Abstract Introduction Mechanisms driving disease progression and potential responsiveness to investigational therapies may theoretically differ among women with heart failure (HF) based on menopausal status. However, few data are available describing the clinical course of premenopausal and postmenopausal women with HF. We investigated differences in baseline characteristics, clinical outcomes, and response to omecamtiv mecarbil in premenopausal and postmenopausal women participants of the GALACTIC-HF trial. Methods The GALACTIC-HF trial randomized patients with symptomatic HFrEF with LVEF of 35% or less to omecamtiv mecarbil or placebo. Menopausal status at randomization was collected. When menopausal status was unknown/unreported, menopausal status was inferred based on the expected distribution of age at menopause in the general population. The risk of the primary endpoint, worsening HF event or cardiovascular death, was compared among women by menopausal status using Cox regression models adjusted for clinical covariates, including age and baseline EF. Treatment effect heterogeneity was evaluated by menopausal status. Results Of the 8,232 patients enrolled, 1,749 (21.2%) were women. Menopausal status was available at baseline in 1,483 (84.8%). One hundred women reported being potentially childbearing (pre-menopausal) and 1,383 women reported being post-menopausal. Among the 266 patients that had unknown menopausal status, those younger than 47 years were additionally classified as pre-menopausal and those older than 56 years as post-menopausal based on estimated 10th /90th percentiles extrapolated from the general population. Compared to post-menopausal women, pre-menopausal women were younger, had higher eGFR, and had fewer comorbidities. Premenopausal women also had slightly higher BMI and lower LVEF, but lower NTproBNP and troponin at baseline compared to postmenopausal women. Premenopausal and postmenopausal women had similarly high burden of symptoms as assessed by the KCCQ-total symptoms score (median 63.5 vs. 64.6; P=0.79). During a median follow-up of 22 months, premenopausal and postmenopausal women experienced similar rates of primary and secondary outcomes (Table 1). Omecamtiv mecarbil was beneficial across the entire female cohort with no effect modification by menopausal status (Pinteraction=0.39). Sensitivity analysis excluding all women with unknown menopausal status yielded similar results. Conclusions In this high-risk HFrEF cohort, premenopausal women experienced similar rates of adverse cardiovascular outcomes as post-menopausal women despite younger age, fewer comorbidities, and lower cardiac biomarkers. Additional research is necessary to understand how risk factors unique to females might influence outcomes in those with heart failure. The benefit of omecamtiv mecarbil on reducing cardiovascular risk was consistent regardless of menopausal status.Primary/secondary outcomes by menopausal