Linda Allais

A global pharmaceutical company initiative: An evidence-based approach to define the upper limit of body weight loss in short term toxicity studies

Short term toxicity studies are conducted in animals to provide information on major adverse effects typically at the maximum tolerated dose (MTD). Such studies are important from a scientific and ethical perspective as they are used to make decisions on progression of potential candidate drugs, and to set dose levels for subsequent regulatory studies. The MTD is usually determined by parameters such as clinical signs, reductions in body weight and food consumption. However, these assessments are often subjective and there are no published criteria to guide the selection of an appropriate MTD. Even where an objective measurement exists, such as body weight loss (BWL), there is no agreement on what level constitutes an MTD. A global initiative including 15 companies, led by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), has shared data on BWL in toxicity studies to assess the impact on the animal and the study outcome. Information on 151 studies has been used to develop an alert/warning system for BWL in short term toxicity studies. The data analysis supports BWL limits for short term dosing (up to 7days) of 10% for rat and dog and 6% for non-human primates (NHPs).

Juvenile toxicity of cyclosporin in the rat

The pups from 32 litters of SD rats were given 0, 1, 3 or 10mg/kg-d of cyclosporin by oral gavage from 4 to 28 days of age. 10mg/kg-d resulted in a persistent impairment of the primary antibody response at 10 weeks of age. Indications of systemic toxicity, including the death of 10/64 pups and severely depressed weight gain, were also observed at this dose level. Arteriopathy of the heart and tubular basophilia and edema in the cortico-medullary region of the kidney were observed at 3 and 10mg/kg-d. In conclusion, while pharmacological effects were seen at all dose levels, the adverse effects of cyclosporin on the development of the immune system in the rat only occurred at a dose level that also induced systemic toxicity.

Developmental Toxicity Testing of Vaccines

Preventative and therapeutic vaccines are increasingly used during pregnancy and present special considerations for developmental toxicity testing. The various components of the vaccine formulation (i.e., protein or polysaccharide antigen, adjuvants, and excipients) need to be assessed for direct effects on the developing conceptus. In addition, possible adverse influences of the induced antibodies on fetal and/or postnatal development need to be evaluated. A guidance document on the preclinical testing of preventative and therapeutic vaccines for developmental toxicity was issued by the FDA in 2006. Preclinical studies are designed to assess possible influences of vaccines on pre- and postnatal development. The choice of model animal for these experiments is influenced by species differences in the timing and extent of the transfer of the induced maternal antibodies to the fetus. The cross-placental transport of maternal immunoglobulins generally only occurs in late gestation and tends to be greater in humans and monkeys than in non-primate species. For many vaccines, the rabbit shows a greater rate of prenatal transfer of the induced antibodies than rodents. For biotechnology-derived vaccines that are not immunogenic in lower species, nonhuman primates may be the only appropriate models. It may be advisable to test new adjuvants using the ICH study designs for conventional pharmaceuticals in addition to the developmental toxicity study with the final vaccine formulation.

Nonclinical evaluation of immunological safety in Göttingen Minipigs: The CONFIRM initiative

ABSTRACT There is a growing need to consider non‐rodent species for the immunological safety evaluation of drug candidates. The EU Framework‐6 RETHINK Project demonstrated that the Göttingen Minipig is a relevant animal model for regulatory toxicology studies. Extensive knowledge on the immune system of domestic pigs is available and fewer differences from humans have been identified as compared to other species, such as mice or non‐human primates. Minipig data are too scarce to allow for claiming full immunological comparability with domestic pigs. Another gap limiting minipig use for immunological safety evaluation is the lack of a qualified and validated database. However, available data lend support to the use of minipigs. The need for a COllaborative Network For Immunological safety Research in Minipigs (the CONFIRM Initiative) was obvious. It is intended to trigger immunological safety research in Göttingen Minipigs, to assist and synergize fundamental, translational and regulatory investigative efforts relevant to the immunological safety evaluation of pharmaceuticals and biologics, and to spread current knowledge and new findings to the scientific and regulatory toxicology community. HighlightsThe Göttingen minipig is a relevant animal model for regulatory toxicology studies.The immune system of pigs is close to that of humans.The Göttingen minipig might prove to be an alternative non‐rodent species for immunological safety evaluation.The CONFIRM Initiative is a collaborative network intended to trigger immunological safety research in Göttingen Minipigs.