Metabolite Bioanalysis in Drug Development: Recommendations from the IQ Consortium Metabolite Bioanalysis Working Group

The Importance of Murine Models in Determining In Vivo Pharmacokinetics, Safety, and Efficacy in Antimalarial Drug Discovery

New chemical entities are constantly being investigated towards antimalarial drug discovery, and they require animal models for toxicity and efficacy testing. Murine models show physiological similarities to humans and are therefore indispensable in the search for novel antimalarial drugs. They provide a preclinical basis (following in vitro assessments of newly identified lead compounds) for further assessment in the drug development pipeline. Specific mouse strains, non-humanized and humanized, have successfully been infected with rodent Plasmodium species and the human Plasmodium species, respectively. Infected mice provide a platform for the assessment of treatment options being sought. In vivo pharmacokinetic evaluations are necessary when determining the fate of potential antimalarials in addition to the efficacy assessment of these chemical entities. This review describes the role of murine models in the drug development pipeline. It also explains some in vivo pharmacokinetic, safety, and efficacy parameters necessary for making appropriate choices of lead compounds in antimalarial drug discovery. Despite the advantages of murine models in antimalarial drug discovery, certain limitations are also highlighted.

Cross-industry demonstration of the validity of the mixed matrix method for the assessment of cross-species exposure coverage of human circulating drug metabolites

The mixed matrix method (MmM) is a widely used approach by the pharmaceutical industry for early assessment of whether exposures to major human circulating metabolites, of traditional small-molecule drugs, are adequately covered by the species used for toxicology assessment, which is a key requirement of the safety testing of drug metabolites (metabolites in safety testing guidelines). However, questions remain regarding its accuracy and utility in replacing conventional bioanalytical approaches. Furthermore, the available literature on the topic is not fully consistent in terms of how the assay should be conducted. As a result, encouraged by health authority advice on this topic, a cross-industry group under the European Federation of Pharmaceutical Industries and Associations was formed to: (1) further investigate the MmM accuracy, including a robust statistical analysis covering a diverse chemical space of commercially available drugs and drug candidates as well as their metabolites; (2) propose recommendations for best practice including a decision tree that the industry should consider when using the MmM; and (3) discuss whether the MmM could be used to support metabolites in safety testing assessment and could potentially be included into new drug application submissions without the need for additional measurements using the conventional bioanalytical approach. The outcome of this European Federation of Pharmaceutical Industries and Associations assessment shows that MmM measured exposure ratios of 1.9 and 1.4 are statistically sufficient to demonstrate adequate exposure coverage of human metabolites above 50% or between 10% and 50% of drug-related exposure, respectively, by toxicology species. The aim is to encourage both industry and regulatory agencies to consider MmM as an acceptable approach to compare major human circulating metabolite exposures across species. SIGNIFICANCE STATEMENT: The outcome of our mixed matrix method assessment showed that measured exposure ratios of 1.9 and 1.4 are adequate to demonstrate coverage of human metabolites above or below 50% drug-related exposure by toxicology species. Recommendations for best practice and a decision tree for conducting metabolites in safety testing evaluations are proposed. Our investigations show that mixed matrix method data are sufficiently robust for the intended purpose and that the assay provides an opportunity to streamline drug development and reduce the need for resource-intensive bioanalysis and certain animal studies.

The Current State of Biotransformation Science - Industry Survey of In Vitro and In Vivo Practices, Clinical Translation, and Future Trends

Embedded within the field of drug metabolism and pharmacokinetics (DMPK), biotransformation is a discipline that studies the origins, disposition, and structural identity of metabolites to provide a comprehensive safety assessment, including the assessment of exposure coverage in toxicological species. Spanning discovery and development, metabolite identification (metID) scientists employ various strategies and tools to address stage-specific questions aimed at guiding the maturation of early chemical matter into drug candidates. During this process, the identity of major (and minor) circulating human metabolites is ascertained to comply with the regulatory requirements such as the Metabolites in Safety Testing (MIST) guidance. Through the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ), the "Translatability of MetID In Vitro Systems Working Group" was created within the Translational and ADME Sciences Leadership Group. The remit of this group was to objectively determine how accurate commonly employed in vitro systems have been with respect to prediction of circulating human metabolites, both qualitatively and quantitatively. A survey composed of 34 questions was conducted across 26 pharmaceutical companies to obtain a foundational understanding of current metID practices, preclinically and clinically, as well as to provide perspective on how successful these practices have been at predicting circulating human metabolites. The results of this survey are presented as an initial snapshot of current industry-based metID practices, including our perspective on how a harmonized framework for the conduct of in vitro metID studies could be established. Future perspectives from current practices to emerging advances with greater translational capability are also provided.