Phase IIb report of fostamatinib (AstraZeneca) OSKIRA-4 trial for RA

AstraZeneca announced top-line results of OSKIRA-4, a Phase IIb monotherapy study of fostamatinib, the first kinase inhibitor with selectivity for SYK (spleen tyrosine kinase) in development as an oral treatment for rheumatoid arthritis (RA). OSKIRA-4 was a six month study evaluating improvements in signs and symptoms of RA in 280 patients who had never previously used a disease-modifying anti-rheumatic drug (DMARD), were DMARD intolerant or had an inadequate response to DMARDs and were randomised to receive fostamatinib as a monotherapy, adalimumab as a monotherapy, or placebo.

In the OSKIRA-4 study, fostamatinib as a monotherapy met the first primary objective, showing a statistically significant superior DAS28 score change from baseline compared to placebo at 6 weeks at the 100mg twice daily dose and the 100mg twice daily for a month followed by 150mg once daily dose, but not at the 100mg twice daily for a month followed by 100mg once daily dose. The OSKIRA-4 study did not meet its second primary objective as all fostamatinib monotherapy doses were inferior to adalimumab.

This Phase IIb dose finding study was designed to evaluate the effect of fostamatinib independent of methotrexate and to inform the further development of fostamatinib as a monotherapy treatment for RA.

Regulatory filings in the US and EU for use in combination with a DMARD based on the OSKIRA Phase III programme, are expected in the second half of 2013.