Insight

Aug 21, 2025, 13:21

Harpreet Singh: FDA’s New Draft Guidance on Radiopharmaceutical Dosing Is Here

Harpreet Singh, Chief Medical Officer at Precision For Medicine, shared a post on LinkedIn:

“FDA has just released draft guidance on dosage optimization for oncology therapeutic radiopharmaceuticals. The guidance aims to help sponsors identify an optimized dose and schedule for radiopharmaceuticals that maximize therapeutic effect while minimizing toxicity before marketing applications.

Radiopharmaceuticals combine features of drugs and radiation therapy, making dosing uniquely complex. Traditional approaches, like relying on external beam radiation organ limits or short DLT windows, don’t fully capture the delayed, cumulative toxicities or heterogeneous tissue effects these therapies present.

FDA’s draft guidance document highlights three critical areas:

Trial Design: FDA recommends sponsors use fixed cycles, set cumulative activity limits, and consider randomized dose–response trials, which are particularly important when evaluating doses that exceed external beam radiotherapy (EBRT) organ tolerances or correspond to the maximum tolerated dose (MTD).
Safety Monitoring: Long-term follow-up (at least 5 years, or until death) is recommended, with close tracking of delayed radiation toxicities and incorporation of prior exposures into analyses.
Dosimetry: Phase 1 trials must include dosimetry studies, ideally with direct imaging of the therapeutic agent, along with detailed reporting and consideration of microdosimetry for alpha emitters.

What does this mean for sponsors? With this latest industry guidance, FDA is signaling a higher bar for evidence, emphasizing long-term safety, rigorous trial design, and robust dosimetry. For developers, this means engaging with regulators earlier and moving beyond maximum tolerated dose strategies to truly optimize dosing.

The draft guidance is open for public comment until October 20, 2025. Information on where to download the full guidance and how to submit comments are linked below.”

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