acute oral toxicity

/Tag:acute oral toxicity

Acute Oral Toxicity Testing: Scientific Evidence and Practicability Should Govern Three Rs Activities

Roland Buesen, Uwe Oberholz, Ursula G. Sauer and Robert Landsiedel

Acute oral toxicity is determined for regulatory hazard classification or non-classification. The European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) recommends the following modules for acute oral toxicity testing: a) the use of the in vitro 3T3 Neutral Red Uptake (NRU) test to identify substances not requiring classification and to estimate starting doses for in vivo acute oral toxicity studies; and b) the use of data from sub-acute toxicity studies to identify substances not requiring classification. However, the application of these modules in a regulatory context would require a predefined, validated and formally accepted testing strategy and data interpretation procedure, which are not available. Furthermore, the application of the 3T3 NRU assay for starting dose estimations could in fact increase the number of animals used. Finally, only very few substances exist for which data from sub-acute or other repeated dose studies are available, but data from acute studies are not. Therefore, in practice, the prediction of acute toxicity by using sub-acute toxicity data is generally irrelevant. It could even lead to a risk of overdosing in the range-finding study, which may result in the death of many or all of the animals used.

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Exploring Waiving Opportunities for Mammalian Acute Systemic Toxicity Tests

Graepel EUSurvey

Rabea Graepel, David Asturiol, Pilar Prieto and Andrew P. Worth

A survey was carried out to explore opportunities for waiving mammalian acute systemic toxicity tests. We were interested in finding out whether data from a sub-acute toxicity test could be used to predict the outcome of an acute systemic toxicity test. The survey was directed at experts in the field of toxicity testing, and was carried out in the context of the upcoming 2018 final registration deadline for chemicals under the EU REACH Regulation. In addition to the survey, a retrospective data analysis of chemicals that had already been registered with the European Chemicals Agency, and for which both acute and sub-acute toxicity data were available, was carried out. This data analysis was focused on chemicals that were administered via the oral route. The answers to the questionnaire showed a willingness to adopt waiving opportunities. In addition, the responses showed that data from a sub-acute toxicity test or dose-range finding study might be useful for predicting chemicals that do not require classification for acute oral toxicity (LD50 > 2000mg/kg body weight). However, with the exception of substances that fall into the non-classified category, it is difficult to predict current acute oral toxicity categories.
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A Tutorial for Analysing the Cost-effectiveness of Alternative Methods for Assessing Chemical Toxicity: The Case of Acute Oral Toxicity Prediction

Hedvig Norlen, Andrew P. Worth and Silke Gabbert

Compared with traditional animal methods for toxicity testing, in vitro and in silico methods are widely considered to permit a more cost-effective assessment of chemicals. However, how to assess the cost-effectiveness of alternative methods has remained unclear. This paper offers a user-oriented tutorial for applying cost-effectiveness analysis (CEA) to alternative (non-animal) methods. The purpose is to illustrate how CEA facilitates the identification of the alternative method, or the combination of methods, that offers the highest information gain per unit of cost. We illustrate how information gains and costs of single methods and method combinations can be assessed. By using acute oral toxicity as an example, we apply CEA to a set of four in silico methods (ToxSuite, TOPKAT, TEST, ADMET Predictor), one in vitro method (the 3T3 Neutral Red Uptake cytotoxicity assay), and various combinations of these methods. Our results underline that in silico tools are more cost-effective than the in vitro test. Battery combinations of alternative methods, however, do not necessarily outperform single methods, because additional information gains from the battery are easily outweighed by additional costs.

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Determination of the Starting Dose for Acute Oral Toxicity (LD50) Testing in the Up and Down Procedure (UDP) From Cytotoxicity Data

Horst Spielmann, Elke Genschow, Manfred Liebsch and Willi Halle

To reduce the number of animals used in acute oral toxicity testing, cytotoxicity data (IC50) can be used to determine the starting dose for in vivo testing by applying the standard regression between IC50 and acute oral LD50 values in the Register of Cytotoxicity (RC). In the RC, the correlation between cytotoxicity, represented by the mean IC50 (IC50x), and the acute oral LD50 of rats and/or mice has been determined for 347 chemicals by applying the linear regression model for log-transformed pairs of IC50 versus oral LD50. The standard regression line of the two toxicity parameters is characterised by an intercept a = 0.625 and regression coefficient b = 0.435, and 252 of 347 chemicals (72.6 %) are located within a dose-range differing by not more than 0.699 (factor FG ≤ log 5) from the standard regression line. In the present study, we have used the RC and its IC50/LD50 regression model to predict the LD50 values from cytotoxicity data for nine chemicals which were tested in an evaluation study of the Up and Down Procedure (UDP). For seven of the nine chemicals, LD50 values (mg/kg) predicted from the RC were in the same doserange as LD50 values determined in vivo, while the dose-range differed by more than one order of magnitude for the two remaining chemicals. Thus, the prediction of LD50 values from cytotoxicity data was promising in this limited data set. It is proposed that a tiered in vitro/in vivo testing approach will reduce animal use in the UDP method. As the first step, the in vitro cytotoxicity of a new chemical is determined. By applying the RC regression and adapting it to the sensitivity of a specific cell line, the LD50 value (mg/kg) can be predicted from the IC50 value. The predicted LD50 dose is then used as the starting dose in the UDP. In the RC model, the precision of the prediction increases with decreasing toxic potential, and the majority of industrial chemicals (around 90%) are not toxic according to EU classification criteria.
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The Registry of Cytotoxicity: Toxicity Testing in Cell Cultures to Predict Acute Toxicity (LD50) and to Reduce Testing in Animals1

Willi Halle

This is a translation of a report on the Registry of Cytotoxicity (RC), originally published in German in 1998. The report presented an advanced in vitro method, which can significantly reduce the number of animals needed for the toxicity testing of a broad range of compounds/xenobiotics. With the RC method, it was possible to predict the oral or intravenous acute toxicity (LD50) — which is a regulatory requirement for newly developed pharmaceuticals and industrial and household chemicals — from the cytotoxicity data (mean IC50 = IC50X) obtained with mammalian cells. The RC method can be used before the in vivo test, and it does not pose any additional harm or suffering to laboratory animals. The RC method is of broad practical use: it can be applied, for example, in the pharmaceutical industry or the chemical industry in regulatory testing or in research. It is ready for validation, and could then be incorporated into OECD guidelines, thus reducing the total number of animals needed for regulatory toxicity testing. The RC method is based on the comparison of the IC50X values and the LD50 values by using linear regression analysis. With the RC method, it was possible to predict, within a predefined dose range, the acute oral LD50 for 252 of 347 xenobiotics, and the intravenous LD50 for rats and/or mice for 117 of 150 xenobiotics. Comparative studies showed that these results are highly reproducible.
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