Efficacy Estimand
A trial statistic answering 'what if everyone took the drug as directed' — the reason one trial reports two averages.
Modern trials report results under different "estimands" — precise framings of the question. The efficacy (or trial-product) estimand asks what the drug achieves when taken as intended; the treatment-regimen estimand includes everyone randomized, dropouts and dose reductions included, approximating real-world average experience.
That's why SURMOUNT-1 is honestly citable as both 22.5% and 20.9% at 15 mg — same trial, different question. Marketing predictably favors the larger number; careful pages label which they're using (ours do). The patient translation: the efficacy estimand is your ceiling with full adherence, the treatment-regimen figure is closer to the average of everyone who starts.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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