Rheumatoid arthritis is a type of arthritis in which a misguided immune system mistakenly attacks its own joints and tissues, causing inflammation and painful degeneration. An experimental drug still in the trial stages offers new hope for the 1.3 million Americans impacted by the disease, most of them women.

A large stage three trial of an experimental rheumatoid arthritis medication, tasocitinib, has met two important goals ?the drug provided an improvement in signs and symptoms of the disease in study participants, and it improved their ability to function physically. The study also made some progress towards a third goal ?disease remission.?"When it works, it really works," enthused primary investigator Dr. Roy Fleischmann of the University of Texas Southwestern Medical Center, "This is the first oral medication for rheumatoid arthritis that has had a successful phase three study this century."

The study included 611 patients with active moderate to severe rheumatoid arthritis (RA) who had not experienced relief from existing meds for arthritis.?Two-thirds (66%) of the study participants on a 10 mg dose of tasocitinib reported improvement in disease activity and symptoms after three months, as did 60% of those taking a 5 mg dose, and only 27% of those given a placebo.?Those given either strength dose of tasocitinib also reported twice as much improvement in their ability to perform everyday physical activities such as dressing, washing, walking, reaching and gripping.

Tasocitinib belongs to a new class of immune system suppressing medication called JAK inhibitors.?It takes a different approach to reducing inflammation than existing RA medications, working by blocking a receptor on cells called JAK-3 to interfere with intracellular signaling pathways. The drug's developer, Pfizer, will be completing further studies to measure the new drug's effectiveness against current rheumatoid arthritis medications around mid-2011. Regulatory approval is not expected for another year or two.

Rheumatoid arthritis is one of over 100 types of arthritis, and is typically more painful and disabling than the much more common osteoarthritis. RA is a painful, chronic autoimmune disorder that causes inflammation and swelling of the joints and surrounding tissue. It is progressive, damaging and deforming the joints and increasingly impairing physical functioning and mobility. In severe cases, RA can cause harmful inflammation in other parts of the body, including the lungs, eyes, skin and nerves. Its cause is unknown, but it runs in families and is believed to have a genetic component. RA affects about 1.3 million Americans, and usually strikes people in their 40s and 50s. It is three times more common in women than in men.

Early, intensive treatment with a combination of RA medication offers the best prognosis. First line medications include NSAIDS and corticosteroids. Second line RA medications include immune suppression drugs such as Rheumatrex (generic methotrexate), which can be taken orally or as methtrexate injections. These first and second line drugs often don't provide sufficient relief for moderate to severe RA, in which case the newer injectable biological response modifiers, which target immune triggers, may be added. These injectable medications are expensive, inconvenient, carry the risk of infection, and can worsen other conditions such as MS and congestive heart failure.?About 20 to 40 percent of RA sufferers don't respond to rheumatoid arthritis drugs.

Tasocitinib appears to hold out hope of a breakthrough in terms of a convenient, effective oral medication with fewer side effects than those currently available to RA sufferers. "As with all drugs, we need long-term information on safety," says Dr. Alan Matsumoto of Arthritis and Rheumatism Associates in Washington, DC, "But from both an effectiveness and safety view, tasocitinib looks to be very promising."?Pfizer is also testing tasocitinib's effectiveness in treating psoriasis, inflammatory bowel disease, and in combating rejection in organ transplants.?