GPV0057 (Compound 5d) is a potent and selective inhibitor of P-glycoprotein (P-gp). It also acts as a selective activator of the potassium channel Kir2.1. By competitively binding at the substrate binding site of P-gp, GPV0057 inhibits ATP-dependent drug efflux, thereby reversing multidrug resistance in tumor cells. Additionally, it stabilizes the open state of Kir2.1, enhancing potassium ion influx. GPV0057 has potential applications in the study of tumors with high P-gp expression and Kir2.1-related diseases, such as heart failure and Andersen-Tawil syndrome.