Danicamtiv

Danicamtiv (MYK-491, BMS-986434, SAR440181) is a selective, orally bioavailable small-molecule cardiac myosin activator that enhances myocardial contractility through direct modulation of the sarcomeric beta-myosin heavy chain (MYH7) without altering intracellular calcium homeostasis. Discovered at MyoKardia in 2016 through a high-throughput screening program designed to refine the pharmacodynamic profile of first-generation cardiac myosin activators, danicamtiv binds an allosteric site on the myosin S1 motor domain that is distinct from the binding site of omecamtiv mecarbil, the first-in-class cardiac myosin activator. The compound increases the proportion of myosin heads in the force-generating "ON" state by restructuring the thick filament and simultaneously slows cross-bridge turnover through inhibition of myosin ADP release, producing concentration-dependent increases in systolic ejection time, stroke volume, and left ventricular ejection fraction in both preclinical models and human studies. In permeabilized porcine cardiac tissue, danicamtiv at 1 micromolar shifts the calcium sensitivity of force (pCa50) from 5.72 to 5.91, reduces the Hill coefficient from 3.96 to 2.27, and decreases the rate of tension redevelopment (ktr) by more than 50 percent, consistent with enhanced myosin recruitment and prolonged cross-bridge attachment. X-ray diffraction studies confirm a shift in the equatorial intensity ratio (I1,1/I1,0) at rest, indicating repositioning of myosin heads away from the thick filament backbone toward actin filaments. In vivo, the compound produces a 27 percent relative improvement in ejection fraction in both wild-type and dilated cardiomyopathy mouse models at 2 mg/kg intravenous dosing. Preclinical pharmacokinetics predict a human plasma half-life of approximately 17.7 hours by allometric scaling, with low predicted hepatic clearance (0.5 mL/min/kg), moderate plasma protein binding (fraction unbound 0.16), and high Caco-2 permeability without efflux. Metabolism is predominantly CYP-mediated, involving amide cleavage, N-demethylation, and isoxazole and piperidine ring opening. A randomized, double-blind, placebo-controlled Phase 2a trial in 40 patients with stable heart failure with reduced ejection fraction (HFrEF; mean baseline LVEF 32 percent) demonstrated that danicamtiv at 50 to 100 mg in the published literature for 7 days produced concentration-dependent increases in stroke volume (7.8 mL at medium plasma concentrations, P less than 0.01), systolic ejection time (36 to 48 ms prolongation), and global circumferential strain, with concurrent improvements in left atrial function. Diastolic filling parameters were preserved at medium plasma concentrations. Transient asymptomatic cardiac troponin I elevations were observed in 23 percent of treated patients. A subsequent open-label Phase 2a trial in 41 patients with genetic dilated cardiomyopathy (12 MYH7 variant, 14 TTN variant, 15 other causes) reported LVEF improvements of 8.8 percent (MYH7 cohort) and 5.9 percent (TTN cohort) from baseline. Treatment-emergent adverse events were mild to moderate in all participants with one discontinuation. Danicamtiv was originally developed by MyoKardia, acquired by Bristol-Myers Squibb in the 13.1 billion dollar MyoKardia acquisition in November 2020, and subsequently licensed to Kardigan for worldwide development and commercialization in genetic dilated cardiomyopathy. No Phase 3 outcome trial has been completed. The compound is not approved by any regulatory authority and is classified as investigational. This monograph reviews the chemistry, molecular pharmacology, preclinical and clinical pharmacokinetics, clinical evidence base, sourcing and handling, stack interactions, adverse-event profile, and a comparative assessment of five cardiac myosin modulators against danicamtiv.