Alexion Pharmaceuticals Inc. gained expansion from the FDA of the label for Soliris (eculizumab) to treat neuromyelitis optica spectrum disorder (NMOSD) in adults who are anti-aquaporin-4 (AQP4) antibody positive.
Some 73% of patients with NMOSD, a rare disorder that attacks the central nervous system without warning, test positive for anti-AQP4 autoantibodies, and U.S. regulators gave their nod to the label add-on following an expedited six-month priority review. NMOSD afflictions, also called relapses, can damage the brain, optic nerve and spinal cord, causing long-term disability.
Complement activation due to anti-AQP4 antibodies is one of the primary underlying causes of the harm done to patients by NMOSD, and Soliris proved its mettle in a study called Prevent, where the complement inhibitor showed safety and efficacy, meeting the primary endpoint of prolonging the time to first adjudicated relapse and reducing the risk of such episodes.
NMOSD disproportionately strikes young women, with the average age of first onset at 39 years. Race is also a significant risk factor for disability and mortality, too; in the U.S., African Americans are overrepresented among patients diagnosed with NMOSD and more likely to suffer more frequent and more severe attacks.
Previously known as Devic's disease, NMOSD is often confused with other neurological illnesses such as multiple sclerosis, which can delay diagnosis and treatment with medicines that may even worsen disease progression, Alexion noted.
Jefferies analyst Eun Yang, in a report last month, cited a neurologist as saying about half of AQP4-positive NMOSD patients are currently on Rituxan (rituximab, Roche Holding AG/Biogen Inc.) intravenously twice a year, with about 75% achieving remission (i.e., no relapses in three years) and about 12% failing – despite near complete B-cell depletion – because of logistical issues (missing their infusion days or finding that their payers denied coverage).
Soliris was first approved in 2007 for paroxysmal nocturnal hemoglobinuria (PNH) and clearance followed in atypical hemolytic uremic syndrome (aHUS) in 2011. In the fall of 2017, the compound was given the FDA's go-ahead for generalized myasthenia gravis. Boston-based Alexion estimates 4,000 to 5,000 U.S. NMOSD patients would be eligible for Soliris, potentially a larger opportunity than PNH and aHUS combined, Yang pointed out.
Shares of Alexion (NASDAQ:ALXN) closed Thursday at $126.11, up 77 cents.