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Stanford University School of Medicine

Drug for psoriatic arthritis shows promise in large late-stage clinical trial

One in every 200 people in the developed world suffer from an inflammatory autoimmune condition called psoriatic arthritis. For too many of these people, standard drugs don't work well or stop working well after initial success. But a new study published in The Lancet suggests that relief may be on the way.

While superficially similar in several respects to the more common  rheumatoid arthritis -- the latter, too is an autoimmune disorder, and both involve stiffness, pain, and swelling of several joints -- the psoriatic variety is distinguished from its rheumatoid lookalike by a number of features. Importantly, psoriatic arthritis is associated with (and usually, but not always, preceded by) the appearance of the scaly rash known as psoriasis.

The underlying molecular mechanisms driving the two kindred diseases also differ, and, as a result, the medications that usually work quite well for rheumatoid arthritis don't work quite so well for psoriatic arthritis. The standard of care for both is a class of injectable biologic drugs that inhibit a pro-inflammatory substance called TNF, which is secreted by some immune cells. TNF is very good at stimulating an immune response to infections, but in overdrive it can spur autoimmunity.

TNF inhibitors account for three of the top eight best-selling drugs in the United States by dollar value -- and for a good reason. Something like 80-85 percent of rheumatoid arthritis patients get lasting relief from them. But only about half of psoriatic arthritis patients who are given these drugs get better.

In the Lancet study, Stanford arthritis investigator Mark Genovese, MD, and colleagues at numerous institutions summarize a late-stage randomized, placebo-control clinical trial in which an injectable biologic drug  works in a different way from TNF inhibitors was given to psoriatic-arthritis patients for whom TNF inhibitors had either stopped working or never did much good in the first place.

In the trial, which was carried out in 109 medical centers in 10 countries, patients who received injections of the actual drug -- whose generic name is ixekizumab -- did substantially better than those whose injections contained only inert substances. As I wrote in our news release about the study:

Over the 24-week duration of the ... trial, 109 participants received ixekizumab every two weeks; 94 received placebo injections every two weeks; and 111 alternated every two weeks between getting injections of ixekizumab and the placebo. While 19.5 percent of patients who received only the placebo injections were judged to have met the trial’s specified clinical endpoint — at least a 20 percent reduction in the number of tender and swollen joints — the response rate among those getting the real drug every four weeks was 53.3 percent.

Ixekizumab is already approved by the U.S. Food and Drug Administration for psoriasis, so it's commercially available. Its manufacturer, Eli Lilly & Co., has filed for FDA approval of the drug for psoriatic arthritis as well.

Previously: Promising new path for refractory rheumatoid arthritis patients?, Unraveling the mechanisms of psoriasis may lead to new treatment, say Stanford researchers and Is osteoarthritis an inflammatory disorder? New thinking gets clinical test
Photo by Global Panorama

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