National Toxicology Program

Other Validation Study Documents

The In Vitro Cytotoxicity Validation Study was a joint effort of NICEATM and the European Centre for the Validation of Alternative Methods (ECVAM). It generated data using in vitro basal cytotoxicity assays with rodent (mouse fibroblast 3T3) and human (normal human keratinocyte) cells to predict rodent in vivo LD₅₀ data and human in vivo lethal blood concentration data so as to further the development of in vitro predictive models for human acute toxicity.

IC₂₀, IC₅₀, and IC₈₀ values were generated by testing 72 chemicals using the in vitro basal cytotoxicity test methods. The IC₅₀ values were used with IC₅₀-LD₅₀ regression formulas developed from Registry of Cytotoxicity to predict starting doses for acute oral toxicity tests (i.e., the Up-and-Down Procedure and the Acute Toxic Class method). Please refer to the Background Review Document for more study information on the prediction of rodent acute oral toxicity using the in vitro basal cytotoxicity test methods. The ICx values and human lethal and sublethal blood concentrations will be used by ECVAM to develop a human prediction model.

Study Objectives

• Further standardize and optimize the in vitro cytotoxicity test method protocols to maximize test method reliability (intralaboratory repeatability, intra- and inter-laboratory reproducibility)
• Assess the accuracy of the standardized in vitro cytotoxicity test methods for estimating rodent oral LD₅₀ values across the five United Nations Globally Harmonised System of Classification and Labelling of Chemicals (GHS) categories of acute oral toxicity, as well as unclassified toxicities
• Estimate the reduction and refinement in animal use achievable from using in vitro test methods to identify starting doses for in vivo acute toxicity tests
• Develop high quality in vitro acute oral lethality and in vitro cytotoxicity test method databases that can be used to support investigations of other in vitro test methods necessary to improve the prediction of in vivo acute oral lethality

Additional Documents

• Report of the International Workshop on In Vitro Methods for Assessing Acute Systemic Toxicity. 2001.
  [NIH Publication No. 01-4499] [PDF (2.4 MB) or HTML]


• Guidance Document on Using In Vitro Data to Estimate In Vivo Starting Doses for Acute Toxicity. 2001.
  [NIH Publication No. 01-4500] [PDF (432 K) or HTML]


• LD₅₀ Database [Excel Spreadsheet]
• IC₅₀ and LD₅₀ Database [Excel Spreadsheet]