In 2020, Emmanuelle Charpentier and Jennifer Doudna were awarded the Nobel Prize in Chemistry for their research on the endonuclease, clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-associated protein 9 (CRISPR-Cas9) method for DNA editing. On 16 November 2023, the UK Medicines and Healthcare Products Regulatory Agency (MHRA) was the first to approve the CRISPR-Cas9 gene editing therapy, Casgevy (exagamglogene autotemcel), for the treatment of patients with transfusion-dependent b-thalassemia and the treatment of sickle cell disease in patients aged ≥12 years with recurrent vaso-occlusive crises. On 8 December 2023, the US Food and Drug Administration (FDA) approved both Casgevy and Lyfgenia (lovotibeglogene autotemcel) for patients with sickle cell disease. On 15 December 2023, the European Medicines Agency (EMA) approved Casgevy for sickle cell disease and transfusion-dependent ß-thalassemia. This Editorial aims to present an update on the landmark first regulatory approvals of CRISPR-Cas9 for patients with sickle cell disease and transfusion-dependent b-thalassemia and the potential challenges for therapeutic gene (DNA) editing.