Genetic Toxicology Technical Committee (GTTC)

Mission Statement

The mission of this committee is to improve the scientific basis of the interpretation of results from genetic toxicology tests for purposes of more accurate hazard identification and assessment of human risk; to develop follow-up strategies for determining the relevance of test results to human health; to provide a framework for integration of testing results into a risk-based assessment of the effects of chemical exposures on human health; to promote the integration and use of new techniques and scientific knowledge in the evaluation of genetic toxicology; and to monitor and promote the development of innovative tests and testing strategies.

HESI GTTC Professional Development Award 2025 Cycle: Now Open!

The Health and Environmental Sciences Institute’s Genetic Toxicology Technical Committee (HESI GTTC) Education and Science Outreach Committee is pleased to announce that the 2025 award cycle is now open! These awards will provide opportunities for trainees to attend scientific conferences, workshops, or courses, etc., to build core competencies and transferable skills, and/or share their research. Awardees will be invited to GTTC’s 2026 Annual Meeting to learn about the emerging projects and science at HESI and to network with experts in the genetic toxicology field.

Two award categories:

  • Professional Development Travel Award – Provides $1,500 USD for travel to attend scientific conferences or workshops.
  • Professional Development Training Award (new!) – Provides $4,000 USD for travel specific to training courses, cross-lab trainings, etc., to build core competencies and transferrable skills.

Learn more and download the application here.

  • Past Award Winners

    2024 Spring Awardees:

    2023 Spring Awardees: Tony Okeke (Drexel University), Ammer Khawam (McGill University), Natalia Bertolez (University of Coruna), Sarah Park (Oak Ridge, US EPA), Victoria Bastos (Maastricht University), Alper Alcarez (NIEHS), Idoia Meaza Izusi (University of Louisville)

    2022 Spring: Jonathan Axellson (UOttawa), Julie Sanders (Sciensano), Anouk Thienpont (VUB), Sam Vielee (U Louisville), David Schuster (UOttawa), Danila Cuomo (Texas A&M).

    2022 Fall: Zhenming Yang (Rutgers), Lee Pribyl (MIT), Natalie Laspata (Pittsburg), Daniela Muoio (Pittsburg), Elizabeth Irvin (NC State), Rebekah Petroff (Michigan).

Working Groups

  • Education and Science Outreach Committee

    Since its launch in 2022, the Education and Science Outreach Working Group has aimed to promote genetic toxicology as a career path and equip the next generation of scientists with foundational skills and experiences. By creating opportunities for networking, skill-building, and mentorship, the group supports early-career researchers in advancing their expertise and connecting with leaders in the field. In 2024, the program broadened its scope to introduce two new awards that help trainees share their research and grow professionally.

    GTTC offers three professional development awards:

    • Professional Development Travel Award – This award supports attendance at scientific conferences and workshops, allowing trainees to engage with current research, expand their networks, and gain insights into cutting-edge topics in genetic toxicology.
    • Professional Development Training Award – Launching in 2024 this award supports travel for specialized training courses, cross-laboratory exchanges, and skill-building activities, this award is designed to strengthen core competencies and enhance the practical skills needed in research.
    • Project Award – Through this award, which launched in 2024 trainees are paired with mentors within GTTC to work on projects closely tied to ongoing working group efforts, providing both hands-on research experience and mentorship in a collaborative setting.

    All awardees are invited to the GTTC Annual Meeting to learn about emerging projects and science at HESI and to network with experts in the gene toxicology field.

    Leadership Team:
    Joel Bercu (Gilead), Erica Briggs (Litron Laboratories)

    HESI Staff:
    Raechel Puglisi, MPH

  • Error-Corrected Sequencing

    This working group is focused on evaluating error corrected next generation sequencing (ecNGS) as an alternative method for assessing in vivo mutagenesis. It’s current focus is on investigating the suitability of ecNGS for regulatory mutagenicity testing. In 2023, the group published a position and review paper on this technology and has recently submitted a paper focused on the sensitivity of Duplex Sequencing through a reconstruction experiment. New initiatives include:

    • Supporting efforts to develop a publicly available database to be housed at the Division of Translational Toxicology/ National Institute of Environmental Health Sciences (DTT/NIEHS);
    • Selecting new chemicals for testing across different ecNGS platforms;
    • Exploring in vitro applications of ecNGS

    Leadership Team:
    Shaofei Zhang (Pfizer), Barbara Parsons (US FDA/NCTR)

    HESI Staff:
    Connie Chen, PhD, MPH

  • Germ Cells

    This working group focuses on developing and refining protocols for assessing genotoxic effects on germ cells. The group has published a manuscript on the impact of analyzing mutations in fast-proliferating tissues at different sampling times. Current efforts include drafting a review paper and collecting data to support UN GHS germ cell criteria for the classification and labeling of chemicals. New workstreams being discussed included:

    • Quantitative analyses of germ cell data
    • Genotoxic effects in oocytes
    • In vitro approaches for germ cell mutagenicity

    Leadership Team:
    Francesco Marchetti, PhD (Health Canada), Jan van Benthem, PhD (RIVM, Retired)

    HESI Staff:
    Connie Chen, PhD, MPH

  • Historical Control Distribution

    This working group is dedicated to establishing consistent methods for compiling, maintaining, and monitoring historical control ranges through consensus among testing laboratories, industry, and regulators. A survey was distributed to gather insights into best practices, with preliminary results presented at IWGT. The group is now discussing additional analyses and planning next steps for data collection.

    Leadership Team:
    Robert Heflich (US Food and Drug Administration), Robert Smith (Labcorp)

    HESI Staff:
    Connie Chen, PhD, MPH

  • In Vitro

    This working group aims to critically evaluate new approach methodologies (NAMs) for in vitro genotoxicity testing, aiming to expand current testing strategies and ultimately make recommendations for creating an “in vitro only” approach for genetox testing that meets the needs of various regulatory decision-makers. The group is currently focused on the first of its committee-defined goals, which involves a comprehensive critical evaluation of NAMS through four focus areas:

    • Identification of aneugens;
    • Metabolism;
    • Indirect genotoxicity;
    • IVIVE

    Leadership Team:
    Marc Beal (Health Canada), Giel Hendriks, PhD (Toxys B.V.)

    Subteam Leadership: IVIVE – Alexandra Long (Health Canada); Metabolism – Nikolai Chepelev (Health Canada), Xiaoqing Guo (US FDA/NCTR); Indirect GTX – Ashley Allemang (P&G), Inger Brandsma (Toxys); Aneugens – Xiaowen Sun (Pfizer)

    HESI Staff:
    Alexandra Taraboletti, PhD; Connie Chen, PhD, MPH

  • In Vivo Follow-Up

    This working group is dedicated to offering detailed guidance and best practices for selecting and conducting in vivo tests following a positive genotoxicity result. A key focus is ensuring that follow-up testing aligns with regulatory requirements and scientific best practices. One subgroup is focused on cytotoxicity of in vivo comet assays (data collection for retrospective analysis and development of a novel in vivo study). The recent pilot study data are under analysis, and the workgroup is planning out a new phase of work. This phase will focus on:

    • Evaluating the sensitivity of in vivo methods to detect weak effects of known mutagens.
    • Investigating how tail intensity influences the ability to detect subtle genotoxic effects.
    • These efforts aim to refine in vivo follow-up testing strategies, enhancing their precision and reliability in genotoxicity assessments.

    Leadership Team:
    Carol Beevers (Corteva), Matt LeBaron (Dow Chemical Company), David Lovell (St. George’s University of London)

    HESI Staff:
    Connie Chen, PhD, MPH

  • Mechanism-based Genotoxicity Risk Assessment (MGRA)

    The MRGA working group integrates the efforts of the former MOA and Clean Sheet working groups to establish a new mechanism-based paradigm for genotoxicity risk assessment. The group is composed of two subgroups focusing on Nitrosamines, and Titanium Dioxide (TiO2).

    Nitrosamines Subteam
    The primary objective of this subteam is to advance the scientific understanding and risk assessment of nitrosamines’ genotoxic potential through innovative mechanism-based testing approaches. (Leadership Team: Tetyana Cheairs (NY Medical College), Andreas Czich (Sanofi))

    This subteam has four working groups:

    1. Ames Optimization – Goal: Develop an optimized Ames protocol that is predictive of the carcinogenic potential of nitrosamines (Leadership Team: Anthony Lynch (GSK), Joel Bercu (Gilead); HESI Staff: Raechel Puglisi, MPH)
    2. In Vitro Approaches – Goal: Identification and verification of in vitro assays to assist in nitrosamine risk identification (Leadership Team: Xiaowen Sun (Pfizer) and Xiaoqing (Carol) Guo (US FDA/NCTR); HESI Staff: Raechel Puglisi, MPH)
    3. In Vivo Folow-up – Goal: Develop an in vivo strategy to verify Ames data within the frame of ICH M7 (Leadership: Joel Bercu (Gilead), Robert Jolly (Eli Lilly), Sheroy Minocherhomji (Eli Lilly), Timothy McGovern (US FDA); HESI Staff: Raechel Puglisi, MPH)
    4. (Q)SAR/QM – Goal: Refine and extend the CPCA using (Q)SAR and QM for improved predictive performance. (Leadership: David Ponting (Lhasa), Jakub Kostal (George Washington University), Kevin Cross (Instem); HESI Staff: Alex Taraboletti, PhD; Connie Chen, PhD, MPH)

    For more information about this subgroup – https://hesiglobal.org/gttc-nitrosamines/

    TiO2 Subteam
    TiO₂ serves as a data-rich case study, offering a complementary perspective to nitrosamines due its (likely) secondary mode of action and broad stakeholder interest to . This subteam aims to elucidate the mode of action, addressing data gaps, and advancing mechanism-based risk assessment strategies. Key objectives include:

    • Establish experimental evidence linking TiO₂ genotoxicity to oxidative stress as a secondary mechanism.
    • Explore connections to the oxidative stress wiki (AOP 296).

    Leadership Team:
    Stefan Pfuhler (P&G), Paul Fowler (FS Tox Consulting)

    HESI Staff:
    Connie Chen, PhD, MPH

  • Mode of Action (MOA)

    This working group is completing several OECD AOP wikis. The first AOP “Oxidative DNA damage leading to mutations and chromosomal damage” was published on the AOPWiki in April 2023. The tubulin binding and topoisomerase II inhibition AOPs will be completed in early 2024, after which this work group will merge into the new MGRA work group.

    Leadership for Tubulin binding AOP:
    Yasmin Dietz (Sanofi)

    Leadership for Topoisomerase II AOP:
    Xiaowen Sun (Pfizer), Ryan Wheeldon (J&J)

    HESI Staff:
    Connie Chen, PhD, MPH

  • Quantitative Analysis (QA)

    This working group is driving advancements in genetic toxicology by evaluating chemical data and enhancing dose-response modeling tools. Key projects include:

    • Conducting a comprehensive genotoxicity dose-response study involving 48 mutagenic carcinogens.
    • Establishing critical effect size parameters to guide risk assessments.
      Providing data-driven insights to inform exposure limits for nitrosamines.
    • Collaborating with industry partners to expand the functionality of the GeneToxPi visualization tool.

    Research highlights involve optimizing in vivo study designs for precise Benchmark Dose (BMD) calculations and assessing inter-individual DNA repair variability. Moving forward, the QA Working Group will focus on developing guidance for the standardized application and regulatory acceptance of the BMD approach in genetic toxicology. These efforts aim to promote broader adoption of dose-response modeling in regulatory decision-making.

    Leadership Team:
    George Johnson (Swansea University), Andreas Zeller (Roche), Paul White (Health Canada)

    HESI Staff:
    Alexandra Taraboletti, PhD

HESI Staff

Leadership Team

  • Stephen Dertinger, PhD

    Litron Laboratories

  • George Johnson, PhD

    Swansea University

Committee Events

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HESI In Vitro Genetic Toxicity (IVGT) Testing Workshop

June 5, 2007 – June 6, 2007

Washington, DC, USA

The HESI Emerging Issues Subcommittee on the Relevance and Follow-up of Positive Results in in Vitro Genetic Toxicity Testing (IVGT) held an international workshop June 5-6, 2007, in Washington, DC.

Read more

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Committee Publications

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A comparative analysis of select P450 enzymes in uninduced and PB/BNF-induced hamster and rat liver S9

Mutation Research – Genetic Toxicology and Environmental Mutagenesis, 2025

Evans et al.

As part of its Nitrosamine Research Program (NRP), HESI’s Genetic Toxicology Technical Committee (GTTC) has supported the publication of a new study evaluating the relative CYP enzyme activities in uninduced and induced hamster and rat liver S9 preparations. This research is critical for assessing the metabolic ...

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A comparison of the lowest effective concentration in culture media for detection of chromosomal damage in vitro and in blood or plasma for detection of micronuclei in vivo

Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 2022

David Kirkland, James Whitwell, Robert Smith, ...

It is often assumed that genotoxic substances will be detected more easily by using in vitro rather than in vivo genotoxicity tests since higher concentrations, more cytotoxicity and static exposures can be achieved. However, there is a paucity of data demonstrating whether genotoxic substances are detected at lower ...

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A Comparison of Transgenic Rodent Mutation and In Vivo Comet Assay Responses for 91 Chemicals

Mutation Research / Genetic Toxicology and Environmental Mutagenesis, 2019

Kirkland D, Levy DD, LeBaron MJ, Aardema MJ, Beevers C, Bhalli J, ...

Whilst the TGR and comet assays are available for measuring genotoxic effects in multiple rodent tissues, there has been no systematic comparison of their performance in detecting genotoxicity per se. A working group of the Genetic Toxicology Technical Committee (GTTC), part of the Health and Environmental Sciences Institute ...

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Analysis of Negative Historical Control Group Data from the In Vitro Micronucleus Assay Using TK6 Cells

Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 2017

Lovell DP, Fellows M, Marchetti F, Christiansen J, Elhajouji A, ...

The recent revisions of the Organisation for Economic Co-operation and Development (OECD) genetic toxicology test guidelines emphasize the importance of historical negative controls both for data quality and interpretation. The goal of a HESI Genetic Toxicology (GTTC) Committee workgroup was to collect data from ...

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