Developmental pharmacokinetic changes of Lamivudine in infants and children

Important roles of transporters in the pharmacokinetics of anti-viral nucleoside/nucleotide analogs

INTRODUCTION

Nucleoside analogs are an important class of antiviral agents. Due to the high hydrophilicity and limited membrane permeability of antiviral nucleoside/nucleotide analogs (AVNAs), transporters play critical roles in AVNA pharmacokinetics. Understanding the properties of these transporters is important to accelerate translational research for AVNAs.

AREAS COVERED

The roles of key transporters in the pharmacokinetics of 25 approved AVNAs were reviewed. Clinically relevant information that can be explained by the modulation of transporter functions is also highlighted.

EXPERT OPINION

Although the roles of transporters in the intestinal absorption and renal excretion of AVNAs have been well identified, more research is warranted to understand their roles in the distribution of AVNAs, especially to immune privileged compartments where treatment of viral infection is challenging. P-gp, MRP4, BCRP, and nucleoside transporters have shown extensive impacts in the disposition of AVNAs. It is highly recommended that the role of transporters should be investigated during the development of novel AVNAs. Clinically, co-administered inhibitors and genetic polymorphism of transporters are the two most frequently reported factors altering AVNA pharmacokinetics. Physiopathology conditions also regulate transporter activities, while their effects on pharmacokinetics need further exploration. Pharmacokinetic models could be useful for elucidating these complicated factors in clinical settings.

Pharmacokinetics and Safety of the Abacavir/Lamivudine/Lopinavir/Ritonavir Fixed-Dose Granule Formulation (4-in-1) in Neonates: PETITE Study

BACKGROUND

Antiretroviral options for neonates (younger than 28 days) should be expanded. We evaluated the pharmacokinetics, safety, and acceptability of the "4-in-1" fixed-dose pediatric granule formulation of abacavir/lamivudine/lopinavir/ritonavir (30/15/40/10 mg) in neonates.

METHODS

The PETITE study is an ongoing phase I/II, open-label, single-arm, 2-stage trial conducted in South Africa. In stage 1, term neonates exposed to HIV on standard antiretroviral prophylaxis (nevirapine ± zidovudine) received single dose(s) of the 4-in-1 formulation, followed by intensive pharmacokinetic sampling and safety assessments. At each PK visit, blood was drawn after an observed dose at 1, 2, 4, 8, and 12 hours postdose. In this study, we have reported the planned interim pharmacokinetic and safety analysis after completion of the single-dose administration.

RESULTS

Sixteen neonates, with a median (range) birth weight of 3130 g (2790-3590 g), completed 24 pharmacokinetic visits. The 4-in-1 formulation imposed relatively high doses of abacavir [8.6 mg/kg (6.6-11.4)] and lamivudine [4.3 mg/kg (3.3-5.7)] but lower doses of lopinavir [11.5 mg/kg (8.8-15.2)]. The geometric means (GM, 90% CI) AUC0-12 of abacavir, lamivudine, and lopinavir were 29.87 (26.29-33.93), 12.61 (10.72-14.83), and 3.49 (2.13-5.72) µg.h/mL, respectively. Lopinavir GM AUC0-12 was below the predefined target (20-100 µg.h/mL), and ritonavir concentrations were only detectable in 4 of the 120 (3%) samples. No adverse events were related to study drugs. No neonate had difficulty swallowing the 4-in-1 formulation.

CONCLUSIONS

The high doses of abacavir and lamivudine (in mg/kg) and AUCs were safe, and the formulation was well tolerated; however, lopinavir/ritonavir exposures were extremely low, preventing its use in neonates use in neonates. Alternative pediatric solid antiretroviral formulations must be studied in neonates.

Comparison of three galenic forms of lamivudine in young West African children living with Human Immunodeficiency Virus

Background

Few pharmacokinetic data were reported on dispersible tablets despite their increasing use. One hundred fifty HIV-infected children receiving lamivudine were enrolled in the MONOD ANRS 12,206 trial. Three galenic forms were administered: liquid formulation, tablet form and dispersible scored tablet.

Method

HIV-infected children <4 years old were enrolled in the MONOD ANRS 12,206 trial designed to assess the simplification of a successful 12-months lopinavir-based antiretroviral treatment with efavirenz. Lamivudine plasma concentrations were analysed using nonlinear mixed effects modelling approach.

Results

One hundred and fifty children (age: 2.5 years (1.9–3.2), weight 11.1 (9.5–12.5) kg (median (IQR)) were included in this study. Over the study period, 79 received only the syrup form, 29 children switched from syrup form to tablet 3TC/AZT form, 36 from syrup to the orodispersible ABC/3TC form and two from the 3TC/AZT form to the orodispersible ABC/3TC form. The 630 lamivudine concentrations were best described by a two-compartment model allometrically scaled. Galenic form had no significant effect on 3TC pharmacokinetic.

Conclusion

This trial provided an opportunity to compare three galenic forms (liquid formulation, tablet form and dispersible scored tablet) of lamivudine in the target population of young HIV–1-infected children. Galenic form had no significant effect on lamivudine pharmacokinetics.

Early initiation of antiviral therapy contributes to a rapid and significant loss of serum HBsAg in infantile-onset hepatitis B

BACKGROUND & AIM

There is a paucity of data regarding antiviral therapy in hepatitis B virus (HBV)-infected infants aged <1 year who have elevated alanine aminotransferase. This study aims to assess the efficacy and safety of antiviral therapy initiated in infancy.

METHODS

A real-world cohort study was conducted from January 2010 to December 2017. HBV-infected infants under 1 year of age, with persistent elevation of alanine aminotransferase and high viral load, were recruited and divided into 2 groups. Group I included 18 infants whose parents chose to initiate antiviral therapy with lamivudine before 1 year of age. Group II included 11 infants whose parents chose to initiate antiviral therapy with interferon-α after 1 year of age and not to receive any antiviral therapies before 1 year of age. The main outcome measure was rate of serum HBV surface antigen (HBsAg) loss at month 12 of treatment.

RESULTS

There were no statistical differences between Groups I and II regarding baseline characteristics. No infants in Group II developed spontaneous HBsAg loss before 1 year of age. In Group I, the cumulative rates of HBsAg loss at month 3, 6, 9 and 12 of treatment were 39%, 67%, 78% and 83%, respectively. In Group II, the cumulative rates of HBsAg loss at month 3, 6, 9 and 12 of treatment were 18%, 27%, 27% and 36%, respectively. Statistical differences existed in the cumulative rates of HBsAg loss between the 2 groups (log-rank test, p = 0.0023). No serious adverse events occurred in the study.

CONCLUSION

Early initiation of antiviral therapy for infantile-onset hepatitis B contributes to a rapid and significant loss of HBsAg. Further trials with larger cohorts are needed to verify our results.

LAY SUMMARY

Chronicity is a serious threat to infants infected with hepatitis B. However, no treatment measure has been recommended for infantile-onset hepatitis B in current guidelines. In order to evaluate the benefit and safety of antiviral therapy in infantile-onset hepatitis B, a real-world cohort study was conducted. Long-term follow-up results showed that early initiation of antiviral therapy with lamivudine safely led to a rapid and significant loss of serum hepatitis B surface antigen in the present subset of infants with alanine aminotransferase ≥2× upper limit of normal. Further trials with larger cohorts are needed.

Population pharmacokinetics of abacavir and lamivudine in severely malnourished human immunodeficiency virus-infected children in relation to treatment outcomes

AIMS

Describe the pharmacokinetics (PK) of the antiretroviral drugs abacavir and lamivudine in malnourished paediatric patients and relate to viral load outcomes after 12 and 48 weeks of treatment.

METHODS

Severely malnourished human immunodeficiency virus-infected children were randomized to early (within 14 days) or delayed (after nutritional recovery) initiation of antiretroviral treatment (ART) using World Health Organization weight-band dosages. Abacavir and lamivudine concentrations were measured as a secondary objective on day 1 and day 14 and patients were followed-up to week 48. Population PK of abacavir and lamivudine were described using NONMEM.

RESULTS

In total, 623 abacavir and 627 lamivudine concentrations were collected from 75 paediatric patients aged 0.1-10.8 (median 1.4) years. Abacavir PK was described by a 2-compartment model, patients randomized to early ART showed increased bioavailability of 31%. Apparent clearance (CL/F, L/h/7 kg) of abacavir increased from day 1 to day 14 from 3.33 (95% confidence interval 2.71-4.12) to 5.86 (95% confidence interval 4.78-7.3). A 1-compartment model described lamivudine PK, variability on CL/F was explained by maturation with age, with age at half-matured CL/F being 4 months. For both drugs allometrically scaled total body weight was related to CL/F and apparent volume of distribution. PK exposure did not correlate with virological outcomes or death at 12 or 48 weeks.

CONCLUSION

Increases in Abacavir's CL/F between day 1 to day 14, bioavailability and PK variability with early start of ART was found in this cohort of severely malnourished children; however, these changes did not influence virological outcomes. The study supports the use of weight-band dosage tables.

Effect of Sorbitol on the Pharmacokinetic Profile of Lamivudine Oral Solution in Adults: An Open-Label, Randomized Study

In children aged ≤4 years, the relative bioavailability of lamivudine oral solution was 37% lower than that of a tablet formulation. An open-label, four-way crossover study was conducted in healthy adults to evaluate the effect of sorbitol, a common liquid excipient, on the pharmacokinetics of lamivudine oral solution (ClinicalTrials.gov identifier, NCT02634073). Sixteen subjects were randomized to one of four sequences consisting of four doses of lamivudine 300 mg (10 mg/mL) alone or with sorbitol 3.2, 10.2, or 13.4 g. Sorbitol 3.2, 10.2, and 13.4 g decreased lamivudine maximum concentration (C_max ) by 28%, 52%, and 55% and area under the concentration-time curve from time 0 to 24 h (AUC_0-24 ) by 20%, 39%, and 44%, respectively. Three subjects (19%) reported five nonserious adverse events (one drug-related). The dose-dependent effects of sorbitol on lamivudine C_max and AUC_0-24 reveal an absorption-based interaction that may decrease lamivudine exposure in patients coadministered sorbitol-containing medicines.

Prevention and treatment of HIV infection in neonates: evidence base for existing WHO dosing recommendations and implementation considerations

INTRODUCTION

Antiretroviral drugs are used in neonates for prevention and treatment of HIV infection. Use of antiretrovirals to prevent perinatal HIV transmission is well established. Early identification of neonates infected with HIV and rapid initiation of combination antiretroviral treatment during the neonatal period is now recommended by WHO and DHHS. However, few antiretrovirals are available in formulations suitable for neonates and there are limited safety and pharmacokinetic data for most antiretrovirals in neonates. Areas covered: We summarize existing neonatal antiretroviral safety and pharmacokinetic information and discuss implementation considerations for programs providing antiretrovirals to neonates and young infants. Expert commentary: Antiretrovirals currently recommended by WHO for use in neonates are zidovudine, lamivudine, lopinavir/ritonavir, nevirapine, and raltegravir. Significant implementation challenges exist to the widespread use of these antiretrovirals in neonates. Optimal, feasible treatment of HIV-exposed and HIV-infected newborns will require development of practical neonatal dosage forms and their study in neonates for a wide range of antiretrovirals.

Antiretroviral Treatment Initiated in the First Month of Life

BACKGROUND

Earlier diagnosis of HIV-infected infants facilitates earlier access to therapy and improved clinical outcomes. The aim of this study was to describe the management of infants who started antiretroviral therapy (ART) in the first month of life.

METHODS

A retrospective review was performed on HIV-infected neonates who started ART within the first month of life between January 2013 and March 2015.

RESULTS

A total of 997 neonates had 1 HIV polymerase chain reaction test. Of the 997 neonates, 26 (2.6%) tested positive for HIV and 22 initiated therapy in the first month of life. The median age of first HIV polymerase chain reaction test was 7 days. Neonates were started on ART within a median of 7 days of their first HIV test, which equated to a median age of 13.5 [interquartile range (IQR) 7-20] days of life. Median gestational age was 35 weeks (IQR 33-38 weeks), and birth weight was 2170 g (IQR 1773-2480). Nineteen (86.4%) had low birth weight (<2.5 kg) and 16 (72.7%) were premature. Median baseline HIV viral loads were log 4.444 copies/mL (IQR 3.457-5.125), median CD4 counts were 1338 (IQR 803-1928) and CD4% percentages were 36.1% (22.2-45.4). All children initiated zidovudine and lamivudine, 10 with lopinavir/ritonavir and 12 with nevirapine. All children in care are now receiving lopinavir/ritonavir. Of the 22 neonates initiated on treatment, 11 are in care (mean age, 2.1 years), and 2 of these infants had a viral load of <50 copies/ mL when last measured.

CONCLUSIONS

Early ART initiation in neonates is feasible. Challenges include safe, palatable regimens and continued close follow-up of mothers and infants.

Dose evaluation of lamivudine in human immunodeficiency virus-infected children aged 5 months to 18 years based on a population pharmacokinetic analysis

AIM

The objectives of this study were to characterize age-related changes in lamivudine pharmacokinetics in children and evaluate lamivudine exposure, followed by dose recommendations for subgroups in which target steady state area under the daily plasma concentration-time curve (AUC_0-24h ) is not reached.

METHODS

Population pharmacokinetic modelling was performed in NONMEM using data from two model-building datasets and two external datasets [n = 180 (age 0.4-18 years, body weight 3.4-60.5 kg); 2061 samples (median 12 per child); daily oral dose 60-300 mg (3.9-17.6 mg kg^-1 )]. Steady state AUC_0-24h was calculated per individual (adult target 8.9 mg·h l^-1 ).

RESULTS

A two-compartment model with sequential zero order and first order absorption best described the data. Apparent clearance and central volume of distribution (% RSE) were 13.2 l h^-1 (4.2%) and 38.9 l (7.0%) for a median individual of 16.6 kg, respectively. Bodyweight was identified as covariate on apparent clearance and volume of distribution using power functions (exponents 0.506 (20.2%) and 0.489 (32.3%), respectively). The external evaluation supported the predictive ability of the final model. In 94.5% and 35.8% of the children with a body weight >14 kg and <14 kg, respectively, the target AUC_0-24h was reached.

CONCLUSION

Bodyweight best predicted the developmental changes in apparent lamivudine clearance and volume of distribution. For children aged 5 months-18 years with a body weight <14 kg, the dose should be increased from 8 to 10 mg kg^-1  day^-1 if the adult target for AUC_0-24h is aimed for. In order to identify whether bodyweight influences bioavailability, clearance and/or volume of distribution, future analysis including data on intravenously administered lamivudine is needed.

Antiretroviral therapy during the neonatal period

No abstract available

Lopinavir/ritonavir plus lamivudine and abacavir or zidovudine dose ratios for paediatric fixed-dose combinations

BACKGROUND

Lopinavir/ritonavir (LPV/r) is available in a liquid formulation that is far from ideal for treatment of children in resource-poor settings. Flexible, low-cost, solid, oral fixed-dose combinations (FDC) of LPV/r with nucleoside reverse transcriptase inhibitors (LPV/r/abacavir [ABC]/lamivudine [3TC] and LPV/r/zidovudine [ZDV]/3TC) are needed to improve both management and adherence of children. This work aimed to develop appropriate drug ratios and dosing for each FDC.

METHODS

Data from 25 combined datasets included therapeutic drug monitoring and clinical studies from IMPAACT and PENTA. Population pharmacokinetic analyses were performed using Monolix. Monte-Carlo simulations of WHO and FDA dosing recommendations were performed to assess their ability to provide optimal exposure in children weighing 4 to 25 kg based on consensus plasma targets. The LPV/r:3TC:ZDV(ABC) dose ratios were 2.67:1:2(2), respectively.

RESULTS

Using WHO dosage, LPV efficacy target was reached in all weight bands. Given the recommended drug ratios, the dosage for the 4-5.9 kg weight band (LPV/ZDV: 120/90 mg twice daily [bid]) showed more than 20% of subjects had ZDV levels at high risk of neutropenia. Reducing the LPV/ZDV dose to 80/60 mg bid decreased frequency of high ZDV concentrations but retained the LPV efficacy criteria.

CONCLUSIONS

This defined a flexible and simple FDC containing 40 mg LPV, 10 mg ritonavir, 15 mg 3TC and 30 mg ABC or ZDV. According to the weight bands defined by WHO, 4-5.9 kg, 6-9.9 kg, 10-13.9 kg, 14-19.9 kg, 20-24.9 kg, therapeutic doses would be 2, 3, 4, 5 or 6 individual units administered by oral route bid.