WASHINGTON, D.C. ( TheStreet) -- Human Genome Sciences ( HGSI) brings its experimental lupus drug Benlysta in front of a U.S. Food and Drug Administration advisory panel today, a pivotal step in the company's efforts to market the first new lupus drug in about 50 years.

If approved, Benlysta is expected to be the first blockbuster drug to emerge from Human Genome's research labs, possibly generating peak sales greater than $2 billion. GlaxoSmithKline ( GSK) will co-market Benlysta under a partnership agreement with Human Genome.

The FDA is asking its advisory panel Tuesday to consider the benefits and risks of Benlysta in patients with the autoimmune disease lupus. Human Genome Sciences conducted two, large phase III studies demonstrating greater overall patient response to treatment with Benlysta compared to placebo.

In a review of Benlysta posted Friday, FDA reviewers questioned the robustness of Benlysta's benefit and raised some safety concerns, including a potential higher suicide risk associated with the drug.

"Clearly there is a need for effective therapies in SLE lupus ," FDA concluded in its review. "However whether belimumab's Benlysta's benefits sufficiently outweigh its risks is the crux of the issue... If belimumab only has a modest effect for some patients and manifestations, is a possible increased risk of death, infection, or neuropsychiatric adverse effects worth the potential benefit?"

Human Genome Sciences shares TK in Monday trading. The stock will be halted Tuesday during the FDA advisory panel.

Lupus is a chronic disease in which the body's immune system creates auto-antibodies that attack connective tissue, resulting in inflammation and tissue damage, often to the heart, joints, lungs and kidneys. Women are more often diagnosed with lupus than men, and the disease goes through periods where it flares up then goes into remission.

Benlysta is a human monoclonal antibody designed to recognize and tamp down the biological activity of B-lymphocyte stimulator, or BLyS, a substance that was discovered by Human Genome. High levels of BLyS plays a role in the development of abnormal B cells (B cells are a component of the immune system), and abnormal B cells lead to increased auto-antibody formation.

Benlysta appears to lower levels of BLyS and therefore stop young B cells from growing abnormally. One advantage to treating lupus with this approach is that Benlysta doesn't appear to affect more mature B cells, which are an important part of a patient's immune system.

--Written by Adam Feuerstein in Boston.

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