Donor Lymphocyte Infusion Research Articles

Harnessing Immune Response in Acute Myeloid Leukemia.

Despite the results achieved with the evolution of conventional chemotherapy and the inclusion of targeted therapies in the treatment of acute myeloid leukemia (AML), survival is still not satisfying, in particular in the setting of relapsed/refractory (R/R) disease or elderly/unfit patients. Among the most innovative therapeutic options, cellular therapy has shown great results in different hematological malignancies such as acute lymphoblastic leukemia and lymphomas, with several products already approved for clinical use. However, despite the great interest in also expanding the application of these new treatments to R/R AML, no product has been approved yet for clinical application. Furthermore, cellular therapy could indeed represent a powerful tool and an appealing alternative to allogeneic hematopoietic stem cell transplantation for ineligible patients. In this review, we aim to provide an overview of the most recent clinical research exploring the effectiveness of cellular therapy in AML, moving from consolidated approaches such as post- transplant donor's lymphocytes infusion, to modern adoptive immunotherapies such as alloreactive NK cell infusions, engineered T and NK cells (CAR-T, CAR-NK) and novel platforms of T and NK cells engaging (i.e., BiTEs, DARTs and ANKETTM).

Prophylactic donor lymphocyte infusion after haploidentical hematopoietic cell transplantation and post-transplant cyclophosphamide for treatment of high-risk myeloid neoplasms in children: A retrospective study.

Post-transplant cyclophosphamide (PTCy) has been recommended for prevention of graft-versus-host disease (GvHD) following haploidentical hematopoietic cell transplantation (haplo-HCT) for treatment of malignant blood diseases, but disease relapse remains a problem. Although donor lymphocyte infusion (DLI) is reported to be effective for treating post-transplantation relapse, the efficacy and safety of prophylactic-DLI (pro-DLI) post haplo-HCT, and PTCy in pediatric patients with hematological malignancies is unknown. We retrospectively analyzed the outcomes of 54 pediatric patients with high-risk myeloid neoplasms who received a PTCy regimen for GvHD prophylaxis and pro-DLI after haploidentical peripheral blood stem cell transplantation. The high-risk myeloid neoplasms in this cohort included acute myeloid leukemia (n=46) and myelodysplastic syndromes (n=8). Median follow-up was for 19.7 (range: 3.4-46.6) months. The cumulative incidences of grade II-IV and III-IV acute GvHD were 37.0% (95% CI: 22.7%-48.7%) and 16.7% (95% CI: 6.1%-26.0%), respectively. There were no graft-failure events, and the 2-year rate of moderate/severe chronic GvHD was 8.1% (95% CI: 0%-16.7%). The 2-year non-relapse mortality, relapse, disease-free survival, GvHD-free relapse-free survival, and overall survival rates were 5.1% (95% CI: 0%-11.7%), 16.6% (95% CI: 5.3%-26.6%), 78.9% (95% CI: 68.0%-91.6%), 62.2% (95% CI: 49.4%-78.3%), and 87.3% (95% CI: 78.3%-97.4%), respectively. Prophylactic donor lymphocyte infusion in the setting of haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide appears to be effective and safe in pediatric patients with high-risk myeloid neoplasms.

Abstract 4 Excellent Event-Free-Survival and Immunoglobulin Independence for Patients with Severe Combined Immunodeficiency Transplanted with Umbilical Cord Blood Stem Cells

Abstract Introduction An HLA matched related donor (MRD) is the preferred donor source for performing a hematopoietic stem cell transplant (HSCT) in patients with severe combined immunodeficiency (SCID) (Heimall 2017). However, many patients lack an MRD and thus an alternative donor, must be used. In these situations, an umbilical cord blood (UCB) represents a promising stem cell source (Gragert 2014, Martinez 2022). Objectives The primary outcome of interest was one-year event free survival (EFS) and the secondary outcome was time to immunoglobulin therapy independence based on donor source. Methods All patients diagnosed with SCID who underwent HSCT at Texas Children’s Hospital from 2003 to 2021 were included. EFS was defined as survival 365 days post-transplant without additional transplant, stem cell “top-off”, or donor lymphocyte infusion. The date of last immunoglobulin infusion was recorded to track time to immunoglobulin therapy independence. Results A total of 67 patients were included in the cohort. One-year EFS was 74.25% for all patients using the Kaplan-Meier method. When stratified by donor/stem cell source, EFS was 88.94% for UCB, 72.92% for MRD, 60.00% for URD, and 41.67% for haplo. There was statistical significance in EFS between URD UCB and the haploidentical group (p = 0.0006). The median time to IVIG independence was 8.6 months for all patients, 7.3 months for UCB, 23.4 months for URD, 26.6 months for haplo, and 32.5 months for MRD. When stratified by donor/stem cell source, cumulative incidence analysis showed UCB patients achieved Immunoglobulin independence earlier when compared to all other groups (UCB vs haplo p = 0.0335, UCB vs MRD p = 0.0012, UCB vs URD p = 0.0488). Discussion This single-center cohort of 67 patients demonstrates excellent survival for SCID patients undergoing HSCT, confirming prior studies (Pai 2014, Heimall 2017). EFS was highest in patients treated with an UCBT. In our analysis of immune reconstitution, we found that SCID patients transplanted with UCB, had a significantly shorter time to IVIG independence compared to other stem cell donors/sources. Given the high survival of UCB patients and this robust immune reconstitution, UCB may represent the best alternative stem cell source for SCID patients without a MRD option.

Adoptive Immunotherapy via Donor Lymphocyte Infusions following Allogeneic Hematopoietic Stem Cell Transplantation for Myelofibrosis: A Real-World, Retrospective Multicenter Study

Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative option for Myelofibrosis (MF). Relapse however remains a significant problem in up to 20-30% of cases. Donor Lymphocyte Infusions (DLI) represent a potentially effective strategy for relapse prevention and management, but optimal timing based on measurable residual disease (MRD)/chimerism analyses and regimen choice remain undetermined. We performed a retrospective 'real world' analysis of a multicentre cohort of MF allo-HCT patients from 8 European transplant centres who received DLI between 2005-2022. Response was assessed using IWG-MRT defined response criteria, and survival endpoints were estimated using the Kaplan-Meier estimator and log-rank test. The study included 28 patients with a median age of 58 years and a Karnofsky performance status of >80. The majority of patients had DIPPS-plus Intermediate-2 or high-risk disease at the time of allo-HCT. In vivo T cell depletion was utilised in 20 (71.2%) cases, with 19/20 patients receiving anti-thymocyte globulin (ATG). Indication for DLI was either 'pre-emptive' (n=15), due to a decrease in recipient chimerism (n=13) or molecular relapse (n=2), or 'therapeutic' (n=13) for clinician-defined haematological/ clinical relapse. No patient received DLI prophylactically. Median time to DLI administration was 23.4 months post allo-HCT. Of the 16 patients receiving >1 dose of DLI, 12 were part of a planned escalating dose regimen. Median follow-up from time of 1st DLI administration was 55.4 months. Response rates to DLI were CR (n=9), PR (n=1), and clinical improvement (n=6). Chimerism levels improved in 16 patients, and stable disease was reported in 5 patients. No response or progression was reported in 7 patients. DLI-induced aGVHD was reported in 11 (39%) cases, grade 3/4 (n=7;25%). Median overall survival from time of 1st DLI was 62.6 months, and the cumulative incidence of relapse/progression after 1st DLI was 30.8% at 6 months. This study highlights that good response rates can be achieved with DLI even after frank relapse in some patients within a cohort where other treatment options are very limited. More prospective studies are warranted to identify the optimal DLI regimen and timing to improve patient outcomes.

FLT3 inhibitors as MRD-guided salvage treatment for molecular failure in FLT3 mutated AML

Patients with FLT3-mutated AML have a high relapse rate and suboptimal outcomes. Many have co-mutations suitable for measurable residual disease (MRD) monitoring by RT-qPCR and those destined to relapse can be identified by high or rising levels of MRD, called molecular failure. This provides a window for pre-emptive intervention, but there is little evidence to guide treatment. The use of FLT3 inhibitors (FLT3i) appears attractive but their use has not yet been evaluated. We identified 56 patients treated with FLT3i at molecular failure. The FLT3 mutation was an ITD in 52, TKD in 7 and both in 3. Over half of patients had previously received midostaurin. Molecular failure occurred at a median 9.2 months from diagnosis and was treated with gilteritinib (n = 38), quizartinib (n = 7) or sorafenib (n = 11). 60% achieved a molecular response, with 45% reaching MRD negativity. Haematological toxicity was low, and 22 patients were bridged directly to allogeneic transplant with another 6 to donor lymphocyte infusion. 2-year overall survival was 80% (95%CI 69–93) and molecular event-free survival 56% (95%CI 44–72). High-sensitivity next-generation sequencing for FLT3-ITD at molecular failure identified patients more likely to benefit. FLT3i monotherapy for molecular failure is a promising strategy which merits evaluation in prospective studies.

MRD as Biomarker for Response to Donor Lymphocyte Infusion after Allogeneic Hematopoietic Cell Transplantation in Patients with AML.

Donor lymphocyte infusions (DLIs) can directly target leukemic cells through a graft-versus-leukemia effect and play a key role in the prevention and management of relapse after allogeneic hematopoietic cell transplantation (alloHCT). Predictors of response to DLIs are not well established. We evaluated measurable residual disease (MRD) before, 30 and 90 days after DLI treatment as biomarkers of response. MRD was assessed by next-generation sequencing in 76 DLI-treated acute myeloid leukemia patients. MRD status before DLI treatment was independently prognostic for event-free survival (EFS, p < 0.001) and overall survival (OS, p < 0.001). Within 90 days of DLI treatment, 73% of MRD+ patients converted to MRD- and 32% of patients without remission achieved remission. MRD status 90 days after DLI treatment was independently prognostic for the cumulative incidence of relapse (CIR, p = 0.011) and relapse-free survival (RFS, p = 0.001), but not for OS. To evaluate the role of DLI treatment in MRD- patients, 23 MRD- patients who received DLIs were compared with a control cohort of 68 MRD- patients not receiving DLIs. RFS (p = 0.23) and OS (p = 0.48) were similar between the two cohorts. In conclusion, MRD is prognostic before (EFS, OS) and after (CIR, RFS) DLI treatment and may help in the selection of patients who benefit most from DLIs.

Joint models quantify associations between immune cell kinetics and allo-immunological events after allogeneic stem cell transplantation and subsequent donor lymphocyte infusion.

Alloreactive donor-derived T-cells play a pivotal role in alloimmune responses after allogeneic hematopoietic stem cell transplantation (alloSCT); both in the relapse-preventing Graft-versus-Leukemia (GvL) effect and the potentially lethal complication Graft-versus-Host-Disease (GvHD). The balance between GvL and GvHD can be shifted by removing T-cells via T-cell depletion (TCD) to reduce the risk of GvHD, and by introducing additional donor T-cells (donor lymphocyte infusions [DLI]) to boost the GvL effect. However, the association between T-cell kinetics and the occurrence of allo-immunological events has not been clearly demonstrated yet. Therefore, we investigated the complex associations between the T-cell kinetics and alloimmune responses in a cohort of 166 acute leukemia patients receiving alemtuzumab-based TCD alloSCT. Of these patients, 62 with an anticipated high risk of relapse were scheduled to receive a prophylactic DLI at 3 months after transplant. In this setting, we applied joint modelling which allowed us to better capture the complex interplay between DLI, T-cell kinetics, GvHD and relapse than traditional statistical methods. We demonstrate that DLI can induce detectable T-cell expansion, leading to an increase in total, CD4+ and CD8+ T-cell counts starting at 3 months after alloSCT. CD4+ T-cells showed the strongest association with the development of alloimmune responses: higher CD4 counts increased the risk of GvHD (hazard ratio 2.44, 95% confidence interval 1.45-4.12) and decreased the risk of relapse (hazard ratio 0.65, 95% confidence interval 0.45-0.92). Similar models showed that natural killer cells recovered rapidly after alloSCT and were associated with a lower risk of relapse (HR 0.62, 95%-CI 0.41-0.93). The results of this study advocate the use of joint models to further study immune cell kinetics in different settings.

Magnesium enhances the graft-versus-tumor effect of donor lymphocytic infusion on hematologic malignancies.

Donor lymphocyte infusion (DLI) cures relapsed hematologic malignancies after allogeneic hematopoietic stem cell transplantation through the graft-versus-tumor (GVT) effect. Although the important role of magnesium in enhancing immunity has been mentioned in studies, limited clinical data have explored how magnesium affects the efficacy of DLI. Besides, although laboratory data demonstrate that magnesium can enhance CD8+ T cells effector function, whether magnesium regulates the tumor killing effect of peripheral blood mononuclear cells (PBMCs) remains to be explored. Here, for the retrospective study, we collected clinical data of relapsed patients receiving DLI and explored the relationship between different serum magnesium levels and patient outcomes. For in vitro studies, we investigated the effect of magnesium on the cytotoxicity of DLI cells which were PBMCs and preliminarily explored the mechanism. Eighty-one patients were enrolled in this study. It was found that the high post-DLI magnesium level was significantly associated with a higher incidence of complete remission (CR) or partial remission (CR/PR) and a higher possibility of survival. The magnesium level after DLI was an independent risk factor of overall survival. In vitro studies proved that increased magnesium enhanced the cytotoxic function of PBMCs on hematologic malignancies. Besides, magnesium modulated LFA-1 headpiece opening. When blocking the integrin-ligand interaction between LFA-1 and ICAM-1, the regulation effect of magnesium on PBMCs was weakened. Therefore, it was possible that magnesium regulated PBMCs effector function by stimulating LFA-1. These results show that serum magnesium levels affect immunological responses mediated by donor lymphocytes in hematologic malignancies.

The graft-versus-leukemia effect of prophylactic donor lymphocyte infusions after allogeneic stem cell transplantation is equally effective in relapse prevention but safer compared to spontaneous graft-versus-host disease.

Therapeutic donor lymphocyte infusions (tDLI) are used to reinforce the graft-versus-leukemia (GvL) effect in relapse after allogeneic stem cell transplantation (alloSCT). In contrast, the role of prophylactic DLI (proDLI) in preventing leukemia relapse has been less clearly established, although supported by retrospective, case-control, and registry analyses. We report a prospective, monocentric, ten year cohort of patients with high risk acute leukemias (AL) or myelodysplasia (MDS) in whom proDLI were applied beyond day +120 post alloSCT to compensate for lack of GvL.272 consecutive allotransplanted AL or MDS patients in complete remission and off immunosuppression at day +120 were stratified according to the prior appearance of relevant GvHD (acute GvHD °II-IV or extensive chronic GvHD) as a clinical indicator for GvL. Escalating doses of unmodified proDLI were applied to 72/272 patients without prior relevant GvHD. Conversely, 157/272 patients with prior spontaneous GvHD did not receive proDLI, nor did 43/272 patients with contraindications (uncontrolled infections, patient refusal, DLI unavailability).By day 160-landmark analysis (median day of first DLI application), proDLI recipients had significantly higher five-year overall (OS) and disease free survival (DFS) (77% and 67%) than patients with spontaneous GvHD (54% and 53%) or with contraindications (46% and 45%) (p=0.003). Relapse incidence for patients with proDLI (30%) or spontaneous GvHD (29%) was significantly lower than in patients with contraindications (39%; p=0.021). With similar GvHD incidence beyond day +160, non-relapse mortality (NRM) was less with proDLI (5%) than without proDLI (18%; p=0.036).In conclusion, proDLI may be able to compensate for lack of GvL in alloSCT recipients with high risk AL or MDS.

Fludarabine, cytarabine, and idarubicin with or without venetoclax in patients with relapsed/refractory acute myeloid leukemia.

Treatment options for relapsed and refractory acute myeloid leukemia patients (R/R AML) are limited. This retrospective cohort study compares safety and efficacy of fludarabine, cytarabine, and idarubicin (FLA-IDA) without or with venetoclax (FLAVIDA) in patients with R/R AML. Thirty-seven and 81 patients received one course FLA-IDA with or without a 7-day course of venetoclax, respectively. The overall response rate (ORR) was significantly higher in FLAVIDA compared to FLAIDA- treated patients (78% vs. 47%; P=0.001), while measurable residual disease was negative at a similar proportion in responding patients (50% vs. 57%), respectively. Eighty-one percent and 79% of patients proceeded to allogeneic hematopoietic cell transplantation or donor lymphocyte infusion after FLAVIDA and FLA-IDA, respectively. Event-free and overall survival were similar in FLAVIDA- and FLA-IDA-treated patients. Refractory patients could be salvaged more successfully after FLA-IDA compared to FLAVIDA pretreatment. Neutrophil and platelet recovery times were similar in the venetoclax and the control group. In conclusion, short-term venetoclax in combination with FLA-IDA represents an effective treatment regimen in R/R AML identifying chemosensitive patients rapidly and inducing measurable residual disease-negative remission in a high proportion of R/R AML patients.

Selected memory T cells infused post haploidentical hematopoietic stem cell transplantation persist and hyper-expand.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplant cyclophosphamide is a curative treatment for many hematological malignancies, yet a majority of patients still suffers from recurrent infections. Post-transplant infusion of memory T cells could potentially enhance immunological protection without increasing the risk of eliciting acute graft-versus-host disease, which is mainly induced by naïve T cells. Here, we performed longitudinal analysis of the lymphocyte compartment in 19 haplo-HSCT patients previously enrolled in a phase II prospective clinical trial (ClinicalTrials.gov Identifier: NCT04687982), in which they received post-transplant CD45RA-depleted donor lymphocyte infusions (DLI). T cell receptor sequencing analysis showed that, surprisingly, CD45RA-depleted DLI do not increase T cell clonal diversity, but lead to prominent expansion of a selected number of infused memory T cell clones, suggestive of recruitment of these cells in the immune response. Pathogen-specific memory T cells, including cytomegalovirus (CMV)-specific cells, engrafted and were able to persist for at least one month. Deep immunophenotyping revealed strong polyfunctional effector CMV-specific T cell responses in the majority of patients, with their expansion correlating with the frequency of CMV-specific cells in the donor. These findings provide a rationale behind the suggested improved protection against viral infections for patients receiving CD45RA-depleted DLI.

Donor-derived CAR-T therapy improves the survival of relapsed B-ALL after allogeneic transplantation compared with donor lymphocyte infusion.

Chimeric antigen receptor (CAR)-T cell therapy revolutionized treatment for various hematologic malignances. However, limited studies were reported to compare the efficacy and safety of CAR-T and donor lymphocyte infusion (DLI) for patients with relapsed B-cell acute lymphoblastic leukemia (B-ALL) after hematopoietic stem cell transplantation (HSCT) comprehensively. We conducted a single-center, retrospective comparative study that consisted of 12 patients who were treated with DLI (control group) and 12 patients treated with donor-derived CD19 CAR-T cells (experimental group, 6 patients also received CD22 or CD123 CAR-T cells sequentially) with 3 overlaps. The event-free survival (EFS) of patients in experimental group was superior to that of the control group: 516days versus 98days (p = 0.0415). Compared with 7 of 12 patients treated with DLI suffered grades III-IV acute graft versus host disease (aGVHD), one grade III aGVHD developed in patients treated with CAR-T therapy. No significant difference in the incidence of infection was identified between these two groups. Most patients in the experimental group had only mild cytokine release syndrome and none developed neurotoxicity. The univariate analysis of patients in the experiment group revealed that earlier CAR-T therapy for post-transplantation relapse was associated with better EFS. There was no significant difference in EFS between patients treated with dual-target CAR-T with those with single CD19 CAR-T. In this study, our data supported that donor-derived CAR-T therapy is a safe and potentially effective treatment for relapsed B-ALL after HSCT and may be superior to DLI.

Donor Lymphocyte Infusion and Molecular Monitoring for Relapsed Myelofibrosis After Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is a curative approach for myelofibrosis patients, but relapse is a major cause of treatment failure. We investigated the effect of donor lymphocyte infusion (DLI) in 37 patients with molecular (n = 17) or hematological relapse (n = 20) after HCT. Patients received median of 2 (range, 1–5) cumulative DLI (total of 91 infusions). Median starting dose was 1 × 106 cells/kg, escalated by half-log ≥6 weeks if no response nor graft-versus-host disease (GvHD) occurred. Median time to first DLI was 40 weeks for molecular relapse versus 145 weeks for hematological relapse. Overall molecular complete response (mCR) at any time was 73% (n = 27) and was significantly higher for initial molecular relapse (88%) versus hematological relapse (60%; P = 0.05). The 6-year overall survival was 77% versus 32% (P = 0.03). Acute GvHD 2–4 occurred in 22% and half of the patients achieved mCR without any GvHD. All patients who relapsed from mCR achieved after first DLI could be salvaged with subsequent DLI, showing long-term survival. No second HCT was needed for molecular relapse versus 6 for hematological relapse. This comprehensive and largest study to date suggests molecular monitoring together with DLI as standard of care and a crucial approach to achieve excellent outcomes in relapsed myelofibrosis.

Donor-derived CD19 CAR-T Cells versus Chemotherapy Plus Donor Lymphocyte Infusion for Treatment of Recurrent CD19-positive B-ALL After Allogeneic Hematopoietic Stem Cell Transplantation.

This study aimed to compare the efficacy of anti-CD19 chimeric antigen receptor T cells (CAR-T cells) versus chemotherapy plus donor lymphocyte infusion (chemo-DLI) for treating relapsed CD19-positive B-cell acute lymphoblastic leukemia (B-ALL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Clinical data of 43 patients with B-ALL who relapsed after allo-HSCT were retrospectively analyzed. Twenty-two patients were treated with CAR-T cells (CAR-T group), and 21 with chemotherapy plus DLI (chemo-DLI group). The complete remission (CR) and minimal residual disease (MRD)-negative CR rates, leukemia-free survival (LFS) rate, overall survival (OS) rate, and incidence of acute graft-versus-host disease (aGVHD), cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were compared between the two groups. The CR and MRD-negative CR rates in the CAR-T group (77.3% and 61.5%) were significantly higher than those in the chemo-DLI group (38.1% and 23.8%) (P=0.008 and P=0.003). The 1- and 2-year LFS rates in the CAR-T group were superior to those in the chemo-DLI group: 54.5% and 50.0% vs. 9.5% and 4.8% (P=0.0001 and P=0.00004). The 1- and 2-year OS rates in the CAR-T versus chemo-DLI group were 59.1% and 54.5% vs. 19% and 9.5% (P=0.011 and P=0.003). Six patients (28.6%) with grade 2-4 aGVHD were identified in the chemo-DLI group. Two patients (9.1%) in the CAR-T group developed grade 1-2 aGVHD. Nineteen patients (86.4%) developed CRS in the CAR-T group, comprising grade 1-2 CRS in 13 patients (59.1%) and grade 3 CRS in 6 patients (27.3%). Two patients (9.1%) developed grade 1-2 ICANS. Donor-derived anti-CD19 CAR-T-cell therapy may be better, safer, and more effective than chemo-DLI for B-ALL patients who relapse after allo-HSCT.

Azacitidine, lenalidomide and donor lymphocyte infusions for relapse of myelodysplastic syndrome, acute myeloid leukemia and chronic myelomonocytic leukemia after allogeneic transplant: the Azalena-Trial.

Azacitidine combined with donor lymphocyte infusions (DLI) is an established treatment for relapse of myeloid malignancies after allogeneic transplantation. Based on its immunomodulatory and anti-leukemic properties we considered Lenalidomide to act synergistically with Azacitidine/DLI to improve outcome. We therefore prospectively investigated tolerability and efficacy of this combination as first salvage therapy for adults with post-transplant relapse of AML, MDS and CMML. Patients were scheduled for 8 cycles Azacitidine (75 mg/m2 day 1-7), Lenalidomide (2.5 or 5mg, day 1-21) and up to 3 DLI with increasing T cell dosages (0.5×106-1.5×107 cells/kg). Primary endpoint was safety, while secondary endpoints included response, graft-versus-host disease (GvHD) and overall survival (OS). Fifty patients with molecular (52%) or hematological (48%) relapse of MDS (n=24), AML (n=23) or CMML (n=3) received a median of 7 (range, 1 to 8) cycles including 14 patients with 2.5mg and 36 with 5mg Lenalidomide daily dosage. Concomitantly, 34 patients (68%) received at least one DLI. Overall response rate was 56% and 25 patients (50%) achieved complete remission being durable in 80%. Median OS was 21 months and 1-year OS rate 65% with no impact of type of or time to relapse and Lenalidomide dosages. Treatment was well tolerated indicated by febrile neutropenia being the only grade ≥3 non-hematologic adverse event in >10% of patients and modest acute (grade II-IV 24%) and chronic (moderate/severe 28%) GvHD incidences. In summary, Lenalidomide can be safely added to Azacitidine/DLI without excess of GvHD and toxicity. Its significant anti-leukemic activity suggests that this combination is a novel salvage option for post-transplant relapse. (NCT02472691).

SINGLE AGENT BRENTUXIMAB VEDOTIN AS BRIDGE TO ALLOGENEIC STEM CELL TRANSPLANT IN ADOLESCENTS WITH RELAPSED ANAPLASTIC LARGE CELL LYMPHOMA (ALCL): THE UCLH EXPERIENCE

Introduction: Optimal treatment for relapsed ALCL in children and adolescents is still subject of debate. We present here the results of our salvage strategy in the TYA Unit at UCLH, using single agent brentuximab vedotin (BV) as bridge to allogeneic stem cell transplant (alloHSCT). Methods: Between 2011 and 2021 we treated 7 patients with relapsed ALCL; all patients had received first line treatment according to ALCL99 guidelines. All relapses were biopsy proven and centrally reviewed if not performed at UCLH. Brentuximab Vedotin was given at the standard dose of 1.8mg/kg intravenously every 3 weeks. Results: All 7 patients were male; median age at diagnosis was 16 (range 13–19). Baseline characteristics were as follows: 7/7 were CD30+, 3/7 were CD3+, 6/7 biopsies were ALK positive, and 3/7 presented with a small cell/lymphohistiocitic (SC/LH) pattern. Six/7 patients had stage IV disease, 4/7 had skin involvement, bone marrow involvement was seen in 3/7 cases (infiltrate between 2 and 10%); 1/7 patients had bulky disease. Of the 7 patients, 3 had primary progressive disease, while 4/7 patients initially achieved a complete metabolic response (CMR), but had a very early relapse, between 2 and 3 months after completion of treatment. 6/7 patients received BV as first line of salvage treatment, 1 as second salvage, after failing ICM (ifosfamide, carboplatin, mitoxantrone), which was still our standard of care in 2011. Median number of doses of BV received was 3 (range 2–5); 6/7 (86%) patients obtained a complete metabolic remission, after a median of 3 doses (range 3–5). One patient progressed on BV; after failing crizotinib he achieved CMR with vinblastine-dexamethasone, then proceeded to transplant and is in long term remission. All 6 patients who achieved a complete remission after BV proceeded to alloHSCT, 1/6 from fully matched sibling donor, 3/6 from haploidentical donors, 2/6 from matched unrelated donors. Conditioning regimen was myeloablative for 5/6 patients, using Cyclophosphamide/total body irradiation +/- Campath depending on donor source; one patient received intermediate intensity conditioning with BEAM (BCNU, etoposide, cytarabine, melphalan)-Campath. With a median follow up of 55 months (range 4–133), all 6 patients are alive and 5/6 (83%) remain in remission with no need for further treatment; 1/6 patients relapsed 8 months post-transplant. This patient was re-challenged with BV, with the addition of donor lymphocytes infusions (DLI) and achieved a complete remission. Conclusions: Salvage treatment with single agent BV followed by alloHSCT is effective in adolescents with relapsed ALCL and lead to durable responses in a cohort of patients with high prevalence of high-risk features (advanced stage, SC/LH pattern, CD3+, early relapse after first line treatment). Interestingly, in one patient who relapsed after alloHSCT, BV and DLI were successful in inducing another complete remission. Keywords: Molecular Targeted Therapies, Non-Hodgkin (Pediatric, Adolescent, and Young Adult), Stem Cell Transplant No conflicts of interests pertinent to the abstract.

Efficacy of CLAE Chemotherapy Regimen Followed by Allogeneic Hematopoietic Stem Cell Transplantation in Patients with Relapsed/Refractory Acute Leukemia

To observe the efficacy and safety of CLAE intensive chemotherapy followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with relapsed/refractory acute leukemia (R/R AL). CLAE regimen [cladribine 5 mg/(m2·d), d 1-5; cytarabine 1.5 g/(m2·d), d 1-5; etoposide 100 mg/(m2·d), d 3-5] followed by allo-HSCT was used to treat 3 R/R AL patients. The patients received CLAE chemotherapy in relapsed or refractory status and underwent bone marrow puncture to judge myelodysplastic state. After an interval of 3 to 5 days, followed by preconditioning regimen for allo-HSCT [fludarabine 30 mg/(m2·d), d -7 to d -3; busulfan 0.8 mg/kg q6h, d -6 to d -3 or d -5 to d -2. If the bone marrow hyperplasia was not active and the blasts were less than 10%, busulfan should be used for 3 days. If the bone marrow hyperplasia was active and the blasts were more than 10%, busulfan should be used for 4 days]. Cyclosporin A, mycophenolate mofetil and short-term methotrexate were used for graft-versus-host disease (GVHD) prevention. After transplantation, the status of minimal residual disease (MRD) and bone marrow chimerism were regularly monitored in all 3 patients, and demethylation drugs or dasatinib were used to prevent recurrence 3 months after transplantation. 2 patients with t(11;19) translocation and relapse/refractory acute myeloid leukemia recurred within 6 months after induction of remission, and received intensive chemotherapy with CLAE regimen followed by haploidentical allo-HSCT and unrelated donor allo-HSCT, respectively. The two patients both relapsed 6 months after transplantation, then achieved complete remission by donor lymphocyte infusion, interferon, interleukin-2 and other methods, and disease-free survival was 2 years after transplantation. The other patient was chronic myelogenous leukemia who developed acute lymphoblastic leukemia during oral administration of tyrosine kinase inhibitor, accompanied by T315I and E255K mutations in ABL1 kinase region and additional chromosomal abnormalities. After morphological remission by induction chemotherapy, central nervous system leukemia was complicated. Intensive chemotherapy with CLAE regimen followed by sibling allo-HSCT was performed in the positive state of MRD. The patient relapsed 3 months after transplantation, and achieved remission after chimeric antigen receptor T-cell (CAR-T) therapy, however, he died 5 months after transplantation because of severe cytokine release syndrome (CRS) and GVHD. CLAE regimen followed by allo-HSCT may be an effective salvage treatment option for R/R AL patients to prolong the overall survival.

Venetoclax durable response in adult relapsed/refractory Philadelphia-negative acute lymphoblastic leukemia with JAK/STAT pathway alterations.

High-risk relapsed/refractory adult Philadelphia-negative (Ph-) B-cell acute lymphoblastic leukemia (B-ALL) is a great challenge due to limited possibilities to achieve and maintain a complete response. This also applies to cases with extramedullary (EM) involvement that have poor outcomes and no accepted standard therapeutic approaches. The incidence of EM localization in relapsed/refractory B-ALL is poorly investigated: data on patients treated with blinatumomab reported a 40% rate. Some responses were reported in EM patients with relapsed/refractory B-ALL treated with inotuzumab ozogamicin or CAR-T. However, molecular mechanisms of response or refractoriness are usually investigated neither at the medullary nor at EM sites. In the complex scenario of pluri-relapsed/refractory B-ALL patients, new target therapies are needed. Our analysis started with the case of an adult pluri-relapsed Ph- B-ALL patient, poorly sensitive to inotuzumab ozogamicin, donor lymphocyte infusions, and blinatumomab in EM disease, who achieved a durable/complete response after treatment with the BCL2-inhibitor venetoclax. The molecular characterization of medullary and EM samples revealed a tyrosine kinase domain JAK1 mutation in the bone marrow and EM samples at relapse. By comparing the expression level of BCL2- and JAK/STAT pathway-related genes between the patient samples, 136 adult JAK1 wt B-ALL, and 15 healthy controls, we identified differentially expressed genes, including LIFR, MTOR, SOCS1/2, and BCL2/BCL2L1, that are variably modulated at diverse time points and might explain the prolonged response to venetoclax (particularly in the EM site, which was only partially affected by previous therapies). Our results suggest that the deep molecular characterization of both medullary and EM samples is fundamental to identifying effective and personalized targeted therapies.

Immunotherapy with cure potential of multi-drug resistant hematologic malignancies using IL-2 preactivated intentionally mismatched donor lymphocyte

PurposeUnfortunately, cure of multi-drug resistant (MDR) hematologic malignancies remains an unmet need. Donor lymphocyte infusion (DLI) following allogeneic stem cell transplantation (SCT) can sometimes eliminate multi-drug resistant leukemia but at a risk of acute and chronic graft-vs-host disease (GVHD) and procedure-related toxicity. Supported by pre-clinical experiments in animal models, we hypothesized that immunotherapy induced by non-engrafting intentionally mismatched IL-2 activated killers (IMAK) including both T & NK cells could induce safer, faster and much more effective immunotherapy while avoiding the need for SCT and the risks of GVHD.MethodsIMAK treatment was applied in 33 patients with MDR hematologic malignancies conditioned with cyclophosphamide 1000 mg/m2 based protocol. Haploidentical or unrelated donor lymphocytes were preactivated with IL-2 6000 IU/ml for 4 days. IMAK was combined with Rituximab in 12/23 patients with CD20+ B cells.ResultsA total of 23/33 patients with MDR (4 failing SCT) achieved complete remission (CR). First patient currently 30 years with no further treatment and 6 observed for > 5 years (2 AML; 2 multiple myeloma, 1 ALL & 1 NHL) can be considered cured. No patient developed > grade 3 toxicity or GVHD. No residual male cells were detectable among six females treated with male cells beyond day + 6, confirming that GVHD was prevented by consistent early rejection of donor lymphocytes.ConclusionsWe hypothesize that safe and superior immunotherapy of MDR with cure potential may be accomplished by IMAK, most probably in patients with low tumor burden, but that remains to be confirmed by future clinical trials.

Allogeneic Hematopoietic Stem Cell Transplantation for Primary Myelofibrosis: A 20-year Experience in a Single Center

Allogeneic hematopoietic stem cell transplantation is a well-established approach for patients diagnosed with primary myelofibrosis and remains the only potentially curative treatment. To present the overall outcome of patients with myelofibrosis treated with allogeneic hematopoietic stem cell transplantation. A retrospective cross-sectional study. This study is a retrospective analysis of 26 consecutive patients with primary myelofibrosis who underwent transplantation at our center between January 2002 and January 2022. Disease and transplant variables contributing to outcomes were analyzed. The median age at the time of transplantation was 52.5 (range, 32-63) years and the median time from diagnosis to allogeneic hematopoietic stem cell transplantation was 25 (range, 3.1-156.8) months. Myeloablative conditioning and reduced-intensity conditioning regimens were used in 8 (30.8%) and 18 (69.2%) transplantations, respectively. Neutrophil and platelet engraftment was achieved in 23 patients at a median follow-up of 21.2 months (range, 12 days to 234.8 months). Primary graft failure occurred in 1 of 23 patients (4.3%). Neutrophil and platelet engraftment occurred at a median of 16 (range, 12-39) days and 20 (range, 11-78) days, respectively. Acute graft-versus-host disease was seen in 11 of 22 patients engrafted allografts, of which 7 (31.8%) were grade 3-4 acute graft-versus-host disease. Eight patients (36.4%) developed chronic graft-versus-host disease, and three cases were extensive. Four patients (19%) relapsed after a median of 5.5 months, and three patients received donor lymphocyte infusion. The 3-year overall survival rate of the entire study population was 46.2%. The median overall survival was not reached in the myeloablative conditioning group; however, it was 11.9 months in the reduced-intensity conditioning group (p =0.3). According to the donor graft source, the median overall survival was 0.73 months in mismatched unrelated graft recipients, 12 months in matched sibling donors, and not reached in matched unrelated graft recipients (p = 0.03). The 3-year progression-free survival rate of patients who survived > 100 days was 74.7%. The effect of JAK-2 status, graft source, conditioning regimen or dynamic international prognostic scoring system on progression-free survival was not statistically significant. Given the poor prognosis of non-transplant recipients and the lack of non-transplant curative approaches, our results support the consideration of allogeneic hematopoietic stem cell transplantation for eligible patients with primary myelofibrosis.