On December 8, 2023, the U.S. Food and Drug Administration (FDA) approved Casgevy™ and Lyfgenia™, the first cell-based gene therapies developed and approved for the treatment of sickle cell disease (SCD) in patients age 12 and older. SCD is a rare genetic disorder occurring most commonly in African Americans. The disease involves a mutation in hemoglobin, the protein in red blood cells that carries oxygen throughout the body, causing red blood cells to form a crescent or “sickle” shape, subsequently restricting blood flow in vessels. This restriction in blood flow, along with a lower capacity to carry oxygen, leads to diminished oxygen delivery to tissues throughout the body. Patients can experience pain, organ damage, life-threatening disabilities, early death and a greatly reduced quality of life. Both newly approved SCD therapies work by genetically modifying the patient’s blood stem cells. The modified stem cells are then transplanted back into the patient to multiply. Casgevy™ uses CRISPR/Cas9 technology to edit the mutated DNA to produce HbF, a type of hemoglobin that is effective in facilitating oxygen delivery and preventing the sickling of red blood cells. In an ongoing clinical trial, all patients treated with Casgevy™ achieved successful engraftment, meaning there were no failures or rejections of the edited blood stem cells infused back into the body. The most common side effects were nausea, abdominal pain, fever with low white blood cell count, headache, itching and reduced level of platelets. Lyfgenia™ also edits the DNA of blood stem cells, modifying them to produce HbAT87Q. This form of hemoglobin functions similarly to hemoglobin A, the normal functioning hemoglobin in adults not affected by SCD. In a clinical trial, 88% of participants treated with Lyfgenia™ achieved complete resolution of vaso-occlusive events (VOE-CR), indicating its effectiveness in reversing the blockage of blood vessels by sickle cells. The most common side effects included mouth sores and reduced levels of platelets, white blood cells and red blood cells. Lyfgenia™ has a black box warning for an increased risk of blood cancer which has occurred in some study participants. The approval of these two new drugs represents medical advancements of cell-based gene therapies as well as hope for improved quality of life in patients suffering from SCD. Both Casgevy™ and Lyfenia™ received Orphan Drug Fast Track, Priority Review and Regenerative Medicine Advanced Therapy designations.