Gene therapy for the haemoglobinopathies has crossed a historic threshold — moving from clinical trials to approved, potentially curative treatments, including the first CRISPR-based medicine ever licensed.
Approved gene therapies
Exagamglogene autotemcel (exa-cel, Casgevy) uses CRISPR-Cas9 to edit the BCL11A enhancer in the patient's own stem cells, switching fetal hemoglobin production back on. In its pivotal trials, about 97% of sickle cell patients were free of severe vaso-occlusive crises for at least 12 months, and roughly 91% of transfusion-dependent β-thalassemia patients achieved transfusion independence. It was approved for sickle cell disease in December 2023 and for β-thalassemia in early 2024 — the first CRISPR gene-editing therapy ever approved. Lovotibeglogene autotemcel (lovo-cel, Lyfgenia), a lentiviral therapy that adds an anti-sickling β-globin gene, was approved for sickle cell disease at the same time (it carries a boxed warning for hematologic malignancy). Betibeglogene autotemcel (beti-cel, Zynteglo), a lentiviral β-globin gene-addition therapy, was approved earlier for transfusion-dependent β-thalassemia, with roughly 91% of patients achieving transfusion independence.
Practical realities
These therapies share two major limitations. Both require myeloablative busulfan conditioning, with its attendant cytopenias, infection risk, and infertility, and both are among the most expensive treatments ever marketed — so access, the conditioning burden, and long-term safety follow-up are the central challenges rather than efficacy. Alongside the curative approaches, the disease-modifying drug landscape continues to evolve, though not without setbacks — the sickle cell agent voxelotor was withdrawn globally in 2024 after post-marketing data raised safety concerns.
Further reading: exa-cel in sickle cell disease (Frangoul et al., NEJM 2024) and β-thalassemia (Locatelli et al., NEJM 2024); lovo-cel (Kanter et al., NEJM 2022); beti-cel (Locatelli et al., NEJM 2022); FDA approvals of Casgevy and Lyfgenia (2023–2024).