Sickle cell disease (SCD) results from an inherited mutation in the hemoglobin gene that causes red blood cells to “sickle” under conditions of low oxygen. It occurs with a frequency of 1/500 African-Americans, and is also common in Hispanic-Americans, who comprise up to 5% of SCD patients in California. The median survival based on 1991 national data was 42 years for males and 48 years for females. More recent data indicate that the median survival for Southern California patients with SCD is only 36 years, suggesting that serious problems exist regarding access to optimal medical care in this community. By twenty years of age, about 15% of children with SCD suffer major strokes and by 40 years of age, almost half of the patients have had central nervous system damage leading to significant cognitive dysfunction. These patients suffer recurrent damage to lungs and kidneys as well as severe chronic pain that impacts on quality of life. While current medical therapies for SCD can make an important difference in short-term effects, the progressive deterioration in organ function results in compromised quality of life and early deaths in ethnic populations who are generally adversely affected by health care disparity. Transplantation of bone marrow from a healthy donor as a source of new adult blood-forming (“hematopoietic”) stem cells can benefit patients with SCD, by providing a source for life-long production of normal red blood cells. However, bone marrow transplant is limited by the availability of well-matched donors and the problems that arise from immune reactions between the cells of the donor and the patient. Thus, despite major improvements in clinical care of SCD patients, SCD continues to be a major cause of illness and early death.
The stem cell therapy approach developed by this Disease Team will be used to treat patients with SCD by transplanting them with their own bone marrow adult hematopoietic stem cells that are genetically corrected by adding a novel therapeutic hemoglobin gene that blocks sickling of the red blood cells. This approach has the potential to permanently cure this debilitating and common illness with significantly less toxicity than with a bone marrow transplant from another person. A clinical trial using stem cell gene therapy for patients with SCD started in 2014 by this multi-disciplinary Disease Team, combining world-leading experts in stem cell gene therapy, clinical bone marrow transplantation and the care of patients with sickle cell disease. The first patient was enrolled and treatment started at the beginning of 2015. Successful use of stem cell gene therapy for sickle cell disease has the potential to provide a more effective and safe treatment for this disease to a larger proportion of affected patients.