Abstract

CBT is frequently complicated by delayed and failed engraftment when compared to other sources of hematopoietic stem cell support. Strategies to improve engraftment include double CBT and ex-vivo expansion. We are comparing these approaches in a randomized, prospective fashion. Patients (N=71) were randomized to receive either two unmanipulated (UNM) CB units (N=36) or one UNM unit and one unit which was EXP ex-vivo (N=35). The majority of CB units were 4/6 HLA matches.

Methods: Diagnoses were AML/MDS (N=25; 35%), ALL(N=17; 24%), NHL(N=10; 14%), HD(N=7; 10%), CML (N=5; 7%), and CLL(N=7; 10%). Patients (Table 1) had primarily advanced disease, with a median of 3 (1–8) prior regimens including autotransplants in 22%. Preparative regimens included ATG and either myeloablative fludarabine plus dose-adjusted busulfan (N=13; myeloid diseases), or melphalan and thiotepa (N=28); patients not eligible for high-dose therapy received non-myeloablative fludarabine plus cyclophosphamide and 200 Gy TBI (=27) or melphalan (n=3). GVHD prophylaxis was tacrolimus plus either 3 doses of 5 mg/m2 methotrexate or MMF (table 1). Ex-vivo expansion: the smallest unit was CD133-selected using the CliniMACS device (day −14). The T cell-containing CD133-negative fraction was frozen. The CD133+ fraction was cultured for 14 days in media containing SCF, G-CSF and TPO. On day 0, the 2nd UNM unit was infused, followed by the CD133-negative and the EXP fractions.

Results. Infused median total nucleated cells (TNC)×107/Kg was 3.5 and 3.6, and median CD34×105/Kg was 1.8 and 1.1, respectively for EXP and UNM pts. Median TNC fold-expansion was 23 (0.44–275) and for CD34+ cells, 2.3 (0–957). The median ex-vivo fold expansion of patients that engrafted platelets was higher than patients that did not engraft (23 (range, 0.4–275) versus 9.3 (range, 1.1–63), P=0.4). Patients that received EXP cells and a reduced-intensity regimen engrafted neutrophils in a median of 7 days (range, 4–15 days; n=14) versus 14 days (range, 5–32 days; n=12) in the UNM arm (P=0.05). Thirty-four patients are alive (48%) with a median follow up of 11.3 mo (range, 2–49 months). Twenty-four patients have relapsed (34%). Chimerism analysis showed that ultimately one CB unit dominated in all patients, on both the UNM and EXP arms of the trial. For the EXP arm the majority of patients had evidence of expanded CB chimerism posttransplant ranging from 7–82%. In half of those patients, the expanded CB unit predominated over the unmanipulated unit for 2–12 months posttransplant (52–87%), followed by gradual predominance of the unmanipulated CB unit by 14 months in all patients.

Conclusion: Conclusion: EXP CBT was safe. The range of fold-expansion was highly variable. Accrual continues and we are focusing on strategies which improve CB expansion.

 Expanded Unmanipulated 
Complete remission at UCBT 41% 59% 0.09 
Median weight 85 (20–168) 76 (15–144) 0.18 
Median age 43 (4–70) 38.1 (2–73) 0.4 
Ablative preparative regimen 47% 68% 0.09 
GVHD prophylaxis with methotrexate 32% 30% NS 
Time to ANC500 (median/95%CI) 14 days (4–32) 17 (5–45)  
   0.2 
Proportion engrafting ANC500 80% 86%  
   NS 
Time to PLT20K (median/95%CI) 34 (4–70) 34 (27–134) NS 
Proportion engrafting PLT 69% 55% 0.2 
1-year survival 60% (40–75) 46% (27–63) 0.2 
2-year survival 55% 20% 0.1 
aGVHD gd II–IV/III–IV 43%/7% 43%/17% NS 
C.Incid. cGVHD 45% (28–78) 25% (15–65) 0.1 
C.Incid.: cumulative incidence    
 Expanded Unmanipulated 
Complete remission at UCBT 41% 59% 0.09 
Median weight 85 (20–168) 76 (15–144) 0.18 
Median age 43 (4–70) 38.1 (2–73) 0.4 
Ablative preparative regimen 47% 68% 0.09 
GVHD prophylaxis with methotrexate 32% 30% NS 
Time to ANC500 (median/95%CI) 14 days (4–32) 17 (5–45)  
   0.2 
Proportion engrafting ANC500 80% 86%  
   NS 
Time to PLT20K (median/95%CI) 34 (4–70) 34 (27–134) NS 
Proportion engrafting PLT 69% 55% 0.2 
1-year survival 60% (40–75) 46% (27–63) 0.2 
2-year survival 55% 20% 0.1 
aGVHD gd II–IV/III–IV 43%/7% 43%/17% NS 
C.Incid. cGVHD 45% (28–78) 25% (15–65) 0.1 
C.Incid.: cumulative incidence    

Disclosures: No relevant conflicts of interest to declare.

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