The past couple of years have been eventful for Bluebird Bio (BLUE -6.80%). In 2022, the gene-editing specialist earned approval for two therapies in the U.S.: Zynteglo, which treats the beta thalassemia (TDT) genetic blood condition, and Skysona, a treatment for cerebral adrenoleukodystrophy (CALD), an inherited disorder that attacks nerve sheaths in the brain. And last year, Bluebird Bio got the green light for yet another gene-editing treatment, Lyfgenia, which targets sickle cell disease (SCD). The appr ...