Xeljanz (tofacitinib citrate) is a small-molecule therapy marketed by Pfizer. It is already approved by the U.S. Food and Drug Administration (FDA) for the treatment of rheumatoid arthritis (RA). Pfizer is now sponsoring studies to evaluate the safety and efficacy of Xeljanz in patients with ankylosing spondylitis (AS). Both RA and AS are diseases caused by inflammation in joints.

How Xeljanz works

A healthy immune system defends the body against harmful invaders and helps begin the repair of damaged tissue. Inflammatory mediators are proteins that send signals to immune cells to recruit them to the site of infection or injury. In diseases such as RA and AS, the inflammatory mediators recruit too many immune cells and end up damaging joint tissue.

Xeljanz improves signs and symptoms of inflammatory joint diseases by fighting inflammation itself. The therapy is called a JAK inhibitor because it blocks the production of Janus kinase (JAK) inside cells. JAK is an enzyme that plays an important role in the activation of various inflammatory mediators. Inhibiting JAK reduces inflammation because it disrupts inflammatory signaling pathways.

Xeljanz in clinical trials for AS

Many studies have already shown that Xeljanz is a safe and effective treatment for people with RA, but fewer studies have explored its potential to decrease inflammation in AS. The results of a Phase 2 clinical trial (NCT01786668) in people with AS were published in the August 2017 issue of Annals of the Rheumatic Diseases.

The trial compared the effectiveness and safety of three different doses of Xeljanz with a placebo. All participants had active disease and met the criteria for AS diagnosis. Participants in the treatment group received either 2 mg, 5 mg, or 10 mg of Xeljanz twice a day for 12 weeks. This was followed by a four-week follow-up period with no treatment.

Investigators found that both the 5 mg and 10 mg dose (twice daily) of Xeljanz significantly reduced the signs and symptoms of the disease as well spinal inflammation compared to a placebo. The safety profile was about the same as the ones obtained in other Xeljanz studies.

Additional information

Xeljanz can lower immunity, so it can increase the chance of serious infections. It is not recommended for people with liver disease, and it is unknown whether or not it is safe and effective in children. It can be used in combination with some other therapies used to treat inflammatory diseases, such as methotrexate and corticosteroids.

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