NEW YORK – An experimental treatment for rheumatoid arthritis being developed by Johnson & Johnson and Schering-Plough Corp appeared to be effective and very safe in three late-stage trials, the companies said Tuesday.

The once-monthly injectable drug, called golimumab, is a newcomer in a family of arthritis medicines that work by blocking an inflammation-causing protein called tumor necrosis factor (TNF).

The drug, now awaiting approval in Europe and expected to be submitted for U.S. approval in coming weeks, could garner annual sales of $1 billion by 2012, according to Cowen and Co.

Golimumab met its primary goal in two of the trials – of reducing symptoms by at least 20 percent. Moreover, in one of those trials, such relief was seen after 14 weeks of treatment among patients who had previously failed to benefit from standard anti-TNF medicines.

“It's the first trial to show that an anti-TNF drug can work with previous anti-TNF failures,” said Dr. Roy Fleischmann, a professor at the University of Texas Southwestern Medical Center, a lead researcher for the trials.

He said the drug could be especially suitable for an estimated 20 percent of patients who now fail to benefit from anti-TNF medicines.

They include Abbott Laboratories Inc's Humira, given by injection once every two weeks; Wyeth's once-weekly injectable Enbrel; and Remicade, sold by J&J and Schering-Plough, which is given every four to eight weeks by intravenous infusion.

All are blockbuster products, thanks to their ability to control arthritis symptoms. But because they work by taming the immune system, they also increase the risk of infection, including reactivation of tuberculosis.

J&J said golimumab was very well tolerated, its most common side effect being mild irritation at the site of injections.

In another phase 3 study, the drug likewise relieved symptoms by at least 20 percent. But it narrowly failed to meet that study's tougher primary goal, of reducing symptoms by at least 50 percent among patients who had not previously been treated with a widely used older oral medicine called methotrexate.

“The overall data from these trials are compelling, with golimumab appearing to be similar in efficacy to anti-TNF drugs that have already been approved,” said Fleischmann, who noted that golimumab was not tested head to head, however, against any anti-TNF drug in the studies.

Results from the studies were presented at the annual meeting of the European League Against Rheumatism, being held in Paris.

(Editing by Braden Reddall)