Heterogeneity of Clinical Trials for Antihypertensive Drugs in Japan: Exploratory Analysis of Confirmatory Phase III Trials Used for Marketing Approval.

The results of pivotal trials, which provide a rationale for marketing approval decisions for new drugs, are considered for various comparative purposes in postmarketing analyses. Using meta-regression analysis of 91 randomized controlled trials of 61 approved antihypertensive drugs in Japan, we show that mean baseline blood pressure (BP) of each arm was associated with predetermined entry criteria (EC), age, and trial start year (TSY). BP changes following treatment were associated with EC, subject characteristics (e.g., age, complications, baseline BP), study design (e.g., concomitant drug use), and TSY. Effect sizes were generally larger in trials for the first and second drugs in the same class than in trials for follow-on drugs. Results of pivotal trials may vary depending on many factors, suggesting possible challenges associated with the comparison of these results indirectly. Due to the heterogeneity in pivotal trials, caution should be exercised when comparing approved drugs and conducting meta-analyses retrospectively.