FDA News: Issue 10, May 2022

Author: [AUTHOR] Published on 5/10/2022 9:00:00 AM

US Food and Drug Administration Announces Availability of a Draft Guidance, Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies


On May 5, 2022, the US Food and Drug Administration (FDA) announced the availability of a draft guidance for industry entitled Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies. This draft guidance describes the FDA’s recommendations regarding clinical pharmacology considerations for conducting human radiolabeled mass balance studies of investigational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 the single most direct method to obtain quantitative and comprehensive information on the absorption, distribution, metabolism, and excretion of the drug in the human body. The mass balance study can provide information to determine the overall pathways of metabolism and excretion of an investigational drug, identify circulating metabolites, and determine the abundance of metabolites relative to the parent or total drug-related exposure. Furthermore, results from mass balance studies provide information on which metabolites should be structurally characterized or should undergo nonclinical safety assessment or drug-drug interaction (DDI) evaluation. Data from such studies can also help determine whether renal or hepatic impairment studies or certain DDI studies are recommended for the investigational drug.


The “Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies” guidance is available at: https://go.usa.gov/xupUp. Please refer to the draft guidance for more details. FDA is publishing this draft guidance to collect additional public comments. You may submit your comments regarding the draft guidance to the docket (FDA-2022-D-0113) available at https://www.regulations.gov up to 90 days following publication in the FEDERAL REGISTER. This draft guidance, when finalized, will represent the current thinking of the FDA on this topic. It does not establish any rights for any person and is not binding on FDA or the public. Your comments do make a difference and can impact the outcomes of FDA regulatory policy. Share your knowledge and experience and make your voice count.


The Office of Clinical Pharmacology (OCP) is pleased to offer the e-mail subscription service Clinical Pharmacology Corner. This is a free service from FDA to provide occasional updates from OCP regarding newly approved therapies, new regulatory and scholarly publications, upcoming events and other items of interest. Subscribe today at https://public.govdelivery.com/accounts/USFDA/subscriber/topics and select Clinical Pharmacology Corner under Drugs.

We always welcome your thoughts regarding the format, content, and utility of this communication. Comments may be sent via email to ocp@fda.hhs.gov.

This communication was prepared by Office of Clinical Pharmacology, Office of Translational Sciences, CDER, FDA.

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