Efficacy and tolerability of stavudine plus lamivudine in treatment-naive and treatment-experienced patients with HIV-1 infection

Rapid plasma viral suppression in naive HIV-infected patients with high CD4 cells and low viraemia initiating a dual nucleoside reverse transcriptase inhibitor strategy: a proof-of-concept study

OBJECTIVES

To evaluate whether a dual nucleoside reverse transcriptase inhibitor (NRTI) strategy can control HIV replication in antiviral therapy (ART)-naive HIV-infected patients with a high CD4 cell count and a low viral load (VL).

METHODS

This observational study included all HIV-infected treatment-naive patients with a CD4 cell count >300 cells/mm(3), a plasma HIV RNA between 1000 copies/mL and 30,000 copies/mL and wild-type virus who initiated dual NRTI ART between January 2008 and December 2012. HIV RNA and CD4 cell count were assessed at Day 0, Week (W) 4, W12, W24 and W48. The primary endpoint was the proportion of patients with a plasma VL (pVL) <50 copies/mL at W24.

RESULTS

Twenty patients were included. The median (IQR) baseline characteristics were: time since HIV diagnosis, 25 months (8-66 months); CD4 cell count, 592 cells/mm(3) (405-798 cells/mm(3)); HIV RNA, 10,395 copies/mL (4106-16,566 copies/mL); and HIV DNA, 464 copies/10(6) peripheral blood mononuclear cells (195-1168 copies/10(6) PBMC). Nineteen patients received tenofovir/emtricitabine and one patient received abacavir/lamivudine. At W12, 88% of the patients with available data (n = 16/18, 95% CI 0.65-0.99) had a pVL <50 copies/mL. Overall, the proportion of patients with a pVL <50 copies/mL was 100% (n = 20/20, 95% CI 0.83-1.0) at W24 and 95% (n = 18/19, 95% CI 0.74-0.99) at W48 (with one patient lost to follow-up and one patient with poor treatment compliance). The median increase in CD4 cells was 83 cells/mm(3) (40-310 cells/mm(3)). There was no discontinuation of antiretroviral therapy for any reason such as lack of efficacy or toxicity.

CONCLUSIONS

This pilot study suggests that, in patients with a high CD4 cell count and a low VL, a dual NRTI strategy may represent a potentially effective treatment strategy to control HIV replication. This needs to be confirmed in larger controlled clinical studies.

A Combined-Formulation Tablet of Lamivudine/Nevirapine/Stavudine: Bioequivalence Compared With Concurrent Administration of Lamivudine, Nevirapine, and Stavudine in Healthy Indian Subjects

Generic fixed-dose combinations of antiretrovirals are frequently prescribed for the treatment of human immunodeficiency virus infection. A randomized, 2-way study was conducted in 24 fasting, healthy, Indian male subjects to assess bioequivalence between a single combination tablet containing lamivudine, stavudine, and nevirapine (treatment A) with respect to separate marketed tablets administered simultaneously (treatment B). Each subject received treatments A and B separated by 19 days of a drug-free washout period. Plasma concentrations of antiretrovirals, determined by a validated liquid chromatography/tandem mass spectrometry assay, were used to assess pharmacokinetic parameters such as maximum observed plasma concentration and area under the plasma concentration curve. Pharmacokinetic parameters were comparable for either treatment. As geometric mean ratios (% treatment A/treatment B) of log-transformed parameters of area under the plasma concentration curve and plasma concentration, as well as their resultant 90% confidence intervals, were within 80% to 125% and 75% to 133%, respectively, 2 treatments were considered bioequivalent in the extent and rate of absorption. Both treatments exhibited similar tolerability under fasting conditions.

Quantum chemical and experimental studies on polymorphism of antiviral drug Lamivudine

Lamivudine, is chemically known as [4-amino-1-[(2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-1,2-dihydropyrimidin-2-one], is an anti-HIV agent belonging to the class of the non-nucleoside inhibitors of the HIV-1 virus reverse transcriptase. Spectral characteristics of Lamivudine have been studied by methods of FTIR, NMR and quantum chemistry. The FTIR and spectra of Lamivudine was recorded in the regions 4000-400 cm(-1). The thermal stability of Lamivudine was studied by the thermogravimetric analysis (TGA). The isotropic (13)C-nuclear magnetic shielding constants of this compound were calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the HF and B3LYP density functional theory using 6-31G(d,p) basis set. The optimized molecular geometry, bond orders, harmonic vibrational spectrum of anhydrous and hydrated Lamivudine were calculated by restricted Hartree Fock and density functional B3LYP method with the 6-31G(d,p) basis set using Gaussian 03W program.

Disease progression in HIV-infected patients treated with stavudine vs. zidovudine

BACKGROUND AND OBJECTIVES

This prospective, observational study compared disease progression and death in HIV-1 patients treated with stavudine vs. zidovudine in the Collaborations in HIV Outcomes Research/U.S. (CHORUS) cohort.

METHODS

Patients with a first occurrence of CD4 count <500 cells/microL (n=3301) were grouped as: no nucleoside reverse transcriptase inhibitor (NRTI) use; other NRTI without stavudine or zidovudine; stavudine with no zidovudine, with or without other NRTIs; and zidovudine with no stavudine, with or without other NRTIs. The risk for death or disease progression was evaluated in unadjusted analyses and using a Cox proportional hazards model, adjusting for: study site, age, gender, race, route of HIV infection, previous AIDS-defining conditions, number of previous antiretroviral regiments, CD4 count, HIV-1 RNA, and treatment variables. Sensitivity analyses were conducted to determine the sensitivity of the results to major modeling assumptions. A landmark analysis was conducted to determine the absolute difference in time to event.

RESULTS

During a median follow-up of 2.4 years, there were 57 deaths and 348 AIDS-defining conditions in 405 patients. Stavudine treatment compared with zidovudine resulted in a greater percentage of patients with AIDS-defining events (14.5 vs. 10.9%; P=.013), and an increased risk of disease progression (HR=1.30; 95% CI: 1.01,1.7; P=.04). This result was not sensitive to modeling assumptions. Landmark analysis demonstrated an absolute difference in time to 95% event-free survival of 2.7 months for those with a CD4< or =200 cells/microL and 11 months for those 6 months after model entry.

CONCLUSIONS

In unadjusted and adjusted analyses of 3301 HIV-1 infected patients, stavudine containing combination therapy was associated with an increased risk of disease progression or death compared to therapy containing zidovudine. Most of the difference was attributable to new cases of wasting.

The prevalence of reduced zidovudine susceptibility in zidovudine-naive, antiretroviral-experienced HIV-1-infected patients

OBJECTIVES

There is increasing in vitro and in vivo evidence that reduced zidovudine (ZDV) susceptibility is generated by the selective pressure conferred by other nucleoside reverse transcriptase inhibitors (NRTIs). However, the degree to which this occurs in clinical practice remains unclear. We assessed phenotypic and genotypic resistance in ZDV-naive patients with virological failure on stavudine (d4T)-containing regimens, with particular reference to potential cross-resistance between d4T and ZDV.

METHODS

Patients were identified from a clinical database. Treatment history was confirmed by case note evaluation and discussion with patients. Genotypic and phenotypic analyses were undertaken by Virco (Virco BVBA, Mechelen, Belgium).

RESULTS

Sixty-seven drug-experienced, ZDV-naive patients who underwent a resistance test while failing a d4T-containing regimen were identified. Of these patients, 23% had received three or more NRTIs and 42% at least one non-nucleoside reverse transcriptase (RT) inhibitor; 22% had viruses with reduced d4T susceptibility (>1.8-fold resistance), and 25% had viruses with reduced ZDV susceptibility (>4-fold). The most frequently observed RT mutations were identified. A significant correlation was found between susceptibility to d4T and susceptibility to ZDV (r=0.36; P=0.003), and also between virtual resistance to d4T and that to ZDV (r=0.38; P=0.002).

CONCLUSIONS

A significant minority of d4T-treated, ZDV-naive patients were found to have viruses with reduced ZDV susceptibility, with a variable association with classical ZDV resistance mutations. These data suggest that cross-resistance between d4T and ZDV may involve novel constellations of mutations. Correlations between d4T and ZDV susceptibilities and resistances further support cross-resistance between NRTIs.

-Dual nucleoside therapy for HIV infection: analysis of results and factors influencing viral response and long term efficacy

We performed a retrospective analysis of our experience with dual nucleoside regimens to look for predictors of long term benefit. The study evaluated a cohort of 68 HIV-infected patients treated at 3 Italian hospital-based facilities. The results were evaluated using univariate and multivariate statistical analysis. Fourty-three males and 25 females were treated for 22 +/- 14 months. Sixty three patients (92.6%) suffered no or low-grade side-effects. Thirty-four patients (50%) reached a viral load <400 copies/ml (undetectable). Viremia remained persistently undetectable in 9 cases (13.2%). Variable relapses of viremia were seen in 13 patients (19.1%) even though their therapys were not modified. Eight patients (11.8%) showed relapsing viremias persistently around or below 10,000 copies/ml. All patients reaching undetectable viremia but one showed increasing or stable CD4+ cell counts. Factors predicting favourable response were: pre-treatment CD4+ T-cells >150/microl, pre-treatment viremia <50,000 copies/ml, pre-treatment lymphocytes >1,500/microl, and no previous exposure to NRTI. Total lymphocyte counts and CD4+ T-cells showed a significant correlation. Dual NRTI regimens may be still considered for patients unable to tolerate HAART regimens and presenting with favourable predictors of response.

Determination of lamivudine/stavudine/efavirenz in human serum using liquid chromatography/electrospray tandem mass spectrometry with ionization polarity switch

A high-performance liquid chromatography/tandem mass spectrometry (LC-MS-MS) method with ionization polarity switch was developed and validated in human serum for the determination of a lamivudine (3TC)/stavudine (d4T)/efavirenz combination HIV therapy. Solid phase extraction (SPE) was used to extract these anti-HIV drugs and internal standard aprobarbital. A gradient mobile phase consisting of acetonitrile and 20 mM ammonium acetate buffer with pH adjusted to 4.5 using glacial acetic acid was utilized to separate these drugs on a hexylsilane column (150 x 2.0 mm i.d.). The total run time between injections was 18 min. The precursor and major product ions of these drugs were monitored on a triple quadrupole mass spectrometer in the multiple reactions monitoring (MRM) mode. Ionization polarity was switched in the middle of the LC run allowing these anti-HIV drugs with different physicochemical properties to be detected simultaneously. The effect of ion suppression from human serum was studied and no interference with the analysis was noted. The method was validated over the range of 1.1-540 ng/mL for 3TC, 12.5-6228 ng/mL for d4T and 1.0-519 ng/mL for efavirenz. The method was shown to be accurate, with intra-day and inter-day accuracy less than 14.0% and precise, with intra-day and inter-day precision less than 13.1%. The extraction recoveries of all analytes were higher than 90%.

Efficacy of zidovudine compared to stavudine, both in combination with lamivudine and indinavir, in human immunodeficiency virus-infected nucleoside-experienced patients with no prior exposure to lamivudine, stavudine, or protease inhibitors (novavir trial)

We compared the efficacy and the toxicity of zidovudine (AZT) versus stavudine (d4T), in combination with lamivudine (3TC) and indinavir, in AZT-, dideoxyinosine (ddI)-, and/or dideoxycytosine (ddC)-experienced patients in a randomized comparative multicenter trial. One hundred seventy human immunodeficiency virus type 1 (HIV-1)-infected patients, who had received AZT, ddI, and/or ddC for at least 6 months but were naive for d4T, 3TC, and protease inhibitors, were randomized to AZT at 250 to 300 mg twice daily, 3TC at 150 mg twice daily, and indinavir at 800 mg every 8 h or to d4T at 40 mg twice daily, 3TC at 150 mg twice daily, and indinavir at 800 mg every 8 h. The primary endpoint was time to virological failure, defined as plasma HIV-1 RNA levels of >5,000 copies/ml after at least 8 weeks of antiretroviral therapy. Additional endpoints were change from baseline in CD4 cell counts, AIDS-defining events and adverse events, and proportion of patients with HIV-1 RNA levels of <500 copies/ml and HIV-1 RNA levels of <50 copies/ml. At week 80, 15 patients in the AZT arm and 14 patients in the d4T arm had reached the primary endpoint, and time to virological failure did not differ between the two arms (P = 0.98). In the d4T and in the AZT arms, 67 and 73% of patients, respectively, had HIV-1 RNA levels of <500 copies/ml (P = 0.50). The median change from baseline in CD4 cell count was 195 x 10(6) and 175 x 10(6)/liter for the d4T- and AZT-containing arms, respectively. The proportions of patients with HIV-1 RNA levels of <50 copies/ml at weeks 8, 16, and 24 were similar in the two arms. The occurrence of serious adverse events was not significantly different between arms. In conclusion, in these patients heavily pretreated with AZT, switching from AZT to d4T when initiating indinavir and 3TC did not bring any additional benefit compared to maintaining AZT.

Impact of Stavudine Phenotype and Thymidine Analogues Mutations on Viral Response to Stavudine plus Lamivudine in Altis 2 Anrs Trial

Objective

Stavudine-based antiretroviral combinations are less effective in zidovudine-experienced patients than in naive subjects and recently, mutations have been described to be associated to the use of both stavudine and zidovudine. In the ALTIS 2 trial, it was shown that a combination of stavudine and lamivudine is less effective in zidovudine-experienced patients than in naive patients. We conducted a retrospective genotypic and phenotypic resistance study (expressed as stavudine phenotypic index, calculated by dividing the inhibitory concentrations 50% [IC50] by the mean value of the sensitive viruses) to evaluate the factors associated with decrease in plasma HIV-1 RNA.

Design

Associations with continuous variables were studied using non-parametric Spearman correlation coefficients. Associations with categorical variables were studied using non-parametric Mann–Whitney tests. Multivariate stepwise regression analyses were used to determine independent prognostic factors of the virological response.

Results

At baseline, most of the subjects harboured zidovudine-associated mutations in plasma and peripheral blood mononuclear cells. Zidovudine and stavudine IC50 and IC90 were strongly associated with response. It appears that a cut-off of stavudine phenotypic index of 1.8-fold of IC50, much lower than the usually used value, could be clinically significant for response to stavudine. In the multivariate analysis, the stepwise model with the higher multiple correlation coefficient ( R2=0.742) included the presence of a 215 Y/F mutation, the number of previously used nucleoside analogues and a resistant stavudine phenotype.

Conclusion

These results argue for a phenotypic and genotypic cross resistance between stavudine and zidovudine. Modest increases of IC50 and IC90 for stavudine had an important impact on the virological response during the trial and plead for a new definition of the threshold value for stavudine phenotypic index.

Discordance between genotypic and phenotypic drug resistance profiles in human immunodeficiency virus type 1 strains isolated from peripheral blood mononuclear cells

The aim of the study was to analyze the relationship between genotypic and phenotypic drug resistance profiles of human immunodeficiency virus type 1 (HIV-1) strains isolated from patients during double-analogue nucleoside therapy. A drug-resistant HIV strain was isolated from 20 out of 25 patients, with 16 (64%) subjects carrying a virus with multiple drug resistance mutations. The most frequent resistance mutations were M184V (18 isolates) and M41L (7 isolates). Discordance between the genotypic and phenotypic profile for at least one drug was detected in 16 out of 25 strains. Particularly, eight isolates had a discordant genotypic-phenotypic resistance pattern for two drugs and one isolate had such a pattern for three drugs. A genotypic resistance pattern with a phenotypic sensitivity profile was detected in six isolates (four resistant to zidovudine and two resistant to lamivudine). On the other hand for several strains a genotypic pattern of sensitivity pattern to abacavir (10 strains), didanosine (7 strains), stavudine (3 strains), zidovudine (2 strains), and lamivudine (1 strain) with a phenotypic resistance profile was detected. After a follow-up period of 8 months, an impairment of virological and immunological parameters was detected only in subjects with an HIV-1 isolate with a phenotypic resistance profile in despite of the genotypic results. Predicting resistance phenotype from genotypic data has important limitations. Despite the low number of patients and the short follow-up period, this study suggests that during failing therapy with analogue nucleosides, a phenotypic analysis could be performed in spite of an HIV genotypic sensitivity pattern.

The emergence of different resistance mechanisms toward nucleoside inhibitors is explained by the properties of the wild type HIV-1 reverse transcriptase

Nucleoside reverse transcriptase inhibitors (NRTIs) represent one of the main drug families used against AIDS. Once incorporated in DNA, they act as chain terminators, due to the lack of a 3'-hydroxyl group. As for the other anti-human immunodeficiency virus type 1 drugs, their efficiency is limited by the emergence of resistant viral strains. Unexpectedly, previous studies indicated that resistance toward NRTIs is achieved via two distinct and generally exclusive mechanisms. Resistance mutations either decrease the efficiency of NRTIs incorporation or increase their excision from the extended primer. To understand the emergence of different resistance mechanisms toward a single inhibitor class, we compared the incorporation and the pyrophosphorolysis of several NRTIs using wild type reverse transcriptase (WT RT). We found that the efficiency of discrimination or excision by pyrophosphorolysis in the presence of nucleotides of a given NRTI is a key determinant in the emergence of one or the other resistance pathway. Indeed, our results suggest that the pathway by which RT become resistant toward a given NRTI can be predicted by studying the inhibition of WT RT, because the resistance mutations do not confer new properties to the mutant enzyme, but rather exacerbate pre-existing properties of the WT enzyme. They also help to understand the low cross-resistance toward d4T observed with the 3'-azido-3'-deoxythymidine (AZT or zidovudine)-resistant RT.

Failure of stavudine-lamivudine combination therapy in antiretroviral-naive patients with AZT-like HIV-1 resistance mutations

To analyze the clinical relevance of AZT resistance mutations in AZT-naive patients, 56 HIV-1 seropositive patients treated for 18 months with stavudine/lamivudine (27 patients) or AZT/lamivudine (29 patients) were studied. AZT-like resistance mutations were found in 13 out of 29 (44%) patients treated with AZT/lamivudine and in 11 out of 27 (40%) patients treated with stavudine/lamivudine. No stavudine or multi-drug resistance mutations were detected. After 26 months of treatment more than 60% of patients showed a virological failure. Among 10 patients failing treatment with stavudine/lamivudine, 9 had AZT-like resistance mutations. The phenotypic test, performed on HIV-1 strains isolated from six of these nine patients, showed a resistance to AZT in five isolates and to stavudine in two isolates. The genotypic pattern of the latter two isolates showed the combined mutations M184V plus R211K and L214F. AZT-like resistance mutations in AZT-naive patients seem to correlate with a virological failure during long-term stavudine therapy.

Baseline antiretroviral drug susceptibility influences treatment response in patients receiving saquinavir-enhancing therapy

PURPOSE

To relate baseline plasma HIV genotypic and virtual phenotypic antiretroviral drug susceptibility to subsequent virological response in patients receiving saquinavir (SQV)-enhancing therapy. Individuals were randomized to receive stavudine (d4T), SQV, and one of ritonavir, nelfinavir, or delavirdine to enhance SQV blood levels.

METHOD

The protease and reverse transcriptase baseline sequences of 31 treatment-experienced patients were analyzed by genotype and virtual phenotype and were related to viral load at weeks 12 and 24. Genotypic resistance to SQV was defined by the presence of G48V and/or L90M mutations in the protease gene. Potential cross-resistance to d4T in zidovudine (ZDV)-experienced individuals was defined by the presence of thymidine-associated mutations in the reverse transcriptase gene.

RESULTS

ZDV-associated mutations did not affect the virological response at 24 weeks. Individuals who were sensitive to SQV at baseline as determined by either genotyping or virtual phenotyping showed a greater decrease in viral load at week 24 than those resistant to SQV, irrespective of treatment arm. By genotyping, SQV-sensitive individuals had a median log decrease of 1.12 compared to 0.32 for those individuals who were SQV resistant. By virtual phenotyping, SQV-sensitive individuals had a median log decrease of 1.0 compared to a rise of 0.08 in resistant individuals.

CONCLUSION

Thymidine analogue-associated mutations at baseline did not influence the response to subsequent therapy involving d4T. Individuals who were sensitive or resistant to SQV by genotyping or virtual phenotyping responded to SQV-enhancing regimens, but the virological response was greater in those who were sensitive.

Low-Rate Emergence of Thymidine Analogue Mutations and Multi-Drug Resistance Mutations in the HIV-1 Reverse Transcriptase Gene in Therapy-Naive Patients Receiving Stavudine plus Lamivudine Combination Therapy

Objectives

Mutations usually associated with zidovudine exposure have been observed in zidovudine-naive patients treated by stavudine in combination. These mutations were named thymidine analogue mutations (TAMs). This fact, combined with phenotypical and biochemical findings provided additional evidence for cross-resistance between zidovudine and stavudine. A recent genotypic study in naive patients receiving stavudine/didanosine combination showed emergence of TAMs and a multidrug-resistance mutation (MDR), Q151M, in 36 and 10% of cases, respectively. Stavudine plus lamivudine is one of the most used binucleoside associations in the antiretroviral combinations. The objective of this study was to assess the genotypic changes in the HIV-1 reverse transcriptase (RT) gene in antiretroviral-naive patients treated by stavudine plus lamivudine.

Methods

We analysed the RT gene of 44 HIV-1 patients, naive of antiretroviral therapy, who were treated for 24 or 48 weeks with stavudine/lamivudine. Results: At the end of the follow-up, all patients acquired the lamivudine-associated mutation M184V. Only two subjects (4.5%) developed a TAM (T215Y; M41L), one subject developed a V75T/A mutation and one subject developed the particular MDR pattern F116Y, Q151M.

Conclusions

Our study clearly demonstrated that naive subjects treated with stavudine/lamivudine for 24–48 weeks selected a low rate of TAMs and MDR Q151M. One hypothesis explaining these results could be the development of the M184V mutation.

Influence of prior exposure to zidovudine on stavudine phosphorylation in vivo and ex vivo

Intracellular phosphorylation of stavudine (d4T) and zidovudine (ZDV) was investigated in peripheral blood mononuclear cells (PBMCs) isolated from ZDV-naive and ZDV-experienced human immunodeficiency virus (HIV)-positive patients. An in vivo study measured the amount of d4T triphosphate (d4TTP), while an ex vivo study assessed the capacity of cells to phosphorylate added d4T. Endogenous dTTP was also measured. d4TTP and dTTP were determined in vivo using a reverse transcriptase chain termination assay. In ex vivo studies, d4T (1 microM) was incubated in resting and phytohemagglutinin-stimulated (10 microg ml(-1); 72 h) PBMCs for 24 h. After washing and methanol extraction, radiolabeled anabolites were detected by high-performance liquid chromatography. d4TTP reached its highest level 2 to 4 h after dosing (0.21 +/- 0.14 pmol/10(6) cells; n = 27 [mean +/- standard deviation]). Comparison of ZDV-naive and ZDV-experienced individuals showed no significant difference in levels of d4TTP (ZDV naive, 0.23 +/- 0.17 pmol/10(6) cells [n = 7] versus ZDV experienced, 0.20 +/- 0.14 pmol/10(6) cells [n = 20]; P = 0.473) or the d4TTP/dTTP ratio (0.14 +/- 0.12 [n = 7] and 0.10 +/- 0.08 [n = 20], respectively; p = 0.391). Ex vivo data demonstrated no significant difference in the formation of d4TTP or total d4T phosphates in naive and experienced patients (0.086 +/- 0.055 pmol/10(6) cells in ZDV-naive patients [n = 17] versus 0.081 +/- 0.038 pmol/10(6) cells in ZDV-experienced patients [n = 22]; P = 0.767). The ability of HIV-infected patients to phosphorylate d4T in vivo and ex vivo was unchanged with increasing exposure to ZDV.

Zidovudine and stavudine sequencing in HIV treatment planning: findings from the CHORUS HIV cohort

BACKGROUND

Optimal sequencing of zidovudine and stavudine in antiretroviral therapy has not been elucidated.

OBJECTIVE

To examine the impact of the sequence of therapeutic regimens containing zidovudine and stavudine on HIV-1 RNA and CD4 lymphocyte counts over 12 months.

DESIGN

Observational, multicenter, longitudinal cohort study.

SETTING

Four large outpatient, HIV practices participating in the community-based Collaborations in HIV Outcomes Research-U.S. (CHORUS) cohort study.

PARTICIPANTS

940 HIV-infected patients.

METHODS

Comparison of HIV-1 RNA and CD4 lymphocyte responses in patients sequenced from zidovudine to stavudine or from stavudine to zidovudine using repeated measures regression models fit to outcomes by application of generalized estimating equation (GEE) methodology.

RESULTS

Patients treated with zidovudine prior to stavudine (n = 834) achieved a greater mean drop from baseline HIV-1 RNA (p = .01) and higher proportion of undetectable HIV-1 RNA results (p = .05) over 12 months than those sequenced from stavudine to zidovudine (n = 106). CD4+ lymphocyte increases did not differ between the groups (p = .6).

CONCLUSIONS

Prior zidovudine therapy was not associated with long-term attenuation of HIV-1 RNA or CD4 response to subsequent stavudine-containing regimens. Zidovudine before stavudine may have benefit in a strategic long-term therapeutic plan.

Antiretroviral Resistance: Mechanisms, Detection and Clinical Implications

Widespread use of antiretroviral agents and the epidemic of human immunodeficiency virus (HIV) strains resistant to these drugs have raised a lot of issues including the biology and clinical implications of HIV resistance, reliability of resistant assays and their role in clinical practice. In May 2000, the International AIDS panel endorsed and recommended the use of antiretroviral drug resistance testing in patients. Considerable data on HIV drug resistance testing that strongly suggest that utility of these assays may be of great value have been published and presented at major meetings. Although the genotypic and phenotypic assays are available for antiretroviral drug resistance testing, the testing has certain limitations. The role of these resistance assays is not clearly defined in clinical practice. Prospective studies are needed to define the long-term benefits of these assays. HIV drug resistance testing in the near future may become an important tool and standard of practice for patients infected with HIV. Clinicians caring for HIV-positive patients should be familiar with the antiretroviral drug resistant assays.

Differential removal of thymidine nucleotide analogues from blocked DNA chains by human immunodeficiency virus reverse transcriptase in the presence of physiological concentrations of 2'-deoxynucleoside triphosphates

Removal of 2',3'-didehydro-3'-deoxythymidine-5'-monophosphate (d4TMP) from a blocked DNA chain can occur through transfer of the chain-terminating residue to a nucleotide acceptor by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). ATP-dependent removal of either d4TMP or 3'-azido-3'-deoxythymidine-5'-monophosphate (AZTMP) is increased in AZT resistant HIV-1 RT (containing D67N/K70R/T215F/K219Q mutations). Removal of d4TMP is strongly inhibited by the next complementary deoxynucleoside triphosphate (50% inhibitory concentration [IC(50)] of approximately 0.5 microM), whereas removal of AZTMP is much less sensitive to this inhibition (IC(50) of >100 microM). This could explain the lack of cross-resistance by AZT-resistant HIV-1 to d4T in phenotypic drug susceptibility assays.

Zidovudine triphosphate and lamivudine triphosphate concentration-response relationships in HIV-infected persons

OBJECTIVE

To quantitate intracellular concentrations of zidovudine and lamivudine triphosphate and explore relationships with virologic and immunologic responses to antiretroviral therapy.

DESIGN

Eight antiretroviral-naive, HIV-infected persons with CD4 T cell counts > 100 x 10(6) cells/l, and HIV RNA in plasma > 5000 copies/ml participating in a prospective, randomized, open-label study of standard dose versus concentration-controlled therapy with zidovudine, lamivudine, and indinavir.

METHODS

Peripheral blood mononuclear cells and plasma were collected frequently throughout the study for quantitation of intracellular zidovudine triphosphate and lamivudine triphosphate concentrations, and zidovudine and lamivudine concentrations in plasma. CD4 T cells and HIV RNA in plasma (Roche Amplicor Ultrasensitive Assay) were measured at baseline and every 4 weeks throughout the study. Relationships among intracellular and plasma concentrations, and CD4 T cells and HIV RNA in plasma were investigated with regression analyses.

RESULTS

Significant relationships were observed between the intracellular concentrations of zidovudine triphosphate and lamivudine triphosphate and the baseline level of CD4 cells. Lamivudine triphosphate concentrations were related in a linear manner to the apparent oral clearance of lamivudine from plasma. A direct linear relationship was found between the intracellular concentrations of zidovudine triphosphate and lamivudine triphosphate. The percent change in CD4 cells during therapy and the rate of decline in HIV RNA in plasma were related to the intracellular concentrations of zidovudine triphosphate and lamivudine triphosphate.

CONCLUSION

These studies into the intracellular clinical pharmacology of nucleoside reverse transcriptase inhibitors illustrate potential clinical implications as determinants of therapeutic success. Moreover, these findings provide several leads and a strong impetus for future investigations with nucleoside reverse transcriptase inhibitors particularly when given in combination and sequentially.

Consensus statement: anemia in HIV infection--current trends, treatment options, and practice strategies. Anemia in HIV Working Group

BACKGROUND

Despite important advances in antiretroviral therapy, anemia remains a problem in many HIV-infected patients. Although the incidence of anemia in these patients has decreased, its prevalence appears to have stabilized or decreased only slightly. Anemia has a deleterious effect on both functional capacity and quality of life, and has been associated with shortened survival.

OBJECTIVE

The Anemia in HIV Working Group, an expert panel of physicians and researchers involved in the care of HIV-infected patients, met to determine the impact of anemia in this patient population; to develop practice strategies for the clinician treating HIV-infected patients with anemia; and to identify future research directions.

METHODS

The proposed practice strategies are based on results of the available clinical trials (as identified through a MEDLINE search), a review of the literature, and the clinical experience and expert opinion of the panel. The present report is based on meetings held in February and June of 1998; as further experience with various treatment options accumulates and the impact of highly active antiretroviral therapy becomes clearer, the panel will reconvene to develop evidence-based guidelines.

RESULTS

The working group considers HIV-associated anemia to be an important contributor to the morbidity and mortality of this infection. Recent reports indicate that recovery from anemia is associated with improved quality of life and survival.

CONCLUSIONS

As HIV-infected persons live longer, maintaining quality of life becomes an increasingly important goal of treatment. When planning treatment strategies, clinicians should consider the quality-of-life decrement caused by anemia. Transfusions should be used when rapid recovery is required, and underlying conditions causing anemia should be treated, if possible. Recombinant human erythropoietin (rHuEPO) therapy is appropriate in certain HIV-infected persons and should be considered to maintain hemoglobin concentrations. The target hemoglobin level is 12 g/dL for men and 11 g/dL for women. Weekly rHuEPO dosing is suggested, initiated at 40,000 U, as has been established in patients with cancer.

Continued lamivudine versus delavirdine in combination with indinavir and zidovudine or stavudine in lamivudine-experienced patients: results of Adult AIDS Clinical Trials Group protocol 370

OBJECTIVE

To compare the virologic activity of continued lamivudine (3TC) versus a switch to delavirdine (DLV) when initiating protease inhibitor therapy in nucleoside-experienced patients.

DESIGN

Randomized, open-label, multi-center study.

SETTING

Adult AIDS clinical trials units.

PATIENTS

Protease and non-nucleoside reverse transcriptase inhibitor-naive patients who had received 3TC plus zidovudine (ZDV), stavudine (d4T), or didanosine (ddl) for at least 24 weeks.

INTERVENTIONS

Patients with plasma HIV-1 RNA levels > 500 copies/ml who previously received d4T + 3TC or ddI + 3TC were randomized to ZDV + 3TC + indinavir (IDV) or ZDV + DLV + IDV.

MAIN OUTCOME MEASURES

Primary endpoints were the proportion of patients with plasma HIV-1 RNA levels < or = 200 copies/ml at 24 weeks, and occurrence of serious adverse events. The proportion of patients with plasma HIV-1 RNA levels < or = 200 copies/ml at week 48 was a secondary endpoint.

RESULTS

At week 24, 58% of subjects in the ZDV + 3TC + IDV arm and 73% in the ZDV + DLV + IDV arm had plasma HIV-1 RNA levels < or = 200 copies/ml (P = 0.29). At week 48, plasma HIV-1 RNA levels were < or = 200 copies/ml in 48% and 83%, respectively (P = 0.007). Rash and hyperbilirubinemia occurred more frequently in the DLV arm than in the 3TC arm. Steady-state plasma IDV levels were higher among patients in the DLV arm as compared with the 3TC arm.

CONCLUSIONS

Substituting DLV for 3TC when adding IDV improved virologic outcome in nucleoside-experienced patients. This result might be explained, in part, by the positive effect of DLV on IDV pharmacokinetics.

A comparison of stavudine plus lamivudine versus zidovudine plus lamivudine in combination with indinavir in antiretroviral naive individuals with HIV infection: selection of thymidine analog regimen therapy (START I)

BACKGROUND

No clinical trial results directly comparing two nucleoside analog pairs in a drug regimen for HIV that includes a protease inhibitor are available.

OBJECTIVE

To compare the safety and efficacy of stavudine (d4T) + lamivudine (3TC) with zidovudine (ZDV) + 3TC, each in combination with indinavir (IDV).

DESIGN

Randomized, open-label, multi-center.

SETTING

Fifteen HIV clinical research centers.

PATIENTS

Two-hundred and four antiretroviral-naive HIV-1-infected-patients with CD4 cell counts > or = 200 x 10(6)/l and HIV-1 RNA > or = 10,000 copies/ml (bDNA assay), modified to 5000 copies/ml.

INTERVENTION

d4T 40 mg twice a day, 3TC 150 mg twice a day plus IDV 800 mg every 8 h compared with ZDV 200 mg every 8 h (modified to 300 mg every 12 h) plus 3TC and IDV.

MEASUREMENTS

Primary endpoint: plasma HIV-1 RNA < 500 copies/ml. Additional endpoints: HIV-1 RNA < or = 50 copies/ml; change from baseline in HIV-1 RNA and CD4 cell counts; safety and adverse events.

RESULTS

For HIV-1 RNA, 62% of patients on d4T + 3TC + IDV and 54% of patients on ZDV + 3TC + IDV had < 500 copies/ml HIV RNA at weeks 40 through 48 [90% confidence interval, -0.204 to 0.036; P= 0.213], with 49% and 47% respectively achieving < or = 50 copies/ml at 48 weeks (90% CI, -0.134 to 0.096; P = 0.834). Median change in CD4 cell counts at 48 weeks was +227 x 10(6)/l and +198 x 10(6)/l for the d4T- and ZDV-containing arms, respectively. The median time-weighted average change from baseline in CD4 cell counts was significantly greater at 48 weeks in the d4T-containing arm (142 x 10(6)/l versus 110 x 10(6)/l; P = 0.033). Serious adverse events were not significantly different between treatment arms, but there were significant differences for frequency of adverse events of all severity with increased nausea and vomiting in the ZDV-containing arm, and increased diarrhea and rash in the d4T-containing arm.

CONCLUSIONS

These results support the choice of d4T + 3TC as a nucleoside analog pair in combination with a protease inhibitor in an initial HIV treatment regimen.

A comparison of stavudine, didanosine and indinavir with zidovudine, lamivudine and indinavir for the initial treatment of HIV-1 infected individuals: selection of thymidine analog regimen therapy (START II)

OBJECTIVE

Comparison of stavudine (d4T), didanosine (ddI) and indinavir (IDV) with zidovudine (ZDV), lamivudine (3TC) and IDV in HIV-1 infected patients.

DESIGN

Randomized, open-label.

SETTING

Fourteen HIV Clinical Research Centers.

PATIENTS

Two-hundred and five patients with less than 4 weeks antiretroviral treatment, naive to 3TC and protease inhibitors and with CD4 cell counts > or = 200 x 10(6)/l and plasma HIV-1 RNA levels > or = 10,000 copies/ml.

INTERVENTIONS

Stavudine 40 mg and ddI 200 mg twice daily plus IDV 800 mg every 8 h compared with ZDV 200 mg every 8 h or 300 mg twice daily, 3TC 150 mg twice daily plus IDV.

MAIN OUTCOME MEASURES

The proportion of patients with plasma HIV-1 RNA levels < 500 copies/ml and < or = 50 copies/ml and changes in CD4 cell counts were compared.

RESULTS

In an analysis of the primary endpoint, 61% of patients on d4T + ddI + IDV and 45% of patients on ZDV + 3TC + IDV had all HIV-1 RNA values obtained between weeks 40 and 48 < 500 copies/ml [95% confidence interval (CI) for the difference between proportions, 1.7-30.3%; P = 0.038]. In an intent-to-treat analysis, the percentage of all patients randomized with all HIV-1 RNA levels < 500 copies/ml between 40 and 48 weeks were 53% for the d4T + ddI + IDV arm and 41% for the ZDV + 3TC + IDV arm (95% CI, -1.4% to 25.7%; P = 0.068). At 48 weeks 41% and 35% were < or = 50 copies/ml for the stavudine- and ZDV-containing arms respectively (P > 0.2). The median time-weighted average increases in CD4 cells count over 48 weeks were 150 x 10(6)/l cells for the d4T arm and 106 x 10(6)/l cells for the ZDV arm (P= 0.001). The occurrence of serious adverse events was not significantly different between arms.

CONCLUSION

The combination of stavudine, ddl and IDV resulted in potent antiretroviral effects over a 48-week period, comparable or superior to zidovudine, 3TC and IDV supporting the use of stavudine, ddI and a protease inhibitor as an initial antiretroviral treatment.

Experience with Nevirapine in Previously Treated HIV-1-Infected Individuals

Objective

To assess the tolerability, virological, immunological and clinical effects of nevirapine in the setting of a compassionate use programme in pretreated HIV-infected individuals.

Design

Retrospective observational cohort-study in 13 HIV-outpatient clinics in The Netherlands.

Methods

Main outcome measures: plasma HIV-1 RNA levels; CD4 cell counts; incidence of new AIDS-defining diseases; multivariate analysis of predictors for virological success; incidence of skin rashes.

Results

187 HIV-infected individuals treated with nevirapine in the Nevirapine Named Patient Programme in The Netherlands were included. After 48 weeks, 38% of patients had an HIV-1 RNA level below 1000 copies/ml. In multivariate regression analysis, prior treatment with three or less nucleoside analogue reverse transcriptase inhibitors, and a higher baseline CD4 cell count was predictive of virological success. The median CD4 cell count remained stable over the 48 weeks. Eleven patients experienced a new AIDS-defining event. The total incidence of rash (including rash not leading to discontinuation of nevirapine) was 13.9 and 6.4% of the patients discontinued nevirapine because of rash. None of the 28 patients with undetectable HIV-1 RNA levels at baseline developed a rash.

Conclusions

We conclude that nevirapine when used as part of salvage therapy, is safe and most likely to give sustained suppression of HIV-1 in patients that have been less extensively pretreated. CD4 cell counts remained stable despite the low rate of virological success, this also occurred in patients not concurrently using protease inhibitors (PIs). The incidence of nevirapine-related rash in PI-pretreated patients and especially in patients with undetectable HIV-1 RNA levels at the start of nevirapine treatment, is considerably lower than previously reported for antiretroviral-naive patients.

Safety and antiretroviral effects of combined didanosine and stavudine therapy in HIV-infected individuals with CD4 counts of 200 to 500 cells/mm3

The safety and antiretroviral effects of didanosine and stavudine in combination were evaluated in 86 people infected with HIV with CD4 counts between 200 and 500 cells/mm3 who had received <7 days of prior nucleoside analogue antiretroviral treatment. Patients were randomized to receive blinded treatments with one of five weight-adjusted, twice-daily regimens of didanosine and stavudine (100 + 10 mg, 100 + 20 mg, 100 + 40 mg, 200 + 20 mg, and 200 + 40 mg) for up to 1 year. Dosages were adjusted appropriately for patients weighing <60 kg and reduced in response to adverse effects. No clear dose-related differences among treatment groups were detected with regard to suppression of plasma HIV RNA level or reduction in infectious titers in peripheral blood mononuclear cells (PBMCs), improvement in CD4 count, or adverse effects. However, trends toward greater decreases in viral load and increases in CD4 count were detected when treatment groups containing the full recommended dosage of one or both agents (high-dose subgroup; arms 3, 4, and 5) were compared with the groups receiving lower dosages. At 28 weeks the mean log 10 HIV RNA decrease was 1.12 (n = 52) and at 52 weeks it was 0.97 (n = 32). Combination therapy was well tolerated, with no apparent dose-related adverse effects. Peripheral neuropathy occurred in 2 of 86 (2.3%) of patients. Didanosine and stavudine together appear to be a good nucleoside analogue foundation for aggressive triple- or quadruple-drug therapy. Full therapeutic doses of each of these two agents should be used to achieve optimal suppression of HIV replication.

Efficacy and safety of delavirdine mesylate with zidovudine and didanosine compared with two-drug combinations of these agents in persons with HIV disease with CD4 counts of 100 to 500 cells/mm3 (ACTG 261). ACTG 261 Team

To evaluate the antiretroviral activity of delavirdine mesylate, a non-nucleoside reverse transcriptase inhibitor of HIV-1, we performed a phase II, randomized, double-blind, multicenter trial comparing the three-drug combination of delavirdine with zidovudine and didanosine to two-drug combinations of these drugs. Patients with CD4 cell counts between 100 and 500 cells/mm3 without prior or <6 months of monotherapy with zidovudine or didanosine were randomized to one of four arms and observed on a follow-up basis for 48 weeks. In total, 544 patients were evaluated. In those assigned to the three-drug regimen, mean short-term (weeks 4-12) and long-term (weeks 40-48) change in CD4 cells from baseline were 49.3+/-8.1 and 65.4+/-13.4 cells/mm3, respectively; mean short-term and long-term HIV-1 RNA changes from baseline were -1.13 log10+/-0.12 and -0.73+/-0.12 copies/ml, respectively. These responses in CD4 cell counts and HIV-1 RNA levels were better in comparisons with each of the two-drug arms at all study points; however, differences were not consistently significant. Gastrointestinal side effects were experienced by 33% of patients (178 of 544), and 30% (121 of 407) receiving delavirdine experienced rash, only one case of which was severe. In this study, therapy with delavirdine + zidovudine + didanosine was safe and showed modest, but not always significant, antiviral activity and CD4 cell count benefit compared with two-drug regimens with these agents. Key

Visit-driven endpoints in randomized HIV/AIDS clinical trials: impact of missing data on treatment difference measured on summary statistics

In randomized HIV/AIDS clinical trials, CD4 lymphocyte counts and plasma HIV-1 RNA measurements are often used as endpoints. The comparison between treatment groups is mainly based on a summary measure of outcome, so-called summary statistic. Such analyses are often complicated by missing data occurring as drop-outs. For the most currently used summary statistics in these trials, we examined the impact of missing data occurring as drop-outs on test size, in order to help choosing between these statistics. A simulation of missing-data patterns was performed, using HIV-1 plasma RNA measurements as the main endpoint, to compare the effect of three plausible informative patterns, depending on treatment group, and on baseline or current plasma viral load, on eight different summary statistics. Missing data resulted in test sizes over the nominal value for the area under the curve minus baseline, the least-squares slope, the slope estimated with use of a mixed effects linear model, assuming a linear trend over the entire study, the difference between baseline and nadir, and the difference between baseline and week 24. The difference between baseline and week 8 was an acceptable summary with respect to the test size, but did not reflect accurately the durability of the effect of treatment. Two criteria appeared as the best summary statistics: the slope estimated by a mixed effects model, with a change of slope after two weeks of treatment, and to a lesser degree, the area under the curve after carrying forward the last observation.

Lamivudine in combination with zidovudine, stavudine, or didanosine in patients with HIV-1 infection. A randomized, double-blind, placebo-controlled trial. National Institute of Allergy and Infectious Disease AIDS Clinical Trials Group Protocol 306 Investigators

OBJECTIVE

To study the antiviral activity of lamivudine (3TC) plus zidovudine (ZDV), didanosine (ddl), or stavudine (d4T).

DESIGN

Randomized, placebo-controlled, partially double-blinded multicenter study.

SETTING

Adult AIDS Clinical Trials Units.

PATIENTS

Treatment-naive HIV-infected adults with 200-600x10(6) CD4 T lymphocytes/l.

INTERVENTIONS

Patients were openly randomized to a d4T or a ddl limb, then randomized in a blinded manner to receive: d4T (80 mg/day), d4T plus 3TC (300 mg/day), or ZDV (600 mg/day) plus 3TC, with matching placebos; or ddl (400 mg/day), ddl plus 3TC (300 mg/day), or ZDV (600 mg/day) plus 3TC, with matching placebos. After 24 weeks 3TC was added for patients assigned to the monotherapy arms.

MAIN OUTCOME MEASURE

The reduction in plasma HIV-1 RNA level at weeks 24 and 48.

RESULTS

Two hundred ninety-nine patients were enrolled. After 24 weeks the mean reduction in plasma HIV-1 RNA copies/ml from baseline was 0.49 log10 (d4T monotherapy) versus 1.03 log10 (d4T plus 3TC; P = 0.001), and 0.68 log10 (ddl monotherapy) versus 0.82 log10 (ddl plus 3TC; P>0.22). After 48 weeks the mean reduction was 1.08 log10 (d4T plus 3TC) versus 1.01 log10 (ZDV plus 3TC) in the d4T limb (P = 0.66), and 0.94 log10 (ddl plus 3TC) versus 0.88 log10 (ZDV plus 3TC; P = 0.70) in the ddl limb.

CONCLUSIONS

3TC added significantly to the virologic effects of d4T, but not ddl, in treatment-naive patients. 3TC plus d4T produced virologic changes comparable to those of 3TC plus ZDV. These results support the use of 3TC with either ZDV or d4 as a component of initial combination antiretroviral therapy.

Highly active antiretroviral therapy (HAART) for the treatment of infection with human immunodeficiency virus type 1

Highly active antiretroviral therapy (HAART) refers to a broad category of treatment regimens usually comprised of three or more antiretroviral drugs that, in previously untreated HIV-1-infected patients, are expected to reduce plasma virus levels below the limits of detection. Most HAART regimens include drugs from at least two of the three classes of antiretroviral therapy (nucleoside analog reverse transcriptase (RT) inhibitors, non-nucleoside analog RT inhibitors, and protease inhibitors). In deciding when to initiate antiretroviral therapy, physicians and their patients must balance the virological and immunological benefits of early treatment with the costs of drug therapy, the risk of drug side effects, and the risk of drug resistance if adherence is suboptimal. In previously untreated patients, HIV-1 replication can be suppressed indefinitely with certain HAART regimens. In previously treated patients, the benefits of HAART are often significantly diminished.

Stavudine in zidovudine (ZDV)-experienced compared with ZDV-naive patients

OBJECTIVE

To assess the effect of prior zidovudine (ZDV) use on subsequent response to stavudine (D4T)-containing regimens.

DESIGN

Analysis of data from prospective observational database.

METHODS

Patients were ZDV-experienced if they had previously received more than 90 days of ZDV and ZDV-naive if they had never received ZDV. HIV-1 RNA and CD4 cell counts were compared at 3, 6, and 12 months after initiation of D4T. Univariate and multivariate analyses were performed, adjusting for baseline HIV-1 RNA and CD4 cell count, age, sex, race, HIV transmission category, time since enrollment, and protease inhibitor use.

RESULTS

No difference was found between ZDV-experienced (n = 130) and naive (n = 98) patients in age, sex, race, transmission category, use of a concurrent protease inhibitor, or baseline CD4 cell count and HIV-1 RNA. There was no difference in the median decline in HIV-1 RNA (-1.29 log10 copies/ml for experienced patients versus -1.19 log10 copies/ml for naive patients; P = 0.39), in achieving HIV-1 RNA < 400 copies/ml at 3 months (51% versus 49%; P = 0.79) or 6 months (48% versus 56%; P = 0.33). There was no difference in CD4 cell response (+73 x 10(6)/l versus + 87 x 10(6)/l; P = 0.51). By multivariate adjustment in a repeated measures analysis, there was no significant difference in achieving undetectable HIV-1 RNA or in CD4 cell response between experienced and naive patients.

CONCLUSION

No difference in response to a D4T-containing regimen between ZDV-experienced and naive patients was found over a 1-year period. In contrast to previous trials, most patients in this study also received a protease inhibitor. These findings may be more relevant in the current era of highly active antiretroviral therapy.