Sickle cell disease is the scourge of a person’s red blood cells. The inherited blood disorder, which disproportionately affects people in sub-Saharan Africa and India, can cause unbearable pain “crises” and extreme exhaustion. And until recently, there was no curative treatment. Now approved gene therapies for sickle cell disease (including sickle cell anemia, the most extreme form) and its milder cousin, beta-thalassemia, show enormous promise.
The therapies work by deactivating or replacing a hemoglobin gene so that a person’s body makes a healthy form instead of the telltale sickle-shaped red blood cells that define sickle cell disease or averting the red blood cell deficiency that causes beta-thalassemia.
At some point, all humans produce two forms of hemoglobin, the red blood cell protein that binds oxygen so it can be transported throughout the body: a fetal form, which is more efficient at extracting oxygen in the womb, and an adult form. After we’re born, our body switches from producing the fetal form to making the adult form.