MRD-negative Remission Research Articles

Blinatumomab for MRD-Negative Acute Lymphoblastic Leukemia in Adults

BackgroundMany older adults with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) have a relapse despite having a measurable residual disease (MRD)–negative complete remission with combination chemotherapy. The addition of blinatumomab, a bispecific T-cell engager molecule that is approved for the treatment of relapsed, refractory, and MRD-positive BCP-ALL, may have efficacy in patients with MRD-negative remission.MethodsIn a phase 3 trial, we randomly assigned patients 30 to 70 years of age with BCR::ABL1-negative BCP-ALL (with :: indicating fusion) who had MRD-negative remission (defined as <0.01% leukemic cells in bone marrow as assessed on flow cytometry) after induction and intensification chemotherapy to receive four cycles of blinatumomab in addition to four cycles of consolidation chemotherapy or to receive four cycles of consolidation chemotherapy alone. The primary end point was overall survival, and relapse-free survival was a secondary end point.ResultsThe data and safety monitoring committee reviewed the results from the third efficacy interim analysis and recommended that they be reported. Complete remission with or without full count recovery was observed in 395 of 488 enrolled patients (81%). Of the 224 patients with MRD-negative status, 112 were assigned to each group. The characteristics of the patients were balanced between the groups. At a median follow-up of 43 months, an advantage was observed in the blinatumomab group as compared with the chemotherapy-only group with regard to overall survival (at 3 years: 85% vs. 68%; hazard ratio for death, 0.41; 95% confidence interval [CI], 0.23 to 0.73; P=0.002), and the 3-year relapse-free survival was 80% with blinatumomab and 64% with chemotherapy alone (hazard ratio for relapse or death, 0.53; 95% CI, 0.32 to 0.87). A higher incidence of neuropsychiatric events was reported in the blinatumomab group than in the chemotherapy-only group.ConclusionsThe addition of blinatumomab to consolidation chemotherapy in adult patients in MRD-negative remission from BCP-ALL significantly improved overall survival. (Funded by the National Institutes of Health and others; E1910 ClinicalTrials.gov number, NCT02003222.)

Blinatumomab in pediatric acute lymphoblastic leukemia: one center experience

Background. Despite the successes achieved in the treatment of B-cell acute lymphoblastic leukemia (B-ALL), overcoming the toxicity of standard chemotherapy regimens and the treatment of relapsed/refractory (r/r) forms of the disease remains relevant. The most promising option is to use immunotherapy (IT), including a monoclonal antibody blinatumomab (BM). The purpose of the study. To analyze indications of using, as well as efficacy and tolerability of BM in children with V-ALL. Materials and methods. From April 2016 to January 2024 a retrospective assessment of using of BM in children with B-ALL in the chemotherapy department of oncohematological diseases and TCM for children in Almazov National Medical Research Centre was performed. Results. The study included 53 patients, including 28 (53 %) girls and 25 (47 %) boys with median age of 7,7 (2,08–19,8) years. Indications for using of BM were as follows: (1) consolidation of remission (CR) with primary ALL (n = 17, 32 %); (2) persistence of minimal residual disease (MRD) (n = 23, 43 %) after completion of chemotherapy (CT) induction or before the stage of allogeneic haematopoietic stem cell transplantation (alloHSCT); (3) replacement of the standard CR due to the previous toxicity of СT or other contraindications to its implementation (n = 12, 23 %); (4) salvage therapy for r/r ALL (n = 1, 1,9 %). The status of MRD-negative remission after the 1st course of IT was achieved in 89 % of cases. Therapy using BM in a patient with the r/r ALL and total blast infiltration of the bone marrow was effective and facilitated reducing the tumor population to 7,2% by day 15 of therapy, however, there was a fatal outcome due to development and progression of preexisted severe infection. The most common variants of grade III–IV toxicity were leuko-/neutropenia (28 %) and neurotoxicity (3,7 %). BM dose reduction for the purpose of relieving toxicity was required in 19 % of patients, while the median days of therapy with dose reduction was 4. Corticosteroids were used for this purpose in 11 % of cases, antibacterial therapy — in 13 %. At the time of results evalution, there were no relapses of the disease in the study group. The article analyzes the international experience of using BM in patients with B-ALL.Conclusion. Our experience and the presented literature data demonstrate a reasonable expansion of indications for using of BM in children with B-ALL with high efficacy and satisfactory toxicity profile.

Obecabtagene autoleucel (obe-cel, AUTO1) in adults with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL): Overall survival (OS), event-free survival (EFS) and the potential impact of chimeric antigen receptor (CAR)-T cell persistency and consolidative stem cell transplantation (SCT) in the open-label, single-arm FELIX phase Ib/II study.

6504 Background: Obe-cel is an autologous CAR-T cell product with a fast off-rate CD19 binder designed to mitigate immunotoxicity and improve expansion/persistence. Pooled results from the pivotal FELIX phase Ib/II study (NCT04404660) of obe-cel in adults with R/R B-ALL were recently presented (Roddie C et al. Blood 2023;142[Suppl 1]:222). Here, OS and EFS in all patients (pts) treated with obe-cel are reported, alongside the impact of CAR-T cell persistency and consolidative SCT for pts in remission. Methods: Pts aged ≥18 yrs with R/R B-ALL were enrolled. CAR-T products were generated via an automated process (Roddie C et al. Blood 2023;142[Suppl 1]:222). Pts received bridging therapy as appropriate and underwent lymphodepletion (fludarabine, 4×30mg/m2; cyclophosphamide, 2×500mg/m2), followed by obe-cel split dose infusions on Days 1 and 10 based on pre-lymphodepletion leukemic burden at a target dose of 410×106 CAR-T cells. Results: A total of 127/153 (83%) enrolled pts were infused. At screening, pts’ median age was 47 yrs; 42%/31%/44% had received prior blinatumomab/inotuzumab ozogamicin/allogeneic SCT; median bone marrow blast burden was 36% (range: 0−100). At data cut-off (13 September 2023), median follow-up was 16.6 mos (range 3.7−36.6 mos). The overall complete remission or complete remission with incomplete count recovery rate among infused pts was 78%. Among responding pts, 17/99 (17%) proceeded to consolidative SCT while in remission; all 17 (100%) were in measurable residual disease (MRD)-negative remission (≤10–4 leukemic blasts) and 10/17 (59%) showed CAR-T cell persistency prior to SCT. Loss of CAR-T cell persistency was associated with a hazard risk of relapse or death 2.9 times compared with pts who had ongoing CAR-T cell persistency. Pts who experienced B-cell recovery had a hazard risk of relapse or death 1.7 times compared with pts without B-cell recovery. At 12 mos, the EFS rate was 50% and 43% with or without censoring for consolidative SCT or new therapies, respectively; the OS rate was 61% and 59% with or without censoring for SCT, respectively. Conclusions: Ongoing CAR-T cell persistency and B-cell aplasia were associated with improved EFS without further consolidation post-obe-cel. At the current follow-up, consolidative SCT for pts in MRD-negative remission post-obe-cel did not improve EFS or OS. Clinical trial information: NCT04404660 .

Blinatumomab-induced macrophage activating syndrome (MAS) in adult with B-cell acute lymphoblastic leukemia (B-ALL)

Blinatumomab as a single agent has demonstrated superiority over salvage chemotherapy in patients with relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL), with manageable safety and efficacy. Though known to have anticipated drug toxicities including cytokine release syndrome (CRS) and neurotoxicity, there is only one prior report of macrophage activating syndrome (MAS) due to blinatumomab. Case Presentation: We report the first case of blinatumomab-induced MAS in an adult. The patient presented with fever, cough, and weakness on the second cycle of blinatumomab. Complete blood count was notable for severe leukopenia, with comprehensive metabolic panel notable for elevated alkaline phosphatase, AST, ALT, LDH, and hyperferritinemia consistent with MAS. The patient was already in MRD-negative remission at presentation with MAS. She responded rapidly to withholding the drug and administration of both tocilizumab and dexamethasone. She was able to restart therapy with blinatumomab dosed at 9 mcg/day with no recurrence of symptoms. Though MAS is not an expected association with blinatumomab, the risk for CRS is. Secondary MAS in this case likely shares a mechanism with other hyperinflammatory conditions. Management includes holding the offending agent, like blinatumomab, and administering tocilizumab and dexamethasone. Future research will be needed to predict which patients are at highest risk to develop MAS after similar T-cell therapies.

Flow cytometry-based measurable residual disease (MRD) analysis identifies AML patients who may benefit from allogeneic hematopoietic stem cell transplantation.

Measurable residual disease (MRD) monitoring independently predicts long-term outcomes in patients with acute myeloid leukemia (AML). Of the various modalities available, multiparameter flow cytometry-based MRD analysis is widely used and relevant for patients without molecular targets. In the transplant (HCT) setting, the presence of MRD pre-HCT is associated with adverse outcomes. MRD-negative remission status pre-HCT was also associated with longer overall (OS) and progression-free survival and a lower risk of relapse. We hypothesize that the combination of disease risk and MRD at the time of first complete remission (CR1) could identify patients according to the benefit gained from HCT, especially for intermediate-risk patients. We performed a retrospective analysis comparing the outcomes of HCT versus non-HCT therapies based on MRD status in AML patients who achieved CR1. Time-dependent analysis was applied considering time-to-HCT as a time-dependent covariate and compared HCT versus non-HCT outcomes according to MRD status at CR1. Among 336 patients assessed at CR1, 35.1% were MRD positive (MRDpos) post-induction. MRDpos patients benefitted from HCT with improved OS and relapse-free survival (RFS), while no benefit was observed in MRDneg patients. In adverse-risk patients, HCT improved OS (HR for OS 0.55; p = 0.05). In intermediate-risk patients, HCT benefit was not significant for OS and RFS. Intermediate-risk MRDpos patients were found to have benefit from HCT with improved OS (HR 0.45, p = 0.04), RFS (HR 0.46, p = 0.02), and CIR (HR 0.41, p = 0.02). Our data underscore the benefit of HCT in adverse risk and MRDpos intermediate-risk AML patients.

Efficacy and safety of chimeric antigen receptor T-cell therapy followed by allogeneic hematopoietic stem cell transplantation in 21 patients with Ph-like acute lymphoblastic leukemia

Objective: To evaluate the efficacy and safety of chimeric antigen receptor T-cell (CAR-T) therapy followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with Ph-like acute lymphoblastic leukemia (Ph-ALL) . Methods: Patients with Ph-ALL who underwent CAR-T therapy followed by allo-HSCT from March 2018 to August 2023 at the First Affiliated Hospital of Soochow University were included, and their clinical data were retrospectively analyzed. Results: Of the 21 patients, 14 were male and 7 were female. The median age at the time of CAR-T therapy was 22 (6-50) years. Seven patients had ABL1-like rearrangements, and 14 had JAK-STAT rearrangements. Prior to CAR-T therapy, 12 patients experienced hematologic relapse; 7 were multiparameter flow cytometry minimal residual disease (MFC-MRD) -positive and 2 were MFC-MRD-negative. CAR-T cells were derived from patients' autologous lymphocytes. Nine patients were treated with CD19 CAR-T cells, and 12 were treated with CD19/CD22 CAR-T cells. After assessment on day 28 after CAR-T therapy, 95.2% of the patients achieved complete remission, with an MRD-negative remission rate of 75%. Nineteen patients developed grade 0-2 cytokine release syndrome (CRS) and 2 patients suffered grade 3 CRS, all cases of which resolved after treatment. All patients underwent allo-HSCT after CAR-T therapy. The median time from CAR-T therapy to allo-HSCT was 63 (38-114) days. Five patients experienced relapse after CAR-T therapy, including four with hematologic relapse and one with molecular relapse. The 3-year overall survival (OS) rates in the ABL1 and JAK-STAT groups were (83.3±15.2) % and (66.6±17.2) %, respectively (P=0.68) . The 3-year relapse-free survival (RFS) rates were (50.0±20.4) % and (55.6±15.4) % in the ABL1 and JAK-STAT groups, respectively. There was no significant difference in 3-year OS or RFS between the two groups. Conclusions: CAR-T therapy followed by allo-HSCT leads to rapid remission in most patients with Ph-ALL and prolongs leukemia-free survival.

Venetoclax: A Game Changer in the Treatment of Younger AML Patients?

The combination approach based on venetoclax (VEN) with azacytidine (AZA) has significantly improved outcomes for elderly patients with acute myeloid leukemia (AML). This innovative approach has led to higher rates of overall response, measurable residual disease (MRD)-negative remissions, and overall survival compared with AZA monotherapy. As a result, this combination has emerged as the gold-standard treatment for elderly or unfit patients with AML who are not eligible for intensive therapy. In younger, fit patients with AML, intensive induction and consolidation chemotherapy is commonly used as a first-line approach; however, relapse continues to be the main reason for treatment failure in approximately 30-40% of patients. Efforts to improve MRD-negative response rates and to facilitate the transition to allogeneic hematopoietic stem cell transplantation, particularly in high-risk AML, have inspired trials exploring the combination of intensive chemotherapy with targeted agents. VEN, a first-in-class anti-BCL2 agent, combined with intensive chemotherapy regimens has shown deep MRD-negative remissions, producing prolonged event-free survival and enhancing the transition to allogeneic transplant in first-complete-remission patients. These benefits support the incremental advantages of adding VEN to intensive chemotherapy approaches across ELN risk subcategories, and provides a robust benchmark to design future trials. In this review, we will discuss current studies assessing the efficacy of frontline regimens integrating VEN into intensive chemotherapy in younger patients with AML and specific molecularly defined subgroups.

Venetoclax Combined with HMA Versus CAG Based Chemotherapy in Acute Myeloid Leukemia: A Propensity Score Matched Analysis

Abstract Background: Venetoclax(VEN) combination with hypomethylating agent(HMA) are lower-intensity regimens with safety which are widely used for older patients with newly diagnosed acute myeloid leukemia (AML). On the other hand, regimen of cytarabine, aclarubicin and G-CSF (CAG) with or without HMA is also of low-intensity usually applied to older AML patients. The comparison of outcomes of these two regimens has not been reported. In this study, we performed a multicenter, retrospective propensity score-matched study to compare the therapeutic responses and survival outcomes of newly diagnosed AML patients with induction of HMA-VEN to those with CAG based treatment. Methods: Newly diagnosed AML patients treated either VEN/HMA or CAG with or without HMA between January 2013 and April 2023 were compared. Age at diagnosis, sex, ECOG performance status, state of fitness for intensive chemotherapy according to Ferrara criteria and ELN2017 risk group were used to construct the propensity score using logistic regression. Propensity score matching was performed in a 1:1 ratio with a calliper value of 0.02. The treatment response, relapse rate, duration of remission, overall survival (OS) were compared between the two groups. Results: A total of 98 out of 109 newly diagnosed patients treated with VEN/HMA were matched to 98 out of 159 newly diagnosed patients treated with CAG based therapy. The patients in VEN/HMA cohort were treated between February 25, 2021 and April 30, 2023. The CAG based treatment recipients were treated from January 25, 2013 to November 12, 2021. The CAG based treatment cohort which was termed as “CAG cohort” below matched closely with the VEN/HMA cohort in terms of baseline characteristics and propensity scores (Table1). The median age was 62 years (range, 52-67) in VEN/HMA cohort and 63 years (range,52-68) in CAG cohort, and the median follow-up period was 6.3 months (range,3.2-14.0) in VEN/HMA cohort and 12 months (range,3.8-28.3) in CAG cohort. Patients treated with VEN/HMA achieved a significantly higher rate of CRc (82.4% vs 60.6%, P=0.002) compared to CAG cohort, with 36.5% in CR, 45.9% in CRi in VEN/HMA cohort and 30.3% in CR, 30.3% in CRi in CAG cohort. There was no statistic difference of the CRc rate between CAG versus CAG plus HMA(35.7%，n=14 vs 60.5%,n=76, p=0.085). CRc in the VEN/HMA and CAG cohort were 100% vs 85.7(p=0.483), 75.9% vs 46.9%(p=0.021), 64.3% vs 45.2%(p=0.079) in the ELN2017 favorable, intermediate and adverse risk group, respectively. The MRD-negative remission rate was higher in VEN/HMA cohort compared to CAG cohort (85.5% vs 61.2%, p= 0.003). The MRD-negative remission rate in the VEN/HMA and CAG cohort were 91.6% vs 80.0%(p=0.571), 88.0% vs 66.6%(p=0.188), 83.9% vs 45%(p=0.003) in the ELN2017 favorable, intermediate and adverse risk group, respectively(Table2). Responses of patients with different mutations were analyzed and ASXL1 predicted higher CRc rate with VEN/HMA treatment compared to CAG based treatment (92.3% vs. 40%, p= 0.019). The median OS was not reached in VEN/HMA cohort and 18 months in CAG cohort(p=0.16). Patients who achieved CRc had longer survival than those without CRc (not reached vs 6.4m, p&amp;lt;0.001). Patients who got MRD negative remission had better survival than those only with MRD positive remission (not reached vs 11.8m, p=0.0002). Patients who underwent allogeneic HSCT had longer survival than those didn't receive transplantation (not reached vs 12.3m, p&amp;lt;0.001). Conclusions: With propensity score-matched analysis, our data show that VEN/HMA demonstrates better treatment response than CAG regimen in patients with newly diagnosed AML. The survival outcome benefits from MRD negative response and allogeneic HSCT. Disclosures No relevant conflicts of interest to declare.

Safety and Efficacy of Azacitidine and Chidamide Maintenance after Allogeneic Hematopoietic Stem Cell Transplantation for Patients with High-Risk Acute Myeloid Leukemia: Interim Analysis of a Prospective, Multicenter, Single-Arm, Phase Ⅱ Clinical Trial

Background Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the potentially curative therapy for AML, the relapse rate after HSCT is high with 30-60% for patients with high-risk AML. Maintenance therapy with efficacy and low toxicity is needed to mitigate relapse. It has been reported that histone deacetylases inhibitor chidamide exhibits anti-tumor activity against AML cells, and is able to elicit anti-tumor immune response in mouse models. However, efficacy and safety of chidamide as maintenance therapy following allo-HSCT for patients with AML have not been reported. Therefore, we designed a multicenter, single arm, phase II clinical trial for high-risk AML patients to use azacitidine combined with chidamide as maintenance therapy post allo-HSCT to prevent relapse. Methods In this multicenter, single arm, phase II clinical trial, patients aged 18-60 years with high-risk AML, defined as the European LeukemiaNet (ELN) 2017 adverse risk group, refractory, relapsed or secondary AML were given AZA and chidamide as maintenance therapy after 60 days post transplantation (NCT05270200). AZA was given at 100mg/day (days 1-5) for 6 cycles and chidamide 5mg daily (days 1-28) with a cycle of 28 days for up to 2 years. The dose of AZA was amended at 50mg/m 2/day (days 1-3) from Dec 23,2022 due to occurrence of thrombocytopenia. If PLT was below 50×10 9/L or grade 3/4 non-hematological toxicity occurs, maintenance should be interrupted or delayed until PLT count was greater than 75×10 9/L or the non-hematological toxicity resolved to ≦ grade 1. Primary objectives were safety and one year cumulative incidence of relapse. Secondary objections were relapse-free survival (RFS), overall survival (OS) and incidence of severity of acute and chronic graft-versus-host disease (GVHD). Results From February 12,2022 to June 30,2023, seven patients were enrolled, with a median age of 46 years（28-60), four patients (57%) were female. One patient (14%) received matched sibling donor transplantation, six patients (86%) received haploidentical donor transplantation. Five patients (71%) received myeloablative and 2/7 (29%) reduced intensity conditioning regimen. Six (86%) were in ELN 2017 adverse risk with three patients harboring KMT2A rearrangement, one patient with TP53 mutation, one patient with -7, one patient with RUNX1 mutation, while one patient (14%) was diagnosed as secondary AML with broad extramedullary infiltration. All but one patients entered transplant in CR, while five patients (83%) were MRD negative and one patient (17%) were positive. The baseline patient characteristics are summarized in Table1. Outcome data were updated as of June 30,2023 (Figure1). The median time to start maintenance therapy after transplantation was 77 days (range 64-80). The median follow-up time was 9.9 months, only one patient relapsed and the accumulative incidence of relapse of one year was 16.7%（95%CI,0.4%-64.1%). The relapsed patient diagnosed with MLL-AF10 rearrangement had extramedullary infiltration of left tonsil, gum and neck lymph nodes at 197 days post transplantation while bone marrow remained in MRD negative remission. AZA/chidamide were well tolerated, with no severe adverse event was recorded. Two grade 3/4 non-hematologic adverse events were observed, with one increased bilirubin due to cGVHD and one pneumonia. Two patients (29%) experienced grade4 thrombocytopenia requiring platelet transfusion. After amendment of AZA dose, no grade4 thrombocytopenia was recorded. No one discontinued treatment due to toxicity. During follow-up, none of patients had aGVHD. Three patients (43%) experienced mild or moderate cGVHD, no severe cGVHD was observed. The median OS was not reached, with six months and one year OS both of 100%. The median RFS is not reached, with six months and one year RFS of 100% and 83.3%(95%CI,35.9%-99.6%). Conclusions Preliminary results suggest that maintenance of AZA combined with chidamide post allo-HSCT in patients with high-risk AML exhibits promising efficacy and well-tolerated. Recruitment of patients with high-risk AML post allo-HSCT for this trial is ongoing. Disclosures No relevant conflicts of interest to declare.

A Phase I/II Study of Combination of ASTX727, Gilteritinib and Venetoclax in Patients with Relapsed/Refractory FLT3 Mutated Acute Myeloid Leukemia (AML)

Background Activating mutations in FLT3 occur in approximately 30% of patients (pts) with AML. Gilteritinib (GILT), a second-generation type I oral FLT3 inhibitor, has been approved in pts with relapsed/refractory (R/R) FLT3-mutated AML. We conducted a phase I/II study to evaluate the combination of decitabine/cedazuridine (ASTX727), venetoclax (VEN), and GILT in pts with FLT3-mutated R/R AML or intermediate-2/high risk MDS/CMML. Methods This phase I/II study included pts with 1) R/R FLT3-mutated AML or R/R intermediate-2/high risk MDS/CMML or 2) newly diagnosed FLT3-mutated AML unfit for intensive chemotherapy (eligible for phase II only). Here we report the initial data from the R/R cohort. In the phase I portion there was no restriction to the number of prior therapies received; however, in the phase II portion pts who had received ≥3 prior therapies were excluded. Pts with FLT3-ITD and/or TKD mutations were eligible. Pts were required to have a performance status ≤3, total bilirubin ≤2.5 x ULN, ALT/AST ≤3 x ULN, and creatinine clearance ≥30 mL/min. In cycle 1 (C1), pts received decitabine/cedazuridine (35mg/100mg) orally on days 1-5, VEN (ramp-up to 400mg with adjustment for concomitant azole) orally on days 1-28, and GILT orally continuously. The GILT dose ranged from 80mg to 120mg daily during the phase I dose escalation (3+3 design). A bone marrow biopsy was performed on day 14, and if blasts were &amp;lt;5% or the marrow was insufficient/aplastic, the VEN was held. For C2 and beyond, ASTX727 was given for 5 days, VEN was given for 14-21 days and GILT was given continuously. The primary endpoint for the phase I was the MTD; and for the phase II, the overall response (defined as CR, CRh, CRi, or MLFS within 2 cycles of therapy). Results The phase I portion is complete with 12 pts enrolled (11 AML, and 1 high-risk CMML). Nine pts received GILT 80mg and 3 received 120mg. No DLTs at either dose level were observed. However, 80mg of GILT was selected for the phase II portion of this study based on the more favorable safety/efficacy profile and better count recovery observed in a parallel study of azacitidine combined with VEN and GILT in AML. In the combined phase I/II cohort of pts with R/R AML or MDS/CMML, 15 pts have been treated. The median age was 65 years (range 38-83 years). Thirteen pts had a FLT3-ITD mutation (including 2 with a concomitant TKD mutation), and 1 pt had a FLT3-TKDmutation alone. Among pts with a FLT3-ITD, the median allelic ratio was 0.21 (range, 0.09 - 10.6). Among pts with a FLT3-TKD, the median allelic ratio was 0.05 (range, 0.02-0.09). Nine pts had diploid karyotype, 2 had adverse risk karyotype, and 4 had miscellaneous, intermediate-risk cytogenetic findings. The median number of prior therapies was 1 (range 1-9). Among the 15 pts treated, 8 (53%) responded: 1 (6%) with CRh, 3 (20%) with CRi, and 4 (27%) with MLFS. The pt with an isolated FLT3-TKD mutation (along with del7q) did not respond. The pt with high-risk CMML achieved a CRi. Six of 12 pts who received prior HMA + VEN responded (2 CRi and 4 MLFS), and 2 of 3 pts without prior HMA + VEN responded (1 CRh and 1 CRi). The median number of cycles received by pts was 2 (range 1-8). Best response was achieved by the end of C1 in 50% of responders, and by the end of C2 in the other 50% of responders. Of the 8 responders, 1 proceeded to alloSCT (with flow positive MRD at 0.3% but FLT3 negative by PCR), 1 is still receiving treatment on protocol with continued response, 5 relapsed without HSCT (median time to relapse 2 months [range, 0.5-7 months]), and 1 died in MLFS. The transplanted pt remains in MRD-negative remission 5 months after alloSCT and is receiving maintenance GILT off protocol. With a median follow-up of 3.8 months (range, 1-18 months), the median overall survival for the cohort was 6.1 months. There were 3 pts with grade 1-2 toxicities (1 with elevated liver enzymes, 2 with skin rash), 9 pts with grade 3 toxicities (9 with neutropenic fever, 4 of which became septic), no pts with grade 4 toxicities, and 2 patients with grade 5 toxicities (both had neutropenia and died from sepsis while on trial). Conclusion In this poor-risk population of pts with R/R FLT3-mutated AML or MDS/CMML, many of whom received prior HMA + VEN, the combination of ASTX727, VEN, and GILT was active, with an ORR of 53%. The trial continues to enroll to the R/R cohort, and is now open for patients with newly diagnosed FLT3-mutated AML who are unsuitable for intensive chemotherapy.

Comparison of Safety and Efficacy between Venetoclax Combined with CAG (cytarabine, aclarubicin, G-CSF) Regimen and CAG Regimen Alone in Patients with Relapsed or Refractory Acute Myeloid Leukemia

Background: Patients with relapsed or refractory (R/R) acute myeloid leukemia (AML) have dismal outcomes, representing an urgent unmet need. The BCL2 inhibitor venetoclax has exhibit encouraging anti-tumor activity in AML. The clinical efficacy of the CAG regimen in patients with R/R AML has been confirmed in previous studies. The aim of this study was to retrospectively compare the safety and efficacy of the combination of venetoclax with CAG regimen and CAG alone in patients with R/R AML. Patients and methods: We retrospectively reviewed and compared the efficacy and safety of venetoclax combined with the CAG regimen (Ven-CAG group, n=37) and CAG regimen alone (CAG group, n=37) for 74 patients with R/R AML treated at our institution between August, 2016 and March 2023. The patients included those who were refractory to at least one cycle of induction chemotherapy, and patients with relapsed leukemia. According to the duration from complete remission (CR) to relapse, the relapsed patients were further divided into two subgroups, the favorable-risk relapsed group (the duration≥12 months) and the poor-risk relapsed group (the duration&amp;lt;12 months). The incidence of composite complete remission (CCR), minimal residual disease (MRD) status, one-year overall survival (OS), and adverse events (AEs) were analyzed and compared in two groups. Results: Patient age, sex, ELN risk stratification, disease status, risk stratification according to the duration from CR to relapse were comparable between two groups (Table 1). The CCR of Ven-CAG group was 78.4% (29/37)，which was superior to 56.8% (21/37) of CAG group (P=0.047) . Furthermore, the rate of MRD elimination in patients who achieved CCR in Ven-CAG group was significantly higher than that in CAG group [44.8% (13/29) vs. 9.5% (2/21), P= 0.007] (Table 2). The rate of MRD elimination in favorable-risk relapsed group (CR to hematological relapse ≥12 months) was higher in Ven-CAG group [100% (5/5) vs. 25% (1/4), P= 0.048]. The one-year OS were 78.4% (95% CI, 62.3%-94.5%) and 66.7% (95% CI, 51.2%-82.2%) in Ven-CAG and CAG group (P=0.225), respectively. The incidences of grade 3-4 hematologic AEs in Ven-CAG group and CAG group were 100% (37/37) and 97.3% (36/37), respectively (P=1.000). The incidences of febrile neutropenia were 67.6% (25/37) and 62.2% (23/37), respectively (P=0.626). Among patients who achieved CCR, the median time for neutrophil recovery in the Ven-CAG group and CAG group were 8 (3-30) days and 9.5 (3-31) days (P=0.781), while the median time for platelet recovery was 9 (3-28) days and 8 (3-19) days (P=0.708). The incidences of grade 3-4 non-hematologic AEs were comparable in Ven-CAG and CAG group (32.4% vs. 35.1%, P=0.806). The most common nonhematologic AEs were infections, with the incidences of 18.9% and 27%, respectively (P=0.407). No patients died within 4 weeks after initiating the induction course in Ven-CAG group. There was one case of early death during induction in CAG group due to cerebral hemorrhage. Conclusions: Venetoclax added to CAG regimen was safe and active in patients with R/R AML, producing higher CCR and MRD-negative remissions than CAG regimen alone. These results highlight the incremental benefit of venetoclax added to CAG regimen. This requires further verification through prospective, larger size clinical trials.

A Rare Cell State Underpins Diverse Mechanisms of Adaptive Resistance to CAR T-Cell Therapy in B-Cell Acute Lymphoblastic Leukemia

The most common pattern of treatment failure of B-cell acute lymphoblastic leukemia (B-ALL) following CD19-targeting chimeric antigen receptor T cell therapy (CAR T), is a measurable residual disease (MRD) negative response followed by relapse. Whilst in a fraction of patients relapse is associated with loss of function mutations &amp;/or deletions of the CD19 locus, a significant proportion of patients relapse with CD19+ disease. We hypothesised that this arises from a rare CAR T tolerant persister population that is able to survive the strong therapeutic pressure and seed relapse. To address this, we investigated the clonal origin and transcriptional dynamics of “CAR T tolerant persister cells” via time resolved clonal tracing of the progeny of individual B-ALL clones, using expressed molecular barcodes in an immunocompetent mouse model of CD19 targeting CAR T. We demonstrate that relapse is a pre-determined fate of rare B-ALL clones, which each adopt diverse, yet clone-specific, transcriptional phenotypes at relapse. Moreover, each diverse relapse phenotype appears to be underpinned by a shared, rare “origin of relapse” cell state that is common to all relapse-fated clones. Our immunocompetent mouse model of murine CAR T cells targeting CD19 (ID3-h41bb-3z) on a syngeneic, BCR::ABL1(p190) driven B-ALL recapitulates the clinical scenario of MRD-negative remission followed by CD19+ relapse. We labelled B-ALL cells with SPLINTR (Fennell &amp; Vassiliadis et al. Nature 2022), a lentiviral lineage tracing reagent comprising expressed molecular barcodes that are read out by single cell RNA sequencing (scRNAseq), to allow dynamic profiling of the clonal origin and transcriptome of individual B-ALL clones over time, across multiple therapeutic timepoints including pre-treatment, remission and relapse. Tumour initiating frequency in this model of B-ALL is high with 23% of transplanted clones able to establish fulminant B-ALL. Only 0.7% of clones, however, were able to persist following CAR-T pressure and seed relapse. In fact, &amp;gt;99% of post-CAR T relapsed disease was comprised by just 3 (0.3%) individual clones and in one mouse disease relapse was driven entirely a single clone. Remarkably, we found that the same clones were able to drive relapse in multiple mice, consistent with a the presence of pre-determined, heritable cell-intrinsic properties capable of causing relapse following CAR T. To further study this phenomenon, we performed scRNAseq on these murine B-ALL samples to examine the transcriptional profiles of these rare, relapse fated clones prior to and following CAR T. Whilst prior to therapy, relapse fated clones were transcriptionally identical to the CAR T sensitive clones, following CAR T we observed that relapse fated clones adopted distinct transcriptional profiles compared to their transcriptome in the absence of therapeutic pressure, suggesting transcriptional adaptation underpins their ability to survive therapy. We noted that each resistant clone had a unique adaptive response and consequent transcriptional signature. Remarkably however, the adaptive response of each clone in different mice was essentially identical, indicative of strong, conserved clone-intrinsic mechanisms of adaptation. Although each CAR T resistant clone adopted disparate transcriptional states in the bulk ALL, we identified a single rare cell state (~1% of the bulk B-ALL) that was shared between all clones, highly suggestive of a common point of origin from which transcriptional adaptation arises. This rare cell state demonstrates metabolic hallmarks of therapy resistance and a distinct developmental transcriptional profile most analogous to the recently characterised preBCR-dependant stage of normal B cell development, raising the prospect that these cells represent an “origin of relapse” cell state. Preliminary data suggests that this rare cell state may also be conserved in human Ph+ B-ALL. In summary, by modelling CD19+ B-ALL relapse following MRD negative remission after CAR T, we have identified a rare cell state that our analysis suggests serves as a common and necessary point from which a transcriptionally diverse range of B-ALL phenotypes can arise and be maintained. We have demonstrated that relapse following CAR T emerges due to clone-specific transcriptional differences from this rare cell state, a phenomenon which may extend to a diverse range of therapies in B-ALL.

Revumenib Maintenance Therapy Following Revumenib-Induced Remission and Transplant

Background: The potent and selective oral menin-histone-lysine N-methyltransferase 2A (KMT2A) inhibitor revumenib (SNDX-5613) induced complete remissions with clearance of residual disease in acute leukemias refractory to multiple previous lines of therapy ( Nature. 2023;615:920-924). Here we report outcomes following the resumption of revumenib after hematopoietic stem cell transplant (HSCT). Methods: Patients aged ≥30 days with relapsed or refractory (R/R) acute leukemias with genetic alterations associated with HOXA overexpression, including KMT2A-rearranged ( KMT2Ar) or nucleophosmin 1 ( NPM1)-mutated leukemias, were enrolled in the AUGMENT-101 phase 1/2, multicenter, open-label, dose-escalation study (NCT04065399). Patients received revumenib every 12 hours (q12h) in 28-day continuous cycles. Patients who achieved a complete response (composite definition [CRc]), morphological leukemia-free state, or partial response could undergo HSCT without leaving the study. Revumenib was stopped before the HSCT conditioning regimen but, per a protocol amendment, could be resumed after HSCT if the patient was in CRc. Measurable residual disease (MRD) was assessed using multiparameter flow cytometry and/or polymerase chain reaction. Results: Between November 5, 2019, and June 28, 2023, a total of 131 phase 1 patients were enrolled and treated in the AUGMENT-101 study. Nine patients with acute myeloid leukemia (AML) from the AUGMENT-101 study resumed revumenib (8 after transplant and 1 after a stem cell boost [Table 1]). Seven patients had KMT2Ar and 1 patient each had nucleoporin 98 rearranged (NUP98r) and mutated NPM1. Revumenib was resumed 59 to 180 days after HSCT (Table 2). Dose was reduced for 4 of 9 patients to mitigate adverse events of thrombocytopenia (n=3) and leg pain (n=1), and revumenib was discontinued in 4 of 9 patients because of progressive disease (n=2), cytopenias (n=1), and not reported (n=1). Revumenib duration of treatment (DOT) in the maintenance setting at the time of this analysis ranged from 23 to 588 days, with treatment ongoing for 5 of the 9 patients. CRc was maintained in 6 of 9 patients after HSCT and maintenance revumenib. One patient with reported MRD after HSCT converted to MRD-negative status following initiation of revumenib maintenance therapy. Overall, MRD-negative remissions were maintained in 5 patients as of the data cut off. Conclusions: With 3 patients on revumenib maintenance therapy for more than a year, long-term responses, including conversion to MRD-negative status, were seen in these heavily pretreated patients with AML. Resuming revumenib post HSCT had a tolerable safety profile consistent with that previously reported for the AUGMENT-101 study.

Venetoclax+Azacytidine Followed By Modified BuCy Conditioning Regimen for High Risk or Refractory/Relapsed Acute Lymphoblastic Leukemia and High Risk Myelodysplastic Syndromes

Background:Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only potential curable treatment for myelodysplastic syndromes (MDS) and acute lymphoblastic leukemia (ALL). However, for patients with high-risk or refractory relapsed (R/R) B-ALL with allo-HSCT, the three-year overall survival (OS) rate is only 5-10%, more worse in T-ALL. It is widely known that MDS patients in the high-risk group do not benefit from induction chemotherapy, the five-year OS rate is 23-39% when they received allo-HSCT. Nevertheless, relapse remains a significant cause of treatment failure after allo-HSCT, highlighting the urgent need for improved conditioning regimens that can improve prognosis and reduce relapse rates. Azacytidine (AZA) combined with Venetoclax (VEN), showed a synergistic anti-tumor activity against several hematological malignancies, Therefore, we explored AZA+VEN (VA) combined with modified BuCy(mBuCy) (semustine, cytarabine, busulfan, and cyclophosphamide) conditioning regimen and assessed the safety and effectiveness. Aims ：The aim of this study is to assess the safety, and effectiveness of the VA treatment regimen followed by mBuCy as conditioning regimen for high-risk or R/R ALL(NCT05809167) and high-risk MDS(NCT03256071) . Methods:Patients diagnosed with high-risk or R/R ALL or high-risk MDS (IPSS-R score), undergoing VA+mBuCy as conditioning regimen, and consolidation treatment with demethylating drugs every three months after transplantation, for a total of 8-12 cycles. Results:Patients diagnosed with high-risk or R/R ALL(n=11) or high-risk MDS (IPSS-R score)(n=8) were enrolled between January 13, 2022, and June 9, 2023. The ALL cohort comprised of 5 Ph-negative B-ALL, 2 Ph-positive B-ALL, 3 mixed phenotype leukemias (MPAL), and one T-lymphoblastic lymphoma/leukemia (T-ALL/LBL). There were 7 males and 4 females, with a median age of 33 years (17-54 years) (Table 1). Out of the eleven patients, four had previously undergone Chimeric Antigen Receptor T-Cell Immunotherapy (CAR-T) therapy, and one patient had received Blinatumomab. One patient experienced relapse, another patient was refractory, and 3 patients had extramedullary infiltration. All patients achieved morphological complete remission prior to transplantation, and 10 patients (90.9%) achieved a MRD negative remission. Additionally, all the transplantations successfully completed, with a median time to absolute neutrophil counts (ANC) recovery of 12 days (11-15 days) and platelet (PLT) recovery of 16 days (15-21 days). The median follow-up time was 6.4 months (2.4 -13.6 months), no patient experienced relapse or death, the OS and DFS are both 100%. There were no grade 3 or higher adverse events (AEs), hepatic veno-occlusive disease (VOD),and the transplant-related mortality (TRM). Four patients who developed acute graft-versus-host disease (aGVHD) post-transplantation, all cases involved grade I/II skin aGVHD, and one of them involved grade III GI aGVHD, and no chronic graft-versus-host disease (cGVHD) were observed during the follow-up period. By the endpoint of follow-up, Cytomegalovirus (CMV) activation was 45.4% (5/11) and Epstein-Barr virus (EBV) activation was 27.3% (3/11). The MDS cohort consisted of 7 cases of MDS-EB-I, 1 case of MDS-EB-II. There were 5 males and 3 females, with a median age of 42 years (23-57 years)(Table 2). Two patients received chemotherapy before transplantation, and the other six patients directly received allo-HSCT. In MDS cohort, the median recovery time for ANC was 12 days (11-13 days) and PLT was 17.5 days (16-20 days). The median follow-up was 14.3 months (1.2-18.3 months), no patient had relapsed or died, both OS and DFS are 100%. There were no grade 3 or higher AEs, and TRM. One patient developed VOD. Three patients developed aGVHD after transplantation, all involving degree I/II skin aGVHD, and there was one case of cGVHD during the follow-up period, where the patient developed a mild pulmonary cGVHD. By the endpoint of the follow-up, the rate of CMV activation was 37.5% (3/8) and EBV activation was 25% (2/8). Conclusion:The VA combined with the mBuCy proves to be a effective and safe conditioning regimen for high-risk ALL and MDS patients. However, more patients are needed for follow-up and validation.

Venetoclax after Progression on Ibrutinib: Results of a Russian Multicenter Study

Introduction Currently, venetoclax is the therapeutic choice for many patients with chronic lymphocytic leukemia progressed on ibrutinib. The optimal drug combinations with venetoclax, the goals and timing of therapy, as well as predictors of response are not yet clear. Only a few clinical trials have included patients with progression on ibrutinib (Kater AP, et.al., J Clin Oncol 2019). Approach to ibrutinib discontinuation and addition of antibodies to CD20 are still a matter of debates. Objectives The aim of this multicenter study was to retrospectively compare outcomes in patients who received venetoclax either alone or in combination with monoclonal antibodies to CD20, as well as outcome of patients who continued ibrutinib after switching to venetoclax. Methods The study included 122 patients with disease progression on ibrutinib according to iwCLL2018 criteria. The data were collected by 27 centers from 25 regions of Russia. Fifty four patients (44%) received venetoclax without monoclonal antibodies, 46 (38%) in combination with obinutuzumab, 22 (18%) with rituximab. Nineteen patients stopped ibrutinib before venetoclax with median interval between treatments of 10 days (range 0 - 91 days). All other patients received venetoclax concomitantly with ibrutinib for some time after progression. Patients who stopped ibrutinib less than 3 months from the date of onset of venetoclax were considered to have discontinued ibrutinib. Results The median age was 63 years (range 30-82), 76 patients were males (62%). Median progression free survival (PFS) for all patients was 26.5 months, overall survival (OS) was 35.2 months. Fifteen patients (12%) had Richter transformation before venetoclax. Overall survival of these patients was significantly worse when compared to other patients, with hazard ratio (HR) 3.46 95% CI 1,42 - 8,48 (p&amp;lt;0.0001). Twenty two patients stopped therapy before the event of death or progression. Reasons included toxicity (N=10), three consecutive confirmation of MRD-negative remission 3 months apart (N=11), and allogeneic stem cell transplantation (N=1). Patients who died or had progression within 3 months after the onset of venetoclax, as well as patients with Richter syndrome diagnosed before the onset of venetoclax were excluded from survival analysis. Table 1 presents patients' characteristics. On pre-treatment, poor outcome was significantly predicted by time to progression on ibrutinib &amp;lt;24 months (PFS: HR 0.53, 95% CI 0.27 - 1.06, p=0,04; OS: HR 0.45, 95% CI 0,22 - 0,93, p=0,01) and ECOG status &amp;gt; 2 (PFS: HR 0.37, 95% CI 0,1 - 1,35, p=0,007; OS: HR 0.32, 95% CI 0,08 - 1.27, p=0,002). There were no differences in baseline characteristics in patients who continued and discontinued ibrutinib, although in the former group more patients have developed Richter syndrome during treatment. Ibrutinib discontinuation was associated with better outcome (PFS: HR 3.72, 95% CI 1.95 - 7.09; OS: HR 3.93, 95% CI 1.96 - 7.88, Figure 1A, B). In total 15 deaths occurred before progression (COVID-19 - 11 patients, secondary cancers - 2, sudden death - 1, pneumonia - 1), and the majority (N = 13) in the group of patients who continued ibrutinib. The group of patients who received antibodies to CD20 was younger (63 versus 69 years, p=0.03), while other baseline parameters were similar. No significant differences were found in either PFS (HR 1.38, 95% CI 0.69 - 2.7) or OS (HR 1.36, 95% CI 0.67 - 2.8, Figure 1C, D). Subgroup analysis of patients who discontinued ibrutinib showed that patients who received venetoclax with monoclonal antibodies had better PFS compared to those on venetoclax alone (HR 6.32, 95% CI 1.43 - 27.8, p=0.045), while OS in the two subgroups did not differ. Conclusion Our data do not support the hypothesis that continuing ibrutinib therapy beyond 2 - 3 months in the context of progression on ibrutinib benefits patients. As evident from increase in PFS, it seems that patients who had discontinued ibrutinib may benefit from adding CD20 antibodies to venetoclax.

Durable MRD and Imaging-Negative Remission ≥ 5 Years Post-Therapy Predicts Long-Term Progression-Free Survival in Multiple Myeloma Patients - a Single-Center Observational Study

Introduction With the advent of modern multiple myeloma (MM) therapies, a significant proportion of patients can achieve durable clinical remission. Minimal residual disease (MRD) reflects depth of response and is a powerful predictor of progression-free survival (PFS) (Munshi et al, JAMA Oncology 2017). Although sustained MRD negativity (defined by IMWG as MRD-negative on two occasions, minimum one-year apart) is associated with improved PFS, there is continued long-term relapse in these patients. A recent study reported a 10-year PFS of 88% in MM patients who are MRD-negative &amp;gt; 3 years after total therapy (Mohan et al, Blood Advances 2022). In the current era of regular MRD testing in MM care, we aimed to estimate the 10-year PFS of unselected MM patients who are MRD and imaging-negative ≥ 5 years after latest therapy, using our single-center data. Methods MRD testing was introduced for MM patients in remission at the Icahn School of Medicine at Mount Sinai (ISMMS) in 2017. Therefore, we systematically reviewed all patients with MRD results in the ISSMS MM registry between July 2017 and December 2022. Next-generation multi-parametric flow cytometry (NGF) was used to detect MRD from 2017 to 2021, with the addition of next-generation sequencing (NGS) from 2021 onwards. MRD-negativity was defined as &amp;lt;1 in 10 5 by NGF or &amp;lt;1 in 10 6 by NGS, and one representative MRD result per year was taken for analysis. Whole-body positron emission tomography (PETCT) and MRI were used to evaluate bone or extra-medullary (EM) disease. Detailed retrospective chart review of patients with sequential MRD-negative results was conducted to identify those with durable clinical, MRD, and imaging negative remission. PFS was evaluated using Kaplan-Meier curves and survival estimates. Results Between 2017 and 2022, 1703 MM patients underwent MRD testing at our center. Of these patients, we have so far identified 92 patients who were in CR, MRD and imaging-negative ≥ 5 years after the start of latest therapy. The estimated 10-year PFS in our cohort was 91.4% (95% CI [0.833 ,1]; Figure 1). With a median follow-up time of 5.9 years (4.6 to 12.6 years), the majority of our cohort (75%) were off-therapy at last follow-up with a median time-off-therapy of 2.5 years. In terms of baseline patient and disease characteristics (Table 1), 57.6% patients were white and 60.9% were male. Most patients were ISS stage I (51.1%) with standard-risk cytogenetics (78.2%) at diagnosis. A much smaller proportion of our cohort had any adverse cytogenetics, including gain1q (13%) and del17p or TP53 mutation (7.6%). The majority of patients were in their first remission after frontline therapy (52.2%), with 33.7% having received autologous stem cell transplant (ASCT) first-line. A smaller proportion of the cohort had received salvage treatment; 31.5% had received two lines, 16.3% had received ≥ 3 lines. Four patients relapsed in this cohort (4.3%) and one patient died of a non-MM related cause. Of the patients who progressed, 2 relapsed with isolated biochemical disease and 2 with predominantly EM disease. Both biochemical relapses were preceded by conversion to MRD positivity by NGF 6 months to 1 year prior, whereas those relapsing with EM disease remained MRD negative. Three patients had been off-treatment between 1 to 4 years prior to clinical relapse and the fourth patient progressed whilst on maintenance treatment. Conclusion We report single-institution MRD data on unselected MM patients who have durable MRD and imaging-negative remission for at least 5 years from their latest line of therapy. The estimated 10-year risk of disease-progression in our cohort is around 8.6%, with the majority of patients being off-therapy. The low rate of disease-progression at 10 years demonstrates that a proportion of MM patients do not suffer multiple relapses and may therefore be potential candidates for discontinuation of maintenance. From our data, these patients are more often ISS stage I, have standard risk cytogenetics and achieve deep responses to frontline therapy. A smaller proportion of patients are able to achieve this landmark even after salvage therapies. This may be increasingly possible in the era of monoclonal antibodies and T cell redirection therapies. Analysis of larger real-world MM cohorts is needed to elucidate whether sustained MRD-negative remission at 5 years can truly predict long-term disease-free survival and possible cure.

Idarubicin Plus Azacitidine + Venetoclax As Induction Therapy Achieved High Remission in Elderly Fit- Acute Myeloid Leukemia Patients: Preliminary Results of a Phase II Study

Background The diagnosed age of de novo acute myeloid leukemia (AML) increased over the years, with a median current age of 68 years old. Elderly AML patients characterized by harboring high-risk mutations and significant comorbidities, usually display resistance to conventional chemotherapy, leading to poor outcomes. Although encouraging results from VIALE-A were reported in these years, over 30% participants had limited responses to the regimen of azacitidine + venetoclax after first-cycle induction. Thus, the selection of initial regimen for elderly AML is worth further exploration, especially for those with good fitness (the fitness was evaluated based on the physical ability, emotional status, cognitive function, and comorbidities). Here, we added idarubicin to azacitidine + venetoclax as the induction regimen (IAV regimen) for elderly fit-AML, and reported the preliminary results of efficacy and safety. Methods This single-center, single-arm, phase II trial (ChiCTR2300070190) was conducted at Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Shanghai, China). Elderly patients (aged 60-75 years) of newly diagnosed acute myeloid leukemia (AML) were assessed via modified comprehensive geriatric assessment (mCGA) for the fitness. From April 2023, 22 patients have been enrolled for the treatment of IAV regimen (cycle 1: IDA 6 mg/m 2 d1-3, AZA 75 mg/m 2 d1-7, VEN 100 mg d1, 200 mg d2, 400 mg d3-14; cycle 2: IDA 6 mg/m 2 d1-2, AZA 75 mg/m 2 d1-5, VEN 400 mg d1-14). Among them, 19 patients and 13 patients who have completed cycle 1 and cycle 2 treatment, respectively, were available for analyzing the preliminary efficacy and safety in the trial. The primary objective of this study was to access the composite complete remission (cCR: CR + CRi) rate of IAV treatment. The secondary objective was to evaluate the MRD-negative rate, regimen-related toxicity, and safety. The duration of CR, overall survival rate and event-free survival rate would also be further accessed with sufficient follow-up time. Results The median age of currently enrolled patients was 64 (61-69) years old, and males accounted for 68.4%. Detailed baseline characters were summarized in Table 1. Composite complete remission rate after 1-cycle IAV treatment was achieved in 89.5% (17/19) participants, among which 52.9% (9/17) got MRD-negative status. One patient (1/19, 5.26%) got partial remission, with 7.5% blasts remained. After cycle 2 treatment, the CR rate increased to 92.9% (13/14), and 92.3% (12/13) CR participants were MRD-negative (Table 1). Till now, only 1 patient with chromothripsis-associated rearrangements showed no response and died on day 40 after treatment initiation. The median recovery time of neutrophils (ANC &amp;gt; 0.5×10 9/L) and platelet (PLT &amp;gt; 50×10 9/L) was 20.5 (16-30) days and 20.5 (15-43) days, respectively (Table 1). The most frequent grade 3/4 non-hematological adverse events (according to CTCAE version 5.0) were febrile neutropenia (grade 3, n = 14; grade 4, n = 5), pneumonia (grade 3, n = 5) and sepsis (grade 3, n = 2; grade 4, n = 1) (Table 2). Conclusion In this study, IAV regimen showed promising efficacy on elderly fit-AML patients, with high rates of MRD-negative remission. Non-hematological toxicities were tolerable under current observation. Based on the invigorating preliminary results, the efficacy and potential benefit of IAV regimen on elderly fit AML is worthy of follow-up in the future.

Dendritic Cell Vaccines Extend CD19 CAR-T Cell Persistence and Improve the Outcomes in Refractory/Relapsed Adult B-ALL

Introduction: The long-term efficacy of anti-CD19 chimeric antigen receptor (CAR)-T cell in refractory or relapsed (r/r) adult B-cell acute lymphoblastic (B-ALL) patients is limited, and the recurrence rate is high. CAR-T cell depletion and limited CAR-T cell persistence are some of the most common reasons for relapse. Our previous in vitro studies confirmed that dendritic cell (DC) vaccines targeting tumor antigens could induce CAR-T cell rejuvenation and increase the killing function of CAR-T cells. So, we designed a clinical trial to study CD19 CAR-T cell combined with DC vaccination for adult r/r B-ALL to explore whether this therapy improves LFS. (clinicaltrials.gov, no: NCT03291444). Methods: Adult r/r B-ALL patients who expressed HLA-A1101, A2402, or A0201 and had high expression of EPS8 or WT1 were eligible. An EPS8 peptide-derived DC (EPS8-DCs) vaccine was used in EPS8-high patients, while a WT1 peptide-derived DC (WT1-DC) vaccine was used in EPS8-negative patients with WT1 positivity. Lymphodepleting chemotherapy comprising fludarabine (30 mg/m²) and cyclophosphamide (300 mg/m²) was administered intravenously daily for 3 days before CD19 CAR-T cells infusion. After 4 weeks of CAR-T infusion, if bone marrow morphologic remission had been achieved, DC vaccination was administered intradermally every 2 weeks for 4 doses. Results: Eight adult patients with r/r B-ALL were enrolled and successfully received CAR-T cells and DC cells, of which 4 (50%) relapsed after allogeneic hematopoietic stem cell transplantation. They were successfully administered one dose of CD19 CAR-T with a median dose of 2.26×10 6/kg (range 6.4×10 5/kg to 4.46×10 6/kg) on day 0 and four doses of DC vaccination with a median dose of 5.44×10 6 (range 2.97×10 6/dose to 2.68×10 7/dose) every 2 weeks after 4 weeks of CAR-T infusion. All eight evaluable patients achieved complete response (CR) after receiving CD19 CAR-T. With a median follow-up of 608 days, the median LFS time was 489 days, and the median OS was not reached. Seven of the eight evaluable patients were still alive. Four (50%) were in continuous MRD-negative remission at the cutoff time, and two of them (pt 02 and pt 03) maintained MRD-negative CR for more than 4 years. The median peak of CAR-T cell expansion in the PB was detected on day 7 after infusion of CD19 CAR-T. The median persistence time of CAR-T was 336 days (range 84 to 1549 days). CAR-T cells were reamplified after infusion of the DC vaccine. For patients with an LFS of more than 2 years (pt 02, pt 03, and pt 05), CD19 CAR-T cells were still detectable for more than 1 year, with a maximum of 4.2 years in pt 03. The activity of the CTLs measured by IFN-γ ELIspot showed that IFN-γ-secreting CTLs were significantly increased after DC vaccination. These assays showed that antigen-specific cellular immune activity was enhanced after vaccination. No grade ≥3 cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) occurred after infusion of 4sCAR19. No grade ≥3 events occurred during the infusion of the DC vaccine. Only 1 of 8 patients experienced local skin reactions after infusion of the DC vaccine. Conclusions: This study reports a novel combination therapy strategy (CAR-T cell combining with individualized DC vaccination) for adult r/r B-ALL. DC vaccination has higher safety, may prolong the persistence of CAR-T cells, and may prolong the survival time and quality of life. CAR-T cell therapy combining with DC vaccination is a potential therapy strategy for adult r/r ALL patients who are not eligible for transplantation or who relapse after transplantation.

Prophylactic or Preemptive Donor-Derived CD19 CAR-T Cell Infusion for Preventing Relapse in High-Risk B-ALL after Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: Relapse remains a significant challenge in the management of high-risk B-cell acute lymphoblastic leukemia (B-ALL) patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Existing post-transplant relapse prevention strategies for high-risk B-ALL patients after transplantation, particularly in cases of Philadelphia chromosome-negative B-ALL, have limitations and suboptimal efficacy. This study aims to evaluate the efficacy and safety profile of prophylactic or preemptive infusion of donor-derived CD19 chimeric antigen receptor T (CAR-T) cells in high-risk B-ALL patients after allo-HSCT. Methods: Between May 2017 and July 2022, high-risk B-ALL patients with minimal residual disease (MRD) positive or MRD negative status after allo-HSCT were enrolled in clinical trials of donor-derived CD19 CAR-T cell therapy (ChiCTR 2000041025 and ChiCTR-ONN-16009862). The primary outcome was the cumulative incidence of relapse (CIR). Secondary outcomes were progression-free survival (PFS), overall survival (OS) and CAR-T cell treatment-related toxicities. Results: A total of 25 high-risk B-ALL patients who received infusion of donor-derived CD19 CAR-T cells after allo-HSCT were enrolled in the CAR-T cell group, including 8 patients with MRD and 17 patients without MRD. A contemporaneous cohort of 43 high-risk B-ALL patients who did not receive CAR-T cell therapy in MRD-positive or MRD-negative status after transplantation was also included as a control group. The median age of patients enrolled in the CAR-T group was 29 years (range: 9-60 years). The median infused CAR-T cell dose was 2.5×10^6/kg (range: 1.0-5.0×10^6/kg), with a median time from transplantation to CAR-T cell treatment of 122 days (range: 45-315 days). The median follow-up duration was 23.6 months (range: 8.3-60.6 months). Of the 25 patients in CAR-T group, eight MRD-positive patients achieved MRD-negative remission after CAR-T cells treatment (Figure1A). The two-year cumulative incidence of relapse in the CAR-T cell group was significantly lower at 4.8% (95% CI: 0.0%-12.6%) compared to the control group's incidence of 26.6% (95% CI: 11.4%-41.8%, P = 0.03，Figure1B). Additionally, the CAR-T cell group exhibited a higher two-year PFS rate [86.3% (95% CI: 71.8%-100%)] compared to the control group [63.5% (95% CI: 48.0%-79.0%), P = 0.04]. However, the two-year OS rates were comparable between the CAR-T cell group [91.0% (95% CI: 79.0%-100%)] and the control group [79.1% (95% CI: 66.0%-92.2%), P = 0.20]. Adverse events were well tolerated, and no patients experienced grade 3-4 cytokine release syndrome or any grade of immune effector cell-associated neurotoxicity syndrome. Hematological cytopenia was the most severe CAR-T cell related toxicity, but the toxicity was manageable, and only three patients experienced acute graft-versus-host disease following CAR-T cell infusion. Conclusions: Prophylactic or preemptive infusion of CAR-T cells after allo-HSCT demonstrated a reduced incidence of relapse and acceptable adverse events in high-risk B-ALL patients. These findings highlight the potential of CAR-T cell therapy as a promising strategy for relapse prevention in high-risk B-ALL patients after allo-HSCT.

Blinatumomab Therapy Is Associated with Favorable Outcomes after Allogeneic Hematopoietic Cell Transplantation in Pediatric Patients with B Cell Acute Lymphoblastic Leukemia

Blinatumomab, a bispecific T cell engager that binds CD19 in leukemic cells and CD3 in cytotoxic T cells and leads to leukemic blast lysis, is often used in pediatric patients with relapsed/refractory (R/R) B cell acute lymphoblastic leukemia (B-ALL) prior to allogeneic hematopoietic cell transplantation (allo-HCT). Concerns about the potential risk of blinatumomab-related immune-mediated toxicities after allo-HCT have not been adequately addressed. These include graft-versus-host disease (GVHD), delayed engraftment, and graft failure or rejection. Pediatric-specific data reporting post-HCT outcomes of patients treated with blinatumomab are scarce and limited to small cohorts. We sought to investigate the clinical outcomes of pediatric patients with R/R B-ALL who received blinatumomab therapy pre-HCT, focusing on overall survival (OS), leukemia-free survival (LFS), cumulative incidence of relapse (CIR), and nonrelapse mortality (NRM), as well as the incidence of immune-mediated post-HCT complications including GVHD, delayed neutrophil or platelet engraftment, graft failure, and graft rejection. We also investigated blinatumomab's effects on B cell reconstitution based on achievement of i.v. immunoglobulin (IVIG) independence post-HCT. This single-center, retrospective study included patients with B-ALL receiving blinatumomab therapy before undergoing allo-HCT, with transplantation performed between 2016 and 2021 at our institution. Patients receiving blinatumomab for relapse after allo-HCT were excluded. Patients receiving chemotherapy alone before allo-HCT during the same period composed the control group. Seventy-two patients were included, 31 of whom received blinatumomab before allo-HCT. Survival estimates were obtained using the Kaplan-Meier method, and the log-rank test was used to analyze differences between groups. Categorical variables were compared between groups using the chi-square test or Fisher exact test, and continuous variables were compared using the Wilcoxon rank-sum test. Cumulative incidences were estimated using the competing risks method, and Gray's test was used to analyze differences between groups. A Cox proportional hazards regression model was used for univariate and multivariable analyses for OS. Landmark analysis was performed at the set time points of 30 days and 100 days post-allo-HCT. Most patients in the study cohort had high-risk relapsed B-ALL. Blinatumomab therapy induced minimal residual disease (MRD)-negative remissions in all patients, whereas 5 patients (12.2%) receiving chemotherapy alone had persistent MRD pre-allo-HCT. Time from the start of therapy to the date of allo-HCT was shorter for patients who received blinatumomab compared with those who received chemotherapy (P < .0001). Blinatumomab therapy was associated with greater LFS compared to chemotherapy alone (P = .049), but when limited to 1 year, LFS was not significantly different from control (P = .066). There appeared to be higher OS, lower CIR, and lower NRM in patients receiving blinatumomab compared to the control group; however, the differences were not significant. None of the variables assessed in multivariable analysis was associated with differences in OS. When compared to the controls, blinatumomab therapy did not result in a higher incidence of acute or chronic GVHD, delayed neutrophil or platelet engraftment, or graft failure or rejection. The time to IVIG infusion independence post-allo-HCT was similar in the 2 groups. This study supports the use of blinatumomab salvage therapy for R/R B-ALL before allo-HCT given its efficacy in inducing MRD-negative remissions and optimizing LFS, as well as its lack of association with an increased incidence of post-allo-HCT adverse immune-mediated toxicities. Larger, prospective studies are needed to confirm these findings and to investigate blinatumomab's effects in long-term post-allo-HCT events.