Successful gene therapy for transfusion-dependent α-thalassemia: a case report

Clinical Snapshot

Key Findings

• P Value: Not reported — no formal statistical testing performed

• Effect Size: Mean haemoglobin ~90 g/L in months 12–24 without transfusion support; HbA fraction >85% of total haemoglobin

• Primary Outcome: Sustained transfusion independence achieved from week 4 post-infusion, maintained through 24 months of follow-up

• Nnt Or Sensitivity: Not calculable from n=1; vector copy numbers described as stable; no clonal dominance, insertional mutagenesis, or RCL detected at 24 months

• Confidence Interval: Not reported — single patient design precludes confidence interval calculation

Clinical Application

Currently limited to specialised academic gene therapy centres with lentiviral vector manufacturing capability, GMP-grade HSPC processing, and Phase I trial infrastructure. Not available as standard of care. Busulfan conditioning carries significant toxicity risk, particularly in adolescent females (gonadotoxicity). Requires long-term haematological and molecular surveillance. α-Thalassemia, including HbH disease, is a significant clinical burden in Australia, particularly in communities of Southeast Asian, Chinese, South Asian, and Pacific Islander heritage — populations well-represented in major metropolitan centres. The RACGP and RANZCOG recommend carrier screening in at-risk populations. Currently, no lentiviral gene therapy for α-thalassemia is TGA-registered or PBS-listed in Australia. The only approved gene therapy for haemoglobinopathy in Australia is betibeglogene autotemcel (Zynteglo) for β-thalassemia, which received TGA registration in 2023. Clinicians should be aware that this technology is at Phase I stage only; referral to clinical trial networks (e.g., ALLG, HSANZ) would be the appropriate pathway for eligible patients. Fertility preservation counselling prior to busulfan conditioning is mandatory under Australian reproductive medicine guidelines. Patients with transfusion-dependent α-thalassemia (specifically HbH disease genotypes) who lack a suitable HLA-matched allogeneic donor and are otherwise eligible for autologous HSPC gene therapy

Abstract

α-Thalassemia is a severe inherited hemoglobin (Hb) disorder with limited curative options for patients with transfusion dependency, lacking suitable donors. We report, to our knowledge, the first-in-human application of lentiviral vector-mediated α-globin gene therapy in a girl aged 14 years with transfusion-dependent HbH disease (--SEA/αCSα). Autologous CD34+ hematopoietic stem and progenitor cells were mobilized, collected, and genetically modified ex vivo using the lentiviral vector (Lenti-HBA) to restore α-globin expression, then reinfused after busulfan conditioning. The patient achieved engraftment within 3 weeks and started to be free of transfusions from the fourth week onward. In the last year of follow-up (months 12-24), the average Hb level remained at ∼90 g/L without transfusion support, with HbA accounting for >85% of total Hb. Vector copy numbers were stable, and no evidence of clonal dominance, insertional mutagenesis, or replication-competent lentivirus was detected. Adverse events (AEs) were limited to expected busulfan-related toxicities, including grade 2 menstrual irregularity and ovarian failure (serious AE). Despite cessation of chelation therapy, iron overload progressed minimally, and no cardiac iron deposition occurred. Immune recovery, growth, and development were preserved. This case demonstrates the feasibility, safety, and durable efficacy of lentiviral α-globin gene therapy as a potential curative treatment for transfusion-dependent α-thalassemia. This trial was registered at www.clinicaltrials.gov as NCT05851105.

References

1. 1.Yin, X., Qian, L., Dong, G., Chen, Y., Zhou, Y., Yang, B., Liao, G., Sun, H., Guo, H., Zeng, X., Zou, H., Ye, T., He, J., Yao, W., Ouyang, W., Zhang, X., & Liu, C. (2026). Successful gene therapy for transfusion-dependent α-thalassemia: a case report. Blood Advances. https://doi.org/10.1182/bloodadvances.2025019280