Delcasertib is a peptide inhibitor of protein kinase C-delta, developed by KAI Pharmaceuticals. Delcasertib disrupts binding of delta-PKC to its receptor for activated C kinase, thereby preventing localization of delta-PKC to the mitochondria during periods of myocardial ischemia and reperfusion. In preclinical studies, when given as a single intracoronary dose, delcasertib reduced infarct size, enhanced early recovery of regional left ventricular contractility, and improved microvascular patency and function in animal models of acute myocardial infarction. The compound diminished myocardial necrosis and improved reperfusion in a pilot study during the primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI). In a larger clinical trial, however, intravenous infusion of delcasertib during PCI for acute STEMI in a population of patients treated according to the contemporary standard of care did not reduce biomarkers of myocardial injury.