Actelion, Europe's biggest biotech company, is sticking to its forecast for core earnings to return to growth from 2014 as cost cuts and a new heart and lung treatment offset declining sales of its main drug.

The Swiss firm expects flat core earnings in local currencies in 2013 as its top-selling heart and lung drug Tracleer faces growing competition, it reiterated on Tuesday in slides to be presented at a JP Morgan Healthcare Conference later in the day.

Actelion has seen its future brighten over the past year after macitentan, its replacement for Tracleer, beat expectations in a clinical trial.

The firm also raised its 2012 earnings view twice last year after cost cuts helped improve profitability.

Actelion expects product sales to fall by a low single digit percentage and for core earnings to grow by a mid single digit in 2012, it said in the presentation published on its website.

After returning to earnings growth in 2014, the company expects double digit percentage growth in 2015, it added.

"In 2013, and the years to come, Actelion will realise the value it has created from innovation in our labs," Chief Executive Jean-Paul Clozel said in a statement.

The company is awaiting decisions from European and U.S. regulators on macitentan, which it plans to market under the name Opsumit.

Actelion also said it had bought back 383.4 million Swiss francs ($415.5 million) worth of shares by the end of 2012 in an accelerated 800 million franc share repurchase program.