The clinical complications of sickle cell disease are due to the inherited abnormality of the oxygen-carrying hemoglobin protein in red blood cells (RBC). The RBC are made from stem cells in the bone marrow and transplantation of stem cells from the bone marrow of a healthy donor to someone with sickle cell disease (SCD) can lead to significant improvements in their health. However, most people do not have a matched sibling donor, and transplants from unrelated donors have higher risks for complications, mainly due to immune reactions between the donor and the recipient.
The goal of this project is to bring to the clinical trial of treating patients with SCD by transplanting them with their own bone marrow stem cells that have been modified in the laboratory by adding the gene for a version of human beta-globin that will act to inhibit sickling of the patient’s RBC (“anti-sickling” gene). This approach may provide a way to improve the health of people with SCD, with advantages over clinical treatments using transplantation of bone marrow stem cells from another person.
In the first 2 years of this project we were able to demonstrate the feasibility of this approach, i.e. that the clinical cell product, the subject’s bone marrow stem cells modified with the anti-sickling gene, can be produced suitably for clinical transplantation and that enough of the anti-sickling hemoglobin is made to reverse sickling of RBC made from the gene-modified stem cells.
Studies done by the Laboratory component of our Disease Team showed that the gene transfer lentiviral vector we developed to insert the anti-sickling gene into bone marrow stem cells met pre-set technical criteria for: the amount of vector that can be made, its efficiency to insert the anti-sickling gene into human bone marrow stem cells, the levels of anti-sickling beta-globin protein made by the vector in RBC, and the absence of adverse effects on the stem cells or their ability to make new RBC. These successful results allow advancement to the major lab focus for Year 3, safety studies to support an IND application.
The Clinical/Regulatory component of our Disease team established the proposed network of California clinical hematology sites to obtain bone marrow samples from volunteer donors with SCD for laboratory research studies on cell product development (UCLA, CHLA and CHRCO). We put into place the necessary IRB-approved protocols to collect bone marrow samples at these sites to use for the laboratory research at UCLA and USC. This network obtained its first BM sample from a SCD donor on 3/18/2010 and a total of 29 over 2 years. These patient-derived samples have been truly essential to the advancement of the laboratory work because bone marrow from SCD patients is needed for studies to measure expression of the anti-sickling gene and improvement in RBC sickling.
The Clinical Regulatory component has also produced a complete first draft of the clinical trial protocol, which defines which specific people with SCD would be eligible for participation in this study, and the exact approach of the clinical study, including how the patients will be evaluated before the procedure, the details of the bone marrow harvest, stem cell processing and transplant processes, and how the effects of the procedure will be assessed. This protocol was conceived with input from the Team of physicians and scientists with expertise in clinical and experimental hematology, bone marrow transplantation, transfusion medicine, gene therapy and cell processing laboratory methods, regulatory affairs, and biostatistics.
These efforts provided sufficient laboratory data and definition of the clinical approach that we could have a pre-IND meeting with the FDA (on 08/22/11). This interaction provided us the opportunity to receive guidance for three key areas that would comprise the IND application: the draft clinical protocol, the methods to make and characterize the gene-modified stem cell product for transplant, and the planned pre-clinical safety studies. The meeting was encouraging and informative.
In Year 3, our laboratory work will focus on performing pre-clinical safety studies (Toxicology study), qualifying end point assays and finalizing stem cell processing.