Roche's Actemra has been given its first green light, gaining marketing approval in Japan for the treatment of rheumatoid arthritis.

Actemra (tocilizumab) is the first in a new class of drugs to treat rheumatoid arthritis. A humanised interleukin-6 (IL-6) receptor-inhibiting monoclonal antibody, the drug works by suppressing the activity of IL-6, an important trigger of the inflammatory process.

Trials in Japan (conducted by Roche's subsidiary Chugai) show Actemra reduces inflammation of the joints and controls the symptoms and progression of the disease.

Analysts at Lehman Brothers have forecast peak annual sales of more than $1 billion, but Actemra is entering an already crowded and competitive field.

Wyeth's Enbrel, Schering-Plough's Remicade and Abbott's Humira are all well-established blockbuster drugs, and are on their way to becoming the standard treatments for the disease.

These drugs are all in the TNF (tumour necrosis factor) blocker class, and are more effective and have fewer side-effects than the existing standard treatments, disease modifying drugs such as methotrexate.

But the TNFs do not work for all patients, with around a third of patients failing to respond to them.  Resistance to the TNFs is also regularly seen, meaning that some patients must be given higher doses to maintain their response.

Roche hope that Actemra could overcome these problems and present an alternative to the TNF drugs.

"Today's approval represents a significant milestone for rheumatologists and patients in Japan," said William Burns, chief executive of Roche's pharmaceuticals division. "The Japanese authorities have recognised that Actemra is a breakthrough drug which addresses an unmet medical need for patients suffering from the debilitating effects of this disease."

Actemra is awaiting approval in the US and Europe. Roche's cancer drug MabThera won a similar RA licence in Europe two years ago, although it is used only in the severe stage of the condition.

In addition to being indicated for RA, Actemra has also been approved in Japan for two forms of the disease that affect children - juvenile idiopathic arthritis and systemic-onset juvenile idiopathic arthritis.

Enbrel, Remicade and Humira have all expanded their uses from RA to other autoimmune diseases and since 2005, Actemra has been marketed in Japan for the treatment of patients with a rare auto-immume condition called Castlemans disease.

The last of five phase III trials to evaluate clinical findings of Actemra is underway. The two-year study called LITHE (Tocilizumab safety and the prevention of structural joint damage) is expected to report preliminary first-year data this year.

pharmafocus@wiley.co.uk