Potential Sensitivity Research Articles

Benzoyl Peroxide's Sensitisation Potential and Potency in Experimental Methods and Review of Contact Allergy and Allergic Contact Dermatitis.

Positive patch test responses to benzoyl peroxide (BPO) have been reported from patients without and with known exposure. Up to 6.5% were found in the United States and 7.8% in a study including patients from Germany, Austria and Switzerland. We provide an overview of the skin sensitisation potential and potency of BPO based on animal experiments and non-animal methods. BPO tested positive in Guinea Pig Tests and the Local Lymph Node Assay. Application of the current OECD guideline to identify a skin sensitizer by combining non-animal method results gave differing outcomes. Moreover, patch test responses of patients to BPO were considered to determine the importance of BPO as a relevant occupational contact allergen. Another well-known BPO exposure is the topical application to treat acne. Despite widespread use, extensive and long-term skin exposure, we found for this group only studies reporting few positive patch test reactions. Further, occupational handling of BPO and contact allergy is reported by dental technicians. In-depth evaluation of the prevalence of contact allergy in different professions with suspected BPO exposure did not reveal an association with occupational handling of BPO. Consequently, a generally increased risk for those professions is not supported.

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay.

Potency and quantitative risk assessment are essential for determining safe concentrations for the formulation of potential skin sensitizers into consumer products. Several new approach methodologies (NAMs) for skin sensitization hazard assessment have been developed, validated, and adopted in OECD test guidelines. However, work is ongoing to develop NAMs for predicting skin sensitization potency on a quantitative scale for use as a point of departure (POD) in next-generation risk assessment (NGRA). GARDskin Dose-Response (DR) is an adaptation of the validated GARDskin assay (OECD TG 442E), and the readout of the assay is a quantitative potency prediction similar to the No Expected Sensitization Induction Level (NESIL) value (µg/cm2). The goal of this study was to evaluate the performance of the GARDskin DR assay for potency prediction of fragrance ingredients. One hundred (100) fragrance ingredients from a reference database covering varied structural reactivity domains and potency were tested in GARDskin DR. Materials tested had varied protein-binding reactivity alerts, including Schiff base, Michael addition, SN2, and acylation. Potency categories were predicted with a total accuracy of 37% and an approximate accuracy (exact match or off by 1 category) of 81%. Combining predicted weak and very weak categories increased total accuracy to 53% and approximate accuracy to 98%. The mean prediction error for the NESIL and local lymph node assay (LLNA) EC3 was 3.15- and 3.36-fold, respectively. Based on the results of this study, GARDskin DR is a promising predictor of skin sensitization potency with an applicability domain covering a wide range of fragrance ingredient reaction mechanisms, increasing the confidence in using the assay to conduct NGRA, ultimately reducing the need for animal testing.

An alternatively translated isoform of PPARG proposes AF-1 domain inhibition as an insulin sensitization target.

PPARγ is the pharmacological target of thiazolidinediones (TZDs), potent insulin sensitizers that prevent metabolic disease morbidity but are accompanied by side effects such as weight gain, in part due to non-physiological transcriptional agonism. Using high throughput genome engineering, we targeted nonsense mutations to every exon of PPARG, finding an ATG in Exon 2 (chr3:12381414, CCDS2609 c.A403) that functions as an alternative translational start site. This downstream translation initiation site gives rise to a PPARγ protein isoform (M135), preferentially generated from alleles containing nonsense mutations upstream of c.A403. PPARγ M135 retains the DNA and ligand binding domains of full-length PPARγ but lacks the N-terminal AF-1 domain. Despite being truncated, PPARγ M135 shows increased transactivation of target genes, but only in the presence of agonists. Accordingly, human missense mutations disrupting AF-1 domain function actually increase agonist-induced cellular PPARγ activity compared to wild-type (WT), and carriers of these AF-1 disrupting variants are protected from metabolic syndrome. Thus, we propose the existence of PPARγ M135 as a fully functional, alternatively translated isoform that may be therapeutically generated to treat insulin resistance-related disorders.

Comprehensive Extractables and Leachables Sensitization Analysis and Practical Application of a Risk-Based Approach to Sensitization Assessment for Parenteral Drug Products.

The Extractables and Leachables Safety Information Exchange (ELSIE) Consortium added to the sensitization potency analysis of Parris et al. (2023) by including the Product Quality Research Institute (PQRI) extractable and leachable dataset (Johnson et al., 2024; Product Quality Research Institute, 2021). This analysis of the comprehensive E&L dataset showed 5% of chemicals (20/407) had experimental results demonstrating or were predicted to be potent (strong or extreme) sensitizers, supporting the previous conclusion, that potent sensitizers are of low prevalence and are not routinely observed as leachables in pharmaceutical products. By accounting for prevalence of sensitization in the overall E&L dataset, the probability of any potential leachable being more potent than the less than lifetime ICH M7 (10, 20, and 120 μg/day for human exposure of >1-10 years, >1-12 months, and <1 month repectively) and non-mutagenic ELSIE threshold values (35, 110, and 180 μg/day for human exposures of >10 years to lifetime, >1-10 years, and ≤1 year respectively) (Masuda-Herrera et al., 2022) was considered. The M7 and ELSIE thresholds are anticipated to provide ≥95% coverage of induction of sensitization, supporting the use of these thresholds to set the Safety Concern Threshold (SCT).

The skin allergy risk assessment-integrated chemical environment (SARA-ICE) defined approach to derive points of departure for skin sensitization.

Mechanistically based non-animal methods for assessing skin sensitization hazard have been developed, but are not considered sufficient, individually, to conclusively define the skin sensitization potential or potency of a chemical. This resulted in the development of defined approaches (DAs), as documented in OECD TG 497, for combining information sources in a prescriptive manner to provide a determination of risk or potency. However, there are currently no DAs within OECD TG 497 that can derive a point of departure (POD) for risk assessment. The Skin Allergy Risk Assessment - Integrated Chemical Environment (SARA-ICE) DA for skin sensitization is a Bayesian statistical model that estimates a human-relevant metric of sensitizer potency, the ED01, an estimate of the human predictive patch test dermal dose at which there is 1% chance of inducing sensitization, which can be used in a risk assessment paradigm. The model accounts for variability of input data and explicitly quantifies uncertainty. SARA-ICE derives the ED01 from a variety of in vitro and in vivo test method data and is built upon historical human, murine, and in vitro test data for 434 chemicals. In addition to the ED01 POD SARA-ICE DA also provides a Globally Harmonized System of Classification and Labelling of Chemicals (GHS) classification probability for GHS subcategories 1A, 1B and not classified (NC). Here we describe the SARA-ICE model and its evaluation, including performance versus benchmark PODs. In addition, via a case study with isothiazolinones (ITs), we demonstrate the utility of SARA-ICE for integrating different data inputs and compare the ED01 for six ITs to existing historical data.

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl3

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl3

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl1

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl1

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl2

Determining a point of departure for skin sensitization potency and quantitative risk assessment of fragrance ingredients using the GARDskin dose-response assay_suppl2

An Integrated Testing Strategy and Online Tool for Assessing Skin Sensitization of Agrochemical Formulations.

Non-animal assessment of skin sensitization is a global trend. Recently, scientific efforts have been focused on the integration of multiple evidence for decision making with the publication of OECD Guideline No. 497 for defined approaches to skin sensitization. The integrated testing strategy (ITS) methods reported by the guideline integrates in chemico, in vitro, and in silico testing to assess both hazard and potency of skin sensitization. The incorporation of in silico methods achieved comparable performance with fewer experiments compared to the traditional two-out-of-three (2o3) method. However, the direct application of current ITSs to agrochemicals can be problematic due to the lack of agrochemicals in the training data of the incorporated in silico methods. To address the issue, we present ITS-SkinSensPred 2.0 for agrochemicals and agrochemical formulations using a reconfigured in silico model SkinSensPred for pesticides. Compared to ITSv2, the proposed ITS-SkinSensPred 2.0 achieved an 11% and 16% improvement in the accuracy and correct classification rate for hazard identification and potency classification, respectively. In addition, an online ITS tool was implemented and available on the SkinSensDB website. The tool is expected to be useful for evaluating skin sensitization of substances.

Self-Nanoemulsifying Formulation Improves Oral Bioavailability and Insulin Sensitizing Potency of Formononetin-Vitamin E Conjugate in Type 2 Diabetic Mice.

The escalating incidence of obesity, diabetes, and insulin resistance has become a significant global health concern. In this study, we have developed a self-nanoemulsifying delivery system (SNEDS) of formononetin-vitamin E conjugate (VESylated-FMN) for improving its oral bioavailability and improving insulin sensitivity and glycemic control. The developed SNEDS were characterized using dynamic light scattering and transmission electron microscopy. Thereafter, the loading capacity, in vitro release, thermodynamic, and gastrointestinal stability of the developed formulation were evaluated. The safety and oral bioavailability of VESylated-FMN-SNEDS were assessed in Sprague-Dawley rats, whereas insulin-sensitizing potency was assessed in high-fat diet-induced type 2 diabetic mice. The VESylated-FMN-SNEDS quickly emulsified on dilution (droplet size ∼79.17 nm) and showed remarkable thermodynamic and gastrointestinal stability. The developed formulation demonstrated enhanced oral bioavailability (∼1.3-fold higher AUC0-t) of VESylated-FMN without liver and kidney injury. Consequently, VESylated-FMN-SNEDS significantly improves insulin sensitivity and glycemic control in HFD-fed mice compared to VESylated-FMN by upregulating the transcript level of insulin-sensitizing genes. Therefore, the SNEDS formulation could be an effective strategy to augment the oral bioavailability and insulin-sensitizing potency of VESylated-FMN.

Identifying and Prioritizing Hazardous Chemicals in Construction Metal Structure Coating Systems: A Roadmap for Data-Driven Disease Prevention.

Occupational exposure as a painter was classified by the International Agency for Research on Cancer (IARC)as a Group 1 carcinogen (carcinogenic to humans) in 1989. Chemical agents responsible for cancers and other illnesses among industrial painters are not well-documented. The goal of this systematic review and synthesis was to document the chemistries of metal structure coating systems, summarize data gaps on occupational exposures and health effects among painters, and identify and prioritize hazardous chemicals to guide future exposure and occupational health studies, and ultimately disease prevention efforts. We reviewed coating products approved by the Northeast Protective Coating Committee (NEPCOAT) for use in steel bridges in New England, with a special focus on Part B of these reactive chemical systems, and related literature on exposures and health effects. From the review of safety datasheets (SDS), we identified 61 unique CAS numbers belonging to different Part B chemical groups of isocyanate- and epoxy-based formulations, including amine hardeners, solvents, nanomaterials, and other additives. The list of identified ingredients contained 14 potent sensitizers, two IARC Group 1 known carcinogens, and 7 IARC Group 2B possible carcinogens. Cancers of the lungs, urinary bladder, liver, kidneys, and gastrointestinal system, allergic contact dermatitis, lung fibrosis, and asthma were some possible disease endpoints. Existing occupational exposure studies focused on solvent exposures, while exposure and biomonitoring studies of amine hardeners and other ingredients of concern in these formulations are lacking. The list of chemicals of concern identified here, including sensitizers and carcinogens, can serve as a basis for analytical method development and field exposure assessment studies. A national multi-pronged strategy to reduce chemical exposures and health risks among construction painters is warranted, including research on exposure monitoring and reduction efforts, longitudinal epidemiological studies, and product reformulation.

Skin Sensitization Potency Prediction Based on Read-Across (RAx) Incorporating RhE-Based Testing Strategy (RTSv1)-Defined Approach: RTSv1-Based RAx.

In recent years, nonanimal approaches for skin sensitization have been developed in response to political, regulatory, and ethical demands. The reconstructed human epidermis (RhE)-based testing strategy (RTS)v1-defined approach (DA) is used to categorize skin sensitization potency. However, the RTSv1 DA alone cannot be used to predict potency based on EC3 values [the estimated concentration that produces a stimulation index of 3 in the local lymph node assay (LLNA)], and underpredictions have been reported. Read-across (RAx) can complement DA data and improve prediction confidence. Although case studies combining new approach methodology/DA data with RAx have been reported, they focus on a single target chemical and lack a comprehensive and robust strategy with well-examined reliability. This study developed a strategy incorporating the RTSv1 DA into RAx (RTSv1-based RAx) to predict skin sensitization potency, applying it to 43 chemicals. The predictive performance of RTSv1-based RAx was evaluated by comparing its predicted potency category and EC3 outcomes with those of RTSv1 DA and the LLNA. RTSv1-based RAx accurately predicted the Globally Harmonized System of Classification (GHS) subcategorization for 38 chemicals and determined the predicted EC3 values for 17 sensitizers within a fourfold range of LLNA-derived EC3 values. This study demonstrates that RTSv1-based RAx offers robust predictivity for both GHS subcategorization and predicted EC3 values, making it useful for quantitative risk assessment.

TRIB3 inhibition by palbociclib sensitizes prostate cancer to ferroptosis via downregulating SOX2/SLC7A11 expression

Palbociclib is a CDK4/6 inhibitor approved for the treatment of breast cancer by suppressing cell proliferation. However, monotherapy with palbociclib was discouraging in prostate cancer, calling for a mechanism-based effective therapy. In this study, we reported in prostate cancer that palbociclib is a potent sensitizer of ferroptosis, which is worked out by downregulating the expression of TRIB3, a gene highly expressed in prostate cancer. Specifically, TRIB3 knockdown augmented the response of prostate cancer cells to ferroptosis inducers, whereas, TRIB3 overexpression rescued prostate cancer cells from palbociclib-induced ferroptosis. Mechanistically, TRIB3 inhibition by palbociclib resulted in downregulation of SOX2, which subsequently led to compromised expression of SLC7A11, a cystine/glutamate antiporter that counteracts ferroptosis. Functionally, a combined treatment of palbociclib with ferroptosis inducer significantly suppressed prostate cancer growth in a xenograft tumor model. Together, these results uncover an essential role of TRIB3/SOX2/SLC7A11 axis in palbociclib-induced ferroptosis, suggesting palbociclib a promising targeted therapy in combine with ferroptosis induction for the treatment of prostate cancer.

Predicting points of departure and potency categories for fragrance ingredients by integrating OECD in vitro models

Continuous potency assessment is crucial for conducting quantitative risk assessment (QRA) of sensitizers. Quantitative regression models, based on in vitro methods, have been developed to calculate points of departure for use in skin sensitization QRA. These models calculate a point of departure as a predicted value for Local Lymph Node Assay (LLNA) EC3 or potency value (PV), integrating data from the kinetic Direct Peptide Reactivity Assay (kDPRA), KeratinoSens (KS) assay, and human Cell Line Activation Test (h-CLAT). The goal of this study was to determine how in vitro predicted EC3s and PVs compare to published reference data. In vitro data were combined in point of departure regression models to predict EC3s and PVs. These points of departure were then grouped into sensitization potency categories, such as extreme, strong, moderate, weak, very weak, or non-sensitizer, as previously described. Trends in potency distribution and high concordance between predicted EC3 and PV categories and published potency categories were observed. Furthermore, the median absolute fold-misprediction ranged between 1.8 and 2.5 for models predicting EC3 and between 1.7 and 3.4 for those predicting PVs. These regression models are a promising animal alternative for determining sensitization quantitative potency for fragrance ingredients, thereby facilitating QRA.

Increasing Accessibility of Bayesian Network-Based Defined Approaches for Skin Sensitisation Potency Assessment.

Skin sensitisation is a critical adverse effect assessed to ensure the safety of compounds and materials exposed to the skin. Alongside the development of new approach methodologies (NAMs), defined approaches (DAs) have been established to promote skin sensitisation potency assessment by adopting and integrating standardised in vitro, in chemico, and in silico methods with specified data analysis procedures to achieve reliable and reproducible predictions. The incorporation of additional NAMs could help increase accessibility and flexibility. Using superior algorithms may help improve the accuracy of hazard and potency assessment and build confidence in the results. Here, we introduce two new DA models, with the aim to build DAs on freely available software and the newly developed kDPRA for covalent binding of a chemical to skin peptides and proteins. The new DA models are built on an existing Bayesian network (BN) modelling approach and expand on it. The new DA models include kDPRA data as one of the in vitro parameters and utilise in silico inputs from open-source QSAR models. Both approaches perform at least on par with the existing BN DA and show 63% and 68% accuracy when predicting four LLNA potency classes, respectively. We demonstrate the value of the Bayesian network's confidence indications for predictions, as they provide a measure for differentiating between highly accurate and reliable predictions (accuracies up to 87%) in contrast to low-reliability predictions associated with inaccurate predictions.

Updating Reaction Mechanistic Domains for Skin Sensitization: 1. Nucleophilic Skin Sensitizers.

It has long been recognized that skin sensitizers either are electrophilic or can be activated to electrophilic species. Several nonanimal assays for skin sensitization are based on this premise. In the course of a project to update dermal sensitization thresholds (DST), we found a substantial number of sensitizers, with no electrophilic or pro-electrophilic alerts, that could be simply explained in terms of the sensitizer acting as a nucleophile. In some cases, the nucleophilic center is a sulfur or phosphorus atom, while in others, it is an aromatic carbon atom. For carbon-centered nucleophiles, a quantitative mechanistic model based on a combination of Hammett σ+ and logP values has been derived. This has been applied to rationalize several groups of known sensitizers with no electrophilic or pro-electrophilic alerts, including anacardic acids and cardols, which are known human sensitizers associated with, inter alia, cashew nut oil, mango, and Ginkgo biloba. The possibility of nucleophilic sensitization needs to be considered when evaluating new chemicals for skin sensitization potential and potency by nonanimal assays, particularly those based on the premise that skin sensitization is dependent upon reactions of electrophiles with skin protein-based nucleophiles.

Identification of STAM-binding protein as a target for the treatment of gemcitabine resistance pancreatic cancer in a nutrient-poor microenvironment

Pancreatic cancer (PC) is a highly malignant solid tumor whose resistance to gemcitabine (GEM) chemotherapy is a major cause of poor patient prognosis. Although PC is known to thrive on malnutrition, the mechanism underlying its chemotherapy resistance remains unclear. The current study analyzed clinical tissue sample databases using bioinformatics tools and observed significantly upregulated expression of the deubiquitinase STAMBP in PC tissues. Functional experiments revealed that STAMBP knockdown remarkably increases GEM sensitivity in PC cells. Multiple omics analyses suggested that STAMBP enhances aerobic glycolysis and suppresses mitochondrial respiration to increase GEM resistance in PC both in vitro and in vivo. STAMBP knockdown decreased PDK1 levels, an essential regulator of the aerobic glycolytic process, in several cancers. Mechanistically, STAMBP promoted the PDK1-mediated Warburg effect and chemotherapy resistance by modulating E2F1 via direct binding to E2F1 and suppressing its degradation and ubiquitination. High-throughput compound library screening using three-dimensional protein structure analysis and drug screening identified the FDA drug entrectinib as a potent GEM sensitizer and STAMBP inhibitor, augmenting the antitumor effect of GEM in a patient-derived xenograft (PDX) model. Overall, we established a novel mechanism, via the STAMBP–E2F1–PDK1 axis, by which PC cells become chemoresistant in a nutrient-poor tumor microenvironment.

Apoptosis of Pancreatic Cancer Cells after Co-Treatment with Eugenol and Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand.

Pancreatic cancer is a refractory cancer with limited treatment options. Various cancer types are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Eugenol, the main component of clove oil, exhibits anticancer, anti-inflammatory, and antioxidant effects. However, no studies have reported that eugenol increases TRAIL sensitivity by upregulating death receptor (DR) expression. Here, we aimed to investigate eugenol as a potent TRAIL sensitizer. Increased apoptosis and inhibition of cell proliferation was observed in pancreatic cancer cells treated with eugenol and TRAIL compared with those treated with eugenol alone. Eugenol upregulated the expression of DR5, inhibited the FLICE-inhibitory protein (FLIP), an anti-apoptotic protein, and increased p53, a tumor suppressor protein. In addition, eugenol induced the generation of reactive oxygen species (ROS) and caused endoplasmic reticulum (ER) stress. C/EBP-homologous protein (CHOP) knockdown using siRNA decreased the expression of DR5 and reduced the combined effects of eugenol and TRAIL. These results demonstrate that eugenol enhances TRAIL-induced apoptosis by upregulating DR5 through the ROS-mediated ER stress-CHOP pathway, which enhances ER stress by inducing p53 and downregulating FLIP expression. This suggests that eugenol has the potential to treat pancreatic cancer by increasing cell sensitivity to TRAIL.

P19-57 Improved Confidence of Quantitative Sensitizing Potency Assessment for Point of Departure Using GARDskin Dose-Response

P19-57 Improved Confidence of Quantitative Sensitizing Potency Assessment for Point of Departure Using GARDskin Dose-Response

P19-41 The SENS-IS in vitro assay to predict and classify the skin sensitization potency of finished cosmetic products

P19-41 The SENS-IS in vitro assay to predict and classify the skin sensitization potency of finished cosmetic products