GALACTIC-HF: Novel Drug Most Effective in Sickest HFrEF Patients

Ted Bosworth

May 24, 2021

The greatest relative benefit from omecamtiv mecarbil, a member of the novel myotropic drug class that improves cardiac performance, is produced in heart failure patients with the lowest left ventricular ejection fraction (LVEF), a new analysis of the recently published phase 3 GALACTIC-HF trial has found.

The findings reinforce the potential for this drug to be helpful in the management of the most advanced stages of heart failure with reduced ejection fraction (HFrEF), reported John R. Teerlink, MD, director of heart failure at San Francisco Veterans Affairs Medical Center, at the annual scientific sessions of the American College of Cardiology.

The phase 3 multinational GALACTIC-HF trial, published earlier this year, linked omecamtiv mecarbil with an 8% reduction in the risk of a heart failure-related events or cardiovascular death, relative to placebo, which was the primary outcome. For entry, HFrEF patients were required to have a LVEF of 35% or less.

Drilling Down on Ejection Fraction

The new analysis divided participants into quartiles of baseline LVEF and then compared relative outcomes and safety.

In the lowest quartile, defined by a LVEF of 22% or lower, the reduction in risk of events reached 17% (hazard ratio, 0.83; 95% confidence interval, 0.73-0.95) for omecamtiv mecarbil relative to placebo. In the highest, defined by a LVEF of 33% or greater, the benefit fell short of significance (HR 0.99; 95% CI, 0.84-1.16). Across quartiles, LVEF was the "strongest modifier of the treatment effect," emerging in this analysis as a statistically significant (P = .004) continuous variable.

The comparison by LVEF quartiles also provided an opportunity to show that omecamtiv mecarbil was as safe and well tolerated in those with the most advanced disease as in those less sick. At the lowest levels of LVEF, like the higher levels, omecamtiv mecarbil did not produce any adverse effects on blood pressure, heart rate, potassium homeostasis, or renal function.

In GALACTIC-HF, 8,256 HFrEF patients with LVEF 35% or less were randomized to omecamtiv mecarbil or placebo. The primary composite outcome of hospitalization or urgent visit for heart failure or death from cardiovascular causes was evaluated after a median of 21.8 months on therapy.

When incidence rate per 100 patient years was graphed against the range of LVEF, the relative advantage of omecamtiv mecarbil became visible just below an LVEF of 30%, climbing steadily even to the lowest LVEF, which reached 10%.

Perhaps relevant to the reduction in events, there were also greater relative reductions in NT-proBNP (NT-proB-type natriuretic peptide) for omecamtiv mecarbil at lower relative to higher LVEF. Although omecamtiv mecarbil is not associated with any direct vascular, electrophysiologic, or neurohormonal effects, according to Teerlink, the indirect effects of selective binding to cardiac myosin has been associated with lower NT-proBNP and other biomarkers of cardiac remodeling in prior clinical studies.

Although Teerlink acknowledged that relatively few patients in GALACTIC-HF received an angiotensin-receptor neprilysin inhibitor (ARNI) or a sodium glucose cotransporter-2 (SGLT2) inhibitor, he said there is "every reason to believe that omecamtiv mecarbil would be complementary to these therapies." He said the mechanism of action of omecamtiv mecarbil, which improves systolic function, has no overlap with these drugs.

Importantly, there is a particular need for new treatment options in patients with advanced LVEF, according to Teerlink, who cited evidence, for example, that "the beneficial effect of [the ARNI] sacubitril valsartan, while still significant, decreases in patients with LVEF less than 35%."

Overall, based on these results, "we believe that omecamtiv mecarbil represents a novel therapy that holds the promise of improving clinical outcomes in patients with severely reduced ejection fraction, which are the very patients that are most challenging for us to treat," Teerlink said.

Omecamtiv Mecarbil May "Buy You Some Time"

Ileana Piña, MD, clinical professor of medicine, Central Michigan University, Mount Pleasant, Mich., agreed. She said that omecamtiv mecarbil, if approved, will be an option for the type of HFrEF patients who are being considered for heart transplant or mechanical-assist devices.

"We are very loath to use inotropes in this population, because we know that ultimately the inotrope is not going to do well," said Piña, calling these therapies a "Band-Aid." Based on the evidence from GALACTIC-HF, she thinks that omecamtiv mecarbil will be more versatile.

"This drug does not increase myocardial oxygen demand as do the inotropes, and it can be given in the outpatient setting if need be, so I see this as a real advance," Piña said. Although Piña acknowledged that omecamtiv mecarbil did not reduce mortality in the GALACTIC-HF trial, "at least it will buy you some time."

Teerlink has financial relationships with multiple pharmaceutical companies, including Amgen, Cytogenetics, and Servier, which provided funding for the GALACTIC-HF trial. Piña reports no potential conflicts of interest.

American College of Cardiology (ACC) 2021 Scientific Session

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