PS1217 INTRA‐BONE DLI AT RELAPSE AFTER ALLO‐HSCT IMPROVES SURVIVAL WITH LOWERING OF PD‐1 POSITIVITY OF CD8+ CELLS AND PRESERVATION OF THE PROFILE OF TCR BETA DOMINANT CLONES IN THE MARROW

Abstract

Background:Immunologic surveillance of leukemia plays a role in consolidation of remission achieved by chemotherapy after relapse post alloHSCT. To augment this effect donor lymphocytes are infused intravenously in patients at risk. Intravenous injection does not facilitate an easy contact of infused lymphocytes with residual blasts and aGvHD is rather frequent. To address these issues, we started delivering donor lymphocytes directly to the bone marrow cavity (IB‐DLI) in patients post alloHSCT at relapse.Aims:The aim of this study was to follow fate of the patients after IB‐DLI and to correlate the effect with a profile and TCR beta clonotypes of lymphocytes residing in the marrow.Methods:Nine patients were studied (six with AML and three diagnosed with CLL or CMML or ALL; 5F/4 M, age from 22 to 64, median: 30 years), all relapsed from 6 to 83 months post alloHSCT. A genetic profile of a malprognosis prognosis was noted in 6 out 9 patients, frequently with multiple aberrations including: FLT3 ITD+, BCR/ABL b2a2, del 7q, TP53 del (17p13.1), del 13q, t(6;9), KMT2A (MLL) or MECOM aberration. Five patients received at relapse chemotherapy, two patients responded poorly and two were left without chemotherapy due to the poor biologic performance. All patients received IB‐DLI which in poorly responding to the primary chemotherapy patients was supported by 5′‐azacitidine (AML case) or Rituximab (CLL case) given between the subsequent IB‐DLI doses.One to 5 IB‐DLIs were given starting from 10E6 and ending with a dose of 10E8 of CD3+ cells/kg body weight. The leukophoretic products either unstimulated or stimulated (used for alloHSCT) were used as a source of lymphocytes. The cells were injected into the bone marrow cavity at the posterior iliac crest.The blood and marrow specimens were taken prior each IB‐DLI for: cytology, cytometry (including CD8, CD279, CD26, CD28 MoAb in addition to the routine staining used for blast cells), genetic work (TCR beta clonotyping, chimerism and the presence of mutations).Results:Altogether 25 IB infusions were performed which resulted in: (i) 5 out of 9 patients benefited from the procedure (responding patients), while in the 4 others the response was either transient (2 patients) or absent, (ii) The survival after the relapse was better in patients receiving than in those lacking IB‐DLI (p = 0.031), (iii) the numbers of CD8+CD69+ (1154 ± 244 vs. 186 ± 63 × 10E6 cells/L, p < 0.015) and CD8+PD‐1+ (1238 ± 476 vs. 255 ± 73 × 10E6 cells/L, p < 0.063) cells in the marrow prior to the IB‐DLI were higher in responding patients than in those in whom treatment failed, (iv) the proportions and the numbers CD8+PD‐1+ cells in the marrow decreased in responding patients (p < 0.043) but not in those in whom the procedure failed, (v) TCR beta V family clones usage was essentially the same in responding patients, 17 clones remained within the top five in the patients under the study. Among the clonotypes having their putative epitope already identified the most frequent were the clones referred as reacting with MART‐1.Summary/Conclusion:IB‐DLI was a safe and clinically effective procedure in relapsing post‐allo‐HSCT leukemic patients. The procedure benefited patients whose marrow had already prior to the IB‐DLIs attracted CD8+ cells and resulted in (1) reduction of proportions of PD‐1+ positive cells in CD8+ marrow cells and (2) supporting leading T cell clonotypes, and (3) longer survival of relapsing patients.