Actelion has reported a 69 percent drop in first quarter net profits amid dropping revenue and a strong Swiss franc.

The Swiss pharmaceutical firm, Europe's biggest biotech company, saw net profit fall to 45.1m Swiss francs (£30.7m) , or the equivalent of 0.38 francs per share, from 146.3m francs, representing 1.2 francs per share.

"As expected the marketplace remains very challenging, mostly due to changes in the competitive landscape in the United States and strong pricing pressures in certain markets," said chief executive Jean-Paul Clozel.

The company said it expected results of a late-stage clinical trial on heart and lung disease drug macitentan in the coming weeks, the success of which will be pivotal in Actelion continue to lead the field in pulmonary arterial hypertension.

Actelion's leading product, Tracleer, which accounts for as much as 90 percent of group sales, faced falling sales in the face of strong performances from rivals. Sales of Tracleer dropped by 39.1m francs to 363.7m francs over the year.

Actelion said it expected to see sales in local currencies decrease by a low single digit percentage in 2012, a slight improvement on low to middle single digit declines originally forecast.

"In the first quarter of 2012, Actelion's overall performance reflects the dynamics of the marketplace, including the continued strength of the Swiss franc," said Andrew J. Oakley, Chief financial officer of Actelion.

"Unforeseen events excluded, Actelion can now provide an improved product sales forecast. The decrease in local currencies is now expected to be in the low single-digit range. Actelion remains of track to meet its previously issued guidance of flat 2012 core earnings."

Actelion shares were trading down around 2 percent in Zurich immediately following the results, changing hands at 33 francs per share.