Phase 3 Results Promising for Fostamatinib, First Oral SYK Inhibitor for Rheumatoid Arthritis

AstraZeneca announced top-line results for Oral SYK Inhibition in Rheumatoid Arthritis (OSKIRA-1), a Phase 3 study assessing the safety and efficacy of fostamatinib, the first oral spleen tyrosine kinase (SYK) inhibitor in development for rheumatoid arthritis (RA).

OSKIRA-1 randomized 923 patients who had experienced an inadequate response to methotrexate (MTX). Patients were evaluated over a 24-week period for the effectiveness of two dosing regimens of fostamatinib (100mg twice daily or fostamatinib 100mg twice daily for four weeks followed by 150mg once daily) in combination with MTX vs. placebo in combination with MTX. Patients on fostamatinib remained on treatment in OSKIRA-1 for 12 months. The study’s two primary endpoints were assessing signs and symptoms of RA as measured by ACR20 response rates, and an X-ray endpoint known as mTSS (modified Total Sharp Score).

Fostamatinib achieved a statistically significant improvement in ACR20 response rate at 24 weeks in both the 100mg twice daily group and the group that received 100mg twice daily for four weeks followed by 150mg once daily (49%, P<0.001 and 44%, P=0.006 respectively) compared to placebo (34%). Fostamatinib did not demonstrate a statistically significant difference in mTSS compared to placebo at 24 weeks for either dose.

The ongoing OSKIRA program will investigate fostamatinib as a potential new oral treatment option for rheumatoid arthritis and an alternative to injectable therapies for patients with an inadequate response to conventional Disease Modifying Anti-Rheumatic Drugs (DMARDs), including methotrexate (OSKIRA-1 and OSKIRA-2) and those with an inadequate response to TNF-α antagonists (OSKIRA-3). The OSKIRA-2 and OSKIRA-3 results are expected later in the second quarter of 2013.

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