PARIS (AP) — French drug maker Sanofi says its net profit was more than halved in the fourth quarter from a year earlier as mounting restructuring costs and patent losses on key drugs combined to hammer earnings.

Sanofi said Thursday that its net profit was €438 million ($593 million) in the October-December quarter, down from €1.5 billion a year earlier. Sales were flat at €8.5 billion in the quarter. Restructuring costs rose over €100 million to €834 million.

The company blamed the loss of U.S. patent protection on key drugs Plavix and Avapro cost it €1.3 billion last year.

Sanofi warned its core earnings per share could fall up to 5 percent this year, after a 12.8 percent drop in 2012.