Preclinical safety assessment studies require the evaluation of toxicity in relation to exposure, and several collection time points may be required to provide adequate data points to perform a comprehensive assessment of the exposure and toxicokinetic (TK) profile. To avoid an impact on hemostasis, the blood volume from each draw is limited. As a result, studies must often include the use of satellite animals to accurately determine TK profiles. Recent advances in the sensitivity of bioanalytical techniques allow for the use of smaller sample volumes called microsamples, generally defined as a volume of up to 50 µL, although volumes of up to 100 µL can be collected.
The use of microsampling in toxicology studies facilitates two of the 3Rs: reduction and refinement. By collecting TK samples from the main population of animals and removing the need for a satellite group, the overall number of animals required for a study is significantly reduced. The microsampling collection techniques are less invasive; consequently, animals are less stressed, and their welfare is enhanced.
Microsampling also offers superior translational data within rodent studies. The ability to relate toxicity directly to exposure in a single animal and to obtain a full TK profile from that animal (instead of using a more traditional inter-animal approach) allows for a more accurate understanding of the toxicokinetics. By collecting comparable blood volumes at the same time points from all animals, we can achieve a better comparison within and across groups. We can also increase the amount of data collected per animal, allowing us to evaluate more parameters in a single animal.
Beyond rodent testing, the advantages of microsampling are also seen in studies involving larger species. Increasingly complex study designs and assessment of drugs that are pharmacologically active in the animal model often require the evaluation of many parameters/endpoints. Microsampling can be used not only for drug quantitation but also for the analysis of various biomarkers and T-dependent antigen response (TDAR) assays.
Overall, the use of microsampling can significantly optimize toxicology study designs, reducing costs and shortening timelines while increasing efficiencies.