MRD Status Research Articles

MRD Positivity Was the Poor Prognostic Factor for Adverse-Risk AML Patients with Allogeneic Hematopoietic Stem Cell Transplantation: A Multicenter Trohpy Study

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is recommended for acute myeloid leukemia (AML) patients with adverse-risk. However, when patients within this group would proceed to allo-HSCT is controversial. We aimed to identify the optimal timepoint for allo-HSCT for adverse-risk AML patients. Methods: This is a multicenter, retrospective designed study, based on the transplant database of Wuhan Tongji Hospital, Shanghai Ruijin Hospital, and Peking University Institute of Hematology (PUIH) (TROPHY group). Consecutive AML patients receiving allo-HSCT from January 2017 to June 2022 were screened, and the eligibility criteria were as followed: (1) aged ≥ 16 years; (2) adverse-risk AML based on ELN 2022 criteria; (3) achieving CR1 before allo-HSCT. The last follow-up was June 30, 2023. MRD status was monitored after the first consolidation chemotherapy (MRDc 1), after the second consolidation chemotherapy (MRDc 2), before allo-HSCT (MRD bft), and at 1, 2, 3, 4.5, 6, 9, and 12 months after allo-HSCT and at 6-month intervals thereafter. 0.1% was used as a threshold to distinguish MRD-positivity detected by multiparameter flow cytometry (MFC). The study was approved by the institutional review board of each participated hospital and was conducted in accordance with the Declaration of Helsinki. Results: A total of 391 adverse-risk AML patients were enrolled. 114 patients showed MRDc1 positivity. The 2-year probability of relapse, leukemia-free survival (LFS), and overall survival (OS) after allo-HSCT was 26.9% (95% CI: 18.1%-35.7%) vs. 9.4% (95% CI: 5.2%-13.6%) (P < 0.001), 60.7% (95% CI: 51.7%-71.1%) vs. 81.5% (95% CI: 76.3%-87.1%) (P < 0.001), and 74.4% (95% CI: 66.3%-83.3%) vs. 88.6% (95% CI: 84.4%-93.0%) (P < 0.001), respectively, for patients with MRDc 1 positivity and MRDc 1 negativity. Among patients with MRDc 1 positivity (n = 69), 24 (34.8%) turned MRD negativity after second consolidation therapy (MRDc 2 negativity). The similar trends were observed in patients with MRDc 2 positivity. The 2-year probability of relapse, LFS, and OS after allo-HSCT was 26.4% (95% CI: 18.1%-34.7%) vs. 9.4% (95% CI: 5.4%-13.3%) (P < 0.001), 61.2% (95% CI: 52.8%-71.0%) vs. 81.6% (95% CI: 76.6%-87.0%) (P < 0.001), and 75.6% (95% CI: 68.3%-83.8%) vs. 87.6% (95% CI: 83.3%-92.0%) (P < 0.001), respectively, for patients with MRD bft positivity and MRD bft negativity. Maintenance therapy provided better protection from relapse than preemptive therapy. In multivariate analysis, MRDc 1 positivity was associated with poorer LFS, MRDc 2 positivity was associated with a higher risk of relapse, and MRD bft positivity was associated with worse EFS after allo-HSCT. Conclusion: For the adverse-risk AML patients according to ELN2022 criteria, MRD is still the most important prognostic index for survival. Patients who achieved MRD negativity after the first consolidation chemotherapy could get similar clinical outcomes compared with those who achieved MRD negativity after the additional rounds of consolidation.

Risk Factors for Positive Posttransplantation Measurable Residual Disease in Patients with Acute Lymphoblastic Leukemia

Background: The level of MRD before and after transplantation is related to inferior transplant outcomes, and post-hematopoietic stem cell transplantation measurable residual disease (post-HSCT MRD) has higher prognostic value in determining risk than pre-HSCT MRD. However, no work has been devoted to the risk factors for positive post-HSCT MRD in patients with ALL. This study evaluated the risk factors for post-HSCT MRD positivity in patients with acute lymphoblastic leukemia (ALL) who underwent allogeneic HSCT (allo-HSCT). Methods: A total of 1683 ALL patients were enrolled. Cox proportional hazard regression models were built for time-to-event outcomes. Multivariate analysis was performed to determine independent influencing factors from the univariate analysis. Results: Both in total patients and in T-ALL or B-ALL, pediatric or adult, HLA-matched sibling donor transplantation or haploidentical HSCT subgroups, positive pre-HSCT MRD was a risk factor for post-HSCT MRD positivity ( P < 0.001 for all). Disease status was also a risk factor for post-HSCT MRD positivity in all patients and in the B-ALL, pediatric, or haploidentical SCT subgroups ( P =0.003; P=0.035; P =0.003, respectively). A risk score for post-HSCT MRD positivity was developed using the variables pre-HSCT MRD and disease status. The cumulative incidence of post-HSCT MRD positivity was 12.3%, 25.1%, and 38.8% for subjects with scores of 0, 1, and 2-3, respectively ( P<0.001). Multivariate analysis confirmed the association of the risk score with the cumulative incidence of post-HSCT MRD positivity and relapse as well as LFS and OS. Conclusion: Our results indicated that positive pre-MRD and disease status were two independent risk factors for post-HSCT MRD positivity in patients with ALL who underwent allogeneic HSCT.

Allo-HSCT Improved Outcome of High Risk ALL in Pediatric-Inspired PDT-ALL-2016 Cohort

Background Pediatric-inspired regimen have remarkably improved the prognosis of adult ALL, particularly for adolescent and young adult (AYA) patients. The role of allo-HSCT was controversy in the era of pediatric-inspired regimen. Some study revealed that patients treated with pediatric-inspired regimen those who achieved MRD negative may not require allo-HSCT (Ref1. Ribera et.al, Blood 2021; Ref2. Dhedin et.al, Blood, 2015). To address this issue, we performed study on HR ALL population in pediatric-inspired PDT-ALL-2016 cohort, by comparing outcome of allo-HSCT and chemotherapy groups. Methods PDT-ALL-2016 cohort is a GRAALL-backbone pediatric-inspired regimen (NCT03564470), patients diagnosed with ALL in Nanfang hospital were enrolled in JAN-2016 to DEC-2021. High-risk features included: WBC higher than 30×10^9/L for B-ALL or 100×10^9/L for T-ALL; pro-B or ETP; presence of t(9;22), t(1;19), t(4;11) or 11q23 rearrangements, Ph-like, complex karyotype, hypodiploid or near triploid; IKZF1 deletion/muation. Patients diagnosed with HR-ALL and achieved CR1 after induction were enrolled in this study. The left-truncated Kaplan-Meier estimator was used to compare the overall survival (OS), event-free survival (EFS), cumulative incidence of relapse (CIR) and non-relapse mortality (NRM). Results A total of 265 HR-ALL patients were enrolled in this study, 168 patients in allo-HSCT and 97 patients in chemotherapy cohorts, respectively. The baseline characteristics between two cohorts were comparable. With a median follow-up time of 43.6 months (3.8-60.0 months), the 3-yr OS and EFS were better in allo-HSCT cohort compared with chemo-only cohort (3-yr OS, 76.8% VS 55.6%, P＜0.001; 3-yr EFS, 66.5% VS 38.8%, P＜0.001). Meanwhile, the allo-HSCT cohort had lower CIR and higher but acceptable NRM compared with chemo-only cohort (3-yr CIR, 15.5% VS 55.5%, P＜0.001; 3-yr NRM, 13.8% VS 3.2%, P＜0.001; Table 1). For MRD positive subgroup (allo-HSCT, n=64; chemo-only, n=37), patients who underwent allo-HSCT had longer EFS and OS, and lower CIR compared with chemo-only cohort (3-yr OS, 71.0% VS 35.3%, P＜0.001; 3-yr EFS, 59.3% VS 25.6%, P＜0.001; 3-yr CIR, 19.8% VS 69.8%, P＜0.001). Of note, for MRD negative subgroup (allo-HSCT, n=96; chemo-only, n=51), the allo-HSCT cohort had longer EFS and lower CIR compared with chemo-only cohort, the OS also improved by allo-HSCT (3-yr OS, 81.2% VS 71.0%, P=0.173; 3-yr EFS, 71.1% VS 50.0%, P=0.014; 3-yr CIR, 14.6% VS 48.8%, P＜0.001; Fig 1). In multivariable analyses, allo-HSCT was protective factors for OS (HR=0.37), EFS (HR=0.56) and CIR (HR=0.45), and negatively infected NRM (HR=4.66). Conclusion Here, we showed that allo-HSCT further improved the outcome of HR ALL regardless of the MRD status, in the era of pediatric-inspired regimen. The survival advantage of allo-HSCT came from lower CIR compared with chemotherapy only. Furthermore, compared with published data, the NRM was more acceptable in our cohort. It is the high NRM (20-40%) in other studies ( Ref1. Ribera et.al, Blood 2021; Ref2. Dhedin et.al, Blood, 2015; Ref3. Wieduwilt et.al, leukemia, 2021; Ref4. Seftel et.al, AJH, 2015) that counterbalanced the benefit of CIR by allo-HSCT, which highlight the importance of experienced management for total therapy in adult ALL. This research was supported by the National Natural Science Foundation of China(NFSC82170163, 81970147), Clinical Study of Nanfang Hospital(LC2016ZD009/2019CR012).

Prognostic Value of MRD By Flow Cytometry in Adolescent and Adult Patients with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia Treated with Pediatric-Inspired Regimen: A Post-Hoc Analysis from a Prospective Study of China

Background Minimal residual disease (MRD) is currently considered as one of the most powerful predictors in patients with Philadelphia chromosome-negative acute lymphoblastic leukemia (Ph - ALL).The time points and thresholds for MRD monitoring in pediatric Ph - ALL have been well established. However, surveillance strategy in adult ALL has not yet been standardized. In this study, we explored the prognostic value of MRD levels and monitoring time points by flow cytometry (FCM) in adolescent and adult patients with Ph - ALL treated with pediatric-inspired regimen. Methods This analysis includes adolescent and adult patients who were treated according to a pediatric-inspired regimen revised based on Children's Oncology Group protocol (CCG-1961). This prospective study was registered at Chinese Clinical Trial Registry Website with the registration number of ChiCTR-OOC-15006328. MRD was measured using bone marrow aspirates with eight-color multiparametric FCM on day 14 of induction, at end of induction (EOI, days 29-42) , post the first consolidation (post-C1), and throughout the treatment period. MRD was defined as the percentage of lymphoblasts present in the total nucleated cells counted. MRD levels of < 0.01% and ≥ 0.01% was considered as negative and positive, respectively.Patients who were MRD-positive were further stratified into three groups according to MRD level: MRD low positive (MRD-lp), ≥ 0.01% to < 0.1%; MRD high positive (MRD-hp), ≥ 0.1% to < 1%; and MRD very high positive (MRD-vhp), ≥ 1%. Results From 2014 to 2021, a total of 415 patients with a median age of 27 (range: 14-69) years were treated. Three hundred and twelve patients presented with B-precursor ALL and 103 with T-cell ALL. With a median follow-up time of 40.8 months, the median overall survival (OS) of the cohort has not yet been reached. There were 386, 389, and 346 BM samples available for MRD evaluation on day 14 of induction, at EOI, and post-C1, respectively. Figure 1A presents the distribution of MRD status over time. Figure 1B depicts the compositions of MRD levels at EOI stratified according to disease types. Notably, Ph-like ALL and early T-cell precursor (ETP) ALL were associated with extremely lower achievements of MRD negativity at EOI compared with other types. The 5-year OS rates of patients with MRD negativity, MRD-lp, MRD-hp, and MRD-vhp at EOI were 68.0% (95% CI: 60.2%-75.8%), 44.8% (95% CI: 28.9%-60.7%), 52.4% (95% CI: 34.2%-70.6%), and 36.7% (95% CI: 24.2%-49.2%), respectively ( P < 0.001) (Figure 2A). If patients were censored at the time of hematopoietic stem cell transplantation, the 5-year OS rates of these patients were 74.9% (95% CI: 65.1%-84.7%), 39.7% (95% CI: 18.7%-60.7%), 42.3% (95% CI: 11.7%-72.9%) and 0%, respectively ( P < 0.001) (Figure 2B). Patients with a negative MRD at EOI had a more favorable OS than those with a positive MRD at EOI. There was no statistically significant difference in terms of survival time between patients with MRD-lp and MRD-hp. Further, patients with MRD-vhp had the worst survival. The relapse probabilities had a similar pattern. Patients with MRD negativity at EOI had a lower 5-year CIR than those with MRD positivity at any levels. Compared to MRD-lp and MRD-hp patients, patients with MRD-vhp experienced a significantly higher rate of early relapse. However, with a longer follow-up, the 5-year cumulative incidence of relapse (CIR) did not differ significantly among patients with a positive MRD in any of the three groups, with a rate of 47.4%, 43.8%, and 49.1% in patients with MRD-lp, MRD-hp, and MRD-vhp, respectively (Figure 2C). Multivariate analysis showed that positive post-induction MRD was one of independent predictors of both OS and Disease-free survival. Conclusion Our study confirmed that MRD negativity at EOI is an independent prognostic factor of OS in adolescent and adult patients with Ph - ALL treated with pediatric-inspired regimen. Patients with MRD-lp and MRD-hp at EOI had a lower OS and a higher relapse incidence than those with MRD negativity. Therefore, an early and deep MRD clearance is important, and even extremely low MRD levels can predict poor prognosis.

Analysis of Post-Transplant Clinical Outcomes and Prognostic Factors in FLT3-ITD Mutated Acute Myeloid Leukemia Patients Under ELN 2022 Risk Stratification

Background In 2022 European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML), one of the most important changes made to the genetic risk classification of AML is that the FLT3-ITD allelic ratio (AR) is no longer considered in the risk classification; consequently, AML with FLT3-ITD (without adverse-risk genetic lesions) are now categorized in the intermediate-risk group, irrespective of the allelic ratio or concurrent presence of NPM1 mutation. Aims To investigate the survival outcomes of FLT3-ITD mutated AML patients underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT), based on prognostic stratification defined by the 2017 and 2022 ELN guidelines, and to analyze the risk factors affecting transplant prognosis. Methods A total of 163 FLT3-ITD mutated AML patients underwent allo-HSCT were enrolled in this study. Bone marrow aspirates were obtained, cytogenetic and molecular characteristics were collected at the time of diagnosis. Genetic risk category was classified according to the 2017 and 2022 edition of the European LeukemiaNet (ELN) recommendations. HLA-haploidentical donor transplants were performed if no HLA matched sibling or unrelated donor was available. Patients received myeloablative conditioning with a modified Bu/Cy/Flu/Ara-c (busulfan/cyclophosphamide/fludarabine/cytarabine) or MCBC (melphalan/cladribine/busulfan/cyclophosphamide) preparative regimen. The therapeutic process and clinical outcomes were retrospectively analyzed. Results We assessed 163 adults with FLT3-mutated AML (median age 37 years) allografted between 2017 and 2022 in our clinical center. The median follow-up of alive patients was 24.9 months. The 2-year relapse-free survival (RFS) and overall survival (OS) were 67.2% and 71.9%, respectively. The 2-year incidences of relapse and non-relapse mortality were 27.9% and 12.5%, respectively. There was no significant difference in survival outcomes between the intermediate and high-risk groups after transplantation, both defined by the 2017 and 2022 ELN guidelines. High FLT3-ITD allelic ratio (≥0.5) at initial diagnosis was associated with elevated WBC counts ( P<0.001), but did not affect the response ratefollowing induction chemotherapy ( P=0.059) . Patients with high allelic ratio were more likely to benefit from maintenance therapy after transplantation ( P=0.048 for OS). In univariate analysis, presence of NPM1 mutation and the allelic ratio of FLT3-ITD did not affect any of the transplant outcomes. In multivariate analysis, MRD-negative at transplantation, occurrence of chronic GVHD and posttransplant maintenance therapy improved OS and RFS. Conclusion Allo-HSCT can overcome the poor prognosis in patients with FLT3-ITD mutated AML. Neither the presence of NPM1 mutation nor the FLT3-ITD allelic ratio affected survival. Prevention of disease relapse after transplantation remains a challenge. The main prognostic factors affecting transplant outcomes included pre-transplant MRD status and the application of maintenance therapy. Thus, introduction of FLT3 inhibitors as post-transplant maintenance therapy and the development of highly sensitive MRD assays will further reduce disease recurrence and improve survival.

Measurable Residual FLT3-ITD before Allogeneic Transplant for Acute Myeloid Leukemia

Background: In the past year, multiple studies have demonstrated the drastically increased risk of relapse and death in patients with Acute Myeloid Leukemia (AML) who have persistent FLT3 internal tandem duplication (ITD) mutations detectable in clinical remission by next generation sequencing (NGS). Translating this evidence into a change in clinical practice requires both widely available testing and a clear understanding of the clinical implications of FLT3-ITD detection at defined threshold levels. In the largest of the recent studies (Pre-MEASURE, PMID: 36881031), we performed FLT3-ITD MRD detection in blood DNA collected from 608 patients at the time of first remission (CR1) prior to allogeneic hematopoietic cell transplant (alloHCT). To evaluate cross-assay comparability and the impact of residual disease burden levels, we performed analysis on this cohort using a commercially available FLT3-ITD MRD NGS assay. Methods: Of the 608 patients aged 18 or older from the Pre-MEASURE study who received an alloHCT for FLT3-ITD mutated AML during CR1 at a CIBMTR reporting site in the USA between the years of 2013-2019, patients not experiencing non-relapse mortality and with sufficient DNA from pretransplant blood available were included in this analysis. A commercially available testing kit (IVS, Invivoscribe, San Diego, CA), which can detect FLT3-ITD MRD by NGS for up to 21 patients on one Illumina MiSeq flow cell, was used to establish a workflow following clinical testing standards and validated to detect ITDs down to a variant allele fraction (VAF) of at least 0.005%. Results were compared to those previously reported using an anchored multiplex PCR-based (AMP) targeted NGS assay. Overall survival (OS) and cumulative incidence of relapse were estimated with the day of transplant as time 0 using Kaplan-Meier estimation (log-rank tests) and Cox proportional hazards models. Results: A total of 451 patients were included in this study, of which 173 (38%) experienced relapse (median: 5.2 months; range 0.7-52.1) and 133 (29%) died (median: 10.7 months; range 2-53.8) post-alloHCT. The IVS assay identified 232 FLT3-ITD variants with a median VAF of 0.005% (range 0.0002-44%) and length of 51bp (range 5-228). IVS positive patients had a median of 1 FLT3-ITD variant (range 1-15) and median maximum VAF of 0.01% (range 0.0003-44%). Utilizing the same VAF cutoff of 0.01% for MRD positivity for the IVS test as used in the Pre-MEASURE study, patients testing positive prior to alloHCT exhibited higher rates of relapse (79% vs 31%, p<0.0001) and decreased survival (29% vs 77%, p<0.0001) at 3 years compared to testing negative. These results closely align with those previously reported using the AMP assay (Figure A). The IVS test has a superior limit of detection compared with the AMP test, allowing investigation of alternative VAF thresholds. In total, 151 patients (33.5%) were FLT3-ITD MRD positive by IVS of which only 75 (17%) had VAF ≥0.01%. A threshold-free approach for the IVS test improved the ability to identify patients at risk of relapse, predicting 63% of relapses within 6 months of transplant compared to 43% with the 0.01% cutoff, but resulted in decreased specificity as 42% of all positive patients relapsed within 6 months vs. 57% with the 0.01% VAF cutoff. In multivariable analysis, IVS FLT3-ITD MRD status was associated with both relapse and overall survival (Figure B). Additionally, stratifying patients by their level of residual FLT3-ITD disease burden prior to alloHCT revealed a dose-dependent increase in risk for death (Figure B) and relapse. Any detectable level of residual FLT3-ITD over 0.001% VAF exhibited increased risk, with VAFs ≥0.01% being the highest. Conclusions: In this analysis of patients with AML from the Pre-MEASURE study, we show cross-assay evidence that the detection of residual FLT3-ITD variants in pre-transplant blood during CR1 is associated with significantly increased risk of relapse and death after alloHCT. The highly sensitive assay used in this study could identify ~2/3 of patients who relapsed within 6 months and demonstrated that a dose-dependent correlation between residual FLT3-ITD level and adverse clinical outcomes exists, with VAF ≥0.01% representing the highest risk. This evidence provides strong justification for NGS-based AML MRD clinical testing for persistent FLT3-ITD prior to alloHCT to identify patients at high risk of post-transplant relapse and death.

Update of Olverembatinib (HQP1351) Overcoming Ponatinib and/or Asciminib Resistance in Patients (Pts) with Heavily Pretreated/Refractory Chronic Myeloid Leukemia (CML) and Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia (Ph + ALL)

Background Olverembatinib, a novel, potent BCR::ABL1 tyrosine kinase inhibitor (TKI), shows strong antitumor activity in pts with CML and Ph + ALL. Here, we report on the safety, efficacy, and pharmacokinetic (PK) profiles of olverembatinib in pts with CML (all phases) and Ph + ALL outside of China, particularly in pts previously treated with ponatinib and/or asciminib. Methods Olverembatinib was administered orally once every other day (QOD) in continuous 28-day cycles. In the monotherapy cohort, pts were enrolled after treatment failure on at least 2 prior TKIs and randomized to olverembatinib QOD 30, 40, or 50 mg. In the combination cohort, pts with Ph + B-cell precursor (BCP) ALL or lymphoid CML-BP (CML-LBP) resistant to at least 1 TKI were enrolled and received olverembatinib (30 or 40 mg) QOD in combination with blinatumomab. Results As of June 30, 2023, 76 pts were enrolled, including 57 with CML-CP and 19 with advanced Ph + leukemia. The median (range) age was 54.5 (21-80) years, and 56.6% of pts were male. In all, 11 (14.5%), 23 (30.3%), and 39 (51.3%) pts had received 2, 3, and ≥ 4 prior TKIs, respectively. A total of 52.6% of pts were previously treated with ponatinib, of whom 67.5% were resistant and 25.0% intolerant to the drug, and 7.5% experienced treatment failure for other reasons. A total of 27.6% of pts were previously treated with asciminib, of whom 71.4% were resistant and 19.1% intolerant to the agent, and 9.5% experienced treatment failure for other reasons. At baseline, 32% of pts had T315I mutations, 38% hypertension, and 17.1% other cardiovascular comorbidities. Median (range) treatment duration was 24.1 (0-134) weeks, and PK profiles were similar to historical PK data on Chinese pts. Twelve pts with CML-CP and 7 with advanced Ph + leukemia discontinued treatment: 4 because of AEs, 7 disease progression, and 8 other reasons. A total of 54 of 65 (83.1%) pts who received ≥ 1 dose of olverembatinib experienced any-grade TRAEs. Grade ≥ 3 AEs occurring in ≥ 3 pts (≥ 4.6% incidence) included thrombocytopenia (17%); neutropenia (13.8%); elevated blood creatine phosphokinase (13.8%); leukopenia (7.7%); and anemia and elevated lipase (4.6% each). Ten (15.4%) pts experienced olverembatinib treatment-related serious AEs, of which each were experienced by 1 (1.5%) pt. Two (3.1%) pts discontinued the study because of TRAEs. No TRAE-associated deaths were reported. Olverembatinib showed sustained antileukemic activity in pts with CML and Ph + ALL (Table 1). Among 50 efficacy-evaluable pts with CML-CP, the rate of complete cytogenetic response (CCyR) was 57% (25/44) and major molecular response (MMR) 43% (21/49). Efficacy improved over time; the MMR rate in pts with CML-CP treated for 6 months was 66% and 88% in pts treated for 12 months. Among pts whose disease failed ≥ 4 prior TKIs, CCyR and MMR rates were 57% (13/23) and 42% (11/26), respectively. In pts with CML-CP harboring the T315I mutation, rates of CCyR and MMR were 60% (9/15) and 44% (7/16), respectively, and 55% (16/29) and 42% (14/33) in pts without the T315I mutation. Among evaluable ponatinib-failed pts, 8/15 (53%) achieved CCyR and 6/16 (38%) MMR. Among pts who failed asciminib therapy, 3/7 (43%) achieved CCyR and 3/8 (38%) MMR. Of 8 pts with CML-CP who had prior exposure to both ponatinib and asciminib, 2 (25%) achieved MMR. At 24 months, PFS was 75% (95% CI, 56.1-86.7) and OS was 97.6% (95% CI, 90.8-99.4). Thirteen pts with advanced Ph + leukemia were efficacy-evaluable, of whom 3 (23%) achieved MMR; only 1 of 3 pts with the T315I mutation achieved MMR; the other 2 were also resistant to ponatinib treatment. The median (95% CI) PFS of efficacy-evaluable pts with advanced leukemia was 12.7 (4-19.5) months. In the combination cohort, 2 pts with Ph + BCP ALL received olverembatinib 30 mg QOD with blinatumomab; both achieved CCyR and 1 achieved a negative MRD status after 1 treatment cycle. Conclusions Olverembatinib alone or combined with blinatumomab was efficacious and well tolerated in pts with heavily pretreated CML or Ph + ALL . Olverembatinib monotherapy was potent in pts who were either resistant or intolerant to ponatinib and/or asciminib, regardless of T315I mutation status. Olverembatinib may provide an effective new treatment option for pts after failure of 2 or more TKIs. Internal study identifier: HQP1351-CU101. Clinicaltrials.gov identifier: NCT04260022.

Primary Endpoint Analysis from a Response Adaptive Phase II Clinical Trial of Carfilzomib, Lenalidomide, Dexamethasone Plus Daratumumab (KRd-Dara) in Patients with Newly Diagnosed Multiple Myeloma (NDMM)

Background Minimal residual disease (MRD) status has prognostic significance for progression-free survival (PFS) and overall survival (OS) in NDMM, but its value in guiding therapy remains unclear. We conducted a 2-stage, phase II trial evaluating the quadruplet regimen of KRd-Dara as induction therapy followed by MRD adapted KRd consolidation +/- autologous stem cell transplantation (ASCT) and maintenance versus observation. We previously reported the results of our stage I analysis at ASH 2022 (n=23; Blood 2022;140:4440-4441). Here we provide an updated analysis of the primary endpoint after completed enrollment of stage 2. Methods Eligible patients had NDMM with measurable disease. The induction phase allowed 8 cycles of KRd-Dara. Post-induction treatment assignment was informed by ASCT eligibility and MRD status by next generation sequencing (NGS at 10 -5), and included Group A (MRD negative, transplant-eligible and -ineligible, optional lenalidomide maintenance), Group B (MRD positive, transplant eligible, ASCT) and Group C (MRD positive, transplant ineligible, KRd consolidation for up to 12 cycles). Patients in Group B could receive up to 12 cycles of KRd consolidation therapy after ASCT if MRD positive. All groups could receive optional lenalidomide maintenance therapy after achievement of MRD negativity after induction ± consolidation. The primary endpoint was ≥complete response (CR) rate at the end of induction. The secondary endpoints were safety, MRD status, stem cell mobilization failure, and survival outcomes. Efficacy endpoints including MRD were evaluated with the intent to treat principle. Results Thirty-nine patients were enrolled: 23 in stage 1 and 16 in stage 2. Median age was 62 (range 34-78), 31% were female and 31% were African American. R-ISS stage 3 was present in 4 (10%), high-risk cytogenetics (including 1q21 gain) in 15 (39%). At the end of induction, ≥CR was achieved in 22/39 (56%, 90% CI: 42%-70%) patients including stringent CR (sCR) in 17 (44%), VGPR in 14 (36%) and PR in 1(3%). Of note, 2 patients did not complete induction therapy; one died during cycle 2, while another was withdrawn from study after an SAE during cycle 1. Evaluating by NGS, 62% achieved MRD negativity at 10 -5 and 41% MRD negativity at 10 -6 post-induction. MRD negativity by next generation flow cytometry (NGF) was 74% at 10 -5 and 31% at 10 -6. Concordance of MRD by NGS/ NGF at 10 -5 was 26/34 (76% in agreement and 24% disagreement, Cohen's kappa: 0.436), and by NGS/ NGF at 10 -6 was 17/25 (68% in agreement and 32% disagreement, Cohen's kappa: 0.351). 39 patients (100%) experienced treatment emergent AE, with grade ≥ 3 AE in 31 (80%). The most common (≥ 25%) any grade treatment related AE (TRAE) were diarrhea (39%), fatigue (36%), neutropenia (28%), and constipation (26%). Grade 3-4 TRAE (≥10% of patients) included neutropenia (21%) and hypophosphatemia (13%). Covid infection occurred in 10 (26%); only one patient needed hospitalization. Other infections (any grade) were seen in 20 (51%) patients. Fourteen (36%) patients experienced at least one SAE, of which 8 patients had a treatment-related SAE, including one death. Thromboembolic events were observed in 3 (8%) patients. Of 23 patients who collected stem cells upon completion of induction (7-8 cycles of KRD-Dara), 7 (30%) failed to collect an optimal target (3 million CD34+ cells/kg) on first attempt. Comparatively, 0 of 11 patients who collected after 3-5 cycles experienced stem cell collection failure (Fisher's exact: p=0.07). Post-induction, 24 patients were assigned to Group A, 8 to Group B, and 5 to Group C. After a median follow up of 26 months (95% CI: 17 - 27; data cut off 7/6/2023), 28 remain on treatment, 9 are in follow up, and 2 are off study. The 2-year PFS is 85.3% (95% CI: 71.6% - 99.1%); median PFS is not reached. Updated data on the best MRD/ CR/ sCR responses achieved post-induction will be presented at the meeting. Conclusions Our data confirm high rates of sCR and MRD negativity of the quadruplet regimen of KRd-Dara in NDMM. The safety data was in alignment with known safety profile of investigational products. With modification of the protocol to allow earlier stem cell collection, we were able to reduce the rate of stem cell mobilization failure from 30% to 0%. Based on our results, we recommend further testing of this MRD-based platform in randomized studies with stem cell collection after 3-4 cycles of KRd-Dara. Clinical trial: NCT04113018

Undetectable MRD Status in Patients with R/R CLL/SLL with Stable Disease after Lisocabtagene Maraleucel Treatment: Exploratory Analysis of the TRANSCEND CLL 004 Study

Background:For patients (pts) with R/R CLL/SLL after failure of Bruton tyrosine kinase inhibitor (BTKi) and B-cell lymphoma 2 inhibitor (BCL2i)-based treatment, there is no established standard of care and therefore there is a high unmet therapeutic need. The phase 1/2 TRANSCEND CLL 004 study (NCT03331198) investigated the efficacy and safety of lisocabtagene maraleucel(liso-cel) monotherapy, an autologous CD19-directed CAR T cell therapy, in pts with heavily pretreated R/R CLL/SLL and ≥ 2 previous lines of therapy, including a BTKi. The primary analysis demonstrated durable CR/CR with incomplete marrow recovery (CRi) per 2018 International Workshop on CLL (iwCLL 2018) criteria, high undetectable MRD (uMRD; 10 −4 sensitivity) rates, and a manageable safety profile in pts who received liso-cel (Siddiqi T, et al. Lancet 2023). All evaluable responders (CR/CRi/PR) achieved blood uMRD status. Among evaluable pts with stable disease (SD), uMRD status was associated with longer median PFS (6.4 months) versus MRD-positive (MRD+) status (PFS, 2.8 months). This exploratory analysis aimed to better understand potential variables associated with achieving uMRD in pts who had SD with liso-cel. Methods: Among 96 pts in the full efficacy set who were treated with liso-cel at dose level 1 (50 × 10⁶ CAR + T cells) or 2 (100 × 10⁶ CAR + T cells), 80 pts were evaluable for peripheral blood MRD. Peripheral blood MRD status was assessed by next-generation sequencing (NGS; clonoSEQ) assay; uMRD was defined as < 10 −4 (< 1 CLL cell per 10,000) at 1 or more postinfusion time points. Additional exploratory analysis leveraged sample-level MRD results defined by total clonal cells/total nucleated cells assessed by NGS. Cellular kinetics were analyzed in peripheral blood samples by qPCR to detect the liso-cel transgene. Correlative analysis studies of baseline markers of tumor burden (sum of the product of diameters; CD19 + cells/μL; percent CLL cells in bone marrow biopsies or aspirates) with liso-cel expansion were evaluated by MRD status. Statistical analyses were performed using the Wilcoxon signed-rank test. Results:Of the 80 pts who were evaluable for peripheral blood MRD, 34 had a best overall response of SD, 19 of whom achieved uMRD and 15 who were MRD+. Greater liso-cel expansion parameters (median maximum expansion and area under the curve from 0-28 days postinfusion) were observed in all pts, including those with SD, who achieved uMRD versus MRD+ status ( P < 0.0001), suggesting that higher liso-cel expansion after infusion was associated with achievement of uMRD independent of iwCLL 2018 response. Regardless of baseline tumor burden, pts with higher liso-cel expansion achieved uMRD after liso-cel treatment. A positive association between tumor burden and liso-cel expansion in pts with SD and uMRD was also observed. In contrast, pts with SD who were MRD+ had lower liso-cel expansion and trends of higher baseline disease burden. Liso-cel expansion in pts with SD and uMRD clustered with the responders, who all achieved uMRD status (in those evaluable for MRD). Notably, 4 pts with SD and uMRD had a durable disease control of > 22 months. We wanted to further understand the relationship between uMRD and durable disease control. Given that the median PFS of pts with SD and uMRD was 6 months, we evaluated the association between tumor burden and liso-cel expansion in pts who had a PFS of ≤ 6 months or > 6 months. Although no clear association was observed with liso-cel expansion and tumor burden within these 2 groups, 4 out of 5 pts with SD and uMRD with longer disease control (PFS > 6 months) had a > 98% decrease in sample-level MRD from Month 1 to Month 3. In contrast, in pts with SD and uMRD with PFS ≤ 6 months, 5 out of 7 pts had a > 70% increase in sample-level MRD from Month 1 to Month 3. Conclusions:In this exploratory analysis of pts with R/R CLL who had SD by iwCLL 2018 criteria after liso-cel treatment, greater liso-cel expansion, regardless of baseline tumor burden, correlated with blood uMRD status. Additionally, those with a PFS > 6 months achieved deeper clearance of blood sample-level MRD within 3 months of treatment versus those with a PFS ≤ 6 months, suggesting that MRD kinetics may identify pts with SD who can achieve durable disease control despite not achieving a response per iwCLL 2018 criteria. Further investigation is needed to better understand which subsets of pts with CLL who had SD may derive clinical benefit from liso-cel.

Toxicities Associated with Tyrosine Kinase Inhibitor Maintenance Following Allogeneic Hematopoietic Cell Transplantation in Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Background Use of tyrosine kinase inhibitor (TKI) maintenance following allogeneic hematopoietic cell transplantation (HCT) in Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia may help to prevent post HCT relapse but is difficult to administer due to toxicity. However, these toxicities and their impact on maintenance is not fully characterized. Herein, we report our experience at a single, large transplant center to describe toxicities encountered with post HCT TKI maintenance in Ph+ ALL. Methods Ph+ ALL patients (pts) who underwent 1st allogeneic HCT at City of Hope between 2003-2021 and received at least one dose of TKI maintenance were included in this retrospective analysis. Baseline characteristics and toxicities were summarized via descriptive analysis, and groups were compared via Fischer test. Survival analyses were calculated from the time of TKI initiation. Results Baseline characteristics are described in Table 1. Of the 186 pts studied, 50 (26.8%) received imatinib and 136 (73.2%) received a newer generation TKI (NG-TKI: 112 dasatinib, 6 nilotinib, 1 bosutinib, 17 ponatinib) at a median time of 78 days (IQR, 41-134) and 91 days (IQR, 58-129), respectively. A total of 96 patients (51.6%) began TKI maintenance within 90 days of HCT. Post HCT TKI was started prophylactically in 149 patients (80.1%) while 37 patients (19.9%) received TKI preemptively for positive MRD. The MRD status at time of HCT differed between the imatinib group and NG-TKI group. In the imatinib group MRD was negative in 33 of 50 patients (66.0%) compared with 78 of 136 patients (57.4%) in the NG-TKI group (P<0.01). There were 12 (24.0%) vs 18 (13.2%) with an unknown MRD-status at HCT in the imatinib vs NG-TKI groups, respectively ( P<0.01). The median follow-up duration for surviving patients in the entire cohort was 5.5 years (range, 1.0-17.5). The median cumulative TKI exposure was 413.5 days (range, 4-2740). The median cumulative imatinib exposure in patients initially receiving imatinib was 328 days (range, 3-2216), while the median cumulative NG-TKI exposure in patients initially receiving NG-TKI was 268.5 days (range, 3-2740), respectively. The median cumulative exposure of dasatinib, nilotinib, bosutinib and ponatinib were 249 days (range, 3-2740), 222 days (range, 114-839), 371 days, and 576 days (range, 72-921), respectively. Twenty-seven (54.0%) vs 75 (55.2%) patients completed >12 months of initial imatinib and NG-TKI maintenance (P=1.0), respectively. Of the treated patients, 78 pts (41.9%) required at least one dose reduction of their initial TKI due to toxicity; 19 of them (10.2%) required ≥2 dose reductions. When imatinib maintenance was used as the initial TKI, a dose reduction due to toxicity was required in 18 patients (36.0%), of whom 7 patients (14.0%) required ≥2 dose reductions. Initial NG-TKI maintenance required a dose reduction due to toxicity in 60 (44.1%), of whom 12 (8.8%) required ≥2 dose reductions. One hundred and thirty-nine patients (74.7%) had their maintenance TKI therapy interrupted, 122 (65.6%) due to toxicity. Sixty-seven patients (36.0%) did not complete their pre-determined maintenance period owing to toxicity; 70 pts (37.6%) discontinued one TKI, and 11 (5.9%) discontinued two TKIs, due to toxicity. The most common reasons for discontinuing the initial TKI are listed in Table 2, including 45.2% of patients due to toxicity, and 12.9% due to progressive disease. Toxicity-related discontinuations occurred within 6 months on that TKI in 63.0% of patients, and 75.3% within the first 12 months. Five-year overall survival and progression-free survival from the start of TKI were similar between the imatinib and NG-TKI group; 83.1% vs 76.9% (P=0.74) and 72.8% vs 70.5% (P=0.63), respectively (Figure 1). Conclusion Toxicities resulting in dose reductions, interruptions, and discontinuation are common in TKI maintenance post HCT. The toxicity profile (mainly GI and blood count related), frequency, and severity of TKIs in the post HCT setting appears to be different than what has been previously reported in the pre-HCT setting, making it a formidable challenge to meet the recommended cumulative TKI maintenance exposure (2 years) per the NCCN guidelines. While the choice of TKI did not appear to impact on long-term outcomes and relapse rates were not excessive in our analysis, further studies are needed to develop tolerable and personalized TKI maintenance strategies.

Impact of Socioeconomic Disparities on Outcomes in Adults Undergoing Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia

Introduction: It is increasingly recognized that racial and socioeconomic disparities play an important prognostic role and contribute to differences in outcomes in adults receiving chemotherapy for acute myeloid leukemia (AML). Structural racism has also been implicated in limiting access to allogeneic hematopoietic cell transplantation (HCT). However, it is unclear to what degree racial and socioeconomic disparities impact post-HCT outcomes of patients with AML in contemporary practice. To address this uncertainty, we investigated the impact of socioeconomic, racial, and non-biologic disparities on outcomes in a large cohort of adults with AML undergoing allogeneic HCT while in first or second morphologic remission. Methods: We identified 1,004 adults with AML (2022 ICC criteria) who underwent allogeneic HCT between 5/2006 and 10/2021 at a single large university-affiliated cancer center. Data was collected on each patient's individual socioeconomic status (SES), including occupation, insurance type, and education attainment. Distance traveled, marital status, household size, country of birth, and religious affiliation were also recorded. Each occupation was classified by the International Socio-Economic Index (ISEI), a standard index of occupational status. Area-level SES was analyzed through the Area Deprivation Index (ADI), a validated measure of socioeconomic disadvantage which corresponds to U.S. census tract measurements. Collected HCT variables include the AML treatment-related mortality score (TRM), pre-HCT flow cytometric MRD status, HLA donor status, cytogenetic risk, conditioning regimen intensity, and incidence of severe acute and chronic graft-vs-host disease. Measured outcomes include non-relapse mortality (NRM), overall survival (OS), relapse, and relapse free survival (RFS). Cause-specific hazard models were used for univariate and multivariable regression analysis and C-statistics were calculated to quantify each model's ability to predict outcomes. Results: In univariate analysis, none of the socioeconomic or non-biologic factors were significantly associated with NRM, and all had poor predictive performance, with C-statistics not exceeding 0.53 for: marital status, larger household size (i.e., patients with children), distance traveled, ISEI, ADI, insurance status, educational attainment, or country of birth. TRM score (P<0.001), non-myeloablative conditioning (P<0.001), reduced intensity conditioning (P<0.001), CR2 (P=0.017) and marital status (P=0.014) were significantly associated with NRM in a multivariable model, but predictive performance of this model was only fair (C=0.69; Table 1). Marital status was only associated with NRM after multivariable adjustment but not on univariate evaluation, possibly because married patients were, on average, older (P<0.001), more likely to be male (P<0.001), and have higher occupational status/ISEI (P<0.001) and TRM scores (P<0.001), with age and sex as likely confounders (Table 2). African American patients (n=14) were found to have worse NRM in both univariate (P=0.036) and multivariate (P=0.024) models, consistent with previously identified racial/ethnic disparities in AML cohorts. Similar results were found for SES and non-biologic variables in regards to OS, relapse, and RFS. Notable exceptions after multivariable adjustment include: ADI was significantly associated with OS (P=0.036) and RFS (P=0.044) and marital status was not significantly associated with OS or relapse. Additional analyses demonstrated that ISEI and ADI were not associated with increased TRM or HLA donor status. Finally, distance traveled decreased in HCT recipients post-2013 (P<0.003), though the number of AML-related transplants remained unchanged. Conclusion: In this retrospective, single center analysis, socioeconomic and non-biologic factors had very limited impact on outcomes following allografting for adults with AML. While reassuring, patients able to undergo allogeneic HCT are highly selected (e.g. need for caregiver, insurance, etc.) possibly accounting for this finding, as could integrated, multidisciplinary cancer care networks and longitudinal care coordination post-HCT. Further research is needed to investigate disparities among HCT-eligible patients and improve access to HCT with a focus on reducing racial/ethnic disparities.

Non-Invasive MRD Monitoring in Multiple Myeloma Patients By Heavy/Light Chain Analysis

Introduction The majority of multiple myeloma (MM) patients are now achieving very deep responses. The most sensitive disease detection techniques are currently bone marrow assays. However, as bone marrow sampling is invasive and unpleasant for patients it is important to investigate whether blood-based assays could be equally or more informative of disease status. The heavy/light chain assay (Hevylite TM, The Binding Site, UK) evaluates serum heavy/light chains (HLC) for IgG, IgA and IgM M-proteins. This study assessed whether the HLC assay could act as an effective marker for disease in the bone marrow of treated MM patients and evaluated the prognostic utility of HLC measurements at best response and relapse time points. Methods 104 IgG and IgA MM patients were recruited either prior to transplant or during chemotherapy. Median follow up was 18 months. Routine M-protein tests were performed alongside HLC testing with parameters including involved HLC (iHLC), uninvolved HLC (uHLC) and kappa/lambda HLC ratio (HLCr). A bone marrow flow cytometry (NGF) assay was performed up to a sensitivity of 10 -6 and was considered to be the gold standard assay. Disease response was determined according to the IMWG criteria. Results and Discussion At pre- and post-transplant time points there was significant agreement between HLC measurements and NGF, with uHLC being the most sensitive measurement (86%) and HLCr the most specific (100%). Both uHLC and HLCr show substantial agreement with the bone marrow NGF method whilst iHLC cannot be used to indicate bone marrow status. Survival analysis showed significantly inferior progression free survival (PFS) in patients with an abnormal uHLC (p=0.01) (Figure A) or HLCr (p=0.02) result post-transplant but no survival difference based on iHLC status (p=0.78) (Figure B). Interestingly, performing survival analysis on these same samples using serum immunofixation (IFE) status (positive or negative) did not produce a significant PFS difference between participants (p=0.21). During long term follow up, HLC values showed a correlation with depth of response, with uHLC being abnormal in 60% of complete response (CR) patients. This suggests that those participants currently grouped as CR may be able to be further subdivided according to uHLC level and this could have a prognostic value in the monitoring and treatment of these patients. At best response uHLC was the only HLC or free light chain (FLC) measurement which gave a significant difference in PFS for all patients in partial response (PR) or better (p=0.005), remaining true when analysing patients in ≥CR only (p=0.002). The addition of free light chain measurements into the HLC analysis did not improve the significance of these survival differences. In relapsed patients, paired comparisons of M-protein and disease activity markers at best response vs. prior to clinical relapse were performed. uHLC was the only marker which was significantly different between the two time points in IgG and IgA patients. The significance of this was confirmed by showing that those patients in stable disease did not experience a significant change in uHLC levels. For other M-protein variables such as total immunoglobulin, IFE status and FLC values there was an increase in levels or abnormality between best response and pre-relapse but these were not significant. The paired comparison suggests that monitoring an individual using HLC could help to detect relapse earlier than conventional methods. In all analyses performed the HLC assay showed increased sensitivity and utility over the IFE technique. Conclusion This study suggests that the HLC assay can be used prior to bone marrow analysis to help influence decisions and improve the patient and laboratory experience. These results can be put into practice during patient follow up post initial treatment in the following ways: At deepest response an abnormal uHLC or HLCr suggests a positive MRD status, meaning a possible reduction or delay in the requirement for bone marrow assessment.All patients in ≥VGPR should have HLC performed alongside conventional assays during follow up.If uHLC values become abnormal during follow up then it should be assumed that the patient is about to undergo relapse. The measurement of HLC values have been shown to be a significant marker in this study, for sensitively detecting the M-protein, giving further clarification of response status and predicting early relapse.

Fixed Duration Combination Therapy with Carfilzomib, Lenalidomide, and Dexamethasone Followed By Lenalidomide Maintenance Leads to High Rates of Sustained MRD Negativity in Patients with High-Risk Smoldering Multiple Myeloma: Long Term Follow up of an Investigator Initiated Phase 2 Trial

Background: Patients with high-risk smoldering multiple myeloma (HR-SMM) have a 5-year risk of progression to symptomatic multiple myeloma of approximately 75% and a median time to progression of less than 2 years (Lakshman et al., Blood Cancer J 2018) (Rajkumar et al., Blood 2015). We previously reported the primary results of our phase 2 trial of carfilzomib, lenalidomide, and dexamethasone followed by lenalidomide maintenance (KRd-R) as prevention of symptomatic multiple myeloma in patients with HR-SMM (Kazandjian et al., JAMA Onc 2021). Herein, we present follow-up data after all patients have completed lenalidomide maintenance to evaluate the durability of responses off therapy. Methods: Patients with HR-SMM based on the Mayo Clinic, PETHEMA, and/or Rajkumar, Mateos, and Landgren criteria were eligible for enrollment in this single-center phase 2 investigator-initiated study. Patients received eight 28-day cycles (induction) of carfilzomib, 20/36 mg/m 2, with dexamethasone 20/10 (days 1,2, 8, 9, 15, 16) and lenalidomide 25 mg (days 1-21), followed by 2 years of maintenance therapy with lenalidomide 10 mg (days 1-21). The primary endpoint was the rate of minimum residual disease negative complete responses (MRD negative CR) at the end of induction as assessed by multicolor flow cytometry (MRD sensitivity 10 -5). Secondary objectives included progression to overt clinical multiple myeloma (end-organ damage or myeloma-defining event) or death (clinical PFS) and biochemical progression (PD) by IMWG criteria (biochemical PFS). Results: A total of54 patients were enrolled and started treatment between May 29, 2012 and July 23, 2020. Full patient demographics and baseline disease characteristics were previously reported. (Kazandjian et al., JAMA Onc 2021) At the data cut-off of July 17, 2023, the median follow-up time was 60.2 months (range: 33.7 - 127.8). As previously reported, 38 patients (70.4%) achieved MRD negative CR by the end of induction. The median duration of MRD negative CR was 57.4 months (95% CI: 44.6 - 97.2). To date, durability of MRD negative CR has been observed up to 120.6 months and 21 patients (39%) have remained MRD negative for over 2 years (95% CI: 25.9 - 53.1%). (Figure 1) All patients attained a PR or better and the median duration of response has still not been reached. At 60 months, 75.1% of patients maintained their response (95% CI: 59.9 - 85.2%). The median clinical PFS has also not been reached. Only 5 out of 54 (9.3%; 95% CI: 3.1-20.3%) patients have progressed to clinical multiple myeloma. At 60 months, 92.7% of patients were free from clinical progression (95% CI: 78.1 - 97.9%). The probability of being free of clinical progression at 100 months was 78.9% (95% CI: 51.9 - 91.8%). While the median biochemical PFS has not been reached, patients who were MRD negative by the end of induction had significantly less risk of having biochemical progression compared to patients who still had measurable disease at completion of induction (median biochemical PFS NR vs. 41.8 (HR 0.168 (95% CI: 0.060 - 0.474) (P value < 0.0001) (Figure 2). As previously reported, KRd-R was well tolerated, with no grade 4 non-hematologic adverse events and manageable low-grade toxicities. Discussion: Treatment of patients with HR-SMM with KRd-R has led to deep and durable remissions. At a median of 5 years of follow-up, this trial has yet to reach a median clinical PFS, indicating success in preventing serious end organ damage. However, it is still unclear if the beneficial outcomes seen in HR-SMM interventional studies are due to treatment of more susceptible disease or inherently less aggressive disease. An abstract evaluating the genomic profile of patients from this trial has been submitted to the meeting separately. Future prospective trials must capture and eventually select HR profiles based on validated genomic signatures. This study suggests that patients who achieve MRD negative remissions after induction therapy have prolonged biochemical PFS. However, further follow-up time is needed to fully understand the rates of clinical PFS and OS. To evaluate if additional treatment duration to achieve MRD negativity would be beneficial we have designed a trial using daratumumab, carfilzomib, and dexamethasone utilizing an adaptive treatment duration based on MRD status for patients with HR-SMM which is currently enrolling participants (NCT04933539).

First-Line Fixed-Duration Ibrutinib Plus Venetoclax (Ibr+Ven) Versus Chlorambucil Plus Obinutuzumab (Clb+O): 55-Month Follow-up from the Glow Study

Introduction : In the GLOW trial (NCT03462719), fixed-duration Ibr+Ven treatment has shown superiority to Clb+O in progression-free survival (PFS), better sustained undetectable minimal residual disease (uMRD) responses, and overall survival (OS) benefit in patients with previously untreated chronic lymphocytic leukemia (CLL) who are older and/or have comorbidities (CU Niemann, et al. Blood. 2022;140[suppl 1]:228-230). In this analysis, we report clinical outcomes, including PFS, OS, and MRD analysis, from the Ibr+Ven combination in GLOW with a median follow-up of 55 months, including subgroup analyses by IGHV and MRD. Methods : Patients aged ≥ 65 years or 18 to 64 years with a Cumulative Illness Rating Scale score > 6 or creatinine clearance < 70 mL/min were randomized 1:1 to Ibr+Ven (3 cycles of Ibr lead-in, followed by 12 cycles of Ibr+Ven; N = 106) or 6 cycles of Clb+O (N = 105). Each cycle was 28 days. Patients were excluded if they had del17p or known TP53 mutations at screening. End points included investigator-assessed PFS, uMRD rates, time to next treatment (TTNT), and OS. MRD was assessed sequentially over time in peripheral blood by next-generation sequencing for patients with partial response (PR) or better. Patients with < 1 CLL cell per 10,000 leukocytes (< 10 -4) were considered to have uMRD, whereas patients with ≥ 1 CLL cell per 10,000 leukocytes (≥ 10 -4) were considered to have detectable MRD (dMRD). All p values reported were nominal. Safety was not further assessed, as all patients were already past the treatment period in previous analyses. Results of updated analyses : With a median follow-up of 55 months, PFS remained superior for Ibr+Ven (hazard ratio [HR] 0.239 [95% confidence interval (CI), 0.159-0.359]; p < 0.0001); 54-month PFS rates were 65.8% for Ibr+Ven and 19.1% for Clb+O. In the Ibr+Ven arm, for patients with unmutated IGHV (uIGHV; n = 67) and mutated IGHV (mIGHV; n = 32), 54-month PFS rates were 58% and 90%, respectively. Also in the Ibr+Ven arm, PFS rates at 3 years post-treatment were 82% in patients who achieved uMRD at 3 months after end of treatment (EOT+3; n = 58) and 73% for patients with dMRD (n = 31). Among patients with uIGHV, PFS rates at 3 years post-treatment were 81% for those achieving uMRD at EOT+3 (n = 40) and 56% for those with dMRD (n = 16). In patients with mIGHV, PFS rates at 3 years post-treatment were ≥ 92% regardless of MRD status at EOT+3. Overall, at 38 months after end of treatment (EOT+38), 32.1% of patients had uMRD in the Ibr+Ven arm. Of the patients who achieved uMRD at EOT+3 (n = 58), 53.4% sustained uMRD status at EOT+38 in the Ibr+Ven arm. In addition, TTNT was prolonged for patients receiving Ibr+Ven versus Clb+O. The risk of needing second-line therapy was significantly reduced by 83% with first-line Ibr+Ven versus Clb+O (HR 0.174 [95% CI, 0.088-0.342]; p < 0.0001), and by 85% among patients with uIGHV (HR 0.146 [95% CI, 0.069-0.310]) compared with a 29% risk reduction in those with mIGHV (HR 0.708 [95% CI, 0.118-4.256]). In the Ibr+Ven arm, 4 patients received single-agent ibrutinib as subsequent therapy as part of the study; while 1 patient had not yet had a disease assessment, the best response for the other 3 patients were complete response (n = 1) and PR (n = 2). Finally, Ibr+Ven continues to demonstrate improved OS versus Clb+O, reducing the risk of death by 58% (HR 0.421 [95% CI, 0.237-0.747]; p = 0.0023). Estimated 54-month OS rates were 84.5% for the Ibr+Ven arm and 63.1% for the Clb+O arm. Conclusion : With prolonged follow-up of 55 months in the GLOW study, all-oral, once-daily, fixed-duration Ibr+Ven continues to show superior PFS versus Clb+O. Among patients treated with Ibr+Ven, benefit in PFS was particularly observed in patients with uIGHV who achieved uMRD at EOT+3 and in patients with mIGHV regardless of MRD status at EOT+3. Moreover, Ibr+Ven fixed-duration combination treatment continues to demonstrate an OS advantage versus chemoimmunotherapy in patients with previously untreated CLL.

Outcomes after CAR T Cells in Multiple Myeloma Patients with Extramedullary and Paramedullary Disease

Background: Extramedullary disease (EMD) is a poor prognostic factor for multiple myeloma patients even in the era of novel therapies, while patients with paramedullary disease (PMD) have historically fared better. We sought to characterize EMD and PMD in the peri-CAR T period, assess their effects on outcomes after CAR T, and evaluate the ability of CAR T-cell therapy to clear EMD. Methods: We retrospectively analyzed patients with relapsed/refractory multiple myeloma (RRMM) treated with CAR T-cell therapy in a clinical trial or with a commercially approved product at The Mount Sinai Hospital who had at least 3 months of follow-up. EMD was defined as the presence of soft tissue lesions not contiguous with bone and was quantified by measuring the sum of the product of the two longest perpendicular diameters (SPD) of each lesion. PMD was defined as the presence of soft tissue lesions contiguous with bone. Results: A total of 134 patients received CAR T-cell therapy for RRMM between April 2017 and February 2023 and were followed for a median of 18.6 months, with 59 patients treated with ciltacabtagene autoleucel, 52 with idecabtagene vicleucel, and 23 with other products on clinical trials. Thirty-four patients (25.4%) had EMD at baseline (EMD+), while patients without EMD were further subdivided into those with PMD (PMD-only, 25 patients, 18.7%) and those with neither EMD nor PMD (75 patients, 56.0%). Among patients with measurable EMD, median SPD was 11.15 cm 2 (range 0.25-200.10 cm 2). Patients were heavily pretreated with triple-class refractory status present in 94.1% of EMD+ patients, 96.0% of PMD-only patients, and 74.7% of patients with neither. Compared to patients with neither EMD nor PMD, PMD-only patients had similar PFS (HR 0.98, 95% CI 0.51-1.87) and OS (HR 1.34, 95% CI 0.48-3.76), while EMD+ patients exhibited significantly worse PFS (HR 1.87, 95% CI 1.13-3.09) and OS (HR 3.78, 95% CI 1.81-7.92). Overall response rates (ORR) were 76.5% in EMD+, 92.0% in PMD-only, and 88.0% in patients with neither. Among EMD+ patients, those with the highest tumor burdens (SPD ≥50 cm 2, n = 7) had ORR of 57.1% with no complete responses (3 PD, 3 PR, 1 VGPR). Conversely, EMD+ patients with SPD <50 cm 2 (n = 27) had 81.5% ORR and deeper responses (66.7% complete response). Of the 134 patients, 69 patients relapsed including 34 with EMD at relapse. Among the 34 patients with baseline EMD, 23 (67.6%) relapsed including 21 (61.8%) who relapsed with EMD. EMD was present in its prior location for 13 patients, while EMD cleared in prior locations and was present in new locations for 8 patients. Of 100 patients who had no EMD at baseline, only 13 (13.0%) relapsed with EMD. All patients with bulky EMD (SPD ≥50 cm 2) relapsed with EMD. Among the 34 patients with EMD at relapse, 28 were assessed for MRD status in the bone marrow at the time of relapse, of which 12 (42.9%) remained MRD negative by next generation flow (sensitivity 10 -5). EMD post-BCMA CAR T was biopsied and stained for BCMA in 7 relapsing patients, of which 6 were BCMA positive and 1 was BCMA negative. Conclusion: EMD is a well-recognized poor prognostic factor in multiple myeloma. In our single-center retrospective analysis, the presence of EMD but not PMD was associated with significantly worse PFS and OS following CAR T-cell therapy. EMD+ patients with SPD <50 cm 2 experienced high response rates and deep responses following CAR T-cell therapy (with two-thirds of patients clearing EMD), while patients with the highest extramedullary tumor burdens (SPD ≥50 cm 2) did not. This shows the ability of CAR T-cell therapy to benefit patients in this high-risk group when extramedullary tumor burden is lower. We contend that controlling extramedullary sites of disease prior to CAR T-cell therapy with optimal bridging chemotherapy and/or radiation therapy may be an effective strategy for improving outcomes. Half of patients relapsing after CAR T-cell therapy had EMD, and the majority of patients with baseline EMD ultimately relapsed with EMD despite having been radiographically EMD negative following CAR T treatment. Finally, 42.9% of patients relapsing with EMD after CAR T-cell therapy remained MRD negative in the marrow, showing bone marrow MRD does not adequately represent overall disease control post-CAR T.

Comparable Outcome after Busulfan- or Treosulfan-Based Conditioning Regimen in Children Above 4 Years of Age with ALL Undergoing Allogeneic HSCT. Results from the Prospective International Forum-Trial

Purpose: Total body irradiation (TBI) has proved to be the “gold standard” as part of the conditioning regimen before allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients with acute lymphoblastic leukemia (ALL). Its superiority over chemo-based conditioning was recently demonstrated in the prospective, international, randomized phase III study, which enrolled 417 patients beyond the age of 4 years transplanted for ALL in complete morphological remission (CR) from either matched sibling (MSD) or matched unrelated donor (MD) (Peters et al, JCO 2021, FORUM study; EudraCT: 2012-003032-22;ClinicalTrials.gov: NCT01949129). The use of either of the two protocol-prespecified chemo-conditioning regimens resulted in significantly worse EFS. Given the unavailability of TBI in some regions/centres and contraindications to TBI in individual patients, we here compare the outcomes of patients who received busulfan (BU) - based regimen vs of those who were given a treosulfan (TREO) - based conditioning in FORUM centres in both randomizing and non-randomizing countries in the years 2013-2018. Patients and methods: Patients ≤ 18 years at diagnosis (median age at HSCT 9.9 years, range 4-19.5), in CR pre-HSCT and with an MSD or MUD were assigned to myeloablative conditioning with fludarabine (FLU), thiotepa (THIO) and either BU or TREO according to country preference. Children transplanted from MSDs received cyclosporine A only as graft-versus-host disease (GvHD) prophylaxis, whereas recipients of MUD HSCT also received short-term methotrexate and anti-thymocyte globulin (ATG). Further details of the transplant procedure have been previously described (Peters C, et al. J Clin Oncol 2021). Results:In addition to the 193 patients from the randomizing countries, the FORUM trial included 115 additional children enrolled in countries where randomization could not occur (for legal or technical reasons). Overall, 180 vs. 128 patients received BU/THIO/FLU vs TREO/THIO/FLU, respectively. There were no differences about the patients' gender, age, and remission status and slight differences regarding donor, stem cell source and MRD status pre-transplant between the two cohorts of patients (see Table 1 for details). Patient's outcomes were updated as of February 20 th, 2023, and median follow-up was 4.2 years (range 0.3 - 9.1). There were neither differences between the 3-year overall survival (OS) (0.71±0.03 for BU/THIO/FLU vs 0.72±0.04 for TREO/THIO/FLU) nor event-free survival (EFS) (0.61±0.04 for BU/THIO/FLU vs 0.55±0.04 for TREO/THIO/FLU, p=NS). Three-year cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) were 0.31±0.03 and 0.08±0.02 following BU/THIO/FLU and 0.36±0.04 and 0.09±0.03 following TREO/THIO/FLU, respectively (p=NS). Only one case of secondary malignancy was observed in the TREO cohort and one case of fatal liver veno-occlusive disease (VOD) in the BU group. No statistical differences were observed regarding the cumulative incidence of both aGvHD and cGvHD between the two groups; 3-year GFRS was almost identical (0.42± 0.04 in the BU/THIO/FLU group and 0.43±0.04 in the TREO/THIO/FLU cohort). There were no differences in OS, EFS, CIR, NRM and GFRS in either CR1 or CR2 patients between the two conditioning regimens. Furthermore, there were no differences in outcomes between countries. Patients given BU/THIO/FLU had a faster leucocyte, neutrophil and platelet recovery as compared to those prepared with TREO/THIO/FLU. Conclusion: Comparable long-term outcomes were observed after BU/THIO/FLU or TREO/THIO/FLU in children with ALL undergoing allogeneic HSCT included in the FORUM trial. Therefore, either of the 2 regimens may be effectively and safely used worldwide in patients > 4 years having a contraindication to or treated in centres/countries unable to deliver TBI.

Multilayer Profiling of MRD in Patients with Relapsed/Refractory CLL Treated with Venetoclax-Based Regimens in a Real-World Setting

Background Clinical trials have shown that patients with relapsed/refractory chronic lymphocytic leukemia (RR-CLL) treated with venetoclax monotherapy (Ven) or venetoclax-rituximab (VenR) often achieve unmeasurable MRD (uMRD) in peripheral blood (57% of VenR-patients achieved uMRD in peripheral blood at the 12 months landmark by FCM and/or ASO-PCR in the RCT MURANO; Kater AP. et al. JCO 2019 1). uMRD is a strong prognostic factor for progression free survival (PFS) in RR-CLL treated with venetoclax, but the rate of uMRD has not been systematically validated in RR-CLL cohorts treated in the real-world setting. Venetoclax imposes a strong selective pressure on the MRD clone, but the magnitude of the genetic drift of MRD persisting under venetoclax has not been quantified or qualified. Resistance to venetoclax can be mediated by selection of BCL2 mutant clones, but it is unknown if they already emerge in persistent cells of the MRD when the disease is in remission. Methods We analyzed peripheral blood of Swiss patients enrolled in the VeRVe study (NCT03342144), a prospective non-interventional observational study assessing effectiveness, safety, and quality of life in real-world patients with RR-CLL treated with Ven or VenR according to local label. MRD was measured by 8-color multi-parametric flow cytometry (FCM) following the European Research Initiative on CLL (ERIC) guidelines (sensitivity 10 -4), by high throughput sequencing (Ig-HTS, clonoSEQ® Assay) on gDNA from PBMCs (sensitivity 10 -6) and by NGS LyV4.0 CAPP-Seq ctDNA Assay on plasma ctDNA (sensitivity 10 -3) at diagnosis and at 12 months of treatment. To overcome the limitations imposed by the small size of MRD under venetoclax treatment, we leveraged ctDNA for clonal evolution profiling and for the detection of BCL2 mutations. Tumor gDNA was extracted from pre-treatment CLL cells purified by flow cytometry. Germline gDNA was extracted from PB leukocytes collected at the time of best MRD remission. Results In total, 28 patients were recruited. At the time of the analysis, 7 patients went off study before the one-year landmark, 4 patients have not yet reached the one-year landmark, resulting in 17 patients (Ven=5, VenR=12) assessable at the one-year landmark [17 analyzed by FCM, 16 by CAPP-seq (1 ongoing) and 12 by Ig-HTS (5 ongoing; 3 could not be evaluated because they failed Ig-HTS QC)]. At the 12 months landmark, uMRD was achieved in 58% of the assessed cases by FCM, 56% by CAPP-seq and 33% by Ig-HTS. FCM and CAPP-seq concordantly defined the MRD status in 76% of cases with κ=0.49 (12% had measurable ctDNA despite uMRD by FCM and 12% lacked ctDNA despite having measurable MRD by FCM). FCM and Ig-HTS concordantly defined the MRD status in 67% of cases with κ=0.40 (33% had measurable MRD by Ig-HTS despite uMRD by FCM). All patients, who had measurable MRD by FCM and/or CAPP-seq, had measurable MRD by Ig-HTS, which instead detected measurable MRD in 11% of patients who scored negative by both FCM and CAPP-seq (κ=0.77). By CAPP-seq of gDNA from purified CLL cells collected before therapy, the most frequently mutated genes were TP53, IGLL5, BRAF, SF3B1, NXF1, and ZMYM3. At baseline the concordance in mutation recovery by CAPP-seq of gDNA from purified CLL and ctDNA from plasma was high (73%). Before therapy, BCL2 mutations were never detected in either gDNA from purified CLL cells, or in ctDNA. To overcome the limitations imposed to genomic profiling by the small size of MRD under Ven or VenR treatment, we leveraged ctDNA for tracking the acquisition of BCL2 mutations. A total of 5 longitudinal, post-treatment timepoints spanning up to two years of therapy were analyzed. No patients who had measurable ctDNA at the one-year landmark (n=16) acquired BCL2 mutations. Conclusions The rate of uMRD achievable by venetoclax-based therapy in RR-CLL as measured in this real-world prospective study is congruent with the rate observed in the randomized clinical study MURANO. Ig-HTS has the best diagnostic performance for MRD detection. BCL2 mutations are not detectable in ctDNA after one year of venetoclax-based treatment, confirming that time limited therapy has low risk of selecting resistance. 1.) Kater AP. et al. Fixed Duration of Venetoclax-Rituximab in Relapsed/Refractory Chronic Lymphocytic Leukemia Eradicates Minimal Residual Disease and Prolongs Survival: Post-Treatment Follow-Up of the MURANO Phase III Study. JCO 2019, 7(4):269-277

EP07.05-10 Efficacy and Safety of Aumolertinib in Stage IB-IIIA NSCLC after R0 Resection and the Correlation between Efficacy and Postoperative MRD Status

EP07.05-10 Efficacy and Safety of Aumolertinib in Stage IB-IIIA NSCLC after R0 Resection and the Correlation between Efficacy and Postoperative MRD Status

Prospective study to assess treatment response and predict patient prognosis by a blood-based multi-omics assay in lymphoma patients.

116 Background: Lymphoma represents a diverse group of cancer that arises from clonal proliferation of lymphocytes. Clinical existing imaging and biomarkers do not reliably predict treatment response across diverse lymphoma subtypes and treatment regimens. Only rare data show circulating tumor DNA (ctDNA) testing may perform as a good predictive biomarker for assessment of therapeutic response. We conducted a prospective study to assess treatment response and predict patient prognosis via our multi-omics assay (SeekInClarity) in lymphoma patients. Methods: SeekInClarity assay utilized common 7 protein tumor markers (PTMs) and cancer genomic hallmarks: copy number aberration (CNA) and fragment size (FS), which were analyzed by shallow whole genome sequencing, to calculate the molecular tumor burden (MTB) score. 8ml peripheral blood samples were collected from patients before and after every 2 cycles of treatment respectively, meanwhile, samples from a part of patients after 1 cycle of treatment were also collected. Results: Before treatment, 95 out of 133 patients (71.4%) were succeeded in detecting cancer signals with higher MTB scores (defined as baseline+). The proportion of patients with baseline+ was higher in patients with higher tumor stages. After 2 cycles of treatment, 39 out of 112 patients had a higher MTB score (defined as MRD+). The proportion of patients with progression in MRD+ group was significantly higher than that in MRD- group (p<0.001). Meanwhile, MRD+ patients had a worse PFS than MRD- patients (p <0.0001, HR: 26.4, 95% CI:8.7~80.3), regardless of tumor stages, lymphoma subtypes and treatment regimens. Among baseline+ patients, after 2 cycles of treatment the patients with MTB score decrease had a better PFS than that with MTB score increase (P<0.001, HR: 7.5 95% CI:0.7~76.7). Among the baseline- group, patients who remained negative after treatment had extremely well PFS (100% PFS). As for the patients after 1 cycle of treatment, MTB value has a good concordance with that after 2 cycles of treatment which demonstrated a lead time in monitoring treatment response. 54 patients with longitudinal monitoring samples, 9(16.7%) patients were always MRD- during the treatment, who had the best PFS (100% PFS), regardless of baseline status. 11 out of 54 patients with always MRD+ had the worst PFS (p < 0.05). Conclusions: This study demonstrates the clinical utility of multidimensional blood-based SeekInClarity assay in pan-cancer/pan-indication treatment response assessment and patient prognosis. After treatment, the dynamic change of MTB score and MRD status were independently associated with patient’s PFS, which indicated both could be used as biomarkers to predict the effectiveness of treatment. Compared with clinical image evaluation after 2 cycles of treatment, SeekInClarity test after 1 cycle of treatment is sufficient to assess treatment response.

Fixed-duration ibrutinib + venetoclax for first-line treatment of chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL): 4-y follow-up from the FD cohort of the phase 2 CAPTIVATE study.

7535 Background: CAPTIVATE (PCYC-1142) is a multicenter phase 2 study of first-line ibrutinib (I) + venetoclax (V) in CLL/SLL. Follow-up results from the fixed duration (FD) cohort showed 3-y PFS rate of 88% overall and rates ≥80% in patients (pts) with high-risk features (Wierda, ASCO 2022). Here we present updated results from the FD cohort with 4-y follow-up. Methods: Pts aged ≤70 y with previously untreated CLL/SLL received 3 cycles of I then 12 cycles of I+V (I 420 mg/d orally; V ramp-up to 400 mg/d orally). Responses were investigator assessed per iwCLL 2008 criteria. Undetectable minimal residual disease (uMRD; <10‒4) was assessed by 8-color flow cytometry. Results: 159 pts were enrolled, including pts with high-risk features of unmutated IGHV (uIGHV) (56%) or del(17p) and/or TP53 mutation (17%). Median time on study was 50 mo (range 1‒53). At 4 y of follow-up, the best CR rate was 58% and ORR was unchanged at 96%. At 4 y, PFS rate was 79% (95% CI 71‒84) and OS rate was 98% (95% CI 94–99). 4 y PFS rates were numerically lower in pts with uIGHV (73%) or del(17p) and/or TP53 mutation (63%), while OS rates remained consistently high (Table). 4 y PFS rates by MRD status 3 mo after stopping treatment (EOT+3) were significantly higher overall in pts with uMRD vs detectable MRD (dMRD) in PB (90% vs. 66%, Table); this difference was minimal at 24 mo (100% vs 91%). Median TTNT was not reached overall (range 1–53 mo); the 4 y rate of freedom from next treatment was 84% (95% CI 77–89). Second malignancies continue to be collected off treatment; 1 AE of prostate cancer occurred during this y of follow-up. To date, 19 pts with PD after completing fixed duration I+V in either the FD cohort or MRD cohort placebo arm initiated retreatment with I. Responses in 17 pts with available data were 1 CR, 13 PR, and 1 each PR with lymphocytosis, SD, and PD. Median time on retreatment was 11 mo (range 0–39). The most common AEs (≥10%) with retreatment were diarrhea (n=3), COVID-19 (n=3), and anemia (n=2). In addition, 4 pts have started I+V retreatment to date. Conclusions: Results of the CAPTIVATE study support I+V as an all-oral, once-daily fixed-duration regimen for previously untreated pts with CLL/SLL. With 4 y follow-up, fixed-duration I+V continues to provide deep, durable remissions with clinically meaningful PFS and time off treatment, including in pts with high-risk disease features. New safety findings off-treatment were expectedly negligible, highlighting the benefits of a fixed duration regimen. Promising responses were observed upon retreatment with I in progressing pts. Clinical trial information: NCT02910583 . [Table: see text]