Roche has presented yet more positive data from the third late-stage study of its experimental compound for rheumatoid arthritis, Actemra.

The 498-patient RADIATE study, the third out of five Phase III international trials investigating Actemra (tocilizumab), examined the drug in combination with methotrexate in RA patients who had an inadequate response to anti-tumour necrosis factor therapy. It showed that a greater proportion of difficult-to-treat patients treated with Actemra plus methotrexate, achieved a significant improvement in disease signs and symptoms following 24 weeks of treatment, compared to those on placebo plus methotrexate.

Actemra was developed by Roche’s majority-owned Japanese partner Chugai, is a humanised monoclonal antibody that blocks the activity of interleukin-6 and therefore targets a new mechanism of action compared to the anti-TNF therapies for RA – Abbott Laboratories’ Humira (adalimumab), Johnson & Johnson/Schering-Plough’s Remicade (infliximab) and Wyeth/Amgen’s Enbrel (etanercept). Chugai already sells the drug in Japan for Castleman’s disease, a rare immune disorder, and it was filed there in April 2006 for RA and systemic-onset juvenile idiopathic arthritis.

Urs Schleuniger, head of inflammation and autoimmune disease for Roche, said that “RADIATE’s positive outcome further confirms the critical role of IL-6 in the pathophysiology of RA and the results “add to the wealth of data being compiled ahead of the anticipated regulatory filing later this year”.

The Swiss drugs major noted that it has two further studies on Actemra underway, one of which is scheduled to report later this year, following the OPTION study which showed that treatment with Actemra plus methotrexate resulted in a rapid and significant improvement of RA signs and symptoms in patients who had an inadequate response to methotrexate. Earlier, the TOWARD trial successfully demonstrated Actemra’s efficacy in patients who had an inadequate response to traditional disease-modifying drugs.

Analysts estimate that Actemra could have peak annual sales of up to 2 billion Swiss francs, around £820 million.