This is the second article in a two-part series to bring us up-to-date on psoriatic arthritis (PsA). The first part focused on the diagnosis of this condition using biomarkers and advanced imaging studies. In this second half, the use of medications to treat the problem is highlighted.
Psoriasis is a disease that most people think of as primarily a skin disease because the condition causes a persistent rash in various areas of the body. Psoriatic arthritis is a type of joint disease that occurs in roughly seven percent of people who have psoriasis.
Psoriatic arthritis affects people of all ages, but most get it between the ages of 30 and 50. Usually a patient has psoriasis (the skin rash) for many years before the arthritis develops, and the arthritis comes on slowly. Patients with psoriatic arthritis must manage both the outbreaks of itchy, scaly skin and the pain and stiffness of arthritis.
One of the most commonly used medications for the treatment of psoriatic arthritis (PsA) is a disease-modifying antirheumatic drug (DMARD) called methotrexate. DMARDs like methotrexate not only control symptoms, they also slow the progression of disease. That’s what makes them “disease-modifying”.
Methotrexate may not be as effective with psoriatic arthritis as it is for patients with rheumatoid arthritis but without the psoriasis. Some patients don’t respond at all while others have an adverse reaction to the medication. And in some cases, it may be necessary to combine methotrexate with another drug (e.g., infliximab) to get the desired results (decreased joint pain, swelling, and stiffness).
Infliximab is a type of disease-modifying medication in a class called anti-tumor necrosis factor (TNF) agents. The anti-TNF agents are a special type of antibody referred to as human monoclonal antibodies. They specifically target (and inhibit) tumor necrosis factor.
Tumor necrosis factor (TNF) promotes the inflammatory response, which in turn causes many of the clinical problems associated with autoimmune disorders such as rheumatoid arthritis. Golimumab is another new TNF-inhibitor that has been approved by the FDA for use with patients who have active moderate-to-severe psoriatic arthritis (PsA).
Not everyone with psoriatic arthritis (PsA) responds well to TNF inhibitors (and not everyone can afford them). What can be done for these patients? Well, that’s a problem scientists are trying to solve. Right now, there aren’t very many options left for these patients.
Oral medications (pills taken by mouth) under investigation that might be available in the future for the treatment of psoriatic arthritis include ustekinumab, apremilast, and tofacitinib. Each of these medications works in a slightly different way to regulate the immune system.
Ustekinumab (Stelara, Centocor) is a human monoclonal antibody. It is directed against two specific interleukins (interleukin 12 and 23). Interleukins are naturally occurring proteins that regulate the immune system and inflammatory disorders like rheumatoid arthritis. In Phase III trials for moderate-to-severe psoriasis, ustekinumab was safe and effective, especially for patients who failed to respond to other standard medications.
Apremilast works as an anti-inflammatory by suppressing more than one pro-inflammatory cells including, TNF-alpha, interleukins 6, 17 & 23, and interferon-gamma (among others). It is currently in Phase III clinical trials for the treatment of psoriasis, psoriatic arthritis, and other chronic inflammatory diseases. Early stage studies found this medication to be safe and well-tolerated with few side effects.
Tofacitinib inhibits Janus kinase, an enzyme that acts as a special signaling messenger in the immune system. Tofacitinib is currently in phase two trials with psoriasis and will be tested next with psoriatic arthritis. Tests are scheduled to run until January 2015. So it may be a while before we see this one on the market for psoriatic arthritis.
In summary, the use of disease-modifying antirheumatic drugs (DMARDs) has changed the quality of life for many patients suffering from the effects of psoriatic arthritis. For those individuals who do not do well with these drugs, there aren’t very many other choices. But scientists point to a “therapeutic pipeline” of drugs that may be available in the near future.