Patients with hemophilia B were cured with gene therapy

Oleg Lischuk, N+1

American scientists have successfully tested a new gene therapy drug for the treatment of hemophilia B. The results of the work are presented at the 21st Congress of the European Hematology Association in Copenhagen (High et al., AAV- mediated gene therapy for hemophilia B-expression at therapeutic levels with low vector doses).

The experimental drug SPK-FIX was developed by Spark Therapeutics. An adeno-associated virus (AAV) modified for selective binding to liver cells was used as a vector. This vector serves to deliver and embed in them the gene for coagulation factor IX of the Padua variant, about eight times more active than the usual factor IX, the deficiency of which leads to the development of hemophilia B.

SPK-FIX was administered intravenously to three patients (23, 18 and 47 years old) at a dose of 5×10 ¹¹ vector genomes per kilogram of body weight. In the first two volunteers, the activity of factor IX in the blood was established at the level of 28 and 30 percent after 18 and seven weeks, respectively (10 percent is usually enough to maintain normal blood clotting). In the third, after three weeks, it reached 16 percent. On the second day after therapy, this participant injected himself with recombinant factor IX once, suspecting hemorrhage in the ankle joint. More patients did not need replacement therapy, bleeding for 28 total man-weeks was not observed.

The tolerability of the therapy was good, no serious side effects were observed. A short-term increase in the level of liver enzymes in the blood did not exceed the norm by more than 1.5 times, the immune response to the drug was minimal or absent, the appointment of glucocorticoid hormones was not needed.

To date, this has become the most successful trial of hemophilia B gene therapy – other drugs were less effective and produced serious side effects. According to MIT Technology Review, several more gene therapy drugs are currently undergoing clinical trials: UniQure and Baxalta are testing the treatment of hemophilia B, and BioMarin is testing the more common hemophilia A associated with factor VIII deficiency. Previously, gene therapy for hemophilia was successfully tested on dogs.

Additional, larger-scale studies are needed for the clinical use of SPK-FIX. If the drug is approved for use, treatment will be extremely expensive – its cost for one patient can reach a million dollars. However, gene therapy provides a lasting cure, and currently about one in five thousand men (women practically do not suffer from hemophilia) requires regular injections of coagulation replacement factors, the market of which is about $ 10 billion a year. SPK-FIX could eliminate this need for about 40 percent of them (the rest have antibodies to AAV in their blood).

Hemophilia is a group of hereditary diseases associated with a deficiency of blood clotting factors. With them, the formation of blood clots is disrupted, which leads to bleeding and hemorrhages of varying severity.

Portal "Eternal youth" http://vechnayamolodost.ru  01.07.2016