P294 Antibodies to recombinant enzyme in Pompe's disease

Abstract

Myozyme (alglucosidase alfa) is drug indicated for use in patients with Pompe disease (GAA deficiency). During the drug administration, life-threatening and severe allergic reactions have been observed. These reactions included anaphylactic shock, cardiac arrest, respiratory distress, hypotension, bradycardia, hypoxia, bronchospasm, dyspnea, angioedema, urticaria, etc. Acute cardiorespiratory failure requiring intubation and inotropic support has been observed after infusion with Myozyme in infantile-onset Pompe disease patients. The most common adverse reactions are Infusion reactions – fever, rush, tachycardia, hypertension, pallor, etc. There is also a risk of cardiac arrhythmia and sudden cardiac death during general anesthesia. Usually, before the infusion of Myozyme patients are pre-medicated with antihistamines, antipyretics and steroids. But, infusion reactions may still occur at any time during, or up to 2 hours after, the infusion. Treatment of less severe reactions includes slower infusion rate, and antihistamines, antipyretics and steroids. Clinical investigations of the patients with Pompe disease often reveal the presence of the IgG antibodies to alglucosidase alfa. The patients with significant titers of these antibodies have a poorer response to treatment and have more often infusion reactions. We would like to present a case of a girl with infantile onset Pompe disease. The treatment with Myozyme has been started when she was 4 months old. It was noticed that her infusion reactions gradually became more often and more severe, including anaphylactic shock. At that moment, we ceased further Myozyme infusions and investigated for the presence of IgG antibodies. The titer of IgG antibodies was found to be high. Our aim was to neutralize those antibodies. At the same time, the paper about this was published (N Engl J Med. 2009 ; 360(2):194-5.). Therefore, we started the same treatment protocol: rituximab + intravenous immunoglobulin + methotrexate. The protocol is not over yet, but our patient is receiving the Myozyme treatment again and without allergic reaction.