Emergence of dual resistance to zidovudine and lamivudine in HIV-1-infected patients treated with zidovudine plus lamivudine as initial therapy

Presence of mutations associated with resistance to zidovudine or lamivudine was determined in isolates of HIV-1 obtained after long-term follow-up of 64 infected individuals who received zidovudine, lamivudine, or both drugs as initial antiretroviral therapy. Zidovudine resistance mutations were less frequent in isolates from patients treated with combination lamivudine plus zidovudine compared with zidovudine alone, but these mutations accumulated over time. Phenotypic resistance to both drugs was found in isolates from 3 of 23 patients. In 3 other patients, lamivudine-resistant virus detected at week 12 was replaced by wild-type virus after longer follow-up, which correlated with a return to baseline levels of plasma HIV-1 RNA. These results show that dual resistance to zidovudine and lamivudine develops over time despite the delayed emergence of zidovudine-resistant mutations. These results also suggest a selective advantage in vivo for HIV-1 species that are wild-type at RT codon 184.     

Tenofovir disoproxil fumarate, emtricitabine, and efavirenz versus fixed-dose zidovudine/lamivudine and efavirenz in antiretroviral-naive patients: virologic, immunologic, and morphologic changes--a 96-week analysis

BACKGROUND: In antiretroviral-naive patients, tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) demonstrated superior outcomes compared with fixed-dose zidovudine (ZDV)/lamivudine (3TC) and EFV through 48 weeks. Results through a 96-week extension phase are presented. METHODS: In this randomized, open-label, noninferiority trial, 517 antiretroviral-naive HIV-infected patients received TDF, FTC, and EFV (TDF + FTC + EFV) or ZDV/3TC and EFV (ZDV/3TC + EFV). The primary endpoint was the proportion of patients with an HIV RNA level <400 copies/mL in patients without baseline nonnucleoside resistance. RESULTS: Through week 96, significantly more patients receiving TDF + FTC + EFV achieved and maintained an HIV RNA level <400 copies/mL (75% receiving TDF + FTC + EFV vs. 62% receiving ZDV/3TC + EFV; P = 0.004). There was a trend toward greater virologic suppression to <50 copies/mL in the TDF + FTC + EFV group (67% vs. 61%; P = 0.16). The TDF + FTC + EFV group demonstrated a significantly greater increase in CD4 count (270 vs. 237 cells/mm; P = 0.036). No patient developed the K65R mutation. Limb fat at week 96 was significantly greater in the TDF + FTC + EFV group versus the ZDV/3TC + EFV group (7.7 vs. 5.5 kg; P < 0.001). CONCLUSION: Over 96 weeks, the combination of TDF, FTC, and EFV was superior to fixed-dose ZDV/3TC + EFV for achieving and maintaining an HIV RNA level <400 copies/mL and an increase in CD4 cells.     

Effect of zidovudine resistance mutations on virologic response to treatment with zidovudine or stavudine,each in combination with lamivudine and indinavir

The authors studied the effect of zidovudine (ZDV) resistance mutation on virologic response to treatment with ZDV or stavudine (d4T) each in combination with lamivudine and indinavir. Viral genotyping was performed on plasma HIV-1 RNA at study entry and concerned 155 patients previously treated with ZDV, didanosine, or zalcitabine and enrolled in the NOVAVIR (Agence National de Recherche sur le SIDA [ANRS] 073) trial. Three virologic responses were investigated: early response (<50 copies/mL at week 24), late response (<500 copies/mL at week 80), and virologic failure (two HIV-1 RNA >5000 copies/mL). Patients were classified as resistant or susceptible to ZDV according to the ANRS algorithm. Plasma viral RNA from 123 of 155 patients had two or more ZDV resistance mutations. The number of ZDV resistance mutations was positively correlated with the duration of prior antiviral therapy (p <.001). At week 24, 74% and 77% of patients with virus classified as resistant were responders in the d4T and ZDV arm, respectively. Similar results were found at week 80. Virologic failure was reached in 7 of 24 patients with virus classified as susceptible and in 26 of 131 patients with resistant virus (p =.29). In the ZDV arm, patients classified as resistant had longer times to virologic failure than those classified as susceptible (p =.003). In conclusion, sustained virologic response despite presence of ZDV resistance mutations implies that these mutations do not preclude an early and durable response to treatment with a potent three-drug regimen in these patients. Patients susceptible to ZDV had lower median mean corpuscular volumes and lower random indinavir levels, suggesting that adherence was the main reason for failure.     

Tenofovir disoproxil fumarate, emtricitabine, and efavirenz compared with zidovudine/lamivudine and efavirenz in treatment-naive patients: 144-week analysis

BACKGROUND: As antiretroviral regimens for the treatment of HIV infection improve, trials providing data on long-term follow-up are increasingly important. METHODS: A regimen of tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) demonstrated superior virologic, immunologic and morphologic effects compared with a regimen of fixed-dose zidovudine/lamivudine (ZDV/3TC) and EFV through 96 weeks in a randomized open-label trial. After 96 weeks, patients on TDF + FTC transitioned to fixed-dose combination TDF/FTC. RESULTS: Through 144 weeks, significantly more patients in the TDF/FTC arm reached and maintained an HIV RNA level <400 copies/mL (71% receiving TDF/FTC and EFV vs. 58% receiving ZDV/3TC and EFV; P = 0.004), with a trend toward greater CD4 cell increase in the TDF/FTC arm (312 vs. 271 cells/mm; P = 0.09). Over 144 weeks of follow-up, more patients in the ZDV/3TC arm discontinued therapy because of adverse events (11% vs. 5%; P = 0.01) and no patients discontinued because of renal events. Patients in the ZDV/3TC arm had significantly less limb fat than patients in the TDF/FTC arm (5.4 vs. 7.9 kg; P < 0.001) at 144 weeks. CONCLUSIONS: Cumulative results from 3 years of follow-up suggest that a regimen of TDF/FTC and EFV demonstrates superior durability of viral load suppression and an improved safety and morphologic profile compared with ZDV/3TC and EFV.     

Dose-finding study of once-daily indinavir/ritonavir plus zidovudine and lamivudine in HIV-infected patients

BACKGROUND: Strategies for treatment of HIV need to be considered in terms of combining potency, safety, and convenience of dosage. However, regimens including once-daily protease inhibitors are not yet available. We have performed a pilot study to determine an indinavir/ritonavir (IND/RTV) regimen for once-daily dosing, by monitoring plasma levels. METHODS: Antiretroviral-naive HIV-infected adults were eligible. Therapy was zidovudine/lamivudine 1 pill twice daily plus IND/RIT (liquid formulation) 800/100 mg twice daily with food. At 4-week intervals, plasma levels were measured and dosage of IND/RIT switched to 1000/100 mg daily and then 800/200 mg daily. If 12-hour minimum concentrations (Cmin12h) of IND were too low (<0.1 microg/ml) with IND/RIT 1000/100 mg once daily in the first half of the patients, it was planned to switch directly to 800/200 mg once daily in the other half. RESULTS: In all, 27 patients were recruited. Mean baseline CD4+ lymphocyte count was 107 x 106/L (range, 4-623 x 106/L). Eleven patients (40%) discontinued the study medication within the first 4 weeks due to clinical progression (n = 3) or grade 1-2 RTV related side effects (n = 8). Nine patients (group A) switched from 800/100 mg twice daily to 1000/100 mg once daily and then to 800/200 mg once daily. Seven patients (group B) switched directly to 800/200 mg once daily. At week 32, viral load was <5 copies/ml in 15 of 16 patients (94%). RTV levels were always <2.1 microg/ml. The mean and 95% confidence interval for IND Cmin and Cmax in microg/ml was: using IND/RTV 800/100 mg twice daily (n = 16) 1.4 (0.5-2.3) and 6.7 (4.4-9.1), respectively; using IND/RTV 1000/100 mg once daily (n = 9) 0.18 (0-0.41) and 8.6 (3.3-14), respectively; and using 800/200 mg once daily (n = 16) 0.38 (0-0.9), and 7.5 (0.8-14.8). For all 16 patients who received IND/RTV 800/100 mg twice daily, the Cmin value for IND was >/=0.1 microg/ml. Conversely, IND Cmin was <0.1 microg/ml in 4 of 9 receiving 1000/100 mg once daily but in only 1 of 16 receiving 800/200 mg once daily. CONCLUSION: Once-daily regimen of IND/RIT is feasible and deserves further evaluation in larger randomized trials. Liquid formulation of RIT was not well tolerated by our antiretroviral-naive patients despite lower than suggested doses.     

Induction with abacavir/lamivudine/zidovudine plus efavirenz for 48 weeks followed by 48-week maintenance with abacavir/lamivudine/zidovudine alone in antiretroviral-naive HIV-1-infected patients

BACKGROUND: The ESS40013 study tested 4-drug induction followed by 3-drug maintenance as initial antiretroviral therapy (ART) to reduce HIV RNA rapidly and then to simplify to an effective yet more convenient and tolerable regimen. METHODS: Four hundred forty-eight antiretroviral-naive adults were treated with abacavir/lamivudine/zidovudine (ABC/3TC/ZDV) and efavirenz (EFV) for the 48-week induction phase. Two hundred eighty-two patients were randomized in a 1:1 ratio to continue ABC/3TC/ZDV+EFV or to simplify to ABC/3TC/ZDV for the 48-week maintenance phase. RESULTS: The baseline median HIV RNA level and CD4 cell count were 5.08 log10 copies/mL (56%>or=100,000 copies/mL) and 210 cells/mm (48% <200 cells/mm), respectively. No significant differences were noted between ABC/3TC/ZDV+EFV and ABC/3TC/ZDV for an HIV RNA level <50 copies/mL (79% vs. 77% [intent to treat (ITT), missing=failure]; P=0.697) or time to treatment failure (P=0.75) at week 96. Drug-related adverse events were more commonly reported for ABC/3TC/ZDV+EFV than for ABC/3TC/ZDV (15% vs. 6%). Improvements in total cholesterol, low-density lipoprotein cholesterol, and triglycerides were observed in the ABC/3TC/ZDV group. Virologic failure occurred in 22 patients during induction and in 24 patients (16 in ABC/3TC/ZDV group and 8 in ABC/3TC/ZDV+EFV group; P=0.134) during maintenance. A greater proportion of patients receiving ABC/3TC/ZDV than ABC/3TC/ZDV+EFV reported perfect adherence at week 96 (88.8% vs. 79.6%; P=0.057). CONCLUSIONS: After induction with ABC/3TC/ZDV+EFV, simplification to ABC/3TC/ZDV alone maintained virologic control and immunologic response, reduced fasting lipids and ART-associated adverse events, and improved adherence.     

Prevalence and risk factors for developing K65R mutations among HIV-1 infected patients who fail an initial regimen of fixed-dose combination of stavudine, lamivudine, and nevirapine.

BACKGROUND: A fixed-dose combination of stavudine, lamivudine, and nevirapine (d4T/3TC/NVP) is extensively used as initial antiretroviral regimen in developing countries. K65R mutations that occur after failing this regimen prevent the use of tenofovir, didanosine, and abcavir in the second-line regimen. OBJECTIVES: To determine the prevalence and risk factors of K65R mutations after failing d4T/3TC/NVP. STUDY DESIGN: Genotypic resistance testing was conducted among HIV-1 infected patients who experienced virological failure with an initial regimen of d4T/3TC/NVP. RESULTS: There were 122 patients who received antiretroviral therapy (ART) for a median (IQR) duration of 19 (13-27) months. Median (IQR) CD4 cell count and plasma HIV-1 RNA at virological failure was 174 (109-264) cells/mm(3) and 4.0 (3.7-4.6)log copies/mL, respectively. The prevalence of K65R mutations was 7%. Patients with K65R mutations had higher plasma HIV-1 RNA at virological failure compared to patients without K65R mutations (4.9log copies/mL vs. 4.0log copies/mL, p=0.001). By logistic regression analysis only plasma HIV-1 RNA at failure correlated with the occurrence of K65R mutations [OR 4.2 (95% CI, 1.5-11.2) per 0.5log copies/mL increment of HIV-1 RNA]. CONCLUSIONS: Seven percent of patients had K65R mutations after failing an initial d4T/3TC/NVP regimen. Tenofovir, didanosine, and abcavir cannot be used in second-line regimen for these patients. HIV-1 RNA at the time that virological failure was detected correlated with the occurrence of K65R mutations.     

Efficacy and safety of atazanavir, with or without ritonavir, as part of once-daily highly active antiretroviral therapy regimens in antiretroviral-naive patients

BACKGROUND: Atazanavir (ATV), the first once-daily protease inhibitor approved for the treatment of HIV-1 infection, is recommended for use in antiretroviral (ARV) treatment-naive and -experienced patients. Study AI424-089 was a prospective, randomized, open-label, 96-week study comparing 2 ATV-based treatment regimens in ARV-naive HIV-infected patients. METHODS: Adults with HIV RNA levels > or =2000 copies/mL were randomized (1:1) to once-daily ATV at a dose of 300 mg with ritonavir at a dose of 100 mg (ATV300/RTV) or ATV at a dose of 400 mg (ATV400); both regimens included lamivudine and an investigational extended-release formulation of stavudine. The primary endpoint for this noninferiority study was the proportion of patients (response rate) with an HIV RNA load <400 copies/mL at week 48. RESULTS: Response rates at week 48 were 86% and 85% on the ATV300/RTV and ATV400 regimens, respectively (difference estimate [95% confidence interval] = 1.5 [-8.2 to 11.1]). There were 3 and 10 patients with virologic failure in the ATV300/RTV and ATV400 groups, respectively. One patient (ATV400) developed phenotypic resistance to ATV associated with an I50L substitution. Adverse event-related discontinuations were 8% among ATV300/RTV-treated patients and <1% among ATV400-treated patients. Plasma lipid elevations were low with both regimens. Both regimens were well tolerated. CONCLUSIONS: These findings demonstrate the safety and efficacy of the ATV300/RTV regimen and confirm the safety and efficacy of ATV400 in an ARV-naive patient population.     

Open-label phase II trial of amprenavir, abacavir, and fixed-dose zidovudine/lamivudine in newly and chronically HIV-1--infected patients

A Phase II clinical trial was designed to evaluate the efficacy and tolerability of twice-daily abacavir, amprenavir, and zidovudine (ZDV)/lamivudine (3TC) in HIV-1-infected study subjects naive to protease inhibitors and 3TC. Plasma and cerebrospinal fluid (CSF) HIV-1 RNA levels and T-cell subsets were measured. In all, 27 newly diagnosed and 12 chronically HIV-1-infected study subjects are included in the analysis. Week 48 plasma HIV-1 RNA levels were <500 copies/ml in 100% of study subjects, and <50 copies/ml in 80% of chronically infected and 100% of newly infected study subjects. The mean change in CD4 was (+)150 cells/microl (newly infected, p <.001), and (+)155 cells/microl (chronically infected, p <.001). At Week 48, evidence of cellular activation persisted in both cohorts. A twice-daily regimen of amprenavir, abacavir, and ZDV/3TC affords potent viral suppression and significant increases in total CD4(+) cells in HIV-1--infected study subjects. Patient intolerance may limit the efficacy of this combination.