholesterol and triglycerides markedly decreased 24 weeks after the switch of HAART (from 46% to 7% and from 54% to 0%, respectively). Proteinuria and glucosuria were not detected in any individual. The mean values of serum creatinine, serum phosphorus, serum bicarbonate, estimated glomerular filtration rate, urinary microalbumin/creati-nine, α-1-microglobulin/creatinine ratio and maximal tubular phosphate reabsorption remained unchanged in both groups.

Conclusions

In HIV-infected children, switching PI to efavirenz and stavudine to tenofovir is virologically and immunologically safe, is not associated with renal impairment and provides a significant improvement in lipid profile.

Superiority of Protease Inhibitors over Nonnucleoside Reverse-Transcriptase Inhibitors when Highly Active Antiretroviral Therapy Is Resumed after Treatment Interruption

Forty-five human immunodeficiency virus (HIV)-infected patients stopped taking treatment but resumed taking it thereafter. All 11 who resumed treatment with their prior protease inhibitor (PI)-based regimen reattained an undetectable virus load, whereas this occurred for only 15 (44%) of 34 patients who resumed nonnucleoside reverse-transcriptase inhibitor (NNRTI)-based treatment (P<.001). Distinct pharmacokinetics and resistance barriers may result in different performances for PIs and NNRTIs after treatment interruptions.

HIV-1 intermittent viraemia in patients treated by non-nucleoside reverse transcriptase inhibitor-based regimen

BACKGROUND

It has been demonstrated that, in patients treated by protease-inhibitor-based regimen, intermittent viraemia occurred frequently and was associated with higher concentrations of residual replication but not with virological failure. Risk factors associated with intermittent viraemia and its impact in patients treated by non-nucleoside-reverse-transcriptase-inhibitor-based (NNRTI) regimen need to be evaluated.

METHODS

We analyzed the occurrence of blips (one HIV-1 RNA > 50 copies/ml with a subsequent value < 50 copies/ml), the level of these blips (between 3 and 50 copies/ml) and their effect on CD4 cell count and the occurrence of virological failure in 43 patients with stable suppression of HIV-1 plasma viraemia (< 50 copies/ml) under NNRTI-based therapy.

RESULTS

Eight out of 43 patients had one episode of blips during the follow-up (median = 350 copies/ml). Comparing patients with and without blips, the median level of HIV-1 RNA at baseline was 7.5 versus 3 copies/ml (P = 0.008), respectively. Patients with blips had a significantly lower CD4 cell count after 12 and 18 months than the others. Plasma concentrations of NNRTI before, during, and after the blips were adequate. In addition, the occurrence of blips was not associated with virological failure.

CONCLUSION

These results suggest that blips may reflect ongoing viraemia of below 50 copies/ml and can impair the CD4 cell count recovery under an NNRTI regimen. The impairment of CD4 cell count recovery seems to be affected more by the occurrence of blips than by the level of viraemia (< 50 copies/ml) itself. Nevertheless, despite a tight genetic barrier for resistance with NNRTI drugs, no virologic failure occurred during the follow-up.

The Protease Inhibitor Transfer Study (PROTRA 1): abacavir and efavirenz in combination as a substitute for a protease inhibitor in heavily pretreated HIV-1-infected patients with undetectable plasma viral load

OBJECTIVES

The aim of the study was to evaluate the safety and efficacy of abacavir (ABC) and efavirenz (EFV) instead of a protease inhibitor (PI) in HIV-1-infected subjects treated with two nucleoside reverse transcriptase inhibitors (NRTIs) and one PI with undetectable viral loads (< 50 HIV -1 RNA copies/mL). To be eligible for inclusion, patients had to have a history of viral load < 400 copies/mL for at least 3 months and had to be naive to treatment with nonnucleoside reverse transcriptase inhibitors (NNRTIs) and ABC, but multiple pretreatment and treatment failure were allowed.

DESIGN

An open-label, single-centre pilot study of duration 48 weeks was conducted. ABC was added to the original treatment with two NRTIs and one PI at baseline, and at week 6 the PI was replaced by EFV. At each study visit, CD4 cell count, viral load [measured by polymerase chain reaction (PCR)] and clinical chemistry were measured. Fasting blood samples were taken at baseline and at weeks 12, 24, 36 and 48 to measure levels of cholesterol [high-density lipoprotein (HDL)/low-density lipoprotein (LDL)], triglycerides, insulin and C-peptide. Additionally, an oral glucose tolerance test (OGTT) was performed. A bioelectric impedance analysis (BIA) and a single slice abdominal and mid-thigh computed tomography (CT) scan were carried out to assess changes in body composition.

RESULTS

Thirty patients were included in the study. Three patients experienced ABC-hypersensitivity and one patient demonstrated virological failure caused by nonadherence. At week 48, all remaining patients had viral loads < 50 copies/mL with stable CD4 counts. The fasting metabolic parameters and abdominal fat distribution remained unchanged.

CONCLUSIONS

In heavily pretreated patients, ABC and EFV in combination provide an effective, simplified and well-tolerated alternative to PI treatment.

Low trough plasma concentrations of nevirapine associated with virologic rebounds in HIV-infected patients who switched from protease inhibitors

BACKGROUND

The substitution of a nonnucleoside reverse-transcriptase inhibitor (NNRTI) for protease inhibitors (PIs) has demonstrated its suitability to maintain virologic response. However, the switch from PIs to an NNRTI could fail for a number of reasons, including NNRTI-associated toxicity and emergence of NNRTI-resistant variants.

OBJECTIVE

To describe the virologic failures among 74 HIV-infected patients who switched from PIs to nevirapine.

METHODS

Virologic failure was defined as any rebound of the plasma HIV-RNA (pVL) levels >1000 copies/mL on one occasion or 2 consecutive intermittent viremia episodes defined as increases of the pVL >20 copies/mL but <1000 copies/mL. Virologic failures were investigated retrospectively by determining nevirapine trough concentrations and performing genotypic resistance analysis.

RESULTS

The mean nevirapine concentration was significantly lower in patients with virologic failure in comparison with patients with virologic response (2572 +/- 1642 vs 4550 +/- 2084 ng/mL, respectively; p = 0.003). In multivariate analysis, the mean duration of undetectable pVL before the switch and the mean plasma concentration of nevirapine were significantly associated with virologic success with relative rates of 1.39 (95% CI 1.10 to 1.76, p = 0.006) and 2.7 (95% CI 1.37 to 5.41, p = 0.01), respectively. In patients with pVL >1000 copies/mL, nevirapine mutations and nucleoside reverse-transcriptase inhibitor mutations were found in 80% of the cases.

CONCLUSIONS

The risk of virologic failure after the switch from PI to nevirapine is higher in cases of inadequate nevirapine plasma concentrations. Our data support prospective monitoring of nevirapine plasma concentrations to detect low concentrations prior to the emergence of resistance mutations.

Clinical management of treatment-experienced, HIV-infected patients with the fusion inhibitor enfuvirtide: consensus recommendations

The introduction of enfuvirtide (FUZEON) represents an important advance in the treatment of therapy-experienced patients with HIV-1 infection. However, parenteral self-administration, and the advanced disease and antiretroviral experience of patients currently most needing enfuvirtide introduce unique usage considerations. Enfuvirtide has been shown to provide clinically relevant improvements in CD4 cell counts and reductions in HIV viraemia across all subgroups of treatment-experienced patients studied, including those taking few or no other active drugs. However, optimal outcome results from initiation when the CD4 cell count is above 100 x 10(6) cells/l and viraemia below 1 x 10(5) copies/ml, as part of a newly constructed third or fourth antiretroviral regimen in combination with one or two other antiretrovirals to which the virus remains sensitive. Resistance testing should be used where available to guide background drug selection. Where insufficient options for an effective background exist, enfuvirtide should still be considered and treatment undertaken with the aim of achieving an immunological or clinical response, despite the unlikelihood of a sustained virological outcome. Similarly, where there is no viable alternative treatment, enfuvirtide should be continued following virological failure wherever ongoing immunological or clinical benefit is discerned. Injection site reactions (ISRs) are common on enfuvirtide and will affect almost all patients. ISRs are manageable and seldom activity- or treatment-limiting. Bacterial pneumonia and systemic hypersensitivity reactions have also been reported uncommonly. A structured series of patient visits with a healthcare professional provides an atmosphere of ongoing training and support that may prevent 'injection fatigue', maintain adherence and minimise the incidence of ISRs. An initial investment in establishing such procedures can be expected to yield significant returns in patient confidence and benefit on enfuvirtide.