* Drug reduces pain but infection risks seen
* FDA panel to weigh in Tuesday
* Novartis shares flat (Adds FDA staff, Novartis, analyst comments)
By Lisa Richwine
WASHINGTON, June 17 (Reuters) - A Novartis AG <NOVN.VX> <NVS.N> medicine reduced pain from gout but also appeared to raise the chances of serious infections and other problems, U.S. drug reviewers said.
Food and Drug Administration staff, in documents released on Friday, said determining whether the benefits of Ilaris outweighed risks was "complicated" in part because the product has extended effects in the body that are not typical of an acute treatment. The impact of just a single injection may be "protracted," FDA reviewer Sarah Yim wrote in a memo to an advisory panel that meets Tuesday.
The panel of outside experts will decide whether to recommend approval of Ilaris, which is now sold for treating a rare inflammatory disorder. Novartis has predicted the medicine could generate blockbuster sales if it won clearance for gout and juvenile rheumatoid arthritis.
The FDA will make the final decision on Ilaris but usually follows panel recommendations.
Deutsche Bank analyst Richard Parkes said the panel likely would support Ilaris for gout despite the FDA's questions.
"We believe the majority of these issues are benign and can be addressed through labeling or post-marketing requirements," Parkes said in a research note.
Parkes estimated "relatively modest sales" of Ilaris in gout reaching ${esc.dollar}510 million in 2016.
Gout is a type of arthritis that occurs when uric acid builds up in the joints. Typically one or a few joints are affected such as the big toe or ankle. About 8.3 million U.S. adults have gout, Novartis said.
FDA reviewers, in a preliminary analysis, said two Novartis studies showed Ilaris decreased pain more than an older drug, triamcinolone, and reduced the risk of a new flare of pain.
The Novartis drug also was linked to twice as many potential side effects that were considered serious. The rate was 7 percent for Ilaris compared with 3 percent for the other medicine.
Serious infections were seen in 2 percent of Ilaris patients and none with the comparison drug.
"Given that (Ilaris) is expected to provide primarily a symptomatic benefit, is the risk of infection still outweighed by the clinical benefits?" FDA reviewer Yim asked in the memo.
Ilaris also "appeared to be associated with an increase in a number of findings, which together, could ultimately result in a negative impact in gout patients" including reduced kidney function, she said.
Some data suggested the risks could be dose-related. "It would have been useful to have additional data from a lower dose," Yim added.
Novartis, in a summary released by the FDA, said Ilaris offered a "positive overall benefit/risk ratio for the intended population" of patients who can't get adequate relief with older therapies.
Novartis shares were flat in Swiss trading. (Reporting by Lisa Richwine, editing by Gerald E. McCormick, Dave Zimmerman)
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