Is there an independent review of QSAR models?
ECHA does not intend to produce a list of ‘approved’ models, because the value of a model depends on how it is used. (See FAQ: ‘What makes a good QSAR model?’) Every user of QSARs needs to be aware that QSAR models are only appropriate and reliable for specific sets of chemicals. A highly reliable model will not produce reliable results for chemicals that lie outside the domain of applicability. In addition, models may be suitable for different regulatory functions: risk assessment, classification and labelling or prioritisation, because each makes different demands on the model.
In terms of the form of the outputs, the QSAR Model Reporting Format (QMRF) checks that a certain number of pieces of information are given. However, such an assessment is carried out on the basis of the values provided by the developer of the model, and these are not checked independently.
The EC funded ANTARES project is evaluating existing models which could be used for REACH. Hundreds of possible models have been identified and listed, which theoretically could be used for tens of REACH endpoints. ANTARES is currently checking the performance of the QSAR models for several endpoints: carcinogenicity, mutagenicity, LD50, fish and daphnia acture toxicity, bioconcentration factor, ready biodegradability and logP.
Given the range of endpoints, the vast numbers of chemicals, the large palette of mathematical algorithms available, and the potential to use tens of thousands of chemical fragments and thousands of chemical descriptors to build a predictive model, it is clearly possible for future scientists to generate huge numbers of QSAR models. It is easy to imagine an explosion in the number of useable models, many with quite similar performance.
1) ANTARES project. www.antares-life.eu
Several platforms of QSAR models exist. The ANTARES project lists hundreds of QSAR models, tens of them are freely available.
Some well known platforms are:
VEGA: The ORCHESTRA project, with ANTARES, has developed the VEGA platform, which incorporates CAESAR and T.E.S.T. models into a single framework. An advantage of the VEGA platform is the facilitated and supported user-access: supporting information, tutorials and videos are all available on the web site. It has been developed from the point of view of the user, and of the REACH requirements. Each model produces not only a predicted value, but also many pages of explanation and assessment of its reliability.
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