A study depicted that in rheumatoid arthritis patients, fostamatinib attained clinically and statistically significant improvements in signs and symptoms. The tolerability and safety of fostamatinib (plus methotrexate) displayed consistency with the prior studies.

Two phase II studies were carried out to investigate the efficacy (OSKIRA-Asia-1) and long-term safety/tolerability (OSKIRA-Asia-1X) of fostamatinib in patients from Asia with active rheumatoid arthritis despite methotrexate treatment.

OSKIRA-Asia-1 was a multicentre, placebo-controlled, double-blind, 12-week, parallel-group trial. Participants were randomly assigned to receive one of four fostamatinib doses: Groups A (n=31), Group B (n=33), Group C (n=33), Group D (n=33) and placebo (Group E, n = 33). OSKIRA-Asia-1X trial was a long-term extension trial (100 mg fostamatinib once per day) of participants who completed OSKIRA-Asia-1 analysis.

The signs and symptoms of rheumatoid arthritis were estimated by the American College of Rheumatology (ACR) response criteria and Disease Activity Score (DAS) based on a 28-joint count. Physical function status was determined with the health assessment questionnaire (HAQ)–Disability Index. The safety findings were examined.

In the efficacy trial, fostamatinib displayed numerical improvements in ACR 20% response (ACR20) at week 12 in group A (100 mg twice daily) and group B (100 mg twice daily, then 150 mg once per day) when compared to placebo. Both the groups illustrated substantial improvements in ACR20 and ACR50 at week 8 and in ACR70 at week 12, and in low disease activity (defined as DAS based on a 28-joint count ≤3.2 based on C-reactive protein).

In group A, improvement in physical function was found to be numerically greater. Hypertension, neutropenia, and diarrhoea were the most commonly occurring adverse events. In OSKIRA-Asia-1X, the most usual noxious events were hypertension, rheumatoid arthritis, nasopharyngitis, and neutropenia. Thus, fostamatinib appears to be a promising agent to treat rheumatoid arthritis.