The present study found ticagrelor-aspirin to be superior to clopidogrel-aspirin among patients with ischemic stroke regardless of whether they had 1 (intermediate metabolizers) or more than 1 (poor metabolizers) nonfunctional copy of CYP2C19. Intermediate metabolizers showed no differences in safety or efficacy from poor metabolizers; the 2 groups could be categorized as a single entity for use of ticagrelor-aspirin for secondary prevention. This evidence concerns the gene CYP2C19 and ischemic stroke.