Omecamtiv Mecarbil

Omecamtiv mecarbil (CK-1827452, AMG 423) is a first-in-class selective small-molecule activator of cardiac myosin, the beta-myosin heavy chain (MYH7) motor protein of the ventricular sarcomere. Discovered at Cytokinetics, Inc. through high-throughput screening of a reconstituted calcium-responsive sarcomere assay and advanced through extensive structure-activity optimization from a poorly soluble nitro-aromatic hit compound, omecamtiv mecarbil binds an allosteric pocket on the cardiac myosin catalytic domain (S1 subfragment) that stabilizes the lever arm in a primed, pre-powerstroke conformation. The compound accelerates the rate-limiting phosphate release step of the cross-bridge cycle, increasing the number of myosin heads engaged with the actin filament during systole and prolonging the duration of force generation, without increasing intracellular calcium concentration or myocardial oxygen consumption. X-ray crystallographic studies have resolved the binding site at 2.45 Angstrom resolution, revealing interactions with the converter domain, relay helix, and N-terminal subdomain that induce a 15-degree rotation and approximately 4 Angstrom translation of the converter. Selectivity for cardiac over skeletal and smooth muscle myosin is structurally rationalized by divergent converter domain residues across isoforms. The clinical development program, spanning nine Phase 1 studies, four Phase 2 trials, and two Phase 3 trials over more than a decade, has established the pharmacodynamic signature of omecamtiv mecarbil: concentration-dependent prolongation of systolic ejection time, increased stroke volume and ejection fraction, decreased ventricular volumes, and reduced NT-proBNP, achieved without the tachycardia, hypotension, or proarrhythmic signals characteristic of catecholamine-based inotropes. The pivotal GALACTIC-HF trial (n = 8,256; NCT02929329) demonstrated a statistically significant reduction in the primary composite endpoint of cardiovascular death or first heart failure event (hazard ratio 0.92; 95% CI 0.86 to 0.99; p = 0.03), with the treatment benefit concentrated among patients with the lowest baseline ejection fractions (LVEF 22% or below: HR 0.83; 95% CI 0.73 to 0.95) and highest NT-proBNP levels. Cardiovascular death alone was not significantly reduced (HR 1.01). The METEORIC-HF trial (n = 276; NCT03759392) found no significant improvement in peak exercise capacity over 20 weeks, indicating that the cardiovascular outcomes benefit may operate through reduction of heart failure decompensation events rather than augmented peak aerobic performance. Pharmacokinetics are characterized by high oral bioavailability (approximately 93%), a terminal half-life of approximately 18 to 21 hours supporting twice-daily dosing, metabolism primarily through a decarbamylation pathway with modest CYP3A4 and CYP2D6 contributions, and balanced renal and fecal elimination. Omecamtiv mecarbil does not prolong the QTc interval at therapeutic concentrations. The compound received a Complete Response Letter from the United States Food and Drug Administration in February 2023; a confirmatory Phase 3 trial (COMET-HF) in patients with severely reduced ejection fraction is ongoing with expected completion in 2028. This monograph reviews the chemistry, structural pharmacology, comprehensive pharmacokinetic characterization, the complete clinical evidence base including positive and negative trials with subgroup analyses, the sourcing and handling considerations for research applications, and a comparative assessment of five heart failure agents against omecamtiv mecarbil on five competency standards. The compound is investigational and is not approved by any regulatory authority.