Emerging Gene Therapies in Sickle Cell Disease: A Comparative Review of Efficacy and Safety Against Standard Treatments.

Sickle cell disease (SCD) is an inherited haemoglobinopathy caused by a point mutation in the β-globin gene, resulting in abnormal sickle haemoglobin (HbS) and variable clinical expression ranging from mild to severe. While individuals with sickle cell trait are usually asymptomatic, those with homozygous disease may experience chronic haemolytic anaemia, recurrent vaso-occlusive crises, and progressive organ injury. Current standards of care, including hydroxyurea therapy, chronic blood transfusions, and allogeneic haematopoietic stem cell transplantation (HSCT), have substantially improved survival and reduced complications. However, each approach has limitations, such as incomplete disease control, toxicity, and limited donor availability. Recent advances in non-myeloablative and haploidentical HSCT have expanded curative options, achieving high survival with minimal graft-versus-host disease, though accessibility and cost remain challenges. Emerging gene therapies, particularly lentiviral vector-mediated gene addition and CRISPR-Cas9 genome editing, represent major progress by directly targeting the underlying genetic defect. These autologous approaches eliminate donor-related immune risks and have demonstrated durable haemoglobin correction, near-complete resolution of vaso-occlusive events, and encouraging outcomes in stroke prevention. This review synthesises evidence comparing gene therapies with standard treatments, outlining molecular mechanisms, efficacy, safety, and long-term considerations. Key challenges include stem-cell mobilisation, fertility preservation, conditioning toxicity, and equitable access. Early trials show substantial clinical benefit, improved quality of life, and favourable safety profiles. Emerging in vivo editing technologies may further simplify delivery and enhance global accessibility. Integrating gene therapy into evolving standards of care could transform SCD management, offering realistic prospects for durable remission or cure.