Aug 31 Bayer will move a new heartfailure drug into final-stage testing this year, boosting itsambitions in cardiovascular medicine, after the experimentalmedicine proved better than an older rival in a mid-stage trial.

Having done well with recently launched drugs like strokeprevention pill Xarelto and eye treatment Eylea, the Germangroup is eager to show it has another potentialbillion-dollar-plus winner in finerenone.

Finerenone, which is still several years from reaching themarket, is an improved version of an troublesome class of heartdrugs called mineralocorticoid receptor antagonists (MRAs).

Existing MRAs spironolactone and eplerenone, branded asInspra by Pfizer, are unsuitable for many patients since they can cause abnormally high levels of potassium in theblood, leading to irregular heart beat or even cardiac arrest.

The two older medicines, whose patents have expired, arealso linked to kidney problems.

Bayer's pill, however, works in a different way and appearsto avoid these issues, so cardiologists are watching itsdevelopment closely.

"If you can eliminate hyperkalaemia (high potassium) thatwould be a huge benefit to patients," said Mary Norine Walsh,vice president of the American College of Cardiology, who wasnot involved in the research.

Phase II trial data presented in London on Monday showedfinerenone led to fewer deaths and fewer hospitaladmissions among participants during 90 days of initialtreatment, when compared to a control group on eplerenone.

"We didn't expect to see these clearly better resultsalready in Phase II," said Frank Misselwitz, head of thetherapeutic area cardiovascular and coagulation at Bayer.

He added that potassium levels in the blood were alsobetter.

A blood reading to measure stress on the heart, which wasthe trial's primary efficacy measure, was at levels comparableto the control group, as was the level of overall side effects,according to results presented at the European Society ofCardiology annual meeting.

Bayer will enrol more than 3,600 patients with heart failureand diabetes and/or kidney disease in its final-stage Phase IIIstudy. It has said previously it would also start Phase IIItests of the drug in diabetic kidney disease.

There has been little progress for more than a decade intreating heart failure, in which the heart fails to pump enoughblood around the body, but competition is starting to heat up.

Novartis recently won approval for its drugEntresto that can cut the risk of both cardiovascular death andhospital admissions by a fifth, and which is forecast byanalysts to generate annual sales of more than $5 billion by2020.

Finerenone may only reach the market in 2020 or 2021,according to analysts, leaving its prospects uncertain, althoughBerenberg and Deutsche Bank have pencilled in potential sales of$1.8 billion and $2.0 billion respectively. (Editing by William Hardy)