Development of albumin-based nanoparticles for the delivery of abacavir

The study was designed to prepare and evaluate albumin nanoparticles containing antiviral drug abacavir sulphate. Various batches of albumin nanoparticles containing abacavir sulphate were prepared by desolvation method. The abacavir loaded particles were characterized for their yield, percentage of drug loading, surface morphology, particle size, surface charge, pattern of in vitro drug release and release mechanism studies. Drug loading ranged from 1.2 to 5.9%w/w. The mean particle size and the surface charge were 418.2nm and -40.8mV respectively. The in vitro drug release varied between 38.73 and 51.36%w/w for 24h. The n value for Korsmeyer-Peppas was 0.425 indicating Fickian type drug release. The preliminary findings indicated that albumin nanoparticles of abacavir can be prepared by desolvation method with good yield, high drug loading and sustained release.

Comparison of methods for in-house screening of HLA-B*57:01 to prevent abacavir hypersensitivity in HIV-1 care

Abacavir is a nucleoside reverse transcriptase inhibitor used as part of combination antiretroviral therapy in HIV-1-infected patients. Because this drug can cause a hypersensitivity reaction that is correlated with the presence of the HLA-B*57:01 allotype, screening for the presence of HLA-B*57:01 is recommended before abacavir initiation. Different genetic assays have been developed for HLA-B*57:01 screening, each with specific sensitivity, turnaround time and assay costs. Here, a new real-time PCR (qPCR) based analysis is described and compared to sequence specific primer PCR with capillary electrophoresis (SSP PCR CE) on 149 patient-derived samples, using sequence specific oligonucleotide hybridization combined with high resolution SSP PCR as gold standard. In addition to these PCR based methods, a complementary approach was developed using flow cytometry with an HLA-B17 specific monoclonal antibody as a pre-screening assay to diminish the number of samples for genetic testing. All three assays had a maximum sensitivity of >99. However, differences in specificity were recorded, i.e. 84.3%, 97.2% and >99% for flow cytometry, qPCR and SSP PCR CE respectively. Our data indicate that the most specific and sensitive of the compared methods is the SSP PCR CE. Flow cytometry pre-screening can substantially decrease the number of genetic tests for HLA-B*57:01 typing in a clinical setting.

Differential skeletal impact of tenofovir disoproxil fumarate in young versus old HIV-infected adults

BACKGROUND

Lower peak bone mass in early adulthood predicts subsequent fragility fractures. Antiretroviral toxicity could contribute to young HIV-infected individuals not achieving adequate peak bone mass.

OBJECTIVE

To determine if tenofovir disoproxil fumarate's (TDF) effect on bone mineral density (BMD) differs by age.

METHODS

We examined BMD data at the lumbar spine and hip from AIDS Clinical Trials Group (ACTG) A5224s and ASSERT and randomized treatment-naive studies comparing TDF/emtricitabine versus abacavir/lamivudine (with efavirenz or atazanavir/ritonavir). In this post hoc analysis, we defined the TDF effect as the difference between mean 48-week BMD per cent changes for lumbar spine and hip in individuals randomized to TDF versus abacavir. We used multivariable linear regression to compare the TDF effect in individuals younger and older than 30 years. If TDF effect by age did not differ significantly between studies, we pooled study populations. Otherwise, analyses were conducted separately within each study population.

RESULTS

Among 652 subjects, 21% were below age 30 years. The relationship between age and TDF effect significantly differed between A5224s and ASSERT (P = 0.008 for lumbar spine; P = 0.007 for hip). In A5224s, there was more bone loss with TDF at lumbar spine and hip in subjects under 30 years old versus in older subjects ( - 4.5% vs - 1.4%; P = 0.045; - 4.3% vs - 1.6%; P = 0.026, respectively). There was no significant evidence for this age-associated TDF effect in ASSERT.

CONCLUSIONS

There was heterogeneity in the observed effect of TDF on bone density in young adults compared to older adults, suggesting that further investigation is required to understand the impact of age on BMD decline with TDF.

Relaxation effect of abacavir on rat basilar arteries

BACKGROUND

The use of abacavir has been linked with increased cardiovascular risk in patients with human immunodeficiency virus infection; however, the mechanism involved remains unclear. We hypothesize that abacavir may impair endothelial function. In addition, based on the structural similarity between abacavir and adenosine, we propose that abacavir may affect vascular contractility through endogenous adenosine release or adenosine receptors in blood vessels.

METHODS

The relaxation effect of abacavir on rat basilar arteries was studied using the myograph technique. Cyclic GMP and AMP levels were measured by immunoassay. The effects of abacavir on nucleoside transporters were studied using radiolabeled nucleoside uptake experiments. Ecto-5' nucleotidase activity was determined by measuring the generation of inorganic phosphate using adenosine monophosphate as the substrate.

RESULTS

Abacavir induced the relaxation of rat basilar arteries in a concentration-dependent manner. This relaxation was abolished when endothelium was removed. In addition, the relaxation was diminished by the nitric oxide synthase inhibitor, L-NAME, the guanylyl cyclase inhibitor, ODQ, and the protein kinase G inhibitor, KT5820. Abacavir also increased the cGMP level in rat basilar arteries. Abacavir-induced relaxation was also abolished by adenosine A2 receptor blockers. However, abacavir had no effect on ecto-5' nucleotidase and nucleoside transporters. Short-term and long-term treatment of abacavir did not affect acetylcholine-induced relaxation in rat basilar arteries.

CONCLUSION

Abacavir induces acute endothelium-dependent relaxation of rat basilar arteries, probably through the activation of adenosine A2 receptors in endothelial cells, which subsequently leads to the release of nitric oxide, resulting in activation of the cyclic guanosine monophosphate/protein kinase G-dependent pathway in vascular smooth muscle cells. It is speculated that abacavir-induced cardiovascular risk may not be related to endothelial dysfunction as abacavir does not impair relaxation of blood vessels. The most likely explanation of increased cardiovascular risk may be increased platelet aggregation as suggested by other studies.

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

PURPOSE

The combination of abacavir + lamivudine (ABC+3TC) versus didanosine + stavudine (ddI+d4T), each combined with other classes of antiretrovirals (ARVs) in ARV-naive patients, was compared for the combined endpoint of time to plasma HIV RNA >50 copies/mL (at or after the 8-month visit) or death (primary endpoint) in a nested substudy of an ongoing multicenter randomized trial.

METHOD

The substudy enrolled 182 patients; mean HIV RNA and CD4+ cell counts at baseline were 5.1 log10 copies/mL and 212 cells/mm3, respectively.

RESULTS

After a median follow-up of 28 months, rates of primary endpoint were 57.2 and 67.8 per 100 person-years for the ABC+3TC and ddI+d4T groups (hazard ratio [HR]=0.81, 95% confidence interval [CI] 0.58-1.14, p=.23).

CONCLUSION

There was a trend for treatments containing ABC+3TC to be better than treatments containing ddI+d4T with respect to HIV RNA decreases, CD4+ cell count increases, and tolerability.

A randomized comparative trial of continued abacavir/lamivudine plus efavirenz or replacement with efavirenz/emtricitabine/tenofovir DF in hypercholesterolemic HIV-1 infected individuals

BACKGROUND

Drug choice and metabolic changes with antiretroviral therapy contribute to cardiovascular risk in persons with HIV-1 infection.

METHODS

A randomized, 12 week, open-label, comparative study of the impact on lipids of continuation of abacavir/lamivudine (ABC/3TC) plus efavirenz (EFV) or replacement with the single tablet regimen of EFV/emtricitabine/tenofovir DF (EFV/FTC/TDF) in hypercholesterolaemic subjects on successful antiretroviral therapy, with a 12-week extension with all subjects on EFV/FTC/TDF.

RESULTS

157 subjects received study drug, 79 switched to EFV/FTC/TDF and 78 subjects continued ABC/3TC+EFV. At Week 12, 73 subjects on ABC/3TC+EFV switched to EFV/FTC/TDF. The switch was well tolerated and no subject experienced viral rebound. Median baseline fasting total cholesterol was 6.32 mmol/L. 12 weeks following switch, the difference in the means (LSM) between treatment groups (EFV/FTC/TDF minus ABC/3TC+EFV) in total cholesterol change from baseline was -0.74 mmol/l (95% CI -1.00, -0.47, p < 0.001). The median change from baseline in total cholesterol following switch in the EFV/FTC/TDF arm was -0.86 mmol/l (p < 0.001) compared with +0.01 mmol/l (p = 0.45) in the continuation arm at Week 12. Significant (p < 0.001) differences between treatment groups following switch were seen for all lipid fractions from baseline to Week 12: LDL cholesterol (-0.47 mmol/L [-0.70, -0.25]), HDL cholesterol (-0.15 mmol/L [-0.21, -0.08]), triglycerides (-0.43 mmol/L [-0.75, -0.11]), and non HDL cholesterol (-0.56 mmol/L [-0.80, -0.31]). In the extension phase, similar declines in total cholesterol were observed with a median change from Week 12 to Week 24 of -0.73 mmol/L (p < 0.001).

CONCLUSIONS

Switching from ABC/3TC+EFV to EFV/FTC/TDF in persons with hypercholesterolemia maintains virological control and significantly improves key lipid parameters.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00615810.

Quadruple-Drug Induction HAART in Advanced HIV Infection

A randomized controlled study exploring an induction-maintenance strategy was performed with a quadruple-drug regimen: zidovudine/lamivudine/abacavir/nevirapine. The study was prematurely interrupted due to the high proportion of adverse events. The median time on protocol-defined therapy was 110 days; 13/28 (46%) patients interrupted therapy and 2/6 tested patients selected praecox viral mutants. Despite this, we observed a significant (p </= .001) increment of CD4. The theoretical advantages of induction-maintenance strategies are tempered by an increased risk of adverse experiences.

Once-Daily Abacavir/Lamivudine/Zidovudine plus Tenofovir for the Treatment of HIV-1 Infection in Antiretroviral-NaïveSubjects: A 48-Week Pilot Study

PURPOSE

To assess the safety and efficacy of a 4-drug, 3-tablet, once-daily (qd) regimen consisting of abacavir/lamivudine/zidovudine (ABC/3TC/ZDV; 2 tablets) and tenofovir (TDF) in antiretroviral-naïve patients with plasma HIV-1 RNA 30,000 copies/mL at 48 weeks.

METHOD

All participants received ABC/3TC/ZDV (300/150/300 mg) and TDF (300 mg) qd in this pilot, open-label, multicenter study. Intent-to-treat (ITT) analyses were conducted to evaluate virologic and immunologic efficacy.

RESULTS

Of the 123 participants enrolled, 52 (42%) prematurely discontinued study for adverse events (14), were lost to follow-up (13), had virologic nonresponse (12), and withdrew for other reasons (13). At week 48, by ITT missing=failure analysis, 41% (51/123) and 51% (63/123) of participants had plasma HIV-1 RNA <50 copies/mL and <400 copies/mL, respectively; by ITT-observed analysis, 75% (51/68) and 93% (63/68) had plasma HIV-1 RNA <50 copies/mL and <400 copies/mL, respectively; 11% (14/123) met virologic nonresponse criteria. Median week 48 change in CD4+ cell count from baseline was +127 cells/mm3. Median week 48 changes from baseline for fasting lipids were as follows: cholesterol (-9 mg/dL), HDL (+1 mg/dL), LDL (-9 mg/dL), and triglycerides (-4 mg/dL).

CONCLUSION

A high rate of premature discontinuations contributed to the overall suboptimal virologic response to ABC/3TC/ZDV+TDF qd; however, the regimen was not associated with high rates of virologic failure previously observed with TDF+ABC/3TC.

48-week efficacy and safety of dolutegravir relative to commonly used third agents in treatment-naive HIV-1-infected patients: a systematic review and network meta-analysis

BACKGROUND

A network meta-analysis can provide estimates of relative efficacy for treatments not directly studied in head-to-head randomized controlled trials. We estimated the relative efficacy and safety of dolutegravir (DTG) versus third agents currently recommended by guidelines, including ritonavir-boosted atazanavir (ATV/r), ritonavir-boosted darunavir (DRV/r), efavirenz (EFV), cobicistat-boosted elvitegravir (EVG/c), ritonavir-boosted lopinavir (LPV/r), raltegravir (RAL), and rilpivirine (RPV), in treatment-naive HIV-1-infected patients.

METHODS

A systematic review of published literature was conducted to identify phase 3/4 randomized controlled clinical trials (up to August 2013) including at least one third agent of interest in combination with a backbone nucleoside reverse transcriptase inhibitor (NRTI) regimen. Bayesian fixed-effect network meta-analysis models adjusting for the type of nucleoside reverse transcriptase inhibitor backbone (tenofovir disoproxil fumarate/emtricitabine [TDF/FTC] or abacavir/lamivudine [ABC/3TC]) were used to evaluate week 48 efficacy (HIV-RNA suppression to <50 copies/mL and change in CD4+ cells/µL) and safety (lipid changes, adverse events, and discontinuations due to adverse events) of DTG relative to all other treatments. Sensitivity analyses assessing the impact of NRTI treatment adjustment and random-effects models were performed.

RESULTS

Thirty-one studies including 17,000 patients were combined in the analysis. Adjusting for the effect of NRTI backbone, treatment with DTG resulted in significantly higher odds of virologic suppression (HIV RNA<50 copies/mL) and increase in CD4+ cells/µL versus ATV/r, DRV/r, EFV, LPV/r, and RPV. Dolutegravir had better or equivalent changes in total cholesterol, LDL, triglycerides, and lower odds of adverse events and discontinuation due to adverse events compared to all treatments. Random-effects and unadjusted models resulted in similar conclusions.

CONCLUSION

Three clinical trials of DTG have demonstrated comparable or superior efficacy and safety to DRV, RAL, and EFV in HIV-1-infected treatment-naive patients. This network meta-analysis suggests DTG is also favorable or comparable to other commonly used third agents (ATV/r, LPV/r, RPV, and EVG/c).

Changes in proteinuria and albuminuria with initiation of antiretroviral therapy: data from a randomized trial comparing tenofovir disoproxil fumarate/emtricitabine versus abacavir/lamivudine

BACKGROUND

Antiretroviral therapy (ART) is associated with improved kidney function; however, the nucleotide reverse transcriptase inhibitor (NRTI) tenofovir disoproxil fumarate (TDF) has been associated with decreased kidney function and proteinuria.

METHODS

We examined changes in urine protein:creatinine (UPCR) and urine albumin:creatinine (UACR) ratios in 245 ART-naive participants in A5202 randomized in a substudy to blinded NRTI (abacavir/lamivudine, ABC/3TC, n = 124 or TDF/emtricitabine, TDF/FTC, n = 121) with open-label protease inhibitor (PI) atazanavir/ritonavir or nonnucleoside reverse transcriptase inhibitor (NNRTI) efavirenz.

RESULTS

At baseline, 18% of participants had clinically significant proteinuria (UPCR ≥200 mg/g), and 11% had clinically significant albuminuria (UACR ≥30 mg/g). The prevalence of clinically significant proteinuria and albuminuria decreased from baseline to week 96 in all treatment groups. In intention-to-treat analyses, there was a significant effect of NRTI component on fold change in UPCR (P = 0.011) and UACR (P = 0.018) from baseline to week 96, with greater improvements in participants randomized to ABC/3TC. There was no significant effect of NNRTI/PI component on fold change in UPCR (P = 0.23) or UACR (P = 0.88), and no significant interactions between NRTI and NNRTI/PI components.

CONCLUSIONS

In this prespecified secondary analysis, ART initiation was associated with improvements in proteinuria and albuminuria, with significantly greater improvements in participants randomized to ABC/3TC versus TDF/FTC. These are the first data from a randomized trial to suggest that initiation of TDF/FTC may not be associated with the same degree of improvement in proteinuria and albuminuria that have been reported with other regimens. Future studies should consider the long-term clinical significance of these findings.

A novel vaginal drug delivery system: anti-HIV bioadhesive film containing abacavir

Women are very much susceptible for acquired immunodeficiency syndrome (AIDS) and other sexually transmitted diseases (STDs), mainly due to unprotected heterosexual vaginal intercourse and for some other social and economical disadvantages. Our aim was to formulate and optimize vaginal film of abacavir, a potent nucleoside reverse transcriptase inhibitor, for the treatment of AIDS and HIV. Abacavir films were prepared by solvent evaporation method using sodium alginate (Na-alginate) as the main polymer, Hydroxypropyl Methylcellulose E 15 (HPMC E 15) as the copolymer and glycerol as a humectant. Abacavir sulphate (ABC) was used here as a drug. Films were optimized for various physicochemical parameters such as tensile strength, % elongation at break, swelling capacity, drug content (mg/cm(2)), thickness, folding endurance, bioadhesion, pH, moisture content and SEM. Drug polymer interaction was studied by FTIR Spectra. The drug release study was accomplished in dissolution apparatus. In vivo study was also carried out. This newly formed film was one kind of sustain release type and can be considered as a novel drug carrier system for the treatment of AIDS and other STDs. It was suitable for local as well as systemic effect. The films showed good physicochemical property with good aesthetic appeal.

Recent advances in rilpivirine: new data and promising treatment option

The usefulness of every antiretroviral drug in the clinical setting should be continuously evaluated, since registration studies may not adequately reflect real-world patient populations. Rilpivirine was developed in an effort to generate patient-tailored drugs with high convenience and minimal side effects. By now, rilpivirine is currently licensed for use with other antiretroviral agents, and as a single agent or a single-tablet regimen with tenofovir and emtricitabine , in antiretroviral-naive, HIV-1-infected adults with < 100,000 HIV-1 RNA copies/ml because of a higher rate of virological failure above this level. However, after its introduction several questions remained to be elucidated, such as the efficacy of rilpivirine with abacavir/lamivudine, or its use in switching strategies, a useful alternative for patients with toxicity or intolerance. Cumulative data suggest the efficacy and safety of the combination of abacavir/lamivudine plus rilpivirine in the clinical setting, and an increasing number of patients received rilpivirine after protease inhibitor, efavirenz, or nevirapine-based therapy without compromising rilpivirine exposure after the change. Moreover, rilpivirine is a substrate and weak inducer of the CYP3A4, but there are no significant pharmacokinetic interactions with new anti-hepatitis C compounds such as telaprevir, simeprevir, daclatasvir, ledipasvir, and sofosbuvir, an important issue for a drug with low risk of hepatoxicity. As a new and promising strategy, rilpivirine has been evaluated with darunavir and dolutegravir in dual therapies, without need of dose adjustment and with adequate preliminary data. Therefore, to date, new data on rilpivirine confirm the good results observed in the clinical trials.

Moving away from Ritonavir, Abacavir, Tenofovir, and Efavirenz (RATE)--agents that concern prescribers and patients: a feasibility study and call for a trial

Objectives

Regimens sparing RATE (ritonavir, abacavir, tenofovir, efavirienz) agents might have better long-term safety. We conducted a feasibility exercise to assess the potential for a randomised trial evaluating RATE-sparing regimens.

Design

Observational.

Methods

We first calculated RATE-sparing options available to an average patient receiving RATE agents. We reviewed treatment history and all resistance assays from patients attending the St. Vincent’s Hospital (Sydney) clinic and receiving ≥2 RATE agents (n = 120). A viable RATE-sparing regimen with 2 or 3 fully-active agents was constructed from the following six ‘safer’ agents: rilpivirine or etravirine; atazanavir; raltegravir; maraviroc; and lamivudine. Activity for each drug was predicted as 1 (full-activity), 0.5 or 0 (no activity) using the Stanford mutation database. The utility of maraviroc was calculated assuming both maraviroc activity and inactivity where unknown. The analysis was restricted to regimens for which supporting evidence was identified in the literature or conference proceedings. Finally, we calculated the proportion of patients in the nationally representative Australian HIV Observational Database (AHOD) cohort receiving ≥2 RATE agents (n = 1473) to measure the potential population-level uptake of RATE-sparing agents.

Results

Assuming full maraviroc activity, 117(97.5%) and 107(89.2%) individuals had at least one option with 2 or 3 active RATE-sparing agents, respectively. Assuming no maraviroc activity this decreased to 113(94.2%) and 104(86.7%), respectively. In AHOD, 837(56.8%) patients were receiving ≥2 RATE agents.

Conclusion

Feasible treatment switch options sparing RATE agents exist for the majority of patients. Understanding the pros and cons of switching stable patients onto new RATE-sparing regimens requires evidence derived from randomised controlled trials.

Fixed dose combination abacavir/lamivudine in the treatment of HIV-1 infection

The fixed dose combination of abacavir with lamivudine represents a new treatment option for patients infected with HIV. Fixed dose combination abacavir/lamivudine has the convenience of one pill and once-daily dosing. It achieves comparable suppression of plasma HIV RNA with the pill's individual components dosed twice daily and with thymidine analogs combined with lamivudine. The combination is well tolerated, with the potential advantages of less lipoatrophy and fewer metabolic perturbations. However, the abacavir component may cause hypersensitivity reactions, which are reported in up to 8% of patients, and are potentially life threatening. Fixed dose combination abacavir/lamivudine should be considered as a viable treatment option for HIV-infected patients, particularly for those who have otherwise limited nucleoside reverse transcriptase inhibitor choices.

[Future direction of pharmacogenomics: identification of genes associated with risk of adverse drug reactions using genome-wide association study]

Drug-induced skin rash characterized by an acute inflammatory reaction of skin and mucous membranes is dose-independent, unpredictable, and sometimes life-threatening. In recent years, the U.S. Food and Drug Administration (FDA) has recommended genotyping of polymorphisms in the human leukocyte antigen (HLA) prior to drug administration for the avoidance of severe skin rash induced by drugs, such as abacavir and carbamazepine. A genome-wide association study (GWAS) is useful for the identification of genomic biomarkers that can predict the efficacy or risk of toxicity of various drugs. We identified novel susceptibility loci associated with the risk of a skin rash induced by nevirapine and carbamazepine in Thai and Japanese populations, respectively, through case-control GWAS with high-throughput single-nucleotide polymorphism (SNP) genotyping technology. In order to apply the genomic biomarkers to clinical therapeutics, prospective clinical trials will be necessary for the evaluation of an intervention based on genetic tests.

[The efficacy and safety of a therapy regimen including raltegravir and a fixed dose combination of lamivudine and abacavir in previously rifabutin-treated patients with tuberculosis and HIV infection]

AIM

To evaluate the efficiency and safety of using raltegravir (RAL) twice daily in conjunction with a once-daily fixed dose combination of abacavir (ABC)/lamivudine (3TC) in patients with HIV infection and active tuberculosis who have not previously received antiretroviral therapy (ART) and have taken rifabutin as antituberculosis therapy (ATT).

SUBJECTS AND METHODS

The efficiency of ART was evaluated in 28 patients from a change in HIV RNA levels and from an increase in CD4+ lymphocyte counts during 48-week treatment that had been completed by 15 (53.6%) patients. The main reason for therapy discontinuation was that the patients returned to the use psychoactive agents.

RESULTS

After 24 and 48 weeks of ART, the level of HIV RNA reached the undetectable values (less than 50 copies/ml) in 81.25 and 75% of the patients, respectively (according to an analysis including the patients who had completed the study in conformity with the requirements of the protocol). In only 2 patients, the virological therapy proved to be ineffective, which was likely to be associated with noncompliance with drug therapy. Following 24- and 48-week therapy, the increase in median CD4+ lymphocyte counts was 70 and 208.5 per μl, respectively. The concurrent use of ART and ATT caused positive changes in the lung skiagraphic pattern in 92.9% of the patients and complete resolution of lung tissue infiltration in 71.4%. Mixed infection ended in a fatal outcome caused by a progressive tuberculous process in 3 (10.7%) patients, in 2 of them within the first 8 weeks of treatment. The concomitant use of ATT including rifabutin and an ART (RAL + ABC/3TC) regimen was safe since one patient was noted to have a RAL-related adverse event (AE) (an allergic reaction) and caused the patient to discontinue therapy. ATT was not discontinued because of AE in any case.

CONCLUSION

The ART regimen containing RAL and a fixed dose combination of ABC/3TC for adult patients with tuberculosis concurrent with HIV infection who are on combined therapy using rifabutin for tuberculosis may be recommended for the treatment of this category of patients.

High rate of HIV resuppression after viral failure on first-line antiretroviral therapy in the absence of switch to second-line therapy

In a randomized comparison of nevirapine or abacavir with zidovudine plus lamivudine, routine viral load monitoring was not performed, yet 27% of individuals with viral failure at week 48 experienced resuppression by week 96 without switching. This supports World Health Organization recommendations that suspected viral failure should trigger adherence counseling and repeat measurement before a treatment switch is considered.

Impact of anesthetics on 3'-[18F]fluoro-3'-deoxythymidine ([18F]FLT) uptake in animal models of cancer and inflammation

The aim of this study was to evaluate the impact of different anesthetics on 3'-[18F]fluoro-3'-deoxythymidine ([18F]FLT) uptake in carcinomas and arthritic ankles. To determine the amount of [18F]FLT uptake in subcutaneous CT26 colon carcinomas or arthritic ankles, spontaneously room air/medical air-breathing mice were anesthetized with isoflurane, a combination of medetomidine/midazolam, or ketamine/xylazine. Mice were kept conscious or anesthetized during [18F]FLT uptake before the 10-minute static positron emission tomographic (PET) investigations. [18F]FLT uptake in CT26 colon carcinomas and arthritic ankles was calculated by drawing regions of interest. We detected a significantly reduced (4.4 ± 0.9 %ID/cm3) [18F]FLT uptake in the carcinomas of ketamine/xylazine-anesthetized mice compared to the [18F]FLT-uptake in carcinomas of medetomidine/midazolam- (7.0 ± 1.5 %ID/cm3) or isoflurane-anesthetized mice (6.4 ± 1.5 %ID/cm3), whereas no significant differences were observed in arthritic ankles regardless of whether mice were anesthetized or conscious during tracer uptake. The time-activity curves of carcinomas and arthritic ankles yielded diverse [18F]FLT accumulation related to the used anesthetics. [18F]FLT uptake dynamics are different in arthritic ankles and carcinoma, and the magnitude and pharmacokinetics of [18F]FLT uptake are sensitive to anesthetics. Thus, for preclinical in vivo [18F]FLT PET studies in experimental tumor or inflammation models, we recommend the use of isoflurane anesthesia as it yields a stable tracer uptake and is easy to handle.

SWIFT: prospective 48-week study to evaluate efficacy and safety of switching to emtricitabine/tenofovir from lamivudine/abacavir in virologically suppressed HIV-1 infected patients on a boosted protease inhibitor containing antiretroviral regimen

BACKGROUND

In the United States, emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) is a preferred nucleoside reverse transcriptase inhibitor (NRTI) backbone with lamivudine/abacavir (3TC/ABC) as a commonly used alternative. For patients infected with human immunodeficiency virus (HIV-1) virologically suppressed on a boosted protease inhibitor (PI) + 3TC/ABC regimen, the merits of switching to FTC/TDF as the NRTI backbone are unknown.

METHODS

SWIFT was a prospective, randomized, open-label 48-week study to evaluate efficacy and safety of switching to FTC/TDF. Subjects receiving 3TC/ABC + PI + ritonavir (RTV) with HIV-1 RNA < 200 c/mL ≥3 months were randomized to continue 3TC/ABC or switch to FTC/TDF. The primary endpoint was time to loss of virologic response (TLOVR) with noninferiority measured by delta of 12%. Virologic failure (VF) was defined as confirmed rebound or the last HIV-1 RNA measurement on study drug ≥200 c/mL.

RESULTS

In total, 311 subjects were treated in this study (155 to PI + RTV + FTC/TDF, 156 to PI + RTV + 3TC/ABC). Baseline characteristics were similar between the arms: 85% male, 28% black, median age, 46 years; and median CD4 532 cells/mm(3). By TLOVR through week 48, switching to FTC/TDF was noninferior compared to continued 3TC/ABC (86.4% vs 83.3%, treatment difference 3.0% (95% confidence interval, -5.1% to 11.2%). Fewer subjects on FTC/TDF experienced VF (3 vs 11; P = .034). FTC/TDF showed greater declines in fasting low-density lipoproteins (LDL), total cholesterol (TC), and triglycerides (TG) with significant declines in LDL and TC beginning at week 12 with no TC/HDL ratio change. Switching to FTC/TDF showed improved NCEP thresholds for TC and TG and improved 10-year Framingham TC calculated scores. Decreased estimated glomerular filtration rate [corrected] (eGFR) was observed in both arms with a larger decrease in the FTC/TDF arm.

CONCLUSIONS

Switching to FTC/TDF from 3TC/ABC maintained virologic suppression, had fewer VFs, improved lipid parameters and Framingham scores but decreased eGFR. CLINICALTRIALS.GOV IDENTIFIER: NCT00724711.

Abacavir Pharmacokinetics in Human Immunodeficiency Virus-Infected Children Ranging in Age From 1 Month to 16 Years: A Population Analysis

Abacavir pharmacokinetics was studied in 105 children by a population approach performed with NONMEM. A 1-compartment open model with linear absorption and elimination adequately described the data. Typical population estimates (percent interindividual variability) of absorption rate constant, apparent distribution volume, and apparent plasma clearance were 1.79 h(-1) (58%), 42.9 L (53%), and 24.3 L/h (30%), respectively. Apparent plasma clearance was positively related to body weight. Individual Bayesian estimates of apparent plasma clearance were used to calculate individual abacavir area under the concentration curve (AUC). For the current weight-based regimen, abacavir exposure was found to be constant throughout the age range of the study, with an overall mean AUC value of 8.5 +/- 2.5 mg x h/L, which is slightly greater than the mean AUC value reported in adults. This study confirms the relevance of the current weight-based abacavir dosage regimen in pediatric patients.