The National Institute for Health and Clinical Excellence (NICE) recommended yesterday that Tysabri (natalizumab) be made available on the National Health Service (NHS) for patients with rapidly evolving severe (RES) relapsing-remitting forms of MS. The monoclonal antibody (mAb), made by Elan Corp and Biogen Idec, is the first in a new class of drugs called selective adhesion molecule (SAM) inhibitors and is also the first mAb to be licensed for MS - it has been on the market in Europe and the US since 2006. In MS, immune cells pass through the blood-brain barrier into the central nervous system (CNS) and cause inflammation and damage to nerves and their protective casing (myelin sheath). Tysabri works by attaching to a specific adhesion molecule (alpha-4 integrin) on the surface of these immune cells and in doing so prevents their passage through the blood-brain barrier. Yesterday NICE also published its final recommendation on Roche's rheumatoid arthritis (RA) treatment Mabthera (rituximab), stating that it can be used in combination with methotrexate in those with severe, active RA. However, patients must have had an inadequate response to or intolerance of other antirheumatic drugs, include treatment with at least one tumour necrosis factor (TNF) inhibitor therapy, and Mabthera treatment should only be continued should it elicit an initial response in these patients, the regulator added. RA is a chronic condition characterised by inflammation of the synovial tissue of the joints, causing pain, swelling and stiffness and progressive joint destruction. It affects 400,000 people in the UK, 15 per cent of whom have the severe form of the disease that the NICE ruling refers to. Mabthera is a mAb that selectively targets a subset of B cells that express CD20, and play a key role in the autoimmune process of RA. MabThera interrupt this process by inhibiting a series of reactions inflaming the synovia and leading to cartilage loss and bone erosion. The drug has been available in the EU since 2004 and in the US since 2002 in non-Hodgkin's lymphoma (NHL) indications and in 2006, Roche also received marketing approval in the EU and in the US for indications in arthritis. Meanwhile, the funding watchdog also issued its final guidance on another mAb, Abbott's Humira (adalimumab) for psoriatic arthritis. NICE recommended the drug's availability for patients with active and progressive psoriatic arthritis when the person has peripheral arthritis with three or more tender joints and three or more swollen joints, and the psoriatic arthritis has not responded to adequate trials of at least two standard disease-modifying anti-rheumatic drugs. It should be withdrawn if no adequate response is shown after 12 weeks, said NICE. Humira binds to TNF-alpha, a cytokine produced by white blood cells inside the joint which plays an important role in stimulating joint inflammation. Adalimumab binds to TNF-alpha and neutralises its inflammatory ability. Psoriatic arthritis (psoriatic arthropathy) is an inflammatory joint disease closely associated with the skin disease psoriasis, affecting 5-7 per cent of sufferers.