The final step after the validation study and peer review is obtaining regulatory acceptance. The data collected during the first three steps will be used to support the eventual acceptance in the regulatory context, such as the OECD Guidelines for chemical testing and the ICH Guidelines for pharmaceutical testing, and may undergo review for potential adoption as an official test method. It is important to note that the acceptance process can vary per country (Ref13).

Regulatory acceptance of an in vitro test means that if an alternative test is approved by regulatory authorities, it can be used as an official tool to provide information that meets specific regulatory requirements (Ref6). Regulators often wait for a method to be formally recognized at an international level before deciding to accept it for their own purposes, even though they are not obligated to do so (Ref34).

Key Criteria for Regulatory Acceptance of a Test Method

• ​Application of the method provides data that adequately predicts the end-point of interest in that it demonstrates either a linkage between (i) the new test and an existing test method or (ii) the new test and effects in the target species.
• ​The method generates data for risk assessment purposes that are at least as useful as, and preferably better than, those obtained using existing methods. This will give a comparable or better level of protection for human health or the environment.
• ​There are adequate testing data for chemicals and products representative of the type of chemicals administered by the regulatory programme or agency (e.g., pesticides, cosmetics).
• ​The test should be robust and transferable and allow for standardisation. If highly specialised equipment, materials or expertise are required, efforts should be sought to facilitate transferability. This is an important criterion to be considered at an early stage of a validation study. According to current OECD policy, the test should not require equipment or material from a unique source. This would prevent the acceptance of patented methods.
• ​The test is cost effective and likely to be used.
• ​Justification (scientific, ethical, economic) should be provided for the new method with respect to any existing methods available (Ref54).