Oncology Therapeutic Radiopharmaceuticals: Dosage Optimization During Clinical Development

FDA Draft Guidance Sets New Standards for Radiopharmaceutical Dosing in Oncology Trials

Oncology radiopharmaceuticals are advancing rapidly, but until now, sponsors have been navigating a dosing landscape built for external beam radiation. That’s changing. In August 2025, the FDA released a draft guidance on Oncology Therapeutic Radiopharmaceuticals: Dosage Optimization During Clinical Development—a move that could reshape how sponsors design and execute clinical trials.

Why This Matters

Unlike external beam radiation, radiopharmaceutical therapies deliver radiation systemically, often with delayed and cumulative effects. Traditional dose-finding models based on “maximum tolerated dose” simply don’t fit. This guidance acknowledges that reality, and sets a higher bar for trial design, patient safety, and regulatory alignment.

Key Takeaways for Sponsors

• Beyond EBRT Limits: Dosing above external beam thresholds may be acceptable if scientifically justified and should be discussed early with FDA.
• Safety First: Sponsors are expected to include long-term follow-up (≥5 years), with particular focus on renal and marrow toxicities.
• Dosimetry Is Essential: Personalized dosimetry should be integrated early to correlate absorbed radiation dose with outcomes.
• Smarter Trial Design: Randomized, dose-response cohorts and clearly defined cycle counts will be expected.

What Sponsors Should Do Now

• Reassess current trial protocols against the draft recommendations.
• Engage dosimetry experts early to ensure data collection aligns with FDA expectations.
• Prepare to submit comments by October 2025—this is a chance to shape the final guidance.

Bracken’s Perspective

This draft guidance is more than regulatory housekeeping: it signals a paradigm shift. Teams that proactively embed dosimetry, flexible dosing schedules, and robust long-term monitoring will not only be compliant, but competitive. At Bracken, our radiopharmaceutical experts help sponsors translate evolving FDA expectations into practical, patient-centered trial strategies.

Call to Action

Is your trial design aligned with the FDA’s new vision for radiopharmaceutical dosing? Contact Bracken today to start building a strategy that’s both compliant and competitive.