WASHINGTON (AP) -- Shares of AstraZeneca and its partner Rigel Pharmaceuticals Inc. fell Thursday after the companies reported that their experimental rheumatoid arthritis drug was less effective than Abbott's Humira in a midstage study.
THE SPARK: AstraZeneca reported results for a six-month study of its drug fostamatinib in 280 patients with hard-to-treat rheumatoid arthritis. The trial tested three doses of the drug: 100 milligrams twice daily, 100 milligrams twice daily for a month followed by 150 milligrams once daily, and 100 milligrams twice daily for a month followed by 100 milligrams once daily.
The drug met its first goal of showing superior results compared to a placebo after six weeks for the first two doses tested. But all doses of the drug showed worse results than Humira after six months of treatment. The study was designed to show that fostamatinib worked as well as Humira in managing rheumatoid arthritis symptoms.
THE BIG PICTURE: Humira, an injectable anti-inflammatory drug, is the world's best-selling rheumatoid arthritis treatment, with sales of roughly $9 billion a year. AstraZeneca and other large drugmakers have been working to develop rival treatments to compete with the blockbuster drug. The company's drug fostamatinib, licensed from Rigel, is a pill that blocks the protein kinase, which plays a role in a variety of inflammatory diseases. Rheumatoid arthritis occurs when the immune system attacks the body's own joints and tissue. It differs from traditional arthritis, which is caused by long-term deterioration of bones and joints. Rheumatoid arthritis affects about 1.3 million people in the U.S., according to the Arthritis Foundation.
AstraZeneca said the latest results should not be taken as definitive. The company is conducting a larger study of the drug's benefits which is expected to be completed in the first half of 2013. The company says those results will be the basis of its application to the Food and Drug Administration and other regulators.
SHARE ACTION: Shares of South San Francisco-based Rigel Pharmaceuticals Inc. fell $3.01, or 34.7 percent, to $5.42 in midday trading after falling as low as $5.37 earlier, its lowest level since early30009. U.S.-traded shares of AstraZeneca PLC fell $1.30, or 2.7 percent, to $47.60. Shares of Abbott Laboratories fell $1.04, or 1.6 percent, to $64.97.