(M0930-10-68) Focus on Efficacy: In Vitro Tissue Models for Preclinical Research

Purpose: During the development of new therapeutics or medical devices, proof of efficacy is of crucial importance. Currently, animal models are largely used for this purpose, but their metabolism can differ significantly from that of humans. This limits their predictive power, which explains, among other things, the high error rates of up to 95% during translation from the preclinical to the clinical development phases. In addition, animal-based studies often result in false predictions in the context of infection studies, as humans are the only natural host for many pathogens. Combined with the current sociopolitical shift in thinking about animal testing, 3Rs-compliant regulations in the EU, and the FDA's pioneering role in preclinical drug testing strategies, non-animal study tools are the future. In this context, cell-based in vitro models of human organs provide an alternative test system for preclinical drug efficacy testing.

Methods: To assess the efficacy of novel pharmaceutical ingredients, drug classes or formulations, we develop human-specific in vitro models for the most relevant barrier organs such as the skin, the gastrointestinal tract, the eye, the respiratory tract as well as the blood-brain barrier. The basis of our models are human primary cells like intestinal organoids or hiPSC-derived cell entities combined with distinct classes of biomatrices as scaffold structures. Tissue-specific endpoints are analyzed by e.g., impedance spectroscopy, single cell RNA sequencing, protein expression analyses as well as histology and transport studies.

Results: The applicability of our in vitro models for preclinical research is demonstrated on behalf of three representative barrier organs. (i) Bioavailability studies of oral drugs are possible on behalf of our established in vitro model of the small intestine that is built up on patient-derived organoids seeded on a biological scaffold developing a confluent polarized cell-monolayer that is characterized by a tight barrier as well as in vivo-like cellular and structural features such as the decoration of cells with microvilli. Gene expression profiling by single cell RNA (scRNA) sequencing further revealed the existence of three major cell clusters signifying the proliferative lineage as well as representatives of the secretory and absorptive lineage [1-2]. Further, transport characteristics for FDA approved substances such as Rhodamine123 or Na-Fluorescein are highly similar between our model and the native epithelium. (ii) Furthermore, we were able to build models representing the human skin for in vitro skin irritation testing by reconstructing of the epidermis. In a validation study we assessed a set of 20 reference substances according to the OECD test guideline 439 which resulted in an accuracy of 80% thereby indicating an alternative skin irritation test platform [3]. (iii) These models were adapted to simulate native cornea in vitro by using primary cells isolated from human cornea biopsies to enable eye irritation testing without compromising animals. By using impedance spectroscopy chemicals were identified for the different eye irritation severity categories [4].

Conclusion: The portfolio of cell-based test systems of human barrier organs developed by us delivers predictive results with regard to efficacy tests and thus represents a 3R-compliant test platform of alternative study models in preclinical research.

References: [1] Schweinlin M. et al. Tissue Eng Part C. 2016
[2] Däullary T. et al. Gut Microbes. 2023
[3] Groeber F. et al. Toxicol In Vitro. 2016
[4] Lotz C. et al. Sci Rep. 2018

Acknowledgements: Conflict of interest: The corresponding author declares that there is no conflict of interest with the authors. Statement on ethics vote: There is a positive ethics vote.

Portfolio of our cell-based test systems of the human barrier organs blood-brain barrier, respiratory tract, eye, skin and intestine. Important characteristics of the respective organs are shown by histological analyses. Models express cell-type specific markers together with a similar cellular morphology compared to the native tissue.