Industrial Genotoxicology Group (IGG): 36th Annual Meeting Report.

The proceedings of the 36th annual meeting of the Industrial Genotoxicology Group (IGG) are shared here. The meeting held at Lhasa Limited, Leeds, UK on 28th November 2023, focussed two aspects; New Approach Methodologies (NAM's), including those for the assessment of non-standard modalities such as gas-vapour assessments and nanomaterials, and addressing the regulatory challenges associated with understanding the genotoxic and carcinogenic potential of N-nitrosamines and N-nitrosamine impurities. New approach methodologies, such as error-corrected sequencing and enhanced Ames tests that may help address these challenges were also discussed.

A framework for the systematic evaluation of a novel cigarette filter technology.

Any functional change in cigarette filter design warrants a rigorous assessment to ensure comparability to existing filter functionality. This study compares the functionality of a standard CA filter with a novel cellulose-based alternative using a combination of emissions, in silico approaches, pre-clinical assessments and behavioural studies. We assess the challenges faced with a significant filtration change, the substantiation of this change and the limitations of such assessments.

Key Challenges for Testing of Tobacco Products for Regulatory Applications: Recommendations for the Mouse Lymphoma Assay.

The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to develop recommendations for optimal scientific and technical approaches for conducting assays to assess potential toxicity within and across traditional tobacco and various tobacco and nicotine next-generation products (NGPs), including Heated Tobacco Products (HTPs) and Electronic Nicotine Delivery Systems (ENDS). This report was developed by a working group composed of attendees of the seventh IIVS workshop, 'Approaches and recommendations for conducting the mouse lymphoma gene mutation assay (MLA) and introduction to disease models', which was held virtually on 21-23 June 2022. This publication provides a background overview of the MLA, and includes the description of assay conduct and data interpretation, key challenges and recommended best practices for evaluating tobacco and nicotine products, with a focus on the evaluation of NGPs, and a summary of how the assay has been used to evaluate and compare tobacco and nicotine products.

A comparison of cigarette smoke test matrices and their responsiveness in the mouse lymphoma assay: A case study.

No cigarette smoke test matrix is without limitation, due to the complexity of the starting aerosol and phase to phase dynamics. It is impossible to capture all chemicals at the same level of efficiency, therefore, any test matrix will inadvertently or by design fractionate the test aerosol. This case study examines how four different test matrices derived from cigarette smoke can be directly compared.

Key challenges for in vitro testing of tobacco products for regulatory applications: Recommendations for dosimetry.

The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to develop recommendations for optimal scientific and technical approaches for conducting in vitro assays to assess potential toxicity within and across tobacco and various next-generation products (NGPs) including heated tobacco products (HTPs) and electronic nicotine delivery systems (ENDSs). This publication was developed by a working group of the workshop members in conjunction with the sixth workshop in that series entitled "Dosimetry for conducting in vitro evaluations" and focuses on aerosol dosimetry for aerosol exposure to combustible cigarettes, HTP, and ENDS aerosolized tobacco products and summarizes the key challenges as well as documenting areas for future research.

Approaches In Carcinogenicity Hazard Assessment: Current Status and Future Needs.

Historically, identifying carcinogens has relied primarily on tumor studies in rodents, which require enormous resources in both money and time. models have been developed for predicting rodent carcinogens but have not yet found general regulatory acceptance, in part due to the lack of a generally accepted protocol for performing such an assessment as well as limitations in predictive performance and scope. There remains a need for additional, improved carcinogenicity models, especially ones that are more human-relevant, for use in research and regulatory decision-making.

Skin sensitization in silico protocol.

The assessment of skin sensitization has evolved over the past few years to include in vitro assessments of key events along the adverse outcome pathway and opportunistically capitalize on the strengths of in silico methods to support a weight of evidence assessment without conducting a test in animals. While in silico methods vary greatly in their purpose and format; there is a need to standardize the underlying principles on which such models are developed and to make transparent the implications for the uncertainty in the overall assessment. In this contribution, the relationship between skin sensitization relevant effects, mechanisms, and endpoints are built into a hazard assessment framework.

mutagenicity of gas-vapour phase extracts from flavoured and unflavoured heated tobacco products.

The mutagenic and genotoxic potential of Heated Tobacco Products (HTPs) has already been studied with the particulate phase and reported previously. This study has been designed to complement the assessment of the HTP and to determine whether the inclusion of potential flavourings would alter the response by testing the other phase of the aerosol, the gas-vapour phase (GVP). Both flavoured and unflavoured Neostik GVP samples did not show any sign of mutagenic activity in the Ames test but induced a mutagenic response in the mouse lymphoma assay (MLA), however, these responses were significantly less than those of the reference cigarette, 3R4F.

Genetic toxicology in silico protocol.

In silico toxicology (IST) approaches to rapidly assess chemical hazard, and usage of such methods is increasing in all applications but especially for regulatory submissions, such as for assessing chemicals under REACH as well as the ICH M7 guideline for drug impurities. There are a number of obstacles to performing an IST assessment, including uncertainty in how such an assessment and associated expert review should be performed or what is fit for purpose, as well as a lack of confidence that the results will be accepted by colleagues, collaborators and regulatory authorities. To address this, a project to develop a series of IST protocols for different hazard endpoints has been initiated and this paper describes the genetic toxicity in silico (GIST) protocol.

Assessment of priority tobacco additives per the requirements in the EU Tobacco Products Directive (2014/40/EU): Part 2: Smoke chemistry and in vitro toxicology.

This publication is part of a series of three publications and describes the non-clinical assessment performed to fulfill the regulatory requirement per Art. 6 (2) of the EU Tobacco Products Directive 2014/40/EU under which Member States shall require manufacturers and importers of cigarettes and Roll Your Own tobacco containing an additive that is included in the priority list established by Commission Implementing Decision (EU) 2016/787 to carry out comprehensive studies (European Comission, 2016). This publication contains the results of a literature search, comprehensive smoke chemistry, additive transfer, and in vitro toxicity studies for the 13 priority additives (carob bean extract, cocoa powder, fenugreek extract, fig juice concentrate, geraniol, glycerol, guaiacol, guar gum, liquorice extract powder, maltol, l-menthol (synthetic), propylene glycol, and sorbitol) commissioned by the members of the Priority Additives Tobacco Consortium to independent Contract Research Organizations.

Evaluation of flavourings potentially used in a heated tobacco product: Chemical analysis, in vitro mutagenicity, genotoxicity, cytotoxicity and in vitro tumour promoting activity.

We designed a novel tobacco-heating product (THP) that heats tobacco to release nicotine and aerosolised components, such as glycerol and tobacco volatiles from a tobacco rod (Neostik). Heating tobacco significantly reduces levels of combustion-derived toxicants in the aerosol compared to cigarette smoke. This study was conducted to determine whether the inclusion of potential flavourings in the THP would add to the levels of toxicants in the emissions or alter in vitro responses.

A novel hybrid tobacco product that delivers a tobacco flavour note with vapour aerosol (Part 2): In vitro biological assessment and comparison with different tobacco-heating products.

This study assessed the toxicological and biological responses of aerosols from a novel hybrid tobacco product. Toxicological responses from the hybrid tobacco product were compared to those from a commercially available Tobacco Heating Product (c-THP), a prototype THP (p-THP) and a 3R4F reference cigarette, using in vitro test methods which were outlined as part of a framework to substantiate the risk reduction potential of novel tobacco and nicotine products. Exposure matrices used included total particulate matter (TPM), whole aerosol (WA), and aqueous aerosol extracts (AqE) obtained after machine-puffing the test products under the Health Canada Intense smoking regime.

The combination of two novel tobacco blends and filter technologies to reduce the in vitro genotoxicity and cytotoxicity of prototype cigarettes.

Tobacco smoke from a combustible cigarette contains more than 6000 constituents; approximately 150 of these are identified as toxicants. Technologies that modify the tobacco blend to reduce toxicant emissions have been developed. These include tobacco sheet substitute to dilute toxicants in smoke and blend treated tobacco to reduce the levels of nitrogenous precursors and some polyphenols.