The CYP2C19 genotype and clopidogrel responsiveness were also investigated in the CHANCE trial, and it was discovered that the use of clopidogrel plus aspirin compared with the use of aspirin alone reduced the risk of a new stroke only in the subgroup of patients who were not carriers of the CYP2C19 loss-of-function alleles. The gene discussed is CYP2C19; the disease is Stroke.