A new study shows that Swiss drug maker Roche AG’s cancer treatment MabThera, called Rituxan in the US, helps ease the symptoms of rheumatoid arthritis, suggesting that sales of the blockbuster drug stand to climb if approval is granted.

Preliminary phase IIb data shows that the drug alleviates symptoms of patients with moderate-to-severe rheumatoid arthritis, Roche said on Tuesday.

The study showed improved symptoms in patients who received two infusions of the drug over a two-week period in combination with a stable dose of methotrexate compared to those who received methotrexate and a placebo.

The drug, marketed in the United States by Biogen Idec and Roche’s California-based Genentech unit, was originally approved as a treatment for non-Hodgkins lymphoma (NHL) but has also been shown to be effective against arthritis. Roche has said that the new indication for the product, currently its biggest-selling drug, could generate additional annual sales of around 500 million Swiss francs.

Sales in 2003 were around 2.8 billion Swiss francs ($2.3 billion).

“Roche has said sales in the indication could reach 500 million francs, thus providing a nice upside to our current estimates,” said Denise Anderson at Kepler Equities, adding that phase III testing is planned with filing possible for 2007.

In addition to the trials for Rituxan/MabThera in arthritis, Roche’s biotechnology division, Genentech, is testing a second-generation compound, currently in phase I/II, she said.

Roche said details of the phase IIb MabThera study, the second randomized trial to look at Rituxan/MabThera’s effect on RA sufferers, would be presented at an upcoming medical meeting.

A total of 465 patients from the United States, Canada, Europe and Australia took part in the multi-center, randomized, trial.

Safety is a key issue in arthritis, since the antibody-based medicine has a broad mechanism of action that might cause adverse side effects if it is given for lengthy periods. It is not used on a long-term basis in its current role as a treatment for non-Hodgkin’s lymphoma.

“A preliminary analysis of the data did not reveal any unexpected safety signals,” Roche said in a statement. “All regimens were generally well tolerated.”

Roche certificates, the most widely traded form of equity, were trading flat at 122.90 Swiss francs at 5:24 a.m. EST in a slightly firmer Swiss market, bringing year-to-date losses to some 1.4 percent.