Characteristics of CliniMACS® System CD34-enriched T cell-depleted grafts in a multicenter trial for acute myeloid leukemia-Blood and Marrow Transplant Clinical Trials Network (BMT CTN) protocol 0303

Abstract

Eight centers participated in the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) protocol 0303 to determine the effect of extensive T cell depletion (TCD) on the outcome of HLA matched sibling donor transplantation for acute myeloid leukemia. One goal of the study was to determine if TCD could be performed uniformly among study sites. TCD was achieved using the CliniMACS(®) CD34 Reagent System for CD34 enrichment. Processed grafts needed to contain ≥ 2.0 × 10(6) CD34(+)cells/kg with a target of 5.0 × 10(6) CD34(+) cells/kg and <10(5) CD3(+) T cells/kg. Up to 3 collections were allowed to achieve the minimum CD34(+) cell dose. In total, 86 products were processed for 44 patients. Differences in the starting cell products between centers were seen in regard to total nucleated cells, CD34(+) cells, and CD3(+) T cells, which could in part be ascribed to a higher dose of granulocyte-colony stimulating factor used for mobilization early in the trial. Differences between centers in processing outcomes were minimal and could be ascribed to starting cell parameters or to differences in graft analysis methods. Multivariate analysis showed that CD34(+) cell recovery (66.1% ± 20.3%) was inversely associated with the starting number of CD34(+) cells (P = .02). Median purity of the CD34 enriched fraction was 96.7% (61.5%-99.8%) with monocytes and B cells the most common impurity. All patients received the minimum CD34(+) cell dose, and 39 patients (89%) came within 10% or exceeded the target CD34(+) cell dose without exceeding the maximum T cell dose. All patients proceeded to transplantation and all achieved initial engraftment. Products processed at multiple centers using the CliniMACS System for CD34 enrichment were comparably and uniformly highly enriched for CD34(+) cells, with good CD34(+) cell recovery and very low CD3(+) T cell content.

Copyright © 2012 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1. Starting Product Characteristics by Center

Cellular content of the individual apheresis products undergoing CD34-enrichment for each participating center. (A) Starting TNC. (B) Starting absolute CD34+ cells. (C) Starting absolute CD3+ T cells. (D) % viable cells as measured by 7-AAD. The bars represent the median for each center. The half open half closed symbols represent products that were subsequently split for CD34-enrichment. Only significant differences between centers are shown. The overall p value for the comparison is shown in the lower right of each panel.

Figure 2. Effect of Wash Method Before and After CD34-Enrichment

Data are from 27 products processed by 3 centers using a Cobe 2991 cell washer for the platelet and antibody wash steps and 57 products processed by 5 centers using a bag method. Results were compared for the effect of the wash method on TNC and CD34+ cell recovery prior to addition onto the tubing set, and for CD34+ cell recovery and purity post enrichment, as well as for Log TCD. The only significant difference based on wash method was a higher CD34+ cell recovery after CD34-enrichment. Data are the mean ± sem of the two groups with the Bag method represented by the white bars and the Cobe 2991 method by the black bars.

Figure 3. Post Processing Outcomes by Center

Outcome after CD34-enrichment. (A) Recovery of CD34+ cells from starting product. (B) % of the CD34-enriched fraction that are CD34+. (C) Log depletion from starting CD3+ T cells. (D) 7-AAD viability of the CD34-enriched fraction. The bars represent the median for each center. The half open half closed symbols represent products that were subsequently split for CD34-enrichment. Only significant differences between centers are shown. The overall p value for the comparison is shown in the lower right of each panel.

Figure 4. Other Cellular Subsets Found in the CD34-enriched products

CD34-enriched fractions were assessed for other unwanted subsets including: CD3+ T cells (median 0.07%, range 0.0% to 2.6%, N=84), CD19 or CD20+ B Cells (median 0.28%, 0.0% to 7.4%, N=79), CD56+ NK cells (median 0.05%, range 0.0% to 21.3%, N=69), and CD14+ monocytes (median 0.5%, range 0.0% to 22.5%, N=65). The horizontal bar represents the median.