Back to Posts

Back to Posts

May 10, 2022 Agency Alerts

Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies


On May 5, 2022, the FDA announced the availability of a draft guidance for industry entitled Clinical Pharmacology Considerations for Human Radiolabeled Mass Balance Studies. This draft guidance describes the FDA’s recommendations regarding clinical pharmacology considerations for conducting human radiolabeled mass balance studies of investigational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 Please refer to the draft guidance for more details. FDA is publishing this draft guidance to collect additional public comments. You may submit your comments regarding the draft guidance to the docket (FDA-2022-D-0113) available at https://www.regulations.gov up to 90 days following publication in the FEDERAL REGISTER. This draft guidance, when finalized, will represent the current thinking of the FDA on this topic.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.

Download the Draft Guidance Document

Interested in learning more? Contact us today to find out how we can help not only with your EMA/FDA submissions, but all of your global regulatory needs.



Your Business has Complex Challenges. ProPharma Group has Exceptional Solutions.

We partner with pharmaceutical, biotechnology, and medical device clients to tackle complex challenges. Contact us to learn how our experienced team can help ensure regulatory and development success throughout the product lifecycle.

Interested in gaining an industry edge? Let us help you stay up to date.


All fields are required.
There was a problem with your submission. Errors have been highlighted below.