July 18, 2025
A new peer-reviewed study published in Arthritis & Rheumatology suggests that ivarmacitinib, a new medication known as a selective JAK1 inhibitor, may be a promising treatment for people with active ankylosing spondylitis (AS).
The study was a randomized, double-blind clinical trial. This means participants were randomly assigned to different treatment groups, and neither they nor the researchers knew who was receiving the actual drug versus a placebo, which helps ensure unbiased results.
In the first part of the study, participants were split into four groups. Three of those groups received ivarmacitinib at daily doses of either 2 mg, 4 mg, or 8 mg, while the fourth group received a placebo. After 12 weeks, researchers selected the 4 mg dose as the most suitable to move forward.
In the next part of the study, new participants were given either ivarmacitinib 4 mg or a placebo daily for another 12 weeks. After that, for the remainder of the trial (weeks 25 to 36), all participants received the 4 mg dose of ivarmacitinib.
In total, 504 people took part in the study. At week 12, 48.7% of those taking ivarmacitinib 4 mg experienced at least a 20% improvement in symptoms, compared to 29.0% of those on the placebo. A higher level of symptom improvement (ASAS40) was seen in 32.1% of ivarmacitinib patients versus 18.3% of those on placebo. The positive effects continued through 24 weeks of treatment.
Mild to moderate side effects were reported in 79.7% of people taking ivarmacitinib and 65.6% of those taking the placebo (e.g., upper respiratory infections, headache, digestive symptoms) but the safety profile was considered tolerable by the researchers.
The study concluded that ivarmacitinib 4 mg significantly improved the signs and symptoms of active ankylosing spondylitis and maintained those improvements over time. The researchers recommend it as a potential new treatment option.
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