Xeljanz (tofacitinib) is an investigational therapy that has shown promise in clinical trials to treat inflammatory bowel disease (IBD), and being developed by Pfizer. It has been tested for ulcerative colitis (UC) and Crohn’s disease (CD), both forms of IBD, with more success in UC so far.

The drug is approved by the U.S. Food and Drug Administration (FDA) to treat rheumatoid arthritis.

How Xeljanz works

In IBD, an abnormally strong immune reaction in the gastrointestinal (GI) tract (digestive system) results in inflammation and swelling, which can lead to problems such as blockages and ulcers.

Xeljanz is a Janus kinase (JAK) inhibitor. The JAK family of proteins are enzymes, or proteins that catalyze specific chemical reactions, that affect the immune system. Specifically, these enzymes send chemical messages to start producing proteins that can trigger an inflammatory response.

It acts by blocking JAK from sending these signals so to lessen the inflammatory response, a process that could relieve IBD symptoms and allow the GI tract to heal.

Xeljanz in clinical trials

Pfizer conducted three key clinical studies, under the OCTAVE Clinical Development Program, assessing Xeljanz as a therapy for IBD. The company announced that the results of the trials in ulcerative colitis patients were published in The New England Journal of Medicine.

The Phase 3 OCTAVE Induction 1 study (NCT01465763) was a multi-center, randomized, double-blind, and placebo-controlled trial tested the response of UC patients to a 10 mg dose, twice daily, over an eight-week period. At week 8, significantly more patients in the Xeljanz-treated group were in remission compared to those in the placebo group (18.5 percent versus 8.2 percent, respectively). Furthermore,  31.3 percent of Xeljanz-treated patients had evidence of mucosal healing, compared to 15.6 percent of placebo-treated patients.

The Phase 3 OCTAVE Induction 2 study (NCT01458951) was similarly successful. Remission was achieved in 16.6 percent of Xeljanz-treated patients, compared to only 3.4 percent of those given placebo. Mucosal healing was achieved in 31.3 percent of Xeljanz-treated and 15.6 percent of placebo-treated patients.

The third clinical trial, OCTAVE Sustain (NCT01458574) aimed to assess it as a maintenance therapy, and enrolled UC patients who had successfully completed a previous OCTAVE study with a positive clinical response. This multi-center, randomized, double-blind, and placebo-controlled trial tested patient response to either a 5 mg or 10 mg dose of Xeljanz, twice daily, over a 52-week period compared to a placebo. The results suggested that Xeljanz is effective as a maintenance therapy, as 34.3 percent and 40.6 percent of participants treated with 5 mg and 10 mg of Xeljanz, respectively, went into remission compared to 11.1 percent in the placebo-treated group.

Xeljanz is currently not approved by the FDA for the treatment of IBD.

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