CD34+ cell engraftment, ex vivo expansion, and malignant cell depletion following immunomagnetic selection

This review describes the published preclinical and clinical data on the use of a manual or semiautomated immunomagnetic selection device, termed the Isolex system. Preclinical evaluation of hematopoietic progenitor cells (CD34+ cells) selected from bone marrow, peripheral blood leukapheresis products, and umbilical cord blood is reviewed with respect to differentiation (CFU-GM, BFU-E, and CFU-GEMM formation) and proliferation. The purities and yields of CD34+ cell products from clinical trials performed since 1994 are presented along with data on malignant cell depletion. On average, the Isolex system resulted in a final product median purity of 67% and a final product median yield of 64%. Positive selection of CD34+ cells with this device decreased residual tumor cell levels by 2-3 logs in autologous transplant products and reduced T cell levels by 3-4 logs in allogeneic grafts. To evaluate the clinical effect of these immunomagnetically selected cells, data on the rate of engraftment were reviewed. Autologous CD34+ cell transplantation resulted in recovery time from neutropenia (ANC > 500/microliter) of 9-14 days and recovery time from thrombocytopenia (platelet count > 20,000/microliter) of 10-20 days. These data showed that the Isolex system can positively select progenitor cells to reconstitute the hematopoietic system following myeloablative therapy.