http://echa.europa.eu SIEF Webinar: Weight of Evidence (WoE) Approach
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SIEF Webinar: Weight of Evidence (WoE) Approach
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Contents
• WoE concept – when it can be used
• Steps to building a WoE case
• Experience with registration dossiers to date
• Case studies
• Conclusions
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When to use WoE?
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Weight of Evidence – the concept (1)
• In REACH the approach is provided as an option in Annex XI for meeting information requirements in Annexes VII-X
• Evidence-based approach, involving an assessment of the relative weights of different pieces of the available information – strengths versus weaknesses
• Requires expert judgement
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Weight of Evidence – the concept (2)
• Weights will be influenced by e.g. the following factors:– quality of the data, – consistency of results/data, – nature and severity of effects, – relevance of the information for the given regulatory
endpoint.
• In all cases the relevance, reliability and adequacy for the purpose have to be considered
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Weight of Evidence – the concept (3)
• WoE is case dependent and endpoint-specific• Use influenced by the relation between
– the amount of information needed– the importance of the decision to be taken by
Registrant– the likelihood of, and consequences for, the decision
being wrong
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Legal basis (Annex XI 1.2)
…evidence from several independent sources … while the information from each single source alone is regarded insufficient…
…from the use of newly developed test methods … or from an international test method recognised by the Commission or the Agency as being equivalent…
Where sufficient WoE … is available:– further testing on vertebrate animals … shall be omitted,– further testing not involving vertebrate animals may be omitted.
In all cases adequate and reliable documentation shall be provided.
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Why is WoE approach useful?
• It makes use of all available information
• Can use less reliable studies/information when included in a pool of information
• Used in developing Integrated Testing Strategies (ITS)
• May avoid the need for further testing
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Steps to building WoE case1) Gather all information
� Literature search (e.g. scientific journals, handbooks, databases)
� Read across from similar substances
� Q(S)AR predictions
� Data from existing studies
� Newly developed test methods
� In vitro studies
� Epidemiological dataThe more the better!
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Steps to building WoE case
2) Assess the data
� Are there 2 or more pieces of information?� Is the information relevant to the endpoint?� Is there adequate documentation of studies?� What is reliability/weight of each piece of data?� Is there consistency in results?� Is the combined weight substantial?
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Steps to building WoE case
3) Draw a conclusion using expert judgement
� Integrate and compare different pieces of information
� Justify weight assigned to each piece of data
� Take into account:ReliabilityRelevanceAdequacy
� Expert Judgement is vital in the construction and appraisal of the WoE package
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Steps to building a WoE
4. Document your case in IUCLID 5
� Adequate documentation for each piece of evidence = endpoint study record in IUCLID 5 for every piece of information
� Purpose Flag = Weight of Evidence
� Prepare Robust Study Summaries (RSS) for each study (also recommended for 1-10 tonne dossiers)
� Record reliability score
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Steps to building a WoE
4. Document your case in IUCLID 5 contd.
� For studies with limited information, consider flagging as supporting study instead
� Reminder: minimum of one complete endpoint study record always required - key study, waiver with justification or weight of evidence
� Create an “Endpoint study summary ” to document conclusion of weight of evidence and justification for using this evidence instead of standard testing
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Our Expectations
• Sufficient details provided for each piece of evidence to allow us to evaluate the overall evidence in an unbiased way
• The combined information allows for a conclusion to be drawn on the relevant endpoint
• The judgement made by the registrant is clearly documented and reported – in IUCLID 5 and CSR
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Our Experience with registration dossiers to date
• Registrants are not always applying a WoE approach when it could be used
• WoE approach flagged but only 1 study reported, e.g. single QSARprediction for biodegradation. Several sources of evidence required for WoE, each with its own study record.
• Insufficient documentation and detail provided for each available data point
• Incorrect use of WoE flag for waiving a study on the grounds of lack of exposure. In this case, indicate in data waiving field the reason ‘exposure considerations’ and provide adequate justification.
• Good examples too, e.g. difficult-to test substance, 2 experimental results for short-term Daphnia toxicity and 1 QSAR prediction. Conclusion on endpoint made in endpoint summary.
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Case Study (1)
WoE applied appropriately: Endpoint Study Record (a)
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Case Study (1) contd.
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Endpoint Study Record (b)
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Endpoint Study Record (b) contd.
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Endpoint Summary
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Case Study 2: WoE inadequate
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Case Study 2: WoE inadequate contd.
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Conclusions
• WoE is useful approach to fulfil information requirements
• Makes use of all available information for an endpoint
• Requires expert judgement – every case different
• Clear, transparent documentation and argumentation essential
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Links to relevant guidance
• REACH Guidance on information requirements and chemical safety assessment http://guidance.echa.europa.eu/docs/guidance_document/information_requirements_en.htm?time=1259066690In particular:� Part B: Hazard Assessment� Chapter R.4: Evaluation of available information� Chapters R.7a, R.7b, R.7c: Endpoint specific guidance
• Weight of Evidence Manual – to be published
• Data Submission Manual 5 How to Complete a Technical Dossier for Registrations and PPORD Notifications (Release 2.1) – to be published