Clinical and anatomic pathology effects of serial blood sampling in rat toxicology studies, using conventional or microsampling methods.

UNLABELLED: As a general practice in rodent toxicology studies, satellite animals are used for toxicokinetic determinations, because of the potential impact of serial blood sampling on toxicological endpoints. Besides toxicological and toxicokinetic determinations, blood samples obtained longitudinally from a same animal may be used for the assessment of additional parameters (e.g., metabolism, pharmacodynamics, safety biomarkers) to maximize information that can be deduced from rodents. We investigated whether removal of up to 6 × 200 µL of blood over 24h can be applied in GLP rat toxicology studies without affecting the scientific outcome. METHODS: 8 week-old female rats (200-300 g) were dosed for up to 1 month with a standard vehicle and subjected or not (controls) to serial blood sampling for sham toxicokinetic/ancillary determinations, using miniaturized methods allowing collection of 6 × 50, 100 or 200 µL over 24h. In-life endpoints, clinical pathology parameters and histopathology of organs sensitive to blood volume reduction were evaluated at several time points after completion of sampling. RESULTS: In sampled rats, minimal and reversible changes in red blood cell mass (maximally 15%) and subtle variations in liver enzymes, fibrinogen and neutrophils were not associated with any organ/tissue macroscopic or microscopic correlate. CONCLUSION: Serial blood sampling (up to 6 × 200 µL over 24h) is compatible with the assessment of standard toxicity endpoints in adult rats.

Miniaturized blood sampling techniques to benefit reduction in mice and refinement in nonhuman primates: applications to bioanalysis in toxicity studies with antibody-drug conjugates.

Minimizing the number of animals in regulatory toxicity studies while achieving study objectives to support the development of future medicines contributes to good scientific and ethical practices. Recent advances in technology have enabled the development of miniaturized blood sampling methods (including microsampling and dried blood spots) applicable to toxicokinetic determinations of small-molecule drugs. Implementation of miniaturized blood sampling methods in the context of biotherapeutic drugs is desirable because a limitation to this type of medicine remains the total blood volume needed from a single animal to support toxicokinetic determinations of several analytes (parent drug, metabolites[s], antidrug antibodies, and so forth). We describe here the technical details, applicability, and relevance of new miniaturized blood sampling procedures in mice and nonhuman primates in the context of the toxicologic evaluation of biotherapeutic drugs consisting of antibody-drug conjugates developed for oncology indications. These examples illustrate how these techniques can benefit the reduction of animal usage in mouse toxicity studies by decreasing the number of animals dedicated to toxicokinetic determinations and the refinement of practices in nonhuman primate toxicity studies by decreasing the blood volume repeatedly drawn for toxicokinetic determinations.