Organ-on-a-chip: current gaps and future directions.

As an emerging hot topic of the last decade, Organ on Chip (OoC) is a new technology that is attracting interest from both basic and translational scientists. The Biochemical Society, with its mission of supporting the advancement of science, with addressing grand challenges that have societal impact, has included OoC into their agenda to review the current state of the art, bottlenecks and future directions. This conference brought together representatives of the main stakeholders in the OoC field including academics, end-users, regulators and technology developers to discuss and identify requirements for this new technology to deliver on par with the expectations and the key challenges and gaps that still need to be addressed to achieve robust human-relevant tools, able to positively impact decision making in the pharmaceutical industry and reduce overreliance on poorly predictive animal models.

Finding synergies for the 3Rs - Repeated Dose Toxicity testing: Report from an EPAA Partners' Forum.

The European Partnership for Alternative Approaches to Animal Testing (EPAA) convened a Partners' Forum on repeated dose toxicity (RDT) testing to identify synergies between industrial sectors and stakeholders along with opportunities to progress these in existing research frameworks. Although RTD testing is not performed across all industrial sectors, the OECD accepted tests can provide a rich source of information and play a pivotal role for safety decisions relating to the use of chemicals. Currently there are no validated alternatives to repeated dose testing and a direct one-to-one replacement is not appropriate. However, there are many projects and initiatives at the international level which aim to implement various aspects of replacement, reduction and refinement (the 3Rs) in RDT testing. Improved definition of use, through better problem formulation, aligned to harmonisation of regulations is a key area, as is the more rapid implementation of alternatives into the legislative framework. Existing test designs can be optimised to reduce animal use and increase information content. Greater use of exposure-led decisions and improvements in dose selection will be beneficial. In addition, EPAA facilitates sharing of case studies demonstrating the use of Next Generation Risk Assessment applying various New Approach Methodologies to assess RDT.

One science-driven approach for the regulatory implementation of alternative methods: A multi-sector perspective.

EU regulations call for the use of alternative methods to animal testing. During the last decade, an increasing number of alternative approaches have been formally adopted. In parallel, new 3Rs-relevant technologies and mechanistic approaches have increasingly contributed to hazard identification and risk assessment evolution. In this changing landscape, an EPAA meeting reviewed the challenges that different industry sectors face in the implementation of alternative methods following a science-driven approach. Although clear progress was acknowledged in animal testing reduction and refinement thanks to an integration of scientifically robust approaches, the following challenges were identified: i) further characterization of toxicity pathways; ii) development of assays covering current scientific gaps, iii) better characterization of links between in vitro readouts and outcome in the target species; iv) better definition of alternative method applicability domains, and v) appropriate implementation of the available approaches. For areas having regulatory adopted alternative methods (e.g., vaccine batch testing), harmonised acceptance across geographical regions was considered critical for broader application. Overall, the main constraints to the application of non-animal alternatives are the still existing gaps in scientific knowledge and technological limitations. The science-driven identification of most appropriate methods is key for furthering a multi-sectorial decrease in animal testing.

Finding synergies for 3Rs - Toxicokinetics and read-across: Report from an EPAA partners' Forum.

The European Partnership for Alternative Approaches to Animal Testing (EPAA) convened a Partners' Forum Toxicokinetics and Read-Across to provide an overview on research activities to develop in vitro toxicokinetics methods and physiologically-based kinetic (PBK) models and to find synergies to enhance use of toxicokinetic data to strengthen read-across. Currently, lacking toxicokinetic data often prevent the application of read-across. Preferably, toxicokinetic data should be generated using in vitro and in silico tools and anchored towards human relevance. In certain sectors, PBK modelling is being used for risk assessment, but less so in others. Specific activities were identified to facilitate the use of in vitro and in silico toxicokinetic data to support read-across: The collation of available tools indicating the parameters and applicability domains covered; endpoint-specific guidance on toxicokinetics parameters required for read-across; case studies exemplifying how toxicokinetic data help support read-across. Activities to enhance the scientific robustness of read-across include the further user-friendly combination of read-across tools and formal guidance by the authorities specifying the minimum information requirements to justify read-across for a given toxicity endpoint. The EPAA was invited to continue dissemination activities and to explore possibilities to collate a contemporaneous list of open toxicokinetics tools that assist risk assessment.

Report of the EPAA-ECVAM workshop on the validation of Integrated Testing Strategies (ITS).

The use of Integrated Testing Strategies (ITS) permits the combination of diverse types of chemical and toxicological data for the purposes of hazard identification and characterisation. In November 2008, the European Partnership for Alternative Approaches to Animal Testing (EPAA), together with the European Centre for the Validation of Alternative Methods (ECVAM), held a workshop on Overcoming Barriers to Validation of Non-animal Partial Replacement Methods/Integrated Testing Strategies, in Ispra, Italy, to discuss the extent to which current ECVAM approaches to validation can be used to evaluate partial replacement in vitro test methods (i.e. as potential ITS components) and ITS themselves. The main conclusions of these discussions were that formal validation was only considered necessary for regulatory purposes (e.g. the replacement of a test guideline), and that current ECVAM approaches to validation should be adapted to accommodate such test methods. With these conclusions in mind, a follow-up EPAA-ECVAM workshop was held in October 2009, to discuss the extent to which existing validation principles are applicable to the validation of ITS test methods, and to develop a draft approach for the validation of such test methods and/or overall ITS for regulatory purposes. This report summarises the workshop discussions that started with a review of the current validation methodologies and the presentation of two case studies (skin sensitisation and acute toxicity), before covering the definition of ITS and their components, including their validation and regulatory acceptance. The following main conclusions/recommendations were made: that the validation of a partial replacement test method (for application as part of a testing strategy) should be differentiated from the validation of an in vitro test method for application as a stand-alone replacement, especially with regard to its predictive capacity; that, in the former case, the predictive capacity of the whole testing strategy (rather than of the individual test methods) would be more important, especially if the individual test methods had a high biological relevance; that ITS allowing for flexible and ad hoc approaches cannot be validated, whereas the validation of clearly defined ITS would be feasible, although practically quite difficult; and that test method developers should be encouraged to develop and submit to ECVAM not only full replacement test methods, but also partial replacement methods to be placed as parts of testing strategies. The added value from the formal validation of testing strategies, and the requirements needed in view of regulatory acceptance of the data, require further informed discussion within the EPAA forum on the basis of case studies provided by industry.

Integration of lead optimization with crystallography for a membrane-bound ion channel target: discovery of a new class of AMPA receptor positive allosteric modulators.

A novel series of AMPAR positive modulators is described that were identified by high throughput screening. The molecules of the series have been optimized from a high quality starting point hit to afford excellent developability, tolerability, and efficacy profiles, leading to identification of a clinical candidate. Unusually for an ion channel target, this optimization was integrated with regular generation of ligand-bound crystal structures and uncovered a novel chemotype with a unique and highly conserved mode of interaction via a trifluoromethyl group.

Overcoming barriers to validation of non-animal partial replacement methods/Integrated Testing Strategies: the report of an EPAA-ECVAM workshop.

The use of Integrated Testing Strategies (ITS) in toxicological hazard identification and characterisation is becoming increasingly common as a method for enabling the integration of diverse types of toxicology data. At present, there are no existing procedures and guidelines for the construction and validation of ITS, so a joint EPAA WG5-ECVAM workshop was held with the following objectives: a) to investigate the role of ITS and the need for validation of ITS in the different industry sectors (pharmaceuticals, cosmetics, chemicals); b) to formulate a common definition of ITS applicable across different sectors; c) to explore how and when Three Rs methods are used within ITS; and d) to propose a validation rationale for ITS and for alternative methods that are foreseen to be used within ITS. The EPAA provided a platform for comparing experiences with ITS across different industry sectors. It became clear that every ITS has to be adapted to the product type, R&D stage, and regulatory context. However, common features of ITS were also identified, and this permitted the formulation of a general definition of ITS in a regulatory context. The definition served as a basis for discussing the needs, rationale and process of formal ITS validation. One of the main conclusions was that a formal validation should not be required, unless the strategy will serve as full replacement of an in vivo study used for regulatory purposes. Finally, several challenges and bottlenecks to the ITS validation were identified, and it was agreed that a roadmap on how to address these barriers would be established by the EPAA partners.

Toward refinement of the colony-forming unit-granulocyte/macrophage clonogenic assay: inclusion of a metabolic system.

This work represents a first attempt to refine the colony-forming unit-granulocyte/macrophage (CFU-GM) clonogenic assay by incorporating liver microsomes and co-factors as a metabolic system into the in vitro test system in response to an ECVAM recommendation. From the comparison of results obtained with the CFU-GM clonogenic assay currently used and with the new experimental protocol, different toxicity on granulocyte/macrophage precursors was demonstrated, when drugs with a known metabolism in vivo were tested.

A new experimental protocol as an alternative to the colony-forming unit-granulocyte/macrophage (CFU-GM) clonogenic assay to assess the haematotoxic potential of new drugs.

In this work, a first attempt to set-up a new in vitro experimental protocol with culture in liquid medium and flow cytometry analysis of bone marrow progenitors is described. This protocol is proposed as an alternative to the colony-forming unit-granulocyte/macrophage (CFU-GM) clonogenic in vitro assay currently used to assess the toxic potential of new drugs in the bone marrow. This new experimental approach should enable to speed up the procedure of the in vitro haematotoxic potential assessment, to reduce inter-experimental variability and to enhance result accuracy. Preliminary results obtained demonstrated that the progenitor cell count by flow cytometry replacing the light microscopy granulocyte/macrophage colony count represents a tremendous improvement in terms of accuracy and standardisation. Moreover, differential counts of cell sub-populations can be performed by using specific monoclonal antibodies. Furthermore, this method demonstrated to be time-saving, since 4 day cell incubation period is required instead of 7-14 day incubation in the CFU-GM clonogenic assay. On the basis of results obtained so far, the new experimental protocol proposed looks a promising alternative to the CFU-GM clonogenic assay currently used.

An inter-laboratory study to evaluate the effects of medium composition on the differentiation and barrier function of Caco-2 cell lines.

Differentiated human intestinal Caco-2 cells are frequently used in toxicology and pharmacology as in vitro models for studies on intestinal barrier functions. Since several discrepancies exist among the different lines and clones of Caco-2 cells, comparison of the results obtained and optimisation of models for use for regulatory purposes are particularly difficult, especially with respect to culture conditions and morphological and biochemical parameters. An inter-laboratory study has been performed on the parental cell line and on three clonal Caco-2 cell lines, with the aim of standardising the culture conditions and identifying the best cell line with respect to parameters relevant to barrier integrity, namely, trans-epithelial electrical resistance (TEER) and mannitol passage, and of epithelial differentiation (alkaline phosphatase activity). Comparison of the cell lines maintained in traditional serum-supplemented culture medium or in defined medium, containing insulin, transferrin, selenium and lipids, showed that parameter performance was better and more reproducible with the traditional medium. The maintenance of the cell lines for 15 days in culture was found to be sufficient for the development of barrier properties, but not for full epithelial differentiation. Caco-2/TC7 cells performed better than the other three cell lines, both in terms of reproducibility and performance, exhibiting low TEER and mannitol passage, and high alkaline phosphatase activity.

[Integrated project for the translational research on pancreatic ductal carcinoma]. / Progetto integrato per la ricerca translazionale nel carcinoma duttale del pancreas.

The narrow chances of therapy and the poor prognosis of pancreatic cancer make basic research a crucial way for both a better knowledge and a possible improvement in the treatment of this disease. The very limited availability of pancreatic specimen for genetic and biological studies forced the researchers to plan "in vitro" and "in vivo" models in order to overcome this handicap. Among the animal models, the one according to Fu et al. seemed to be the most helpful and effective approach. Nevertheless, being this model complex and failing in main perspective applications, an enlarged project perpetuating B-lymphocytes of the patients, successfully xenografting from vitally criopreserved specimen and developing cell lines from xenografts was planned. According to the aim of our project, a really perpetual and renewable bank of tumoral and normal tissue from patients suffering from pancreatic carcinoma was obtained. This model is also expected to be an effective approach for the evaluation of experimental chemotherapeutic schedules and new gene therapy assessment.