Animal-Health Pharmaceuticals: Research Responsibilities and Efforts in Target Animal Safety and Laboratory Animal Welfare

Abstract

As researchers in animal health, we are charged with numerous responsibilities. Among the greatest of these are ensuring the safety and effectiveness of the products we develop and the appropriate use of animals in our research efforts. The following discussion focuses primarily on the demonstration of drug safety in the species for which the product is to be licensed or registered (target animal safety) in the USA, and on our role as stewards of animal welfare in laboratory research.

Keywords::

• Center for Veterinary Medicine
• drug sponsor
• guideline 43
• investigational veterinary pharmaceutical products
• maximum potential exposure dose
• target animal safety
• target animal species

Target animal safety

Our work is guided by both industry and government standards, some of which have existed for almost 200 years (the US Pharmacopeia was first established in 1820) [101,102]. Ideally, drug research and development, together with the regulations and guidances by which we are directed, are continually improving. Sadly, change is often prompted by tragedies such as those experienced with elixir of sulfanilamide and thalidomide (resulting in the US Federal Food, Drug and Cosmetic Act of 1938 and the Kefauver–Harris Drug Amendments of 1962, respectively) [102,103]. Experiences like these are painful stimuli for the advancement of regulatory standards. We must constantly re-evaluate our methods to ensure we are providing the most thorough and appropriate demonstration of safety for our products. However, unreasonable or impractical requirements will stifle innovation and prevent beneficial drugs from reaching the public. Therefore, we must strive for well-studied, sustainable standards in target animal safety (TAS) testing.

Today, government regulations require that investigational veterinary pharmaceutical products (IVPP) be demonstrated safe in the target animal species prior to registration through both laboratory testing and field studies. In the USA, the development path for the TAS component of a new animal drug application includes close communications with the US FDA Center for Veterinary Medicine (CVM). Similar discussions with an appropriate cohort of regulators outside of the USA are recommended early in the development process for global or international projects. Recent efforts to harmonize the requirements set forth by the USA, EU and Japan were realized in the finalization of International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products Guideline 43 (VICH GL43) released in the spring of 2009 [1]. This standardization of TAS study recommendations aids in preventing the duplication of studies for each international region, allowing a more conservative use of research animals and lower development costs while promoting study designs that conform to animal welfare regulations.

The cornerstone of the TAS component of drug development is the margin of safety (MOS) study. This study is designed to evaluate the effect of the IVPP at the maximum potential exposure dose, as well as at exaggerated doses for extended durations. For example, if the maximum dose that the target species may be exposed to (based on label recommendations, weight bands and formulation characteristics [e.g., liquid suspension or scored tablet]) is 1 mg/kg and the duration for administration is 5 days, it will be tested as follows: 1, 3 and 5 mg/kg (one-, three- and five-times the maximum potential exposure dose) for a total of 15 days (three-times duration) compared with an untreated control group. Drugs to be administered for extended durations (e.g., medications for chronic disease such as hypothyroidism or osteoarthritis) are generally administered for a 6-month period or longer in the MOS study. It is important to note that the sponsor must justify the selected dose and treatment levels and the general study design based on existing data (e.g., pharmacokinetics, pharmacodynamics and toxicology [see later discussion of characterization of the toxic syndrome]), proposed use in the target species and any unique characteristics of the IVPP (e.g., inhalant anesthetic or hormone). Each treatment group is usually comprised of four healthy animals per gender with a narrow demographic scope (typically beagles and domestic shorthair breeds for canine and feline products, respectively). Although the ability of the MOS study to truly determine safety in the general population is somewhat limited by biological variation within and among individuals and groups and an inherently restricted evaluation in a small, relatively homogeneous collection of animals, the exaggerated dosing schemes incorporated in our MOS studies facilitate extrapolation of safety from the laboratory setting to the field.

Variables measured include general health, physical examinations, clinical observations, food consumption, body weight, clinical pathology and gross/microscopic histopathology. The extent of testing (e.g., frequency, specific systemic evaluations or laboratory tests) is again based on existing data and the intended use of the product. Studies may incorporate specialized procedures to evaluate the IVPP’s effects on a specific organ system or in a known sensitive population. Examples include the use of electrocardiograms where the potential for cardiotoxicity exists and testing in avermectin-sensitive collies for IVPPs that may adversely impact dogs with the ABCB1 mutant/mutant genotype. Additionally, serum may be collected during the in-life phase of the MOS study to evaluate the pharmacokinetics of the IVPP. These data may help further define the dose–exposure–response relationship. MOS studies typically require sacrifice of the study animals at the end of the in-life phase for gross and microscopic evaluation of tissues. This is considered necessary for two reasons: potentially negative systemic effects of the IVPP may not manifest themselves clinically or in the variables measured during the in-life phase of the study, requiring post-mortem gross and microscopic examination for detection; alternatively, gross and microscopic evaluation of tissues helps elucidate the pathology of adverse or abnormal findings that are observed during the in-life phase. Individual and group data are reviewed against pretreatment and control values and further assessed using statistical analyses. Due to the small number of animals included in TAS studies, the lack of a significant difference between groups does not necessarily indicate the absence of a safety issue. Therefore, evaluation of possible treatment-related effects is not limited to values outside of control or normal reference ranges, or to statistically significant tests, but includes careful attention to potential trends (e.g., persistent increases in a single hematology value or increases in a group of enzymes associated with damage to a particular organ system) and an evaluation of all findings together from a ‘big-picture’ perspective.

The effects of the IVPP as specifically related to the method of application (e.g., injectable, dermal or mammary gland safety) may be evaluated as incorporated into the MOS study design or as separate studies where the pivotal MOS study has already been completed. Additionally, reproductive safety studies may be necessary where appropriate per proposed product use. Although these are generally not terminal studies, they require additional use of research animals. Formerly, the dose–tolerance study was used to establish the toxic syndrome via administration of ten times the maximum potential exposure dose of the IVPP (given for the proposed label duration). In place of the dose–tolerance study, the CVM now requires characterization of the toxic syndrome based on study summaries, literature reviews and/or foreign market experience. This formal, written evaluation encompasses all available data, including those from uses in other species or via different formulations or methods of application, providing a robust analysis of potential toxic effects while substantially decreasing animal use and conserving resources. Finally, data from field studies allow evaluation of the IVPP under conditions of use where a larger, more diverse population of animals is sampled, including those clinically affected by the disease state the drug is intended to treat (compared with the ‘healthy’ populations evaluated in laboratory safety studies).

Study reports, raw data and other relevant information are compiled and submitted to the appropriate regulatory bodies for review. For US animal health pharmaceutical projects, this is the CVM. A submission that satisfactorily demonstrates product safety may be granted regulatory approval for release in the market. Drug-safety monitoring continues after release through pharmacovigilance activities, including regular evaluations of adverse events seen in the general population and periodic safety update reports to the regulatory agencies, ensuring that any potential safety issues are identified and addressed in a timely manner.

The release of a drug onto the market that causes unnecessary and avoidable harm is the substance of nightmares for researchers, and a situation we work very hard to prevent. As individuals, sponsors and regulators, we are deeply committed to ensuring the safety of our products.

Animal welfare

Every TAS study conducted involves research animals; this fact is not taken lightly. From both scientific and ethical viewpoints, the humane treatment of research animals is vital. From a scientific perspective, humane treatment decreases the potential for artifacts in study data, preventing physiologic changes due to stress or substandard care. Quality data come from healthy, well-cared for subjects. From an ethical perspective, the fundamental goal of scientists who perform TAS studies is to improve the health and quality of life of animals through the development of new or improved therapies. Our responsibility to ensure the welfare of our research subjects works in tandem with this goal, not in opposition to it. From housing to handling, it is in the best interests of the sponsor and scientist to positively influence the environment of their research subjects.

Government regulation of animal care and use dates back to Britain’s Cruelty to Animals Act of 1876 [2,3,104]. This was the first national law governing animal experimentation. In the USA, federal regulation was preceded by state laws until the passage of the Laboratory Animal Welfare Act in 1966 (referred to as the Animal Welfare Act [AWA] since its initial amendment in 1970) [4,105–107]. Similar to guidance for TAS testing, animal welfare regulations have been continually updated, broadening in scope and depth. The regulations of the AWA are enforced by the Animal and Plant Health Inspection Service (APHIS) branch of the US Department of Agriculture. Further guidance is provided by the Office of Laboratory Animal Welfare Public Health Service Policy on Humane Care and Use of Laboratory Animals [108]. At the individual laboratory level, AWA and Office of Laboratory Animal Welfare standards are supported by Institutional Animal Care and Use Committees (IACUC) and membership with the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC), together with the Guide for the Care and Use of Laboratory Animals National Research Council (NRC) 2011 [109], the Guide for the Care and Use of Agricultural Animals in Research and Teaching (Ag Guide), Federation of Animal Science Societies (FASS) 2010 [110], and the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes, Council of Europe (ETS 123) [111]. Laboratories are regularly evaluated via site visits, inspections and reviews conducted by APHIS, the laboratory’s IACUC and representatives of the AAALAC.

At the level of the individual study, protocols are inherently designed to incorporate the three Rs of replacement, reduction and refinement [5,112,113]. While there is currently no acceptable alternative to animal testing (both from scientific and regulatory perspectives), the experimental method of the MOS study and the standardization of regulatory requirements help ensure that appropriate data are gathered through the use of the smallest number of animals possible. Studies are carefully designed to gather the most information by the most humane methods. Protocols are reviewed and approved by the laboratory’s IACUC prior to finalization providing another level of assessment for appropriate and humane use. Unnecessary studies and procedures are avoided, with both ethical and scientific ends in mind.

Conclusion

The development of new animal drugs is critical to our ability to prevent and fight disease and promote quality of life for the greater animal population. For the individual scientist and the sponsor, the establishment of product safety and the responsible use of research animals are integral components of the development process as guided by industry and regulatory standards. TAS and animal welfare will continue to be critical topics in drug development, setting the stage for continuous improvements in study design, regulatory oversight and animal care and use.

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Additional information

Funding

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.