Metabolites in safety testing (MIST) and in vivo metabolism

 

Unexpected toxicities and safety issues are a major cause of attrition in preclinical and clinical drug development programs. Identification of the small molecule parent drug’s metabolites in human and assesing their safety comprises an important step in evaluation of the lead compounds acceptance for further development. Whilst the parent drug is to be tested in various animal in vivo as well as in vitro toxicity and safety models, its metabolites may need to be tested for toxicity as well. This can be due to possible differences in metabolic profiles between humans and used animal species.

These differences can be either presence of unique metabolites in humans compared to the used animal species or disproportionally higher presence of the metabolites may significantly differ in humans from those occuring in the used animal models. The importance of preclinical MIST is also explained in regulatory guidelines like FDA Guidance to the Industry document, 2008, OECD Toxicokinetic guideline “Draft proposal for a revised TG 417: Toxicokinetics” (draft), 2008) and ICH M3 R2 Guidance on Nonclinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for PharmaceuticalsFinalised Guideline, 2009 . The key aspect of this guidance relates to the testing of the possibly differing metabolites in various species for safety using the various in vitro and in vivo tests.

Typically in in vivo studies, the metabolites are detected from plasma and urine, sometime also from solid tissues, like liver, kidney and brains. The metabolites in excreted matrices, like urine, are typically phase II conjugates, whilst the metabolites in the other matrices are predominantly phase I oxidation/reduction metabolites. In vivo metabolism study should be precluded by an in vitro metabolism studies and can be part the of the more elucidative pharmacokinetics study, where the bioanalytical quantitation is done both to the administered parent compound as well as the metabolites identified in the in vitro microsomal and hepactocyte studies. However, the whole in vivo organism is obviously more complex system than the in vitro metabolism systems and often differences in the metabolite profile are observed. In in vivo metabolism studies, the sample matrix poses sometimes challenges for the analytics, like urine is typically more challenging matrix than plasma or homogenized tissues.

Our expertise in MIST

We provide a variety of expertise and test systems related to the MIST. This includes the identification of the metabolites and their stabilities in several species with in vitro and in vivo settings as well as characterisation of reactive metabolites. We offer end-to-end in vivo rodent and non-rodent DMPK solutions, where the pharmacokinetics of the parent compound and its metabolites are quantitated from plasma, different tissues as well as form urine and faeces collected form special metabolic cages >>see more on our pharmacokinetics expertise. Analysis of the in vivo metabolites requires more specific and sensitive instrumentation analysis, for which we are fully equipped in our laboratories (UPLC-TOF/MS instrumentation in addition to UPLC-QqQ MS/MS).

We provide also tailored studies, where the in vivo metabolism and pharmacokinetics profiling is combined with early toxicity observations >>more on our in vivo toxicology and safety expertise. Since we conduct all the in vivo and bioanalytics and metabolism studies in our own laboratories, we are able to do very rapid turnaround times for these studies.

In addition to the metabolism related in vivo safety studies, we also provide various in vitro toxicology studies (viability, membrane integrity, respiratory chain activity, lysosomal activity, apoptosis) in various cell models, including specific hepatocyte cells which are viral transfected to express the particular P450 CYP enzyme involved in the phase I metabolism. This model provide in vitro safety assessment of both the parent compound as well as its phase I metabolites.

Reactive metabolites, ie metabolites that can form covalent adducts with cells nucleic acids and proteins, are in central focus of the metabolism related safety concerns. We provide unique expertise in detecting reactive metabolites >> read more from this link.

Further, following synthesis of the metabolites, we can test their safety and toxicity in various in vitro and in vivo models.

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