Good answers Bfw and Koo. Just to elaborate on Koo's response, half patients are placebo. Even if apabetalone causes a ~50% relative risk reduction, the trial will still accumulate 125 and 250 events (though it may take longer to reach event milestones if apabetalone is working that good!) This is assuming of course that the trial isn't stopped early for good (or for bad) reasons.
BearDownAZ