Fostamatinib Improves Signs and Symptoms of Rheumatoid Arthritis

The main objective of the researchers was to study the effectiveness and long-term safety of fostamatinib in patients with active rheumatoid arthritis despite MTX treatment.

Treatment with spleen tyrosine kinase inhibitor fostamatinib was associated with significant improvements in signs and symptoms of rheumatoid arthritis (RA), according to a study in Rheumatology.

In the 12-week OSKIRA-Asia-1 study, patients with RA were randomly assigned to either placebo (n=33) or twice-daily 100 mg fostamatinib (n=31), twice-daily 100 mg fostamatinib every 4 weeks followed by 150 mg fostamatinib once daily (n=33), twice-daily 75 mg fostamatinib (n=33), or twice-daily 50 mg fostamatinib (n=33). Another long-term extension study, OSKIRA-Asia-1X, included 115 patients who received once-daily 100 mg fostamatinib.

Researchers evaluated post-treatment RA signs and symptoms using the ACR response criteria as well as DAS based on a 28-joint count. In addition, the investigators assessed physical function status using the HAQ–Disability Index. Safety was also assessed in the patient in the OSKIRA-Asia-1 and OSKIRA-Asia-1X studies.

In the OSKIRA-Asia-1 study, treatment with fostamatinib was associated with numerical improvements in ACR 20% response (ACR20) at 12 weeks in patients who received 100 mg (P =.059) and 100 mg followed by 150 mg (P =.054) compared with patients who received placebo.

Additionally, the researchers found statistically significant improvement with fostamatinib vs placebo for 100 mg fostamatinib and 100 mg followed by 150 mg fostamatinib in ACR20 at week 8 (60.0% [P =.006] and 58.6% [P =.019] vs 31.0%, respectively), ACR50 at week 8 (26.7% [P =.025] and 34.5% [P =.006] vs 10.3%), and ACR70 at week 12 (11.5% [P =.028] and 13.8% [P =.021] vs 0.0%).

Treatment with fostamatinib at either 100 mg or 100 mg followed by 150 mg was also associated with a greater proportion of patients achieving low disease activity (DAS28-CRP ≤3.2) at week 12 compared with placebo (34.6% [P =.033] and 34.5% [P =.033] vs 10.7%, respectively). Common adverse events with treatment were hypertension, diarrhea, and neutropenia. The most common adverse events in OSKIRA-Asia-1X included nasopharyngitis, hypertension, RA, and neutropenia.

A limitation of the OSKIRA-Asia-1 and OSKIRA-Asia-1X studies included their early termination, which led to a limited number of participants in the final population.

Disclosure: This clinical trial was supported by AstraZeneca. Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Tanaka Y, Millson D, Iwata S, Nakayamada S. Safety and efficacy of fostamatinib in rheumatoid arthritis patients with an inadequate response to methotrexate in phase II OSKIRA-ASIA-1 and OSKIRA-ASIA-1X study. Rheumatology. Published online November 30, 2020. doi:10.1093/rheumatology/keaa732