ZURICH, Feb 1 (Reuters) - Swiss drugmaker Roche expects erosion of Rituxan sales in Europe will intensify in 2018 as cheaper copies made by rivals gather momentum, its drug unit said on Thursday.
Revenue for Roche's top-selling blood cancer medicine in Europe plunged 26 percent in the fourth quarter of 2017, after a 16 percent third-quarter drop following patent losses.
Overall, the medicine's full-year sales rose by 1 percent to 7.4 billion Swiss francs ($7.99 billion), as sales in the United States -- where patents remain valid until mid-2018 -- offset the European slump.
But with more Rituxan biosimilar launches from Novartis and Celltrion across Europe on the way, O'Day said the decline will worsen.
"We'll see an acceleration of this exposure... all expected in the first half of the year," Roche pharmaceuticals chief Dan O'Day told analysts in London.
Roche on Thursday forecast U.S. tax changes would help profit growth outstrip sales in 2018.
But the Basel company's vulnerability to biosimilars is growing: Beyond Rituxan, up to five biosimilar copies of Roche's $7 billion-per-year cancer drug Herceptin could be introduced this year, O'Day said.
Roche Chief Executive Severin Schwan acknowledged Roche's 2018 sales target-- for flat or low-single-digit percentage growth -- is "more cautious" than in years past due to biosimilar threat. ($1 = 0.9267 Swiss francs) (Reporting by John Miller, editing by John Revill)