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Welcome

Welcome to the Adverse Outcome Pathway Exploratory Research Assistant (AOPERA)!

AOPERA is designed to identify existing tools that can assist you in the process of linking your chemical to an adverse outcome pathway (AOP). This informational tool is specifically targeted to users with an uncharacterized chemical and limited toxicity information, but can also assist you if you already have information that links your uncharacterized chemical to a molecular initiating event (MIE), a key event (KE), or an adverse outcome (AO), or if you have a characterized chemical.

AOPERA explains the four-step process of linking an uncharacterized chemical to an AOP, and provides descriptions and links to the tools relevant to the specific information gaps you need to address for your chemical.

At this point, you have either a characterized or uncharacterized chemical and are at one of the four "Levels of Knowledge" depicted in Figure 1. Please select the Level that corresponds to your current state.

Level OverviewFigure 1

Level 0

I do not know anything about my chemical.

Level 1

I know my chemical causes an AO, but I do not know how

Level 2

I know my chemical causes a Key Event, but I do not know upstream or downstream MIE, KEs, or AOs.

Level 3

I know my chemical causes an MIE, but I do not know downstream key events or AO

Level 0

Your current-state Level of Knowledge is Level 0 - "I do not know anything about my chemical." Don't worry, AOPERA was designed for you! There are four "Steps" within Level 0 that you will need to proceed through in order to link your chemical to an AOP. It is recommended that you start with Step 1; however, you may skip a step using the buttons if you already have the output information from that step.

If your chemical is characterized and you have its Chemical Abstracts Service Registry Number (CASRN), you may proceed directly to Step 3.

Overview of StepsFigure 2

Step 1

The objective of Level 0 - Step 1 is to link your uncharacterized chemical directly to MIEs, KEs, or AOs. There are six tools and informational resources that may be able to assist you with this step. Learn More.

Step 2

The objective of Level 0 - Step 2 is to identify analogs for your uncharacterized chemical. There are ten tools and informational resources that may be able to assist you with this step. Learn More.

Step 3

The objective of Level 0 - Step 3 is to link a characterized chemical to MIEs, KEs, or AOs. The characterized chemical will either be an analog that you identified in Step 2, or your chemical if you started with a characterized chemical and skipped Steps 1 and 2. Learn More.

Step 4

The objective of Level 0 - Step 4 is to identify AOPs that contain the MIEs, KEs, or AOs that your chemical was linked to in Step 3. There are two tools and informational resources that may be able to assist you with this step. Learn More.

Step 1 Resources

Below you will find information pertaining to tools and resources that can be used to link your uncharacterized chemical directly to MIEs, KEs, or AOs.

Step 1 OverviewFigure 3

VEGA QSAR

Using the VEGA platform, you can access a series of QSAR (quantitative structure-activity relationship) models for regulatory purposes, or develop your own model for research purposes. QSAR models are models linking a property or effect, such as boiling point or toxicity, to parameters associated with chemical structure, such as certain molecular descriptors. They can be used to assess chemical substances within the so-called in silico approach (as an analogy to the in vitro and in vivo approach).

OECD QSAR Toolbox

The OECD QSAR Toolbox is a software application intended for use by governments, the chemical industry and other stakeholders to fill gaps in (eco)toxicity data needed for assessing the hazards of chemicals. The Toolbox incorporates information and tools from various sources into a logical workflow. Crucial to this workflow is grouping chemicals into chemical categories. The seminal features of the Toolbox are identification of relevant structural characteristics and potential mechanism or mode of action of a target chemical; identification of other chemicals that have the same structural characteristics and/or mechanism or mode of action; and use of existing experimental data to fill the data gap(s). The toolbox also provides an approach to predict skin sensitisation based on the concept of Adverse Outcome Pathways.

Toxicity Estimation Software Tool (TEST)

TEST allows a user to estimate toxicity without requiring any external programs. Users input a chemical to evaluate by drawing it in an included chemical sketcher window, entering a structure text file, or importing it from an included database of structures. Once entered, the toxicity is estimated using one of several advanced QSAR methodologies. The required molecular descriptors are calculated within TEST.

OncoLogic

The OncoLogic™ model is a predictive system that mimics the judgment of human experts by following sets of knowledge rules based on studies of how chemicals cause cancer in animals and humans. OncoLogic™ asks for chemical and use information from the user, and following the knowledge rules incorporated into the system, uses the responses to construct an estimation of the carcinogenicity potential of the chemical.

Mcule

Mcule is an online drug discovery platform. It offers a unique solution for pharma and biotech companies by providing the highest quality purchasable compound database and molecular modeling tools. Applications include: 1-Click Docking, 1-Click Scaffold Hop, Property calculator, and Toxicity checker.

EPA's New Chemical Categories Document

EPA groups Premanufacture Notice (PMN) chemicals with shared chemical and toxicological properties into categories, enabling both PMN submitters and EPA reviewers to benefit from the accumulated data and past decisional precedents allowing reviews to be facilitated. Currently, there are a total of 56 categories. Establishing these categories has streamlined the process for Agency review of new chemical substances. This document describes the molecular structure a new chemical must have to be included in the category, boundary conditions such as molecular weight, equivalent weight, the log of the octanol/water partition coefficient (log P), or water solubility, that would determine inclusion in (or exclusion from) a category, and standard hazard and fate tests to address concerns for the category.

Step 2 Resources

Below you will find information pertaining to tools and resources that can be used to identify analogs for your uncharacterized chemical.

Step 2 OverviewFigure 4

Toxicity Estimation Software Tool (TEST)

TEST allows a user to estimate toxicity without requiring any external programs. Users input a chemical to evaluate by drawing it in an included chemical sketcher window, entering a structure text file, or importing it from an included database of structures. Once entered, the toxicity is estimated using one of several advanced QSAR methodologies. The required molecular descriptors are calculated within TEST.

Chemistry Dashboard (CompTox)

The Chemistry Dashboard is part of a suite of dashboards developed by EPA to help evaluate the safety of chemicals. The Chemistry Dashboard provides access to a variety of information on over 700,000 chemicals currently in use. Within the Chemistry Dashboard, users can access chemical structures, experimental and predicted physicochemical and toxicity data, and additional links to relevant websites and applications. It maps curated physicochemical property data associated with chemical substances to their corresponding chemical structures.

eMolecules

eMolecules empowers researchers to explore uncharted chemical and biological spaces and deliver more efficient drug-discovery programs. One of its aims is to facilitate exploration of uncharted chemical and biological space with its database of over 8 million compounds.

PubChem

PubChem is an open chemistry database at the National Institutes of Health (NIH). PubChem collects information on chemical structures, identifiers, chemical and physical properties, biological activities, patents, health, safety, toxicity data, and many others. Since the launch in 2004, PubChem has become a key chemical information resource for scientists, students, and the general public.

ChemIDplus (part of TOXNET)

ChemIDplus gives you access to structure and nomenclature authority files used to identify chemical substances cited in the National Library of Medicine® (NLM) databases. You can also find structure searching and links to other biomedical resources at NLM and on the Internet. It contains more than 400,000 chemical records, including 3D structure models for more than 300,000 chemicals and 645,000 variations.

EURL ECVAM JRC QSAR Model Database

Quantitative Structure-Activity relationship (QSAR) models can be used to predict properties needed for hazard and risk assessment and for which data gaps exist. The JRC QSAR Model Database provides information on the validity of QSAR models that have been submitted to the JRC. The database is intended to help to identify valid QSARs.

Mcule

Mcule is an online drug discovery platform. It offers a unique solution for pharma and biotech companies by providing the highest quality purchasable compound database and molecular modeling tools. Applications include: 1-Click Docking, 1-Click Scaffold Hop, Property calculator, and Toxicity checker.

VEGA QSAR

Using the VEGA platform, you can access a series of QSAR (quantitative structure-activity relationship) models for regulatory purposes, or develop your own model for research purposes. QSAR models are models linking a property or effect, such as boiling point or toxicity, to parameters associated with chemical structure, such as certain molecular descriptors. They can be used to assess chemical substances within the so-called in silico approach (as an analogy to the in vitro and in vivo approach).

Analog Identification Methodology (AIM)

The Analog Identification Methodology (AIM) is a downloadable software program that facilitates analog analysis and data identification in support of chemical assessment or read-across approaches to help scientists and chemical managers predict potential hazards of untested chemicals. Key characteristics of the program include: ability to conduct comprehensive structural analysis of chemicals using over 700 individual atoms, groups and super fragments indexed in a predefined database; use of structural analysis to match potential analogs from an inventory of over 86,000 chemicals with publicly available measured data and links to the data sources; and ability to recode defined substitutions or exclusion rules for the refinement of analog search strategies.

ChemSpider

ChemSpider is a free chemical structure database providing fast access to over 63 million structures, properties, and associated information. By integrating and linking compounds from ~280 data sources, ChemSpider enables researchers to discover the most comprehensive view of freely available chemical data from a single online search. It is owned by the Royal Society of Chemistry. ChemSpider builds on the collected sources by adding additional properties, related information, and links back to original data sources. ChemSpider offers text and structure searching to find compounds of interest and provides unique services to improve this data by curation and annotation, and to integrate it with users' applications.

ChemMaps.com

ChemMaps.com is a webserver developed in JavaScript to interact with a chemical space. It is available for the drug space and for environmental space and was developed in collaboration with the National Institute of Environmental Health Sciences (NIEHS) and the Fourches' lab in North Carolina State University.

Step 3 Resources

Below you will find information pertaining to tools and resources that can be used to link a characterized chemical to MIEs, KEs, or AOs.

Step 3 OverviewFigure 5

ToxCast (Toxicity Forecaster)

The ToxCast Dashboard helps users examine high-throughput assay data to inform chemical safety decisions. To date, the ToxCast Dashboard has data on over 9,000 chemicals and information from more than 1,000 high-throughput assay endpoint components. Once the user selects the chemicals and assays of interest, they can then explore the biological activity for the chemical-assay combinations. Results from the selections are shown with tables, graphs and charts that can be downloaded by the user.

VEGA QSAR

Using the VEGA platform, you can access a series of QSAR (quantitative structure-activity relationship) models for regulatory purposes, or develop your own model for research purposes. QSAR models are models linking a property or effect, such as boiling point or toxicity, to parameters associated with chemical structure, such as certain molecular descriptors. They can be used to assess chemical substances within the so-called in silico approach (as an analogy to the in vitro and in vivo approach).

ACToR

EPA’s Aggregated Computational Toxicology Online Resource (ACToR) aggregates data from thousands of public sources on over 500,000 chemicals. ACToR is also the data and web applications warehouse for EPA’s computational toxicology information which includes high-throughput screening, chemical exposure, sustainable chemistry (chemical structures and physicochemical properties) and virtual tissues data. ACToR is the warehouse for EPA web applications which can be used to explore and visualize complex computational toxicology information.

ATSDR Toxic Substances Portal

The ATSDR Toxic Substances Portal provides access to important information about toxic substances and how they affect our health. Information about toxic substances includes: characteristics, exposure risks, associated health effects, and related CDC and ATSDR health studies and assessments.

Pharos Chemical and Material Library

Pharos is an independent database of chemicals, polymers, metals, and other substances that includes 88,024 records and counting. Using dozens of scientific lists for specific human and environmental health hazards, it aggregates a vast array of information used for analyzing chemicals of concern. The tool also provides a wealth of information on certifications and standards used to measure the health impacts of products, including VOC content and emissions, recycled and bio-based content, and much more.

EDSP21

Beginning in 2012, the Endocrine Disruptor Screening Program (EDSP) began a multi-year transition to validate and more efficiently use computational toxicology methods and high throughput screens that will allow EPA to more quickly and cost-effectively assess potential chemical toxicity. The initiative, referred to as EDSP21 – or EDSP in the 21st century – aims to use computational or in silico models and molecular based in vitro high-throughput screening (HTS) assays to prioritize and screen chemicals to determine their potential to interact with the estrogen, androgen or thyroid (E, A, or T) bioactivity.

Reactome

Reactome is an open-source, open access, manually curated and peer-reviewed pathway database. Reactome's goal is to provide intuitive bioinformatics tools for the visualization, interpretation and analysis of pathway knowledge to support basic and clinical research, genome analysis, modeling, systems biology and education.

OECD QSAR Toolbox

The OECD QSAR Toolbox is a software application intended for use by governments, the chemical industry and other stakeholders to fill gaps in (eco)toxicity data needed for assessing the hazards of chemicals. The Toolbox incorporates information and tools from various sources into a logical workflow. Crucial to this workflow is grouping chemicals into chemical categories. The seminal features of the Toolbox are identification of relevant structural characteristics and potential mechanism or mode of action of a target chemical; identification of other chemicals that have the same structural characteristics and/or mechanism or mode of action; and use of existing experimental data to fill the data gap(s). The toolbox also provides an approach to predict skin sensitisation based on the concept of Adverse Outcome Pathways.

Toxicity Estimation Software Tool (TEST)

TEST allows a user to estimate toxicity without requiring any external programs. Users input a chemical to evaluate by drawing it in an included chemical sketcher window, entering a structure text file, or importing it from an included database of structures. Once entered, the toxicity is estimated using one of several advanced QSAR methodologies. The required molecular descriptors are calculated within TEST.

EPA's New Chemical Categories Document

EPA groups Premanufacture Notice (PMN) chemicals with shared chemical and toxicological properties into categories, enabling both PMN submitters and EPA reviewers to benefit from the accumulated data and past decisional precedents allowing reviews to be facilitated. Currently, there are a total of 56 categories. Establishing these categories has streamlined the process for Agency review of new chemical substances. This document describes the molecular structure a new chemical must have to be included in the category, boundary conditions such as molecular weight, equivalent weight, the log of the octanol/water partition coefficient (log P), or water solubility, that would determine inclusion in (or exclusion from) a category, and standard hazard and fate tests to address concerns for the category.

WikiPathways

WikiPathways is an open, collaborative platform that includes a graphical pathway editing tool and integrated databases covering major gene, protein, and small-molecule systems.

ChemView

The ChemView database contains information on chemical health and safety data received by EPA and EPA's assessments and regulatory actions for specific chemicals under the Toxic Substances Control Act (TSCA). ChemView contains no confidential business information (CBI).

OncoLogic

The OncoLogic™ model is a predictive system that mimics the judgment of human experts by following sets of knowledge rules based on studies of how chemicals cause cancer in animals and humans. OncoLogic™ asks for chemical and use information from the user, and following the knowledge rules incorporated into the system, uses the responses to construct an estimation of the carcinogenicity potential of the chemical.

Mcule

Mcule is an online drug discovery platform. It offers a unique solution for pharma and biotech companies by providing the highest quality purchasable compound database and molecular modeling tools. Applications include: 1-Click Docking, 1-Click Scaffold Hop, Property calculator, and Toxicity checker.

Mol-Instincts Database

MOL-Instincts is a database containing property data and molecular information of chemical compounds for industrial applications. It is also meant to be used for research and development in the many fields of science and engineering. The database includes thermodynamic properties, physico-chemical properties, transport properties, quantum-related information, molecular descriptors, drug-related properties, spectra information, optimized 3D structure, and orbital information.

Distributed Structure-Searchable Toxicity Database Network (DSSTox)

DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology. A distinguishing feature of this effort is the accurate mapping of bioassay and physicochemical property data associated with chemical substances to their corresponding chemical structures. 

EURL ECVAM JRC QSAR Model Database

Quantitative Structure-Activity relationship (QSAR) models can be used to predict properties needed for hazard and risk assessment and for which data gaps exist. The JRC QSAR Model Database provides information on the validity of QSAR models that have been submitted to the JRC. The database is intended to help to identify valid QSARs.

EPA's Virtual Tissue Models (Embryo, Blood Vessel Development, Developmental Toxicity, and Thyroid)

Virtual tissue models use new computational methods to construct advanced computer models capable of simulating how chemicals may affect human development. Virtual Embryo models simulate biological interactions observed during development and predict when chemicals disrupt key biological events in pathways that are thought to lead to adverse effects. The goal of the Virtual Thyroid is to model the potential impact of chemical disruption of thyroid function and subsequent adverse impacts on brain development.

OpenFoodTox (EFSA)

The OpenFoodTox database gives information on over 4,000 chemical substances, related EU legislation, the EFSA output identifying their critical effects, and the safe levels set by EFSA scientific panels, such as tolerable or acceptable daily intakes.

NICEATM Integrated Chemical Environment (ICE)

The Integrated Chemical Environment (ICE) provides high-quality, curated data from NICEATM and its partners as well as other data resources and tools to support development of new approaches for assessing chemical safety. ICE allows users to easily query and integrate data streams that can then be explored interactively via table or graphic formats. The Integrator currently provides access to data for about 10,000 chemicals; endpoints include acute oral toxicity, skin and eye irritation, skin sensitization, and endocrine activity.


TOXNET

Comparative Toxicogenomics Database (CTD)

CTD is a robust, publicly available database that aims to advance understanding about how environmental exposures affect human health. It provides manually curated information about chemical–gene/protein interactions, chemical–disease and gene–disease relationships. These data are integrated with functional and pathway data to aid in development of hypotheses about the mechanisms underlying environmentally influenced diseases.

Chemical Carcinogenesis Research Information System (CCRIS)

The CCRIS database contains chemical records with carcinogenicity, mutagenicity, tumor promotion, and tumor inhibition test results. It was developed by the National Cancer Institute (NCI). Data are derived from studies cited in primary journals, current awareness tools, NCI reports, and other sources. Test results have been reviewed by experts in carcinogenesis and mutagenesis.


Literature Search - Supporting Resources

Chemistry Dashboard ("CompTox")

The Chemistry Dashboard is part of a suite of dashboards developed by EPA to help evaluate the safety of chemicals. The Chemistry Dashboard provides access to a variety of information on over 700,000 chemicals currently in use. Within the Chemistry Dashboard, users can access chemical structures, experimental and predicted physicochemical and toxicity data, and additional links to relevant websites and applications. It maps curated physicochemical property data associated with chemical substances to their corresponding chemical structures.

ChemSpider

ChemSpider is a free chemical structure database providing fast access to over 63 million structures, properties, and associated information. By integrating and linking compounds from ~280 data sources, ChemSpider enables researchers to discover the most comprehensive view of freely available chemical data from a single online search. It is owned by the Royal Society of Chemistry. ChemSpider offers text and structure searching to find compounds of interest and provides unique services to improve this data by curation and annotation, and to integrate it with users’ applications.

eChemPortal

eChemPortal provides free public access to information on properties of chemicals: physical chemical properties, ecotoxicity, environmental fate and behavior, and toxicity. eChemPortal allows simultaneous searching of reports and datasets by chemical name and number, by chemical property, and by GHS classification.

QuickGO

QuickGO is a web interface developed by the European Molecular Biology Laboratory - European Bioinformatics Institute (EMBL-EBI). QuickGO is a fast web-based browser of the Gene Ontology and Gene Ontology annotation data.

AmiGO

AmiGO 2 is a project to create the next generation of AmiGO--the current official web-based set of tools for searching and browsing the Gene Ontology database.

International Toxicity Estimates for Risk (ITER)

ITER contains data in support of human health risk assessments. It is compiled by Toxicology Excellence for Risk Assessment (TERA) and contains data from CDC/ATSDR, Health Canada, RIVM, U.S. EPA, IARC, NSF International and independent parties offering peer-reviewed risk values. ITER provides comparison charts of international risk assessment information and explains differences in risk values derived by different organizations.

Literature Search - TOXNET

GENE-TOX

GENE-TOX provides genetic toxicology (mutagenicity) test data from expert peer review of open scientific literature for more than 3,000 chemicals from the United States Environmental Protection Agency (EPA). GENE-TOX was established to select assay systems for evaluation, review data in the scientific literature, and recommend proper testing protocols and evaluation procedures for these systems.

Hazardous Substances Data Bank (HSDB)

HSDB is a toxicology database that focuses on the toxicology of potentially hazardous chemicals. It provides information on human exposure, industrial hygiene, emergency handling procedures, environmental fate, regulatory requirements, nanomaterials, and related areas. The information in HSDB has been assessed by a Scientific Review Panel.

TOXLINE

TOXLINE is a bibliographic database with an assortment of citations from specialized journals and other sources. It provides references covering the biochemical, pharmacological, physiological, and toxicological effects of drugs and other chemicals. Most of TOXLINE's bibliographic citations contain abstracts and/or indexing terms and Chemical Abstract Service (CAS) Registry Numbers.

LactMed (Drugs and Lactation DB)

The LactMed® database contains information on drugs and other chemicals to which breastfeeding mothers may be exposed. It includes information on the levels of such substances in breast milk and infant blood, and the possible adverse effects in the nursing infant. Suggested therapeutic alternatives to those drugs are provided, where appropriate. All data are derived from the scientific literature and fully referenced. A peer review panel reviews the data to assure scientific validity and currency.

DART (Developmental and Reproductive Toxicology DB)

DART provides more than 400,000 journal references covering teratology and other aspects of developmental and reproductive toxicology. DART is funded by the U.S. Environmental Protection Agency, the National Institute of Environmental Health Sciences, the National Center for Toxicological Research of the Food and Drug Administration, and the NLM.

Step 4 Resources

Below you will find information pertaining to tools and resources that can be used to identify AOPs that contain the MIEs, KEs, or AOs that your chemical was linked to in Step 3.

Step 4 OverviewFigure 6

e.AOP.Portal

The e.AOP.Portal enables search functionality within the Adverse Outcome Pathway Knowledge Base (AOP-KB). The AOP-KB is a project launched by the OECD to enable the scientific community, in one central location, to share, develop and discuss their AOP related knowledge. It allows all stakeholders to build AOPs by entering and then linking information about MIEs, KEs, AOs and Chemical Initiators. Knowing that pathway elements are not necessarily unique to a single AOP, value is added to existing knowledge by facilitating the re-use of MIE, KE and AO information in multiple AOPs, which prevents redundancy and make the collective knowledge about those entities available in all AOPs in which they appear."

AOP-Wiki

The AOP-Wiki provides a system that organizes, via crowd-sourcing, the available knowledge and published research into a verbal description of individual pathways, using a user friendly Wiki interface. Controlled-vocabulary drop-down lists from which to select Methods, Actions, Biological Objects, Life stages, Species etc. related to the AOP simplify the entry of ontology-based information.

Effectopedia

Effectopedia is an open-knowledge and structured platform able to display quantitative information on AOPs. It is a collaborative tool designed to facilitate the interdisciplinary efforts for delineating AOPs in an encyclopedic manner with greater predictive power.

AOP Xplorer

The AOP Xplorer is a computational tool that enables automated graphical representation of AOPs and networks among them. The Xplorer is currently being developed.

Reactome

Reactome is an open-source, open access, manually curated and peer-reviewed pathway database. Reactome's goal is to provide intuitive bioinformatics tools for the visualization, interpretation and analysis of pathway knowledge to support basic and clinical research, genome analysis, modeling, systems biology and education.

Levels 1, 2, or 3

Your current-state Level of Knowledge is either Level 1, 2, or 3. This means that you have already identified that your chemical is linked to at least one MIE, KE, or AO.

Steps 1 - 3Figure 7

You should proceed directly to Level 0 - Step 4 to identify AOPs that contain the MIEs, KEs, or AOs that your chemical is linked to. Additionally, you may want to try to identify more MIEs, KEs, or AOs that your chemical is linked to, in which case you should start at Level 0 - Step 1 if your chemical is uncharacterized (no CASRN) or Level 0 - Step 3 if your chemical is characterized.