ERBB agonist-1 (Compound EF-1) is an agonist for ERBB4, that activates the ERBB4 signaling pathway by inducing dimerization of the ERBB4 receptor with an EC50 of 10.5 μM. ERBB agonist-1 induces phosphorylation of Akt and ERK1/2, reduces the collagen expression in cardiac fibroblasts, inhibits H2O2-induced cardiomyocyte death and Ang II -induced cardiomyocyte hypertrophy. ERBB agonist-1 prevents fibrosis and exhibits cardioprotective efficacy in mouse models.