Developmental neurotoxicity testing with human embryonic stem cell-derived in vitro systems: the novel FP7 ESNATS tests are available

Avoiding a reproducibility crisis in regulatory toxicology-on the fundamental role of ring trials

The ongoing transition from chemical hazard and risk assessment based on animal studies to assessment relying mostly on non-animal data, requires a multitude of novel experimental methods, and this means that guidance on the validation and standardisation of test methods intended for international applicability and acceptance, needs to be updated. These so-called new approach methodologies (NAMs) must be applicable to the chemical regulatory domain and provide reliable data which are relevant to hazard and risk assessment. Confidence in and use of NAMs will depend on their reliability and relevance, and both are thoroughly assessed by validation. Validation is, however, a time- and resource-demanding process. As updates on validation guidance are conducted, the valuable components must be kept: Reliable data are and will remain fundamental. In 2016, the scientific community was made aware of the general crisis in scientific reproducibility-validated methods must not fall into this. In this commentary, we emphasize the central importance of ring trials in the validation of experimental methods. Ring trials are sometimes considered to be a major hold-up with little value added to the validation. Here, we clarify that ring trials are indispensable to demonstrate the robustness and reproducibility of a new method. Further, that methods do fail in method transfer and ring trials due to different stumbling blocks, but these provide learnings to ensure the robustness of new methods. At the same time, we identify what it would take to perform ring trials more efficiently, and how ring trials fit into the much-needed update to the guidance on the validation of NAMs.

The Future of the Teratogenicity Testing

The purpose of this review is to examine the importance, possible advantages and disadvantages of teratogenicity tests, and their future. For this purpose, numerous sources have been scanned in the field of teratogenicity. Although there are many methods related to teratogenic studies and very important studies have been made in this field, there are still serious deficiencies. There are advantages and disadvantages of in vitro and in vivo classical tests that have been used so far. The current status of in vivo tests is a matter of debate, especially due to the use of experimental animals. However, in vitro tests that do not perform the distribution and metabolism of chemicals also raise doubts in determination of teratogenicity. Despite the modern approaches of molecular biology and genetics and the best diagnostic techniques, the real cause of more than half of congenital diseases is still not understood. In this sense, the importance and necessity of teratogenic tests are understood once again. It is necessary to develop faster, reliable, and inexpensive techniques to replace traditional in vivo tests. It is important to disseminate harmless and reliable imaging techniques such as micro-CT. The use of European Center for the Validation of Alternative Methods (ECVAM) scientifically validated and approved in vitro tests such as embryonic stem cell test (EST), micro mass test (MM), and whole embryo culture (WEC) tests in routine screening can provide a solution in a shorter time than the classical tests. Improving these tests and developing new tests can help to solve the problem permanently.

Interpreting in vitro developmental toxicity test battery results: The consideration of toxicokinetics

In the EU collaborative project ChemScreen an alternative, in vitro assay-based test strategy was developed to screen compounds for reproductive toxicity. A toxicokinetic modeling approach was used to allow quantitative comparison between effective concentrations in the in vitro test battery and observations of developmental toxicity in vivo. This modeling strategy is based on (1) the definition of relevant observations of toxicity in vivo, (2) simulation of the corresponding systemic concentrations in vivo by toxicokinetic modeling, and (3) correction for differences in protein binding and lipid partitioning between plasma and in vitro test media. The test results of a feasibility study with a number of known reproductive toxicants has been described previously (Piersma et al. [15]). In the present paper, we take a more detailed look at the toxicokinetics of these compounds, and add the analysis of some compounds from subsequent studies. We discuss how the consideration of toxicokinetics allowed comparison between test systems with differing test medium composition, has helped to interpret the in vitro findings in light of in vivo observations, and to gain confidence in the predictive value of the test battery outcomes. The same toxicokinetic modeling strategy, in reverse order, can now be used for risk assessment purposes to predict toxic doses in vivo from effective concentrations in vitro.