Summary Report of a Public Workshop: Case Studies of Multi-Regional Clinical Trial Incorporating Concept of the ICH E17 Guideline.

To further our understanding of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) E17 guideline and promote effective implementation, a public workshop was held in Japan by regulatory agency and industry representatives. In this workshop, important concepts explained in the ICH E17 guideline, such as intrinsic/extrinsic ethnic factors that influence treatment effects ("effect modifiers") and the holistic evaluation of consistency of treatment effect were actively discussed through case studies. The importance of holistic evaluation of consistency was recognized, and it was concluded that the evaluation and relevant discussion should be shared with regulatory authorities, sponsors, and broader stakeholders.

Characteristics of Asian Participation in Multi-regional Clinical Trials Reviewed for Drug Approval in Japan: Opportunities for Collaboration Between South-East Asia, East Asia, and Japan.

Although the percentage of multi-regional clinical trials (MRCTs) submitted for drug approval in Japan increased significantly since the 2007 publication of the regulatory guideline, "Basic principles on global clinical trials", strategic collaborations between Asian countries will be important to promote MRCTs in accordance with the ICH E17 guideline published in 2017. In this study, characteristics of MRCTs reviewed for drug approval in Japan, especially those with participation by South-East Asia and East Asia, were investigated to explore opportunities for collaborations on global drug development in Asia. More than 90% of reviewed trials were conducted as global MRCTs. In addition to Japan, South-East Asia has participated in various types of MRCTs in terms of total numbers of subjects and countries. However, South-East Asia participation was lower in large-size MRCTs (total sample size ≥ 1000) than in middle- (500 ≤ total sample size < 1000) and small-size MRCTs (total sample size < 500). Furthermore, similar clinical trials for the same indications to the MRCTs without South-East Asia were rarely conducted separately in South-East Asia. Participation of other Asian countries did not affect the percentage of Japanese subjects enrolled in an MRCT, but did significantly increase the percentage of participating Asian subjects. These results suggest that additional opportunities for collaboration on MRCTs may be possible between Japan and other Asian countries, especially more collaborations with South-East Asia in the large-size MRCTs. More data of Asian populations from MRCTs will be useful for exploring an important ethnic factor affecting drug response, and will provide a sound scientific basis in considering the application of the pooled data concept in Asia, as described in the ICH E17 guideline.

Use of Pharmacogenomics and Biomarkers in the Development of New Drugs for Alzheimer Disease in Japan.

PURPOSE: Pharmacogenomics (PGx) and biomarkers have been utilized for improving the benefit/risk ratios of drugs and the efficiency of drug development. In the development of drugs for Alzheimer disease (AD), a number of clinical trials have failed to demonstrate clinical efficacy. To overcome this circumstance, the importance of using PGx/biomarkers for enhancing recruitment into clinical trials and for evaluating the efficacy of treatments has been increasingly recognized. In this article, the current status and examples of the use of PGx/biomarkers in Japan for drug development are explained. METHODS: Guidelines, notifications, and administrative notices related to PGx/biomarkers were downloaded from the Web sites of the Pharmaceuticals and Medical Devices Agency (PMDA), the US Food and Drug Administration, and the European Medicines Agency. Data from clinical studies of AD drugs were obtained from the review reports of the PMDA. To analyze the current status of the use of PGx/biomarkers in Japan, "Issues to Consider in the Clinical Evaluation and Development of Drugs for Alzheimer's Disease (Interim Summary)" was also downloaded from PMDA Web site. FINDINGS: There are 2 major measures of utilizing PGx/biomarkers for drug development: (1) biomarker qualification and (2) companion diagnostics. Recently, the PMDA issued a number of guidelines and notifications for their practical use. Although examples of qualified PGx/biomarkers and approved companion diagnostics are limited at present, it is expected that the use of PGx/biomarkers for the development of drugs against AD would increase. IMPLICATIONS: For promoting the use of PGx/biomarkers in the development of drugs against AD, PGx/biomarkers should be qualified as early as possible. To that end, accumulating data on PGx/biomarkers from nonclinical or clinical trials and the concurrent development of reliable diagnostics in the early stage of the development process are indispensable. It is important to strengthen collaboration among the academia, industries, and regulatory agencies, followed by the establishment of an effective guideline in the area of AD.

Regulatory perspective on remaining challenges for utilization of pharmacogenomics-guided drug developments.

Pharmacogenomics-guided drug development has been implemented in practice in the last decade, resulting in increased labeling of drugs with pharmacogenomic information. However, there are still many challenges remaining in utilizing this process. Here, we describe such remaining challenges from the regulatory perspective, specifically focusing on sample collection, biomarker qualification, ethnic factors, codevelopment of companion diagnostics and means to provide drugs for off-target patients. To improve the situation, it is important to strengthen international harmonization and collaboration among academia, industries and regulatory agencies, followed by the establishment of an international guideline on this topic. Communication with a regulatory agency from an early stage of drug development is also a key to success.

Similarities and differences between US and Japan as to pharmacogenomic biomarker information in drug labels.

Pharmacogenomics (PGx) has been utilized as a tool to improve a drug's benefit/risk ratio and the efficiency of drug developments. In order to examine what factors are involved to determine the level of contexts (contents and descriptions) of drug-PGx biomarker information, we graded sections of Japanese package inserts and US drug labels into six levels according to the importance of cautions in regards to clinical practice and compared similarities and differences of the contexts between the two countries. Out of 54 contexts identified, 33 (61%) were graded differently between Japan and the US. The different contexts were mainly related to metabolizing enzymes used in terms of safety, therapeutic areas other than oncology, outcome before 1993, Japan-based companies having marketing authorization and no PGx data on the Japanese population. We describe the potential reasons that could lead to the differences between the two countries such as genetic differences and quantitative evidence in the Japanese population, and also discuss future perspectives to improve PGx utilization in clinical practices in Japan.

Mechanisms of substrate transport-induced clustering of a glial glutamate transporter GLT-1 in astroglial-neuronal cultures.

Glutamate uptake by the Na(+)-dependent glutamate transporter GLT-1, which is predominantly expressed in astrocytes, is crucial for regulating glutamate concentration at the synaptic cleft and achieving proper excitatory neurotransmission. A body of evidence suggests that GLT-1 constitutively traffics between the plasma membrane and endosomes via an endocytosis/recycling pathway, and forms a cluster. Here, we report substrate transport via GLT-1-induced formation of GLT-1 cluster accompanied by intracellular trafficking in rat astroglial-neuronal cultures. We constructed a recombinant adenovirus expressing enhanced green fluorescence protein (EGFP)-tagged GLT-1. Adenoviral infection resulted in the expression of functional GLT-1-EGFP preferentially in astrocytes, partly as clusters. Treatment with glutamate, but not N-methyl-D-aspartate, dramatically increased the number of GLT-1 clusters within 1 h. The estimated EC(50) value of glutamate was 240 microm. In addition, glutamate decreased the cell surface expression and increased the intracellular expression of GLT-1. The GLT-1 clusters were found in early and recycling endosomes and partly in lysosomes, and were inhibited by blockade of endocytotic pathways. Ionotropic and metabotropic glutamate receptor antagonists had no effect on glutamate-induced GLT-1 clustering. The non-transportable glutamate uptake inhibitors (2S,3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate and dihydrokainate, as well as Na(+)-free conditions, prevented the glutamate-induced GLT-1 clustering, whereas the competitive substrates, aspartate and L-trans-pyrrolidine-2,4-dicarboxylate, induced GLT-1 clustering. Furthermore, the Na(+)/K(+)-ATPase inhibitor, ouabain, and the Na(+) ionophores, gramicidin and monensin, produced GLT-1 clustering. Modulators of intracellular Ca(2+)signaling or membrane depolarization had no effect on GLT-1 clustering. Taken together, these results suggest that Na(+) influx associated with GLT-1 substrate transport triggers the formation of GLT-1 clusters accompanied by intracellular trafficking via endocytotic pathways in astrocytes.

Characterization of the tritium-labeled analog of L-threo-beta-benzyloxyaspartate binding to glutamate transporters.

L-Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Termination of glutamate receptor activation and maintenance of low extracellular glutamate concentrations are primarily achieved by glutamate transporters (excitatory amino acid transporters 1-5, EAATs1-5) located on both the nerve endings and the surrounding glial cells. To identify the physiological roles of each subtype, subtype-selective EAAT ligands are required. In this study, we developed a binding assay system to characterize EAAT ligands for all EAAT subtypes. We recently synthesized novel analogs of threo-beta-benzyloxyaspartate (TBOA) and reported that they blocked glutamate uptake by EAATs 1-5 much more potently than TBOA. The strong inhibitory activity of the TBOA analogs suggested that they would be suitable to use as radioisotope-labeled ligands, and we therefore synthesized a tritiated derivative of (2S,3S)-3-{3-[4-ethylbenzoylamino]benzyloxy}aspartate ([3H]ETB-TBOA). [3H]ETB-TBOA showed significant high-affinity specific binding to EAAT-transfected COS-1 cell membranes with each EAAT subtype. The Hill coefficient for the Na+-dependence of [3H]ETB-TBOA binding revealed a single class of noncooperative binding sites for Na+, suggesting that Na+ binding in the ligand binding step is different from Na+ binding in the substrate uptake process. The binding was displaced by known substrates and blockers. The rank order of inhibition by these compounds was consistent with glutamate uptake assay results reported previously. Thus, the [3H]ETB-TBOA binding assay will be useful to screen novel EAAT ligands for all EAAT subtypes.