Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies July 2024

https://www.fda.gov/regulatory-information/search-fda-guidance-documents/clinical-pharmacology-considerations-human-radiolabeled-mass-balance-studies?utm_medium=email&utm_source=govdelivery On July 18, 2024, the FDA announced the availability of a final guidance for industry entitled Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies, replacing the May 2022 draft guidance on this topic. This final guidance describes the FDA’s recommendations regarding clinical pharmacology considerations for conducting human radiolabeled mass balance studies of investigational drugs, including: (1) deciding whether and when to conduct the study, (2) designing the study, and (3) reporting results. A human radiolabeled mass balance study is a direct method to obtain quantitative information on the absorption, distribution, metabolism, and excretion of the drug in the human body. Data from such studies can help to: Provide information on which metabolites should be structurally characterized and which metabolites should undergo nonclinical safety assessment or drug-drug interaction (DDI) evaluation Assess whether renal or hepatic impairment studies or certain DDI studies are recommended for the investigational drug Assess the extent of absorption of the investigational drug