> ## Content Index
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> Use this file to discover other available public pages before exploring further.

# Comments on Radiolabeled Studies Draft
- URL: https://www.fdaweb.com/comments-on-radiolabeled-studies-draft/
- Published: 2022-08-10T12:00:00.000Z
- Updated: 2026-09-14T17:55:21.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5152482

Janssen says an FDA draft guidance on clinical pharmacology considerations for human radiolabeled mass balance studies is well written and provides sponsors with much-needed guidance when conducting mass balance studies. The firm’s [comment](https://www.regulations.gov/comment/FDA-2022-D-0113-0011?ref=fdaweb.com) also has specific suggestions for strengthening the draft.

AbbVie [says](https://www.regulations.gov/comment/FDA-2022-D-0113-0013?ref=fdaweb.com) recent microtracer approaches using accelerator mass spectrometry should be addressed in the guidance. It includes other line-by-line comments.

Takeda [asks](https://www.regulations.gov/comment/FDA-2022-D-0113-0018?ref=fdaweb.com) for some clarifications and gives specific line-by-line comments.

AstraZeneca [provides](https://www.regulations.gov/comment/FDA-2022-D-0113-0016?ref=fdaweb.com) general comments on definition of terminology and number of evaluable subjects and line-by-line comments.

Finally, Pfizer [gives](https://www.regulations.gov/comment/FDA-2022-D-0113-0011?ref=fdaweb.com) line-by-line specific comments.