Lentiviral vector ALS20 yields high hemoglobin levels with low genomic integrations for treatment of beta-globinopathies.

Ongoing clinical trials for treatment of beta-globinopathies by gene therapy involve the transfer of the beta-globin gene, which requires integration of three to four copies per genome in most target cells. This high proviral load may increase genome toxicity, potentially limiting the safety of this therapy and relegating its use to total body myeloablation. We hypothesized that introducing an additional hypersensitive site from the locus control region, the complete sequence of the second intron of the beta-globin gene, and the ankyrin insulator may enhance beta-globin expression. We identified a construct, ALS20, that synthesized significantly higher adult hemoglobin levels than those of other constructs currently used in clinical trials. These findings were confirmed in erythroblastic cell lines and in primary cells isolated from sickle cell disease patients. Bone marrow transplantation studies in beta-thalassemia mice revealed that ALS20 was curative at less than one copy per genome. Injection of human CD34+ cells transduced with ALS20 led to safe, long-term, and high polyclonal engraftment in xenograft experiments. Successful treatment of beta-globinopathies with ALS20 could potentially be achieved at less than two copies per genome, minimizing the risk of cytotoxic events and lowering the intensity of myeloablation.

Solid organ transplants following hematopoietic stem cell transplant in children.

SOT may be indicated for a select group of pediatric patients who experience permanent organ failure following HSCT. However, there is limited information available about outcomes. We identified eight children at our center who received an SOT following an HSCT. Patients were six months to 18 yr at HSCT. Diseases for which children underwent HSCT included thalassemia, Wiskott-Aldrich syndrome, Shwachman-Diamond/bone marrow failure, sickle cell disease (SCD), erythropoietic porphyria (EP), ALL, chronic granulomatous disease, and neuroblastoma. Time from HSCT to SOT was 13 days to seven yr (median, 27 months. Lung SOT was performed for two patients with BO, kidney transplants for three patients, and liver transplants for three patients (VOD, chronic GVHD). Seven patients are alive with functioning allografts 6-180 months from SOT. Advances in organ procurement, operative technique, immunosuppressant therapy, and infection control may allow SOT for a select group of patients post-HSCT. However, scarcity of donor organs available in a timely fashion continues to be a limiting factor. Children who have undergone HSCT and develop single organ failure should be considered for an SOT if there is a high likelihood of cure of the primary disease.