bluebird bio's betibeglogene autotemcel (beti-cel; Zynteglo) continues to demonstrate long-term efficacy and a favorable safety profile in patients with transfusion-dependent β-thalassemia (TDT), according to updated data presented at the 66th American Society of Hematology (ASH) Annual Meeting. The gene therapy, already approved by the FDA, has shown sustained curative potential in multiple clinical trials, offering a promising alternative to regular transfusions for affected individuals.
Long-Term Follow-Up Data
The data, derived from 63 participants in the long-term follow-up study LTF-303, included patients previously treated with beti-cel in phase 1/2 and phase 3 clinical trials. Of these, 2 patients have been followed for 10 years, and 51 patients (81.0%) for at least 5 years. Protocol-defined transfusion independence (TI) was achieved by 52 of the 63 patients. According to Dr. Alexis A. Thompson, Chief of the Division of Hematology at Children's Hospital of Philadelphia, the ability to achieve TI was similar across genotypes and age cohorts.
Transfusion Independence and Iron Homeostasis
Notably, all but one of the patients who achieved TI maintained this status through their most recent follow-up. Specifically, TI was achieved by 15 of 22 patients (68.2%) in the phase 1/2 trials and 37 of 41 patients (90.2%) in the phase 3 trials. Markers of iron overload in patients who achieved TI also showed maintenance of normalization for liver iron content and serum ferritin, reflecting improved iron homeostasis.
Quality of Life Improvements
Long-term quality of life measures indicated improvements in both the mental and physical components, as assessed by the Short Form-36 Health Survey in adults and the Pediatric Quality of Life Inventory in pediatric patients.
Safety Profile
The safety data revealed no fatal events and no serious adverse events (SAEs) related to beti-cel occurring more than 2 years post-treatment. There were no cases of malignancies, insertional oncogenesis, or vector-derived replication-competent lentivirus observed. Two cases, focal nodular hyperplasia and immune thrombocytopenia, were deemed possibly related to beti-cel but potentially explained by other causes.
Real-World Evidence
Real-world data from the University Hospital Heidelberg in Germany, where eight patients received beti-cel infusions, support the therapy’s efficacy. All eight patients achieved transfusion independence within 8 to 59 days, with post-treatment hemoglobin levels between 11.3 g/dL and 19.3 g/dL. These findings align with the safety profile observed in clinical trials, although some patients experienced adverse events consistent with the known effects of busulfan, the myeloablative conditioning agent used prior to beti-cel infusion.
Implications for Treatment
"Updated follow-up data of up to 10 years showed that patients treated with beti-cel in clinical trials experienced durable transfusion independence and normal or near-normal hemoglobin, regardless of genotype and age, and a continued favorable safety profile," said Dr. Richard Colvin, chief medical officer of bluebird bio. The long-term data provide additional confidence that the transformational outcomes observed in parent studies are sustained over time, informing treatment decisions for clinicians using this therapy in real-world settings.
While challenges with busulfan conditioning and its impact on gonadal function were noted, the data underscore the potential of beti-cel as a curative option for patients with transfusion-dependent β-thalassemia, offering an alternative to allogeneic hematopoietic stem cell transplantation, especially for those lacking suitable donors.
