(Reuters) - AbbVie Inc’s Chief Executive Officer Richard Gonzalez said on a conference call that rivals Biogen Inc and Amgen Inc had been the most aggressive in Europe with their biosimilar versions of its blockbuster drug Humira.

Sales of rheumatoid arthritis drug Humira have accounted for the bulk of AbbVie’s total revenue for years, but competition from new, cheap rivals in Europe has recently hit its results.

Novartis, Mylan Inc and other drugmakers have also launched Humira biosimilars in Europe.