A drug that holds significant promise for treating the devastating effects of hemolytic uremic syndrome (HUS) has been approved for limited use, the U.S. Food and Drug Administration announced Friday. Soliris (generically eculizumab), marketed in this country by Alexion Pharmaceuticals, will for now be allowed only to treat patients with atypical hemolytic uremic syndrome (aHUS), which accounts for 5 to 10 percent of all cases of HUS, an acute condition that disproportionately affects children. But the fast-track approval by the FDA for the use of Soliris to treat atypical HUS, and to use it to treat children, indicate it may eventually be available for more common forms of the disease. The European Committee for Medicinal Products for Human Use also gave a positive opinion of Soliris for aHUS treatment on Friday. Approval by the European Commission is expected in about two months, the drug manufacturer said. Soliris — classified as an orphan drug, meaning it has demonstrated promise for treating rare diseases or conditions — works by blocking proteins that impair kidney function. HUS is a life-threatening syndrome that can lead to kidney failure, coma and stroke, and affects a significant percentage of people – especially children – who are infected with foodborne E. coli O157:H7 and other Shiga-toxin producing serotypes. It is the most common cause of acute kidney failure in infants and young children; more than half the children with HUS require dialysis. This summer, during the outbreak of E. coli O104:H4 that ravaged Europe, of the 4,321 infections reported by the Robert Koch Institute, 852 were HUS cases — three times the normal rate. And of the 50 people who died in the outbreak, 32 were HUS patients. Three HUS patients in Germany who came perilously close to death were all 3 years old. Suffering with severe infections, the children were not responding to conventional treatment, which is blood plasma exchange, and doctors feared they would die or suffer permanent brain damage. Given this “devastating prognosis,” according to an article in the New England Journal of Medicine, the children were given Soliris. All of them regained renal function and six months later remained in full remission, a “dramatic resolution of symptoms” when recovery had seemed unlikely, the article authors stated. Soliris was first approved by the FDA in March 2007 to treat paroxysmal nocturnal hemoglobinuria (PNH), a rare blood disorder that can disable and kill. But it had never been tested or approved for treating E. coli infections before it was used in Germany, and doctors were astounded by the results. After receiving the drug, one girl improved within 24 hours, after three days no longer needed dialysis and was discharged from the hospital within nine days to return home, according to a report in Der Spiegel. In the FDA’s announcement, Dr. Richard Pazdur, director of the Office of Hematology and Oncology Products in the agency’s Center for Drug Evaluation and Research, noted that Friday’s approval of Soliris “underscores how an increased understanding of the biology of a disease and of how a drug interacts with that process can expedite drug development.” Soliris’ safety and effectiveness, according to the FDA, were established in two single-arm trials in 37 adults and adolescent patients with aHUS, and one retrospective study in 19 pediatric patients and 11 adult patients with aHUS. Kidney function improved in the patients treated with Soliris. Several who were not responding to plasma therapy no longer required dialysis after they were given the drug. Soliris will continue to be available only on a restricted basis, and doctors will have to register to prescribe the medication, as well as provide a guide to enrolled patients advising them of its experimental nature. One side effect is the increased risk of meningococcal infection. Alexion agreed to provide Soliris to Germany for free during the E. coli O104:H4 outbreak. It has been called the most expensive drug in the world, with a cost of at least $22,000 per patient. But the estimated total medical costs for conventional treatment of HUS are also high — typically at least $100,000 but sometimes mounting to millions, depending on complications. Soliris was reviewed under the FDA’s six-month “priority review” for drugs that may offer major advances in treatment or that provide a treatment when no adequate therapy exists. The therapy also is being approved under the FDA’s accelerated approval program, designed to provide patients with earlier access to promising new drugs, followed by further studies to confirm the drug’s clinical benefit.