Shares in Merck & Co have slipped after the drugmaker announced that its investigational acute heart failure drug rolofylline has failed in a late-stage study.

The New Jersey-based firm says that preliminary results for a Phase III study of MK-7418 (rolofylline) show that the drug did not meet the primary or secondary efficacy endpoints. Merck added that it will continue to analyse the data “with outside experts” but will not file applications for regulatory approval this year.

The primary hypothesis of the 2,033-patient study, called PROTECT, was that rolofylline 30mg would improve symptoms of acute heart failure compared to placebo. The secondary endpoints were that the drug would reduce the risk of death or cardiovascular or renal re-hospitalisation 60 days after treatment, and reduce the incidence of persistent kidney impairment.

Dan Bloomfield, executive director of cardiovascular research at Merck, said that “advances to help patients with acute heart failure”, the leading cause of hospitalisation for people over 65 and associated with a high rate of mortality, “have long been elusive". He added that the results were disappointing “because we had been hopeful that blocking the adenosine A1 receptor with rolofylline would prove to be a useful new approach”.

Dr Bloomfield said that Merck remains committed to discovering treatments for heart failure and for cardiovascular disease, but the failure of rolofylline, which the firm acquired in 2007 when it purchased NovaCardia, is a big blow. It comes a year after a bid to revitalise its cholesterol portfolio was dealt a blow when the US Food and Drug Administration issued a not approvable letter for Tredaptive (extended-release niacin/laropiprant) for the treatment of mixed dyslipidemia and primary hypercholesterolemia.