Long-Term Efficacy and Safety Results of Betibeglogene Autotemcel Gene Therapy for Transfusion-Dependent Β-Thalassemia

Abstract

Betibeglogene autotemcel (beti-cel) gene therapy for transfusion-dependent β-thalassemia (TDT) involves autologous transplantation of hematopoietic stem and progenitor cells transduced with a modified β-globin gene to produce functional adult hemoglobin (Hb) containing β^A-T87Q-globin (HbA^T87Q). Sixty-three participants with TDT (median age, 17 years [range, 4-35]) received beti-cel in phase 1/2 (n = 22) or phase 3 (n = 41) studies and enrolled in the long-term follow-up LTF-303 study (median follow-up, 5.9 years [range, 2.9-10.1]).

Manufacturing refinements in phase 3 increased transduction efficiency, resulting in higher drug product vector copy number and HbA^T87Q levels, which translated into higher Hb and transfusion independence (TI) rates than in phase 1/2. TI was achieved by 15 of 22 (68.2%) phase 1/2 participants (median weighted average Hb during TI, 10.2 g/dL) and 37 of 41 (90.2%) of phase 3 participants (median, 11.2 g/dL) and was sustained through last follow-up.

Treatment efficacy was similar across ages and TDT genotypes. Among participants achieving TI, 38 of 52 (73%) had discontinued iron chelation at last follow-up, with no increase in liver iron concentration. Markers of ineffective erythropoiesis, including serum transferrin receptor and erythropoietin, improved with restoration of iron homeostasis. Health-related quality-of-life assessment scores showed durable improvements. No malignancies, insertional oncogenesis, or vector-derived replication-competent lentivirus were reported.

These findings establish beti-cel as a durable, 1-time therapy that achieves TI, restores iron balance, and improves quality of life, offering a potentially curative treatment option for people with TDT.

This trial was registered at www.clinicaltrials.gov as NCT02633943.

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