Rewriting the Hemoglobin Switch: CRISPR Targeting in Sickle Cell Disease

The RUBY trial demonstrates that disrupting the BCL11A binding site in the γ-globin promoters can normalize hemoglobin in severe sickle cell disease.

Background: The Problem Is Not Just the Mutation—It’s the Silencing of the Solution

Gene therapy for sickle cell disease has reached a transformative moment. Two hematopoietic stem-cell gene therapies are now FDA-approved—one introducing an antisickling HBB variant via lentiviral transfer, and another using CRISPR-Cas9 to disrupt the erythroid enhancer of BCL11A.1,2 These represent meaningful progress, but they also raise a critical question: can we intervene more directly—and more precisely—at the level of γ-globin regulation?