Flipping the fetal switch across β-hemoglobinopathies.

Liu et al. extend the application of transformer base editing of HBG1/2 promoters from transfusion-dependent β-thalassemia alone to one patient with sickle cell disease and three patients with geographically diverse β-thalassemia genotypes.1 The responses are meaningful, but scale, genomic surveillance, burden of cure, and access now define the translational test.