Johnson & Johnson unveiled Thursday results of a late-stage trial that showed its psoriasis drug, ustekinumab, was more effective than rival Enbrel sold by Wyeth and Amgen.

The results of the study were presented at a dermatologists’ medical meeting in Paris. The study involved 903 patients with moderate to severe psoriasis. Psoriasis, a skin disorder that causes scaly red patches, affects an estimated 7.5 million Americans.

The 12-week study showed that ustekinumab, also called Stelara, decreased the severity of the psoriasis by 68 percent in patients taking a 45-milligram dose and 74 percent in patients taking a 90-milligram dose, while patients taking 50 milligrams of Enbrel only saw a 57 percent reduction in their condition. Both Enbrel and Stelara are given through injections, but the later would be administered less frequently. Stelara injections work by blocking an inflammation-causing protein called tumor necrosis factor (TNF).

“These findings reinforce the promise of Stelara as an infrequently administered and highly effective biologic therapy for the treatment of adults with moderate to severe psoriasis,” Bruce Strober, one of the trial investigators, said.

The drug also proved more efficient than Enbrel in reducing the severity of psoriasis by 90 percent. To be more specific, 36 percent of patients on low-dose ustekinumab and 45 percent on the higher dose saw such an improvement compared with 23 percent of those receiving Enbrel.

“We’ve never seen clearance along the lines of what we’ve been seeing with ustekinumab. This is pretty dramatic,” Dr. Alan Menter, a Baylor University dermatologist who helped lead the study, said.

Also, patients given ustekinumab had fewer side effects comparable to patient given Enbrel. There were fewer cases of redness or irritation at the injection site in ustekinumab patients.

Wyeth questioned ustekinumab trial’s results saying they were based on a short-term study, whereas psoriasis is a systemic, chronic disease that requires long-term treatment.

“This is a short-term study with no longer efficacy conclusions” or long-term safety data, Wyeth said in a statement.

A US Food and Drug Administration panel unanimously voted in June in favor of ustekinumab. However, seven of the panel’s 11 members showed their concern about the self-administration of the injections and recommended that the drug be given by a physician.

“This recommendation takes away from the convenience advantage of the product,” Raymond James analysts Jayson Bedford, said.

J&J has already applied for US approval of the drug and expects a decision before the end of the year. If approved, analysts expect the drug to generate hundreds of millions of dollars in sales within a few years considering Enbrel’s sales last year that reached $5.3 billion, being one of the best-selling drugs in the world, according to IMS Health. Enbrel was introduced in 1998 for rheumatoid arthritis but soon after received regulatory approval for psoriasis too. Ustekinumab global market is expected to worth about 1.1 billion dollars in 2008 and almost 3 billion in 2010, Mike Weinstein, analyst of JPMorgan Chase, said.