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PubMed2005

NNRTI hypersusceptibility.

Hypersusceptibility to the nonnucleoside reverse transcriptase inhibitors (NNRTIs) is a recently described observation in which approximately 30% of HIV isolates with resistance to nucleoside reverse transcriptase inhibitors exhibit greater phenotypic susceptibility to the NNRTI class than does wild-type HIV. This increased susceptibility has been associated with better virologic outcomes in several clinical trials and observational cohorts in which NNRTI-based regimens were used. Nucleoside mutations at positions 215, 208, and 118 are associated with efavirenz hypersusceptibility, but to date, there have been no reported biochemical or structural studies on the effect of these mutations on NNRTI binding or on binding pocket conformational changes. There is currently no basis for the practical use of NNRTI hypersusceptibility to guide HIV therapeutic strategies, but it theoretically could affect the evolution of resistance in antiretroviral-naive patients who begin NNRTIs with various nucleoside backbones.

Alkynes↗
PubMed2001

Initiation and continuation of newer antiretroviral treatments among medicaid recipients with AIDS.

OBJECTIVE: To examine initiation of newer antiretroviral treatments across sociodemographic subgroups during the 3 years following the introduction of these treatments, and explore persistence on treatment and its association with patient characteristics. DESIGN: Merged Medicaid paid claims and HIV/AIDS surveillance data were used to analyze use of protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) over time. Survival analysis techniques were used to analyze initiation of PI/NNRTI use. Ordinary least squares and logistic regression were used to determine predictors of persistence on PI/NNRTI therapy. SETTING AND PARTICIPANTS: The study population consisted of 2,459 New Jersey non-HMO adult Medicaid beneficiaries with AIDS, identified through a match between HIV/AIDS Registry and Medicaid files. Their PI/NNRTI use was followed from March 1996, when the first PI was licensed, to the end of 1998. MEASUREMENTS AND MAIN RESULTS: African Americans initiated treatment on average 8 months later than non-Hispanic whites; initiation of treatment was also slower for injection drug users and for those who did not receive case management through a Medicaid waiver program. These bivariate findings were confirmed with a multivariate time-to-treatment analysis using proportional hazards regression. Among those initiating PI/NNRTI use, 35% had discontinued it by the end of follow-up. Bivariate analyses of treated individuals found that PI/NNRTI use as a proportion of follow-up time was lower for African Americans and Hispanics, and higher for older individuals and for those receiving case management through a Medicaid waiver program, while injection drug use history was not associated with persistence. These findings were confirmed by a regression analysis, which found that controlling for other characteristics, African-American race, and Hispanic ethnicity were each associated with a significant 8% reduction in the proportion of time on PI/NNRTIs following initiation of treatment. Alternative approaches for modeling persistence produced similar results. CONCLUSIONS: Results suggest that consistent longitudinal use is difficult for many patients. Persistence of use was lower for minority beneficiaries despite comparable coverage for pharmacy and other health services through Medicaid. Our findings suggest the need to examine nonfinancial barriers to appropriate use of highly active antiretroviral therapy, and to develop and test programmatic strategies for supporting patients in remaining on these regimens consistently.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Simple linear model provides highly accurate genotypic predictions of HIV-1 drug resistance.

Drug resistance is a major obstacle to the successful treatment of HIV-1 infection. Genotypic assays are used widely to provide indirect evidence of drug resistance, but the performance of these assays has been mixed. We used standard stepwise linear regression to construct drug resistance models for seven protease inhibitors and 10 reverse transcriptase inhibitors using data obtained from the Stanford HIV drug resistance database. We evaluated these models by hold-one-out experiments and by tests on an independent dataset. Our linear model outperformed other publicly available genotypic interpretation algorithms, including decision tree, support vector machine and four rules-based algorithms (HIVdb, VGI, ANRS and Rega) under both tests. Interestingly, our model did well despite the absence of any terms for interactions between different residues in protease or reverse transcriptase. The resulting linear models are easy to understand and can potentially assist in choosing combination therapy regimens.

Algorithms↗
PubMed2003

Nucleoside analogues and neuropathy in the era of HAART.

BACKGROUND: Sensory neuropathies occur commonly in the setting of HIV infection. Sensory neuropathy (SN) is clearly associated with HIV itself, and in this context develops in association with increased macrophage activation in the peripheral nervous system. A clinically identical SN may also occur as a consequence of exposure to some HIV treatments. In this setting, impaired mitochondrial function is thought to play a role in the development of neurological dysfunction. OBJECTIVE: This review explores the evidence for the neurotoxicity of HIV and HIV treatments, the effect of nucleoside reverse transcriptase inhibitors on mitochondria, and the likely associations between these. CONCLUSIONS: Dideoxynucleotide drugs are commonly associated with SN. The nucleoside reverse transcriptase inhibitors inhibit mitochondrial DNA synthesis and may thus exacerbate existing viral-induced nerve damage.

Animals↗
PubMed2004

Genotypic determinants of the virological response to tenofovir disoproxil fumarate in nucleoside reverse transcriptase inhibitor-experienced patients.

OBJECTIVE: To assess the genotypic determinants of the virological response to tenofovir disoproxil fumarate (TDF) in a multicentre cohort of antiretroviral (ARV)-experienced patients receiving TDF as a part of a salvage therapy. METHODS: HIV-1 genotype was assessed at baseline in a subgroup of 161 patients of the French expanded access program receiving a stable TDF-including regimen for 3 months or more. Reverse transcriptase mutations associated with the viral load decrease at month 3 with a P-value <0.15 were retained for the construction of a mutation score. The score was then validated using a multivariate analysis and bootstrap resampling method. RESULTS: The strongest association with decrease in viral load was observed with a set of seven mutations (TDF mutation score) that consisted of M41L, E44D, D67N, T69D/N/S, L74V, L210W and T215Y/F RT mutations. The RT K65R mutation and the insertions at codon 69 were not included in the analysis due to low prevalences. A TDF mutation score of < or = 2 predicted the absence of resistance to TDF and > or = 6 mutations predicted resistance to TDF with corresponding reductions in viral load of -1.3 +/- 1.1, and +0.1 +/- 0.7 log10 copies/ml, respectively. In patients with a TDF mutation score of 3-5, the decrease in viral load was -0.8 +/- 1.0 log10 copies/ml and was considered possibly resistant. In the multivariate analysis, a TDF mutation score > or = 6, previous use of amprenavir, indinavir and lopinavir, and co-prescription of didanosine were associated with a worse virological response. The bootstrap analysis showed the robustness of the TDF mutation score. CONCLUSION: In ARV-experienced patients receiving TDF-containing regimens, a score derived from seven reverse transcriptase mutations was shown to be independently predictive of the virological response.

Adenine↗
PubMed2005

Comparison of efavirenz and nevirapine in HIV-infected patients (NEEF Cohort).

The non-nucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz (EFV) and nevirapine (NVP) taken in combination with nucleoside reverse transcriptase inhibitors (NRTIs) have both shown to be just as highly effective as protease inhibitors (PIs) in reducing viral load in patients infected with HIV. Our study compares the performance of these two NNRTIs with each other. This was a non-randomized, prospective, two-arm, multi-centre trial. We evaluated all patients with an EFV- or NVP-containing antiretroviral regimen. The primary endpoint was the difference in success rates defined as a viral load of </=50 copies/mL at week 48. chi(2)-tests were used for naïve and pretreated patients using intention-to-treat (ITT) and on-treatment analysis. As secondary endpoints, a viral load of </=500 copies/mL and CD4 count at week 48 for naïve patients were evaluated. A Cox regression was used to adjust for prespecified covariates. We included 662 patients (NVP 337, EFV 325). The difference in success rates in the ITT analysis was 4.5% ( -11.5%, 19.0%), P=0.578. Pretreated patients with a triple therapy show a difference of 10.1 (-0.3, 20.6), P=0.056. Non-significant results appeared for all secondary analyses. In this trial, no difference between EFV and NVP in combination with NRTI backbone therapy can be shown, regarding viral load. Further randomized studies are necessary to evaluate possible differences.

Alkynes↗
PubMed2006

Effectiveness of dual and triple antiretroviral therapy in the treatment of HIV-infected children.

OBJECTIVE: The use of antiretroviral therapy in HIV-infected children has been a widely discussed issue. The aim of this study was to compare the effectiveness of dual nucleoside analogue reverse transcriptase inhibitor (NRTI) regimens and three-drug regimens [2NRTI+ non-nucleoside reverse transcriptase inhibitor (NNRTI) or protease inhibitor (PI)] in a cohort of HIV-infected children. METHODS: The study was carried out in a referral center for the management of infected children, which is affiliated with the School of Medicine of Universidade Federal de Minas Gerais (UFMG). Those children whose antiretroviral therapy was implemented between January 1998 and December 2000 and who were followed until December 2001 were included in the study. Therapeutic failure or death was regarded as the endpoint in our analysis. RESULTS: A total of 101 patients were assessed, 58 (57.4%) on dual therapy and 43 (42.6%) on triple therapy. No statistically significant difference was observed between the groups in terms of gender, age, CD4+ count and baseline viral load. The average duration of dual therapy was 26.3 months (95%CI 21.3-31.3) and that of triple therapy was 34.3 months (95%CI 29.2-39.5%). There was therapeutic failure in 33 (56.9%) patients on dual therapy and in 11 (25.6%) patients on triple therapy (log rank = 5.03; p = 0.025). The relative risk of therapeutic failure of the dual therapy was 2.2 times higher (95%CI 1.3-3.9). The percentage of initial CD4+ T cells was a predictor of risk for therapeutic failure (p = 0.001). Patients on triple therapy showed a more remarkable reduction in their viral load (p = 0.001). CONCLUSION: Triple therapy was efficient for a longer time period and showed better virologic response than dual therapy in this cohort of HIV-infected children. Therefore, triple therapy should be the treatment of choice.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Resistance and cross-resistance to abacavir.

BACKGROUND: Abacavir (ABC) is a potent nucleoside reverse transcriptase inhibitor (NRTI) used in multi-drug antiretroviral regimens and in combination with other NRTIs, protease and/or non-nucleoside reverse transcriptase inhibitors (NNRTIs) in both treatment naive and treatment experienced patients. PATTERNS OF RESISTANCE: Resistance to ABC has been demonstrated in vitro and in vivo. Patterns of emerging mutations may vary when ABC is combined with other NRTIs relative to the mutations observed in monotherapy. Additionally, thymidine NRTIs may select for mutations that, while not selected for by ABC, may confer diminished susceptibility and diminished clinical response to ABC. CLINICAL USE OF ABC: Resistance and clinical data indicate that ABC may be a suitable component of initial regimens and second or subsequent lines of therapy. It may be used as a substitution agent for persons wishing to discontinue protease inhibitor therapy who have not previously experienced viral rebound on NRTI therapy.

Anti-HIV Agents↗
PubMed1999

Treatment of human immunodeficiency virus 1-infected infants and children with the protease inhibitor nelfinavir mesylate.

An open-label study was conducted of nelfinavir mesylate, given with reverse transcriptase inhibitors to human immunodeficiency virus 1 (HIV-1)-infected infants and children 3 months to 13 years of age. Doses of nelfinavir mesylate of 20-30 mg/kg yielded drug exposures comparable to those seen in adults. The drug was well tolerated; mild diarrhea was the primary toxic effect observed. Seventy-one percent (39) of the 55 evaluable subjects had an initial decrease in plasma HIV-1 RNA, of at least 0.7 log10 copies/mL; suppression of plasma HIV-1 RNA levels to < 400 copies/mL was observed in 15. Children who began taking at least one new reverse transcriptase inhibitor near the time when nelfinavir mesylate was started, and those with a > or = 24% proportion of CD4 lymphocytes, had a greater chance of achieving and maintaining a decline in plasma HIV-1 RNA to < 400 copies/mL. Suppression of viremia was achieved in children as young as 3 months of age.

Adolescent↗
PubMed2001

Antiretroviral resistance mutations among pregnant human immunodeficiency virus type 1-infected women and their newborns in the United States: vertical transmission and clades.

To assess the impact of antiretroviral resistance on perinatal transmission prevention efforts, human immunodeficiency virus type 1 (HIV-1) genotypic resistance testing was done for 220 HIV-1-infected, zidovudine (AZT)-exposed pregnant women and 24 of their infected infants. The women were prospectively enrolled in 4 US cities in 1991-1997. Phylogenetic and sequencing analyses revealed 5 women with non-clade B infections traced to western African origins. AZT-associated mutations were detected in 17.3% of pregnant women, whereas genotypic resistance to nonnucleoside reverse-transcriptase inhibitors and protease inhibitors was infrequent. No significant association was detected between perinatal transmission and the presence of either AZT or nucleoside reverse-transcriptase inhibitor resistance-associated mutations. AZT resistance mutations were detected in 2 (8.3%) neonatal samples, but the mutation pattern was not identical to the mother's. Although no effect of viral resistance on mother-infant transmission was demonstrated, the advent of more-potent drug classes and the potential for the rapid emergence of resistance warrant prospective surveillance.

Anti-HIV Agents↗
PubMed1997

Recent advances in antiretroviral therapy and HIV infection monitoring.

Potent new antiretroviral drugs combined with updated treatment strategies have now achieved efficient inhibition of HIV replication in most patients. The major targets for antiretroviral therapy are the reverse transcriptase and the protease of HIV. Up to date, 11 antiretroviral drugs have been licensed in the US. New nucleoside reverse transcriptase inhibitors (NRTI), i.e. abacavir, and adefovir dipivoxil proved to be effective in clinical trials. The antiretroviral activity and impact on clinical outcome of nonnucleoside reverse transcriptase inhibitors (NNRTI) are mostly short lived. Compared to NRTIs, protease inhibitors (PIs) have the highest antiretroviral activity. New PIs that conserve activity against mutant HIV strains or derivatives that have a simpler biosynthesis are being developed. A major drawback of highly active antiretroviral therapy is the selection of resistant mutants under suboptimal dosage, in advanced stages of disease or after pre-treatment with mono- or double-combination regimens. Monitoring of antiretroviral therapy is achieved by measurement of viral load using nucleic acid amplification techniques. The goal of antiretroviral therapy should be to reduce viral load below the detection limit of current assays in order to delay the emergence of resistant mutants and to maximally reduce disease progression. Recommendations for antiretroviral therapy and monitoring are evolving constantly due to the rapid progress in the development of active compounds and new insights into HIV pathogenesis. Resistance determination of HIV patient isolates seems to play a progressively increasing role in monitoring of antiretroviral treatment since treatment-naive patients may already harbour drug-resistant virus. Due to cross-resistance between different compounds, the choice of the treatment regimen should be guided by resistance patterns of HIV in order to warrant maximal and long-lasting efficiency.

Dideoxynucleosides↗
PubMed2005

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.

Adult↗
PubMed2003

Low rate of genotypic HIV-1 drug-resistant strains in the Senegalese government initiative of access to antiretroviral therapy.

OBJECTIVE: To monitor the prevalence of antiretroviral (ARV)-resistant HIV-1 viruses, and the genotypic mutations in patients enrolled in the Senegalese initiative for access to antiretroviral treatment (ART). METHODS: A total of 80 patients with a virological follow-up of at least 6 months were selected, 68 were ART-naive and 12 ART-experienced. Genotypic resistance to ARV was studied at baseline for a random subset of patients and at each rebound in plasma viral load during ART, by sequencing the protease and reverse transcriptase genes. RESULTS: At baseline, 66 patients received highly active antiretroviral therapy (HAART) [2 nucleoside reverse transcriptase inhibitors (NRTIs) +1 protease inhibitor (PI) (n = 64) or 2 NRTIs + 1 non-nucleoside reverse transcriptase inhibitor (NNRTI) (n = 2)] and 14 patients (17.5%) started with a dual therapy because of ongoing antitubercular therapy or efficient previous bitherapy for the ART-experienced patients. The emergence of drug-resistant viruses (n = 13) during follow-up was more frequent in ART-experienced patients than in ART-naive patients, 41.7 versus 11.8%, resistant viruses emerged at comparable follow-up periods, a median of 17.8 and 18.3 months, respectively. In patients receiving zidovudine and lamivudine in their drug regimen, resistance to lamivudine was more frequent than to zidovudine. Two of the three patients, with viruses resistant to PIs, acquired mutations associated with cross-resistance. Strikingly, five (39%) of the 13 patients developed resistances to drugs that they had never received (n = 3) or that they received 18 or 36 months ago (n = 2). Didanosine/stavudine pressure had selected zidovudine-resistant viruses in four patients, and indinavir had selected a nelfinavir-resistant virus in one patient. CONCLUSION: In contrast to other reports from developing countries where patients had received ARVs in an uncontrolled manner, our study showed that implementation of HAART together with good clinical, biological and logistical monitoring can reduce the emergence of resistant strains in Africa.

Adult↗
PubMed2006

Development of a new methodology for screening of human immunodeficiency virus type 1 microbicides based on real-time PCR quantification.

Potential topical retrovirucides or vaginal microbicides against human immunodeficiency virus type 1 (HIV-1) include nonnucleoside reverse transcriptase inhibitors (NNRTIs). To be successful, such agents have to be highly active against cell-free virions. In the present study, we developed a new real-time PCR-based assay to measure the natural endogenous reverse transcription (NERT) activity directly on intact HIV-1 particles in the presence of reverse transcriptase (RT) inhibitors. We further evaluated the permeability to nevirapine (NVP) and efavirenz (EFV) and their retention within nascent viral particles. We also demonstrated the NVP and EFV inhibitory effects on NERT activity and the impact of resistance mutations measured directly by this new strategy. Furthermore, the results showed a clear correlation between NERT activity and classical infectivity assays. The 50% inhibitory concentrations (IC50s) of NVP and EFV were demonstrated to be up to 100-fold higher for cell-free than for cell-associated virions, suggesting that cell-free virions are less permeable to these drugs. Our results suggest that NVP and EFV penetrate both the envelope and the capsid of HIV-1 particles and readily inactivate cell-free virions. However, the characteristics of these NNRTIs, such as lower permeability and lower retention during washing procedures, in cell-free virions reduce their efficacies as microbicides. Here, we demonstrate the usefulness of the NERT real-time PCR as an assay for screening novel antiretroviral compounds with unique mechanisms of action.

Alkynes↗
PubMed2000

Anti-HIV drug update.

There continues to be progress in the development of a number of new anti-HIV drugs. Additional research has focused on optimizing the use of protease inhibitors and non-nucleoside reverse transcriptase inhibitors (NNRTIs). This has resulted in studies of dual protease inhibitor combinations, protease inhibitor and NNRTI combinations and now dual NNRTI combinations.

CD4 Lymphocyte Count↗
PubMed2004

Salvage therapy with amprenavir, lopinavir and ritonavir 200 mg/d or 400 mg/d in HIV-infected patients in virological failure.

OBJECTIVES: To compare the antiviral efficacy of a salvage therapy combining lopinavir and amprenavir with 200 mg/d or 400 mg/d ritonavir, together with nucleoside reverse transcriptase inhibitors, over a 26-week period in HIV-infected patients in whom multiple antiretroviral regimens had failed. DESIGN: Phase IIb, randomized, open-label, multicentre trial. Patients were eligible if they had <500 CD4+ cells/mm3 and >4 log10 copies/ml HIV-RNA after treatment with at least two protease inhibitors (PIs) and one non-nucleoside reverse transcriptase inhibitor. RESULTS: At baseline (n=37), the median CD4+ cell count was 207/mm3 and the median plasma HIV-1 RNA level was 4.7 log10 copies/ml; the median number of PI mutations was seven and the median decrease in phenotypic susceptibility to lopinavir and amprenavir was 9.7 and 2.6, respectively. The mean number of antiretrovirals received prior to randomization was 7.7. The fall in the median HIV-1 RNA level at week 26 was -1.4 log10 copies/ml in the 200 mg/d ritonavir group and -2.5 log10 copies/ml in the 400 mg/d group (P=0.02). Viral load fell below 50 copies/ml in 32% and 61% of patients, respectively (P=0.07). After adjustment for the ritonavir dose, a smaller number of PI mutations was the only baseline characteristic associated with a better virological response at week 26. Amprenavir concentrations were significantly lower in presence of lopinavir. The lopinavir inhibitory quotient at week 6 correlated weakly with the change in the HIV-RNA level at week 26. CONCLUSION: Combination of amprenavir, lopinavir and 400 mg/d ritonavir shows significant virological efficacy without increased toxicity in HIV-infected patients in whom multiple antiretroviral regimens have failed.

Adult↗
PubMed2007

Cervical shedding of HIV-1 RNA among women with low levels of viremia while receiving highly active antiretroviral therapy.

BACKGROUND: Among women with low or undetectable quantities of HIV-1 RNA in plasma, factors associated with genital HIV-1 RNA shedding, including choice of treatment regimen, are poorly characterized. METHODS: We measured HIV-1 RNA in cervical swab specimens obtained from participants in the Women's Interagency HIV Study who had concurrent plasma viral RNA levels <500 copies/mL, and we assessed factors associated with genital HIV shedding. The study was powered to determine the relative effects of antiretroviral protease inhibitors (PIs) versus nonnucleoside reverse transcriptase inhibitors (NNRTIs) on viral RNA shedding. RESULTS: Overall, 44 (15%) of 290 women had detectable HIV-1 RNA in cervical specimens. In the final multivariate model, shedding was independently associated with NNRTI (vs. PI) use (odds ratio [OR], 95% confidence interval [CI]: 2.24, 1.13 to 4.45) and illicit drug use (OR, 95% CI: 2.41, 0.96 to 5.69). CONCLUSIONS: This is the largest study to define risks for genital HIV-1 RNA shedding in women with low/undetectable plasma virus. Shedding in this population was common, and NNRTI-based highly active antiretroviral therapy (HAART) (vs. PI-based HAART) was associated with genital HIV shedding. Further study is required to determine the impact of these findings on transmission of HIV from mother to child or to sexual partners.

Adult↗