Humira is one of the world's top-selling medicines, garnering more than $8 billion per year, but is facing growing competition from other therapies including a pill being developed by Pfizer.

Karsten Jung, Head GPS Immunology at Roche said the aim of the trial was to give comparative data to doctors to help them to decide in favour of RoActemra, also known as Actemra outside of Europe, when prescribing treatment.

"Among a treatment environment of nine different medicines, it is very difficult to make an individual treatment decision for the physician. They are looking for reasons why they should choose one over the other," Jung told Reuters.

Roche's drug has been approved in United States and Europe for use in patients who are either intolerant to or have failed to respond to other medicines to treat inflammation.

Roche said the results of the 24-week study of 326 patients, will be presented on June 8 at the European League Against Rheumatism (EULAR) meeting in Berlin.

About 1 percent of the world's adult population has rheumatoid arthritis, a potentially crippling condition in which the body's own immune system attacks the joints.

(Reporting by Caroline Copley; Editing by Edwina Gibbs)

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