Minimal Residual Disease-negative Complete Remission Research Articles

Comprehensive analysis of the efficacy and safety of CAR T-cell therapy in patients with relapsed or refractory B-cell acute lymphoblastic leukaemia: a systematic review and meta-analysis

Background Relapse/refractory B-cell acute lymphoblastic leukaemia (r/r B-ALL) represents paediatric cancer with a challenging prognosis. CAR T-cell treatment, considered an advanced treatment, remains controversial due to high relapse rates and adverse events. This study assessed the efficacy and safety of CAR T-cell therapy for r/r B-ALL. Methods The literature search was performed on four databases. Efficacy parameters included minimal residual disease negative complete remission (MRD-CR) and relapse rate (RR). Safety parameters constituted cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Results Anti-CD22 showed superior efficacy with the highest MRD-CR event rate and lowest RR, compared to anti-CD19. Combining CAR T-cell therapy with haploidentical stem cell transplantation improved RR. Safety-wise, bispecific anti-CD19/22 had the lowest CRS rate, and anti-CD22 showed the fewest ICANS. Analysis of the costimulatory receptors showed that adding CD28ζ to anti-CD19 CAR T-cell demonstrated superior efficacy in reducing relapses with favorable safety profiles. Conclusion Choosing a more efficacious and safer CAR T-cell treatment is crucial for improving overall survival in acute leukaemia. Beyond the promising anti-CD22 CAR T-cell, exploring costimulatory domains and new CD targets could enhance treatment effectiveness for r/r B-ALL.

Sequential CD7 CAR T-Cell Therapy and Allogeneic HSCT without GVHD Prophylaxis

BackgroundPatients with relapsed or refractory hematologic cancers have a poor prognosis. Chimeric antigen receptor (CAR) T-cell therapy as a bridge to allogeneic hematopoietic stem-cell transplantation (HSCT) has the potential for long-term tumor elimination. However, pre-HSCT myeloablation and graft-versus-host disease (GVHD) prophylaxis agents have toxic effects and could eradicate residual CAR T cells and compromise antitumor effects. Whether the integration of CAR T-cell therapy and allogeneic HSCT can preserve CAR T-cell function and improve tumor control is unclear.MethodsWe tested a novel “all-in-one” strategy consisting of sequential CD7 CAR T-cell therapy and haploidentical HSCT in 10 patients with relapsed or refractory CD7-positive leukemia or lymphoma. After CAR T-cell therapy led to complete remission with incomplete hematologic recovery, patients received haploidentical HSCT without pharmacologic myeloablation or GVHD prophylaxis drugs. Toxic effects and efficacy were closely monitored.ResultsAfter CAR T-cell therapy, all 10 patients had complete remission with incomplete hematologic recovery and grade 4 pancytopenia. After haploidentical HSCT, 1 patient died on day 13 of septic shock and encephalitis, 8 patients had full donor chimerism, and 1 patient had autologous hematopoiesis. Three patients had grade 2 HSCT-associated acute GVHD. The median follow-up was 15.1 months (range, 3.1 to 24.0) after CAR T-cell therapy. Six patients remained in minimal residual disease–negative complete remission, 2 had a relapse of CD7-negative leukemia, and 1 died of septic shock at 3.7 months. The estimated 1-year overall survival was 68% (95% confidence interval [CI], 43 to 100), and the estimated 1-year disease-free survival was 54% (95% CI, 29 to 100).ConclusionsOur findings suggest that sequential CD7 CAR T-cell therapy and haploidentical HSCT is safe and effective, with remission and serious but reversible adverse events. This strategy offers a feasible approach for patients with CD7-positive tumors who are ineligible for conventional allogeneic HSCT. (Funded by the National Natural Science Foundation of China and the Key Project of Science and Technology Department of Zhejiang Province; ClinicalTrials.gov numbers, NCT04599556 and NCT04538599.)

Abstract CT180: Phase I clinical trial of CD19CAR -T cells secreting PD-1-targeting IL-21 in advanced relapsed/refractory acute lymphoblastic leukemia

Abstract Background/Purpose: Chimeric antigen receptor (CAR) T cell therapy has shown remarkable responses in hematologic malignancies. However, suboptimal clinical outcomes have been associated with decreased expansion and persistence of adoptive transferred CAR-T cells, antigen-negative relapses, and impairment by an immunosuppressive tumor microenvironment. We previously developed CD19CAR-T cells secreting PD-1Ab21 fusion protein composed of anti-PD-1 single chain antibody and IL-21(PD-1Ab21-CD19CAR-T). This investigator-initiated clinical trial is designed to assess the safety and efficacy of the novel CAR-T cells in advanced relapsed/refractory acute Lymphoblastic leukemia (ALL). Methods: This study recruited 10 patients with advanced relapsed/refractory B-ALL and half of them relapsed after allogeneic hematopoietic stem cell transplantation (allo-HSCT). All patients received fludarabine and cyclophosphamide before a single infusion of PD-1Ab21-CD19CAR-T cells at dose of 0.3, 1 or 3 x 106 cells/kg of body weight. The patients were monitored for adverse events, clinical response, as well as expansion of CAR-T and lymphocytes. Results: All five non-post-transplant patients achieved complete remission (CR), including two active CNS diseases, and three of them pursued consolidative allo-HSCT. Among the five post-transplant patients, one patient, who had undergone autologous, allogeneic CAR-T cell therapies and allo-HSCT, achieved CR and remained leukemia-free for 5 months, which was longer than the duration of remission (< 4 monthes) after allo-HSCT. The last treated patient achieved CR. Three other post-transplant patients, including two active CNS diseases, eventually died of the infection. One of the patients achieved minimal residual disease negative CR. The other two patients did not undergo laboratory evaluation, but their CNS symptoms disappeared. Once the expansion of CAR-T cells was detected, the proportion of CD8+T cell in CD3+T cells increased dramatically, rapidly reaching 77.8~91.2% and maintaining above 50% for a long time in all treated patients. Except for the three patients who died from infection, other patients experienced no or mild cytokine release syndrome (CRS) (grade ≤2). None of the patients had neurotoxic side effects. Conclusion: This study demonstrates that PD-1Ab21-secreting CAR-T cells are safe and effective therapeutic platform, even in cancer patients with CNS invasion. Our data also suggest that PD-1Ab21-secreting CAR-T therapy can activate endogenous anti-tumor CD8+ T cell responses. Citation Format: Yu Jing, Ying Li, Liping Dou, Shengjuan Zhang, Ran Tian, Guojing Wang, Xiangrui Cheng, Jitao Zhao, Hang Li, Yueyi An, Naibo Yang, Shengdian Wang. Phase I clinical trial of CD19CAR -T cells secreting PD-1-targeting IL-21 in advanced relapsed/refractory acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT180.

Safety and efficacy of donor-derived chimeric antigen receptor T-cell therapy in patients with relapsed B-cell acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation

Objective: To investigated the safety and efficacy of donor-derived CD19+ or sequential CD19+ CD22+ chimeric antigen receptor T-cell (CAR-T) therapy in patients with B-cell acute lymphoblastic leukemia (B-ALL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods: The data of 22 patients with B-ALL who relapsed after allo-HSCT and who underwent donor-derived CAR-T therapy at the Zhujiang Hospital of Southern Medical University and the 920th Hospital of Joint Logistics Support Force of the People's Liberation Army of China from September 2015 to December 2022 were retrospectively analyzed. The primary endpoint was overall survival (OS), and the secondary endpoints were event-free survival (EFS), complete remission (CR) rate, and Grade 3-4 adverse events. Results: A total of 81.82% (n=18) of the 22 patients achieved minimal residual disease-negative CR after CAR-T infusion. The median follow-up time was 1037 (95% CI 546-1509) days, and the median OS and EFS were 287 (95% CI 132-441) days and 212 (95% CI 120-303) days, respectively. The 6-month OS and EFS rates were 67.90% (95% CI 48.30%-84.50%) and 58.70% (95% CI 37.92%-79.48%), respectively, and the 1-year OS and EFS rates were 41.10% (95% CI 19.15%-63.05%) and 34.30% (95% CI 13.92%-54.68%), respectively. Grade 1-2 cytokine release syndrome occurred in 36.36% (n=8) of the patients, and grade 3-4 occurred in 13.64% of the patients (n=3). Grade 2 and 4 graft-versus-host disease occurred in two patients. Conclusion: Donor-derived CAR-T therapy is safe and effective in patients with relapsed B-ALL after allo-HSCT.

Minimal Residual Disease-Negative Complete Remission at the End of Induction Is a Prognostic Indicator of Long-Term Survival in Adult Patients with Ph+ Acute Lymphoblastic Leukemia Receiving First-Line Therapy

Background: Minimal residual disease (MRD) is an established, prognostic indicator for patients with acute lymphoblastic leukemia (ALL), including Philadelphia chromosome-positive (Ph+) ALL. The objective of this study was to evaluate the association between MRD and long-term outcomes (event-free survival [EFS] and overall survival [OS]) in adult patients with Ph+ ALL receiving first-line therapy. Methods: A systematic literature review (SLR) was performed to identify eligible studies, including interventional and observational studies reporting survival outcomes by MRD status in adults ≥18 years of age with Ph+ ALL receiving first-line therapy. Key outcomes and data elements of interest were EFS, OS, and MRD or MRD-negative complete remission (CR) at end of induction (EOI). Aggregate study-level and individual patient data (IPD) meta-analyses were conducted. The IPD approach included a log-level MRD analysis to evaluate the concordance of deepening levels of molecular response with long-term EFS or OS in patients with CR and an analysis evaluating the utility of MRD-negative CR over CR alone. The analyses were conducted using frequentist and Bayesian approaches with fixed-effects and random-effects models. Kaplan-Meier method with log-rank tests was used for survival analysis. Where applicable, Cox regression method with and without adjustment for prognostic factors were applied. Results: The SLR identified 19 publications (18 unique studies), 10 (9 unique studies) of which had sufficient MRD and EFS/OS data. Nine studies (n=704) were included in the aggregate study-level analysis; 3 of the 9 studies (Phase II AP24534-11-001 [Jabbour et al. 2015], Phase II GIMEMAINCB 84344-201 [Martinelli et al. 2017], and Phase III GRAAPH-2005 RCT [Chalandon et al. 2015]) had IPD available. MRD was assessed by polymerase chain reaction in all 9 studies. Findings from the aggregate study-level meta-analysis demonstrated a significant long-term survival benefit (EFS and OS) in favor of patients with MRD-negative CR. This significant benefit was generally consistent across analysis types (base-case or sensitivity analyses), analytic models (fixed- or random-effects), and approaches (frequentist or Bayesian). Evidence from the IPD analysis, based on patients with CR, was mostly consistent with the aggregate study-level meta-analysis, supporting MRD-negative CR at the EOI as being predictive of EFS or OS. Log-level MRD analysis showed that patients who are in CR with deeper molecular response ( BCR::ABL1/ABL1 ≤0.01%) at EOI have significantly better long-term EFS and OS compared with patients with other levels of MRD (ie, BCR::ABL1/ABL1 >0.01%). This significant long-term survival benefit was also demonstrated in patients with MRD-negative CR ( BCR::ABL1/ABL1 ≤0.01%) at EOI compared with patients who were MRD-positive ( BCR::ABL1/ABL1 >0.01%) ( Table 1) or based on achievement of CR alone (regardless of BCR::ABL1/ABL1 values). Results from the IPD analysis standardized for outcome definition, with and without adjustment for prognostic factors (age, gender, white blood cell count at baseline, and stem cell transplant), were consistent with the findings from the log-level MRD analysis. The analysis showed a significant association between MRD-negative/MRD-negative CR status (ie, BCR::ABL1/ABL1 ≤0.01% threshold) at EOI with improved long-term EFS and OS. The results were significant for EFS in both the adjusted and unadjusted models. The OS results were significant only in the unadjusted model. Conclusions: These analyses indicate that a deeper molecular response at EOI results in better long-term EFS and OS; MRD-negative CR has a greater prognostic value than CR and is strongly associated with long-term EFS and OS in patients with Ph+ ALL. Acknowledgement: The authors acknowledge APHP, who provided the individualized patients data for the GRAAPH study.

CD33 CAR T-Cells (CD33CART) for Children and Young Adults with Relapsed/Refractory AML: Dose-Escalation Results from a Phase I/II Multicenter Trial

Introduction: Current therapies for patients with acute myeloid leukemia (AML) push the limits of chemotherapy intensity but cure only 30% of adults and 70% of children. Recently developed antibody-based therapies and molecularly-targeted agents only modestly improve outcomes for select patient subsets. Thus, new approaches are needed. Given the success of chimeric antigen receptor (CAR) T-cell therapies for acute lymphoblastic leukemia (ALL), we developed and optimized a novel CD33 CAR T-cell (CD33CART) construct for clinical testing in a multicenter Phase I/II clinical trial in children, adolescents, and young adults (AYA) with relapsed/refractory (r/r) AML. ( Qin H, et al. JITC 2021) We report interim results following completion of the dose-escalation phase. Methods: This multicenter phase I/II clinical trial (NCT03971799) was conducted as a 3+3 dose escalation study through the Pediatric Transplantation and Cell Therapy Consortium with National Marrow Donor Program sponsorship and managed by CIBMTR CRO. Autologous CD33CART product were centrally manufactured on a ClinicMACS Prodigy® by the Biopharmaceutical Development Program at the Frederick National Laboratory for Cancer Research (NCI). Eligibility criteria were r/r AML in subjects < 35 years old with adequate organ/performance status and an identified allogeneic stem cell transplant (SCT) donor. Bone marrow assessment was used for standard morphologic evaluation and central flow cytometric minimal residual disease (MRD) quantification. All subjects received pre-CD33CART lymphodepleting chemotherapy (LD) with fludarabine (75-120 mg/m 2) and cyclophosphamide (900-1000 mg/m 2). CD33CART doses levels (DLs) were: DL1: 3 x 10 5 CD33 CAR+ T-cells/kg; DL2: 1 x 10 6/kg; DL3: 3 x 10 6/kg and DL4: 1 x 10 7/kg. Adverse event grading used CTCAE v5 with incorporation of ASTCT consensus definitions for cytokine release syndrome (CRS) and immune effector cell associated neurotoxicity syndrome (ICANS). Dose-limiting toxicities (DLTs) included > grade 3 CRS, > grade 3 ICANS, and persistent > grade 3 non-hematologic toxicity that did not resolve < grade 2 in 72 hours. CD33CART persistence was assessed via flow cytometric evaluation of the blood and bone marrow. Data cut-off was June 1, 2023. Results: A total of 24 subjects (median age of 16 years, range 1-34 years), were enrolled, 12 (50%) of whom underwent a prior SCT. CD33CART products were successfully manufactured for 23 subjects and infused into 19. In 4 non-infused subjects with manufactured products, 1 died from progressive disease (PD) prior to LD, 2 transitioned to palliative care and 1 withdrew consent to seek alternative therapy. Manufacturing was not performed in one subject due to death from PD after enrollment. One morbidly obese subject (BMI=49.3) enrolled at DL4 but received treatment at DL3 due to weight-based manufacturing limitations. The median time from enrollment to infusion was 47 days (range, 24-242). (Table) Three subjects each were infused at DL1 and DL2 without DLTs. At DL3, 1 subject experienced DLT (grade 4 CRS) prompting expansion at this dose level, and no subsequent DLTs were observed. At DL4, 1 subject experienced a prolonged grade 3 CRS (> 72 hours) and grade 3 ICANS, both constituting DLT and necessitating expansion of the cohort without additional DLTs seen. Across all dose-levels, CRS was seen in 13 (68%) patients and was > grade 3 in 4 (21%) with onset typically within the first 24 hours post-infusion. Complete remission (CR) was only seen at DL4 and achieved in 2 subjects, both achieving an MRD negative CR alongside myeloid aplasia. One SCT naïve subject developed candidemia during aplasia but was able to proceed to an allogenic SCT, achieved engraftment, and was in remission at Day +100 post SCT. The second patient (post-two prior SCTs) declined third SCT, had spontaneous count recovery and remained in remission until day +119 (MRD+ relapse). Transient CD33CART expansion was detected in 9 (47.4%) subjects overall and in all 6 (100%) subjects at DL4. Conclusions: CD33CART manufacturing is feasible in children and AYAs with r/r AML with acceptable toxicity experienced in treated subjects. CD33CART expansion was best in subjects treated at DL4 (1 x 10 7/kg) with MRD negative CRs and transient myeloid aplasia occurring in 2 of 5 (40%) subjects evaluable for response (Table). Based on early clinical efficacy at DL4, enrollment continues in the phase 2 portion.

Sequential CD19 and CD22 chimeric antigen receptor T-cell therapy for childhood refractory or relapsed B-cell acute lymphocytic leukaemia: a single-arm, phase 2 study

Relapses frequently occur following CD19-directed chimeric antigen receptor (CAR) T-cell treatment for relapsed or refractory B-cell acute lymphocytic leukaemia in children. We aimed to assess the activity and safety of sequential CD19-directed and CD22-directed CAR T-cell treatments. This single-centre, single-arm, phase 2 trial, done at Beijing GoBroad Boren Hospital, Beijing, China, included patients aged 1-18 years who had relapsed or refractory B-cell acute lymphocytic leukaemia with CD19 and CD22 positivity greater than 95% and an Eastern Cooperative Oncology Group performance status of 0-2. Patients were initially infused with CD19-directed CAR T cells intravenously, followed by CD22-directed CAR T-cell infusion after minimal residual disease-negative complete remission (or complete remission with incomplete haematological recovery) was reached and all adverse events (except haematological adverse events) were grade 2 or better. The target dose for each infusion was 0·5 × 106 to 5·0 × 106 cells per kg. The primary endpoint was objective response rate at 3 months after the first infusion. Secondary endpoints were duration of remission, event-free survival, disease-free survival, overall survival, safety, pharmacokinetics, and B-cell quantification. The prespecified activity analysis included patients who received the target dose and the safety analysis included all treated patients. This study is registered with ClinicalTrials.gov, NCT04340154, and enrolment has ended. Between May 28, 2020, and Aug 16, 2022, 81 participants were enrolled, of whom 31 (38%) were female and 50 (62%) were male. Median age was 8 years (IQR 6-10), all patients were Asian. All 81 patients received the first infusion and 79 (98%) patients received sequential infusions, CD19-directed CAR T cells at a median dose of 2·7 × 106 per kg (IQR 1·1 × 106 to 3·7 × 106) and CD22-directed CAR T cells at a median dose of 2·2 × 106 per kg (1·1 × 106 to 3·7 × 106), with a median interval of 39 days (37-41) between the two infusions. 62 (77%) patients received the target dose, including two patients who did not receive CD22 CAR T cells. At 3 months, 60 (97%, 95% CI 89-100) of the 62 patients who received the target dose had an objective response. Median follow-up was 17·7 months (IQR 11·4-20·9). 18-month event-free survival for patients who received the target dose was 79% (95% CI 66-91), duration of remission was 80% (68-92), and disease-free survival was 80% (68-92) with transplantation censoring; overall survival was 96% (91-100). Common adverse events of grade 3 or 4 between CD19-directed CAR T-cell infusion and 30 days after CD22-directed CAR T-cell infusion included cytopenias (64 [79%] of 81 patients), cytokine release syndrome (15 [19%]), neurotoxicity (four [5%]), and infections (five [6%]). Non-haematological adverse events of grade 3 or worse more than 30 days after CD22-directed CAR T-cell infusion occurred in six (8%) of 79 patients. No treatment-related deaths occurred. CAR T-cell expansion was observed in all patients, with a median peak at 9 days (IQR 7-14) after CD19-directed and 12 days (10-15) after CD22-directed CAR T-cell infusion. At data cutoff, 35 (45%) of 77 evaluable patients had CAR transgenes and 59 (77%) had B-cell aplasia. This sequential strategy induced deep and sustained responses with an acceptable toxicity profile, and thus potentially provides long-term benefits for children with this condition. The National Key Research & Development Program of China, the CAMS Innovation Fund for Medical Sciences (CIFMS), and the Non-Profit Central Research Institute Fund of Chinese Academy of Medical Sciences. For the Chinese translation of the abstract see Supplementary Materials section.

Which one is better for refractory/relapsed acute B-cell lymphoblastic leukemia: Single-target (CD19) or dual-target (tandem or sequential CD19/CD22) CAR T-cell therapy?

CD19 chimeric antigen receptor (CAR) T-cell therapy has shown great success against B-cell acute lymphoblastic leukemia (B-ALL). Tandem and sequential CD19/CD22 dual-target CAR T-cell therapies have been developed to reduce the possibility of CD19-negative relapse; however, the superior strategy is still uncertain. This study screened 219 patients with relapsed/refractory B-ALL who were enrolled in clinical trials of either CD19 (NCT03919240) or CD19/CD22 CAR T-cell therapy (NCT03614858). The complete remission (CR) rates in the single CD19, tandem CD19/CD22, and sequential CD19/CD22 groups were 83.0% (122/147), 98.0% (50/51), and 95.2% (20/21), respectively (single CD19 vs. tandem CD19/CD22, P = 0.006). Patients with high-risk factors achieved a higher rate of CR in the tandem CD19/CD22 group than in the single CD19 group (100.0% vs. 82.4%, P = 0.017). Tandem CD19/CD22 CAR T-cell therapy was one of the significant favorable factors in the multivariate analysis of the CR rate. The incidence of adverse events was similar among the three groups. Multivariable analysis in CR patients showed that a low frequency of relapse, a low tumor burden, minimal residual disease-negative CR and bridging to transplantation were independently associated with better leukemia-free survival. Our findings suggested that tandem CD19/CD22 CAR T-cell therapy obtains a better response than CD19 CAR T-cell therapy and a similar response to sequential CD19/CD22 CAR T-cell therapy.

Targeted Therapy With Venetoclax and Daratumumab as Part of HSCT Preparative Regimen in Children With Chemorefractory Acute Myeloid Leukemia

The long-term outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in chemorefractory acute myeloid leukemia (AML) remains suboptimal because of a high relapse rate. Enhancement of conditioning regimens by the incorporation of targeted anti-leukemia agents is a potential approach to improve the efficacy of HSCT. In a pilot trial and extended access cohort, we evaluated the safety and potential value of adding combinations of venetoclax and daratumumab to a preparative regimen among children with chemorefractory acute myeloid leukemia grafted with αβ T-cell–depleted peripheral blood stem cells. All 20 patients had active disease status of AML at the time of transplantation. The preparative regimen included myeloablative conditioning based on either total body irradiation or treosulfan. A haploidentical related donor was used as a graft source for all patients. Engraftment was not compromised, and no excess toxicity was noted. Minimal residual disease–negative complete remission was achieved in 17 patients (85%). The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 17%, and the cumulative incidence of chronic GVHD was 7%. At 2 years, nonrelapse mortality was 10%, relapse incidence was 46%, event-free survival was 44%, and overall survival was 65%. Our data show the possibility of safely adding targeted agents to conditioning regimens; however, no evidence of a significant improvement in long-term transplantation outcomes in this cohort of patients was observed.

Antigen Directed Therapy Pre-Transplant Confers Superior Post-Transplant Survival Outcome Compared to Conventional Chemotherapy in Pediatric Patients with Relapsed and Refractory B-ALL

Background: Hematopoietic stem cell transplant (HCT) represents the most effective mean to achieve cure for children, adolescents and young adults with relapsed or refractory (R/R) B-ALL. Among the several disease-specific and transplant-specific characteristics evaluated so far, achievement of minimal residual disease (MRD) negative complete remission (CR) prior to HCT is the strongest independent prognostic factor of post-HCT outcome. Antigen directed therapies (ADT) such as blinatumomab, inotuzumab ozogamicin and chimeric antigen receptor (CAR) T-cell are very effective at inducing MRD-negative remission and offer an alternative approach for disease control in patients with chemo-resistant disease. We hypothesized that ADT may provide a more durable disease control and lesser morbidity than conventional chemotherapy (CT) and therefore we sought to explore whether the type of treatment (ADT or CT) adopted to achieve MRD negative CR prior to HCT, impacts post-HCT outcomes. Patients and methods: This is a retrospective, multi-institutional cohort study of patients (pts) with R/R B-ALL who received an allogeneic HCT in MRD negative CR between 2010-2021. Patients were eligible if they were ≤30 years at time of diagnosis of R/R B-ALL, had received either CT or ADT (blinatumomab, CAR T-cell, inotuzumab ozogamicin with or without preceding chemotherapy) for the treatment of R/R B-ALL and had achieved MRD negative CR (<0.01% blasts by flow cytometry) prior to HCT. Patients with isolated extramedullary relapse or acute leukemia of ambiguous lineage or history of prior HCT were excluded. Patients were categorized as being in the "CT" or "ADT" group based on whether they received conventional CT or ADT as last cycle that led to MRD negativity prior to HCT. The primary objective of the study was to compare the EFS, OS and treatment related mortality (TRM) from time of transplant according to the therapy (ADT vs. CT) received pre-HCT. Kaplan-Meier or Aalen-Johansen estimates were used to estimate survival rates and curves were compared using logrank or Gray's tests. Results: Seventy-six pts from 7 centers met eligibility criteria; 38 pts (50.0%) received ADT and 38 pts (50.0%) received chemotherapy as last cycle prior to HCT. Demographic, disease and treatment characteristics are summarized in Table 1; notably, more pts in the ADT group had refractory leukemia and more pts had received ≥4 cycles of therapy before achieving MRD negative remission in the ADT group than in the CT group. The 5-yr. EFS and OS for the entire cohort were 53% and 67%, respectively. EFS was superior in the ADT group compared to the CT group (5-yr. EFS 64% vs. 42%, p=0.04; Figure 1). OS was also superior in the ADT group (85% vs. 47%, p=0.0008; Figure 1). In a univariable and multivariable prognostic model for OS that included age, race, having relapsed or refractory disease and CT or ADT as pre-HCT therapy, pre-HCT therapy was the only significant prognostic factor (p<0.001); in a similar model for EFS, pre-HCT therapy was the only significant prognostic factor in the univariable analysis (p=0.04) but not in the multivariable analysis. There was no difference in the incidence of acute GVHD, rate of immune reconstitution at day 100, time to engraftment and cumulative incidence of relapse between the two groups. However, the CT group appeared to have a higher rate of both TRM (33.0% vs. 8%, p=0.01) and relapse related mortality, although not significant for the latter (19% vs. 7% p=0.12). Conclusion: This multicenter study shows that having received ADT prior to HCT may be beneficial when compared to conventional chemotherapy for patients with R/R B-ALL who receive a HCT in MRD negative CR. Patients who received ADT experienced a superior EFS and OS primarily due to a significantly lower TRM, despite having received more cycles of therapy prior to proceeding to HCT. There was no difference in the relapse rate among the two groups further supporting the notion that MRD negative CR is the single most important predictor of post-HCT relapse. Further analysis is ongoing to identify specific factors that could explain the difference in post-HCT mortality among the 2 groups. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prognostic Relevance of Minimal Residual Disease in Therapy Related and Secondary Acute Myeloid Leukemia Receiving CPX-351 or Fludarabine-Based Induction

Background: The high prognostic value of minimal residual disease (MRD) assessment in Acute Myeloid Leukemia patients (AML) undergoing intensive induction therapy has been confirmed by several studies. The most widely adopted MRD techniques include multicolor flow cytometry (MFC), RT-PCR for recurrent genetic lesion and, for patients lacking specific markers, RT-PCR for the pan-leukemic marker WT1. However, mostly younger patients receiving a conventional 3+7 induction are included in clinical studies evaluating MRD in AML. As a consequence, secondary AML, evolving from a previous myelodisplastic syndrome (s-AML) or therapy-related AML (t-AML), which usually affect elderly AML patients are usually under-represented in those trials. Recently, CPX-351 was approved for the treatment of s-AML and t-AML, following the positive results of the Phase III trial by Lancet et al. However, as MRD was not assessed in this trial, only a limited ammount of data are available on the kinetics and the prognostic value of MRD in elderly s- AML and t-AML patients receiving CPX-351 induction. Aims: In order to assess the prognostic value and to define the best time points for MRD assessment, MFC-based and WT1 based MRD was evaluated in a cohort of elderly s-AML or t-AML patients receiving CPX-351 induction. Timepoints for assessment were after induction (TP1), after first consolidation (TP2) and at the end of treatment (TP3). As a comparison, we also evaluated MRD in a cohort of elderly s-AML and t-AML patients who received an age-adjusted fludarabine-containing regimen (FLAI3). MRD analysis in this cohort was performed with the same methodics and at the same timepoints. Methods: A total of 151 elderly (>60 year, median age 68, range 60-77) patients were analyzed in this study. Patients were treated between January 2005 and January 2020 in our Center, either with CPX-351 (n=50) or fludarabine- high dose cytarabine-idarubicin (FLAI), with (n=72) or without (n =29) gemtuzumab-ozogamicin (GO). MRD was analyzed in all patients achieving hematological complete remission (CR) with both MFC and WT1 expression levels. All patients were affected by s-AML or t-AML, defined according to the WHO 2016 criteria. Results: After first induction cycle, 95 patients (59%) achieved CR. Patients treated with CPX-351 had a significantly higher CR rate, if compared to patients receiving FLAI (40/50, 80% and 55/101, 54.5%, respectively, p<0.05). Adding GO to FLAI did not increase CR rate. Overall, in the two cohorts, an MRD negative CR was achieved in 51 (53.7%) and 53 responding patients (55.8%) assessed with MFC or WT1-based methods, respectively. The probability of achieving MFC MRD negativity was significantly higher among patients treated with CPX-351, when compared to patients receiving FLAI with or without GO (MFC MRD negativity rate of 26/40, 65% and 25/55, 45%, respectively, p<0.05). In both cohort, the most informative timepoint in terms of survival prediciton was after first cycle (TP1). WT1-based MRD assessment led to superimposable results. In multivariate analysis, MRD was significantly correlated with an higher probability of longer Overall Survival (OS) in all treatment group (2-year OS of 34% and 77% in patients with or without residual MFC MRD after induction, respectively, p<0.05). Allogeneic stem cell transplantation consolidation (HSCT) was also significantly correlated with longer OS in both treatment groups (p<0.05). Notably, 12/40 (30%) CR patients treated with CPX 351 underwent HSCT, whereas only 8 CR patients proceeded to HSCT in the FLAI group (15%) Conclusions: MRD assessment has a strong prognostic value also in the context of elderly s-AML and t-AML patients. WT1-based and MFC-based MRD assessment lead to similar conclusions thus allowing to obtain MRD data from virtually all AML patients treated in the selected time period. Overall, CPX-351 resulted in higher CR rate with deeper MRD responses, if compared to FLAI3. This increased efficacy translated in a significantly higher number of elderly AML patients proceeding to HSCT in CR, which is the only curative approach in this particular AML setting.

Inotuzumab Ozogamicin Induction Followed By Standard Chemotherapy Yields High Remission Rates and Promising Survival in Older (>55 Years) Patients with De Novo B-Lymphoblastic Leukemia (GMALL-Initial1 Trial)

Introduction: Acute lymphoblastic leukemia (ALL) represents approx. 5% of all newly diagnosed leukemias in patients (pts) between 55 and 70 years of age. Incorporation of novel antibody-based therapies in the first line induction therapy bears the potential of a significantly increased response rates and survival together with a reduction of treatment toxicity. Methods: This open label phase II study (ClinicalTrials.gov, identifier: NCT03460522) of the German Multicenter Study Group on Adult Acute Lymphoblastic Leukemia was conducted at 13 centers. Pts aged >55 years with newly diagnosed Ph/BCR-ABL negative B-precursor ALL (at least CD20 positivity of leukemic blasts) were eligible. The 1st induction cycle consisted of InO 0.8mg/m2 on day1 and 0.5mg/m2 on d8 and d15 together with dexamethasone 10 mg/m2 (day7-8, day14-17) and one intrathecal injection (i.th.) of methotrexate (MTX), cytarabine (AraC) and dexamethasone (Dex). The 2nd and 3rd induction cycle consisted of InO 0.5mg/m2 on day 1, 8 and 15 plus i.th. MTX/AraC/Dex. Pts achieving a complete remission (CR) were offered to receive 5 conventional consolidation therapies (3 x ID-MTX/asparaginase; 2 x ID-AraC) and one reinduction therapy (idarubicine/ AraC/ cyclophosphamide / Dex.) in combination with rituximab (for CD20+ ALL), followed by a maintenance therapy with 6-MP/MTX. The primary endpoint was event free survival (EFS) at 12-months follow-up. An event was defined as any of the following: persisting bone marrow blasts after 2 cycles of InO, relapse or death. An event rate of ≤40% at 12 months follow-up was considered to qualify the experimental treatment as very promising for additional testing. Results: 43 out of the 45 pts included were analyzed regarding the primary end point. Two pts were excluded per protocol from further analysis, as they received only one cycle of induction or withdraw consent. At diagnosis, median age was 64 years (range 56-80 years, 20 pts ≥65 years and 12 pts ≥70 years), median bone marrow blast count was 80% and median CD22 expression on leukemic blasts was 69% (range 21-99). 38 pts were diagnosed with a common- and 5 with a pro-B ALL. 42/43 pts completed all 3 cycles of induction therapy. All 43 pts achieved a complete remission (CR/CRi), mainly after the 1st induction. Median time between start of 1st induction to start 2nd induction, from 2nd to 3rd induction and from 3rd induction to 1st consolidation therapy was 21 days, 28 days and 30 days, respectively. Results of minimal residual disease (MRD), measured by real-time quantitative PCR, are available for all 43 pts, with 23/43 (53%) and 31/42 (74%) pts being MRD negative after 2nd and 3rd induction therapy, respectively. With a median follow-up of 697 days, the probability of OS at 1 and 2 years is 91% (95% C.I. 82-99%) and 81% (95% C.I. 69-94%), respectively. No patient died within the first 6 months after start of induction therapy. 5 events occurred within the first year after study inclusion, 3 deaths in CR and 2 relapsed ALL, resulting in event rate of 12% and a probability of EFS at 1 year (primary endpoint of the study) of 88% (95% CI 79-98). EFS at 2 years was 73% (95% CI 59-88). So far, 7 pts with persisting/reappearance of MRD (2 pts) or relapse (5 pts) were treated with blinatumomab. 9 pts received an aSCT (4 pts in CR1 and 5 pts >CR1), 6 of these pts are alive in CR. Regarding adverse events (AEs) during induction cycles 1, 2 and 3, most common AEs ≥CTC grade 3 reported were leukocytopenia (in 74%, 19% and 2% of all cases, respectively), anemia (37%, 5%, 0%), thrombocytopenia (49%, 7%, 2%) and elevation of liver enzymes (14%, 5%, 0%). One patient was reported with suspected veno occlusive disease (after 2nd induction therapy). Classical factors which may be associated with inferior survival outcomes like age, diagnosis of pro-B ALL, disease burden at diagnosis, co-morbidity or no MRD negative CR after induction had no significant impact on OS or EFS. Conclusion: Three cycles of InO as induction therapy for the treatment of older pts with de novo acute B-lymphoblastic leukemia resulted in a very high remission rate. Given that our study met the primary end point (predefined event rate at 1 year ≤40%, observed event rate 12%), these promising study results could be a rationale for integrating InO induction therapy in future treatment recommendations. Ideally, this novel induction therapy should be evaluated in prospective randomized trials. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Comparable outcomes in patients with B-cell acute lymphoblastic leukemia receiving haploidentical hematopoietic stem cell transplantation: Pretransplant minimal residual disease-negative complete remission following chimeric antigen receptor T-cell therapy versus chemotherapy.

IntroductionChimeric antigen receptor (CAR) T-cell (CAR-T) therapy followed by haploidentical hematopoietic stem cell transplantation (haplo-HSCT) markedly improves the long-term survival of patients with refractory/relapsed (R/R) B-cell acute lymphoblastic leukemia (B-ALL).MethodsWe performed a parallel comparison of transplant outcomes in 168 B-ALL patients undergoing haplo-HSCT after achieving minimal residual disease (MRD)-negative complete remission (CR) from CAR-T therapy (n = 28) or chemotherapy (n = 140) between January 2016 and August 2021. We further divided the chemotherapy group into the first CR group (chemo+CR1, n = 118) and a second or more CR group (chemo+≥CR2, n = 22).ResultsWith a median follow-up period of 31.0 months, the 2-year overall survival (OS), leukemia-free survival (LFS), non-relapse mortality (NRM), and relapse rates in the CAR-T and chemotherapy groups did not differ significantly (OS, 87.9% vs. 71.5 %; LFS, 72.0% vs. 66.8%; NRM, 3.9% vs. 13.7%; relapse, 24.1% vs. 19.4%). Multivariate analysis confirmed that ≥CR2 at transplantation following chemotherapy was an independent risk factor associated with poor OS (hazard ratio (HR) 4.22 [95% CI, 1.34–13.293], p = 0.014) and LFS (HR 2.57 [95% CI, 1.041–6.343], p = 0.041). The probabilities of OS and LFS at 2 years in the CAR-T group were comparable to those in the chemo+CR1 group but significantly higher than those in the chemo+≥CR2 group (OS, 87.9% vs. 37.8%, p = 0.007; LFS, 72.0% vs. 41.7%, p = 0.043). No significant differences in the incidences of NRM were noted among the three groups.ConclusionsOur results demonstrated that patients with R/R B-ALL receiving haplo-HSCT after CAR-T therapy achieved comparable outcomes to patients transplanted post-chemotherapy-based MRD-negative CR1, without increased risk of transplant-related mortality and toxicity.

Characterization of extramedullary disease in B-ALL and response to CAR T-cell therapy

AbstractChimeric antigen receptor (CAR) T cells effectively eradicate medullary B-cell acute lymphoblastic leukemia (B-ALL) and can traffic to and clear central nervous system (CNS) involvement. CAR T-cell activity in non-CNS extramedullary disease (EMD) has not been well characterized. We systematically evaluated CAR T-cell kinetics, associated toxicities, and efficacy in B-ALL non-CNS EMD. We conducted a retrospective review of B-ALL patients with non-CNS EMD who were screened for/enrolled on one of three CAR trials (CD19, CD22, and CD19/22) at our institution. Non-CNS EMD was identified according to histology or radiographic imaging at extramedullary sites excluding the cerebrospinal fluid and CNS parenchyma. Of ∼180 patients with relapsed/refractory B-ALL screened across multiple early-phase trials over an 8-year period, 38 (21.1%) presented with isolated non-CNS EMD (n = 5) or combined medullary/non-CNS EMD (n = 33) on 18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging. A subset receiving CAR T cells (18 infusions) obtained FDG PET/CT scans preinfusion and postinfusion to monitor response. At best response, 72.2% (13 of 18) of patients showed a medullary minimal residual disease–negative complete remission and complete (n = 7) or partial (n = 6) non-CNS EMD response. Non-CNS EMD responses to CAR T cells were delayed (n = 3), and residual non-CNS EMD was substantial; rarely, discrepant outcomes (marrow response without EMD response) were observed (n = 2). Unique CAR-associated toxicities at non-CNS EMD sites were seen in select patients. CAR T cells are active in B-ALL non-CNS EMD. Still, non-CNS EMD response to CAR T cells may be delayed and suboptimal, particularly with multifocal disease. Serial FDG PET/CT scans are necessary for identifying and monitoring non-CNS EMD.

Characteristics and Outcome of Elderly Patients (> 55 Years) with Acute Lymphoblastic Leukemia (ALL)

Introduction: Prognosis of elderly ALL patients is generally considered to be poor. Nonetheless, data on disease characteristics, treatment and outcome of this group of patients is scarce.Methods: Between May 2003 and October 2020, 96 patients (pts) aged > 55 years with B-precursor ALL (91 pts) or T-ALL (5 pts), received first-line induction chemotherapy (84 pts) or were admitted for salvage treatment (8 pts) or allogeneic stem cell transplantation (alloSCT, 4 pts) at the University Hospital Muenster, Germany. 78 patients were diagnosed with a common-ALL (27 pts were BCR/ABL positive) and 13 patients with a pro-B-ALL. Age adapted BFM (Berlin-Frankfurt-Muenster)-like treatment regimens, according to the recommendations of the GMALL (German multicenter ALL study group) for younger (18-55 years, 25 pts) or elderly patients (> 55 years, 68 pts) were used. In general, these protocols consisted of two cycles of induction therapy followed by consolidation, reinduction and consolidation therapy blocks in the 1 st year as well as a consecutive maintenance therapy in the 2 nd year. 3 patients (3%) received no intensive treatment due to poor performance status and comorbidities. Overall survival (OS) and relapse-free survival (RFS) were analyzed using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the log-rank-test and Cox proportional hazards model for RFS and OS, respectively.Results: Median patient age at diagnosis was 66 years (range 55-89 years). 94% of all patients had an ECOG (Eastern Cooperative Oncology Group) status of 0-2 and 92% had a Charlson comorbidity index of 0-2. The median follow-up of all patients was 2.0 years (range 20 days - 16.9 years) and of surviving patients 3.7 years (range 8.8 months - 16.9 years). A complete remission (CR) after induction therapy was documented in 62 of 81 (77%) patients receiving their initial induction therapy at our center. Minimal residual disease (MRD) status was analyzed by quantitative real time PCR in 44 of these patients and 19 patients had an MRD negative CR (43%) after induction therapy. The rate of early death after intensive therapy (death within 100 days after start of treatment) was 6%. The 3 patients not treated with intensive chemotherapy died within 3 months.27 of 93 patients finished the first year of treatment. Subsequent maintenance therapy was administered to 12 patients. The reasons for discontinuation of conventional treatment in the first and second year were relapsed disease (31 pts), alloSCT in 1 st CR (23 pts), toxicity/patients' preference (17 pts) and death in CR under conventional therapy (7 pts). 3 patients have not completed their therapy yet.OS and RFS of the entire cohort at 1 year were 73% (95% CI: 64-82%) and 57% (95% CI: 47-67%) and at 3 years 46% (95% CI: 36-56%) and 32% (95% CI: 22-42%), respectively. The cumulative incidence of relapse at 1 and 3 years was 29% (95% CI: 20-41%) and 56% (95% CI: 45-69%), respectively. OS of those patients receiving an alloSCT (23 pts in 1 st CR, 7 pts in 2 nd CR, 3 pts with active disease, median age at alloSCT 62 years) at 1 and 3 years was 82% (95% CI: 68-95%) and 49% (95% CI: 32-67%), respectively. The cumulative incidence of relapse after alloSCT at 1 and 3 years was 16% (95% CI: 7-35%) and 32% (95% CI: 18-56%), respectively.Regarding the entire patient cohort, older age (> 75 years, 15 pts) was significantly associated with an inferior OS (p < .001). BCR/ABL status, ALL phenotype (T- or B-ALL) or intensity of conventional treatment applied (protocol originally intended for patients ≤ 55 years vs > 55 years) had no significant impact on OS. In multivariate analysis, ECOG status >2 and persisting disease after 1 st consolidation therapy were risk factor associated with inferior OS (p < .05).Conclusion: Intensive treatment is feasible in selected elderly ALL patients (> 55 years). High relapse rates and impaired survival rates underline the need for novel therapeutic strategies. DisclosuresKhandanpour: GSK: Honoraria; Takeda: Honoraria; Janssen: Honoraria; AstraZeneca: Honoraria, Research Funding; Pfizer: Honoraria; Sanofi: Honoraria, Research Funding; BMS/Celgene: Honoraria. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Brüggemann: Incyte: Other: Advisory Board; Amgen: Other: Advisory Board, Travel support, Research Funding, Speakers Bureau; Janssen: Speakers Bureau. Berdel: Philogen S.p.A.: Consultancy, Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees. Stelljes: Celgene/BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Amgen: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau.

Allogeneic-Hematopoietic Stem Cell Transplantation Is Effective and Safe for Relapsed/ Refractory B-ALL Patients Who Cannot Get Remission or MRD Negative after CART Treatment

▪Background: Chimeric antigen receptor T-cell (CART) Therapy has induced high rates of complete remission (CR) in the patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL), but a small portion of them still cannot obtain CR or minimal residual disease (MRD) negative. Salvaged allogeneic hematopoietic stem cell transplantation (allo-HSCT) could be the only curative treatment for this setting. According to previous reports, around 20% to 30% overall survival (OS) has been seen in the patients with r/r B-ALL treated with salvaged allo-HSCT.Aim: In current study, the efficacy and safety of allo-HSCT for the patients with r/r B-ALL who cannot achieve CR or MRD negative after CART therapy were evaluated.Methods: Between January 2018 and June 2021, 23 consecutive patients with r/r B-ALL who did not achieve CR or MRD negative after CART treatment and received allo-HSCT in our hospital were included. The median age was 10 (1-47) years old. The median disease course was 24 (8-89) months. Eight patients were in non-remission (NR) and 15 cases were MRD positive (10 detected by flow cytometry, and 5 detected by RT-PCR). The median blast in bone marrow (BM) in NR series was 39 (0.5-94)% in which two patients were only extramedullary leukemia, and the median flow cytometric MRD level in BM in MRD positive series was 0.11 (0-3)%. One patient had TP53 mutation, one had MLL-AF4 fusion gene and one had both TP53 mutation and MLL-AF4 fusion gene. Nineteen patients (82.6%) received at least two kinds of CART therapies (murinized CD19, humanized CD22, humanized CD19) and 4 patients (17.4%) received one kind of CART therapy (murinized CD19, humanized CD22 or humanized CD19). Three patents underwent second transplantation. Eighteen patients (78.3%) received allo-HSCT from haploidentical donors and 5 patients (21.7%) from unrelated donors (HLA 10/10 matched in 3 and 9/10 matched in 2). Myeloablative conditioning regimens with total body irradiation (fractionated, total 10 Gy) /etoposide (200mg/m 2 x 3) /fludarabine (30mg/m 2 x 5) or cyclophosphamide (1.8g/m 2 x 2) /rabbit anti-T-cell globulin were used. Cyclosporine, mycophenolate mofetil and short-term methotrexate were employed for graft-versus-host disease (GVHD) prophylaxis. Some patients received maintenance regimens with targeted medicine based on their fusion genes or gene mutations up to 2 years post-transplant.Results:All patients achieved durable engraftment. For the patients in NR (n=8) before transplantation, the median follow-up time was 336 (22-803) days. Four of them had been alive free of leukemia and MRD negative, and 4 patients died of relapse. One-year OS and leukemia-free survival (LFS) were 85.7% and 35.7%, respectively. No patient died of transplant-related events. Two patients developed grade III acute GVHD (aGVHD) and 1 patient had extensive chronic GVHD (cGVHD). All of them were resolved with immune-suppressants. CMV and EBV reactivation was detected in 6 and 1 patients, respectively. One patient had severe lung fungal infection and 1 case developed mild hemorrhagic cystitis. For the patients with MRD positive (n=15) before transplantation, the median follow-up time was 359 (42-872) days and one-year OS and LFS were 68.1% and 40.9%, respectively. Seven patients relapsed, three of them achieved MRD negative CR with donor-derived CART therapies, and 3 patients died of relapse. Six patients developed grade III~IV aGVHD and one patient had extensive cGVHD. All of them were resolved except one patient died from grade IV aGVHD. CMV and EBV reactivation was found in 6 and 1 patients, respectively. Three patients had mild hemorrhagic cystitis. No other severe infection occurred.Conclusion: Our results indicate that salvaged allo-HSCT has improved survival remarkably in r/r B-ALL patients who failed not only chemotherapy but also CART therapy.One-year OS and LFS can reach 85.7% and 35.7%, 68.1% and 40.9% in NR and MRD positive cohorts, respectively. Transplant-related mortality is quite low (1/23). The leading cause of death is disease recurrence (7/23). Under our protocol, allo-HSCT is a safe and effective salvaged modality for r/r B-ALL who cannot obtain CR or MRD negative with CART therapy. DisclosuresNo relevant conflicts of interest to declare.

Peripheral leukemia burden at time of apheresis negatively affects the clinical efficacy of CART19 in refractory or relapsed B-ALL

Our previous clinical study achieved complete remission (CR) rates of >90% following chimeric antigen receptor T cells targeting CD19 (CART19) treatment of refractory/relapsed B cell acute lymphoblastic leukemia (r/r B-ALL); however, the influence of the leukemia burden in peripheral blood (PB) blasts remains unclear. Here, we retrospectively analyzed 143 patients treated with CART19 (including 36 patients with PB blasts) to evaluate the effect of peripheral leukemia burden at the time of apheresis. One hundred seventeen patients with high disease burdens achieved 91.5% CR or incomplete count recovery CR and 86.3% minimal residual disease-negative CR, and 26 patients with low disease burdens obtained 96.2% MRD− CR. Collectively, 9 of 36 (25%) patients with PB blasts and 2 of 107 (1.87%) patients without PB blasts did not respond to CART19 therapy. The leukemia burden in PB negatively influenced ex vivo cell characteristics, including the transduction efficiency of CD3+ T cells and their fold expansion, and in vivo cell dynamics, including peak CART19 proportion and absolute count, fold expansion, and persistence duration. Further studies showed that these patients had higher programmed death-1 expression in CART19 products. Our data imply that PB blasts negatively affected CART19 production and the clinical efficacy of CART19 therapy in patients with r/r B-ALL.

CAR T cells with dual targeting of CD19 and CD22 in adult patients with recurrent or refractory B cell malignancies: a phase 1 trial

Despite impressive progress, more than 50% of patients treated with CD19-targeting chimeric antigen receptor T cells (CAR19) experience progressive disease. Ten of 16 patients with large B cell lymphoma (LBCL) with progressive disease after CAR19 treatment had absent or low CD19. Lower surface CD19 density pretreatment was associated with progressive disease. To prevent relapse with CD19− or CD19lo disease, we tested a bispecific CAR targeting CD19 and/or CD22 (CD19-22.BB.z-CAR) in a phase I clinical trial (NCT03233854) of adults with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) and LBCL. The primary end points were manufacturing feasibility and safety with a secondary efficacy end point. Primary end points were met; 97% of products met protocol-specified dose and no dose-limiting toxicities occurred during dose escalation. In B-ALL (n = 17), 100% of patients responded with 88% minimal residual disease-negative complete remission (CR); in LBCL (n = 21), 62% of patients responded with 29% CR. Relapses were CD19−/lo in 50% (5 out of 10) of patients with B-ALL and 29% (4 out of 14) of patients with LBCL but were not associated with CD22−/lo disease. CD19/22-CAR products demonstrated reduced cytokine production when stimulated with CD22 versus CD19. Our results further implicate antigen loss as a major cause of CAR T cell resistance, highlight the challenge of engineering multi-specific CAR T cells with equivalent potency across targets and identify cytokine production as an important quality indicator for CAR T cell potency.

Successful Treatment of TCF3-HLF–positive Childhood B-ALL with Chimeric Antigen Receptor T-Cell Therapy

BackgroundTCF3-HLF positive leukemia represents a rare subtype of B-cell acute lymphoblastic leukemia (B-ALL), characterized by a high treatment failure rate despite intensive treatment and hematopoietic stem cell transplantation (HSCT). Patients and MethodsFour consecutive children with TCF-HLF3–positive B-ALL who were refractory or relapsed with initial chemotherapy were treated with CD19-specific or combined CD19-and CD22-specific chimeric antigen receptor T-cell therapy (19/22 CAR-T) after conditioning regimen with fludarabine and cyclophosphamide. Clinical features, treatment responses, toxicity, and outcomes were analyzed retrospectively. ResultsFour patients received 18.0, 6.0, 5.0, and 7.4 × 106 CAR-T cells per kilogram and developed grade I, III, II, and III cytokine release syndrome, respectively. They all achieved minimal residual disease-negative complete remission (CR). Two of them (patients 1 and 3) underwent haploid HSCT afterward. Patient 1 relapsed after 7.2 months of transplantation and received donor-derived 19/22 CAR-T cell infusion. He had CR2 after he experienced grade II cytokine release syndrome of the second CAR-T and underwent umbilical cord blood transplantation. Unfortunately, this child died of severe lung graft versus host disease 8.4 months after the second transplantation. Patients 2 and 4 experienced reversible neurotoxicity and had a persistent clinical response to CAR-T cells for 13.8 and 6.8 months, respectively, without HSCT. Patient 3 is in continuous CR for 10.6 months until now. ConclusionCAR-T cells can effectively treat relapsed/refractory TCF3-HLF–positive childhood B-ALL with acceptable toxicity, which could be a new treatment option for this subtype compared with chemotherapy or HSCT.

Prognostic significance of lymphocyte patterns in multiple myeloma patients after autologous transplant.

Despite the high efficacy of current induction regimens, most multiple myeloma (MM) patients relapse over time. The link between changes in the immune system and the prognosis of the disease is still not entirely clear. Therefore, we analyzed whether the pattern of bone marrow (BM) lymphocytes during routine BM examination after autologous stem cell transplant (ASCT) is related to disease prognosis or MRD negative complete remission. From 2009 to 2018, 98 MM patients underwent routine BM testing after the first ASCT. Using multi-parametric flow cytometry, twelve BM lymphocyte subtypes were analyzed. In 60% of patients who achieved a complete response (CR), MRD by flow cytometric analysis (sensitivity threshold 10-6) was evaluated. We found an association of relative proportion of BM lymphocyte subtypes with treatment response, progression-free survival (PFS), overall survival (OS), and minimal residual disease (MRD) negativity. Higher relative proportion of memory B cells was associated with inferior median PFS [HR 1.089 (95% CI: 1.023-1.160), p=0.008] and median OS [HR 1.170 (95% CI: 1.074-1.274), p<0.001]. In non-responding patients (minimal response and worse), higher proportion of memory B cells was found when compared to patients achieving CR [3.8% (range 0.5-35.0) vs. 1.0% (range 0.1-12.5); p=0.001]. No significant association of BM lymphocyte subtypes proportion with MRD negative CR was found. Our results show that changes in BM lymphocyte subsets including memory B cells may have prognostic value in MM patients after ASCT.