Announcing top-line results today from two Phase III clinical trials investigating fostamatinib, a spleen tyrosine kinase inhibitor developed as an oral treatment for rheumatoid arthritis, AstraZeneca said it has decided not to proceed with regulatory filings for the candidate.
For the first study, OSKIRA-2, evaluating patients who showed inadequate response to disease modifying anti-rheumatic drugs (DMARDs), AstraZeneca found that fostamatinib in combination with DMARDs showed statistically significant improvements in ACR20 response rates at 24 weeks in two groups—a 100mg twice daily group, and another receiving 100mg twice daily for four weeks followed by 150mg once daily—compared to placebo.
And for OSKIRA-3, evaluating patients who showed inadequate response to methotrexate (MTX) and a single TNF-alpha antagonist, the company found that fostamatinib in combination with MTX showed statistically significant improvements in ACR20 response rates at 24 weeks in the 100mg twice daily group, though not for the group given 100mg twice daily for four weeks followed by 150mg once daily, compared to placebo.
While AstraZeneca found fostamatinib safe and tolerable in both trials, the company said that based on the totality of results from the OSKIRA Phase III program—including the data previously reported from OSKIRA-1—it will not proceed with regulatory filings, and instead will return the rights to the compound to developer Rigel Pharmaceuticals.
In a statement, Briggs Morrison, M.D., evp Global Medicines Development and CMO, AstraZeneca, said: “The results of the late stage trials did not measure up to the promising results we saw earlier in development.” He added that his firm remains “committed to the search for new treatments for patients with rheumatic and inflammatory diseases,” noting that it has Phase II compounds in development for such.