Efficacy and Safety of Abacavir Plus Lamivudine Versus Didanosine Plus Stavudine When Combined with a Protease Inhibitor, a Nonnucleoside Reverse Transcriptase Inhibitor, or Both in HIV-1 Positive Antiretroviral-Naive Persons

Efficient monitoring of HIV-1 vertically infected children in Kenya on first-line antiretroviral therapy

BACKGROUND

Worldwide access to antiretroviral therapy (ART) in low- and middle-income countries has significantly increased. Although this presents better treatment options for HIV-infected individuals, the challenge of monitoring ART in these settings still remains.

OBJECTIVE

To investigate efficient and cost-effective criteria for assessing ART failure among HIV-1-infected children on first-line ART in resource-limited settings.

STUDY DESIGN

Retrospective analysis of 75 HIV-1 vertically infected Kenyan children with a follow-up period of 24 months after initiating ART. Plasma viral load, peripheral CD4(+)T-cell counts and HIV-1 drug-resistance mutations were monitored biannually.

RESULTS

Plasma viral load (VL) was suppressed to undetectable level or more than 1.5 log(10) from baseline levels in 53 (70.7%) children within 24 months. VL in the remaining 22 (29.3%) children was not suppressed significantly. Of the 22 children, 21 were infected with HIV-1 strains that developed drug-resistance mutations; 9 within 12 months and 12 between 12 and 24 months. Among the 53 who were successfully treated, VL was suppressed in 33 within 12 months and in 20 between 12 and 24 months. There was no significant difference in VL at baseline and the change of CD4(+)T-cell counts after initiating ART between those treated successfully and the failure groups.

CONCLUSION

After initiating ART, children may require longer times to achieve complete viral suppression. Plasma viral load testing 24 months after initiating ART could be used to differentiate ART failures among HIV-1 vertically infected children in resource-limited settings. Additionally, drug resistance testing, if affordable, would be helpful in identifying those failing therapy and in choosing second-line regimens.

Abacavir and lamivudine for the treatment of human immunodeficiency virus

INTRODUCTION

The introduction of combination antiretroviral therapy (cART) in 1996 dramatically changed the survival and the quality of life of people living with human immunodeficiency virus (HIV). Viral replication can be controlled by using a combination of more than 30 licensed drugs. Despite the fact that many advances have been made in the last 20 years of experience with antiretrovirals, certain needs remain to be addressed, such as the presence of chronic inflammation, the long-term side effects of newly introduced drugs and eradication. Abacavir (ABC) and lamivudine (3TC) are licensed in a fixed-dose combination to be administered once daily with other antiretroviral agents for the treatment of HIV.

AREAS COVERED

This article provides an extensive review of the evidence on the combination of ABC 600 mg and 3TC 300 mg. Specifically, it discusses the chemistry-- including the phrarmacodynamics, resistance to treatment, pharmacokinetics and metabolism--and formulations available. It also looks at clinical efficacy, including safety and tolerability.

EXPERT OPINION

In the last few years, new data regarding human leukocyte antigen (HLA) B*5701 testing to prevent the hypersensitivity reaction due to ABC have been presented, providing a landmark in the management of adverse events in HIV, and later a previously unexpected correlation of the recent exposure to ABC with an increased risk of cardiovascular disease. This review presents the current situation with regard to the long-term efficacy and safety data on the ABC/3TC combination.

Abacavir/lamivudine combination in the treatment of HIV: a review

Abacavir has been at the center of research and clinical interest in the last two years. The frequency of the associated abacavir hypersensitivity syndrome has decreased substantially since the introduction of routine testing for the HLA-B*5701 allele; the activity of the drug in HIV-infected persons with HIV RNA values more than 100,000 copies/mL has been questioned; the possible increased risk of myocardial infarction after recent exposure to abacavir has been debated; and the drug has been moved from the “recommended” category to the “alternative” category in several guidelines. Still, the drug remains a useful agent in combination with other drugs, including lamivudine, for the treatment of HIV infection. This review will focus on the pharmacokinetics, activity, side effects, and resistance profile of both abacavir and lamivudine, including a thorough review of all of the recent studies relevant to both drugs.

Successful implementation of a national HLA-B*5701 genetic testing service in Canada

Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) that is used in combination antiretroviral therapy in HIV-infected patients. It is currently recommended as a preferred or an alternative NRTI in antiretroviral-naïve patients. The major toxicity of abacavir is a hypersensitivity reaction (HSR), which occurs in approximately 5% of treated patients. There is a strong association between the human leukocyte antigen (HLA)-B*5701 allele and abacavir HSR, which has allowed for rapid acceptance of genetic screening for HLA-B*5701 in clinical use. Canadian clinicians working in hospital centers with HLA typing capacity opted to launch a pilot project in 2006 to offer the screening test as standard of care to HIV-infected patients. Currently, more than 11,000 HLA-B*5701 tests have been performed, among which 6.3% are positive. Continued efforts have been made to ensure that testing is available to all HIV-infected patients to widen the patients' therapeutic options. HLA-B*5701 screening shows clinical use and preliminary data suggest cost-effectiveness.

Virologic, immunologic, clinical, safety, and resistance outcomes from a long-term comparison of efavirenz-based versus nevirapine-based antiretroviral regimens as initial therapy in HIV-1-infected persons

PURPOSE

To compare long-term virologic, immunologic, and clinical outcomes in antiretroviral-naïve persons starting efavirenz (EFV)- versus nevirapine (NVP)-based regimens.

METHOD

The FIRST study randomized patients into three strategy arms: PI+NRTI, NNRTI+NRTI, and PI+NNRTI+NRTI. NNRTI was determined by optional randomization (NVP or EFV) or by choice. For this randomized substudy, the primary endpoint was HIV RNA >50 copies/mL after 8 months or death. Genotypic resistance testing was done at virologic failure (VF; HIV RNA >1,000 copies/mL at or after 4 months).

RESULTS

228 persons (111 randomized to EFV, 117 to NVP) were followed for median 5 years. Rates per 100 person years for the primary endpoint were 41.2 (EFV) and 42.8 (NVP; p = .59). The percent of persons with HIV RNA <50 copies/mL was similar throughout follow-up (p = .24), as were average increases in CD4+ cells (p = .30). 423 persons declining the substudy chose EFV; 264 chose NVP. There were 915 persons in the combined cohort (randomized and choice). In the combined cohort, the risk of VF and VF with any NNRTI or NRTI resistance or resistance of any class was significantly less for EFV compared to NVP.

CONCLUSIONS

EFV-based regimens as initial therapy resulted in a lower risk of VF and VF with resistance than did NVP-based regimens, although immunologic and clinical outcomes were similar.

A comparison of three highly active antiretroviral treatment strategies consisting of non-nucleoside reverse transcriptase inhibitors, protease inhibitors, or both in the presence of nucleoside reverse transcriptase inhibitors as initial therapy (CPCRA 058 FIRST Study): a long-term randomised trial

BACKGROUND

Long-term data from randomised trials on the consequences of treatment with a protease inhibitor (PI), non-nucleoside reverse transcriptase inhibitor (NNRTI), or both are lacking. Here, we report results from the FIRST trial, which compared initial treatment strategies for clinical, immunological, and virological outcomes.

METHODS

Between 1999 and 2002, 1397 antiretroviral-treatment-naive patients, presenting at 18 clinical trial units with 80 research sites in the USA, were randomly assigned in a ratio of 1:1:1 to a protease inhibitor (PI) strategy (PI plus nucleoside reverse transcriptase inhibitor [NRTI]; n=470), a non-nucleoside reverse transcriptase inhibitor (NNRTI) strategy (NNRTI plus NRTI; n=463), or a three-class strategy (PI plus NNRTI plus NRTI; n=464). Primary endpoints were a composite of an AIDS-defining event, death, or CD4 cell count decline to less than 200 cells per mm3 for the PI versus NNRTI comparison, and average change in CD4 cell count at or after 32 months for the three-class versus combined two-class comparison. Analyses were by intention-to-treat. This study is registered ClinicalTrials.gov, number NCT00000922.

FINDINGS

1397 patients were assessed for the composite endpoint. A total of 388 participants developed the composite endpoint, 302 developed AIDS or died, and 188 died. NNRTI versus PI hazard ratios (HRs) for the composite endpoint, for AIDS or death, for death, and for virological failure were 1.02 (95% CI 0.79-1.31), 1.07 (0.80-1.41), 0.95 (0.66-1.37), and 0.66 (0.56-0.78), respectively. 1196 patients were assessed for the three-class versus combined two-class primary endpoint. Mean change in CD4 cell count at or after 32 months was +234 cells per mm3 and +227 cells per mm3 for the three-class and the combined two-class strategies (p=0.62), respectively. HRs (three-class vs combined two-class) for AIDS or death and virological failure were 1.15 (0.91-1.45) and 0.87 (0.75-1.00), respectively. HRs (three-class vs combined two-class) for AIDS or death were similar for participants with baseline CD4 cell counts of 200 cells per mm3 or less and of more than 200 cells per mm3 (p=0.38 for interaction), and for participants with baseline HIV RNA concentrations less than 100 000 copies per mL and 100,000 copies per mL or more (p=0.26 for interaction). Participants assigned the three-class strategy were significantly more likely to discontinue treatment because of toxic effects than were those assigned to the two-class strategies (HR 1.58; p<0.0001).

INTERPRETATION

Initial treatment with either an NNRTI-based regimen or a PI-based regimen, but not both together, is a good strategy for long-term antiretroviral management in treatment-naive patients with HIV.

Prevalence and Impact of HIV-1 Protease Codon 33 Mutations and Polymorphisms in Treatment-Naive and Treatment-Experienced Patients

Background

HIV-1 protease gene mutations at codon 33 have been associated with resistance to some but not all protease inhibitors (PIs). Little is known about the difference in prevalence of codon 33 mutations and polymorphisms between treatment-naive and treatment-experienced patients, and the effect of codon 33F on PI phenotypic resistance patterns.

Methods

Baseline genotypes (TRUGENE) from 772 patients participating in two different randomized clinical trials [504 antiretroviral treatment-naive patients and 268 antiretroviral treatment-experienced patients] were evaluated for the presence of protease codon 33 mutations and polymorphisms. Baseline phenotypes (Antivirogram), including fold-change in resistance for 16 antiretroviral drugs, were available for the 268 treatment-experienced patients. Multivariate linear regression models were used to determine factors associated with phenotypic fold-change for PIs.

Results

The prevalence of codon 33 mutations and polymorphisms was 5.2% in the naive cohort (0.2% 33F, 2.5% 33V, 2.5% 33I) and 34.7% in the experienced cohort (30.2% 33F, 1.5% 33V, 3.0% 33I). In the antiretroviral-experienced cohort (mean = 4.2 prior PIs, 10.6 prior antiretroviral drugs overall), a model adjusting for the presence of specific major protease and multi-PI resistance conferring mutations, the number of other minor PI mutations, prior PI drug exposure (current, prior only, never), and HIV transmission risk factor was used to estimate the phenotypic fold-change in resistance for those with and without mutation 33F. Those with 33F had a significantly higher fold-change for amprenavir (33 vs 19, P<0.0001), ritonavir (162 vs 82, P<0.0001), lopinavir (49 vs 38, P=0.04), and saquinavir (47 vs 41, P=0.02). The presence of the 33F was not a significant predictor of fold change in susceptibility for indinavir or nelfinavir.

Conclusions

At protease codon 33, the prevalences of polymorphisms 33V and 33I were similar for PI-naive and PI-experienced patients (<3.0%), but the prevalence of 33F was significantly different (0.2% versus 30.2%). In the treatment-experienced cohort, the differences in phenotypic fold-change for amprenavir, lopinavir, saquinavir, and ritonavir between those with and without 33F persist after adjustment for the presence of other major PI mutations and PI drug exposure history. Given the availability of newer PIs that may select for 33F, monitoring for the presence of this mutation should be ongoing for both treatment-naive and treatment-experienced patients.