(Adds comment from J&J, share move)
By Toni Clarke
July 31 (Reuters) - There were more deaths in patients taking Johnson & Johnson's experimental rheumatoid arthritis drug sirukumab than among those taking a placebo, staff reviewers for the U.S. Food and Drug Administration said in a report published Monday.
The report comes two days before an outside committee of advisors meets to discuss the drug and recommend whether it should be approved. The FDA is not obliged to follow the advice of its advisers but typically does so.
The most common causes of death were major heart problems, infection and malignancies.
Other potential safety issues related to immune system suppression were similar to other products in the class, but the trend of increased overall mortality "seems unique for the sirukumab program," the report said. It was published on the FDA's website.
Brian Kenney, a J&J spokesman, said rheumatoid arthritis is a complex and serious disease, with patients frequently cycling through multiple therapies until finding one that may work for them. "We are confident in the benefit-to-risk of sirukumab," he said.
J&J was originally developing the drug, which would be known as Plivensia if approved, with GlaxoSmithKline Plc. GSK recently said it would end the program and return all rights to J&J. GSK had rights to the drug in North, Central and South America.
Sirukumab is a human monoclonal antibody that blocks a cytokine in the body known as interleukin 6 (IL-6), which can contribute to the inflammation associated with rheumatoid arthritis, an autoimmune disorder that affects more than 1.3 million Americans.
Sirukumab is designed to patients who have failed or cannot tolerate one or more disease modifying drug such as methotrexate.
Sirukumab would compete with Roche Holding AG's IL-6 inhibitor Actemra and a recently approved IL-6 therapy, Kevzara, or sarilumab, made by Sanofi SA and Regeneron Pharmaceuticals Inc.
Analysts on average forecast global sales of Kevzara to reach about $667 million by 2020, according to Thomson Reuters data. They expect sales of sirukumab, if approved, to be about $450 million over the same period.
Neither Kevzara nor sirukumab are sufficiently different from Actemra to gain a great deal of traction in the market, said Damien Conover, an analyst with Morningstar.
"I don't think they are really going to move the needle for any of these large companies," he said.
J&J shares were up 0.6 percent at $132.70 in morning trading on the New York Stock Exchange. (Reporting by Toni Clarke in Washington; Editing by Bernadette Baum and Nick Zieminski)