Alternatives to animal testing: current status and future perspectives
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On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book “The Principles of Humane Experimental Technique” by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on “Toxicology in the twenty-first Century”, as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper.
KeywordsAlternatives to animal testing ZEBET 3Rs Replacement Reduction Refinement
On the future of ZEBET
Some general considerations and thoughts
While finalizing the schedule and program of the 20th anniversary symposium, ZEBET staff were highly interested in discussing the possible future direction of the department in order to provide a proposal on how the future of ZEBET might look like, as a milestone not too far away, let us say—maybe in the forthcoming one or two decades.
Before going into what ZEBET’s future might look like, it is worthwhile to assess the status quo and to praise what has been achieved during the first 20 years at this German institution. Thus, the initial focus of this section will be the current situation at ZEBET, how it is organized and equipped, and what are its main tasks and commitments. In addition, the current situation of animals used for scientific purposes will be assessed, their numbers, and the trends in alternatives to animal testing.
Current status of animal experimentation in Europe
For comparison, a USDA/APHIS census estimated that a total of 17–22 million animals were used in research and testing in the US in 1983 (US Congress, Office of Technology Assessment 1986). However, a more recent independent estimate suggests up to 80 million animals used, in part due to the advent of transgenic animals (Carbone 2004). The USDA publishes annual reports on animal usage in research; however, those numbers exclude birds, mice of the genus Mus, and rats of the genus Rattus bred for use in research, according to animal welfare act (AWA) regulations, and are therefore not included in the 1,131,076 animals reported in 2009 (US Department of Agriculture, Animal and Plant Health Inspection Service 2009).
In Europe, of the animals used 79% are mammals, with rodentia, and here mainly mice and rats, making up for 75% of total animals; another 2.6% are rabbits (Fig. 3). The main areas of use are in basic science (33%) and research and development (31%), followed by production and quality control for medical products, substances, or devices (15%).
Animal usage under the REACh legislation
How to test for CMR and long-term organ damage without animals?
We are still far away from a pure in vitro—in silico approach. However, the described methods are already used today by the pharmaceutical industry to evaluate drug candidates during research and development and thereby reduce animal use in that area. A number of in vitro methods have been accepted by the OECD or are under review for acceptance. Computational approaches have the same potential to drastically reduce animal use under the REACh legislature.
Current efforts at ZEBET
Toward international acceptance of alternative methods
OECD test methods that have been improved in respect to animal welfare under participation of ZEBET
Complete replacement of the animal experiment
Skin absorption: in vitro method
In vitro skin corrosion: transcutaneous electrical resistance (TER)
In vitro skin corrosion: human skin model test
In vitro 3T3 NRU phototoxicity test
Bovine corneal opacity and permeability test method for identifying ocular corrosives and severe irritants
Isolated chicken eye test method for identifying ocular corrosives and severe irritants
In vitro skin irritation: reconstructed human epidermis (RhE) test method
Reduction in the number of animals and stress of the laboratory animals
Acute oral toxicity—fixed dose procedure
Acute oral toxicity—acute toxic class method
Acute oral toxicity—up-and-down procedure
Skin sensitization—local lymph node assay
Acute inhalation toxicity—acute toxic class method
The following OECD guidance documents have been developed or improved from the animal welfare perspective
Detailed review document on classification systems for eye irritation/corrosion in OECD member countries
Detailed review document on classification systems for skin irritation/corrosion in OECD member countries
Guidance document on the recognition, assessment, and use of clinical signs as humane endpoints
Guidance document on acute oral toxicity testing
Guidance document for the conduct of skin absorption studies
Guidance document on the validation and international acceptance of new or updated test methods for hazard assessment
Guidance document on acute inhalation toxicity testing
Guidance Document on the validation of (quantitative) structure–activity relationship [(Q)SAR] models
Report on biostatistical performance assessment of the draft TG 436 acute toxic class testing method for acute inhalation toxicity
The experimental validation of any new or updated toxicological test method requires examining both its intra- and inter-laboratory reproducibility as well as its performance in the prediction of toxic properties to humans. The translation of test method readouts into human health predictions requires prediction models which are often based on biostatistical methods. Thus, prediction models are crucial components of test methods as they must guarantee correct predictions about new substances for the purpose of human health protection. The incorporation of the “prediction model concept” into GD 34 was a major concern of ZEBET and ECVAM (Archer et al. 1997), and probably the most important contribution to this document through a special OECD expert consultation meeting on “Data Interpretation Procedures” in 2004.
Over the years, it has been understood that competent authorities, of which ZEBET itself is a part, and stakeholders need to be involved throughout the entire validation and acceptance process. In addition to their participation in the national and later international consolidation processes (e.g., OECD, ICH, ISO), they should be involved already in earlier steps. The definition of their information needs and identification of suitable readouts and endpoints of the new method, the selection of suitable tests and test chemicals, and subsequently the peer review of the method all benefit from their involvement, and importantly help to avoid the development of tests not suitable to support regulatory decisions. In later stages, regulators should be involved in the definition of performance standards and the definition of special studies, e.g., to enlarge the applicability domain of a new test method which can also mean the extension of regulatory acceptance into new areas not yet validated.
This lesson was learned during the evaluation of the Corrositex assay for skin corrosion (Interagency Coordinating Committee on the Validation of Alternative Methods 1999). The test producer used a panel of chemicals during development that mostly covered pH values <3 or >11, substances which would be suspected as corrosive by that fact alone. Indeed, chemical categories with a majority of chemicals providing extreme pH values have been finally accepted to be the validated applicability domain of the Corrositex assay, and it is therefore now instrumental for hazard sub-categorization of corrosive chemicals and products in the context of UN regulations for transportation of dangerous goods.
Similarly, at the heart of the idea of performance standards for test guidelines was the acute problem of loss of suppliers for two human reconstituted skin models during their early validation for testing for skin corrosivity (Balls 1997). Performance standards define global criteria that a test method is expected to fulfill, independent of a specific test setup. To emphasize the importance of performance standards, we may look at the achievements in the automobile industry. When renting a car of unknown make at an airport nowadays, due to standardization, we are familiar with the instruments and are able to safely drive within a few minutes without the need of a manual and further advice. Most importantly, we can trust that in a dangerous situation, the car will behave similar to other cars; for instance, due to internationally agreed performance standards, braking distances of today’s cars are in the range of 40 m ± 7% when coming to a halt from a speed of 100 km/h. Translated into the area of new toxicological test guidelines, this means that definition of performance standards in the test guidelines will allow for so-called catch-up validation. For instance, the OECD TG 431 defines general and functional conditions that an in vitro human reconstructed (dermal or epidermal) model must meet before it can be used routinely for skin corrosion testing. In addition, the guideline requires correct prediction of twelve reference chemicals as well as assessment of intra- and inter-laboratory variability. This allows new developments or very similar assay systems to be rapidly incorporated into guidelines. For example, the SkinEthic RHE in vitro corrosion test was accepted by ECVAM little more than half a year after publication of its catch-up validation study (Kandarova et al. 2006; European Center for the Validation of Alternative Methods 2006). The more recent TG 439 comprises three elements for performance standards, essential test method components, a minimum list of twenty reference chemicals, and defined reliability and accuracy values. The latter values represent the sensitivity, specificity, and accuracy of current methods, and any new method has to perform equal or better.
ZEBET is also in the unique position to be able to perform “horizontal” method re-evaluation. A study investigating the necessity for the use of one rodent and one non-rodent animal species, usually rats and dogs, in parallel for repeated dose toxicity of pesticides revealed that treatment of dogs for longer than 90 days provides no additional information indispensable for risk assessment (Spielmann and Gerbracht 2001; Box and Spielmann 2005). This was possible since ZEBET had access to regulatory data covering 40 years of authorization of pesticides from companies supplying Germany through the competent regulatory authority (BGA and later BgVV). At ZEBET, such data, which is in most cases not published and confidential, can be analyzed anonymously.
Another example of the scientific use of proprietary data for the development of an in silico prediction tool is the development of the “decision support system” for skin irritation and corrosion. Based on the confidential EU New Chemicals Database, a set of exclusion rules derived from physicochemical properties and structural alerts derived from SAR models were developed at the BGA (and later BgVV) in cooperation with the Dutch Ministry of Health (RIVM) and the US-Environmental Protection Agency (US-EPA) for identifying chemicals that are unlikely or likely to cause skin irritation or corrosion (Gerner et al. 2004; Hulzebos et al. 2005; Walker et al. 2004, 2005). This in silico method is recommended to be used within the new EU regulation of chemicals (REACh) and is currently integrated in the OECD (Q)SAR Application Toolbox.
The use of embryonic stem cells in developmental toxicity testing
Congenital abnormalities represent perhaps the most severe side effects a chemical can have, and their prevention is an essential goal in toxicological safety assessment of chemicals and drugs. To evaluate adverse effects on reproduction and embryonic development, mandatory OECD test guidelines, or so-called segment studies, encompassing three crucial periods of pre- and postnatal development and fertility have been established (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use 2005a). These guidelines specify time-consuming and expensive in vivo experiments mostly performed on mammalian species such as rats or rabbits (Fig. 6).
One prominent drawback of the classical EST, which is shared by other in vitro assays for embryotoxicity such as the whole embryo culture test and the rat limb bud micromass test, is its reliance on a morphological endpoint. Although all of these tests systems offered 100% predicitivity for strong embryotoxicants as verified in the ECVAM validation trial, it is of great concern that they all rely on experienced laboratory personnel to produce high-quality data (Spielmann et al. 2006). In order to improve the accuracy of these assays, we and other research groups are now focused on the identification of novel molecular endpoints to be assessed by more objective and quantitative means, such as gene expression analysis based on real-time RT-PCR and flow cytometry (Seiler et al. 2004; zur Nieden et al. 2004). In a recent study, we worked out a new molecular approach based on the analysis of the expression of certain marker proteins specific for developing heart tissue (i.e., sarcomeric MHC and α-actinin) using quantitative flow cytometry analyses (Fig. 11). The molecular FACS-EST offered the same sensitivity compared to the validated EST protocol but the test duration could be significantly reduced. Due to these improvements, this new molecular method holds promise as a sensitive, more rapid and reproducible screen highly suited to predict developmental toxicity in vivo from in vitro data (Buesen et al. 2009). Recent studies on glycol ether alkoxy acid metabolites (de Jong et al. 2009) and valproic acid derivatives (Riebeling et al. 2011) nicely demonstrated that both the standard EST and the molecular FACS-EST can be reliably used as a tool to assess structure-dependent teratogenicity.
Currently, the stem cell research group at ZEBET is committed to exploring and developing additional stem cell-based approaches, searching for novel predictive biomarkers of developmental toxicity, and extending the experimental approach to other cellular systems for the prediction of developmental neuro- and osteotoxicity. Promising differentiation protocols for certain cell types most susceptible to chemical-mediated toxicity during early development like cardiac, bone, and neural cells have been successfully developed. For neural cell development, we could demonstrate that mouse embryonic stem cells can be efficiently differentiated in vitro into cell types present in the nervous system like mature neurons, astrocytes, and oligodendrocytes (Seiler et al. 2006b). On the basis of this approach, new rapid and predictive in vitro screens for developmental neurotoxicity testing have been developed. Currently, investigations are underway to explore the use of pluripotent stem cell lines derived from primate blastocysts in assessing developmental osteotoxicity. Due to the close evolutionary relationship, these cells might help to improve the predictivity for human toxicity.
Recently, new exciting avenues of research on the role of microRNA (miRNA) in toxicogenomics and the possibility of epigenetic effects on gene expression were identified. Therefore, miRNA profiling opens the possibility to discover new molecular endpoints that might contribute to a further understanding of chemical-mediated developmental toxicity. Current investigations are aimed at studying miRNA expression in differentiating mouse embryonic stem cells and their dysregulation upon exposure to embryotoxic compounds. Furthermore, in line with the report from the National Research Council on toxicity testing in the twenty-first century, which has proposed fundamentally new directions for toxicity testing in light of advances in understanding biological responses to chemical stressors (Krewski et al. 2010), new research projects at ZEBET involve the mapping of toxicity pathways in differentiating mouse and human stem cells as well as pluripotent stem cell lines and the identification of critical pathway perturbations that either correlate with or directly represent molecular initiation events for adverse effects during human embryonic development.
Implementing the 3Rs principle by funding the development of alternative methods
An increasing demand for health risk assessment due to the REACh program of the EU, as well as changes in the legislature exemplified by the 7th Amendment of the Cosmetics Directive that prohibits the use of animal experiments for the toxicological evaluation of cosmetic ingredients, has stimulated the search for novel experimental approaches that have the potential to reduce or replace animal experiments.
On the other hand, the US National Academy of Sciences published its vision of a modern toxicology in the twenty-first century in 2007 (Krewski et al. 2010). The US-EPA, the NIEHS National Toxicology Program, and the National Institutes of Health Chemical Genomics Center joined forces to follow this ambitious proposal to develop new toxicity testing strategies, with an emphasis on high throughput technologies to establish toxicological “fingerprints” or reveal toxicological pathways of chemicals, complex mixtures, and pharmaceuticals (Krewski et al. 2009, 2010; Dix et al. 2007; Andersen and Krewski 2009).
These more recent activities reflect a completely changed perception of alternative and in vitro methods as a tool for toxicological risk assessment. Following the implementation of the EU Directive 86/609 and the revision of the German animal welfare act, promoting the development of alternative methods became one of the main missions of ZEBET. Since its inception, ZEBET supports research projects throughout Germany which have the potential to provide novel and innovative experimental approaches to reduce or replace animal experiments with a unique funding program (Fig. 12).
The financial resources of ZEBET@BfR allow for the support of approximately ten projects at a time, amounting to over 100 funded research projects over the last 20 years (Fig. 12). The emphasis is given to projects that lack the experimental evidence that is necessary to seek financial support from larger funding agencies but target important regulatory needs and appear promising to contribute substantially to animal welfare. In this respect, the integration of ZEBET into the BGA first and the BfR later proved instrumental, since the close proximity to regulators facilitated the exchange of information concerning regulatory needs and thus the selection of meaningful projects at the right time.
Over a period of 2–3 years, the investigator is provided with sufficient funds to gather experimental evidence in proof-of-concept studies. For example, the establishment of recombinant Chinese hamster V79 cell lines ectopically expressing human cytochrome P450 enzymes allowing the analysis of drug metabolism and toxicity led to subsequent funding by the BMBF and EU and the successful foundation of a company (Döhmer 2001). In addition, the development of bioreactors enabled scientists to avoid the use of ascites as a source for monoclonal antibodies and are now used to simulate various organs, including the human lymph node, to evaluate the sensitization potential of chemicals or pharmaceutical substances (Giese et al. 2006). Furthermore, initial work on the development of the monocyte activation test as an alternative to pyrogen testing in rabbits was supported by the ZEBET and will be adopted by the European Pharmacopoeia (Hartung et al. 2001).
ZEBET@BfR also funded the development of various in silico methods based on structural similarities that gained increasing importance over the last years in the evaluation of potential adverse effects, but also for the analysis of in vitro data. For example, the lazy structure–activity relationships (LAZAR) program is used to predict genotoxic activities of chemicals based on structural similarities to chemicals with known in vivo toxicity data (Helma 2006). Similarly, ZEBET provided the financial support to allow the development of software required for the prediction of the phototoxic potential of chemicals based on the results obtained by the in vitro 3T3 NRU phototoxicity test (OECD TG 432), and the biometric evaluation of the Acute Toxic Class (ATC) method for acute inhalation toxicity (OECD TG 436). These projects were essential to achieve international acceptance of these methods as OECD test guidelines (Holzhütter 1997; Holzhütter et al. 2003). Further, the establishment of the so-called Registry of Cytotoxicity that is based on published data from hundreds of in vitro cytotoxicity assays provides strong evidence that the in vivo toxicity of chemicals can be predicted from in vitro data (Halle 2003). This in turn can have a significant effect on the number of animals used for in vivo toxicity testing, e.g., by facilitating the calculation of the starting dose for acute oral toxicity studies. Finally, in silico models that provide important information concerning the permeability of the human skin have been developed that correlate well with results obtained using in vitro experimental skin models (Hansen et al. 2008).
A large number of cell-based, organotypic or ex vivo approaches were supported over the years, including models for specific toxicological effects on liver, heart, lymph node, ovary, ear, central nervous system, cornea, or the skin (Fig. 9). In particular, the use of human skin models was promoted by ZEBET. As an in vitro alternative to the rabbit test for skin irritation and corrosion (OECD TG 404), this model is now accepted worldwide. In addition, these models are very useful for the prediction of skin adsorption and penetration of chemicals and pharmaceuticals (Schäfer-Korting et al. 2008).
In summary, the support by ZEBET of a broad spectrum of activities and ideas was very successful in promoting the development of in vitro systems that already reduce or replace animal experiments or bear the promise to contribute to the 3Rs concept in the near future. The success of the ZEBET@BfR funding program is also reflected by the various national and international awards received by the funded scientist for their work and contributions to the 3Rs as summarized in the brochure published by the BfR on the occasion of the 20th anniversary of ZEBET (http://www.bfr.bund.de/cd/30995).
ZEBET’s competence in searching for literature and information on alternative methods to animal experiments
Acknowledging that “man has a moral obligation to respect animals and to have due consideration for their capacity for suffering” (Council of Europe 2005), the EU has stipulated legislation to protect animals that are used for experimental and other scientific purposes (Council of Europe 2005).
As a consequence, in addition to morality, there is a legal obligation to identify and use appropriate methods to replace, reduce, or refine experimental animal use. This obligation considers the internationally accepted 3Rs concept that was laid out by Russel and Burch in 1959. Concerning replacement, an “experiment shall not be performed if another scientifically satisfactory method of obtaining the result sought, not entailing the use of an animal, is reasonable and practicably available” (Council of Europe 2005). Furthermore, as to reduction and refinement experiments which “use the minimum number of animals, involve animals with the lowest degree of neurophysiological sensitivity, cause the least pain, suffering, distress, or lasting harm” should be selected (Council of Europe 2005). Therefore, the search for relevant information about methods compliant with the 3Rs is a key issue of authorization procedures for animal experiments in Europe.
Scientists in the European countries planning to conduct animal experiments are obliged to undertake a valid “indispensability search” prior to applying for an authorization of the experiment at the national competent authority. The aim of an indispensability search is to proof the lack of the presence of (1) a suitable alternative method according to the 3Rs concept that can be applied instead, (2) usable results from comparable previous animal experiments, and (3) results from other research suited to anticipate the outcome of the planned experiment. Only when the availability of a suitable alternative or of usable scientific results have been excluded based upon the current state of knowledge, an animal experiment may be authorized.
Scientifically relevant databases like PubMed provide the opportunity to search an ever-growing number of documents simultaneously via simple and usually general keywords. After retrieving the hit list, extensive efforts are usually required for sorting out irrelevant literature. Moreover, the typical curriculum of scientists completely lacks courses in information retrieval. Most scientists may only be capable of applying ordinary searcher skills. In the field of patent affairs, where the “novelty search” has a similar significance, it is estimated that the cost of duplicate research due to irrelevant information retrieval amounts to about €20 billion a year in Europe alone (European Patent Office 2009).
In order to support the implementation of animal protection obligations in the sciences, ZEBET advises individual scientists and authorities how to obtain, evaluate, and apply information on suitable alternative methods.
ZEBET follows a three-fold strategy to improve information dissemination on alternative methods to animal experiments that consists of (1) capturing of and supply with information, (2) education in reliable search procedures, and (3) research in retrieval technology.
AnimAlt-ZEBET: all the essential information in a nutshell
In the basic sciences, the impact of a method is judged by bibliometric analyses, i.e., citation analyses and the impact factor of the publishing journal. For a more informed evaluation, it is planned to conduct expert consultations whenever a sufficient body of alternative methods addressing a defined topic in the basic sciences has been compiled. The primary objective of the consultations will be to reach consensus on the relevance and the foreseen application domains of the given methods.
Currently, the emphasis of the database is on methods in toxicity and potency testing, e.g., alternatives in skin sensitization, eye irritation, or Botulinum neurotoxin potency testing. In the future, the focus will be extended to cover alternatives in the basic sciences more comprehensively. Accordingly, the latest method portraits feature alternatives to animal models in neurodegenerative processes, such as traumatic brain injuries, and Parkinson’s and Alzheimer’s disease.
Education in reliable search procedures
Surveying the relevant literature is part of the daily business in basic science and medicine; however, courses on information retrieval are not obligatory in scientific education. In cooperation with the universities and the Regional Authority for Health and Social Matters of Berlin (LAGeSo), ZEBET@BfR contributes to training courses on “Laboratory Animals, Animal Experiments and Alternatives”. This course is certified by the German Society for Laboratory Animal Science (GV-SOLAS) and is attended by some 200–300 scientists involved in animal experimentation per year. The ZEBET part covers topics of information retrieval like structured searching, choosing the most relevant information resources, conceiving of search terms, using operators and wildcards, index-term-based searching, and semantic search engines. A main goal of the course is to instruct participants in index-term-based (classification) searching strategies (Motschall and Falck-Ytter 2005), and 3R-relevant terms.
In addition, ZEBET cooperates with ECVAM of the European Commission’s (EC) Joint Research Centre (JRC) in developing a search guide primarily to support scientists, regulators, and ethical committees involved in the planning, ethical review, authorization, and conduct of animal experiments.
Research in retrieval technology
Search engines that integrate human expert domain knowledge are a subgroup of “semantic search engines”. They aim to gather the meaning of natural language documents or phrases from the occurrence and co-occurrence of certain terms and their synonyms within the text of a document and thus assist scientists in retrieving and sorting relevant domain literature.
Advisory services for public authorities, ministries, and scientists
The Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) is responsible for consumer protection and animal welfare in Germany. ZEBET as part of the BfR, which is a higher federal authority, is directly reporting to the BMELV. Consequently, ZEBET advises the ministry’s animal welfare division on all scientific questions of animal welfare in the context of laboratory animals. For instance, ZEBET experts repeatedly advised the BMELV in conjunction with the amendment of EU Directive 86/609 which regulates the handling of laboratory animals in the EU.
Furthermore, ZEBET scientists examine on request of the competent authorities of the federal states (“Länder”) whether an animal experiment for which an application has been submitted is indispensable pursuant to the animal welfare act. For this assessment, more than 250 scientists at the BfR and also scientists at other federal institutions can be consulted in the evaluation. ZEBET scientists investigate whether the application reflects the latest scientific findings, whether alternative methods exist that can be used instead of the proposed animal experiment, whether the experimental design is statistically sound and, at the same time, whether the number of animals reduced to a minimum without compromising the objectives of the project. Additionally, scientists who develop or wish to establish new alternative methods in research institutes, universities, or industry also frequently approach ZEBET. Because of their many years of experience in the development, validation, and regulatory recognition of alternative methods, ZEBET scientists are able to judge whether a new alternative method is likely to be a suitable replacement for an internationally established animal experiment and how this goal might be achieved. ZEBET scientists are also sought as experts on the international level in research support programs for the development of alternative methods and for the judging of research prizes.
Furthermore, ZEBET scientists are very popular interview partners for the German media because of their comprehensive expert knowledge.
Regulatory challenges to be urgently addressed: The example of Botulinum neurotoxin
Currently, the serotypes BoNT-A and BoNT-B are used as active ingredients in licensed drugs for the treatment of a variety of medical disorders such as cervical dystonia, blepharospasm, spastic conditions, and hyperhidrosis. However, BoNT is also used in so-called “esthetic medicine” to temporarily treat facial asymmetries or reduce facial lines. BoNT’s pharmacological activity is extraordinarily high which, due to its biological origin, varies from batch to batch. Therefore, it is not only a question of potency but also of drug safety that the biological activity of BoNT needs to be determined as accurately as possible. The monograph “Botulinum Toxin Type A for Injection” of the European Pharmacopoeia 7.2 (Council of Europe 2011) states that every production lot of BoNT has to be tested in an LD50 potency test in mice (Fig. 16), where the final dilution series results in the highest dosing killing 90% of animals and the lowest dosing in at least 90% survival.
In the case of BoNT LD50 potency testing, the dosing of animals is associated with severe suffering. Death is generally secondary to respiratory failure due to paralysis of the respiratory muscles. Consequently, the introduction of alternative methods is urgently required. A number of alternative tests have been developed in the past decades aiming to replace the mouse bioassay. Additionally, promising methods are under development, which may alone or in combination with other assays meet the rigid requirements of potency testing.
The basis for successful validation studies for alternative bioassays is the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guideline Q2 (Validation of analytical procedures) (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use 2005b). Since the LD50 tests of the different BoNT-producing companies vary and are product specific (Mclellan et al. 1996; Sesardic et al. 2003), the specific alternative methods have to be validated for each individual medicinal product. In this context, no standard validation program can be applied, but individual validation plans have to be developed.
Ethical concerns have been raised in both Europe and the US about the animal suffering in BoNT potency testing, especially in the context of BoNT’s cosmetic applications. As a result, the BMELV commissioned ZEBET to assess the status of the different existing alternative methods to the BoNT LD50 potency test and the most promising approaches for their validation. In the following, an Expert Meeting on the “Current Scientific and Legal Status of Alternative Methods to the LD50 Test for Botulinum Neurotoxin (BoNT) Potency Testing” was held at the BfR on April 27–28, 2009 (Adler et al. 2010). Experts from industry, regulatory authorities, German ministries, academia, national and international validation centers, and animal welfare organizations were invited to actively participate in the meeting.
During the meeting it became clear that guidance on product-specific validation of alternative methods to the LD50 potency test needs to be given by the regulatory authorities in close communication with the manufacturers before and during the validation process. To facilitate validation efforts, international harmonization and mutual acceptance criteria of regulatory authorities are necessary. Importantly, funding should be made available and coordinated to develop and validate alternative assays for BoNT potency testing according to the 3Rs principles. Especially the development of a replacement alternative for BoNT testing should have priority.
At the expert meeting, researchers and industry could demonstrate some progress in implementing reduction and refinement in BoNT potency testing, and in the development of alternative potency assays. Still, the majority of participants expressed the wish that a “BoNT Expert Working Group” (BoNT EWG) should be established in order to provide advice and guidance on validation requirements for proposed alternative methods and to define minimum standards in order to implement the 3Rs in BoNT potency testing. Furthermore, the BoNT EWG should promote awareness and transparency between the stakeholders and regulatory authorities. By request of the participants of the meeting, ZEBET@BfR in collaboration with the Federal Institute for Drugs and Medical Devices (BfArM) accepted to function as chairs and coordinators of this working group.
The BoNT EWG comprises experts from European regulatory authorities, 3R-related and validation institutions, manufacturers, and scientists. Additionally, experts from overseas are invited as observers. It will meet regularly several times per year during a proposed time frame of 4 years. The BoNT EWG has been formally established and their statutes phrased and adopted in three meetings so far. However, the outcomes of the meetings remain confidential unless otherwise expressly agreed by all members.
Current and future activities of ZEBET@BfR
Current experimental activity at ZEBET
Inhalation toxicity testing in vitro (CULTEX)
Go3R semantic search engine
Metabolic capacity of skin tissue models
Embryotoxicity assays and metabolically competent systems
In vitro developmental cardiotoxicity
In vitro developmental neurotoxicity
In vitro developmental osteotoxicity
Increased research efforts regarding chronic toxicity endpoints
Boosting collaborations, national and international networking
Intensifying efforts at the OECD
Severity classification of procedures on animals
Establishment of a Refinement Center at ZEBET@BfR
Establishment of a National Reference Center for Alternatives to Animal Testing
: The 3Rs in the field of transgenic animals
Implementation and enforcement of the 3Rs principle in the field of transgenic animals
Best practice conditions and animal welfare standards
Defined pure genetic backgrounds
Shared and cryo-archived models
Standardized characterization in Mouse Clinics
Phenotyping results in databases
Standardizing and connecting European databases
Phenotyping of existing models
Mouse line generation by most competent staff
Improved ethical review and biostatistics
Reduced distress in identification/genotyping methods
Indication of 3R relevant technical information in publications
However, building on our strengths, such as boosting collaborations and networking in the national as well as the international arena, and intensifying our efforts at the OECD level, will remain a central future aim. Also, the existing expertise in in vitro methodologies as alternatives to animal testing needs to be fairly expanded, and research efforts especially regarding chronic toxicity endpoints increased. By noting this, it becomes clear that without any doubt ZEBET’s main tasks and focus currently lie and will remain to lie in the replacement and reduction of animal testing. In particular with regard to chronic toxicity endpoints, such research efforts are still ill funded and scattered throughout Germany and to increase exchange and collaboration a National Reference Center for Alternatives to Animal Testing should be established which could be hosted at ZEBET@BfR.
The authors are grateful to all of the contributors and attendees of the 20th anniversary of ZEBET celebrated at BfR, Berlin, in October 2009.
Conflict of interest
The authors declare that there are no conflicts of interest.
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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