Conference Coverage

Oral danicamtiv improves left atrial contractility in HFrEF



Danicamtiv, a novel oral selective cardiac myosin activator, demonstrated promising beneficial effects on left ventricular systolic function coupled with marked improvements in left atrial volume and function in patients with heart failure with reduced ejection fraction in a phase 2a clinical trial, Adriaan A. Voors, MD, PhD, said at the European Society of Cardiology Heart Failure Discoveries virtual meeting.

Importantly, these improvements weren’t accompanied by any unwelcome significant increase in diastolic stiffness, added Dr. Voors, a cardiologist at the University of Groningen (the Netherlands).

This is a drug whose novel mechanism of action could make it a good fit in combination with existing guideline-recommended therapies known to improve morbidity and mortality in patients with heart failure with reduced ejection fraction (HFrEF), none of which do what danicamtiv does: namely, activates cardiac myosin by enhancing myofibrillar adenosine triphosphatase activity, thereby boosting intrinsic myocardial contractility without any impact upon calcium homeostasis, he explained.

Dr. Voors reported on 40 patients with stable HFrEF and a left ventricular ejection fraction of 35% or less, all on background guideline-directed medical therapy. They were randomized double blind to 7 days of danicamtiv at 50, 75, or 100 mg twice daily, or placebo. A total of 489 ECGs were performed in conjunction with blood draws to measure plasma drug concentrations during the study.

Danicamtiv significantly improved left ventricular stroke volume and global longitudinal and circumferential strain in plasma drug concentration–dependent fashion, while simultaneously decreasing left ventricular end-systolic and end-diastolic diameters. Danicamtiv increased systolic ejection time from 286 milliseconds at baseline by an additional placebo-corrected 15, 36, and 48 milliseconds in patients with low, mid-range, and high drug concentrations.

The cardiac myosin activator’s concentration-dependent salutary effects on left atrial (LA) parameters in this brief study were intriguing, since LA function is often compromised in patients with heart failure and has been shown in prior observational studies to independently predict cardiovascular outcomes, the cardiologist noted. The favorable changes in response to danicamtiv included a reduction in LA minimal volume index and an increase in LA emptying fraction. Also, there were marked improvements in LA function index, by 6.1 and 5.8 points, respectively, in patients with mid- and high drug concentrations, from a baseline of 26 points.

Holter monitoring revealed no increased risk of atrial or ventricular arrhythmias in study participants.

Treatment-emergent adverse events were mild and/or unrelated to treatment and showed no particular pattern. The one serious adverse event in the study was a case of hyperkalemia deemed by investigators to be unrelated to treatment.

Seven of 30 danicamtiv-treated patients developed mild, transient, asymptomatic increases in serum cardiac troponin I and/or high-sensitivity troponin T. Dr. Voors said the significance of this must await further examination in larger clinical trials. A phase 2 clinical trial in patients with HFrEF and paroxysmal or persistent atrial fibrillation is planned in order to learn if chronic therapy with danicamtiv results in sustained LA remodeling and clinical benefits. Another planned phase 2 study will be conducted in patients with selected forms of genetic dilated cardiomyopathy.

Because danicamtiv appears to have no effects on blood pressure, renal function, or electrolytes, Dr. Voors speculated that the drug might prove to be an attractive therapeutic option in patients with advanced refractory heart failure, who often have low blood pressure, poor renal function, and a very low left ventricular ejection fraction.

Discussant Thomas Thum, MD, PhD, commented that danicamtiv has definitely earned an opportunity to show what it can do in larger, long-term clinical trials. He was impressed by the significant increase in systolic ejection time, a good marker for cardiac contractility. But he added that the troponin signal warrants careful scrutiny.

“The slight increase over baseline in the phase 2a study was not correlated with any ECG changes or clinical symptoms. However, whether this is a detrimental biomarker sign of a silent harm to the heart remains to be investigated,” said Dr. Thum, a cardiologist at the Institute of Molecular and Translational Therapeutic Strategies at Hannover (Germany) Medical School.

The phase 2a study finding of a plasma drug concentration–dependent prolongation in isovolumetric relaxation time “warrants some caution in future clinical development in patients with impaired diastolic function,” he added.

Simultaneous with Dr. Voors’ presentation, the study results were published online (Eur J Heart Fail. 2020 Jun 19. doi: 10.1002/ejhf.1933).

The danicamtiv study was sponsored by MyoKardia. Dr. Voors reported receiving research funding from and serving as a consultant to MyoKardia and numerous other companies.

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