Patients undergoing the percutaneous coronary intervention (PCI) for in-stent restenosis (ISR) are enrolled. All patients will be randomized to receive either 12 months or 24 months of dual antiplatelet therapy with a P2Y12 receptor antagonist in addition to aspirin, all patients continue receiving aspirin indefinitely. The primary efficacy end points of this study are the incidence of a composite end point including all cause deaths, myocardial infarction, the incidence of Academic Research Consortium defined definite or probable stent thrombosis and stroke (MACCE) at 24 months. The primary safety end point is the incidence of GUSTO moderate or severe bleeding.