Pascal Espié

Allometric scaling is widely used to predict human pharmacokinetic parameters from preclinical species, and many different approaches have been proposed over the years to improve its predictive performance. Nevertheless, prediction errors are commonly observed in the practical application of simple allometry, for example, in cases where the hepatic metabolic clearance is mainly determined by enzyme activities, which do not scale allometrically across species. Therefore, if good correlation was noted for some drugs, poor correlation was observed for others, highlighting the need for other conceptual approaches. Physiologically based pharmacokinetic (PBPK) models are now a well-established approach to conduct extrapolations across species and to generate simulations of pharmacokinetic profiles under various physiological conditions. While conventional pharmacokinetic models are defined by drug-related data themselves, PBPK models have richer information content and integrate information from various sources, including drug-dependent, physiological, and biological parameters as they vary in between species, subjects, or with age and disease state. Therefore, the biological and mechanistic bases of PBPK models allow the extrapolation of the kinetic behavior of drugs with regard to dose, route, and species. In addition, by providing a link between tissue concentrations and toxicological or pharmacological effects, PBPK modeling represents a framework for mechanistic pharmacokinetic-pharmacodynamic models.

Like any other drugs, antiallergic medications can be associated with large inter- and intraindividual variability in their disposition. The best-documented examples belong to the H1 antihistamines. Variable drugs are more likely to show unpredictable therapeutic response with both increased risks of side effects and subtherapeutic dosing in individual subjects. This article will review the main factors contributing to intervariability in pharmacokinetics with a special emphasis on gender differences, genetic polymorphism, and food habits.

CONTEXT: The CD40-CD154 co-stimulatory pathway plays an important role in the pathogenesis of Graves disease (GD) by promoting autoreactive B-cell activation. OBJECTIVE: Evaluate efficacy and safety of a human, blocking, nondepleting anti-CD40 monoclonal antibody, iscalimab, in hyperthyroid patients with GD. DESIGN: Open-label, phase II proof-of-concept study. SETTING: Multicenter. PATIENTS: Fifteen with GD. INTERVENTION: Patients received 5 doses of iscalimab at 10 mg/kg intravenously over 12 weeks. MAIN OUTCOME MEASURES: Thyroid-related hormones and autoantibodies, plasma soluble CD40, free CD40 on B cells, soluble CXCL13, pharmacokinetics, and safety were assessed. RESULTS: The iscalimab intervention resulted in complete CD40 engagement for up to 20 weeks. A clinical response and biochemical euthyroidism was observed in 7 of 15 (47%) patients. Free and total triiodothyronine and thyroxine normalized in 7 patients who did not receive any rescue medication with antithyroid drugs (ATD), and 2/15 (13.3%) showed normal thyrotropin. Six (40%) patients required ATD. Four of 7 responders relapsed after treatment completion. Serum concentrations of thyrotropin receptor autoantibodies (TSH-R-Ab) significantly declined in all patients (mean 15.3 IU/L vs 4.0 IU/L, 66% reduction; P < 0.001) and TSH-R-Ab levels normalized in 4 (27%). Thyroperoxidase and thyroglobulin autoantibodies significantly decreased in responders. Iscalimab rapidly reduced serum CXCL13 concentrations (P < 0.001). Twelve (80.0%) patients reported at least 1 adverse event (AE). All treatment-related AE were mild or moderate and resolved by end of the study. CONCLUSION: Iscalimab was generally safe and clinically effective in a subgroup of hyperthyroid GD patients. The potential therapeutic benefit of iscalimab should be further tested.