Antiretroviral treatment of HIV infection: Swedish recommendations 2007

Longitudinal decline of plasma neurofilament light levels after antiretroviral initiation in people living with HIV

BACKGROUND

This retrospective follow-up study aims to investigate the dynamic longitudinal change of plasma neurofilament light (NfL) levels after antiretroviral therapy (ART) initiation in a cohort of people living with human immunodeficiency virus (HIV) (PWH).

METHODS

We tested a convenience sample of 116 patients from the NORTHIV study. Plasma NfL levels-measured using Single molecule array (Simoa) technology-as well as other laboratory parameters were collected at baseline, weeks 4, 48, 96, and 144. Linear mixed-effects models were estimated to evaluate longitudinal change over time. Baseline CD4⁺ T-cell levels, CDC classification, and HIV RNA levels were considered. Models were adjusted by age, sex, treatment regimen, and baseline serum creatinine levels.

RESULTS

Plasma NfL levels were higher at baseline and also declined faster during the follow-up for participants with CD4⁺ count <100 cells/µl compared with >100 cells/µl. No significant difference was found between the CD4⁺ strata 100-199 and 200-499/µl. Participants with CDC classification stages B and C had higher levels of plasma NfL at baseline, as well as faster decline compared with participants with stage A. No significant main effects or change over time was found in baseline HIV RNA levels, treatment regimen, or sex.

CONCLUSION

Plasma NfL is a sensitive biomarker to assess ongoing central nervous system injury in PWH. Plasma NfL concentrations decline relatively fast following ART initiation and then stabilize after 48 weeks. Plasma NfL concentrations are associated with CD4⁺ count and stage of HIV disease. No correlations were seen with different ART regimens.

Bilirubin-a potential marker of drug exposure in atazanavir-based antiretroviral therapy

The objective of this work was to examine the atazanavir-bilirubin relationship using a population-based approach and to assess the possible application of bilirubin as a readily available marker of atazanavir exposure. A model of atazanavir exposure and its concentration-dependent effect on bilirubin levels was developed based on 200 atazanavir and 361 bilirubin samples from 82 patients receiving atazanavir in the NORTHIV trial. The pharmacokinetics was adequately described by a one-compartment model with first-order absorption and lag-time. The maximum inhibition of bilirubin elimination rate constant (I(max)) was estimated at 91% (95% CI, 87-94) and the atazanavir concentration resulting in half of I(max) (IC50) was 0.30 μmol/L (95% CI, 0.24-0.37). At an atazanavir/ritonavir dose of 300/100 mg given once daily, the bilirubin half-life was on average increased from 1.6 to 8.1 h. A nomogram, which can be used to indicate suboptimal atazanavir exposure and non-adherence, was constructed based on model simulations.

Normal Range of CD4 Cell Counts and Temporal Changes in Two HIVNegative Malawian Populations

Longitudinal studies were carried out to determine trends in CD4 cell counts over a four year period in healthy HIV-negative adults in a rural (134 individuals) and an urban (80 individuals) site in Malawi, using TruCountTM and FACScountTM platforms. At baseline, median counts and 95% ranges were 890 (359-1954) cells per microlitre (μl) and 725 (114-1074) cells/μl respectively. 1.5% and 6% respectively had baseline counts below 350 cells/μl and 1.5% and 2.5% below 250 cells per μl. Transient dips to below 250 cells/μl were observed in seven individuals, with two individuals having persistently low CD4 counts over more than one year. Women and individuals from the urban site were significantly more likely to have "low CD4 count" (< 500 cells/μl) even when adjusted for other factors. In common with neighbouring countries, HIV-negative populations in Malawi have CD4 counts considerably lower than European reference ranges, and healthy individuals may have persistently or transiently low counts. Within Malawi, ranges differ according to the selected population.

In silico prediction of efavirenz and rifampicin drug-drug interaction considering weight and CYP2B6 phenotype

AIMS

This study aimed to test whether a pharmacokinetic simulation model could extrapolate nonclinical drug data to predict human efavirenz exposure after single and continuous dosing as well as the effects of concomitant rifampicin and further to evaluate the weight-based dosage recommendations used to counteract the rifampicin-efavirenz interaction.

METHODS

Efavirenz pharmacokinetics were simulated using a physiologically based pharmacokinetic model implemented in the Simcyp™ population-based simulator. Physicochemical and metabolism data obtained from the literature were used as input for prediction of pharmacokinetic parameters. The model was used to simulate the effects of rifampicin on efavirenz pharmacokinetics in 400 virtual patients, taking into account bodyweight and CYP2B6 phenotype.

RESULTS

Apart from the absorption phase, the simulation model predicted efavirenz concentration-time profiles reasonably well, with close agreement with clinical data. The simulated effects of rifampicin co-administration on efavirenz treatment showed only a minor decrease of 16% (95% confidence interval 13-19) in efavirenz area under the concentration-time curve, of the same magnitude as what has been clinically observed (22%). Efavirenz exposure depended on CYP2B6 phenotype and bodyweight. Increasing the efavirenz dose during concomitant rifampicin was predicted to be most successful in patients over 50 kg regardless of CYP2B6 status.

CONCLUSIONS

Our findings, although based on a simulation approach using limited in vitro data, support the current recommendations for using a 50 kg bodyweight cut-off for efavirenz dose increment when co-treating with rifampicin.

Differential effects of efavirenz, lopinavir/r, and atazanavir/r on the initial viral decay rate in treatment naïve HIV-1-infected patients

Initial viral decay rate may be useful when comparing the relative potency of antiretroviral regimens. Two hundred twenty-seven ART-naïve patients were randomized to receive efavirenz (EFV) (n = 74), lopinavir/ritonavir (LPV/r) (n = 77), or atazanavir/ritonavir (ATV/r) (n = 79) in combination with two NRTIs. The most frequently used NRTI combinations in the EFV and ATV/r groups were the nonthymidine analogues tenofovir and emtricitabine or lamivudine (70% and 68%, respectively) and, in the LPV/r group, lamivudine and the thymidine analogue zidovudine (89%). HIV-1 RNA was monitored during the first 28 days after treatment initiation. Phase 1 and 2 decay rate was estimated in a subset of 157 patients by RNA decrease from days 0 to 7, and days 14 to 28. One-way ANOVA and subsequent Tukey's post hoc tests were used for groupwise comparisons. Mean (95% CI) HIV-1 RNA reductions from days 0 to 28 were 2.59 (2.45-2.73), 2.42 (2.27-2.57), and 2.13 (2.01-2.25) log(10) copies/ml for the EFV-, LPV/r-, and ATV/r-based treatment groups, respectively, with a significantly larger decrease in the EFV-based group at all time points compared with ATV/r (p < 0.0001), and with LPV/r at days 7-21 (p < 0.0001-0.03). LPV/r gave a greater RNA decrease compared with ATV/r from day 14 (p = 0.02). Phase 1 decay rate was significantly higher in the EFV group compared with LPV/r (p = 0.003) or ATV/r (p < 0.0001). No difference was found in phase 2 decrease. EFV-based treatment gave a more rapid decline in HIV-1 RNA than did either of the boosted protease inhibitor-based regimens. The observed differences may reflect different inherent regimen potencies.

Medical resource utilization and cost of HIV-related care in the highly active antiretroviral therapy era at a University Clinic in Sweden

INTRODUCTION

Little is known regarding healthcare costs for HIV/AIDS patients in the era of highly active antiretroviral therapy (HAART) and subgroups of patients according to the severity and progression of HIV infection in Sweden. The objective of this study is therefore to describe the direct medical resource use and cost of healthcare for HIV patients at a university clinic in Sweden.

METHODS

A patient registry database for HIV treatment at the Department of Infectious Diseases, Sahlgrenska University Hospital, between 2000 and 2005 provided information on patient characteristics, antiretroviral drugs and dosages, tests and diagnostic procedures, outpatient visits and inpatient stays. The review used publicly available unit costs with a county council perspective, expressed in 2006 Euros.

RESULTS

Two hundred and eighty-five patients with a mean age of 38 years in 2000 (64% men) were followed for 1368 patient-years. They had a mean (median) of 6.3 (0) inpatient days, 4.1 (3.7) physician visits, 4.2 (3.8) nurse visits, 2.6 (0.7) counsellor visits and 11.5 (7.7) tests and diagnostic procedures per patient-year. Only 12 deaths were recorded during the study period, and the proportion of treated patients with successful treatment (HIV-RNA < 50 copies/mL) increased from 74% to 92% during the period. The mean cost per patient-month amounted to €1069. The main cost driver was HIV drugs (51%), followed by inpatient stays (including hospitalizations for opportunistic infections; 22%), outpatient physician, nurse or therapist visits (19%) and diagnostics and tests (7%). All non-drug costs increased with a decreasing CD4 cell count.

CONCLUSIONS

Overall, approximately half of the direct costs of HIV treatment were not related to antiretroviral treatment. The non-antiretroviral costs were inversely correlated with HIV-induced immune deficiency.

Prevalence of drug resistance and importance of viral load measurements in Honduran HIV-infected patients failing antiretroviral treatment

OBJECTIVE

The Honduran HIV/AIDS Program began to scale up access to HIV therapy in 2002. Up to May 2008, more than 6000 patients received combination antiretroviral therapy (cART). As HIV drug resistance is the major obstacle for effective treatment, the purpose of this study was to assess the prevalence of antiretroviral drug resistance in Honduran HIV-1-infected individuals.

METHODS

We collected samples from 138 individuals (97 adults and 41 children) on cART with virological, immunological or clinical signs of treatment failure. HIV-1 pol sequences were obtained using an in-house method. Resistance mutations were identified according to the 2007 International AIDS Society (IAS)-USA list and predicted susceptibility to cART was scored using the ANRS algorithm.

RESULTS

Resistance mutations were detected in 112 patients (81%), 74% in adults and 98% in children. Triple-, dual- and single-class drug resistance was documented in 27%, 43% and 11% of the study subjects, respectively. Multiple logistic regression showed that resistance was independently associated with type of treatment failure [virological failure (odds ratio (OR) = 1) vs. immunological failure (OR = 0.11; 95% confidence interval (CI) 0.030-0.43) vs. clinical failure (OR = 0.037; 95% CI 0.0063-0.22)], route of transmission (OR = 42.8; 95% CI 3.73-491), and years on therapy (OR = 1.81; 95% CI 1.11-2.93).

CONCLUSION

The prevalence of antiretroviral resistance was high in Honduran HIV-infected patients with signs of treatment failure. A majority of study subjects showed dual- or triple-class resistance to nucleoside reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors and protease inhibitors. Virologically defined treatment failure was a strong predictor of resistance, indicating that viral load testing is needed to correctly identify patients with treatment failure attributable to resistance.

Etravirine

Etravirine is a next-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that demonstrates potent in vitro activity against wild-type strains of HIV type 1 (HIV-1), as well as against numerous strains resistant to available NNRTIs. Furthermore, the potential for resistance to etravirine developing appears to be lower than for first-generation NNRTIs. In treatment-experienced patients infected with HIV-1 with NNRTI resistance, HIV-1 RNA levels of <50 copies/mL (primary endpoint) and <400 copies/mL were achieved by a significantly greater proportion of patients receiving etravirine 200 mg twice daily plus background therapy (BT) than placebo plus BT, according to the planned pooled and individual 24-week analyses of two large, well designed, continuing phase III trials (DUET-1 and DUET-2). In the pooled 24-week analysis, patients receiving etravirine plus BT achieved a significantly greater mean reduction in viral load from baseline and a significantly greater mean increase in CD4+ cell counts from baseline than patients receiving placebo plus BT. The pooled and individual findings of the DUET studies at 48 weeks indicate that the efficacy of etravirine is maintained with regard to these endpoints. In the DUET studies, etravirine was generally well tolerated in treatment-experienced patients infected with HIV-1, with a tolerability profile generally similar to that of placebo. Adverse events were mostly of mild or moderate severity.

The cost-effectiveness of HLA-B*5701 genetic screening to guide initial antiretroviral therapy for HIV

OBJECTIVE

To evaluate the clinical impact and cost-effectiveness of HLA-B*5701 testing to guide selection of first-line HIV regimens in the United States.

DESIGN

Cost-effectiveness analysis using a simulation model of HIV disease. The prevalence of HLA-B*5701 and the probabilities of confirmed and unconfirmed severe systemic hypersensitivity reaction among patients taking abacavir testing HLA-B*5701 positive and negative were from the Prospective Randomized Evaluation of DNA Screening in a Clinical Trial study. The monthly costs of abacavir-based and tenofovir-based regimens were $1135 and $1139, respectively; similar virologic efficacy was assumed and this assumption was varied in sensitivity analysis.

PATIENTS

Simulated cohort of patients initiating HIV therapy.

INTERVENTIONS

The interventions are first-line abacavir, lamivudine, and efavirenz without pretreatment HLA-B*5701 testing; the same regimen with HLA-B*5701 testing; and first-line tenofovir, emtricitabine, and efavirenz.

MAIN OUTCOME MEASURES

Quality-adjusted life years and lifetime medical costs discounted at 3% per annum, cost-effectiveness ratios ($/QALY).

RESULTS

Abacavir-based treatment without HLA-B*5701 testing resulted in a projected 30.93 years life expectancy, 16.23 discounted quality-adjusted life years, and $472,200 discounted lifetime cost per person. HLA-B*5701 testing added 0.04 quality-adjusted months at an incremental cost of $110, resulting in a cost-effectiveness ratio of $36,700/QALY compared with no testing. Initiating treatment with a tenofovir-based regimen increased costs without improving quality-adjusted life expectancy. HLA-B*5701 testing remained the preferred strategy only if abacavir-based treatment had equal efficacy and cost less per month than tenofovir-based treatment. Results were also sensitive to the cost of HLA-B*5701 testing and the prevalence of HLA-B*5701.

CONCLUSION

Pharmacogenetic testing for HLA-B*5701 is cost-effective only if abacavir-based treatment is as effective and costs less than tenofovir-based treatment.

Prophylaxis and treatment of HIV-1 infection in pregnancy: Swedish Recommendations 2007

Prophylaxis and treatment with antiretroviral drugs, a consequent low viral load, and the use of elective Caesarean section, are factors that radically decrease the risk of HIV transmission from mother to child during pregnancy and delivery. The availability of new antiretroviral drugs, updated general treatment guidelines and increasing knowledge of the importance of drug resistance, have necessitated recurrent revisions of the recommendations for 'Prophylaxis and treatment of HIV-1 infection in pregnancy'. For these reasons, The Swedish Reference Group for Antiviral Therapy (RAV) has, at an expert meeting on May 4, 2007, once more updated the treatment recommendations of 1999, 2002 and 2005, which were defined in cooperation with the Swedish Medical Products Agency (Läkemedelsverket). This new text takes the recently updated general HIV treatment recommendations into account. Furthermore, the very low risk of HIV transmission when the mother is treated with combination antiretroviral therapy, has undetectable levels of viraemia and no obstetric risk factors, has been considered in the recommendations concerning the mode of delivery. Finally, the recommendations for monitoring of infants born to HIV-infected mothers have been modified. The recommendations are evidence graded in accordance with the Oxford Centre for Evidence Based Medicine, 2001 (see http://www.cebm.net/levels_of_evidence.asp#levels).

Pharmacogenetic information derived from analysis of HLA alleles

A large amount of pharmacogenetic information has, in particular, accumulated on the association between human leukocyte antigen (HLA) alleles and hypersensitivity to certain drugs. Prospective HLA typing has dramatically reduced the risk of abacavir hypersensitivity because of its strong association with HLA-B*5701. Significant predisposition to nevirapine hypersensitivity has been reported in Caucasian Australians harboring HLA-DRB1*0101 with high CD4+ T-cell counts, and Sardinians and Japanese harboring HLA-Cw8. A strong association between carbamazepine hypersensitivity and HLA-B*1502 has been reported in Han Chinese. Most Han Chinese individuals with allopurinol-induced severe cutaneous adverse reactions are positive for HLA-B*5801. HLA typing can stratify risk of hypersensitivity to certain drugs and allow personalized treatment, although the patients should be monitored closely even if they are negative for HLA alleles associated with hypersensitivity.

P-glycoprotein-mediated active efflux of the anti-HIV1 nucleoside abacavir limits cellular accumulation and brain distribution

P-glycoprotein (P-gp)-mediated efflux at the blood-brain barrier has been implicated in limiting the brain distribution of many anti-HIV1 drugs, primarily protease inhibitors, resulting in suboptimal concentrations in this important sanctuary site. The objective of this study was to characterize the interaction of abacavir with P-gp and determine whether P-gp is an important mechanism in limiting abacavir delivery to the central nervous system (CNS). In vitro and in vivo techniques were employed to characterize this interaction. Abacavir stimulated P-gp ATPase activity at high concentrations. The cellular accumulation of abacavir was significantly decreased by approximately 70% in Madin-Darby canine kidney II (MDCKII)-MDR1 monolayers compared with wild-type cells and was completely restored by the P-gp inhibitors ((R)-4-((1aR,6R,10bS)-1,2-difluoro-1,1a,6,10b-tetrahydrodibenzo(a,e)cyclopropa(c)cycloheptan-6-yl)-alpha-((5-quinoloyloxy)methyl)-1-piperazineethanol, trihydrochloride) (LY335979) and N-[4-[2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]phenyl]-5-methoxy-9-oxo-10H-acridine-4-carboxamide (GF120918). Directional flux experiments indicated that abacavir had greater permeability in the basolateral-to-apical direction (1.58E-05 cm/s) than in the apical-to-basolateral direction (3.44E-06 cm/s) in MDR1-transfected monolayers. The directionality in net flux was abolished by both LY335979 and GF120918. In vivo brain distribution studies showed that the AUC(plasma) in mdr1a(-/-) CF-1 mutant mice was approximately 2-fold greater than the AUC(plasma) in the wild type, whereas the AUC(brain) in the mutant was 20-fold higher than that in the wild type. Therefore, the CNS drug targeting index, defined as the ratio of AUC brain-to-plasma for mutant over wild type, was greater than 10. These data are the first in vitro and in vivo evidence that a nucleoside reverse transcriptase inhibitor is a P-gp substrate. The remarkable increase in abacavir brain distribution in P-gp-deficient mutant mice over wild-type mice suggests that P-gp may play a significant role in restricting the abacavir distribution to the CNS.