AstraZeneca/Rigel's fostamatinib shows positive response in rheumatoid arthritis in Ph IIb study

Anglo-Swedish drug major AstraZeneca’s (LSE: AZN) new oral syk inhibitor, fostamatinib (R788), in-licensed from US firm Rigel Pharmaceuticals (Nasdaq: RIGL), significantly improved outcomes of patients with rheumatoid arthritis (RA) who responded inadequately to ongoing treatment with methotrexate (MTX), according to Phase II study data published in The New England Journal of Medicine today.

Development and commercialization rights to the drug were acquired earlier this year in a deal that could cost AstraZeneca as much as $1.25 billion in upfront and milestone payments, providing the London-headquartered firm. AstraZeneca plans to commence the Phase III clinical trial program - called OSKIRA (Oral Syk Inhibition in Rheumatoid Arthritis) - for fostamatinib shortly.

In the six-month Phase IIb study completed by Rigel, known as TASKi2, 67% of patients taking fostamatinib 100mg twice daily achieved the primary efficacy endpoint (ACR 20)* at six months, which was significantly higher than placebo. 36% of patients achieved an ACR 20 response after just one week. Speed of onset may be an important factor in RA because permanent joint damage can occur when the disease is active, the report noted. The most common adverse events included diarrhea and upper respiratory infection.