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Gene therapy successful for hemophilia B

Researchers from Erasmus MC and three other UMC's have showed that gene therapy in patients with severe hemophilia B reduces the number of bleedings.

A European study, led in the Netherlands by Prof. Frank Leebeek of Erasmus MC in Rotterdam showed that AAV-based gene therapy in patients with severe hemophilia B resulted in a clinically relevant increase of Factor IX (nine) levels in blood and thereby reduced the number of bleedings.

In the successful study 6 of the total 10 patients were treated in the Dutch hemophilia treatment centers from Erasmus MC, UMCG, AMC and UMCU. The important results were presented this week at the Congress of the American Society of Hematology in Atlanta and are published in the renowned Journal Blood. Hemophilia B is an inherited bleeding disorder which caused by a deficiency of coagulation factor IX in blood.

Frank Leebeek HematologiePatients with the severe form of this disorder have frequent spontaneous bleeds, mostly in joints and muscles, eventually leading to arthropathy and disability. The current treatment consists of regular infusion of coagulation factor concentrates, with the aim to reduce spontaneous and traumatic bleeding. This treatment is a severe burden for the patients, who have to intravenously inject themselves 2-3 times weekly to administer the factor concentrates. Treatment with concentrates is also very costly, about 200.000 euro per year per patient.

Blood stream
Gene therapy uses a modified non-pathogenic virus, which has the FIX gene incorporated. In this study an Adeno-Associated Virus 5 - FIX gene product, produced by uniQure biopharma located in Amsterdam, was administered via a 30 minute infusion in 10 patients with hemophilia B. After infusion in the blood stream, the virus vector will be transported to the liver, where it is incorporated in liver cells, which will subsequently synthesize FIX. In all patients treated with two dose levels of gene therapy FIX was measurable in blood, with a mean level of 4.8 % using the low dose and 7.2% using the high dose. This resulted in 90% decrease of spontaneous bleeds across all 10 patients, with no bleeds observed in patients receiving the higher dose in the last 9 months of follow up.

Of the nine patients that previously treated themselves regularly with replacement therapy, eight could stop these infusions after gene therapy. This resulted in an estimated total cost saving of around 2.000.000 euro per year. Treatment-related adverse events were minimal and included transient mild and asymptomatic elevations in liver enzyme levels. Some patients are now more than two years after gene therapy with continued, stable expression of FIX.

Prof. Leebeek: "This important study shows that this investigational gene therapy is safe and effective for patients with hemophilia B and reduces the number of bleeds dramatically, as well as the use of coagulation factor concentrates. We will conduct a large follow-up study with 30 to 40 patients in Rotterdam."

Date published: 20 December 2017.

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