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Your Environment. Your Health.

Clustering and Classification Workshop

Applications to Investigate Adverse Effects of Chemicals on Human Health and Environment Workshop
October 3-4, 2022 • 8:30 a.m. – 4:00 p.m. EDT

illustration of atoms and DNA

Main Purpose

This 2-day virtual workshop is part of the NIEHS/DTT scientific outreach activities to discuss Clustering and Classification Methods (and related cheminformatic tools as part of New Approach Methodologies (NAM)s) and their applications to facilitate toxicology research and provide information for risk assessment. The workshop will introduce the concept of similarity and the different classification and clustering approaches as well as their uses for scientific toxicity research and risk assessment. The invited speakers and expert discussants will help to identify best practices and guidelines for the application of these approaches. Participation from attendees to round table discussions will be encouraged.

This workshop is supported by the DTT/NIEHS Consumer Products and Therapeutics Program, which has a goal of developing and applying define approaches to infer hazard across specific structural and functional substance classes.

Workshop Goals

  • Increase communication and collaboration from different sectors: government, academia and industry (US & international)
  • To educate and correct misconceptions and develop new ideas/concepts (best practices & innovation)
  • To introduce the different classification and clustering approaches and their uses for scientific toxicity research and risk assessment
  • To involve both NAM developers and users (regulators, researchers) to increase benefit and exchange

Discussion Topics

  • Chemical similarity: supervised vs unsupervised similarity (clustering)
  • Classic read-across (analogues) and endpoint specific classification/clustering-based approaches (surrogates)
  • How to develop and how to apply the clustering and classification approaches
  • “Relativity” of chemicals similarity: supervised vs unsupervised similarity (clustering)
  • Applications and examples


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Privacy Act Statement

The primary use of the collection of your name and email address is for providing the webinar link and information, communicating about the workshop, and/or for individual follow up after the workshop. If you do not provide this information, you would not be able to participate in the workshop. Collection of this information is authorized under 42 U.S.C. 203, 241, 289l-1 and 44 U.S.C. 3101, and Section 301 and 493 of the Public Health Service Act. The Privacy Act System of Records Notice (SORN) that covers collection of this information is 09-25-0156 Records of Participants in Programs and Respondents in Surveys Used to Evaluate Programs of the Public Health Service, HHS/PHS/NIH/OD and 09-90-1901 HHS Correspondence, Comment, Customer Service, and Contact List Records.


Day 1: Monday, October 3, 2022


Session 1 (8:45 – 11:45 a.m. EDT): Chemicals and Similarity: Structures and Bioactivity

This session will provide an introduction covering chemical structures and the concept of similarity from a structural, biological, phenotypic, and mechanistic perspective, including how similarity matters and depends on the context and goal in research and regulatory assessment. It will also include a discussion on the concept of activity cliffs and cases where subtle differences in structural characteristics can lead to orders of magnitude differences in biological activity.


  • José Medina-Franco, Universidad Nacional Autónoma de México
  • Esther Kellenberger, Université de Strasbourg
  • Andrea Mauri, Alvascience

Round Table Discussants

  • Alexandre Varnek, Université de Strasbourg
  • Cathy Lester, The Procter & Gamble Company
  • Huixiao Hong, U.S. Food and Drug Administration, National Center for Toxicological Research

Session 2 (12:30 – 3:30 p.m. EDT): Supervised and Unsupervised Approaches

This session will define and redefine terms ranging from molecular descriptors, fingerprints, tox alerts, machine learning, read-across, QSAR, univariate/multivariate analysis, classification, clustering, etc. and give an introduction to the general theory of supervised and unsupervised learning approaches, covering the concept of analogues and surrogates and how to select the right ones depending on the goal and context.


  • Andreas Bender, University of Cambridge
  • Davide Ballabio, Università degli Studi di Milano-Bicocca
  • Denis Fourches, Oerth Bio

Round Table Discussants

  • Thomas Luechtefeld, Insilica
  • Alexander Sedykh, Sciome LLC
  • Elena Fioravanzo, ToxNavigation

Day 1 Wrap-up

Day 2: Tuesday, October 4, 2022


Session 3 (8:45 – 11:45 a.m. EDT): How and When to Apply the Different Approaches

This session will provide an overview of the different possible applications of supervised and unsupervised clustering and classification approaches and how to apply them, separately or in combination, and interpret results. This session will be important to for a discussion on best practices.


  • Alexander Tropsha, University of North Carolina at Chapel Hill
  • Alessandra Roncaglioni, Istituto Mario Negri
  • Todd Martin, U.S. Environmental Protection Agency

Round Table Discussants

  • Gilles Marcou, Université de Strasbourg
  • Arianna Bassan, Innovatune
  • Tomasz Sobanski, European Chemicals Agency

Session 4 (12:30 – 3:30 p.m. EDT): Applications and Examples

The last session will provide examples of applications of different approaches for research and regulatory assessment uses.


  • Andrea Gissi, European Chemicals Agency
  • Grace Patlewicz, U.S. Environmental Protection Agency
  • Andrew Rooney and Suril Mehta, NIEHS, and Charles Bevington, U.S. Consumer Product Safety Commission

Round Table Discussants

  • Lauren Zeise, California Office of Environmental Health Hazard Assessment
  • Gino Sarcano, U.S. Environmental Protection Agency
  • Patra Volarath, U.S. Food and Drug Administration, Center for Drug Evaluation and Research
  • William Bisson, INOTIV

Day 2 Wrap-up and Adjourn

Workshop Planning Committee Members

Kamel Mansouri (Chair)
Vicki Sutherland (Co-chair)
Scott Auerbach
Jeremy Erickson
Stephen Ferguson
Rachel Frawley
Jui-Hua Hsieh
Gloria Janke
Nicole Kleinstreuer
Suril Mehta
Fred Parham
Cynthia Rider
Andrew Rooney
Kyla Taylor
Amy Wang


For questions about the workshop content, please contact Kamel Mansouri at 984-287-3187 or Vicki L. Sutherland at 984-287-3193. For logistical questions, please contact Kerri Voelker at 919-794-4710.

American Disabilities Act Accommodations Requests

Individuals with disabilities who need accommodation to participate in this event should contact Kerri Voelker at 919-794-4710. TTY users should contact the Federal TTY Relay Service at 1-800-877-8339. Requests should be made at least 5 business days in advance of the workshop.

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