In conclusion, we have developed a novel and highly potent MCL-1 inhibitor, APG-3526, which displays clinically relevant pharmacokinetic properties and elicits potent antiproliferative and antitumor activities via disrupting MCL-1 complex and triggering caspase activation, especially in MCL-1 driven MM models. These results support APG-3526 as a promising MCL-1inhibitor for further clinical development.