Allogeneic Hematopoietic Cell Transplantation From Combined Haploidentical Family Members and Unrelated Cord Blood (CB) Can Benefit High Risk Patients Lacking HLA-Identical Donors.
Authors: Rich Elizabeth Shima , Artz Andrew , Karrison Theodore , Godley Lucy A , Odenike Olatoyosi , Joseph Loren , Kline Justin , Nguyen Vu H. , Martinez Guadalupe , del Cerro Paula , Pape Lisa , Schroeder Linda , Allen Scott , Horowitz Sarah , Cunningham John , Larson Richard A. , Stock Wendy , Wickrema Amittha , van Besien Koen 
Published: October 2019

Abstract
Abstract 3378
Poster Board III-266

Introduction:
Haploidentical-cord blood transplantation is a promising approach for patients (pts) who lack HLA donors and may improve rates of early engraftment while allowing long term cord blood reconstitution with low rates of GVHD. We enrolled 29 pts (17 AML/MDS, 4 ALL, 3 CML, 4 NHL/HL, 1 severe aplastic anemia) lacking HLA identical donors. The median age was 40 years (range, 4-67), and median weight was 75 kg (range, 14-125). Twenty-two (76%) pts had active disease at time of transplant; 6 had prior autologous transplants. 14 pts were Caucasian; 15 were other race or ethnicity. The haploidentical donor was the mother in 4; father in 3; child in 10; sibling in 10; and half-sibling in 2 cases. The median haploidentical CD34+ dose was 2.51 × 106/kg (range, 1.25-10.95); CD3+ cells were 1.0 × 104/kg (range, 0.3-3.7). Single unrelated CB units were matched by low resolution at HLA-A and B and high-resolution at DRB1, and matched 6/6 in 2 pts; 5/6 in 18 pts; 4/6 in 9 pts. Median cord total nucleated cells equaled 1.93 × 107/kg (range, 1.07-9.36); CD34+ cells were 0.08 × 106/kg (range, 0.03-0.75). The conditioning regimen for 18 pts was fludarabine (Flu) (30 mg/m2 on d-7 through -3), melphalan (Mel) (70 mg/m2 on d -3 and -2), and Thymoglobulin (rATG) (1.5 mg/kg on d-7, -5, -3, -1). Eleven pts received Flu, thiotepa (5 mg/kg on d -7 and -6), total-body irradiation (TBI) (12 Gy lateral opposed fields in 2 Gy fractions BID on d-3 through -1), and rATG. GVHD prophylaxis consisted of tacrolimus (Tac) + methylprednisolone or Tac + mycophenolate.

Engraftment:
Two pts died early (sepsis, CVA). Three other pts failed to engraft with either haploidentical or CB and died of infection on d36, 43, and 63. One of these had anti-donor HLA antibodies. 24 pts engrafted with a median time to ANC >500/mL of 10 days (range, 9-31) and median time to sustained platelets >20,000/mL of 20 days (range, 15-63). In the majority of pts, early haploidentical engraftment was replaced by durable engraftment of CB by 100 days. However, 3 pts had persistent hematopoiesis associated with only the haploidentical donor, while a fourth pt engrafted with only CB on day 31. Late graft failure and death from sepsis occurred in one of the patients with haploidentical engraftment. In unfractionated peripheral blood or bone marrow cells, median haploidentical chimerism was 95% (range, 0-100) on d14; 76% (range, 0-95) on d30; 6% (range, 0-87) on d100. Median unfractionated cord chimerism was <5% (range, 0-100) on d14; 20% (range, 0-100) on d30; 85% (range, 0-100) on d100. In the CD3+ compartment, median haploidentical chimerism was 95% (range, 0-100) on d14; 86% (range, 0-95) on d30; 6% (range, 0-79) on d100. Median CD3+ cord chimerism was 5% (range, 0-100) on d14; 26% (range, 0-100) on d30; 90% (range, 1-100) on d100. Toxicities and outcome: Other fatal toxicities included VOD (1), EBV-associated PTLD (1), ARDS (1), cardiac arrest (1), intractable seizures (1). Two patients developed TTP and later died of complications related to sepsis. Five pts relapsed of whom 4 have died. Acute GVHD (aGVHD) grade II occurred in 3 pts, one of whom developed the only case of chronic GVHD after failing to continue prograf. No aGVHD grade III-IV was seen. Twelve pts are currently alive; 11 are without disease. The median follow up for survivors is 186 days (range, 16-642). Estimated one year survival is 26% (95%CI, 6-46), and PFS is 19% (1-36).

Conclusions:
Combined haploidentical and CB transplantation results in early haploidentical engraftment followed by durable CB predominance in a majority of pts. The median times to neutrophil engraftment are considerably shorter - and the range narrower - than with other methods of cord blood transplantation. Early haploidentical engraftment failed in four patients; cord blood engraftment also failed in three of these pts and in three others. Rates of acute and particularly of chronic GVHD are low. Durable remissions can be achieved even in high risk pts regardless of age or remission status at the time of transplant.

Disclosures:
Rich: Genzyme: Research Funding. Odenike:Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees. van Besien:Genzyme: Research Funding.