STRUCTURE: Mavacamten, 3-(1-methylethyl)-6-[[(1S)-1-phenylethyl]amino]-2,4(1H,3H)-pyrimidinedione, is a reversible small-molecule allosteric inhibitor of cardiac myosin ATPase with a molecular formula of C15H19N3O2 and molecular weight of 273.33 g/mol. It belongs to the pyrimidinedione drug class.