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In some cases, the improvements lasted up to six months after just one injection, researchers report.
"The studies that we carried out clearly showed that the drug worked, and worked very effectively," said study author Dr. Gerald G. Krueger, the Benning presidential endowed chair in the department of dermatology at the University of Utah. "I think this is going to be a very effective treatment if what we see in the phase 3 trial is similar to what we saw in this phase 2 trial. And there's no reason to believe it won't be."
The new study was instrumental in moving research forward to the phase 3 trial currently being conducted, Krueger added. That trial will provide more safety and efficacy data, probably in 2008.
"We still need to see the results of the phase 3 trial and some long-term safety data because it is a new drug, but patients in the trial have seen miraculous results," added Liz Horn, director of research at the National Psoriasis Foundation. "Some have had one injection and have stayed clear for quite a long time."
Psoriasis affects between 2 percent and 2.6 percent of Americans, or between 5.8 million and 7.5 million people. The disease occurs when the body suddenly begins overproducing skin cells. The cells pile up on the surface of the skin before they have a chance to mature, creating bright red patches covered with silvery scales.
These patches of skin cause itching, burning and stinging sensations. They most often occur on the elbows, knees, other parts of the legs, scalp, lower back, face, palms and soles of the feet. But they can occur on skin anywhere on the body, according to the U.S. National Institutes of Health.
Doctors believe the disease is linked to the immune system and is genetic in nature. But no one is certain why some people suffer from psoriasis while others do not, or what causes the disease to first start and then spread.
There is a widely recognized need for new treatments.
The new study, published in the Feb. 8 issue of the New England Journal of Medicine, involved 320 people with moderate-to-severe psoriasis who were randomly chosen to receive the interleukin-12/23 monoclonal antibody at different doses and schedules, or a placebo. The study was sponsored by pharmaceutical company Centocor, which makes the drug.
There was a 75 percent or more improvement in 52 percent of participants who received one 45-milligram (mg) dose of the monoclonal antibody, in 59 percent of those receiving one 90 mg dose, in 67 percent of those receiving a 45 mg dose four times weekly, and in 81 percent of those receiving four weekly 90-mg doses.
There was at least a 90 percent improvement in 23 percent, 30 percent, 44 percent and 52 percent, respectively, of patients receiving the monoclonal antibody.
Only 2 percent of those receiving the placebo experienced this type of recovery.
Some 79 percent of the interleukin-12/23 group experienced side effects, compared with 72 percent of the placebo group. The difference was not considered statistically significant.
The high response rate to the drug supports the idea that psoriasis is a disease with an immune basis, researchers said.
"The number one thing this article does is give us further evidence of the immune-mediated nature of psoriasis," said Dr. Daniel Bennett, an assistant professor of internal medicine at Texas A&M Health Science Center College of Medicine and a dermatologist with Scott & White Hospital. "The argument in the past was that the problem was primarily in the skin vs. being immune-mediated. But the more we tinker with the actual signaling molecules in the immune response, the more evidence that it seems to be immune-mediated."
The drug falls into the class of medications called biologics, which have specific mechanisms of action. This compound works on signaling molecules in the immune response that have not been targeted before. "It's an expansion of the biologics," Bennett said.
But the fact that the disease went away for such a long period of time after only one injection also implies that there's another mechanism of action.
"Either the drug stays around a lot longer than anyone could possibly imagine or it has some down-regulatory effect," Krueger said. "Currently, it's our belief that the latter is the case because the drug has a 21-day half life."
The interleukin-12/23 monoclonal antibody also appears to work against inflammatory bowel disease, indicating that the interleukin-12/23 pathway is common to both conditions.
SOURCES: Gerald G. Krueger, M.D., Benning presidential endowed chair in the department of dermatology, University of Utah, Salt Lake City; Liz Horn, Ph.D., director, research, National Psoriasis Foundation, Portland, Ore.; Daniel Bennett, M.D., assistant professor, internal medicine, Texas A&M Health Science Center College of Medicine, and dermatologist, Scott & White Hospital, Temple, Texas; Feb. 8, 2007, New England Journal of Medicine
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