A next generation risk assessment was carried out to evaluate the safety of benzophenone-4 (BP-4), a UV filter present at 5% in a body lotion, to compare a non-animal approach with a traditional safety assessment based on historical animal data. Exposure characterization indicated that BP-4 is poorly absorbed through the skin, poorly metabolized by the liver, a substrate of influx and efflux transporters, and excreted by the kidney. The resulting physiologically-based kinetic model predicted an upper bound (95th percentile) plasma Cmax of 1.27 μM, and liver and kidney concentrations of 0.32 μM and 0.44 μM, respectively. To characterize bioactivity, in silico and in vitro new approach methodologies were used. Points of departure (PoDs) were derived from four bioactivity platforms, including in vitro pharmacological profiling, CALUX assays, high-throughput transcriptomics, and a cell stress panel. By dividing the in vitro PoDs (PoDNAM) from these assays by the 95th percentile plasma Cmax value, bioactivity exposure ratios (BERs) were calculated. The lowest PoD was from a single gene expression change, and the highest PoD from phenotypic biomarkers using a primary renal cell model. Most BERs were above 11, except for those from gene-level PoDNAM in HepG2 and MCF-7 cells, which were 3.3 and 4.3. These lowest PoDNAM values are linked to gene transcription changes and are likely indicative of adaptive biological activity rather than adverse health effects. This work demonstrates the usefulness of next generation risk assessment in addressing pressing relevant regulatory questions without using animals.
To address the challenges posed by traditional homogeneous palladium catalysts, such as separation issues, metal leaching, and contamination, this study introduces Pd-PEPPSI-decorated hyper-crosslinked polymers (HCPs) as highly efficient heterogeneous palladium catalysts for the Suzuki-Miyaura coupling of aryl chlorides and direct C-H arylation reactions. This work features a "large-but-flexible" N-heterocyclic carbene ligand design, incorporating bulky diphenylmethyl groups at the para-position of the N-aryl moieties. This steric hindrance enhances catalyst stability, prevents palladium leaching, and maintains an open-coordination environment, improving the catalytic efficiency. The catalytic performance was evaluated in both the Suzuki-Miyaura coupling and direct C-H arylation, achieving high yields (80-96%) under air conditions. The catalysts demonstrated excellent recyclability with minimal Pd leaching and sustained efficiency after multiple cycles. This work offers a cost-effective and scalable solution for the development of robust heterogeneous palladium catalysts, contributing to sustainable catalytic applications in organic synthesis and industrial chemistry.
New in vivo data cannot be generated for cosmetics. New safety assessments for genotoxicity must rely on in vivo data from the in vivo Mammalian Erythrocyte Micronucleus (MN) Test generated before the ban. Many used intraperitoneal (i.p.) administration, which is no longer recommended without scientific justification. Therefore, we investigated whether these studies are still valid for evaluating genotoxicity of hair dyes. Small to medium size molecules, including hair dyes, are preferentially absorbed via the portal vein and undergo first-pass metabolism, whereas large molecules are taken up by the lymphatics directly into the systemic circulation. Plasma concentrations of small molecules are generally similar, if not higher, after i.p. than after p.o. administration. Importantly, outcomes from in vivo MN Test using the i.p. and p.o. routes were equivalent. Most genotoxic carcinogens with positive outcomes in the in vivo MN Test were administered by i.p. injection. Differences between in vivo genotoxicity assay results using administration routes are attributed to the Mode of Action and/or tissue-specific effects. In conclusion, the i.p. route achieves sufficiently high internal exposure i.e., in the plasma and bone marrow. Therefore, legacy OECD test guideline compliant studies using the i.p. route are valid for current safety assessments of hair dyes.
This study aimed to develop a physiologically based kinetic (PBK) model for benzophenone-4 (BP-4) in humans based on in vitro and in silico input data and to achieve scientific confidence in predicted internal exposures of BP-4 in the absence of human kinetic data. The key steps included are: 1) establishing a core PBK model containing minimal required input for dermal absorption, liver metabolism, plasma protein binding, blood:plasma ratio, and tissue:plasma partition coefficients, 2) using chemical-specific characteristics to define additional key kinetic processes, which led to inclusion of transporter kinetics, and 3) conducting sensitivity analyses and assessing population variability. The in vitro kinetic results revealed limited skin penetration of BP-4 (< 0.4%), no metabolic conversion by the liver, and involvement of active transporters, including OAT1, OAT2, OAT3, BCRP, and MRP4. Inclusion of the transporter activity in the PBK model (scaled to kidney and liver) resulted in BP-4 active excretion and lowering of the plasma concentrations from 4 μM to 0.7 μM. Due to faster influx rates, by OAT1, OAT2, and OAT3, compared to efflux rates by BCRP and MRP4, relatively higher organ concentrations were predicted for the liver (0.31 μM) and kidney (0.18 μM) compared with other organs. While the PBK model results could not be evaluated against human data, we could evaluate the evolution of predicted concentrations in the process of developing the model. Increasing the physiological relevance of the model through inclusion of transporters increased confidence in the plausible ranges in plasma and organ concentrations.
The transition from traditional animal-based approaches and assessments to New Approach Methodologies (NAMs) marks a scientific revolution in regulatory toxicology, with the potential of enhancing human and environmental protection. However, implementing the effective use of NAMs in regulatory toxicology has proven to be challenging, and so far, efforts to facilitate this change frequently focus on singular technical, psychological or economic inhibitors. This article takes a system-thinking approach to these challenges, a holistic framework for describing interactive relationships between the components of a system of interest. In this case, the regulatory toxicology system. We do so by analysing and interpreting a very large qualitative data set of experts' observations, collected in a 3-day interactive workshop and three follow-up online workshops with a heterogeneous sample of experts representing major actors from the global regulatory toxicology system. We identified leverage points (where a small change within a system can have a disproportionately large effect) in the six core aspects-infrastructure, processes, culture, technology, goals, and actors-in the regulatory toxicology system to facilitate the effective use of NAMs. Identified systematic leverage points include the need for a functioning incentive structure for effectively discovering, developing, validating and using NAMs within academia, regulation, and industry; and measures that prevent or mitigate unwanted effects of using NAMs that acknowledge clashes between scientific, regulatory, political and social processes. The results serve as a basis for follow-up activities that reflect on the actual effectiveness of these levers and that develop measures for the regulatory toxicology system.
