Omecamtiv Mecarbil
Details
Omecamtiv mecarbil is the first selective cardiac myosin activator (myotrope) — a novel class of cardiac drug that directly augments systolic function by binding to cardiac myosin and increasing the number of force-generating myosin heads without affecting intracellular calcium transients. This calcium-independent mechanism distinguishes it from all traditional positive inotropes (digitalis, PDE3 inhibitors, beta-agonists), which improve contractility via calcium loading but consistently cause myocardial ischemia, ventricular arrhythmias, or death. In the phase 3 GALACTIC-HF trial (NEJM 2021; n=8,232; LVEF ≤35%), omecamtiv mecarbil reduced the primary composite of HF event or CV death (HR 0.92; P=0.03) but did not reduce CV death, all-cause death, or HF hospitalisation, and showed no QoL benefit. A prespecified LVEF subgroup interaction indicated benefit concentrated in LVEF ≤28%. The drug is not approved by FDA or EMA and is not guideline-listed as of May 2026.
Key Facts
Mechanism of Action
- Selective cardiac myosin activator (myotrope) — distinct class from all prior positive inotropes
- Binds directly to cardiac myosin, increasing the proportion of myosin heads entering the pre-power stroke (force-generating) configuration → more productive cross-bridge cycles at the start of systole → greater systolic force and ejection
- Does not affect intracellular calcium transients — the fundamental mechanistic safety differentiation from inotropes that cause ischemia/arrhythmia via calcium overload
- Physiological effects (COSMIC-HF phase 2): increased LV systolic ejection time and stroke volume; decreased LV volumes (reverse remodeling); reduced NT-proBNP and heart rate (sources/omecamtiv-galactichf-nejm-2021, rating: high)
Phase 2 — COSMIC-HF (Lancet 2016)
- Phase 2 pharmacokinetic RCT in chronic HFrEF; omecamtiv mecarbil vs placebo for 20 weeks
- Increased LVST and stroke volume; decreased LV systolic and diastolic volumes; reduced NT-proBNP and heart rate
- Confirmed target engagement and provided haemodynamic rationale for the phase 3 design (sources/omecamtiv-galactichf-nejm-2021, rating: high)
Phase 3 — GALACTIC-HF (NEJM 2021)
- Trial: GALACTIC-HF (Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure)
- Population: n=8,232; LVEF ≤35%; NYHA II–IV; inpatients + outpatients; 945 sites, 35 countries; median 21.8 months; >19% ARNi; 2.6% SGLT2i (pre-DAPA-HF era)
- Dosing: Pharmacokinetic-guided 25 mg, 37.5 mg, or 50 mg BID
- Primary outcome (HF event or CV death): HR 0.92 (95% CI 0.86–0.99; P=0.03); 37.0% vs 39.1%; 2.1 pp absolute reduction; 8% RRR
- CV death: HR 1.01 (95% CI 0.92–1.11) — not significant
- All-cause death: HR 1.00 (95% CI 0.92–1.09) — not significant
- First HF hospitalisation: HR 0.95 (95% CI 0.87–1.03) — not significant
- KCCQ: inpatients +2.5 pts (below 5-point MCID), outpatients −0.5 pts; joint test did not meet prespecified alpha 0.002 — not significant
- NT-proBNP at week 24: 10% lower vs placebo (geometric mean; 95% CI 6–14%) — favourable biomarker signal
- Troponin I at week 24: +4 ng/L vs placebo — small; below ULN (40 ng/L); no adjudicated ischemic excess (sources/omecamtiv-galactichf-nejm-2021, rating: high)
LVEF Subgroup — Critical Heterogeneity (Prespecified)
- Prespecified analysis by median LVEF (28%):
- LVEF ≤28%: HR 0.84 (95% CI 0.77–0.92) — meaningful benefit
- LVEF >28%: HR 1.04 (95% CI 0.94–1.16) — no detectable benefit
- Statistically significant interaction — most clinically important prespecified subgroup
- Biological basis: more impaired systolic function = greater potential for myosin activation to improve force generation
- Implication: if approved, benefit-risk profile most favourable at LVEF ≤28%; evidence does not support broad use across the LVEF ≤35% criterion (sources/omecamtiv-galactichf-nejm-2021, rating: high)
Safety Profile
- Major cardiac ischemic events: 4.9% vs 4.6% — similar to placebo
- Ventricular arrhythmic events: similar to placebo
- No effect on potassium, creatinine, systolic BP
- Heart rate slightly lower in omecamtiv mecarbil group
- Troponin I +4 ng/L — small, without clinical correlate; no excess MI; partially unresolved
- Drug withheld for suspected ACS: 103 vs 101 — balanced; no excess ACS signal (sources/omecamtiv-galactichf-nejm-2021, rating: high)
Regulatory and Guideline Status (May 2026)
- Not approved by FDA or EMA
- Not included in AHA 2022 or ESC 2021 HF guidelines
- Status: investigational; phase 3 completed; drug development status uncertain post-GALACTIC-HF
Contradictions / Open Questions
- Primary composite significant but all secondary outcomes NS: The primary outcome (HR 0.92; P=0.03) is statistically significant but all secondary outcomes — CV death (HR 1.01), all-cause death (HR 1.00), first HF hospitalisation (HR 0.95), KCCQ — were non-significant. A drug with a narrowly positive composite but neutral mortality and QoL offers limited clinical argument; the absolute benefit (2.1 pp) is modest and the trial barely cleared the P=0.05 threshold. (sources/omecamtiv-galactichf-nejm-2021, rating: high)
- LVEF interaction challenges the full LVEF ≤35% indication: Benefit appears confined to LVEF ≤28% (HR 0.84) with no effect at LVEF 29–35% (HR 1.04). This suggests the approved population — if approval occurs — should be restricted to the lowest LVEF patients, which substantially narrows the candidate pool and raises questions about the drug's role alongside SGLT2i/ARNi at higher HFrEF LVEF values. (sources/omecamtiv-galactichf-nejm-2021, rating: high)
- Pre-SGLT2i era background: Only 2.6% on SGLT2i (enrolled 2017–2019 before DAPA-HF/EMPEROR-Reduced). SGLT2i independently reduces HF hospitalisations — which are the dominant driver of the GALACTIC-HF primary composite. The incremental benefit of omecamtiv mecarbil on top of modern quadruple GDMT (ARNi + BB + MRA + SGLT2i) is unknown and likely smaller than the trial estimate. (sources/omecamtiv-galactichf-nejm-2021, rating: high)
Connections
- Related to entities/HFrEF — population; management context; Additional Agents section
- Related to entities/Heart-Failure — full HF hub