The results are being presented today at ACR Convergence 2020, in a session titled “Tofacitinib for the Treatment of Adult Patients with Ankylosing Spondylitis: Primary Analysis of a Phase 3, Randomized, Double-blind, Placebo-controlled Study.”
“We are proud to share these positive results from our Phase 3 investigational study for tofacitinib [Xeljanz] in adults with ankylosing spondylitis, and we believe they demonstrate Pfizer’s commitment to addressing unmet needs for those living with inflammatory conditions,” Michael Corbo, PhD, chief development officer of inflammation and immunology at Pfizer Global Product Development, said in a press release.
Pfizer’s Xeljanz is a small molecule that targets Janus kinase (JAK), a protein that plays a central role in sending pro-inflammatory signals. By blocking JAK, Xeljanz is intended to ease inflammation and associated symptoms.
Currently, the treatment is approved by the U.S. Food and Drug Administration (FDA) to treat adults with active rheumatoid arthritis, ulcerative colitis, or active psoriatic arthritis, as well as patients, 2 and older, with active polyarticular juvenile idiopathic arthritis — all of which, like AS, are driven by inflammation.
Pfizer sponsored an international Phase 3 clinical trial (NCT03502616) that enrolled 269 adults with active AS who had not responded or been intolerant to standard treatment with two or more nonsteroidal anti-inflammatory drugs. Participants were given either Xeljanz (5 mg twice daily) or a placebo for 16 weeks, or nearly four months. Mean age was 42.2 in the Xeljanz group and 40 in patients receiving a placebo.
The researchers assessed efficacy using the Assessment of SpondyloArthritis International Society (ASAS) criteria, which analyzes pain, function, inflammation, and a patient global assessment. The study’s primary efficacy measurement was the number of participants who experienced at least a 20% improvement, or reduction, in this score (ASAS20). As secondary goals, the team analyzed the number of participants who experienced a 40% improvement (ASAS40), as well as changes in both ASAS20 and ASAS40 responses over time.
After 16 weeks, significantly more participants given Xeljanz than placebo experienced ASAS20 (56.4% vs. 29.4%) and ASAS40 (40.6% vs. 12.5%). Such benefits were seen from week two in ASAS20 and week 4 in ASAS40. Compared to the placebo, Xeljanz also resulted in significant reductions in the levels of inflammatory markers.
“[Patients] with active AS had a rapid clinical response to tofacitinib [Xeljanz],” the researchers wrote.
About half of the participants in both groups reported adverse events; the most common were upper respiratory tract infection, nasopharyngitis (the common cold), diarrhea, joint stiffness, joint pain, headache, and increases in alanine aminotransferase, a marker of liver damage. Serious and severe adverse events were each reported in two participants given Xeljanz after 16 weeks. Three patients had stop treatment with Xeljanz due to side effects.
Safety trends were similar throughout the subsequent 32 weeks, in which all patients were treated with Xeljanz.
The FDA is currently reviewing an application seeking approval of Xeljanz for people with AS. A decision is expected by mid-2021.
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