FDA Grants Priority Review for bluebird bio’s β-Thalassemia Gene Therapy

On November 22nd, bluebird bio announced that the FDA has accepted and granted priority review for betibeglogene autotemcel (beti-cel), its gene therapy for β-thalassemia, a rare blood disease. The FDA has a response date set for May 20, 2022. 

An approval would make beti-cel the third approved gene therapy in the US, after Spark Therapeutics’ Luxturna and Novartis’ Zolgensma. Beti-cel could also become the first ex vivo gene therapy, where a patient’s cells are extracted, treated, and re-infused into the body.

One-time Solution for β-Thalassemia

A gene mutation significantly cuts levels of hemoglobin (Hb) in people with β-thalassemia. As a result, they suffer from severe anemia and require regular infusions of red blood cells (RBC). Additionally, patients have to go through chelation therapy to reduce excess iron from hemoglobin in the RBC infusions, which could cause organ failure. 

Beti-cel is positioned as a one-time treatment for β-thalassemia, offering a way out of regular RBC infusion and chelation therapy.

The treatment involves taking out hematopoietic stem cells (HSCs) from the patient. Beti-cel fixes the gene mutation by adding functional copies of the gene into the HSCs. The modified HSCs are then returned to the patient’s body. 

Phase 3 studies of the drug have shown that 89%, or 32 out of 36 evaluable patients across all ages and genotypes, no longer need RBC infusions for at least a year post-treatment. 

Adverse events associated with the therapy included abdominal pain, tachycardia, and non-cardiac chest pain, as well as cytopenias (reduction in blood cell number). One serious side effect of thrombocytopenia was recorded and has been resolved. However, the company says side effects were uncommon and, in general, not serious. 

With the encouraging results, bluebird bio is forging ahead with ongoing Phase 3 studies it calls Northstar-2 and Northstar-3. The company is also investigating beti-cel in a long-term follow-up study called LTF-303. 

 “The FDA’s acceptance of our BLA for beti-cel brings us one step closer to potentially providing a one-time treatment that can address the underlying cause of β-thalassemia and offer patients freedom from regular transfusions,” said Andrew Obenshain, CEO of bluebird bio.

“It’s also a critical milestone for bluebird bio as an independent severe genetic disease company. We are moving forward with great discipline and exceptional care to deliver on our commitments to patients and achieve our near-term goal of launching three first-in-class gene therapies in the U.S.”

bluebird bio is currently discussing with the FDA to lift the clinical hold on eli-cel (Lenti-D), its gene therapy for a rare neurodegenerative disease. The treatment was given the red light after a serious adverse event was linked to the gene delivery vector used in the treatment. The company still expects to submit the BLA for eli-cel by the end of 2021.

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Joy Lin

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