(Reuters) - Johnson & Johnson's Stelara was significantly better than placebo at inducing clinical response and remissions in patients with moderate to severe Crohn's disease, according to data from a late stage trial, providing ammunition for a potential expanded approval of the medicine.

Stelara, a biotech medicine that blocks inflammation, is approved to treat the skin condition scaly plaque psoriasis and a type of arthritis associated with psoriasis.

J&J reported $613 million in third-quarter Stelara sales. The company said it was on track for global approval filings for Crohn's this year.

Subjects in the 628-patient trial presented on Monday received either a single infusion of 130 milligrams of Stelara, a Stelara infusion of 6 mg per kilogram of weight or a placebo.

After six weeks, 52 percent of those in the 130 mg group and 56 percent in the 6mg/kg group experienced a clinical response, defined as a reduction from baseline of at least 100 points in the Crohn's Disease Activity Index score. That compared with 29 percent in the placebo group.

In addition, 31 percent of the Stelara 130 mg group and 40 percent in the other dosing arm achieved clinical remission by week 8 of the study, versus 20 percent for placebo.

The results were deemed to be statistically significant.

"I think this is an approvable drug," said Dr. Brian Feagan, co-lead investigator of the study presented at the American College of Gastroenterology meeting in Honolulu.

"We need drugs that are alternatives to TNF blockers," he said of widely used biologic medicines such as AbbVie's Humira. "This drug can be a first-line biologic therapy."

Patients in the study had previously failed to be helped by steroids or immunomodulator drugs, such as methotrexate. Another study is testing Stelara in those who failed anti-TNF therapy.

Crohn's disease is a chronic inflammatory condition of the gastrointestinal tract that affects about 700,000 Americans and 250,000 Europeans. Symptoms can include frequent diarrhea, abdominal pain and rectal bleeding.

In addition to reductions in signs and symptoms of disease, Stelara patients reported significant improvements in the Inflammatory Bowel Disease Questionnaire, a health-related quality of life measure, researchers said.

The rate of serious side effects, including infections, was similar for Stelara and placebo.

"Serious infection is really the thing that clinicians worry about and there was not a signal here, which is surprisingly great news," Feagan said.

(Reporting by Bill Berkrot; Editing by Nick Zieminski)