Israel-based Teva Pharmaceuticals Industries has begun the testing of a copycat biosimilar version of Roche’s blockbuster rheumatoid arthritis drug, Rituxan.

Teva has launched a clinical trial of the drug, called TL011, in severe, active rheumatoid arthritis that will be complete in mid-2011.

The drug, which is sold by Biogen Idec and Roche, and had global sales of $5.7bn in 2009, could be the first major drug to face competition from a biosimilar since a regulatory pathway for biosimilars was opened during recent healthcare overhauls in the US.

Although the drug may still take many years to reach the market, the trial is one of the first attempts to create a genetic version of complex biotech drugs, a process which unlike traditional generic development requires clinical testing.

Rituxan is approved to treat non-Hodgkin’s lymphoma, chronic lymphocytic leukaemia and rheumatoid arthritis.