Background
Two single-arm Phase 3 studies. HGB-207 (Northstar-2): N=23 with transfusion-dependent β-thalassemia, non-β0/β0 genotype. HGB-212 (Northstar-3): N=22 with β0/β0 or IVS-I-110/β0 genotype. Betibeglogene autotemcel (beti-cel; Zynteglo): autologous HSCT with BB305 lentiviral vector encoding βA-T87Q globin. FDA approved Aug 17, 2022 for β-thalassemia requiring ≥4 pRBC units/yr; bluebird discontinued US operations April 2024.
Interventions and follow up
Treatment: Single IV infusion of beti-cel after myeloablative busulfan conditioning; HGB-207 enrolled non-β0/β0 (n=23), HGB-212 enrolled β0/β0 or IVS-I-110/β0 (n=22)
Primary endpoint: Transfusion independence (TI): Hgb ≥9 g/dL with no pRBC transfusions for ≥12 consecutive mo
Median follow-up: 29.5 mo (HGB-207), 13.5 mo (HGB-212)
Primary endpoint: Transfusion independence (TI): Hgb ≥9 g/dL with no pRBC transfusions for ≥12 consecutive mo
Median follow-up: 29.5 mo (HGB-207), 13.5 mo (HGB-212)
Results
Transfusion independence (HGB-207): 20/23 (89%); median Hgb 13.1 g/dL during TI period
Transfusion independence (HGB-212): 14/22 (64%); median Hgb 10.3 g/dL
HbA-T87Q: Median 10.3 g/dL (HGB-207); median 6.1 g/dL (HGB-212)
Transfusion burden: Eliminated in TI patients; ongoing in ~11–36% non-TI patients
Transfusion independence (HGB-212): 14/22 (64%); median Hgb 10.3 g/dL
HbA-T87Q: Median 10.3 g/dL (HGB-207); median 6.1 g/dL (HGB-212)
Transfusion burden: Eliminated in TI patients; ongoing in ~11–36% non-TI patients
Adverse events
Conditioning/HSCT-related: Febrile neutropenia, mucositis
Veno-occlusive disease: 3 patients (all resolved)
Delayed engraftment: 3 patients
Vector safety: No vector-related malignancies or off-target insertions detected
Discontinuation: Not applicable (one-time therapy)
Veno-occlusive disease: 3 patients (all resolved)
Delayed engraftment: 3 patients
Vector safety: No vector-related malignancies or off-target insertions detected
Discontinuation: Not applicable (one-time therapy)
Conclusions
Beti-cel achieved transfusion independence in 89% of non-β0/β0 and 64% of β0/β0 patients with transfusion-dependent β-thalassemia, with durable Hgb responses, supporting gene therapy as a potentially curative approach.
Key Limitations
Small single-arm studies, no randomized comparator. Lower TI rate in β0/β0 genotype (64%). Surrogate endpoints; HGB-212 follow-up short (13.5 mo). Myeloablative conditioning toxicity/infertility. Generalizability limited by stringent eligibility and need for adequate stem-cell mobilization.
Clinical Context
Supported FDA approval of Zynteglo (Aug 2022), first gene therapy for transfusion-dependent β-thalassemia. Positioned for patients lacking a matched related HSCT donor; competes with later CRISPR-based exa-cel. bluebird discontinued US commercial operations April 2024.