Alexion: the NME of blood disease
received a boost when the first ever drug to treat the disease was
approved.
The US Food and Drug Administration (FDA) has given the go ahead to Alexion Pharmaceuticals to market its new molecular entity (NME) therapy, Soliris (eculizumab). The monoclonal antibody therapy is designed to treat the underlying cause of paroxysmal noctural haemoglobinuria (PNH): weak red blood cells that are destroyed more quickly than normal. A chronic reduction of red blood cells can cause several debilitating symptoms, including severe anaemia, fatigue, intermittent abnormally darkened urine and blood clots. There is currently no specific treatment for PNH and, in severe cases, patients are forced to undergo frequent blood transfusions or even a bone marrow transplant. On average, patients with PNH only survive 10 to 15 years from the time of diagnosis. "This product is important in that it offers a treatment other than blood transfusion that may help this small population of patients who are often very ill," said Dr Steven Galson, director of the Center for Drug Evaluation and Research at the FDA. Soliris does not cure PNH but instead works to combat a mutation on the PIG-A gene. This defect leads to red blood cells being formed that lack enough proteins on their surface to protect the cells from being destroyed by the immune system. Several proteins carry out this immune attack, including one - C5 - that must first break into two parts before it can launch its attack. Soliris binds to C5, preventing from splitting and thus stopping the destructive process that causes red blood cells to swell and burst - a process called haemolysis. "Soliris directly targets the underlying disease process responsible for debilitating symptoms that may contribute to shortened life spans of PNH patients," said Dr Wendell Rosse, a professor of medicine at Duke University, US. "Having cared for more than 300 patients with PNH over my career, I believe this is the most important advance that has been made in the treatment of this disease." In a phase III study, half of the Soliris-treated patients achieved haemoglobin stabilisation compared with none of the patients in the placebo group and the median number of blood transfusions was reduced from 10 units per patient to none. However, by interfering with the body's natural immune system, Soliris increases the risk of patients contracting serious infections, particularly those causing bacteria meningitis. All 196 patients in the clinical trial were vaccinated against this type of infection. However, two of them developed an infection of the bloodstream caused by meningococcal bacteria. Alexion are currently waiting on a decision from the European Medicines Evaluation Agency on whether Soliris will be approved for European Union patients with PNH. It submitted a marketing authorisation application last September. One other possible stumbling block remains for Alexion. PDL Biopharma has filed a patent infringement lawsuit against Alexion. PDL claims that, in developing Soliris, Alexion used some of its intellectual property regarding humanising antibodies. Survival Time Socie G, Mary J Yves, de Gramont A, et al. Paroxysmal nocturnal haemoglobinuria: long-term follow-up and prognostic factors. Lancet 1996; 348:573-577. Hillmen P. Lewis SM, Bessler M, Luzzatto L, Dacie JV. Natural history of paroxysmal nocturnal hemoglobinuria. N Engl J Med 1995; 333:1253- 1258
