Rigel says rheumatoid arthritis drug met goal

SOUTH SAN FRANCISCO - Rigel Pharmaceuticals Inc. said Thursday its rheumatoid arthritis drug candidate was shown to reduce patients' symptoms in a midstage clinical trial, meeting the study's goal.

Rigel said patients treated with the drug candidate R788, or fostamatinib disodium, had lower scores on two disease scales compared with patients who received a placebo. The company said it plans to find a partner to help develop the oral drug, and then begin late-stage testing in early 2010.

Rigel said more than 2 million people in the U.S. have rheumatoid arthritis, which is a chronic inflammatory disease that affects the joints and destroys soft tissue, cartilage and bone.

In the six-month study, patients were treated with either 100 mg of R788 twice per day, 150 mg once per day, or a placebo. All patients were also treated with methotrexate, a drug commonly used against rheumatoid arthritis. Their symptoms were then measured based on scales developed by the American College of Rheumatology or the Disease Activity Score.

Among patients treated with 100 mg of R788 twice per day, Rigel said 66 percent saw improvement of at least 20 percent in their symptoms, while 43 percent had 50 percent improvement and 28 percent saw 70 percent improvement or better. For patients who received 150 mg once a day, 57 percent had a 20-percentage point improvement, 32 percent had a 50 point improvement and 14 percent improved by at least 70 percent.

That compares with 35 percent of people on placebo seeing improvement of 20 percent, 19 percent seeing 50 percent improvement and 10 percent seeing their symptoms get better by 70 percent or more. Those results are based on the ACR score, which assesses symptoms and pain levels. The R788 patients also had better disease activity scores after six months.

The most common side effects in the trial were diarrhea and hypertension.

Rigel is a development-stage company with no products currently on the market. R788 is its most advanced drug candidate. In addition to rheumatoid arthritis, it is also testing the drug against B-cell lymphoma and idiopathic thrombocytopenic purpura, a condition in which the immune system destroys blood platelets for unknown reasons. That leaves patients at increased risk of bleeding.

In Thursday trading, Rigel shares surged $1.92, or 17.1 percent, to close at $13.16.

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