Age-related effects on nelfinavir and M8 pharmacokinetics: a population study with 182 children

Preventive and therapeutic benefits of nelfinavir in rhesus macaques and human beings infected with SARS-CoV-2

Effective drugs with broad spectrum safety profile to all people are highly expected to combat COVID-19 caused by SARS-CoV-2. Here we report that nelfinavir, an FDA approved drug for the treatment of HIV infection, is effective against SARS-CoV-2 and COVID-19. Preincubation of nelfinavir could inhibit the activity of the main protease of the SARS-CoV-2 (IC₅₀ = 8.26 μM), while its antiviral activity in Vero E6 cells against a clinical isolate of SARS-CoV-2 was determined to be 2.93 μM (EC₅₀). In comparison with vehicle-treated animals, rhesus macaque prophylactically treated with nelfinavir had significantly lower temperature and significantly reduced virus loads in the nasal and anal swabs of the animals. At necropsy, nelfinavir-treated animals had a significant reduction of the viral replication in the lungs by nearly three orders of magnitude. A prospective clinic study with 37 enrolled treatment-naive patients at Shanghai Public Health Clinical Center, which were randomized (1:1) to nelfinavir and control groups, showed that the nelfinavir treatment could shorten the duration of viral shedding by 5.5 days (9.0 vs. 14.5 days, P = 0.055) and the duration of fever time by 3.8 days (2.8 vs. 6.6 days, P = 0.014) in mild/moderate COVID-19 patients. The antiviral efficiency and clinical benefits in rhesus macaque model and in COVID-19 patients, together with its well-established good safety profile in almost all ages and during pregnancy, indicated that nelfinavir is a highly promising medication with the potential of preventative effect for the treatment of COVID-19.

Therapeutic drug monitoring of antiretroviral drugs in HIV-infected patients

INTRODUCTION

Therapeutic drug monitoring (TDM) may be beneficial when applied to antiretroviral (ARV). Even though TDM can be a valuable strategy in HIV management, its role remains controversial. Areas covered: This review provides a comprehensive update on important issues relating to TDM of ARV drugs in HIV-infected patients. Articles from PubMed with keywords relevant to each topic section were reviewed. Search strategies limited to articles published in English. Expert commentary: There is evidence supporting the use of TDM in HIV treatment. However, some limitations need to be considered. The evidence supporting the use of routine TDM for all patients is limited, as it is not clear that this strategy offers any advantages over TDM for selected indications. Selected groups of patients including patients with physiological changes, patients with drug-drug interactions or toxicity, and the elderly could potentially benefit from TDM, as optimized dosing is challenging in these populations.

Children with HIV are not small adults: what is different in pharmacology?

PURPOSE OF REVIEW

The pharmacokinetics of antiretroviral drugs are highly variable among HIV-infected children. This review describes pharmacokinetic processes in children and recent pharmacokinetic data in children with HIV. The general lack of pharmacokinetic data and the potential role of therapeutic drug monitoring are discussed.

RECENT FINDINGS

It was found unexpectedly that exposure to lopinavir is decreased in the first 6 months of life. Recent findings of subtherapeutic efavirenz concentrations in children suggest that pediatric dose recommendations should be re-evaluated. In addition, recommended dosing of lamivudine leads to lower exposure in children younger than 6 years of age. Preliminary results of pediatric fixed-dose combination tablets for HIV-infected children with a higher nevirapine to stavudine and lamivudine ratio than adult fixed-dose combinations suggest adequate drug exposure. As an alternative to plasma sampling, concentrations of nevirapine can be determined in saliva.

SUMMARY

There is a shortage of pharmacokinetic data in the highly variable population of HIV-infected children. Selected pharmacology studies should be undertaken to improve pediatric dose guidance of existing antiretroviral drugs. Therapeutic drug monitoring is a useful tool to optimize treatment in HIV-infected children. More data are needed, however, to establish child-specific reference values.

Nelfinavir and Lamivudine pharmacokinetics during the first two weeks of life

BACKGROUND

There are no previous data describing nelfinavir and lamivudine pharmacokinetics in neonates treated with weight-band dosing regimens.

DESIGN

Pharmacokinetic study of nelfinavir and lamivudine pharmacokinetics in infants during the first 2 weeks of life treated with weight-band dosing regimens.

METHODS

Intensive 12-hour pharmacokinetic profiles were performed between either days 4-7 or days 10-14 of life in 26 Brazilian infants.

RESULTS

Pharmacokinetic data were obtained from 26 infants who received median (range) per kg doses of 58.8 (48.4-79.0) mg/kg for nelfinavir and 2.0 (1.5-3.2) mg/kg for lamivudine. Median nelfinavir 12-hour AUC (AUC0-12) was 25.5 (1.7-183.5) μg*h/mL and median 12-hour concentration (C12h) was 1.09 (<0.04-14.44) μg/mL. AUC0-12 was less than 15 μg*h/mL (the 10% for adults) in 12 infants (46%). Median lamivudine AUC0-12 was 7.8 (2.7-15.6) μg*h/mL and median C12h was 0.23 (<0.04-0.74) μg/mL.

CONCLUSIONS

: Lamivudine pharmacokinetic parameters observed in this study were consistent with those seen in other studies of neonates. While median nelfinavir AUC and C12h in these neonates were above the exposure targets, interindividual variability in nelfinavir exposure was large and nelfinavir exposure failed to meet the exposure targets in 46% of infants.

Novel strategies in the use of lopinavir/ritonavir for the treatment of HIV infection in children

Lopinavir/ritonavir (LPV/r) is considered by many as the first choice protease inhibitor (PI) for children. This co-formulation avoids the need for children to take ritonavir separately to “boost” the levels of lopinavir. LPV/r has high virologic potency, an excellent toxicity profile and a high barrier to the development of viral resistance. However, LPV/r has poor tolerability of the oral suspension (due to the poor taste of ritonavir), difficult dosing requirements and metabolic side effects, especially hyperlipidemia. The new tablet low-dose formulation (100/25 mg) may allow more convenient antiretroviral treatment in children. Novel strategies of LPV/r in childhood could maximize its advantages. For example, infants infected with HIV despite single dose Nevirapine after birth need effective combination antiretroviral treatment. This can be given using a higher dose of LPV/r with therapeutic drug monitoring. Other novel uses include once daily LPV/r regimens in older children and adolescents and lower doses of LPV/r in certain populations, which may decrease hyperlipidemia. Heavily pre-treated children might benefit from a double PI/r regimen which includes LPV/r. The high potency of LPV/r needs to be balanced with convenient regimens, to enhance adherence and decrease toxicity whenever possible. The aim of this review is to discuss the rationale behind these novel strategies of LPV/r use in pediatric antiretroviral treatment as well as their results and limitations.

Practical therapeutic drug management in HIV-infected patients: use of population pharmacokinetic models supplemented by individualized Bayesian dose optimization

Individualized, model-based, target-oriented optimal concentration-controlled dosing of HIV medications can be beneficial to patients for whom there are limited dosing guidelines, such as children, adolescents, or patients with altered physiologic function. Barriers to this approach include lack of training, expertise, and access to appropriate software to assist the clinician. The authors present 4 illustrative clinical cases of HIV-infected patients whose therapy was optimized using population pharmacokinetic models (here generated from published studies) and supplemented by individualized Bayesian adaptive control of dosage regimens as implemented in the MM-USCPACK software. These 4 cases illustrate how clinicians can maximize therapeutic success in (1) patients with reduced drug clearance, (2) young adolescents transitioning to adult physiology, (3) patients with dose-dependent toxicity, and (4) adolescents with limited therapeutic options.

Population pharmacokinetics and dose simulation of carvedilol in paediatric patients with congestive heart failure

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Applying in silico tools such as population pharmacokinetic analysis and simulation will help to find adequate dosing strategies and increase the probability of success for a randomized controlled trial. * Up to now, for carvedilol in paediatric patients with congestive heart failure (CHF) the dose has been linearly extrapolated from adults, but the results with this dosing strategy are ambiguous. * Further trials are necessary to establish carvedilol for paediatric patients with CHF.

WHAT THIS STUDY ADDS

* Carvedilol pharmacokinetics in paediatric patients with CHF depends on the weight and age of the patient. * Therefore, the drug exposure differs substantially between patients of different ages receiving the same dose with respect to body weight. * Simulations revealed that an age-adjusted carvedilol dosing strategy with higher doses for younger patients with respect to body weight is preferable to a uniform one.

AIMS

To investigate the ontogeny of carvedilol pharmacokinetics and to develop an age-appropriate carvedilol dosing strategy for paediatric patients.

METHODS

Data were derived from a prospective, nonplacebo-controlled study of carvedilol for the treatment of paediatric patients with congestive heart failure and analysed using a nonlinear mixed-effects modelling approach (NONMEM, Version V 1.1). The population pharmacokinetic model was further utilized for simulations of different carvedilol dosing strategies.

RESULTS

Four hundred and eighty carvedilol plasma concentrations of 41 patients (0.1-19.3 years; median 3.5) were included in the analysis. A two-compartment model with first-order absorption and absorption lag served as structural model. Weight and age were the most important covariates for carvedilol pharmacokinetics. The weight-adjusted clearance was highest for the younger patients with 2.7 l h(-1) kg(-1) for a 1-year-old patient compared with 0.7 l h(-1) kg(-1) for a 19.3-year-old patient. Dose simulations revealed that the area under the plasma concentration-time curve (AUC) as a measure of drug exposure increased with age despite constant doses with respect to body weight. For infants (28 days to 23 months), children (2-11 years) and adolescents (12-15 years) daily doses of 3, 2 and 1 mg kg(-1), administered in two or three discrete doses, were necessary to reach an exposure comparable to adults receiving 0.7 mg kg(-1) day(-1).

CONCLUSION

The ontogeny of carvedilol pharmacokinetics in paediatric patients depends on age and weight. Dose simulations revealed that younger patients have to be treated with higher doses with respect to body weight to reach the same exposure as adults.

Effect of CYP2C19 polymorphism on nelfinavir to M8 biotransformation in HIV patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Nelfinavir is an HIV protease inhibitor, substrate of the transporter P-glycoprotein and metabolized via CYP2C19, CYP3A4 and CYP3A5 enzymes. * Pharmacokinetic studies have shown wide interindividual variability of nelfinavir concentrations, some of this variability perhaps caused by variant drug metabolism or transporter genes. * For CYP3A4*1B and CYP3A5*3 polymorphism, results from three studies are in agreement, showing no difference in nelfinavir concentrations between patients with these different genotypes. * However, for MDR1 and CYP2C19 polymorphism, there have been contradictory studies, showing either no impact on nelfinavir concentration or modified concentrations which could influence virological response.

WHAT THIS STUDY ADDS

* Patients with an *1/*2 or *2/*2 genotype for CYP2C19 had a nelfinavir to M8 biotransformation divided by 2 compared with *1/*1 patients. * No evidence of any influence of MDR1 polymorphism on nelfinavir absorption could be detected.

AIMS

To evaluate the effect of CYP2C19 polymorphism on nelfinavir and M8 pharmacokinetic variability in human immunodeficiency virus-infected patients and to study the link between pharmacokinetic exposure and short-term efficacy and toxicity.

METHODS

Nelfinavir (n = 120) and M8 (n = 119) concentrations were measured in 34 protease inhibitor-naive patients. Two weeks after initiating the treatment, blood samples were taken before, 1, 3 and 6 h after drug administration. Genotyping for CYP3A4, 3A5, 2C19 and MDR1 was performed. A population pharmacokinetic model was developed to describe nelfinavir-M8 concentration time-courses and to estimate interpatient variability. The influence of individual characteristics and genotypes were tested using a likelihood ratio test. Estimated mean (C(mean)), maximal (C(max)) and trough (C(trough)) nelfinavir and M8 concentrations were correlated to short-term virological efficacy and tolerance using Spearman nonparametric correlation tests.

RESULTS

A one-compartment model with first-order absorption, elimination and metabolism to M8 best described nelfinavir data. M8 was modelled by an additional compartment. Mean pharmacokinetic estimates and the corresponding intersubject variabilities were: absorption rate 0.17 h(-1) (99%), absorption lag time 0.82 h, apparent nelfinavir total clearance 52 l h(-1) (49%), apparent nelfinavir volume of distribution 191 l, M8 elimination rate constant 1.76 h(-1) and nelfinavir to M8 0.39 h(-1) (59%) in *1/*1 patients and 0.20 h(-1) in *1/*2 or *2/*2 patients for CYP2C19*2. Nelfinavir C(mean) was positively correlated to glycaemia and triglyceride increases (P = 0.02 and P = 0.04, respectively).

CONCLUSIONS

The rate of metabolism of nelfinavir to M8 was reduced by 50% in patients with *1/*2 or *2/*2 genotype for CYP2C19 compared with those with *1/*1 genotype.

Pharmacokinetic modelling of the placental transfer of nelfinavir and its M8 metabolite: a population study using 75 maternal-cord plasma samples

AIMS

A population pharmacokinetic model was developed to characterize the transfer of nelfinavir and its active metabolite M8 from maternal to cord plasma and amniotic fluid.

METHODS

Concentration data were obtained from 75 women on the day of delivery and for whom maternal, umbilical plasma and amniotic fluid samples were collected. Data from 53 pregnant, 61 nonpregnant and seven consecutively pregnant and non pregnant women were then added to the database, the contents of which were analyzed using NONMEM.

RESULTS

Nelfinavir and M8 concentrations in maternal plasma, umbilical plasma and amniotic fluid were described by six connected compartments. Mean (% intersubject variability) population estimates were: absorption rate 00.67 h(-1), lag time 00.87 h, oral clearance and volume of distribution: 39.5 l h(-1) (53%), and 557 l for non pregnant and pregnant women, respectively, and 115 l h(-1) (132%) and 1626 l, respectively, on the day of delivery, M8 formation clearance 0.77 l h(-1) and M8 elimination rate constant 03.41 h(-1) (74%). For nelfinavir and M8, respectively, the mother-to-cord parameters were 0.058 l h(-1) (34%), and 00.35 h(-1) (76%), the cord-to-amniotic fluid rate constants were 0.23 and 00.59 h(-1), and the elimination rate constants from amniotic fluid were 0.36 and 00.49 h(-1). The nelfinavir fetus : maternal concentration ratio was 25% for maternal concentrations between 0.1 and 2.5 mg l(-1), between the 31 and 41st week of gestation.

CONCLUSIONS

The low transfer of nelfinavir from the placenta is unlikely to protect the fetus from vertical HIV-1 transmission.

Lopinavir/Ritonavir pharmacokinetic profile: impact of sex and other covariates following a change from twice-daily to once-daily therapy

The aim of this study was to determine the impact of sex on the pharmacokinetics of lopinavir/ritonavir. Interaction between lopinavir/ritonavir and tenofovir was also evaluated. Steady-state plasma samples were obtained from virologically suppressed HIV-infected patients on lopinavir/ritonavir 800/200-mg soft gel capsule taken once daily. Drug assays were performed by high-performance liquid chromatography. Pharmacokinetic parameters estimated by noncompartmental method were reported as 90% confidence intervals (CIs) about the geometric mean ratio (GMR). There were 9 males and 11 females. No sex differences were observed in lopinavir/ritonavir pharmacokinetics profile. The GMR(sex) (women compared with men) for lopinavir area under the concentration-time curve (AUC(24)), maximum concentration (C(max)), and minimum concentration (C(min)) was 0.95 (90% CI, 0.70-1.29), 0.88 (90% CI, 0.67-1.15), and 1.27 (90% CI, 0.60-2.66), respectively. Similarly, the GMR(sex) for ritonavir AUC(24), C(max), and C(min) was 0.84 (90% CI, 0.57-1.24), 0.79 (90% CI, 0.50-1.22), and 1.02 (90% CI, 0.58-1.80), respectively. Tenofovir coadministration led to a reduction in lopinavir/ritonavir plasma exposure, giving a lopinavir GMR(tenofovir) for C(max) of 0.72 (90% CI, 0.57-0.93) and AUC(24) of 0.74 (90% CI, 0.56-0.98), respectively. No difference in lopinavir/ritonavir plasma concentrations between sexes was demonstrated in this study. However, tenofovir coadministration lowered lopinavir/ritonavir plasma exposure.

Pregnancy-related effects on nelfinavir-M8 pharmacokinetics: a population study with 133 women

A relationship between nelfinavir antiretroviral efficacy and plasma concentrations has been previously established. As physiological changes associated with pregnancy have a large impact on the pharmacokinetics of many drugs, a nelfinavir population study with women was developed, and the large intersubject variability was analyzed in order to optimize individual treatment schedules for this drug during pregnancy. A population pharmacokinetic model was developed in order to describe the concentration time course of nelfinavir and its metabolite M8 in pregnant and nonpregnant women. Individual characteristics, such as age, body weight, and weeks of gestation or delivery, which may influence nelfinavir-M8 pharmacokinetics were investigated. Data from therapeutic drug monitoring in 133 women treated with nelfinavir were retrospectively analyzed with NONMEM. Nelfinavir pharmacokinetics was described by a one-compartment model with linear absorption and elimination and M8 produced from the nelfinavir central compartment. Mean pharmacokinetic estimates and the corresponding intersubject percent variabilities for a nonpregnant woman were the following: absorption rate, 0.83 h(-1); absorption lag time, 0.85 h; apparent nelfinavir elimination clearance (CL(10)/F), 35.5 liters/h (50%); apparent volume of distribution (V/F), 596 liters (118%); apparent formation clearance to M8 (CL(1M)/F), 0.65 liters/h (69%); and M8 elimination rate constant (k(M0)), 3.3 h(-1) (59%). During pregnancy, we observed significant increases in nelfinavir (44.4 liters/h) and M8 (5 h(-1)) elimination but unchanged nelfinavir transformation clearance to M8, suggesting an induction of CYP3A4 but no effect on CYP2C19. Apparent nelfinavir clearance and volume showed a twofold increase on the day of delivery, suggesting a decrease in bioavailability on this day. The M8 elimination rate was increased by concomitant administration of nonnucleoside reverse transcriptase inhibitors. A trough nelfinavir plasma concentration above 1 mg/liter was previously shown to improve the antiretroviral response. The Bayesian individual pharmacokinetic estimates suggested that the dosage should not be changed in pregnant women but may be doubled on the day of delivery.