Background: Microdosing is a technique for studying the behavior of compounds in vivo at 1/100th of the dose of a test substance calculated, based on animal data, to yield a pharmacologic effect. In microdosing, use is made of accelerator MS (AMS). In this study, we investigated whether 129I-labeling of proteins with subsequent AMS measurements is a suitable method to perform microdose studies with therapeutic proteins. We used erythropoietin (EPO) as a case study.
Results: In an animal study with 129I-labeled EPO in Han-Wistar rats, an increase of 129I-EPO is observed after dose administration. The half-life was found to be 2 and 5.5 h for two different EPOs. These results are in accordance with expected values.
Conclusion: Although further research is required, 129I-labeling of proteins seems a feasible method for AMS microdose studies with peptide and protein drugs, such as biosimilars.