Radiographic results have shown that Enbrel (etanercept), a rheumatoid and psoriatic arthritis drug, significantly inhibits the progression of joint destruction, joint-space narrowing, and bone erosion associated with psoriatic arthritis. A group of University of Washington researchers presented their results from the phase III, one-year extension study at the 2002 American College of Rheumatology meeting in New Orleans.
A chronic inflammatory disease of the joints and connective tissue, psoriatic arthritis causes joint pain and swelling that can lead to crippling debilitation, accompanied by inflamed and irritated scaly red patches of skin. There are approximately 450,000 patients with psoriatic arthritis in the U.S., and the disease affects both men and women, most commonly between the ages 30 and 50. Etanercept received FDA approval for psoriatic arthritis in January 2002, and is the only approved drug treatment for the condition.
"Even though patients' symptoms have been shown to improve following treatment with DMARDs (disease-modifying anti-rheumatic drugs), they still would exhibit progression in joint damage," said lead investigator Dr. Peter Ory from the department of radiology, University of Washington Medical School in Seattle. "This is the first study to show that we can reduce signs and symptoms, and inhibit the progression of bone erosions and joint-space narrowing associated with psoriatic arthritis, a disease which has unique and distinct radiographic features not seen in rheumatoid arthritis."
The investigators initially enrolled 205 subjects with psoriatic arthritis in a 24-week, double-blind study of etanercept and a placebo. The results of that study, which concluded that etanercept was safe and effective, were presented at the 2001 American College of Rheumatology meeting in San Francisco.
The 205 subjects were then given the opportunity to enroll directly into a one-year extension. In this study, the investigators made a comparison of collected radiographic progression images from patients treated with etanercept versus placebo. They evaluated images of hands and wrists at baseline of the original blinded study, at 24 weeks, at initiation of open-label treatment, at one year from original baseline, and at early termination during either part of the study.
"Investigators analyzed digitized x-rays of the hands, which were read on high-resolution monitors," Ory said. Readers who were blinded to the results scored the images for erosions and joint-space narrowing using a modified Sharp method, which uses a 4-point scale to rate joints according to the severity of erosions and degree of joint-space narrowing. The erosion and joint space-narrowing subscores were then added to obtain a total radiographic score. The researchers also evaluated images of distal interphalangeal joints.
The investigators found significantly less radiographic progression in the etanercept group than in the placebo group. At one year, there was inhibition of radiographic progression in the etanercept group (n=101) as compared with the placebo group (n=104).
The mean change from baseline in total Sharp score was a reduction in progression of -0.02 units in the etanercept group versus an increase in progression of +1.03 units in the placebo group (p=0.0001).
Progression of structural damage was inhibited when measured not only by the total Sharp score, but also by joint erosion scores and joint space narrowing scores. The total mean rate of change in erosion scores was -0.08 units/year for etanercept versus +0.69 units/year for placebo (p < 0.0001). Likewise, for joint-space narrowing the total mean rate of change was +0.06 units/year for etanercept versus +0.35 units/year in placebo patients (p = 0.04).
"Patients with psoriatic arthritis often exhibit the painful bone and joint destruction and eventual deformities to fingers, hands, and wrists which are associated with disability in this disease," Ory said. "This is the first study to show that an available treatment for psoriatic arthritis can dramatically inhibit the progression of this terrible condition. This is a breakthrough for us as clinicians, and, most importantly, for our patients."
Etanercept is the only tumor necrosis-factor inhibitor that can be used as monotherapy (without methotrexate) and the only biologic-response modifier approved for use as a first-line monotherapy for rheumatoid arthritis.
By Bruce SylvesterAuntMinnie.com contributing writer
November 15, 2002
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