February 2001 News

FETAX Not Ready for Regulatory Use

February 28, 2001

The Frog Embryo Teratogenesis Assay--Xenopus (FETAX), as currently constituted, "is not sufficiently validated or optimized to be used for regulatory applications," according to the Expert Panel that reviewed this proposed alternative method.

FETAX is an in vitro method proposed for evaluating the developmental toxicity potential of chemicals. Its possible applications include screening and prioritizing compounds for further testing, evaluating complex mixtures and environmental samples, and assessing toxicity hazards.

An Expert Panel met last May, following completion of initial development and pre-validation studies, to evaluate the validation status of FETAX. Expert Panel meetings are a key step in the extensive scientific peer-review process required for the validation and acceptance of a new alternative method in the United States. The Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) is responsible for guiding new tests through this process.

The Panel members found Xenopus "an interesting vertebrate model organism for studying developmental pathways and processes" but expressed a number of concerns, including "problems in variability" and "the need to further develop specific application, validation, and utilization criteria for FETAX." The Panel identified additional assessments that are necessary across chemicals and across laboratories, and they suggested changes in experimental protocol and performance outcomes.

Complete minutes of the meeting now are available online. The document can be downloaded in Word at this page or viewed in Adobe Portable Document Format (PDF) here.

FETAX is the third alternative method to come down the U.S. validation and regulatory acceptance pipeline. So far, two alternative methods have completed this process. The Murine Local Lymph Node Assay (LLNA), the first alternative test to be approved by federal regulatory agencies after an ICCVAM panel review, determines the potential of chemicals to cause allergic dermatitis. This assay is less painful than the old method, requires fewer animals, and uses mice rather than guinea pigs. For more details, see the Altweb news story here.

The second approved alternative method involves a "synthetic skin," called Corrositex, which can be used to test for skin corrositivity. For an Altweb news story about this new test, go here.

The recent passage of the ICCVAM Authorization Act, making ICCVAM a permanent federal panel, will help ensure the continued development and validation of alternative methods. For details see here.