Supplemental Acute Toxicity Protocol, October, 2000 Workshop
The EPA, along with the National
Toxicology Program and the National Institute of Environmental Health
Sciences (NIEHS), sponsored an International Workshop on In vitro
Methods held on October 17-20, 2000, to review the validation status of
available In vitro methods for predicting acute oral toxicity,
among other goals.
The October 2000 Workshop concluded that In vitro cytotoxicity data could be useful in estimating starting doses for In vivo acute toxicity testing, and in this way could also reduce the number of animals used in subsequent In vivo tests. The two candidate cytotoxicity tests recommended for use with the regression model are the neutral red uptake assays using the mouse fibroblast cell line BALB/c 3T3, and normal human kerantinocytes. Certain other cell lines/cells could also be used with the regression model to determine basal cytotoxicity, but first the correlation between the In vitro test and the In vivo test must be established quantitatively. Guidance on these In vitro tests, protocols for use of recommended tests, and a reporting template for results of In vitro tests are all contained in NIEHS (2001b), which is one of the products of the October Workshop. Further background on the October workshop can be found in NIH (2001a).
While the formal request to EPA from NIH that would ask the Agency to accept or reject these protocols has not yet been received (nor have these methods been incorporated in OECD or the EPA acute toxicity test guidelines), the findings of this workshop included a recommendation to all Agencies participating in ICCVAM to consider the use of these In vitro cytotoxicity tests as supplements to the current acute oral In vivo acute toxicity protocols. These In vitro cytotoxicity protocols were recognized earlier in Steven Johnson's letter of October 30, 2001. The In vitro tests are supplements to, not replacements for, the OECD acute toxicity test guideline 425 (known as the Up-and-Down Procedure) which is currently recommended for use in the HPV Challenge Program. The new In vitro tests are intended to better estimate the starting doses for new In vivo acute oral toxicity studies conducted under the HPV Challenge.
We encourage those participating in the HPV Challenge Program to consider using the recommended In vitro tests noted here as a supplemental component in conducting any new In vivo acute oral toxicity studies under the HPV Challenge Program, to note the intention to use these protocols in HPV Challenge test plans submitted to EPA, and to summarize the results using the recommended reporting template. This information on the In vitro template should accompany results from the In vivo acute oral tests, and be provided to EPA as part of the HPV Challenge Program. The October workshop guidance documents, and the recommended reporting template, for the recommended In vitro tests can be found below. The ICCVAM website - http://iccvam.niehs.nih.gov/methods/invitro.htm? - should be consulted for any future updates to the In vitro guidance methodologies prior to proceeding with testing.
In order to gain more familiarity with these methods, technical experts from industry and other organizations were invited to a workshop sponsored by EPA, NIEHS, and others on these In vitro methods. The workshop was held February 19-21, 2001 (see the ICCVAM website at http://iccvam.niehs.nih.gov/meetings/schedule.htm for more details).
Report of the International Workshop on In vitro Methods for Assessing Acute Systemic Toxicity, NIH Publication No. 01-4499. August 2001
Guidance Document on Using In vitro Data to Estimate In vivo Starting Doses for Acute Toxicity. NIH Publication No. 01-4500. August 2001
Standard Test Reporting Template
Any updates to this methodology can be found at the The Interagency Coordinating Committee on the Validation of Alternative Methods of the The National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods http://iccvam.niehs.nih.gov/methods/invitro.htm?