The International Council for Harmonisation revised the E14 guideline through the questions and answers process to allow concentration-QTc (C-QTc) modeling to be used as the primary analysis for assessing the QTc interval prolongation risk of new drugs. A well-designed and conducted QTc assessment based on C-QTc modeling in early phase 1 studies can be an alternative approach to a thorough QT study for some drugs to reliably exclude clinically relevant QTc effects. This white paper provides recommendations on how to plan and conduct a definitive QTc assessment of a drug using C-QTc modeling in early phase clinical pharmacology and thorough QT studies. Topics included are: important study design features in a phase 1 study; modeling objectives and approach; exploratory plots; the pre-specified linear mixed effects model; general principles for model development and evaluation; and expectations for modeling analysis plans and reports. The recommendations are based on current best modeling practices, scientific literature and personal experiences of the authors. These recommendations are expected to evolve as their implementation during drug development provides additional data and with advances in analytical methodology.
The criterion for assessing whether a drug prolongs QT as described in the International Conference on Harmonization topic E14 guideline does not explicitly account for individual drug concentrations. The authors' experience with reviewing QT studies indicates that understanding the relationship, if any, between individual drug concentration and QT change provides important additional information to support regulatory decision making. Therefore, regulatory reviews of "thorough QT" studies routinely include a characterization of the concentration-QT relationship. The authors provide examples to illustrate how the concentration-QT relationship has been used to plan and interpret the thorough QT study, to evaluate QT risk for drugs that have no thorough QT studies, to assess QT risk in subpopulations, to make dose adjustments, and to write informative drug labels.
To increase our understanding of important subject characteristics and design variables affecting the performance of oral moxifloxacin in thorough QT studies, population pharmacokinetic and concentration-QTc models were developed by pooling data from 20 studies. A 1-compartment model with first-order elimination described the pharmacokinetics. Absorption delay was modeled using 8 transit compartments. Mean (95% confidence interval) values for oral clearance, apparent volume of distribution, the first-order absorption rate constant, and mean transit time were 11.7 (11.5-11.9) L/h, 147 (144-150) L, 1.9 (1.7-2.1) 1/h, and 0.3 (0.28-0.34) hours, respectively. Overencapsulating the moxifloxacin tablet increased mean transit time by 138% and delayed time to maximum concentration by 0.5 hours but had a minimal effect on overall exposure. Administration with food decreased absorption rate constant by 27%. Women had higher moxifloxacin exposure compared with men, which was explained by lower body weights. A linear model described the concentration-QTc relationship with a mean slope of 3.1 (2.8-3.3) milliseconds per µg/mL moxifloxacin. Mean slopes for individual studies ranged from 1.6 to 4.8 milliseconds per µg/mL. Hysteresis between moxifloxacin plasma concentrations and QTc was modest, and incorporating this delay did not result in a different slope (3.3 milliseconds per µg/mL). There were no differences in slope estimates between men and women or among race categories.
Pharmacometric analyses have become an increasingly important component of New Drug Application (NDA) and Biological License Application (BLA) submissions to the US FDA to support drug approval, labelling and trial design decisions. Pharmacometrics is defined as a science that quantifies drug, disease and trial information to aid drug development, therapeutic decisions and/or regulatory decisions. In this report, we present the results of a survey evaluating the impact of pharmacometric analyses on regulatory decisions for 198 submissions during the period from 2000 to 2008. Pharmacometric review of NDAs included independent, quantitative analyses by FDA pharmacometricians, even when such analysis was not conducted by the sponsor, as well as evaluation of the sponsor's report. During 2000-2008, the number of reviews with pharmacometric analyses increased dramatically and the number of reviews with an impact on approval and labelling also increased in a similar fashion. We also present the impact of pharmacometric analyses on selection of paediatric dosing regimens, approval of regimens that had not been directly studied in clinical trials and provision of evidence of effectiveness to support a single pivotal trial. Case studies are presented to better illustrate the role of pharmacometric analyses in regulatory decision making.
Purpose: On December 15, 2008, the US Food and Drug Administration approved plerixafor (Mozobil®; Genzyme Corp.), a new small-molecule inhibitor of the CXCR4 chemokine receptor, for use in combination with granulocyte colony-stimulating factor (G-CSF) to mobilize hematopoietic stem cells (HSC) to the peripheral blood for collection and subsequent autologous transplantation in patients with non-Hodgkin’s lymphoma (NHL) and multiple myeloma (MM). This summary reviews the database supporting this approval. Experimental Design: The safety and efficacy of plerixafor were demonstrated by 2 multicenter, randomized, placebo-controlled studies in patients with NHL and MM who were eligible for autologous HSC transplantation. The primary efficacy end points were the collection of ≧5 × 106 CD34+ cells/kg from the peripheral blood in 4 or fewer apheresis sessions in patients with NHL or ≧6 × 106 CD34+ cells/kg from the peripheral blood in 2 or fewer apheresis sessions in patients with MM. Results: The 2 randomized studies combined enrolled 600 patients (298 with NHL and 302 with MM). Fifty-nine percent of patients with NHL who were mobilized with G-CSF and plerixafor had peripheral blood HSC collections of ≧5 × 106 CD34+ cells/kg in 4 or fewer apheresis sessions, compared with 20% of patients with NHL who were mobilized with G-CSF and placebo (p < 0.001). Seventy-two percent of patients with MM who were mobilized with Mozobil and G-CSF had peripheral blood HSC collections of ≧6 × 106 CD34+ cells/kg in 2 or fewer apheresis sessions, compared with 34% of patients with MM who were mobilized with placebo and G-CSF (p < 0.001). Common adverse reactions included diarrhea, nausea, vomiting, flatulence, injection site reactions, fatigue, arthralgia, headache, dizziness, and insomnia. Conclusions: This report describes the Food and Drug Administration review supporting the approval of plerixafor.
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