MRD-negative Complete Remission Research Articles

Case report: Successful combination of CLL1 CAR-T therapy and hematopoietic stem cell transplantation in a 73-year-old patient diagnosed with refractory acute myeloid leukemia

The incidence of Acute myeloid leukemia (AML) increases with advancing age, and the prognosis for elderly patients is significantly poorer compared to younger patients. Although the combination therapy of venetoclax and hypomethylating agents has demonstrated improved prognosis in patients unable to tolerate intensive chemotherapy, there remains a therapeutic blank for those who fail to achieve remission with current treatment regimens. Here, we report the successful clinical utilization of autogenous CLL1 CAR-T therapy combined with hematopoietic stem cell transplantation in a 73-year-old patient diagnosed with refractory AML. The patient achieved morphological complete remission (CR) with incomplete marrow recovery and a slight presence of minimal residual disease (MRD) after receiving CLL1 CAR-T therapy. To further enhance the treatment and promote the recovery of hemopoiesis, we performed bridged allogenic hematopoietic stem cell transplantation (allo-HSCT) 20 days after the infusion of CLL1 CAR-T cells. The patient achieved MRD-negative CR following HSCT treatment. His primary disease maintained a complete remission status during the 11-month follow-up period. The patient encountered grade 2 cytokine release syndrome and grade 4 granulocytopenia subsequent to the infusion of CAR-T cells, while several rounds of infection and graft-versus-host disease were observed following allo-HSCT. Nevertheless, all these concerns were successfully addressed through comprehensive provision of supportive treatments. We have successfully demonstrated a highly effective and safe combination strategy involving CLL1 CAR-T therapy and allo-HSCT, which has exhibited remarkable tolerability and holds great promise even for elderly patients with AML.

In-depth analysis of responders in the phase 3 PhALLCON trial of ponatinib vs imatinib in newly diagnosed Ph+ ALL.

6533 Background: Ponatinib, a third-generation BCR::ABL TKI, has potent activity against all clinically relevant BCR::ABL1 variants, including T315I. PhALLCON (NCT03589326), a phase 3 trial comparing frontline TKIs in adults with Ph+ ALL, met its primary endpoint with a higher rate of minimum residual disease–negative (MRD-neg) complete remission (CR) at end of induction (EOI) with ponatinib vs imatinib (34.4%/16.7%; P=0.002). Here, we report response rates of MRD-neg at any time and PFS by age and BCR::ABL1 variant subgroups. Methods: Adults with newly diagnosed Ph+ ALL were randomized 2:1 to ponatinib (30 mg QD reduced to 15 mg QD upon MRD-neg CR at or after EOI) or imatinib (600 mg QD) plus 20 cycles of reduced-intensity chemotherapy (induction: 3 cycles; consolidation: 6 cycles; maintenance: 11 cycles), followed by single-agent ponatinib or imatinib until disease progression or unacceptable toxicity. Hematopoietic stem cell transplant (HSCT) was per investigator’s discretion. Post hoc analyses compared MRD-neg ( BCR:: ABL1IS ≤0.01%; MR4) at any time and PFS (any-cause death, failure to achieve CR by EOI, relapse from CR, or failure to achieve/loss of MRD-neg) by age (</≥65 y) and BCR:: ABL1 variant (p190/p210). Data cutoff: Aug 12, 2022. Results: In the population of randomized patients (pts) with p190/p210 confirmed by central lab (n=232; 154/78 ponatinib/imatinib; median follow-up 20.1 mo), 68% vs 50% in the ponatinib vs imatinib arms were MRD-neg at any time, with similar benefit of ponatinib across age and variant subgroups (Table). Median PFS was more than twice as long with ponatinib vs imatinib across subgroups (Table). Pts achieving MRD-neg at any time were less likely to have HSCT with ponatinib vs imatinib (32%/56%). Among 107/42 pts without HSCT, exposure was >2-fold longer in the ponatinib vs imatinib arms (median 12.8/5.1 mo) with comparable rates of arterial occlusive (3%/2%) and venous thromboembolic events (11%/12%), and discontinuations due to TEAEs (13%/14%). Conclusions: Ponatinib was superior to imatinib in combination with reduced-intensity chemotherapy for frontline treatment of Ph+ ALL, with higher rates of MRD-neg at any time, substantially longer PFS across age and BCR::ABL1 variant subgroups, and a safety profile comparable to imatinib. Clinical trial information: NCT03589326 . [Table: see text]

Ponatinib vs Imatinib in Frontline Philadelphia Chromosome–Positive Acute Lymphoblastic Leukemia

In newly diagnosed Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL), disease progression due to acquired resistance to first- or second-generation BCR::ABL1 tyrosine kinase inhibitors is common. Ponatinib inhibits BCR::ABL1 and all single-mutation variants, including T315I. To compare frontline ponatinib vs imatinib in adults with newly diagnosed Ph+ ALL. Global registrational, phase 3, open-label trial in adults aged 18 years or older with newly diagnosed Ph+ ALL. From January 2019 to May 2022, eligible patients at 77 sites were randomized 2:1 to ponatinib (30 mg/d) or imatinib (600 mg/d) with reduced-intensity chemotherapy, followed by single-agent ponatinib or imatinib after the cycle 20 phase of the trial. The last date of follow-up for this analysis was August 12, 2022. Patients received ponatinib, 30 mg/d, or imatinib, 600 mg/d, with reduced-intensity chemotherapy, followed by single-agent ponatinib or imatinib after cycle 20. The ponatinib dose was reduced to 15 mg on achievement of minimal residual disease-(MRD) negative complete remission. The primary end point of this interim analysis was MRD-negative complete remission (≤0.01% BCR::ABL1 [MR4] centrally assessed by reverse transcriptase-quantitative polymerase chain reaction), with complete remission maintained for at least 4 weeks at the end of cycle 3. The key secondary end point was event-free survival. Of 245 patients randomized (median age, 54 years; 133 [54.3%] female), 232 (ponatinib, n = 154; imatinib, n = 78) who had p190 or p210 dominant isoforms verified by the central laboratory were analyzed for the primary end point. The MRD-negative complete remission rate (primary end point) was significantly higher with ponatinib (34.4% [53/154]) vs imatinib (16.7% [13/78]) (risk difference, 0.18 [95% CI, 0.06-0.29]; P = .002). At the data cutoff, event-free survival had not met the prespecified number of events. Median event-free survival was not reached in the ponatinib group and was 29 months in the imatinib group. The most common adverse events were similar between treatment groups. Arterial occlusive events were infrequent and comparable between groups (ponatinib, 2.5%; imatinib, 1.2%). Ponatinib demonstrated a superior rate of MRD-negative complete remission at the end of induction vs imatinib when combined with reduced-intensity chemotherapy in adults with newly diagnosed Ph+ ALL. The safety profile of ponatinib was comparable with imatinib. ClinicalTrials.gov Identifier: NCT03589326.

Seven-year outcomes of venetoclax-ibrutinib therapy in mantle cell lymphoma: durable responses and treatment-free remissions

AbstractIn the phase 2 clinical trial (AIM) of venetoclax-ibrutinib, 24 patients with mantle cell lymphoma (MCL; 23 with relapsed/refractory [R/R] disease) received ibrutinib 560 mg and venetoclax 400 mg both once daily. High complete remission (CR) and measurable residual disease negative (MRD-negative) CR rates were previously reported. With median survivor follow-up now exceeding 7 years, we report long-term results. Treatment was initially continuous, with elective treatment interruption (ETI) allowed after protocol amendment for patients in MRD-negative CR. For R/R MCL, the estimated 7-year progression-free survival was 30% (95% confidence interval [CI], 14-49; median, 28 months; 95% CI, 13-82) and overall survival was 43% (95% CI, 23-62; median, 32 months; 95% CI, 15 to not evaluable). Eight patients in MRD-negative CR entered ETI for a median of 58 months (95% CI, 37-79), with 4 experiencing disease recurrence. Two of 3 reattained CR on re-treatment. Time-to-treatment failure, which excluded progression in ETI for those reattaining response, was 39% overall and 68% at 7 years for responders. Beyond 56 weeks, grade ≥3 and serious adverse events were uncommon. Newly emergent or increasing cardiovascular toxicity were not observed beyond 56 weeks. We demonstrate long-term durable responses and acceptable toxicity profile of venetoclax-ibrutinib in R/R MCL and show feasibility of treatment interruption while maintaining ongoing disease control. This trial was registered at www.ClinicalTrials.gov as #NCT02471391.

CD19-Specific CAR-T Cell Treatment of 115 Children and Young Adults with Acute B Lymphoblastic Leukemia: Long-term Follow-up.

Chemotherapy has been the primary treatment for patients with B-cell acute lymphoblastic leukemia (B-ALL). However, there are still patients who are not sensitive to chemotherapy, including those with refractory/relapse (R/R) disease and those experiencing minimal residual disease (MRD) re-emergence. Chimeric antigen receptor-T lymphocytes (CAR-T) therapy may provide a new treatment option for these patients. Our institution conducted a single-arm prospective clinical trial (ChiCTR-OPN-17013507) using CAR-T-19 to treat R/R B-ALL and MRD re-emergent patients. One hundred and fifteen patients, aged 1-25 years (median age, 8 years), were enrolled, including 67 R/R and 48 MRD re-emergent CD19-positive B-ALL patients. All patients achieved morphologic complete remission (CR), and within 1 month after infusion, 111 out of 115 (96.5%) patients achieved MRD-negative CR. With a median follow-up time of 48.4 months, the estimated 4-year leukemia-free survival (LFS) rate and overall survival (OS) rate were 68.7%±4.5% and 70.7%±4.3%, respectively. There were no significant differences in long-term efficacy observed among patients with different disease statuses before infusion (4-year OS: MRD re-emergence vs. R/R B-ALL, 70.6%±6.6% vs. 66.5%±6.1%, p=0.755; 4-year LFS: MRD re-emergence vs. R/R B-ALL, 67.3%±7.0% vs. 63.8%±6.2%, p=0.704). R/R B-ALL patients bridging to transplantation after CAR-T treatment had a superior OS and LFS compared to those who did not. However, for MRD re-emergent patients, there was no significant difference in OS and LFS, regardless of whether they underwent hematopoietic stem cell transplantation or not. CD19 CAR-T therapy effectively and safely cures both R/R B-ALL and MRD re-emergent patients.

Real World Data on Treatment of Acute Myeloid Leukemia (AML) in a Private Healthcare Institution in Brazil, a Low-Middle Income Country - Importance of Allogeneic Hematopoietic Stem Cell Transplantation (HSCT)

Introduction: Treatment of patients with AML has evolved in the past decade, with development of novel drugs and increased knowledge about the genetic basis of disease. However, results of therapy in AML in LMICs have lagged those seen in more developed countries. A recently published paper highlighted the worse outcome of pts with AML treated in two public healthcare hospitals in Brazil compared with pts treated at an academic center at Oxford, UK, with lower overall survival (OS), lower rates of HSCT and a longer time to HSCT. 1 We hypothesized, however, that better outcomes could be seen in private healthcare institutions in Brazil with a higher rate of HSCT in first remission. Methods: We reviewed medical records of 122 patients with a diagnosis AML treated at Hospital Israelita Albert Einstein in São Paulo, Brazil, from 2010 until 2023. OS was defined as time from diagnosis until death from any cause and estimated by the Kaplan-Meier method. Risk was evaluated by the ELN 2022 risk classification. Results: A total of 122 consecutive patients were included. Median age was 63 years (range 24-91 years), and 45% were female. Per the ELN 2022 risk classification, 17% of patients were low risk, 33% were intermediate risk and 50% were considered high risk cases. Intensive chemotherapy was used in 62.5% of cases, while low-intensity regimens were employed in 37.5% of cases, including venetoclax in 21.4% of patients. After a median follow-up of 36 months, median OS of the whole cohort is 25.2 months (95% CI 19.2-83.8 months), and 3-years OS is 44% (95% CI 34-55%). As expected, patients in the high 2022 ELN risk category had lower 3-years OS probability (15.6% vs. 47.3%/91.6% for intermediate- and low-risk, respectively). Eighty-two patients (67.2% of the cohort) underwent HSCT, and 59% were in MRD-negative complete remission (CR) prior to HSCT. We next analyzed outcomes in patients younger than 60 years of age who received intensive chemotherapy, the subset of patients analyzed by Silveira et al. 1 Results are summarized in Table 1 and figure 1. The outcomes of our patients compare favorable to what has been reported here in Brazil and, like the data from the UK center, has a high rate of HSCT with a low time to transplant. Conclusion: Our results demonstrate that it is feasible to obtain favorable outcomes in patients with AML in a LMIC with a high rate of HSCT in first CR. It is also important to mention that our results also reflect the reality of a private healthcare institution in Brazil. However, even after considering this, our results carry an important message. There is limited availability of clinical trials and novel medications for AML in LMICs compared to the developed world, and options in the salvage setting are usually limited to intensive chemotherapeutic regimes. Allogeneic HSCT is a technique that is readily available in most countries and has the potential to cure AML, particularly when employed in first CR. We believe that physicians and institutions treating patients with AML in a LMIC should primarily focus on strategies that improve access to HSCT in first CR for these patients.

CD7 CAR-T Therapy Followed By a Second Transplant for T-Cell Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma Patients Who Relapsed after a Prior Transplant

Background The therapeutic options for patients with T-cell acute lymphoblastic leukemia or lymphoblastic lymphoma (T-ALL/LBL) who relapse after hematopoietic stem cell transplantation (HSCT) are currently restricted. CD7-targeted chimeric antigen receptor (CAR) T-cell therapy provides a promising avenue towards remission, yet the long-term prognosis for these patients still needs to be improved. The advantages of progressing to a second transplant post-CAR-T treatment remain uncertain due to limited data. In this study, we analyzed the clinical characteristics and transplantation outcomes of 16 T-ALL/LBL patients who, having relapsed after their initial transplantation, achieved complete remission (CR) in bone marrow (BM) and CR/partial remission (PR) in extramedullary lesions via CD7 CAR-T therapy and then opted for a second allogeneic HSCT (allo-HSCT) at our center. Our aim is to explore strategies to enhance the survival rate of these patients. Methods From January 2021 to January 2023, we analyzed T-ALL/LBL patients who underwent second transplantation at Hebei Yanda Lu Daopei Hospital. The patients included in this study met the following criteria: they had relapsed following their first HSCT and had subsequently undergone CD7 CAR-T therapy prior to the second transplantation. The follow-up cut-off date was till June 1, 2023. The median follow-up duration after the second transplantation was 178 days, ranging from 9 to 500 days. Results A total of 16 patients including 13 with T-ALL and 3 with T-LBL were enrolled. There were 14 males and 2 females. The donor of first transplantation was autologous(n=3), sibling identical(n=2), unrelated donor(n=2), or haplo-identical (n=9). After the first transplantation, 8 patients relapsed in bone marrow (BM) and 8 relapsed both in BM and extramedullary sites. Of these, 13 patients received autologous CD7 CAR-T, one patient received donor-derived CD7 CAR-T, and one patient was treated with universal CAR-T cells. After the CD7 CAR-T therapy, all 16 patients (100%) achieved minimal residual disease (MRD)-negative CR in BM, and 6 out of 8 patients (75%) achieved CR in extramedullary lesions. Only two patients exhibited PR in the extramedullary lesions. The median age at the time of the second transplantation was 28 years (range 14-42 years). The median time from diagnosis to the second transplantation was 683 days (range 385-2672 days). The median interval between the first and second transplantation was 438 days (range 229-2540 days), and the median interval from CD7 CAR-T infusion to the second transplantation was 72 days (range 31-92 days). For the second transplantation, 13 cases had haplo-identical donors and 3 cases had unrelated donors. The conditioning regimens utilized were either total body irradiation (TBI)-based (n=9), busulfan-based (n=6), or melphalan-based (n=1). Following the 2 nd transplant, the 1-year overall survival(OS) and leukemia-free survival(LFS) were 58.5% (95% CI, 28.9-85.0%) and 51.4% (95% CI, 22.4-79.9%), respectively(Figure 1). The 1-year relapse incidence (RI) and non-relapse mortality (NRM) were 15.9% (95% CI, 4.4-57.8%) and 31.5% (95% CI, 13.2-74.9%), respectively. The cumulative incidence of CMV and EBV viremia at day 100 were 75.0% (95% CI, 56.5-99.5%) and 19.8% (95% CI, 7.2-54.6%), respectively. The cumulative incidence of all grades acute graft-versus-host disease (aGVHD) and 3-4 grade aGVHD at day 100 were 56.3% (95%CI, 36.5-86.7%) and 25% (95%CI, 10.7-58.4%), respectively. One-year chronic GVHD(cGVHD) was observed in 25.1% of the cases (95%CI, 9.3-67.4%), while moderate to severe cGVHD was not found in any patient. Following the 2 nd transplant, a total of 6 patients died, including 3 from infection, 2 from relapse and 1 from intracranial hemorrhage. Conclusions Our initial findings suggest that even in refractory/relapsed T-ALL/LBL patients who have experienced relapse following previous HSCT, MRD-negative complete remission can potentially be achieved utilizing CD7 CAR-T cell therapy. The subsequent implementation of a second allo-HSCT appears feasible. Combining CAR-T therapy with a follow-up second HSCT presents a strategy for these heavily pre-treated patients, offering promising prospects for survival. However, further evaluation of this treatment approach is required, necessitating long-term monitoring and a larger patient cohort.

Mini-Hyper-CVD Plus Venetoclax for Treatment of Older Adults with Newly Diagnosed Ph-Negative B-ALL or T-ALL

Introduction Treatment of Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) in older patients (pts) is challenging due to poor tolerance of conventional chemotherapy and chemo-resistant disease. Pre-clinical work demonstrates that lymphoblasts are BCL2-dependent and sensitive to the BCL2 inhibitor venetoclax (VEN). We hypothesized that VEN plus dose-reduced hyper-CVD (cyclophosphamide, vincristine, dexamethasone) chemotherapy would be well tolerated and effective in older pts. We previously reported the safety and tolerability of VEN plus hyper-CVD in newly diagnosed and relapsed/refractory (R/R) pts (Jain ASH 2019), with a maximum tolerated dose of VEN 600 mg daily on days 1-21 per 28-day cycle. Preliminarily efficacy was promising in newly diagnosed pts, which prompted study extension to phase (P) 2, enrolling newly diagnosed older pts with Ph-negative (neg) B-ALL and T-ALL. Methods Pts with Ph-neg B-ALL or T-ALL were enrolled in a multi-center Phase Ib/II study (NCT03319901). In P1, both R/R pts and newly diagnosed pts ≥ 60 years (yrs) were enrolled. In P2, only newly diagnosed pts ≥ 55 yrs old or ≥ 50 yrs old with BMI ≥ 35 kg/m2 were enrolled. Pts began with VEN ramp-up (P1 over 7d; P2 over 3d) to target dose (P1: dose level [DL]1 400 mg/d; DL2 600 mg/d; P2 400 mg/d), Figure 1. Hyper-CVD, including central nervous system (CNS) prophylaxis with intrathecal chemotherapy, was then given with VEN per DL for 21/28 days per cycle, for up to 8 cycles. Following completion of hyper-CVD courses, pts received VEN plus POMP maintenance for up to 2 yrs. Pts were recommended to receive fewer than 8 cycles of hyper-CVD in the setting of toxicity or to proceed to allogeneic hematopoietic stem cell transplant (HSCT) per physician discretion. This report updates follow-up of the newly diagnosed pts enrolled in P1 and the P2 cohort. Complete remission (CR) was defined as <5% marrow blasts, no evidence of extramedullary or CNS leukemia, ANC >1.0 K/uL and platelets >100 K/uL. Measurable residual disease (MRD) was evaluated by multicolor flow cytometry (MFC) and negative defined as <0.01%. Survival outcomes are presented via Kaplan Meier. Results In total, 30 newly diagnosed pts [P1 11 (DL1=3; DL2=8); P2 18] were treated with a median age of 68 yrs (range, 57-81 yrs, n=12 [40%] ≥70 yrs); n=15 (50%) women, n=4 (13%) Hispanic, and n=1 (3%) Black. Twenty-three (77%) pts had B-ALL and 7 (23%) pts had T-ALL (6/7 early T-cell precursor). Two (6%) pts had central nervous system (CNS) involvement at diagnosis (1-CNS3, 1-CNS2). High risk genetics were present in 56% (13/23) of B-ALL pts: TP53 (n=9 associated with complex [n=3] or hypodiploid [n=5] karyotype), KMT2A (n=1), IKZF1 abnormality (n=2), and Ph-like (n=1). Eight B-ALL pts had received prior chemotherapy for multiple myeloma (n=6; n=4 auto HSCT, n=5 lenalidomide), diffuse large B-cell lymphoma (n=1, RCHOP), and breast cancer (n=1, docetaxel, carboplatin, trastuzumab). The median number of hyper-CVD cycles received was 4 (range 1-8) among the 27 pts who have completed the hyper-CVD phase of treatment (3 pts are currently receiving consolidation). Mortality within 30 days was 3% (n=1). One patient died in CR due to sepsis during cycle 4. Venetoclax did not impair count recovery: median time from C1 to C2 was 34 days (range 27-47). Dose adjustments of VEN occurred in 4 pts (15%). An MRD-neg CR was achieved in 25/30 (83%) pts. The median cycles to achieve both CR and MRD negativity by MFC was one (range: CR 1-2 cycles; MRD negativity 1-4 cycles). Remaining pts had refractory disease (n=4, 13%), or were not assessed (n=1, 3%) due to early death. Of the 25 pts who achieved CR, 11/25 (44%) received allogeneic HSCT in CR1 after a median of 200 days (range 138 to 347). With a median follow-up of 16.4 months, the estimated 12- and 24-month OS are 82.1% (95% CI 66, 98) and 74.6% (95% CI 54, 95), Figure 2; and RFS are 82.9% (95% CI 65, 100.0) and 67.8% (95% CI 44, 92), respectively. At data cut-off, 22 pts (73%) are alive. Death events (n=8, 27%) were due to early mortality (n=1, related to both ALL and infection), post HSCT complications (n=3), refractory ALL (n=1), relapsed ALL (n=1), sepsis in CR (n=1), and complications of cardiac surgery in CR (n=1). Conclusion In this ongoing study, the addition of VEN to hyper-CVD in newly diagnosed ALL was well tolerated with encouraging responses. A future amendment will incorporate blinatumomab consolidation for pts with B-ALL.

A Single Centre Cohort Study of Monitoring B Cell Populations in the Bone Marrow and Peripheral Blood Post Tisagenlecleucel Therapy of Relapsed/Refractory Acute Lymphoblastic Leukaemia

Introduction: CD19-targeting CAR T cell therapy has transformed the landscape of relapsed/refractory (r/r) B cell acute lymphoblastic leukaemia (ALL). Outcome data from multiple study and real-world cohorts suggest early loss of B cell aplasia (i.e. within 6 months of infusion) is associated with a high relapse risk, but the optimal therapeutic strategy is not clear, with consideration given to e.g. consolidative hematopoietic stem cell transplant (HSCT) in order to mitigate relapse risk. CAR T cell persistence is inferred from ongoing B cell depletion assessed by enumeration of normal CD19-expressing B-cells or B-cell precursors in the peripheral blood (PB) and bone marrow (BM)respectively. However, internationally-agreed consensus definitions for B cell aplasia in the context of CAR T cell therapy are lacking. Whilst CAR T cells can be detected by flow cytometric and PCR-based assays, these are complex to validate robustly because of differing sensitivity and specificity, harmonisation efforts are underway. We systematically investigated recovery of healthy B cells in the BM and PB in patients undergoing tisagenlecleucel therapy for B cell ALL at our centre and mapped these events to MRD emergence, relapse and further therapy provision. Methods: Patients deemed eligible for this study were all those treated with tisagenlecleucel for r/r B-cell ALL at our centre and who entered an MRD negative complete remission with or without haematological recovery (CR/CRi). B cell aplasia was defined as having less than 0.01 CD19+ B cells x10^9/L in the peripheral blood and less than 1x10^-3 CD19+ BM B cell precursors enumerated against CD45+ BM WBC events after red cell lysis. B cell recovery in either PB or BM was defined by detection of greater than or equal to 0.01 CD19+ B cells x10^9/L in the peripheral blood or 1x10^-3 CD19+ BM B cell precursors respectively Patients were routinely monitored for B cell populations in PB monthly for the first 12 months. BM +/- CSF was assessed for disease/measurable residual disease (MRD) by flow cytometry and immunoreceptor gene rearrangements by qPCR as well as normal B cell regeneration at months 1, 3, 6, 12 post CAR T cell infusion. Patients were followed for recovery of B cells in the PB or BM until one of the following events: emergence of MRD, frank relapse or death in remission. Therapy (HSCT or maintenance chemotherapy) instigated for B cell recovery in patients remaining in an MRD negative CR/CRi was documented. Results: 46 patients meeting the eligibility criteria for this study were treated with tisagenlecleucel between January 2019 and May 2023. Patient characteristics are given in Table 1. Events for 28 patients with detection of normal B cells in the BM or PB at any time point post CAR T cell infusion are shown in the swimmer plot in Figure 1. Of 46 treated patients, 2 had not achieved B cell aplasia at 1 month post infusion. Of the remaining 44 patients, 26 subsequently (59%) had B cell recovery suggesting loss of CAR T cell persistence; 18 (41%) have B cell aplasia. Of 26 patients with B cell recovery, 16 (62%) recovered B cells in BM before PB with a median of 3 months (range 0-22 mo) between these. 8 (31%) patients had recovery of B cells in BM and PB contemporaneously and 1 (8%) had recovery detected in PB only at 22 mo post infusion Of 16 patients with first detection of BM B cells, 8 (50%) went on to have with HSCT or maintenance chemotherapy (for those with a contraindication to HSCT) whilst in an MRD neg remission, 1 had a repeat CART infusion, 2 had frank relapse, 1 developed secondary AML. 7 of the 9 treated patients are alive in MRD neg remission Of the 8 patients with recovery in both PB and BM compartments, 2 went on to have HSCT, 4 maintenance chemotherapy and 2 had second infusion. 4 remain alive and in MRD neg remission Of 46 patients achieving B cell aplasia, 1 patient had a frank CD19+ relapse at 648 days without prior detection of normal B cell recovery. 3 other patients without B cell recovery were noted to have emergence of MRD at 84, 93, and 206 days (CD19+, CD19- and CD19 unknown respectively) Conclusions: Following BM B cell populations can provide a window of opportunity to intervene before MRD emergence or relapse for patients with early B cell recovery suggesting loss of CAR T cell persistence.

Safety and Efficacy of CD22/ CD19 CAR-T and Auto-HSCT “Sandwich” Strategy As Consolidation Therapy for Ph Negative B Cell Acute Lymphoblastic Leukemia

Introduction: Chimeric antigen receptor T-cell (CAR-T) therapy has a high relapse rate in B cell acute lymphoblastic leukemia (B-ALL). CAR T-cells target multi-antigen or CAR-T combined with other strategy may reduce the relapse post CAR-T. The main purpose of this study is to observe the safety and efficacy of CD22/CD19 CAR-T and Auto-HSCT “Sandwich” strategy in Ph negative (Ph -) B-ALL patients. Methods: A total of 19 newly diagnosed Ph - B-ALL patients were enrolled in this study (NCT05470777). These patients received induction and consolidation chemotherapy according to standard protocols. Autologous lymphocytes were collected at week 4 after induction chemotherapy. Afterwards, autologous CAR T-cells targeting CD22 and CD19 (CAR-T 1, co-stimulatory molecule was 4-1BB and infusion dose was 5×10 6/kg, respectively) were sequential infused after lymphodepletion chemotherapy with fludarabine and cytophosphamide. Autologous stem cells mobilization and collection were performed at 6-8 weeks after CAR T-cells infusion. After conditioned with modified BuCy regimen, autologous stem cells transplantation (auto-HSCT) was conducted. Sequential infusion of CD22 and CD19 CAR-T cells was performed on the second day after transplantation (CAR-T 2, co-stimulatory molecules and dose as CAR-T 1). No maintenance therapy was performed after auto-HSCT. Measurable detectable disease (MRD) was monitored by flow cytometry and IGHV leader-based next generation sequencing. Persistence of CAR T-cells were detected using real time quantitative RT-PCR (qPCR). Results: Three of the enrolled patients were Ph-like B-ALL. 10 (52.6%) patients had poor risk factors according to NCCN guidelines. Grade 1-2 cytokine release syndrome (CRS) occurred in four (21.1%) and seven (36.8%) patients after CAR-T 1 and CAR-T 2, respectively. No grade 3-4 CRS and immune effector cell associated neurotoxicity syndrome (ICANS) occurred. After CAR-T therapy, all patients achieved MRDnegative complete remission (MRD -CR). Until the last follow-up on July 1 st, 2023, the median follow-up was 16 months (range, 7 - 32 months). 84.2% of enrolled patients remain MRD -CR. Duration of continuous MRD -CR was detected in 2 patients for more than 2 years and in 9 patients for more than 1 year. The median overall survival (OS) and leukemia-free survival (LFS) in all 19 patients are not reached. Three (3/19, 15.8%) patients experienced antigen-positive relapse. One Ph-like B-ALL patient relapsed at 10 months after auto-HSCT and underwent allogeneic HSCT. Two patients with Ph - B-ALL relapsed at 5 and 6 months after auto-HSCT and were treated with blinatumomab. All of them achieved MRD -CR again after treatment. All patients are alive and CAR-T cells are detectable in all patients at the last follow-up (range, 5-28 months). Conclusions: Our preliminary study demonstrated that CD22/CD19 CAR-T and Auto-HSCT “Sandwich” strategy as a consolidation strategy showed favorable safety and efficacy in Ph - B-ALL. CD22/CD19 CAR-T resulted in deeper remission before transplantation. The new strategy may benefit patients from LFS and OS.

Gene-Edited Universal CD7 Chimeric Antigen Receptor T Cells for Pediatric T-Cell Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma

Background: T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) are highly aggressive T-lineage malignancies characterized by an infiltration of immature T cells in the bone marrow (BM) and peripheral blood (PB) or extramedullary organ involvements. Effective treatments were elusive, and the long-term survival of patients with refractory/relapsed (R/R) T-ALL/LBL remains poor despite allogeneic hematopoietic stem cell transplantation (allo-HSCT). CAR-T therapies for T-cell malignancies remain underdeveloped due to the shared antigenicity between normal and malignant T cells. CD7 is highly expressed on the surface of T-ALL/LBL T cells and is considered a viable CAR-T therapeutic target. However, CD7-targeting immunotherapies may be compromised by T-cell fratricide and extermination. And one of the biggest challenges with autologous CAR-T cell therapy is to isolate a sufficient number of healthy T cells from malignant T cells. Thus, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR9-associated protein 9 (Cas9)-mediated gene ablation has been used to produce universal CD7-targeted CAR T cells (UCD7-CAR) from suitable healthy donors that no longer express CD7 and TCR. In vitro killing tests, animal tests, and phase 1 clinical trials have preliminarily verified the efficacy and safety of universal CD7 CAR-T cells. Here we investigated the safety and efficacy of the universal CD7 CAR-T therapy in phase 2 clinical trial(NCT05454241) for pediatric R/R T-ALL/LBL patients. Aims: To investigate the efficacy and safety of the universal CD7 CAR-T therapy for pediatric R/R T-ALL/LBL patients. Methods: Patients over three years of age whose disease failed ≥ 2 lines of therapies and had ≥ 80% CD7 expression were eligible, including those who relapsed within 12 months after complete response or relapsed more than 12 months after complete response and failed to achieve remission induced by one or more courses of standard treatment; and patients with recurrence after hematopoietic stem cell transplantation. A lymphodepletion regimen was administered to all patients using fludarabine (30 mg/m2 per day) and cyclophosphamide (500 mg/m2 per day) for three consecutive days (day -5 to day -3) before CAR-T infusion. Patients received one single infusion of UCD7-CAR T cells at a median dose of 2.0×10^6/kg. Consolidative allo-HSCT after remission was allowed after day 28 after UCD7-CART infusion at the discretion of the physician and patient preference. All surviving patients were followed until July 15, 2023; the median follow-up was 109 days (54 to 117 days). Results: Five eligible children, 1 with r/r T-LBL and 4 with r/r T-ALL, were enrolled between December 2022 and April 2023 (Table 1). The median age of the patients was 5 (4-11) years. One girl(Patient 04) had a history of allo-HSCT before enrollment. Patients were heavily pretreated with a median of 3(2-6) lines of therapies. At registration, the median proportion of blasts in 4 T-ALL patients was 47.275% (6.0%-56.0%) in BM by FCM along with CNS(n=2) or testis(n=1) involvement. In contrast, 1 T-LBL patient(patient 02) did not have BM blasts but with bulky mediastinal masses ≥7 cm in diameter. All five patients had no or mild CRS (no CRS, n=1; grade 1, n=3; grade 2, n=1), and most(n=4) did not show symptoms of neurotoxicity. Patient 04, who received a prior allo-HSCT approximately seven months before CAR-T therapy, had a Herpes virus 6 (HHV-6B) encephalitis on day 17 after CAR-T infusion, but no GVHD was observed. On day 28, 4 of 5 (80.0%) patients who had BM involvement achieved MRD-negative complete remission (CR; n=2) or CR with incomplete hematologic recovery (CRi; n=2); but patient 02 with bulky mediastinal masses did not have an obvious response. Until the cutoff date, patient 04 still kept a sustained MRD negative CR; patient 05 relapsed again 49 days after CAR-T infusion, and the other three patients received a subsequent allo-UCBT with a CR state. All the children are still alive. Conclusion:UCD7-CAR T therapy is a safe and highly effective pediatric T-ALL/LBL treatment. More patients and longer follow-ups are needed for validation.

Impact of Treatment with Inotuzumab Ozogamicin before or after Chimeric Antigen Receptor T-Cell Therapy in Children with Relapsed/Refractory Acute Lymphoblastic Leukemia

Background: Inotuzumab (InO), a monoclonal antibody targeting CD22 conjugated to calicheamicin, is widely used for relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) with good salvage rates (O'Brien, JCO 2022, Bhojwani, Leukemia 2019). Feasibility data on its use as a bridge to Chimeric Antigen Receptor T-cell therapy (CART) or as salvage therapy post CART is limited. Concern has been raised that InO given prior to leukapheresis might impact the quality of T-cell collection and, when used for bridging therapy prior to CART, could result in insufficient B-cell antigen load at the time of CART infusion, therefore reducing efficacy. Methods: Data of patients who received InO monotherapy on Children's Oncology Group study AALL1621 Cohort 1 and who received any form of CART prior to study enrollment or within 1 year of coming off protocol therapy, irrespective of other anti-leukemic treatments, were collected retrospectively using a standardized Case Report Form. Results: Forty-eight patients received InO on AALL1621; 3-year overall survival (OS) rate was 35.4±6.9%. Thirteen received InO prior to CART and thirteen received InO post CART including 1 patient who received CD19 CART prior to InO and CD22 CART post InO (Table 1). InO prior to CART (11 CD19 CART, 1 CD22 CART, 1 unknown): Seven patients went directly to CART post InO, 5 received intervening chemotherapy, and 1 had an intervening transplant with relapse post. Nine patients received tisagenlecleucel and 3 received an investigational CART. Patients were infused CART 1-150 days (median 45 days) after coming off protocol therapy. At CART infusion, 10 patients had detectable ALL, only 2 had no CD19 expressing cells at infusion (ALL or normal B-cells) and 1 unknown. At post CART bone marrow evaluation on day 28, 7/12 (58.3%) were in a minimal residual disease (MRD) negative (<0.01%) remission, 1 had MRD=0.021%, 1 had unknown response. Three had residual disease including the single patient who received CD22-targeted CART. Four MRD negative patients who received CART post-InO are alive without relapse at a median of 3.8 years post CART and 1 is alive with a subsequent relapse. At 3 years post CART infusion OS is 53.9±13.8%. T-cells were collected immediately following 3-9 doses of InO in 8/13 (61.5%) patients (1-6 months from date of enrollment on the study), 2 were collected prior to InO and three had unknown collection dates. All had a CART product manufactured successfully. Post CART 7/13 patients did not develop thrombocytopenia (< 50,000/uL); 5 who developed thrombocytopenia had measurable ALL at day 28 post CART or soon after. One other patient went to planned transplant post CART and remained with low platelets and ANC. Almost all patients (11/13) had ANC < 500/uL post CART, of whom 3 did not recover including two with persistent ALL. InO Post CART (11 CD19-targeted CART, 2 CD22-targeted CART): Of the 13 patients who received InO post CART therapy, 7/13 (53.8%) achieved an MRD-negative complete remission (CR) to CART but then developed detectable disease 2-36 months post CART. Five did not have a CR post-CART, 4 of whom enrolled on AALL1621 within one month; 1 received intervening chemotherapy. One had an unknown response. On univariate analysis CR rate with InO therapy was no different for those who received CART prior to InO than those who did not. As well, risk of a dose limiting toxicity event (DLT) or developing sinusoidal obstructive syndrome (SOS) during InO therapy or during subsequent transplant after InO was not different in patients with CART exposure prior to AALL1621 enrollment. Conclusion: The ability to collect and manufacture CART cells was feasible within weeks of receiving InO. Response to CART post InO was lower than retrospective cohorts (Ceolin, Leukemia 2022) but 3-year OS post CART was consistent with published CD19-targeted CART trials at 53.9% (Maude, NEJM 2018; Pasquini, Blood Adv 2020). InO did not appear to impact durability of remission in those who attained an MRD negative remission with CART. Given most patients had a CD19 target due to disease presence at the time of CART infusion, differential response to CART based upon antigen could not be analyzed. Prior InO exposure did not appear to worsen cytopenias post CART when compared to published CART trials and was associated with a comparable 3-year OS. As well, CART exposure prior to InO did not appear to effect response or increase the risk of DLT or SOS during subsequent InO therapy.

A Phase I Study of Venetoclax in Combination with Inotuzumab Ozogamicin for Relapsed or Refractory ALL in Adults

Introduction Adults with acute lymphoblastic leukemia (ALL), especially those who are older and/or have unfavorable disease biology frequently relapse. Inotuzumab ozogamicin (INO), an anti-CD22 monoclonal antibody covalently linked to calicheamicin, is approved for treatment of relapsed or refractory (R/R) CD22+ ALL. Although INO induces measurable residual disease negative (MRD-neg) complete remission (CR) in >75% of patients (pts), the duration of response (DOR) is limited (<6 months). Pre-clinical work demonstrates that malignant lymphoblasts are BCL2-dependent (Del Gaizo Moore Blood 2008). Initial results of the BCL2 inhibitor venetoclax (VEN) combination therapies for ALL are promising (Jain ASH 2019, Pullarkat Cancer Discov 2021). Due to distinct mechanisms of activity, non-overlapping toxicity, and possible synergy (Kirchhoff Blood 2021), we hypothesized that INO and VEN can be safely and effectively combined. Study Design and Eligibility This is an investigator-sponsored phase I study (NCT05016947) with a 3+3 dose escalation design. The primary objective is to determine the maximum tolerated dose (MTD) of VEN plus INO at the FDA-approved doses in adults with R/R CD22+ ALL. Secondary objectives assess efficacy (hematologic response, MRD by multi-parametric flow cytometry [MFC] threshold <0.01%, and DOR). A 14 pt expansion cohort is planned. Dose-limiting toxicity (DLT) is defined as treatment-related CTCAE v5 non-heme toxicity grade 3+, sinusoidal obstructive syndrome (SOS) any grade, or liver toxicity during Induction (Ind) Cycle (C) 1 and/or failure of hematologic recovery (ANC ≥500, Plts ≥25 K/mL) by day 42 of Ind C1 in responding pts. Eligibility: ≥18 years (yrs); ALL (≥5% blasts) or LBL (marrow involvement not required); CD22 expression on ≥20% of blasts; R/R to one or more cycles of CC or in the case of Philadelphia-chromosome (Ph)-positive ALL, failed by two or more TKIs, or refractory to/ineligible for ponatinib; ≥60 days from bone marrow transplant (BMT), and off immune suppression ≥2 weeks; adequate liver and kidney function; no history of liver disease including SOS; blast count ≤25 K/mL prior to treatment; no symptomatic central nervous system (CNS) disease. Pts with prior INO or VEN treatment for R/R ALL are excluded. Regimen Pts are treated with a VEN Ramp-Up over 3 days (DL1: 100/200/200; DL2: 100/200/400) followed by Induction C1: IV INO days 1, 8, 15 (0.8/0.5/0.5 mg/m2) and VEN daily per DL days 1-21. DEX 10 mg/m2 IV/PO is administered during Ramp-Up and Ind C1 days 1-4 (7 days total). Pts with >5% blasts after C1 receive Ind C2 without DEX. Pts with <5% blasts after Ind (1 or 2 cycles) continue with up to four 28-day consolidation cycles (INO 0.5 mg/m2 days 1, 8, 15 plus VEN per DL days 1-21). Pts receive CNS prophylaxis with intrathecal chemotherapy. Results The 2-level dose-escalation phase has been completed; we enrolled 9 pts (5 female/4 male) with Ph-negative (n=7) or Ph-positive (n=2) ALL. The median age was 45 yrs (range 25 -74). Pts had received 1 (n=5) or 2 (n=4) prior lines of therapy. DL1 enrolled 3 pts without DLT. All DL1 pts achieved an MRD-neg CR and bridged to consolidation: 1 pt XRT to involved disease site (ankle) after 3 cycles and 2 pts to BMT after 2 cycles (Table). Three pts enrolled at DL2; no DLTs were observed. All achieved an MRD-neg CR. Two pts bridged to consolidation (donor lymphocyte infusion after 3 cycles, blinatumomab after 5 cycles) while 1 pt with KMT2A-r ALL experienced early relapse with lineage switch during second cycle. A confirmatory cohort of 3 pts enrolled at DL2 without DLT. All achieved a CR (n=2, MRD-neg; n=1, MRD-pos). The pt with MRD-pos CR as best response proceeded to blinatumomab as bridge to BMT after 2 cycles with 2 pts continuing treatment (currently cycle 2). Overall, CR was achieved in 100% (9/9) of pts with 7/8 (87%) achieving MRD-negativity. With median follow-up of 195 days (95% CI 80 - NR), 2 pts have relapsed 48 (on treatment) and 177 (after BMT) days from registration while other pts remain alive in CR. Non-heme grade 3-4 AEs include febrile neutropenia (2), DIC (1), tumor lysis syndrome (1), anxiety (1), hypertension (1), and hypotension (1). There have been no SOS. There were no delays in count recovery during C1, with median time from C1 to C2 being 30 days (range 27-42). Conclusion VEN 400mg x 21 days in combination with INO at standard doses was well tolerated and declared the recommended phase 2 dose (RP2D) with a CR rate of 100%.

A Multicenter Study of CAR-T Cell Therapy for Relapse of B-ALL Post Allogeneic Stem Cell Transplantation

BACKGROUND: Patients with acute B-cell lymphoblastic leukemia (B-ALL) relapsed after allogeneic stem cell transplantation (allo-HSCT) have very poor prognosis. Chimeric antigen receptor T (CAR-T) cells targeting CD19 have been developed as one of the effective immunotherapies for relapsed/refractory B-ALL. The safety and efficacy of CAR-T cells in patients relapsed after allo-HSCT remain unclear. METHODS: This study analyzed 60 B-ALL patients relapsed after allo-HSCT treated with CAR-T cells between October 2015 and February 2022 from four Chinese centers. Their pre-treatment patient characteristics, treatment regimens, efficacy, adverse effects, and follow-up data were comprehensively analyzed. RESULTS: One patient refused efficacy evaluation. 7 patients died before day 28 after CAR-T infusion. A total of 52 were assessed for efficacy within 28 days after CAR-T infusion.76.92% (40/52) patients achieved complete remission (CR) at Day 28 after CAR-T infusion, including 38 patients who achieved MRD-negative CR. 4 of the 40 patients relapsed at a median follow-up date of 12.1 months. The 1-year OS and EFS of all patients were 52.8% ± 7.0% and 51.5% ± 7.0%, respectively, and the 2-year OS and EFS were 40.1% ± 8.6% and 45.1% ± 8.6%, respectively. Multifactorial analysis showed that patients with severe CRS had worse OS and EFS, and other factors including age, gender, site of CAR-T tumor involvement, type of previous transplantation, previous transplantation type, CAR-T product and CRS grade, etc., did not affect the long-term survival of patients. The incidence of CRS was 80.00%, the incidence of grade ≥3 CRS was 20.83%, and the median time of CRS was 2 days after CAR-T cell infusion (range: 0-34 days). 3 patients (5.00%) died due to multiorgan failure caused by severe CRS, and the rest of the patients' CRS was controlled, and the grade of CRS was related to the proportion of blast cells in the bone marrow prior to CAR-T cell infusion., independent of the type of transplantation and the source of CAR-T cells. The incidence of ICANS was 5.00%. The incidence of aGvHD was 30.00%, and patients who had received prior haploidentical allogeneic HSCT were significantly more likely to develop aGvHD after CAR-T cell infusion than those who had received prior matched allogeneic HSCT. The occurrence of aGvHD after CAR-T treatment was not associated with the occurrence of CRS (p = 1), the presence of aGvHD after prior transplantation (p = 0.3484), the presence of cGvHD after prior transplantation (p = 0.3167), the presence of cGvHD at the time of CAR-T infusion (p = 0.5136), and the presence of prior donor lymphocyte infusion (p = 0.7404), and whether CAR-T cells were from autologous or donor (p = 0.4819). CONCLUSIONS: CAR-T cells are safe and effective in treating B-ALL patients with post-transplant relapse, and donor-derived CAR-T cells do not exacerbate CRS with aGVHD, and there is a high incidence of aGVHD after CAR-T therapy in patients with HLA-haplotype-matched transplantation.

Cladribine Combined with Homoharringtonine and Cytarabine Achieves a High Remission Rate in Adult Patients with De Novo Acute Myeloid Leukemia, Especially for Adverse-Risk Group: A Prospective, Single Center, Single-Arm, Phase 2 Study

Background: For adult de novo acute myeloid leukemia (AML), the standard 3+7 induction regimen has approximately 60% complete remission (CR) rate. Recently, BCL-2 inhibitor plus intensive chemotherapies as novel induction regimens have shown an above 90% composite complete remission (CRc) rate, however still have limited response effect in an adverse risk group, especially for patients with specific cytogenetic abnormalities such as KMT2A rearrangements, FLT3, RAS, and TP53 mutations. Multiple studies have shown that homoharringtonine (HHT) can target leukemia diseases that have switched their anti-apoptotic dependence from BCL-2 to MCL-1. We recently demonstrated that cladribine (CdA) could eradicate BCL-2 inhibitor-resistant monocytic leukemia stem cells driven by RAS mutants and KMT2A rearrangements. (Pei S, et al. Cancer Discovery. 2023) Together, these clinical and basic findings suggest a rationale for combining CdA with HHT to treat AML patients. In this study, we report the efficacy and safety of a newly designed “CHA” regimen composed of CdA, HHT, and cytarabine (AraC) in adult patients with de novo AML. Methods: This is a prospective, single-center, single-arm phase 2 trial. Newly diagnosed AML patients aged 18-59 years were enrolled. The diagnosis, risk classification, and response evaluation were determined according to ELN 2022 criteria. All enrolled patients received the CHA regimen: CdA (5mg/m2, days 1-3), HHT (2mg/m2, days 1-5), and AraC (100mg/ m2, days 1-7) administered intravenously. The response was evaluated on day 28 via bone marrow routine and minimal residual disease (MRD) measurement by flow cytometry. The primary endpoint was CRc (CR plus CRi). Secondary endpoints were MRD, overall survival (OS), disease-free survival (DFS), event-free survival (EFS), and adverse events. Bone marrow (BM) samples on day 1 and 7 and peripheral blood (PB) samples on days 1-7 were collected for laboratory flow analysis to monitor the kinetics of leukemia reduction. We also treated primary AML specimens with single, dual, and triple combinations of CdA, HHT, and Ara-C to evaluate their anti-leukemic activity in vitro. Statistical analyses were carried out using SPSS 24.0. Survival curves were prepared using the Kaplan-Meier method. A two-tailed P value <0.05 was considered statistically significant. This trial is registered on ClinicalTrials.gov (NCT05906914). Results: A total of 33 patients were enrolled from August 1, 2021, to April 15, 2023. The median age was 49 years. 33% (11/33) of patients were at favorable risk, 42% (14/33) were at intermediate risk, and 24% (8/24) were at adverse risk. After one course of CHA induction therapy, the CRc rate was 87% (27 of 31 patients), and the CR rate was 84% (26 of 31 patients). The CR rates in the favorable, intermediate, and adverse-risk groups were 82% (9 of 11 patients), 75% (9 of 12 patients), and 100% (8 of 8 patients), respectively. Notably, six out of six patients with KMT2A rearrangement and ten out of ten patients with RAS mutations achieved MRD-negative CR. The overall MRD negativity was 89% (24 of 27 patients with CRc). In 31 evaluable patients, four patients did not reach CR; three of them held FLT3 mutations. 30-days treatment-related mortality (TRM) was 6% (2 of 33 patients), and both died of sepsis. The median neutrophil recovery time (from the end of chemotherapy to the neutrophil counts ≥0.5×109/L) and platelets recovery time (from the end of chemotherapy to platelets counts ≥20×109/L) were both 11 days. With a median follow-up time of 13 months (IQR: 6-17 months), the one-year OS was 86%, 1-year DFS was 89%, and the 1-year EFS was 76%. Flow cytometry analysis of serially collected PB and BM samples from nine randomly selected patients revealed that an average of 91.0% and 94.7% of leukemia burden was cleared in the PB and BM by day 7, respectively, demonstrating a rapid and effective response induced by CHA. Finally, our in vitro assay demonstrated a synergistic effect of CdA, HHT, and Ara-C on primary AML specimens including three patients with adverse-risk. Conclusion: We propose the CHA regimen as a novel, effective, and safe chemotherapy regimen for newly diagnosed adult AML patients with remarkable potency in treating adverse-risk group patients, especially those with KMT2A rearrangements and RAS mutations that are otherwise resistant to BCL-2 inhibitor-based therapies, but a limited effect on FLT3mutated AML patients.

Ponatinib Versus Imatinib in Patients with Newly Diagnosed Ph+ ALL: Subgroup Analysis of the Phase 3 Phallcon Study

Background: BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy or steroids remain the standard of care in patients with newly diagnosed Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). Most patients treated with first- or second-generation TKIs eventually experience disease progression due to treatment resistance. Ponatinib is the only currently approved pan-BCR::ABL1 inhibitory TKI that potently inhibits wild-type and single resistance mutation variants of BCR::ABL1, including T315I. Multiple studies have shown promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with ponatinib in combination with chemotherapy or chemotherapy-free regimens. PhALLCON (NCT03589326) is the first randomized study comparing frontline TKIs in adults with Ph+ ALL. The primary endpoint for PhALLCON was met, with a clinically significantly higher MRD-neg complete remission (CR) rate at end of induction (EOI) with ponatinib vs imatinib (34.4% vs 16.7%; risk difference: 0.18 [95% confidence interval (CI): 0.06‒0.29]; P=0.0021) and a manageable safety profile comparable with imatinib. Here we report subgroup efficacy analyses from PhALLCON. Methods: This global, registrational, phase 3, open-label study randomized newly diagnosed adult patients with Ph+ ALL 2:1 to receive ponatinib (30 mg once daily [QD]) or imatinib (600 mg QD) plus reduced-intensity chemotherapy through EOI (Cycles 1-3), consolidation (Cycles 4-9), and post-consolidation (Cycles 10-20). Following post-consolidation, patients continued to receive single-agent ponatinib or imatinib until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg ( BCR:: ABL1 ≤0.01% [MR4])CR for 4 weeks at EOI. Event-free survival (EFS; any-cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. A post-hoc analysis of progression-free survival (PFS; EFS-defined events, failure to achieve MRD-neg by the end of treatment, and loss of MRD-neg) was conducted. Subgroup analyses were performed relative to baseline demographic and disease characteristics. Results: Of 245 randomized patients, 232 (ponatinib, n=154; imatinib, n=78) had baseline BCR::ABL1 p190/p210 variants verified by central lab (efficacy-evaluable population); median age was 54 years (37.1% ≥60 years). As of Aug 2022, 78 patients (ponatinib/imatinib: 68 [41.5%]/10 [12.3%]) remained on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (HSCT; 30.5%/37.0%), adverse events (12.2%/12.3%), and lack of efficacy (7.3%/25.9%). Median follow-up in the ponatinib and imatinib arms was 20 months and 18 months, respectively. Benefit for ponatinib was observed across all subgroups analyzed ( Table). All age subgroups had higher rates of MRD-neg CR with ponatinib vs imatinib, with the greatest benefit observed in patients ≥60 years (40.0% ponatinib vs 10.3% imatinib; P=0.0005). MRD-neg CR rate was higher for ponatinib vs imatinib among those with the BCR::ABL1 p190 variant (38.6%/17.0%; P=0.0017); it was higher for the p210 variant as well, but not significantly (22.5% vs 16.0%; P=0.51). Median PFS was longer with ponatinib vs imatinib regardless of age, with the greatest difference observed in the subgroup of patients ≥60 years (22.5 months for ponatinib vs 8.3 months for imatinib; hazard ratio: 0.594 [95% CI: 0.332-1.063]). Conclusions: Ponatinib was superior to imatinib in combination with reduced-intensity chemotherapy in the front-line setting for patients with Ph+ ALL, with a clinically significantly higher MRD-neg CR rate at EOI. Benefit was observed across all subgroups, particularly for patients ≥60 years and for those with the BCR::ABL1 p190 variant.

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.

Toward a Measurable Residual Disease-Based Algorithm for Selection of Allogeneic Hematopoietic Stem Cell Transplant in Acute Myeloid Leukemia

Background: The diagnosis and management of acute myeloid leukemia (AML) have transformed in recent years with an improved understanding of leukemogenesis and improved methods of measurable residual disease (MRD) detection. Current treatment algorithms include consideration of allogeneic hematopoietic stem cell transplant (HCT) for intermediate and adverse-risk AML. MRD negativity is widely accepted as a predictive and prognostic marker for disease-free survival and overall survival. However, the clinical use of MRD status in consolidative HCT planning remains unclear. Methods: Two hundred thirty-three consecutive patients achieving complete remission (CR) as defined in ELN 2022 after receiving therapy at Massey Cancer Center were analyzed. MRD status was determined either by multiparameter flow cytometry, PCR-based sequencing, and/or next-generation sequencing. Patients were analyzed via retrospective chart review to obtain baseline characteristics, molecular and cytogenetic profiles, and survival data. Median overall survival (mOS) was calculated and compared using the Kaplan-Meier method. Continuous variables were compared using one-way ANOVA. Categorical variables were analyzed using Fisher's exact test. Results: In total,109 patients achieved MRD-negative CR and 124 patients achieved an MRD-positive CR. Of the MRD-negative patients, 42 went received HCT (39%). In the MRD-positive cohort, 44 underwent HCT (35%). Among the MRD negative group, those receiving HCT tended to be younger (52.1 y. [range: 24.8-71.7] vs 61. 8 y. (range: 27.1-82.9) p = 0.026) with fewer co-morbidities (Charlson comorbidity index [CCI] score: 3 [range: 2-9] vs 4 (range: 0-14), p = 0.322). We observed a similar trend in those who had MRD positivity at best response or at the time of transplant (age 55 y. [range: 24.5-72.2] vs 62 y. [range: 25.1-88], p = 0.142; CCI 4 [range: 2-7] vs 5 (range 2-11], p = 0.014). In the MRD-negative/no HCT group, 49.3% had ELN favorable-risk disease at initial AML diagnosis, 28.4% had intermediate risk, and 22.4% had adverse risk. In the MRD-negative/HCT group, 31% were favorable risk, 33.3% intermediate risk, and 35.7% were adverse risk. In the MRD-positive/HCT group, 46.3% favorable risk, 23.8% intermediate risk, and 29.5% were adverse risk. There were no significant differences in ELN risk between any group. MRD-positive patients who underwent HCT had a mOS of 25.7 m. vs 20.7 m. for no HCT (HR=0.68 [95% CI, 0.41-1.11], p = 0.125). The median OS was not reached for MRD-negative patients, regardless of receipt of HCT (HR=0.61 [95% CI, 0.30-1.23], p = 0.168). Patients undergoing HCT in MRD-negative CR had improved OS compared to those undergoing HCT with persistent MRD positivity (p = 0.006). Discussion: MRD positivity is a known predictor of relapse and decreased survival despite HCT. However, the use of MRD as a decision point predicting which patients will benefit from transplant a priori needs to be better understood. Our data suggest that MRD negativity has a more significant impact on overall prognosis than HCT status.Likewise, the negative impact of MRD positivity was not significantly abrogated by subsequent HCT. This highlights the need for refinement in HCT selection beyond ELN 2022 intermediate/adverse-risk patients, and new validated algorithms incorporating MRD status are warranted.

Single Agent Tagraxofusp in Relapsed/Refractory CD123-Positive Acute Myeloid Leukemia: A Preliminary Analysis of Italian Gimema AML2020 Trial

Background and Aims: Tagraxofusp (SL-401; TAG) is a recombinant protein drug consisting of IL3 fused to a truncated diphtheria toxin payload that targets CD123, a subunit of the IL3 receptor, expressed on the surface of Acute Myeloid Leukemia (AML) blasts. TAG is currently approved for the treatment of blastic plasmacytoid dendritic cell neoplasm by the FDA and EMA. Here, we report the results of a preliminary analysis of the GIMEMA AML2020 trial which is the first study in Europe investigating the activity and safety of single agent TAG in patients with relapsed/refractory (R/R) CD123-positive AML. Patients and Methods: In this open-label, multi-center phase 2 study (NCT04342962) adult patients with R/R CD123-positive AML patients who received no more than 2 previous lines of therapy were eligible for enrollment. Tagraxofusp was administered at a dose of 12ug/kg from days 1 to 3 in the first cycle and then given for 5 days. Written informed consent for treatment, data collection and biobanking of biological samples was obtained for each patient enrolled. Results: As of July 2023, 23 patients have been enrolled. Median age was 65 years (41-75). Ten patients had refractory disease; 13 patients had relapsed disease. Nine patients were classified high risk at diagnosis according to ELN2017 classification. First-line treatment consisted of fludarabine-based induction, CPX-351, conventional anthracycline/Ara-C (3+7) induction for 22 patients and 1 patient received reduced intensity induction with hypomethylating agents + venetoclax. Second line treatments included azacytidine, azacytidine + venetoclax, gilteritinib; six patients received TAG as second line treatment. Two patients, who received allogeneic stem cell transplantation (allo-BMT) while in complete remission (CR), were enrolled at first relapse post-transplant. The median number of TAG cycles was 2 (range 1-10). Overall response rate (ORR) was 34.8% with 2 patients achieving MRD negative CR and 6 patients achieving partial remission (PR). As for treatment duration, 1 patient receiving 4 courses achieved PR and died due to CNS bleeding; 1 patient received 7 courses of TAG for early relapse after allo-BMT and achieved PR; 1 patient received 10 courses achieving PR. Early treatment discontinuation in the other cases was due to disease progression or adverse events (AEs). Emergent AEs are summarized in Figure 1. In addition, 3 patients developed leucocytosis immediately following TAG administration on the first course; in one case it was also associated with lung infiltrates. Capillary leak syndrome (CLS), a disorder characterized by leakage of intravascular fluids into the extravascular space, was reported in 5 patients: 2 patient experienced grade 2 (symptomatic) CLS which resolved with mild supportive treatment; 1 patient experienced grade 3 (severe), 1 grade 4 (life-threatening) and in one case the onset of CLS triggered by infectious event resulted fatal. One patient experienced the onset of acute renal failure and severe hypertension after C1 day 1 which resulted fatal, possibly being consistent with CLS. Conclusions: These results show that single agent TAG can exert anti-leukemic activity in R/R CD123-positive AML, even in cases with very unfavourable prognosis. However, further studies are necessary to disclose predictors of response and of the risk of adverse events. The safety profile observed here is similar to that previously observed for TAG requiring close monitoring of patients and timely supportive measures. However, overlapping of TAG-induced systemic inflammatory responses with refractory disease led to complex clinical management in some cases. Investigation of combinations strategies with TAG is warranted in order to optimize treatment efficacy, especially in the context of R/R AML.

Newly Dignosed Early T-Cell Precursor Acute Lymphoblastic Leukemia Successfully Treated with Venetoclax Combined with DA and IA Regime

Abstract Background: Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is a distinctive and extremely aggressive subtype of T-ALL. It is characterized by the aberrant expression of myeloid/stem cell antigens and the lack of Tlymphoid antigens including CD1a, CD4, CD5, and CD8. Currently, standard combination chemotherapy is still the mainstay of ETP-ALL treatment. However, the optimal management remains to be determined. ETP-ALL has low response rates to conventional chemotherapy and high relapse rates with a grim prognosis. Although some ETPALL patients achieved morphologic complete remission (CR), a more signifcant proportion maintained MRD positive. Under the traditional induction and intensifcation treatment strategy, the ETP-ALL group had worse long-term outcomes than the non-ETP-ALL group [1]. A recent preclinical study suggested that inhibition of B-cell lymphoma/leukemia-2 (BCL-2) might be a potential treatment option for patients with ETP-ALL [2]. Here, we present two cases of ETP-ALL clinical reactivity to venetoclax in combination with the IA regimen, providing a better bridge to allogeneic hematopoietic stem cell transplantation (allo-HSCT). Case 1 A 47-year-old female was diagnosed with ETPALL in October 2021. Flow cytometry analysis showed CD7,CD117,CD34,CD13,CD2,CD200,cyCD3 positive,suggestive of ETP ALL. Cytogenetic analysis was normal and molecular panel identified aberrations in TET, EP300 and EZH2. She then recived venetoclax plus DA regime（venetoclax, 100 mg d1, 200 mg d2, 400 mg qd d3-14；daunorubicin 40mg d1-3；cytarabine 100mg d1-5). A bone marrow biopsy after the 1st cycle revealed CR with minimum residual disease (MRD) 1.91% by flow cytometry. She then received 2nd cycle of venetoclax plus CAG treatment and got MRD negative. She received 2cycles of the same combination and remained in MRD-negative CR prior to proceeding with a reduced intensity haploidentical allo-transplantation. She is currently 1 years and 4 months post-transplant and in remission. Case 2 A 53-year-old man was diagnosed with ETP-ALL following bone marrow aspiration in August 2022. He presented with Leukopenia and anemia (WBC 2.53× 109 /L, HB 73 g/L, PLT 148 × 109 /L). Bone marrow biopsy revealed a hypercellular bone marrow with 80% lymphoid blasts, negative for MPO staining. The flow cytometry showed the immunophenotype of the lymphoid blasts (CD7+CD34+CD33+CD13+CD200+cyCD3+nTdT+), which were consistent with the immunophenotype of the ETP-leukemic cells. Cytogenetics revealed der(4)(q35).The molecular panel identified aberrations in CSF3R,DNMT3A,CCND3,CSF3R and WT1. Therefore, ETP-ALL was diagnosed. Initially, he received the first cycles of venetoclax combined with IA regimen (venetoclax, 100 mg d1, 200 mg d2, 400 mg qd d3-14;idarubicin 10mg d1-3,cytarabine 100mg d1-5), and CR was achieved this time. Then, he received a 3rd CAG therapy. Subsequently, he underwent hematopoietic stem cell transplantation (HSCT) successfully in December, and CR was still maintained at now 7 months after HSCT. Conclusion Combination therapy of venetoclax with IA regimen is an effective regimen for treating patients with ETP ALL.