Predicting clinically significant drug interactions during drug development is a challenge for the pharmaceutical industry and regulatory agencies. Since the publication of the US Food and Drug Administration's (FDA's) first in vitro and in vivo drug interaction guidance documents in 1997 and 1999, researchers and clinicians have gained a better understanding of drug interactions. This knowledge has enabled the FDA and the industry to progress and begin to overcome these challenges. The FDA has continued its efforts to evaluate methodologies to study drug interactions and communicate recommendations regarding the conduct of drug interaction studies, particularly for CYP-based and transporter-based drug interactions, to the pharmaceutical industry. A drug interaction Web site was established to document the FDA's current understanding of drug interactions (http://www.fda.gov/cder/drug/drugInteractions/default.htm). This report provides an overview of the evolution of the drug interaction guidances, includes a synopsis of the steps taken by the FDA to revise the original drug interaction guidance documents, and summarizes and highlights updated sections in the current guidance document, Drug Interaction Studies-Study Design, Data Analysis, and Implications for Dosing and Labeling.

, WI *This article represents the scientific opinion of many experts and, in particular, is derived from a series of workshops held under the auspices of the Federation International Pharmaceutique (FIP) and cosponsored by the Royal Pharmaceutical Society (UK), the Bundesverband der Pharmazeutischen Industrie (BPI), Colloquium Pharmaceuticum (Germany), the American Association of Pharmaceutical Scientists (AAPS, US), and the US Food and Drug Administration. It is

The value of quantitative thinking in drug development and regulatory review is increasingly being appreciated. Modeling and simulation of data pertaining to pharmacokinetic, pharmacodynamic, and disease progression is often referred to as the pharmacometrics analyses. The objective of the current report is to assess the role of pharmacometrics at the US Food and Drug Administration (FDA) in making drug approval and labeling decisions. The New Drug Applications (NDAs) submitted between 2000 and 2004 to the Cardio-renal, Oncology, and Neuropharmacology drug products divisions were surveyed. For those NDA reviews that included a pharmacometrics consultation, the clinical pharmacology scientists ranked the impact on the regulatory decision(s). Of about a total of 244 NDAs, 42 included a pharmacometrics component. Review of NDAs involved independent, quantitative evaluation by FDA pharmacometricians, even when such analysis was not conducted by the sponsor. Pharmacometric analyses were pivotal in regulatory decision making in more than half of the 42 NDAs. Of the 14 reviews that were pivotal to approval related decisions, 5 identified the need for additional trials, whereas 6 reduced the burden of conducting additional trials. Collaboration among the FDA clinical pharmacology, medical, and statistical reviewers and effective communication with the sponsors was critical for the impact to occur. The survey and the case studies emphasize the need for early interaction between the FDA and sponsors to plan the development more efficiently by appreciating the regulatory expectations better.

Upadacitinib is a Janus kinase 1 inhibitor under development for the treatment of several inflammatory disorders including rheumatoid arthritis (RA). Upadacitinib was administered in the phase 2 RA trials primarily as twice-daily regimens of an immediate-release (IR) formulation. The upadacitinib extended-release (ER) formulation was developed to enable once-daily dosing. In the present study, upadacitinib pharmacokinetics were characterized after the administration of single and multiple once-daily doses of the ER formulation in healthy subjects relative to single and multiple twice-daily doses of the IR formulation. Increase in upadacitinib exposure was dose-proportional over the evaluated 15- to 30-mg ER dose range. Single 15- and 30-mg ER doses provided equivalent AUC compared with single 12- and 24-mg IR doses, respectively. A high-fat breakfast increased upadacitinib ER C and AUC by only 20% and 17%, respectively, relative to fasting conditions. The median time to peak plasma concentrations was 2 to 4 hours for the ER formulation, and steady state was achieved by day 4 of once-daily dosing. Doses of 15 and 30 mg once daily using the ER formulation provided equivalent AUC , comparable C and C , and a fluctuation index over a 24-hour period at steady state similar to 6 and 12 mg twice daily, respectively, using the IR formulation. These results supported the use of upadacitinib 15- and 30-mg doses of the ER formulation in the phase 3 trials in RA.