Psoriatic arthritis (PsA), an autoimmune disease that attacks both the skin and underlying joints and tissues, can have painful, irritating and damaging results. Like other autoimmune forms of arthritis, such as rheumatoid arthritis, psoriatic arthritis causes inflammation in the joints that can lead to permanent damage if not treated early and aggressively.

In addition to the scaly, itchy, red patches of psoriasis that most people with this condition have, psoriatic arthritis is characterized by symptoms such as badly swollen fingers and toes, pitted nails, pain and inflammation in joints, and fatigue.

Common treatments for psoriatic arthritis include nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids to manage its symptoms while disease-modifying antirheumatic drugs (DMARDs) address the actual causes of inflammation. According to the American College of Rheumatology, the DMARDs most commonly prescribed for psoriatic arthritis are sulfasalazine (Azulfidine), methotrexate (Rheumatrex, Trexall), cyclosporine (Neoral, Sandimmune) and leflunomide (Arava). Azathioprine (Azasan, Imuran) may be prescribed as well.

In the last decade, a group of drugs belonging to a subcategory of DMARDs known as biologic response modifiers, has been approved for psoriatic arthritis. Many of them inhibit production of tumor necrosis factor alpha (TNF-alpha), a protein believed to be involved in the inflammation process, and are showing dramatic results. These include etanercept (Enbrel), infliximab (Remicade) and adalimumab (Humira). These drugs are often used in combination with methotrexate.

Treatments on the Horizon

Now, even more cutting-edge treatments are in the later stages of study and development and approval for psoriatic arthritis. Here’s a brief overview:

Certolizumab pegol (Cimzia): Already approved in the U.S. to treat rheumatoid arthritis and Crohn’s disease (an inflammatory, autoimmune disease affecting the intestines), certolizumab is currently in Phase III studies for psoriatic arthritis. Like the drugs noted above, certolizumab is a TNF inhibitor, meaning it blocks production of TNF-alpha. It's also PEGylated, a process that makes the drug more water soluble, possibly masking it from the body’s immune system, reducing clearance of the drug by the kidneys and perhaps allowing for a reduced dosage. The drug is delivered by intramuscular injection.

Alefacept (Amevive): This fusion protein given as an intramuscular injection or an intravenous infusion blocks T cells (white blood cells) linked to inflammation. The drug is already approved in the United States to treat moderate-to-severe plaque psoriasis in adults who are candidates for phototherapy or systemic drugs. It isn't approved Europe due to safety issues including possible birth defects if used by pregnant women. Alefacept is now being studied in combination with methotrexate for psoriatic arthritis. A 2008 clinical trial showed promising results, and the drug is currently in Phase II trials for psoriatic arthritis patients.

Apremilast: One of a new type of oral medications called Type 4 phosphodiesterase inhibitors, apremilast targets proteins that cause inflammation. It has shown positive results in treating psoriatic arthritis – 20 percent or more of patients in a Phase II study, whose results were released in June 2009, showed improvement in their symptoms, and the drug was reported to be safe and tolerable. Some experts thought the study’s results showed its efficacy to be no better than older, cheaper drugs, but its tolerability might be higher. The results were promising enough to launch a Phase III study, beginning in June 2010, of the drug given at higher doses to determine if it can be more effective while still tolerated safely.

Ustekinumab (Stelara), a drug in the class of human anti-interleukin 12 and anti-interleukin 23 monoclonal antibody, was approved in late 2009 for treatment of moderate-to-severe plaque psoriasis in adults who are candidates for other PsA treatments such as phototherapy (ultraviolet light therapy) or systemic drugs for the disease. Because anti-interleukins inhibit the production of interleukin cytokines, proteins that trigger the inflammatory response, ustekinumab is currently being studied for use in psoriatic arthritis as well. A Phase-II, placebo-controlled trial of people with psoriatic arthritis showed significant results in relieving tender, swollen joints. The drug would be indicated for inhibiting the progression of structural damage to joints, as well as improving physical function in those with the disease.