Ex Vivo Fucosylation Of Cord Blood Accelerates Neutrophil and Platelet Engraftment

Cord blood transplantation (CBT) is an increasingly used alternative to bone marrow or peripheral blood stem cell transplantation, but is associated with slower neutrophil and platelet recovery. One strategy to overcome the delayed hematopoietic recovery of CB is to correct the decreased fucosylation of CB cell surface molecules which is thought to impair homing to the bone marrow of the limited numbers of stem and progenitor cells in the CB graft. Our pre-clinical murine xenograft models have demonstrated that human CB-derived progenitor cells treated with recombinant human fucosyltransferase-VI (ASC-101:America Stem Cell Inc.) prior to infusion resulted in more rapid and higher levels of human engraftment as compared to untreated CB progenitors (Robinson et al Exp Hematol, 2012). We therefore sought to study this novel strategy in a clinical trial where recipients with hematologic malignancies receive a double CBT where one CB unit is fucosylated prior to infusion.

In an effort to improve engraftment following cord transplant, we tested the ability of a 30-minute ex vivo fucosylation treatment to shorten time to neutrophil and platelet recovery.

Cell Processing: The unmanipulated CB unit with the highest total nucleated cell (TNC) dose was thawed, washed on the Sepax device (Biosafe) and infused first. The second CB unit which had the smaller TNC dose was thawed and washed using 10% Dextran-40/5% human serum albumin and the cells treated at 10⁶cells/ml for 30 minutes at room temperature with recombinant human fucosyltransferase VI (ASC-101) and substrate GDP-fucose (America Stem Cell Inc). The fucosylated cells were then washed on the Sepax and infused. After the procedure fucosylated (CD34+ CLA+) CD34+ cells increased from a median of 33% to 99%.

10 patients with AML (5), MDS (2), NHL (2), or HL (1) have been enrolled to date. Three patients are too early to evaluate engraftment; therefore, first 7 evaluable patients are reported here.

Median age was 55 (range 26 -62) years and median weight 87 (range 61-97) kg. All patients were conditioned with fludarabine 160mg/m², melphalan 140mg/m², and ATG 3mg/kg. Tacrolimus and MMF were used for GVHD prophylaxis.

Median time to absolute neutrophil count ≥ 0.5 X 10⁹ /L was 14 (range 12-28) days. Median time to platelet count ≥ 20 X 10⁹/L was 33 (range 18-100) days. One patient had secondary graft failure and was rescued with backup autologous stem cells. Four patients had engraftment of the fucosylated unit and 2 of the unfucosylated unit. Two patients developed grade 2 acute graft versus host disease. No infusion related toxicities were seen.

Ex vivo fucosylation appears to be a safe, simple and rapid approach to enhancing neutrophil and platelet engraftment in the setting of double cord transplantation. Accrual to the trial continues and updated results will be presented.

Miller:America Stem Cell Inc: Equity Ownership. Paradiso:America Stem Cell Inc: Equity Ownership. Koh:America Stem Cell Inc: Equity Ownership.