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Orphan Status Granted for Hemophilia Genome Editing

Blood sample

(Public Domain Pictures/Pixabay)

6 September 2016. Treatments using genome-editing techniques for hemophilia B, a rare blood clotting disease, received orphan therapy status from the U.S. Food and Drug Administration. The therapy is being developed by Sangamo Biosciences, a biotechnology company in Richmond, California.

Hemophilia is an inherited disorder, where a genetic defect causes the proteins needed to mix with platelets allowing blood to coagulate are missing. About 8 in 10 people with the condition have hemophilia type A, where the protein clotting factor 8 is missing. In type B, clotting factor 9 is missing. Factor 9 is made in the liver, and circulates dormant in the blood stream until a blood vessel is damaged, when it is activated by other proteins that set in motion the processes to form a clot.

Sangamo BioSciences develops therapies for infectious diseases and genetic disorders, including hemophilia, with gene transfer and genomic editing therapies. The company’s genomic editing technology employs a process known as  zinc-finger nucleases, where synthetic enzymes modify DNA sequences, including corrections or insertions. These enzymes, with a hydrocarbon and zinc chemistry, branch out in finger-like protrusions that bind with DNA molecules. Sangamo says it engineers the proteins to predictably and consistently bind with longer DNA sequences.

The therapy using zinc-finger nucleases in this case, code-named SB-FIX, edits the albumin gene in the liver that encodes a number of proteins in the blood. SB-FIX delivers enzymes that bind with and correct the defective gene responsible for the missing clotting factor 9 in hemophilia B. The precise targeting of the DNA, says Sangamo, affects only DNA for the specific clotting factor 9, and thus does not affect the rest of the albumin gene. In addition, since children will most likely receive SB-FIX treatments, the therapy is expected to provide stable production of blood clotting proteins for their lifetimes.

Sangamo is planning an early and intermediate-stage clinical trial to test the safety and different dose levels of SB-FIX. That trial will enroll 9 adults with severe cases of hemophilia B. “[O]ur goal is to move into pediatric patients” says Sango vice-president for research and development Geoff Nichol in a company statement, “a population we believe could particularly benefit from a treatment that has the potential to provide lifelong expression of therapeutic levels of factor 9 protein.”

The Orphan Drug Act of 1983 gives FDA authority to designate an orphan drug, for treatments being developed targeting diseases affecting fewer than 200,000 Americans. Therapies, both drugs and biologics, designated as orphan drugs qualify for incentives such as tax credits for clinical trials and exemptions from marketing application fees.

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