Efficacy
The ability of a drug to produce a desired therapeutic effect under controlled clinical trial conditions. Efficacy indicates whether a drug works when properly administered. Tirzepatide demonstrated up to 22.5% mean weight loss in pivotal trials, establishing a new efficacy benchmark for metabolic peptide drugs.
Technical Context
Efficacy assessment requires controlled conditions to isolate the drug's effect from confounders, placebo effect, and regression to the mean. Key efficacy metrics vary by indication: diabetes (HbA1c change, fasting glucose, time in range), obesity (% weight loss, proportion achieving ≥5/10/15/20% loss), cancer (overall survival, progression-free survival, response rate), osteoporosis (fracture incidence, BMD change), and hormonal conditions (hormone levels, symptom scores). The treatment policy estimand (ITT) reflects efficacy as prescribed (including dropouts), while the trial product estimand (completers) reflects efficacy with adherence. The difference between these estimates quantifies the impact of non-adherence. Tirzepatide 15mg achieved up to 22.5% mean weight loss (ITT, treatment policy) and 26.6% (completers), demonstrating both high efficacy and the importance of estimand specification.