The FDA has approved Bluebird Bio’s Zynteglo as the first cell-based gene therapy for the treatment of adult and pediatric patients with beta-thalassemia who require regular red blood cell transfusions.

The drug, betibeglogene autotemcel (also known as beti-cel), is a one-time gene therapy product administered as a single dose. Each dose of Zynteglo is a customized treatment created using the patient’s own bone marrow stem cells that are genetically modified to produce functional beta-globin.

“Today’s approval is an important advance in the treatment of beta-thalassemia, particularly in individuals who require ongoing red blood cell transfusions,” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research. “Given the potential health complications associated with this serious disease, this action highlights the FDA’s continued commitment to supporting the development of innovative therapies for patients who have limited treatment options.”

Beta-thalassemia is a type of inherited blood disorder that causes a reduction of normal hemoglobin and red blood cells in the blood, through mutations in the beta-globin subunit, leading to insufficient delivery of oxygen in the body. The reduced levels of red blood cells can lead to a number of health issues including dizziness, weakness, fatigue, bone abnormalities, and more serious complications. Transfusion-dependent beta-thalassemia, the most severe form of the condition, generally requires life-long red blood cell transfusions as the standard course of treatment. These regular transfusions can be associated with multiple health complications of their own, including problems in the heart, liver, and other organs due to an excessive build-up of iron in the body.

“The FDA approval of Zynteglo offers people with beta-thalassemia the possibility of freedom from burdensome regular red blood cell transfusions and iron chelation, and unlocks new possibilities in their daily lives,” said Andrew Obenshain, CEO of Bluebird Bio. “After more than a decade of research and clinical development, and through the perseverance of clinicians, patients, and their families, the approval of Zynteglo marks a watershed moment for the field of gene therapy. As the first ex vivo lentiviral vector gene therapy approved in the U.S. for the treatment of people with beta-thalassemia, we are ushering in a new era in which gene therapy has the potential to transform existing treatment paradigms for diseases that currently carry a lifelong burden of care.”

The approval is impactful for Bluebird Bio, which had a rocky spring. Earlier this year, in March, shares of Bluebird Bio plunged 62% including a 10% stock price drop triggered by Bluebird’s disclosures about the resignation of its CFO and doubts about its ability to continue as a growing concern.

Just one month later the company announced that they were eliminating roughly 30% of its staff (an estimated 155 jobs) during the second and third quarters as part of a restructuring plan designed to generate $160 million in savings over the next two years.

The safety and effectiveness of Zynteglo were established in two multicenter clinical studies that included adult and pediatric patients with beta-thalassemia requiring regular transfusions. Effectiveness was established based on achievement of transfusion independence, which is attained when the patient maintains a pre-determined level of hemoglobin without needing any red blood cell transfusions for at least 12 months. Of 41 patients receiving Zynteglo, 89% achieved transfusion independence.

This news follows last month’s vote by FDA’s Cellular, Tissue, and Gene Therapies Advisory Committee (CTGTAC) which recommended approval by the agency of two Bluebird Bio lentiviral vector gene therapy candidates: beti-cel and elivaldogene autotemcel, or eli-cel, for the treatment of cerebral adrenoleukodystrophy (CALD) in patients less than 18 years of age who do not have an available and willing human leukocyte antigen (HLA)-matched sibling hematopoietic stem cell (HSC) donor.

The most common adverse reactions associated with Zynteglo included reduced platelet and other blood cell levels, as well as mucositis, febrile neutropenia, vomiting, pyrexia (fever), alopecia (hair loss), epistaxis (nosebleed), abdominal pain, musculoskeletal pain, cough, headache, diarrhea, rash, constipation, nausea, decreased appetite, pigmentation disorder, and pruritus (itch).

There is a potential risk of blood cancer associated with this treatment; however, no cases have been seen in studies of Zynteglo. Patients who receive Zynteglo should have their blood monitored for at least 15 years for any evidence of cancer. Patients should also be monitored for hypersensitivity reactions during Zynteglo administration and should be monitored for thrombocytopenia and bleeding.