A novel pharmacokinetic approach to predict virologic failure in HIV-1-infected paediatric patients

Hair Zidovudine Concentrations Predict Virologic Outcomes Among People Living with HIV/AIDS in China

BACKGROUND

Hair antiretroviral concentrations are an objective and non-invasive measure of adherence to long-term antiretroviral therapy (ART) and can further predict virologic outcomes among people living with HIV/AIDS (PLWH). Zidovudine, one of the mainstream antiretrovirals in China, has been verified to have high reliability in adherence assessment, especially for its hair concentrations. However, data are limited in its predicting virologic outcomes. Therefore, this study aimed to characterize whether hair zidovudine concentrations can predict virologic suppression among Chinese PLWH compared with hair lamivudine concentrations and two self-reported measures, the overall frequency of adherence behaviors and percentage adherence.

METHODS

This cross-sectional study randomly recruited 564 PLWH currently treated with zidovudine, lamivudine, and other ART agents (efavirenz, nevirapine, or lopinavir/ritonavir) in Guangxi, China. Hair antiretroviral concentrations were determined using the LC-ESI⁺-MS/MS method. Receiver operating characteristic (ROC) curves were used to estimate the optimal classification thresholds of hair concentrations of zidovudine and lamivudine, and the two self-reported measures. Based on those optimal classification thresholds, logistic regression was used to examine whether those four adherence measures can predict virologic suppression (HIV-1 RNA <200 copies/mL).

RESULTS

ROC curves demonstrated good classification performance for association with virologic suppression of zidovudine with the optimal threshold at 58 pg/mg and lamivudine at 255 pg/mg but no self-reported measures. PLWH with hair zidovudine concentrations >58 pg/mg had an adjusted odds ratio (aOR) of 43.191 (95% confidence interval (CI) = 10.171‒183.418, p < 0.001) for virologic suppression. Hair lamivudine concentrations were also associated with virologic suppression (aOR = 10.656, 95% CI = 3.670‒30.943, p < 0.001). However, two self-reported measures did not predict virologic suppression (aORs = 1.157 and 2.488, ps >0.149).

CONCLUSION

Hair zidovudine concentrations can be served as an alternative tool for clinically predicting virologic suppression among PLWH in China.

Concentration-response model of rilpivirine in a cohort of HIV-1-infected naive and pre-treated patients

BACKGROUND

Rilpivirine is widely prescribed in people living with HIV. Although trough plasma concentrations have been associated with virological response, the drug pharmacodynamics remain incompletely characterized.

OBJECTIVES

To develop the first pharmacodynamic model of rilpivirine in order to establish the rilpivirine concentration-response relationship for future treatment optimization.

METHODS

A retrospective observational study was conducted in patients receiving the once-daily rilpivirine/tenofovir disoproxil fumarate/emtricitabine regimen. Individual rilpivirine trough plasma concentrations over time were predicted using a previous pharmacokinetic model. An established susceptible, infected, recovered model was used to describe HIV dynamics without assuming disease steady-state. Population analysis was performed with MONOLIX 2018 software. Simulations of the viral load evolution as a function of time and rilpivirine trough plasma concentration were performed.

RESULTS

Overall, 60 naive and 39 pre-treated patients were included with a follow-up ranging from 2 to 37 months. The final model adequately described the data and the pharmacodynamic parameters were estimated with a good precision. The population typical value of rilpivirine EC50 was estimated at 65 ng/mL. A higher infection rate constant of CD4 cells for HIV-1 was obtained in pre-treated patients. Consequently, the time to obtain virological suppression was longer in pre-treated than in naive patients.

CONCLUSIONS

The concentration-response relationship of rilpivirine was satisfactorily described for the first time using an original population pharmacodynamic model. Simulations performed using the final model showed that the currently used 50 ng/mL rilpivirine trough plasma concentration efficacy target might need revision upwards, particularly in pre-treated patients.

Role of efavirenz plasma concentrations on long-term HIV suppression and immune restoration in HIV-infected children

Background

To access the long term relationship between efavirenz plasma concentrations and evolution of HIV RNA loads and CD4 cell counts in children.

Methods

Retrospective analysis of data from HIV-infected children on first line efavirenz-containing regimen. A population pharmacokinetic-pharmacodynamic (PK-PD) model was developed to describe the evolution of HIV RNA load and CD4 cell count (efficacy outcomes) in relation to efavirenz plasma concentration. Individual CYP2B6 516 G>T genotype data were not available for this analysis. A score (IS_EFV) quantifying the effect of efavirenz concentrations on the long-term HIV replication was calculated from efavirenz concentrations and PD parameters and, a value of IS_EFV below which HIV replication is likely not suppressed was determined. Cox proportional hazards regression models were used to assess the association of the risk of viral replication with IS_EFV, and with efavirenz mid-dose concentration(C₁₂).

Results

At treatment initiation, median (interquartile range, IQR) age was 8 years (5 to 10), body weight 17 kg (14 to 23), HIV RNA load 5.1 log₁₀ copies/mL (4.6 to 5.4), and CD4 cell count 71 cells/mm³. A model of PK-PD viral dynamics assuming that efavirenz decreases the rate of infected host cells adequately described the relationship of interest. After adjusting for age, baseline HIV RNA load and CD4 cell counts an IS_EFV <85% was significantly associated with a higher risk of viral replication (p-value <0.001) while no significant association was observed with C₁₂ <1.0 mg/L.

Conclusion

The IS_EFV score was a good predictor of viral replication in children on efavirenz-based treatment.

Determinants of virological outcome and adverse events in African children treated with paediatric nevirapine fixed-dose-combination tablets

BACKGROUND

Nevirapine is the only nonnucleoside reverse transcriptase inhibitor currently available as a paediatric fixed-dose-combination tablet and is widely used in African children. Nonetheless, the number of investigations into pharmacokinetic determinants of virological suppression in African children is limited, and the predictive power of the current therapeutic range was never evaluated in this population, thereby limiting treatment optimization.

METHODS

We analysed data from 322 African children (aged 0.3-13 years) treated with nevirapine, lamivudine, and either abacavir, stavudine, or zidovudine, and followed up to 144 weeks. Nevirapine trough concentration (Cmin) and other factors were tested for associations with viral load more than 100 copies/ml and transaminase increases more than grade 1 using proportional hazard and logistic models in 219 initially antiretroviral treatment (ART)-naive children.

RESULTS

Pre-ART viral load, adherence, and nevirapine Cmin were associated with viral load nonsuppression [hazard ratio = 2.08 (95% confidence interval (CI): 1.50-2.90, P < 0.001) for 10-fold higher pre-ART viral load, hazard ratio = 0.78 (95% CI: 0.68-0.90, P < 0.001) for 10% improvement in adherence, and hazard ratio = 0.94 (95% CI: 0.90-0.99, P = 0.014) for a 1 mg/l increase in nevirapine Cmin]. There were additional effects of pre-ART CD4 cell percentage and clinical site. The risk of virological nonsuppression decreased with increasing nevirapine Cmin, and there was no clear Cmin threshold predictive of virological nonsuppression. Transient transaminase elevations more than grade 1 were associated with high Cmin (>12.4 mg/l), hazard ratio = 5.18 (95% CI 1.95-13.80, P < 0.001).

CONCLUSION

Treatment initiation at lower pre-ART viral load and higher pre-ART CD4 cell percentage, increased adherence, and maintaining average Cmin higher than current target could improve virological suppression of African children treated with nevirapine without increasing toxicity.

Are Prophylactic and Therapeutic Target Concentrations Different?: the Case of Lopinavir-Ritonavir or Lamivudine Administered to Infants for Prevention of Mother-to-Child HIV-1 Transmission during Breastfeeding

The ANRS 12174 trial assessed the efficacy and tolerance of lopinavir (LPV)-ritonavir (LPV/r) prophylaxis versus those of lamivudine (3TC) prophylaxis administered to breastfed infants whose HIV-infected mothers were not on antiretroviral therapy. In this substudy, we assessed LPV/r and 3TC pharmacokinetics to evaluate the percentage of infants with therapeutic plasma concentrations and to discuss these data in the context of a prophylactic treatment. Infants from the South African trial site underwent blood sampling for pharmacokinetic study at weeks 6, 26, and 38 of life. We applied a Bayesian approach to derive the 3TC and LPV pharmacokinetic parameters on the basis of previously published pharmacokinetic models for HIV-infected children. We analyzed 114 LPV and 180 3TC plasma concentrations from 69 infants and 92 infants, respectively. A total of 30 LPV and 20 3TC observations were considered missing doses and discarded from the Bayesian analysis. The overall population analysis showed that 30 to 40% of the infants did not reach therapeutic targets, regardless of treatment group. The median LPV trough concentrations at weeks 6, 26, and 38 were 2.8 mg/liter (interquartile range [IQR], 1.7 to 4.4 mg/liter), 5.6 mg/liter (IQR, 3.2 to 7.7 mg/liter), and 3.4 mg/liter (IQR, 2.3 to 7.3 mg/liter), respectively. The median 3TC area under the curve from 0 to 12 h after the last drug intake were 5.6 mg · h/liter (IQR, 4.1 to 7.8 mg · h/liter), 5.9 mg · h/liter (IQR, 5.1 to 7.5 mg · h/liter), and 7.3 mg · h/liter (IQR, 4.9 to 8.5 mg · h/liter) at weeks 6, 26, and 38, respectively. Use of the therapeutic doses recommended by the WHO would have resulted in a higher proportion of infants achieving the targets. However, no HIV-1 infection was reported among these infants. These results suggest that the prophylactic targets for both 3TC and LPV may be lower than the therapeutic ones. For treatment, the WHO dosing guidelines should be suitable to maintain values above the therapeutic pharmacokinetic targets in most infants. (This study has been registered at ClinicalTrials.gov under identifier NCT00640263.).

Optimization of the strength of the efavirenz/lamivudine/abacavir fixed-dose combination for paediatric patients

BACKGROUND

Child-friendly, low-cost, solid, oral fixed-dose combinations (FDCs) of efavirenz with lamivudine and abacavir are urgently needed to improve clinical management and drug adherence for children.

METHODS

Data were pooled from several clinical trials and therapeutic drug monitoring datasets from different countries. The number of children/observations was 505/3667 for efavirenz. Population pharmacokinetic analyses were performed using a non-linear mixed-effects approach. For abacavir and lamivudine, data from 187 and 920 subjects were available (population pharmacokinetic models previously published). Efavirenz/lamivudine/abacavir FDC strength options assessed were (I) 150/75/150, (II) 120/60/120 and (III) 200/100/200 mg. Monte Carlo simulations of the different FDC strengths were performed to determine the optimal dose within each of the WHO weight bands based on drug efficacy/safety targets.

RESULTS

The probability of being within the target efavirenz concentration range 12 h post-dose (1-4 mg/L) varied between 56% and 60%, regardless of FDC option. Option I provided a best possible balance between efavirenz treatment failure and toxicity risks. For abacavir and lamivudine, simulations showed that for option I >75% of subjects were above the efficacy target.

CONCLUSIONS

According to simulations, a paediatric efavirenz/lamivudine/abacavir fixed-dose formulation of 150 mg efavirenz, 75 mg lamivudine and 150 mg abacavir provided the most effective and safe concentrations across WHO weight bands, with the flexibility of dosage required across the paediatric population.

Special considerations concerning the use of antiretroviral drugs in children

INTRODUCTION

Antiretroviral therapy is extremely effective in both children and adults infected with HIV. Treatment indications have rapidly expanded; ideally, with rare exceptions, all infected children should now be treated. Areas covered: The use of antiretroviral drugs in children is based largely on extrapolations from experience with adult patients. Pharmacokinetic studies are required in addition to formal studies, which are difficult to conduct in pediatric situations, extending from birth to adolescence. However, despite often inadequate galenic formulation, treatment of children is easier than generally thought. No major or irreversible toxicity has been observed with the latest generation of molecules. Several observations suggest that very early treatment, beginning shortly after birth, provides better long-term immunological control of infection. Expert commentary: All HIV-infected children should be treated with antiretroviral drugs. Manufacturers should propose appropriate dosage forms, including combined forms in particular, and should support pharmacological and tolerance studies in pediatric patients of various ages. Very early treatment maximizes the chances of long-term immunological control.

Pharmacokinetic/pharmacodynamic modelling approaches in paediatric infectious diseases and immunology

Pharmacokinetic/pharmacodynamic (PKPD) modelling is used to describe and quantify dose-concentration-effect relationships. Within paediatric studies in infectious diseases and immunology these methods are often applied to developing guidance on appropriate dosing. In this paper, an introduction to the field of PKPD modelling is given, followed by a review of the PKPD studies that have been undertaken in paediatric infectious diseases and immunology. The main focus is on identifying the methodological approaches used to define the PKPD relationship in these studies. The major findings were that most studies of infectious diseases have developed a PK model and then used simulations to define a dose recommendation based on a pre-defined PD target, which may have been defined in adults or in vitro. For immunological studies much of the modelling has focused on either PK or PD, and since multiple drugs are usually used, delineating the relative contributions of each is challenging. The use of dynamical modelling of in vitro antibacterial studies, and paediatric HIV mechanistic PD models linked with the PK of all drugs, are emerging methods that should enhance PKPD-based recommendations in the future.