Implications of the Draft FDA Bayesian Guidance

2026
bayes
design
drug-development
drug-evaluation
inference
multiplicity
p-value
posterior
RCT
sample-size
sequential
The draft guidance for the use of Bayesian methodology in drug and biologics development was a long time coming but its arrival is celebrated. It offers opportunities for providing evidence measures that are more actionable and states that Bayesian methods are applicable in any context, not just specialized ones such as adaptive clinical trials or when borrowing information in rare diseases. It also puts forward pure Bayesian operating characteristics for the first time at FDA, and sets the stage for recasting multiplicity as a problem caused by assertions that are too easy to be true in any paradigm, rather than a problem to be addressed on the back-end through the use of arbitrary adjustments on the randomness scale.
Author

Frank Harrell

Published

May 21, 2026