SB-525 is a gene therapy being developed by Sangamo Therapeutics to treat hemophilia A. The U.S. Food and Drug Administration (FDA) has granted SB-525 fast track and orphan drug designations. Both support a Phase 1/2 clinical trial that is expected to start in mid-2017 and run through 2021.

People with hemophilia have bleeding disorders due to genetic modifications that diminish the production of blood coagulation factors — factor VIII in the case of hemophilia A, and coagulation factor IX in the case of hemophilia B.

The development of drugs that rely on techniques of gene therapy or editing may help hemophilia patients to overcome problems associated with this disease by inducing the generation of coagulation factors through normal cell processes of protein formation.

How SB-525 works

The goal of treatment with SB-525 is to reduce or eliminate the need for coagulation factor VIII replacement therapy by getting cells to naturally produce this important protein.

SB-525 is composed of a small portion of genetic material with the code for the production of factor VIII. Once inside cells, it binds to the existing genetic material to allow for the correct formation of this coagulation factor through the normal processes of cellular protein formation.

The genetic information within SB-525 is carried and delivered to liver cells (where coagulation factors are produced) using a modified, harmless form of the adeno-associated virus, which normally travels to the liver and infects the organ.

Overall, a single SB-525 administration may provide a durable production of coagulation factor VIII in liver cells, which is then carried into the blood stream and can assist in the formation of blood clots, protecting against bleeding complications in hemophilia patients.

Studies with SB-525

Results from a preclinical study showed a long-term production of human coagulation factor VIII in mouse models of hemophilia A, through the use of adeno-associated viral vector delivery of genetic information to the liver.

Sangamo plans to initiate a first clinical trial for SB-525 in hemophilia A patients, who will be followed for three years, before the end of 2017. The Phase 1/2, open-label, adaptive, and dose-ranging study (NCT03061201) will evaluate the safety, tolerability, and efficacy of SB-525 in treating about 20 adults with severe hemophilia A. More information is available on the study’s clinical webpage.

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