Comprehensive safety evaluation of new drugs for diabetes mellitus is needed in the area of cardiovascular (CV) outcomes, particularly in populations with high CV risk. Alogliptin, a dipeptidyl peptidase 4 inhibitor, is under development for the treatment of type 2 diabetes mellitus alone or in combination with other antidiabetic therapies. Long-term CV safety of alogliptin is being established in a randomized, placebo-controlled clinical study in patients with acute coronary syndrome (ACS) using an analytical approach that has both an interim and final assessment. The primary CV end point for this trial is a composite of CV death, nonfatal myocardial infarction, and nonfatal stroke. Approximately 5,400 men and women with type 2 diabetes and ACS (acute myocardial infarction or unstable angina) are being recruited and will be followed up for up to 4.5 years postrandomization. The statistical plan for the trial uses a design that evaluates the hazard ratio (HR) of alogliptin to placebo first based on the primary CV composite end point after accrual of 80 to 150 primary CV events and again when there are 550 to 650 primary CV events. In the first series of analyses, the upper bound of a group-sequential 1-sided repeated CI for the HR must be