Bristol Myers Squibb Co.’s audacious $13.1 billion 2020 takeover of Myokardia Inc. appears to have paid off with U.S. FDA approval of the drug at the heart of the deal, mavacamten. The medicine, a cardiac myosin inhibitor for treating adults with obstructive hypertrophic cardiomyopathy (HCM), will be marketed under the brand name Camzyos.