Frantz Foissac’s research while affiliated with Université Paris Cité and other places

Background In cases of maternal primary infection with cytomegalovirus (CMV-MPI) maternal treatment with oral valaciclovir 8 g/day has been shown to reduce the risk of fetal infection. The pharmacological profile of this high dosage during pregnancy is not yet known. Objectives To quantify maternal-fetal exposure to valaciclovir 8 g/day in a population pharmacokinetic (popPK) study. Methods Between October 2019 and April 2023, pregnant women referred for CMV-MPI were offered to participate following: (i) CMV-MPI <14 weeks of gestation; (ii) acceptance of valaciclovir 8 g/day; and (iii) consent for amniocentesis. Amniotic fluid was tested for (i) CMV PCR for prenatal diagnosis; and (ii) dosage of aciclovir concentration (the active form of valaciclovir). Maternal serum levels of aciclovir were also measured. Aciclovir assays in both compartments were used for popPK analysis. Pharmacokinetics were described using non-linear mixed-effect modelling. Results We prospectively included 119 women with their 122 fetuses. CMV-MPI occurred at a median of 3.0 (range: −12; + 14) weeks of gestation. CMV-infected pregnant women were treated at a median of 12.3 (range: 4.6–21.4) weeks of gestation for a median duration of 35 days (range: 7–90 days). Median pharmacokinetic parameters (Cmin, Cmax and AUC0–24) were all successfully defined in both maternal blood and amniotic fluid compartments. No differences in aciclovir exposure were observed between infected (n = 12, 9.8%) and non-infected fetuses. Simulations showed that after a last maternal dose, aciclovir concentration would be undetectable in the amniotic fluid after 43–47 h. Conclusions In this popPK study, maternal and fetal pharmacokinetics were established using in vivo data. The results provide a better understanding of how this fetal therapy works.

Background: Limited data exist on how continuous renal replacement therapy (CRRT) affects antimicrobial dosing in pediatric patients. This study examined the impact of pediatric CRRT parameters on the pharmacokinetics (PK) of meropenem, piperacillin, and tazobactam using an in vitro CRRT model. Research design and methods: An in vitro CRRT model with a pediatric ST60 circuit was used to assess antimicrobial clearance during continuous veno-venous hemodialysis (CVVHD) or hemofiltration (CVVH). Antimicrobials were administered intermittently or continuously, with samples taken pre- and post-filter, and from the effluent. The model tested two conditions: 1) off treatment (0 mL/kg/h), and 2) an elimination phase, with CRRT flow rates ranging from 40 to 400 mL/kg/h. Results: Clearance of meropenem, piperacillin, and tazobactam increased significantly with higher dialyzate/ultrafiltration flow rates (p < 0.001). Median clearance rates differed significantly by CRRT flow rates and modality (p < 0.001). Under CVVHD, the saturation coefficient (Sa) decreased with increasing dialyzate flow rates, while under CVVH, the sieving coefficient (Sc) remained stable regardless of ultrafiltration rates. Conclusions: The clearance of low protein-binding, low molecular weight antimicrobials increases with higher CRRT effluent flow rates, with modality-specific differences in clearance dynamics.

Our aim was to describe the pharmacokinetics of paracetamol and its metabolites in extreme preterm neonates in the context of patent ductus arteriosus treatment. Factors associated with inter-individual variability and metabolic pathways were studied. The association between drug exposure and clinical outcomes were investigated. Preterm neonates of 23–26 weeks’ gestational age received paracetamol within 12 h after birth. Plasma concentrations of paracetamol and its metabolites were measured throughout 5 days of treatment. Clinical success was defined as ductus closure on two consecutive days or at day 7. Aspartate aminotransferase and alanine aminotransferase levels were used as surrogates for liver damage. Data from 30 preterm neonates were available for pharmacokinetic analysis. Paracetamol pharmacokinetics were described using a two-compartment model with significant positive effects of weight on clearance and of birth length on peripheral compartment volume. Paracetamol was mainly metabolised into sulphate (89%) then glucuronide (6%), and the oxidative metabolic pathway was reduced (4%). The glucuronidation pathway increased with gestational age, whereas the sulfation pathway decreased. No difference was observed in drug exposure between successful and unsuccessful patients. No increase in aspartate aminotransferase and alanine aminotransferase levels were observed during treatment, and no association was found with either paracetamol or oxidative metabolite exposures. The relative proportions of the metabolic pathways were characterised with gestational age. In the range of observed drug exposures, no association was found with clinical response or liver biomarkers. These findings may suggest that paracetamol concentrations were within the range that already guarantee a maximum effect on ductus closure.

Aims Vigabatrin is an antiepileptic drug used to treat some forms of severe epilepsy in children. The main adverse effect is ocular toxicity, which is related to the cumulative dose. The aim of the study is to identify an acceptable exposure range, both through the development of a population pharmacokinetic model of vigabatrin in children enabling us to calculate patient exposure and through the study of therapeutic response. Methods We performed a retrospective study including children with epilepsy followed at Necker‐Enfants Malades hospital who had a vigabatrin assay between January 2019 and January 2022. The population pharmacokinetic study was performed on Monolix2021 using a nonlinear mixed‐effects modelling approach. Children treated for epileptic spasms were classified into responder and nonresponder groups according to whether the spasms resolved, in order to identify an effective plasma exposure range. Results We included 79 patients and analysed 159 samples. The median age was 4.2 years (range 0.3–18). A 2‐compartment model with allometry and creatinine clearance on clearance best fit our data. Exposure analysis was performed on 61 patients with epileptic spasms. Of the 22 patients who responded (36%), 95% had an AUC0–24 between 264 and 549 mg.h.L⁻¹. Conclusions The population pharmacokinetic model allowed us to identify bodyweight and creatinine clearance as the 2 main factors explaining the observed interindividual variability of vigabatrin. An acceptable exposure range was defined in this study. A target concentration intervention approach using this pharmacokinetic model could be used to avoid overexposure in responder patients.

A major breakthrough in cystic fibrosis (CF) therapy was achievedAQ1 with CFTR modulators. The lumacaftor/ivacaftor combination is indicated for the treatment of CF in pediatric patients above 6 years old. Pharmacokinetic (PK) studies of lumacaftor/ivacaftor in these vulnerable pediatric populations are AQ2crucial to optimize treatment protocols. The objectives of this study were to describe the population PK (PPK) of lumacaftor and ivacaftor in children with CF, and to identify factors associated with interindividual variability. The association between drug exposure and clinical response was also investigated. A total of 75 children were included in this PPK study, with 191 concentrations available for each compound and known metabolites (lumacaftor, ivacaftor, ivacaftor-M1, and ivacaftor-M6). PPK analysis was performed using Monolix software. A large interindividual variability was observed. The main sources of interpatient variability identified were patient bodyweight and hepatic function (aspartate aminotransferase). Forced expiratory volume in the first second (FEV1) was statistically associated with the level of exposure to ivacaftor after 48 weeks of treatment. This study is the first analysis of lumacaftor/ivacaftor PPK in children with CF. These data suggest that dose adjustment is required after identifying variability factors to optimize efficacy. The use of therapeutic drug monitoring as a basis for dose adjustment in children with CF may be useful.

Objective To examine the safety, efficacy and pharmacology of intravenous (IV), intramuscular (IM) and oral tranexamic acid (TXA) use in pregnant women. Design Randomised, open‐label trial. Setting Hospitals in Pakistan and Zambia. Population Women giving birth by caesarean section. Methods Women were randomised to receive 1 g IV, 1 g IM, 4 g oral TXA or no TXA. Adverse events in women and neonates were recorded. TXA concentration in whole blood was measured and the concentrations over time were examined with population pharmacokinetics. The relationship between drug exposure and D‐dimer was explored. The trial registration is NCT04274335. Main outcome measures Concentration of TXA in maternal blood. Results Of the 120 women included in the randomised safety study, there were no serious maternal or neonatal adverse events. TXA concentrations in 755 maternal blood and 87 cord blood samples were described by a two‐compartment model with one effect compartment linked by rate transfer constants. Maximum maternal concentrations were 46.9, 21.6 and 18.1 mg/L for IV, IM and oral administration, respectively, and 9.5, 7.9 and 9.1 mg/L in the neonates. The TXA response was modelled as an inhibitory effect on the D‐dimer production rate. The half‐maximal inhibitory concentration (IC50) was 7.5 mg/L and was achieved after 2.6, 6.4 and 47 minutes with IV, IM and oral administration of TXA, respectively. Conclusions Both IM and oral TXA are well tolerated. Oral TXA took about 1 hour to reach minimum therapeutic concentrations and would not be suitable for emergency treatment. Intramuscular TXA inhibits fibrinolysis within 10 minutes and may be a suitable alternative to IV.

Differences in disability perception between patients and care providers may impact outcomes. We aimed to explore differences in disability perception between patients and care providers in systemic sclerosis (SSc). We conducted a cross-sectional internet-based mirror survey. SSc patients participating in the online SPIN Cohort and care providers affiliated to 15 scientific societies were surveyed using the Cochin Scleroderma International Classification of Functioning, Disability and Health (ICF)-65 questionnaire, including 65 items (from 0 to 10), representing 9 domains of disa-bility. Mean differences between patients and care providers were calculated. Care providers’ characteristics associated with a mean difference ≥ 2 of 10 points were assessed in multivariate analysis. Answers were analysed for 109 patients and 105 care providers. Mean age of patients was 55.9 (14.7) years and disease duration was 10.1 (7.5) years. For all domains of the ICF-65, care providers’ rates were higher than those of patients. Mean difference was 2.4 (1.0) of 10 points. Care providers’ characteristics associated with this difference were organ-based specialty (OR=7.0 [2.3-21.2]), younger age (OR=2.7 [1.0-7.1]) and following patients with disease duration ≥ 5 years (OR=3.0 [1.1-8.7]). We found systematic differences in disability perception between patients and care providers in SSc. Keywords: systemic sclerosis; disability; activity limitations; patient-reported outcomes.

Aims Glucocorticoids are 1 of the primary treatments in paediatric kidney transplantation. The aims of this study were: (i) to build a population pharmacokinetics (PPK) model of free prednisolone, which is the active form of prednisone, in paediatric kidney transplant recipients; (ii) to identify covariates accounting for interindividual variability (IIV) of pharmacokinetics (PK) parameters; and (iii) to investigate drug exposure–safety relationships. Methods Ninety‐seven samples were obtained from 39 paediatric kidney transplant recipients (aged 3.4–17.2 years) in order to investigate prednisone PPK. We selected children receiving oral prednisone as part of their immunosuppressive regimen. A PPK analysis was performed using Monolix. Results A 1‐compartment model best described prednisolone concentrations. Large IIV was observed as prednisolone was undetectable at H12 in some patients but could still be detected at H24 in others. Both bodyweight and ciclosporin cotreatment influenced the PK. The clearance (CLU) and volume of distribution of free prednisolone allometrically scaled to 70 kg were 27.6 L/h and 101 L. Ciclosporin cotreatment decreased CLU by 67%. High blood pressure and new onset diabetes after transplantation were associated with daily free prednisolone exposure. Conclusion This study is the first analysis of prednisolone PPK in kidney‐transplanted children. Some of the IIV in the PK parameters was explained by bodyweight and ciclosporin cotreatment. These data suggest that dose adjustment is required after identifying variability factors to optimize efficacy and limit side effects. The use of therapeutic drug monitoring in kidney‐transplanted children may be useful, especially with respect to safety issues.