Advancements in Safety Testing
The idea of the “3Rs” – Reduction in the number of animals used for a test method, Refinement of methods toward more humane treatment and Replacement of animal testing with alternative methodology – was a noble effort to advance welfare standards for animals and reduce the number of animals used in science. Yet the “3Rs” philosophy neglects to address the fundamental inadequacies of animals to predict what is safe and effective for people. In other words, even alternative methods that are based on other species will reflect the fundamental flaws of animal tests.
Today there is a total rethinking of the current paradigm of animal testing. Proposals for change include efforts by the government and industry to put more emphasis on human biology and to emphasize systems biology and computational chemistry, as well as biological pathways and networks. These emerging tools offer the promise of safety testing that is more rapid, less costly, and that accelerates the process of eliminating animal use. A recent U.S. initiative to address the problem of the scientific complexity has become known as “Toxicology for the 21st Century,” or “Tox 21.”
The ongoing revolution in biology and biotechnology is making it possible to study the effects of chemicals using cells, cellular components and tissues — preferably of human origin — rather than whole animals. These powerful new advancements should help to address a number of challenges facing the field of toxicity testing. New tests should identify changes at the molecular level, helping scientists to better predict how chemical exposures do or do not lead to certain health effects, and how they affect sensitive populations such as children. They should also enable rapid screening of chemicals, thus reducing the large backlog of industrial chemicals that have not yet been evaluated under the current regulatory system.
Some progress has been made in response to recent large government testing programs in the U.S. and the EU that require new data for a vast number of chemicals (high volume and endocrine disruptors, for example). Concerns over the cost, time, and number of animals that would have been used to test these chemicals have stimulated efforts for the validation of new alternative methods. Industry has applied a number of strategies to reduce animal use for testing required by these programs, e.g., searching for existing data; data sharing; using in silico tools to group similar chemicals; and using alternative test methods including in vitro screening assays, test batteries, and tiered testing schemes.
Health care company Allergan recently made great strides in its effort to reduce the number of animals used in product testing. The company developed an exciting new FDA-approved, cell-based assay for the testing of BOTOX. Use of this cell-based test will lead to a 95% reduction in the number of animals used in the safety testing of BOTOX. This new cell-based assay will replace the historically-used mouse LD50 test, and has several advantages over the animal assay, including that it has the potential to be automated (operate automatically with help of computers and robotics). Allergan is in the process of developing other in vitro assays, and feels that the knowledge scientists gained from developing the BOTOX in vitro assay will be invaluable when developing in vitro assays for other products.
The recent World Congress on Alternatives and Animal Use in the Life Sciences (held in Montreal, Canada in August 2011) highlighted the continuing progress in the development of new alternative methods, international cooperation in validating their use, and the increased cooperation and collaboration between many different European and U.S. laboratories. The 2009 memorandum of understanding between the U.S., European, Canadian, and Japanese alternative programs was recently expanded to include Korea. This memorandum formalized the cooperative effort to work together in validating alternative methods and to harmonize this effort internationally. The success of alternative test development and validation internationally is dependent upon the willingness of regulatory agencies from each country to accept a “valid test” as a replacement for currently used animal models. This is due in part to the differences in laws and agency regulations. The memorandum of understanding has addressed this issue by encouraging cooperation between the various international validation programs in the design, performance, and interpretation of validation studies to meet the various regulatory requirements of each country, thereby ensuring a better chance of international acceptance of the validated methods.
Several approaches that implement 21st century science into the risk assessment process are currently underway. Laboratories have begun the difficult task of trying to understand the basic mechanisms associated with chemical exposure. The Human Chemical Genomics Center in Gaithersburg, MD, for example, is using high-throughput screening to identify chemical mechanisms using genetically modified cells to monitor individual gene responses. They are using robotic systems to generate a large database of potential toxicity mechanisms for each chemical. This effort is funded by a consortium of federal agencies.
While these efforts represent an important beginning, a lot of work remains to accomplish the task of predicting human toxicity and safety without the use of animals. Various bioinformatics programs that can process and interpret large amounts of data must be developed to identify potential pathways of toxicity. Once identified, the changes in specific pathways on specific tissue function, such as the heart or nervous systems, will need to be confirmed using human cells and/or tissue models that have yet to be constructed. The hope is that the use of stem cells for regenerative medicine will provide the tissue-specific models that can be utilized for this analysis. Pilot studies to identify pathways of toxicity for a specific tissue have been initiated in an international collaborative project. Projects such as this are critical for the ultimate integration of modern, 21st century biology into human risk assessment.