3D liver models in tissue engineering and toxicology

In her thesis, Viktoriia Starokozhko developed new and improved existing liver models for the use in tissue engineering and toxicology. One of the models she described and used are liver slices (PCLS), a mini-organ model for the liver. PCLS are used already for many years in various fields of pharmacology and toxicology. However, their application is limited by their short life span. In this thesis it was shown that viability and functionality of PCLS can be prolonged to 5 days by using enriched media, which will allow performance of subchronic toxicity studies. The application of PCLS in toxicology studies was successfully demonstrated for drug-induced cholestasis.Another topic described in this thesis is a liver-on-a-chip or bioartificial liver (BAL). To date, the only effective treatment available for patients with acute liver failure is liver transplantation. However, orthotopic transplantation is limited by the shortage of liver donors. Therefore, creation of a BAL has been proposed as an alternative approach to whole liver transplantation, or as a temporary solution, reducing the mortality rate of patients on the waiting list. In this thesis, the challenges on the road to the development of such a BAL are described. Moreover, a prototype of an extracorporeal BAL device is presented based on human induced pluripotent stem cells, which considered to be the most promising source for the generation of human liver cells. Fully functional liver cells were derived from these stem cells, which is a major step forward in liver tissue engineering. The application of these human liver models significantly reduces the use of animals and improves prediction of toxicity for man

Biomarker qualification at the European Medicines Agency: a review of biomarker qualification procedures from 2008 to 2020

Regulatory qualification of biomarkers facilitates their harmonised use across drug developers, enabling more personalised medicine. This study reviews various aspects of the European Medicines Agency's (EMA) biomarker qualification procedure, including frequency and outcome, common challenges, and biomarker characteristics. Our findings provide insights into EMA's biomarker qualification process and will thereby support future applications. All biomarker-related "Qualification of Novel Methodologies for Medicine Development" procedures that started from 2008 to 2020 were included. Procedural data were extracted from relevant documents and analysed descriptively. In total, 86 biomarker qualification procedures were identified, of which 13 resulted in qualified biomarkers. Whereas initially many biomarker qualification procedures were linked to a single company and specific drug development program, a shift was observed to qualification efforts by consortia. Most biomarkers were proposed (n=45) and qualified (n=9) for use in patient selection, stratification, and enrichment, followed by efficacy biomarkers (37 proposed, 4 qualified). Overall, many issues were raised during qualification procedures, mostly related to biomarker properties and assay validation (in 79% and 77% of all procedures, respectively). Issues related to the proposed context of use and rationale were least common, yet, were still raised in 54% of all procedures. While few qualified biomarkers are currently available, procedures focus increasingly on biomarkers for general use instead of those linked to specific drug compounds. The issues raised during qualification procedures illustrate the thorough discussions taking place between applicants and regulators - highlighting aspects that need careful consideration and underlining the importance of an appropriate validation strategy

Rat precision-cut liver slices predict drug-induced cholestatic injury

Drug-induced cholestasis (DIC) is one of the leading manifestations of drug-induced liver injury (DILI). As the underlying mechanisms for DIC are not fully known and specific and predictive biomarkers and pre-clinical models are lacking, the occurrence of DIC is often only reported when the drug has been approved for registration. Therefore, appropriate models that predict the cholestatic potential of drug candidates and/or provide insight into the mechanism of DIC are highly needed. We investigated the application of rat precision-cut liver slices (PCLS) to predict DIC, using several biomarkers of cholestasis: hepatocyte viability, intracellular accumulation of total as well as individual bile acids and changes in the expression of genes known to play a role in cholestasis. Rat PCLS exposed to the cholestatic drugs chlorpromazine, cyclosporine A and glibenclamide for 48 h in the presence of a 60 μM physiological bile acid (BA) mix reflected various changes associated with cholestasis, such as decrease in hepatocyte viability, accumulation and changes in the composition of BA and changes in the gene expression of Fxr, Bsep and Ntcp. The toxicity of the drugs was correlated with the accumulation of BA, and especially DCA and CDCA and their conjugates, but to a different extent for different drugs, indicating that BA toxicity is not the only cause for the toxicity of cholestatic drugs. Moreover, our study supports the use of several biomarkers to test drugs for DIC. In conclusion, our results indicate that PCLS may represent a physiological and valuable model to identify cholestatic drugs and provide insight into the mechanisms underlying DIC

Strengthening regulatory science in academia:STARS, an EU initiative to bridge the translational gap

Truly disruptive medicine innovation and new treatment paradigms tend to start in non-commercial research institutions. However, the lack of mutual understanding between medicine developers and regulators when it comes to medicine development significantly delays or even prevents the access of patients to these innovations. Here, we outline what regulatory-related barriers hamper the translational development of novel products or new treatment paradigms initiated in academia, and propose key steps towards improved regulatory dialogue among academia, funding bodies and regulatory authorities. Moreover, we briefly describe how the STARS (Strengthening Training of Academia in Regulatory Science) project aims to reach out to medicine innovators in academia to bridge the regulatory knowledge gap and enhance this dialogue to facilitate the implementation of academic research findings in clinical practice