A new phase III study finds that abatacept (Orencia) — a medication that disrupts T-cell activity in order to reduce inflammation, which tends to be prescribed after methotrexate fails to work — had a positive impact on patients with psoriatic arthritis, although it wasn’t as successful improving skin conditions.

“Abatacept treatment of PsA in this phase III study achieved its primary endpoint, ACR20 response, showed beneficial trends overall in musculoskeletal manifestations and was well tolerated,” researchers wrote in Annals of the Rheumatic Diseases. “There was only a modest impact on psoriasis lesions.” (ACR20 refers to a 20 percent improvement in the disease.)

(Read more about psoriasis of the skin here.)

Of the 424 psoriatic arthritis patients in the study, 213 received a dose of abatacept while 211 were administered placebo treatments. “Abatacept treatment resulted in a significantly higher proportion of patients achieving an ACR20 response at week 24 versus placebo,” the authors wrote: 39.4 percent for the abatacept takers, and 22.3 percent for the placebo group.

But when it came to improving skin conditions, the abatacept group only outperformed the placebo group 26.7 percent compared to 19.6 percent. It was a “more modest” improvement when compared to the musculoskeletal response, the authors wrote.

Noting the gap between the impact on skin versus the musculoskeletal, the authors added, “The reasons for this are unclear but may include differential dose requirements for optimal efficacy of abatacept in skin versus the joints, for example, due to less efficient drug penetration of skin versus synovial tissue, and distinct pathologies with divergent roles of T cells and T-cell subsets in skin versus synovial inflammation in PsA.”

The study which the researchers relied upon, called Efficacy and Safety of Subcutaneous Abatacept in Adults With Active Psoriatic Arthritis (ASTRAEA), was conducted at 76 centers worldwide in 2013, notes MedPage. It enrolled “adult patients with active arthritis and plaque psoriasis,” MedPage adds. “All had previously had an inadequate response to one or more non-biologic disease-modifying anti-rheumatic drugs (DMARDs), and approximately 60 percent had already been treated with a tumor necrosis factor (TNF) inhibitor.”

(Click here to read a Q&A from the Mayo Clinic about adjusting psoriatic arthritis medications.)

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