BackgroundEmicizumab (ACE910) is a bispecific antibody mimicking the cofactor function of activated coagulation factor VIII. In phase I–I/II studies, emicizumab reduced the bleeding frequency in patients with severe hemophilia A, regardless of the presence of factor VIII inhibitors, at once-weekly subcutaneous doses of 0.3, 1, and 3 mg/kg.MethodsUsing the phase I–I/II study data, population pharmacokinetic and repeated time-to-event (RTTE) modeling were performed to quantitatively characterize the relationship between the pharmacokinetics of emicizumab and reduction in bleeding frequency. Simulations were then performed to identify the minimal exposure expected to achieve zero bleeding events for 1 year in at least 50% of patients and to select the dosing regimens to be tested in phase III studies.ResultsThe RTTE model adequately predicted the bleeding onset over time as a function of plasma emicizumab concentration. Simulations suggested that plasma emicizumab concentrations of ≥  45 μg/mL should result in zero bleeding events for 1 year in at least 50% of patients. This efficacious exposure provided the basis for selecting previously untested dosing regimens of 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks, and 6 mg/kg every 4 weeks for phase III studies.ConclusionsA pharmacometric approach guided the phase III dose selection of emicizumab in hemophilia A, without conducting a conventional dose-finding study. Phase III studies with the selected dosing regimens are currently ongoing. This case study indicates that a pharmacometric approach can substitute for a conventional dose-finding study in rare diseases and will streamline the drug development process.Electronic supplementary materialThe online version of this article (10.1007/s40262-017-0616-3) contains supplementary material, which is available to authorized users.

Ethnic evaluation of the pharmacokinetics and safety of new drugs is required in Japan before implementing bridging or joining global studies. As therapeutic monoclonal antibodies (mAbs) show limited ethnic differences, their pharmacokinetics and safety in Japanese individuals could be estimated from prior non-Japanese studies. Therefore, there is potential to re-evaluate the development program for mAbs in Japan. We reviewed the pharmacokinetics of mAbs approved in Japan. Although some differences had been observed in pharmacokinetics of mAbs between Japanese and non-Japanese populations (mainly Caucasians), these differences were attributed to differences of body weight and/or antigen levels. Moreover, the influential factors can be estimated without conducting regional pharmacokinetic/safety studies. The pharmacokinetics of some mAbs is presumably non-linear and show differences between healthy volunteers and patients because of differences in antigen levels. However, for 10/24 mAbs approved in Japan, Japanese healthy volunteer studies were conducted before the patient studies. Additionally, for the mAbs that showed ethnic differences in pharmacokinetics, the doses selected in subsequent patient studies were the same as the doses approved in the United States. In this review, we discuss new drug development strategies in various regions, and assess the need for regional pharmacokinetics/safety studies before joining global studies.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Nicorandil injection is used for unstable angina and for acute heart failure in Japan. • The pharmacokinetics of nicorandil following oral administration have been described in healthy subjects. WHAT THIS STUDY ADDS • This paper describes the differences in nicorandil pharmacokinetics between healthy subjects and acute heart failure patients. • A population pharmacokinetic‐pharmacodynamic model for nicorandil in acute heart failure patients is described using pulmonary artery wedge pressure as the biomarker. • A rational guide for initial dosing of nicorandil to achieve a target effect on pulmonary artery wedge pressure was based on pharmacokinetic and pharmacodynamic principles. AIMS The aims of the study were 1) to evaluate the pharmacokinetics of nicorandil in healthy subjects and acute heart failure (AHF) patients and 2) to evaluate the exposure‐response relationship with pulmonary arterial wedge pressure (PAWP) in AHF patients and to predict an appropriate dosing regimen for nicorandil. METHODS Based on the data from two healthy volunteer and three AHF patient studies, models were developed to characterize the pharmacokinetics and pharmacodynamics of nicorandil. PAWP was used as the pharmacodynamic variable. An asymptotic exponential disease progression model was used to account for time dependent changes in PAWP that were not explained by nicorandil exposure. The modelling was performed using NONMEM version V. RESULTS The pharmacokinetics of nicorandil were characterized by a two‐compartment model with linear elimination. CL, V1 and V2 in AHF patients were 1.96, 1.39 and 4.06 times greater than in healthy subjects. Predicted plasma concentrations were assumed to have an immediate concentration effect relationship on PAWP. An inhibitory Emax model with Emax of −11.7 mmHg and EC50 of 423 µg l−1 was considered the best relationship between nicorandil concentrations and PAWP. PAWP decreased independently of nicorandil exposure. This drug independent decline was described by an asymptotic decrease of 6.1 mmHg with a half‐life of 5.3 h. CONCLUSIONS AHF patients have higher clearance and initial distribution volume of nicorandil compared with healthy subjects. The median target nicorandil concentration to decrease PAWP by 30% is predicted to be 748 µg l−1, indicating that a loading dose of 200 µg kg−1 and a maintenance dose of 400 µg kg−1 h−1 would be appropriate for the initial treatment of AHF.

A population pharmacokinetics model of erlotinib was developed and validated in Japanese patients. There was no relationship between exposure of erlotinib before the occurrence of ILD-like events and the occurrence of ILD-like events when erlotinib was administered at the same dosage. The high plasma concentration of erlotinib reported in patients after the onset of ILD-like events may be explained by CL/F decrease which occurs along with increasing levels of AGP which was identified as a covariate for CL/F.

Neither the pharmacokinetics nor the pharmacodynamics of tofogliflozin was affected by any of the anti-T2DM drugs evaluated in this study, nor was the pharmacokinetics of any of the anti-T2DM drugs affected by tofogliflozin in healthy male volunteers.