Abstract

Background

UCBT has proven effective in treating patients with hematologic malignancies (HM),but engraftment is slower and graft failure rates higher compared to other unrelated transplants. We have previously shown that incubation of UCB CD133+ cells with cytokines and the copper chelator TEPA (5µM), inhibits stem cell differentiation and results in a median of 89 and 30 fold expansion of CD34+ and CD34+CD38- cells, respectively (Cytotherapy 2004;6:344). Using this technology (StemEx®) we performed a prospective multicenter myeloablative UCBT trial in patients with HM.

Methodology

Patients were transplanted with a single CBU of which CD133+ cells from a segregated portion of the CBU (20-50%) were cultured for 21 days with hematopoietic cytokines and TEPA and transplanted along with a minimum of 107nucleated cells (NC)/kg from the un-manipulated (UM) portion of the same unit (NCT00469729). The primary endpoint of this study was 100 day overall survival. Using an intent to treat design, outcome was compared to a 2006-2010 double UCBT (dUCBT) control group (n = 295) collected from and by the CIBMTR and Eurocord registries using identical eligibility criteria to the StemEx® study: lack of a 5/6 or 6/6 matched sibling donor, age 12-55 years with high risk AML or ALL in 1stCR or subsequent, advanced CML or after failing TKI, MDS with Int-2 or high risk features or chemosensitive relapsed lymphoma. GvHD prophylaxis included a calcineurin inhibitor and mycophenolate mofetil. Comparison of the primary endpoint was based on a logistic regression model that adjusts the treatment comparison for imbalance between the groups in important prognostic factors found to impact mortality: age, sex, CMV status and disease risk.

Results

25 centers in US, EU and Israel enrolled 101 eligible patients between Oct 2007-Feb 2012 with AML-43, ALL-30, MDS and CML-8 each, and lymphoma-12. Median age was 37 (12.6-55.8); median weight was 68 kg (42.5-128.5). The baseline NC and CD34 cell dose/kg were 3.06 (1.29-11.0) x 107 and 1.64 (0.24-9.23) x 105. 70% of the units were matched at 4/6 loci. Median NC and CD34 fold expansion were 400 (0-764) and 77 (6-280), respectively. StemEx yielded a median of 14-fold increase in the number of CD34+ infused, in comparison to the number of CD34+ cells the patients could have received from the entire UM CBU. In total, patients received a median dose of 2.2 x 107 NC/kg and 9.7 x 105CD34/kg. No significant acute toxicity was seen with the expanded cell infusions.

The primary endpoint of this study has been met: 100 day survival was significantly higher in the StemEx® vs control group; 84.2 vs 74.6 % [95% CI 0.5 (0.26-0.95); p = 0.035]. Neutrophil and platelet engraftment rates were faster in the StemEx® vs control group: 21 vs 28 days (p< 0.0001) and 54 vs 105 days (p = 0.008), respectively. There was a trend in the reduction of engraftment failure from 14.4% in the control to 8.1% in the StemEx® group, p=0.086. Early engraftment (EE) (ANC ≤ day 20 and platelets ≤ day 60) was achieved more frequently in StemEx® (39.4%) than in the control arm (12.4%) , p<0.001. EE was associated with improved 100 day survival (p = 0.0028). Grade III/IV aGvHD and cGvHD rates did not differ between the study and control groups (19.4 vs 16.9%; p = 0.107) and 18.4 vs 16.0% (p = 0.731), respectively. Of the 101 patients, 16 patients died in the first 100 days. Causes of death were infection (5), multiorgan failure/ARDS (4), VOD (2) and relapse, acute GvHD, graft failure, hemorrhagic CVA and DIC (1 each). Importantly, the CD34+ cell dose from the StemEx expanded fraction was associated with time to ANC and platelet engraftment (p<0.001, 0.011, respectively) and inversely associated with grade III/IV infections during 100 day post-transplant (p = 0.023).

Conclusions

This multi-international study demonstrated the advantage of StemEx® over dUCBT historical controls,measured by a significant improvement in day 100 survival and faster engraftment of ANC and platelets. The robust associations obtained between CD34+ cell dose derived from the expanded portion and graft functionality provide additional support for the clinical benefit obtained over the dUCBT historical control arm. This technology holds the promise of increasing the number of UCBT being performed while potentially reducing its short term morbidity and mortality.

Disclosures:

Stiff:Gamida Cell Ltd: Consultancy, Honoraria, Research Funding. Peled:Gamida Cell: Employment. Landau:Gamida Cell Ltd: Employment. Rosenheimer:Gamida Cell Ltd: Employment. Mandel:Gamida Cell LTd: Employment. Hasson:Gamida Cell Ltd: Employment. Olesinski:Gamida Cell Ltd: Employment. Glukhman:Gmaida Cell Ltd: Employment. Snyder:Gamida Cell Ltd: Employment. Galamidi Cohen:Gamida Celll Ltd: Employment. Kidron:Gamida Cell Ltd: Employment. Bracha:Gamida Cell Ltd: Employment. Harati:Gamida Cell Ltd: Employment. Ben-Abu:Gamida Cell Ltd: Employment. Freind:Gamida Cell Ltd: Employment. Freedman:Gamida Cell Ltd: Consultancy. Olmer:Gamida Cell Ltd: Consultancy. Barishev:Gamida Cell Ltd: Consultancy. Nagler:Gamida Cell Ltd: Consultancy, Research Funding. Sanz:Gamida Cell Ltd: Consultancy, Honoraria, Research Funding.

Author notes

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Asterisk with author names denotes non-ASH members.