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  • Writer's pictureEscalate Life Sciences

Bluebird gene therapy approved by FDA for rare blood disease

Zynteglo is cleared for transfusion-dependent beta thalassemia, but will come at a cost of $2.8 million per patient.

The Food and Drug Administration on Wednesday approved a powerful new treatment for people with an inherited blood condition called beta thalassemia, clearing a personalized gene therapy developed by the biotechnology company Bluebird bio.

The therapy, which showed dramatic benefit in clinical testing, will come at a cost of $2.8 million per patient, making it one of the most expensive medicines sold.

Its approval is a milestone in a number of other respects, too. Beta thalassemia, a disease that in severe cases requires regular blood transfusions for life, has for years been marked as a target for gene therapy. Bluebird’s treatment, which will be sold as Zynteglo, is the first of several in development to reach market in the U.S., giving patients an option that could free them from those transfusions and their associated side effects.

Prior to Wednesday’s decision on Zynteglo, the FDA has previously cleared only two other gene therapies for inherited diseases: one for a form of childhood blindness, the other for a rare and fatal neuromuscular disorder.

Zynteglo’s approval is also significant for Bluebird, a gene therapy pioneer that’s been beset by difficulties in recent years and now faces financial peril. Reaching this point with Zynteglo, and several other gene therapies Bluebird is developing, has taken more than a decade of research and cost the company billions of dollars.

The FDA cleared Zynteglo for adults and children who have severe beta thalassemia and depend on blood transfusions. Typically, these life-sustaining transfusions are needed every two to five weeks, requiring regular trips to health clinics and hospitals as well as medication to manage iron overload.

Clinical testing showed treatment with Zynteglo freed study participants from needing regular transfusions, with 89% of treated patients in Phase 3 studies meeting the criteria for transfusion independence.

In clearing Zynteglo, however, the FDA had to weigh the therapy’s clear benefit against concerns that it might cause cancer. While no cases of cancer were reported in studies of Zynteglo, a study volunteer in a trial of another Bluebird gene therapy for sickle cell disease developed a form of leukemia. The two therapies are similarly designed, although there are differences in how they’re manufactured.

Three participants in a study of a third Bluebird gene therapy for a rare brain disease called CALD also developed a form of bone marrow cancer many months after their treatment.

Published Aug. 17, 2022 Ned Pagliarulo, Lead Editor

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