Mixed Results Reported for Arthritis Drug Fostamatinib, Regulatory Filing Scrapped
First STK inhibitor completes phase III program (May 4)
Mixed results have been announced from OSKIRA-2 and OSKIRA-3, the remaining pivotal phase III trials investigating fostamatinib (AstraZeneca), the first oral spleen tyrosine kinase (STK) inhibitor in development as an oral treatment for rheumatoid arthritis (RA).
The OSKIRA-2 study involved patients who had shown an inadequate response to disease-modifying antirheumatic drugs (DMARDs). Fostamatinib in combination with DMARDs showed statistically significant improvements in the number of tender and swollen joints (ACR20 response rates) at 24 weeks in both the 100 mg twice-daily group and the group receiving 100 mg twice daily for 4 weeks followed by 150 mg once daily (39.6% in both arms; P < 0.001) compared with placebo (24.5%).
The OSKIRA-3 study involved patients with an inadequate response to methotrexate (MTX) and a single tumor necrosis factor (TNF)-alpha antagonist. Fostamatinib in combination with MTX showed statistically significant improvements in ACR20 response rates at 24 weeks in the group given 100 mg twice daily (36.2%; P = 0.004) but not in the group given fostamatinib 100 mg twice daily for 4 weeks followed by 150 mg once daily (27.8%; P = 0.168) compared with placebo (21.1%).
The most commonly reported adverse events in the OSKIRA program included hypertension, diarrhea, nausea, headache, and nasopharyngitis.
Based on the totality of the results from the OSKIRA phase III program, including data previously reported from OSKIRA-1, the drug’s developer (AstraZeneca) has decided not to proceed with regulatory filings for fostamatinib.
Source: AstraZeneca; June 4, 2013.