The first in a new class of drugs to treat heart failure called cardiac myosin activators has shown encouraging activity in a small Phase II trial published in The Lancet (August 20).

The new drug, called omecamtiv mercabil, was developed by US drugmaker Cytokinetics and is licensed to Amgen. It targets the motor proteins that cause muscle contraction and prolongs the action of the left ventricle of the heart, which pumps blood around the body.

Rather than make the heart beat more often like current medicines, omecamtiv mercabil makes the heart muscles contract for longer, which increases the volume of blood the heart pumps with each stroke without increasing the amount of energy used.  That means it should not exhaust the heart, which can occur with currently-used inotropic agents and contribute to cardiac ischaemia.

The Phase II trial compared the intravenously-administered drug to placebo in 45 heart failure patients with impaired function of the left ventricle, who were also taking background therapy with ACE inhibitors and beta blockers. Omecamtiv mercabil increased left ventricular ejection time and stroke volume compared to control, alongside a small reduction in heart rate, suggesting that the hearts were working more effectively and efficiently.

Heart failure affects around 10 million people in the EU alone, according to Professor John Cleland of the University of Hull in the UK, who led the trial. While two-year survival rates among heart failure patients have advanced dramatically over the last 20-30 years, at least for those who receive advanced treatment, it still has a high mortality rate despite existing treatments.

"This is a totally new concept," said Prof Cleland. "We need to see whether the improvements in cardiac function translate into real benefits for patients, in terms of their symptoms and quality of life, and whether it can impact on mortality and morbidity."

Another Phase IIb trial should start next year, and if successful the drug could be on the market within the next three to four years, said Prof. Cleland. Cytokinetics is also developing oral formulation of omecamtiv mercabil, but this is unlikely to be ready to submit for approval for five years or more.