In the six month phase IIb study completed by Rigel – known as TASKi2 – 67 per cent of patients taking fostamatinib 100 mg twice daily achieved the primary efficacy endpoint (ACR 20) at six months, and thirty-six per cent of patients achieved an ACR 20 response after just one week.

‘In this study, we saw a significant clinical benefit in this rheumatoid arthritis population and a manageable safety profile,’ said Mark C. Genovese, Division of Rheumatology, Stanford University, Palo Alto, CA. ‘

Based on the data, further study of fostamatinib as an oral agent for the treatment of patients with rheumatoid arthritis is certainly warranted.’

Fostamatinib is the first oral syk inhibitor in development as a novel therapeutic approach for RA. It is thought to reversibly block signalling in multiple cell types involved in inflammation and tissue degradation in RA.

Patients in the study had active RA, despite treatment with methotrexate alone, and were given either fostamatinib 100mg twice daily (bid), fostamatinib 150mg once daily (qd) or placebo. Significant clinical benefits were reported in both fostamatinib groups.

After six months, the ACR 20 response was achieved by significantly (p<0.01) more patients in the bid group and the qd group (67 per cent and 57 per cent, respectively) than in the placebo group (35 per cent).

ACR 50 response rates were 43 per cent, 32 per cent and 19 per cent for the bid group, the qd group and the placebo group, respectively. In addition, the Disease Activity Score 28 remission rate was significantly higher in the bid group and the qd group (31 per cent and 21 per cent, respectively) than in the placebo group (7 per cent).

The published data indicate that the most common drug-related adverse events in the study were diarrhoea, upper respiratory infection and neutropenia.

AstraZeneca plans to commence the phase III clinical trial programme for fostamatinib, OSKIRA (oral syk inhibition in rheumatoid arthritis), shortly.