The future of a key drug in Novartis' late-stage portfolio is looking bleaker after advisors to the US Food and Drug Administration said they could not recommend approval of serelaxin, hot on the heels of a thumbs down in Europe.

A review by the FDA's Cardiovascular and Renal Drugs Advisory Committee, posted online ahead of meeting involving external experts this week, concludes that serelaxin (proposed brand name Reasanz) should not be approved for acute heart failure (AHF) because Novartis has failed to provide enough evidence to support the proposed indication of improving symptoms 'through reduction of the rate of worsening of heart failure'.

The Swiss drug giant filed its application to market serelaxin - which carries Breakthrough Status in the US - on the back of just one trial showing that its addition to standard therapy helped to alleviate shortness of breath (dyspnoea) by slowing the rate of worsening heart failure, but the norm is to include evidence from two independent studies.

On the plus side, the reviewers stressed that they "did not identify any significant safety concerns precluding approval".

But given that the European Medicines Agency's Committee for Medicinal Products for Human Use came to pretty much the same conclusion earlier this year, ruling that trial data failed to show a benefit for short-term relief of dyspnoea over up to 24 hours, it is looking like there could well be a significant delay to serelaxin's market entry on both sides of the Atlantic.

It is estimated that 5 million people in the US are living with chronic heart failure, of which about one million are hospitalised with episodes of acute heart failure.

If regulatory clearance is issued, serelaxin is forecast to make sales of $713 million by 2018, according to an average estimate of five analysts polled by Thomson Reuters.