APJ receptor agonist 5 (compound 3) is a potent and orally active agonist of apelin receptor ( APJ ) with an EC 50 of 0.4 nM. APJ receptor agonist 5 displays excellent pharmacokinetic profiles in the rodent heart failure (HF) model. APJ receptor agonist 5 also shows an acceptable safety profile in preclinical toxicology studies. APJ receptor agonist 5 leads to improved cardiac function and can be used for researching the HF disease.