Donor Lymphocyte Infusion from G-CSF-Primed, Unmanipulated Whole Blood Is Safe and Improves Chimerism in HLA-Matched and Haploidentical Transplantation

Introduction: Donor lymphocyte infusion (DLI) is a useful therapy for mixed chimerism (MC) or measurable residual disease (MRD) after allogeneic hematopoietic cell transplantation (HSCT) in patients with malignancies, while it is less effective for overt relapse and is limited by graft-versus-host disease (GVHD). Multiple DLI products can be obtained from a single leukoapheresis without granulocyte-colony-stimulating factor (G-CSF) priming, while cryopreserving surplus is an alternative for peripheral blood grafts. The ideal DLI CD3+ cell dose remains undefined ranging from 1-500x10⁶/kg. However, leukoapheresis and cryopreservation are not risk-free, they are expensive and their costs prohibitive for many patients in developing countries. Furthermore, T-cell doses present in standard whole blood units can reach ≥1x10⁶/kg in healthy donors which can be further increased after G-CSF exposure. For these reasons we have used G-CSF-primed whole blood units (WB-DLI) in HLA-matched and haploidentical (Haplo) transplant recipients and report our single-center experience.

Methods: Patients ≥16 years of age who received WB-DLI at any time after HLA-matched related or Haplo peripheral blood HSCT due to relapse, MRD, MC or poor graft function were included from 2016-2018. Donors were stimulated with filgrastim 5 μg/kg every 24 hours for 3 days prior to donation. Standard pre-transfusion testing included major/minor crossmatch and flow cytometry analysis for lymphocyte subset quantification. The blood draw was performed on day 4 with the aim to collect 450 mL of whole blood in a standard collection bag. For patients with major and bidirectional ABO mismatch who had not undergone group switch or had a mixed population in solid-phase typing, a reactive major crossmatch was considered an absolute contraindication, while a reactive minor crossmatch was not. WB-DLI was infused fresh on the day of collection without manipulation in an outpatient basis. For relapsed patients, concurrent chemotherapy was administered on a case-by-case basis. Disease evaluation after relapse was performed on day +30 after treatment, while chimerism analysis was performed on day +60 through standard methods. GVHD prophylaxis was performed with oral cyclosporine A or tacrolimus and gradually tapered in a 60-day window.

Results: Fourteen patients received a single dose of WB-DLI, median age was 32 years (16-67), 50% were female. Most common diagnoses were acute lymphoblastic leukemia, (n=5) and acute myeloid leukemia (n=5), followed by myelodysplastic syndrome (n=2), non-Hodgkin lymphoma (n=1) and chronic myeloid leukemia (n=1). Nine patients received Haplo grafts, while 5 were HLA-matched. Three patients had previous GVHD inactive at the time of WB-DLI. Indication for WB-DLI was relapse for 6 patients, 3 had MRD while 5 remained in remission; one patient received WB-DLI due to poor graft function. Median chimerism at the time of WB-DLI was 72% (range 38-100%). A single infusion was administered in all cases. Median mononuclear cell count obtained was 32x10x⁶/kg (range, 9-74), while median CD3⁺ cell count was 6.7x10⁶/Kg (range 5.2-19). No immediate, severe adverse effects were observed. Febrile non-hemolytic transfusion reaction was documented in 4 cases after completing the procedure. No complications were observed in n=4 ABO mismatch cases including (n=2) major and bidirectional patients. Overall 50% of patients responded. Chimerism was improved in 50%, with a median increase of 28% (range 9-53%). Median post-DLI chimerism was 92.5% (range 20-100). Regarding patients treated for relapse or MRD, 3/9 patients responded (33%). Overall 8/14 patients eventually relapsed (57%) with a 12-month progression free survival of 27.5%, lower in relapsed/MRD positive patients (Figure I) (log rank test p=0.02 and 0.04, respectively). Overall survival at 12 months was 61.2%. Three patients developed acute GVHD, two of them grade III/IV in a median of 13 days (range 7-38). Four patients died due to relapse. Median follow-up after WB-DLI was 5 months (range 0.6-20.1 months). The cost of obtaining and administering WB-DLI was $350 USD per dose.

Conclusions: DLI obtained from unmanipulated, GCSF-primed whole-blood is a safe and affordable adoptive cell therapy. It is effective and improves mixed chimerism after HSCT, while it was less effective for overt relapse.

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