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Abstract Introduction: Brexu-cel is a highly effective treatment for R/R B-ALL, with complete responses achieved in 71% of patients (pts) treated in the pivotal ZUMA-3 trial. Patients with B-ALL with high-risk (HR) genetics are known to have inferior outcomes with chemotherapy, but little is known about the influence of HR ALL genetics on responses to chimeric antigen receptor (CAR)-T in adults. In this study, we assessed the impact of HR ALL genetics on outcomes in a large cohort of adult patients treated with brexu-cel for R/R Philadelphia chromosome (Ph)-negative B-ALL. Methods: Patient characteristics and outcomes were obtained from the Real-World Outcomes Collaborative of CAR-T in Adult ALL (ROCCA) database which includes data from 40 U.S. centers. NCCN guidelines (NCCN Guidelines in Oncology, ALL v2.2025) were used to define HR B-ALL genetics; lack of HR genetics was defined as standard-risk (SR). The primary outcome was event-free survival (EFS), defined as lack of response, disease progression, or death from any cause. Secondary outcomes were overall survival (OS), relapse free survival (RFS) and response rates including complete response (CR), CR incomplete count recovery (CRi), measurable residual disease negative CR (MRD-) by flow or NGS and progressive disease (PD). Multivariable models were adjusted for age, pre-infusion blast percentage, prior allo-HCT, and post CAR-T allo-HCT (modeled as a time-varying covariate). Results: The cohort included 286 pts: 169 with HR and 117 with SR B-ALL. The HR cohort included TP53m (n=24, 14%), KMT2Ar (n=16, 9%), CRLF2r (n=65, 39%) and other HR genetics such as JAK2 and other Ph-like, IKZF1, complex cytogenetics (n=64, 38%). Relative to SR pts, HR pts were more commonly Hispanic (50% vs 28%). HR and SR pts had similar disease burden pre-apheresis (>5% blasts: 58% vs 53%), prior blinatumomab (60% vs 58%), prior inotuzumab (42% vs 46%), and prior allo HCT (27% vs 37%). The presence of CNS disease (11% HR vs 12% SR) and extramedullary disease (EMD, 22% HR vs 29% SR) at apheresis was also similar. CR/CRi was achieved in 90.5% of evaluable HR pts (n=147) and 90.2% of evaluable SR pts (n=102); MRD- rates were also similar between HR and SR pts at 78.9% and 78.2% respectively. In unadjusted analyses, EFS did not significantly differ between HR pts (median 9.6 mos; 1-yr: 46%, 95% CI 38%-54%) and SR pts (median 11.6 mos; 1-yr: 48%, 95% CI 38%- 58%). Median RFS (HR: 12.2 mos, SR: 13.3 mos) and median OS (HR: 22.4 mos, SR: 21.0 mos) were also similar. Multivariable models demonstrated no significant associations between HR B-ALL and EFS (HR 1.09, 95% CI 0.73-1.63), RFS (HR 1.13, 95% CI 0.71-1.80), or OS (HR 0.96, 95% CI 0.62- 1.48) relative to SR ALL. 28% of HR patients and 21% of SR patients underwent consolidative allo-HCT. Among the HR subgroup, CR/CRi rate was lowest in KMT2Ar (71%) relative to TP53m (95%), CRLF2r (95%), and other HR genetics (89%). The median EFS was lowest in KMT2Ar (4.1 mos), followed by TP53m (6.9 mos), CRLF2r (11.6 mos), and other HR (11.1 mos). Median OS was also lowest in KMT2Ar (6.8 mos) vs 22.4 mos in TP53m and not reached in CRLF2r or other HR. PD was highest in KMT2Ar pts (29%), as compared to 11% HR other, 10% SR, and 5% TP53 and CRLF2r. The rate of relapse among those that achieved CR across the groups was similar and ranged between 28% -40%. Rates of CD19 negative relapse were similar between all subgroups (13%-15%), however 21% of KMT2A pts underwent myeloid transformation as compared 0% for TP53 and CRLF2 pts, and 2% among other HR and SR pts. 25% of KMT2Ar patients underwent consolidative allo-HCT as compared to 32% CRLF2 pts, 29% TP53 pts, 25% other HR pts and 21% SR pts. Multivariable models evaluating the different genomic subgroups demonstrated that relative to SR B-ALL, only KMT2Ar was associated with inferior OS (HR 3.17, 95% CI 1.53-6.58, p=0020). No associations were seen between HR subgroups and EFS. Conclusion: To our knowledge, this analysis represents the largest examination of adult B-ALL recipients of CAR-T assessed by genomic risk group. We found that response rates and survival outcomes following brexu-cel were similar among HR and SR B-ALL pts, including pts with TP53m and CRLF2r. However, pts with KMT2Ar had lower response rates and dismal EFS and OS, with higher rates of PD and myeloid transformation at relapse, suggesting that alternative strategies are necessary to improve outcomes for patients with R/R KMT2Ar B-ALL.

Abstract The incidence of venous thromboembolism (VTE) in patients with acute lymphoblastic leukemia (ALL) receiving asparaginase-based induction is high despite primary thromboprophylaxis. Our aim was to derive and externally validate a VTE risk prediction model in patients with ALL receiving asparaginase-based induction. We conducted a multicenter retrospective cohort study of patients (aged ≥18 years) with newly diagnosed ALL receiving asparaginase-based induction. The derivation and external validation cohorts included 306 and 94 patients, respectively. Primary outcome was VTE at any site. A cause-specific Cox proportional hazards model stratified by thromboprophylaxis and center was performed to identify VTE risk factors in the derivation cohort. A risk prediction model for VTE at 30 days was derived using variables with P value < .05 in the multivariable model and was tested in the validation cohort. VTE risk factors on multivariable analysis in the derivation cohort included D-dimer ≥1 μg fibrinogen equivalent unit per mL (hazard ratio [HR], 2.64; 95% confidence interval [CI], 1.07-6.5) and hemoglobin (HR for each 1 g/dL increment, 1.19; 95% CI, 1.06-1.34) at ALL diagnosis. A VTE risk score based on these variables distinguished between a 4% (95% CI, 0.72-12) and 20% (95% CI, 14-27) 30-day cumulative incidence of VTE in the derivation cohort, with similar findings in the validation cohort (area under the curve, 0.56). The negative predictive value for VTE at 30 days was 96% and 93% in the derivation and validation cohorts, respectively, and the positive predictive value was 20% in both. We derived and validated a model using D-dimer and hemoglobin, which stratifies VTE risk in patients with ALL receiving asparaginase-based induction.

Adolescents and young adults (AYA; ages 15–39) with acute leukemia have significant unmet supportive care needs. This pilot study integrated same-day palliative care (PC) into an AYA leukemia clinic, measuring symptom burden (SB) with validated symptom assessment tools at baseline, 3, and 6 months. Among 31 patients, moderate-severe symptoms included tiredness, anxiety, and poor appetite. AYAs experienced high SB and psychological distress, regardless of care phase or sociodemographics. With PC integration, tiredness and depression improved significantly; no symptoms worsened. Half of the PC visits led to management changes. Early integration of symptom-focused PC was feasible, value-adding, and well-received by patients.

PURPOSE Older patients with ALL receiving conventional chemotherapy have poor survival due to toxic death and relapse. We hypothesized that a chemotherapy-free, targeted regimen using the anti-CD22 antibody-calicheamicin conjugate inotuzumab ozogamicin followed by the bispecific anti-CD19/CD3 T-cell engager blinatumomab would reduce toxic death and yield high rates of prolonged remission and survival. METHODS Eligible patients were age 60 years and older with untreated, Philadelphia chromosome (Ph)–negative, CD22-positive, B-cell ALL. Patients received up to two cycles of inotuzumab ozogamicin followed by four or five cycles of blinatumomab with intrathecal methotrexate CNS prophylaxis. The primary end point was 1-year event-free survival (EFS). RESULTS The 33 eligible patients had a median age of 71 years (range, 60-84) and a median CD22 expression of 92% (range, 21%-100%). Eight (24%) had previous chemotherapy or radiation for other cancers, six for multiple myeloma. The composite complete remission rate was 85% after two cycles of inotuzumab ozogamicin and 97% by the end of two cycles of blinatumomab. At a median follow-up of 30 months, the 1-year EFS and overall survival were 75% (95% CI, 61 to 92) and 85% (95% CI, 73 to 98), respectively. EFS was shorter with lower CD22 expression or detectable measurable residual disease at any time point. CONCLUSION Inotuzumab ozogamicin then blinatumomab without maintenance chemotherapy in older patients with untreated, Ph-negative, CD22-positive, B-cell ALL yields a high remission rate and excellent EFS. Given the lack of standard, safe, and effective therapies in this population, the regimen should be considered a standard treatment option.

Abstract Inotuzumab ozogamicin (InO) is an antibody-calicheamicin conjugate with high efficacy in lymphoid malignancies. It targets the B-cell surface protein CD22, which is expressed in most B-cell acute lymphoblastic leukemia (B-ALL) cases, albeit with variable intensity. However, factors governing CD22 expression and thus leukemia sensitivity to InO remain incompletely understood. Using multiomic characterization of 196 human B-ALL samples, coupled with ex vivo InO sensitivity profiling, we showed that early leukemia differentiation arrest at the pre–pro-B stage is associated with resistance to InO. Screening of 1639 transcription factor genes identified early B-cell factor 1 (EBF1) as a key regulator of CD22 expression (false discovery rate of 7.1 × 10−4). When comparing the assay for transposase-accessible chromatin with sequencing profiling results of the most InO-sensitive and -resistant cases (50% lethal concentration <10th vs >90th percentile, n = 18), the binding motif for EBF1 was strikingly enriched in regions with differential open chromatin status (P = 8 × 10−174). CRISPR interference targeting EBF1 binding sites at the CD22 locus led to an ∼50-fold reduction in cell surface CD22 expression and, consequently, an ∼22-fold increase in InO resistance in ALL cell lines. Interestingly, within BCR::ABL1 ALL, we observed intrasubtype heterogeneity linked to EBF1 transcriptional downregulation (P = 1.1 × 10−15) and/or somatic alteration (P = .004), which led to reduced CD22 expression (P = 8.3 × 10−11) and ex vivo and in vivo resistance to InO. Collectively, these findings point to the direct impact of EBF1 on CD22 expression during B-cell development, which, in turn, contributes to interpatient variability in InO response, even within the same subtype of B-ALL.

AbstractBackgroundAcute lymphoblastic leukemia (ALL) in adults is aggressive, with long‐term outcomes impacted by treatment resistance and toxicity. CD52 is expressed in most cases of B‐ and T‐lineage ALL. Alemtuzumab, a humanized immunoglobulin G1 monoclonal antibody that targets CD52, was identified as a potential agent to improve treatment efficacy without increasing toxicity.MethodsIn this phase 1/2 study (Cancer and Leukemia Group B [CALGB] 10102, NCT00061945), a course of single‐agent alemtuzumab was intercalated into CALGB 19802 backbone chemotherapy after the third course of intensive chemotherapy in those who were CD52+ at diagnosis. Phase 1 tested three dose levels of subcutaneous alemtuzumab (10, 20, and 30 mg 3 times weekly for 4 weeks/12 doses) and demonstrated that 30 mg was tolerable. Phase 2 established feasibility.ResultsThe study enrolled 295 evaluable patients (115 in phase 1, 180 in phase 2); 206 (69.8%) were CD52+. Among evaluable CD52+ patients, 43.7% (90/206) completed the first three treatment modules; 97.8% (88 of 90) were treated with alemtuzumab. Alemtuzumab was associated with cytomegalovirus viremia, which occurred in 23.3% (14 of 60) of patients during and 29.2% (19 of 65) after alemtuzumab treatment. With a median follow‐up of 101.2 months, median overall survival (OS) was 26.3 months (3‐year rate, 44%; 5‐year rate, 36%; 10‐year rate, 31%). Landmark analysis at the start of the fourth course of treatment demonstrated no difference in OS or disease‐free survival between patients who did and who did not receive alemtuzumab.ConclusionAlemtuzumab was feasible to administer in adults with ALL receiving intensive chemotherapy, but was without evidence of benefit.

Abstract Inotuzumab ozogamicin (InO) is an antibody-calicheamicin conjugate with striking efficacy in B-cell acute lymphoblastic leukemia (B-ALL). However, there is wide interpatient variability in treatment response, and the genetic basis of this variation remains largely unknown. Using a genome-wide CRISPR screen, we discovered that the loss of DNA nucleotidylexotransferase (DNTT) is a primary driver of InO resistance. Mechanistically, the downregulation of DNTT attenuated InO–induced DNA damage response, cell cycle arrest, and mitochondrial apoptotic priming, thereby ultimately leading to leukemia resistance to InO. Ex vivo leukemia InO sensitivity was highly associated with DNTT expression in ALL blasts with substantial intraleukemia heterogeneity as revealed by single-cell RNA sequencing. Among patients with B-ALL enrolled in the Children's Oncology Group trial AALL1621, we observed consistent DNTT downregulation in residual blasts following InO treatment. The selection of DNTT-low blasts by InO therapy was also recapitulated in vivo using patient-derived xenograft models. Collectively, our data indicate that DNTT is a key regulator of calicheamicin response in leukemia and thus a potential biomarker for individualizing InO therapy in B-ALL.

Background: The BeatAML Master Trial (BAMT) began in 2016 with a goal of determining the feasibility of a precision-medicine approach in treating acute myeloid leukemia (AML) in older adults ≥ 60 years of age where outcomes are poor. At the time, standard of care (SOC) for older patients with AML was intensive 7+3 chemotherapy (cytarabine + daunorubicin) if fit and hypomethylating agents (HMA: azacitidine or decitabine) if unfit. Besides confirming the feasibility, the early results (2019) from the Master Trial suggested that patients who received therapy on one of the sub-studies had a lower early death rate and superior overall survival compared to patients receiving off-protocol SOC, which was primarily single-agent HMA at the time. Since then, the 2019 approval of venetoclax (ven) + azacitidine for older unfit AML patients has been transformative and emerged as the SOC. Using data from the BAMT from 2016-2024, we suggest that knowing the comprehensive genomic profile of AML at the time of diagnosis is still beneficial in determining therapy that would lead to the optimal outcome and that development of targeted therapies and combination regimens with ven/HMA is still needed. Methods: This is a retrospective analysis of 1096 patients who consented and enrolled on the BAMT (NCT03013998) from Nov 2016 through Jun 2024. Patients ≥ 60 years with newly diagnosed AML were included. Patients underwent therapy on a BeatAML sub-study based on their genetics (N=433) or treatment off-protocol (N=663). We divided the patients according to what therapy they received: (1) Non-Intensive (Off-Protocol, N=121), (2) Ven/HMA (Off-Protocol, N=234), (3) Non-Intensive (Sub-Study, N=407), (4) Intensive (Sub-Study, N=26), and (5) Intensive (Off-Protocol, N=155). 94 patients received no treatment and 59 were unknown. Non-intensive therapies included primarily targeted agents or non-ven combinations. We analyzed baseline characteristics and demographics, overall survival (OS), and the impact of allogenic stem cell transplant (SCT). OS, using Kaplan-Meier method, was measured from the start of therapy to all-cause death, censoring patients at last follow-up. Results: Characteristics and demographics were similar between Groups 1, 2 and 3. Group 4 and 5 were treated with intensive chemotherapy and their characteristics are reflective of younger/fit patients appropriate for the intensive regimen. Groups 4 and 5 also had the longest median OS (mOS) of 40.2 months (95% CI: 13.9-not reached (NR)) and 42.3 months (95% CI: 25.1-NR) respectively. Group 3, which included patients treated with a non-intensive, targeted therapy on a sub-study, had an mOS of 14.0 months (95% CI: 12.3-16.7), which was similar to Group 2, treated with Ven/HMA, that had an mOS of 13.2 months (95% CI: 10.9-16.3). Lastly, patients in Group 1, who were treated primarily with HMA monotherapy, did poorly in comparison, with an mOS of 6.0 months (95% CI: 3.3-10.1). Additionally, we looked at the cumulative incidence rate (CIR) of SCT. The CIR in 12 months of Group 1 was 9.8% (95% CI: 6.9-13.4), Group 2: 5.4% (95% CI: 2.2-10.7), Group 3 and 4 combined: 35.0% (95% CI: 628.1-42.1), and Group 5: 13.1% (95% CI: 6.9-13.4). In a multi-variable analysis, after adjusting for typical favorable risk factors like NPM1 mutations and core binding factor, SCT was highly significant (p<0.0001) in improving OS with a hazard ratio of 0.23 (95% CI: 0.16-0.32), and Group 3 performed similarly to Group 2 (p=0.20). Conclusions: First, our results suggest that it is clinically relevant to correctly identify whether an intensive chemotherapy, targeted-therapy, or ven/HMA regimen is best suited for older AML patients, for which a precision-medicine trial is ideal for. Secondly, in this group of patients, our results show that patients treated with a non-intensive targeted therapy (Group 3) has a similar mOS to those treated with ven/HMA (Group 2). Especially after controlling for patient characteristics, patients in Group 2 performed similar to those in Group 3 (p=0.20). Patients in Group 3 were treated on Beat AML sub-studies which included targeted therapy alone or with non-venetoclax combinations, which is a strong rationale for continued development of targeted agents to optimize toxicity and quality of life with similar survival. Lastly, this data also supports the need to improve the ven/HMA SOC by developing combination regimens with targeted agents to further improve outcomes.

Background: Mutations of isocitrate dehydrogenase (IDH) are recurrent in acute myeloid leukemia (AML) and the prevalence increases with age. The prognostic impact of IDH1 and IDH2 mutations remains controversial. IDH inhibitors are small molecules that bind within the IDH enzymatic active site, blocking aberrant 2-hydroxyglutarate production and inducing myeloid differentiation. While they can lead to differentiation syndrome, they generally have a more favorable side-effect profile, making them an attractive option for older patients. We aimed to describe the prevalence and prognostic impact of IDH mutations in newly diagnosed (ND) AML patients ≥ 60 years in a large cohort of patients treated on a Leukemia and Lymphoma Society-sponsored trial. Methods: We performed a retrospective observational analysis including patients ≥ 60 years with ND AML who were enrolled on the Beat AML clinical trial (NCT03013998) before May 10, 2023. Patients were treated with a variety of treatment regimens. Cytogenetic analysis and next-generation sequencing (FoundationOne®Heme) were obtained. Mutations were considered present at any detectable VAF. Cox proportional hazard models were used to describe the relative risk of each variable on death over time from the date of trial inclusion. Results: A total of 1023 patients with ND AML were identified. Patients had a median age of 72 (range 60-92) years and the majority were non-Hispanic White (83.2%), and male (57.6%). Ninety-nine (9.7%) patients were IDH1MUT, 193 (18.9%) patients were IDH2MUT including 10 (1.0%) patients with a co-occurring IDH1 and IDH2 gene mutations. Both IDH1MUT and IDH2MUT were associated with 2022 ELN favorable-risk (26.3% and 22.3% for IDH1 and IDH2 respectively, vs 15.5% overall (P<0.001)). IDH1MUT significantly co-occurred with DNMT3AMUT (42.4%), NPM1MUT (44.4%) and less frequently with TP53MUT (10.1%) (P<0.001 for all). IDH2MUT was associated with DNMT3AMUT (35.8%), NPM1MUT (31.1%), SRSF2MUT (38.3%), and less frequently with TET2MUT (6.7%) and TP53MUT (9.3%) (P<0.001 for all). Normal karyotype was higher in IDH1MUT (P<0.001) and IDH2MUT (P<0.001), whereas complex karyotype (P<0.001 for both) and core-binding factor AML (P=0.047, P=0.015) were lower in IDH1MUT and IDH2MUT. To evaluate the impact of IDH mutations in patients ≥ 60 years, we focused on patients evaluable for outcome treated with lower-intensity therapy (LIT) (N=674), and intensive chemotherapy (IC) (N=178), separately. Among the LIT treated patients, 96 patients received treatment with an IDH inhibitor, and 237 patients received a hypomethylating agent (HMA) plus venetoclax. For patients treated with LIT, the hazard ratios (HRs) of death over time were 0.58 [95% CI 0.47-0.72; P<0.002], 0.81 [95% CI 0.59-1.13; P=0.214] and 0.56 [95% CI 0.44-0.72; P<0.001] for IDHMUT, IDH1MUT, IDH2MUT respectively. Among patients receiving IC, the HRs were 1.05 [95% CI 0.68-1.69; P=0.777], 0.70 [95% CI 0.31-1.61; P=0.406] and 1.27 [95% CI 0.77-2.1; P=0.352] for IDHMUT, IDH1MUT, and IDH2MUT respectively. The HR of death for IDH1MUT patients treated with LIT with the addition of an IDH1 inhibitor (N=24) was significantly lower (HR 0.47 [95% CI 0.24-0.92; P=0.027] vs IDH1MUT patients treated without an IDH1 inhibitor, while an IDH2 inhibitor did not change survivial outcomes in patients with IDH2MUT (N=71). Discussion: To our knowledge this is the largest retrospective study characterizing the prevalence of IDH mutations in patients ≥ 60 years with AML. We demonstrated that IDH mutations were detected in ~27% of older patients with AML. Although there could have been selection bias as the Beat AML study had separate IDHMUT study arms, these findings are concordant with other studies showing an increase in frequency of IDH mutations with age. IDH2MUT was associated with a lower HR of death among patients treated with LIT, which was not seen in patients receiving IC. The high prevalence of IDH mutations suggests that IDH inhibitors used as single agents or in combination with lower-intensity therapies are an important class of drugs for this older patient population as they are generally well tolerated, that need further investigation.

Introduction: Brexucabtagene autoleucel (brexu cel) is a CD19-targeted chimeric antigen receptor (CAR) T cell therapy approved for the treatment of adults with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL). Some patients (pts) proceed with a consolidative allogeneic hematopoietic cell transplant (HCT) after breux cel. We do not know which pts can safely avoid a consolidative HCT and its associated morbidity. Methods: We conducted a retrospective cohort study utilizing the Real-World Outcomes Collaborative of CAR-T in Adult ALL (ROCCA) dataset. ROCCA is a registry of brexu cel pts in 32 centers in North America. We defined complete remission (CR) as < 5% blasts in the bone marrow and no central nervous system (CNS) or extramedullary (EM) disease on or around D28 after brexu cel. We defined measurable residual disease negative (MRD-) CR as CR and no abnormal blasts in the bone marrow by multiparameter flow cytometry, quantitative polymerase chain reaction, ClonoSeq next generation sequencing (NGS), or other sequencing modalities with lower sensitivity. ClonoSeq NGS has a sensitivity of 10-6, while the other modalities have a sensitivity of at least 10-4. We defined progression free survival (PFS) as the time from CAR-T infusion to relapse or death, censored at the date of last follow-up. Statistical analyses were performed in R. Univariable Cox proportional hazards regression analyses were performed to determine the association of pre-specified variables with PFS. Variables known to be associated with CAR T outcomes in ALL were entered into a multivariable model. HCT was incorporated as a time-varying covariate. Results: During the study period, 281 pts were infused with brexu cel. We focused our analysis on 172 (61%) pts with confirmed MRD- CR on D28, as that is the group with clinical equipoise regarding maintenance strategy. 38 (22%) of those pts received a consolidative HCT, 30 (17%) received another form of maintenance therapy (primarily tyrosine kinase inhibitors for Philadelphia (Ph)-chromosome positive ALL), and 104 (60%) pts received no maintenance therapy. Pts who underwent consolidative HCT were younger (median age 35 years) than those who received no maintenance (42y) (p = 0.023) and were less likely to have a history of prior HCT (13% vs. 47%, p < 0.001). No differences were observed with respect to sex, TP53 mutation status, prior inotuzumab (ino) or blinatumomab (blina) exposure, disease burden prior to CAR, or development of any cytokine release syndrome (CRS) or any neurotoxicity with brexu cel. We performed univariable Cox proportional hazard regression analyses among pts in MRD- CR on D28, excluding those who received other maintenance therapy besides HCT; the median follow up was 8.1 months. In univariable analyses, D28 MRD negativity by ClonoSeq NGS (versus MRD negativity by other, less sensitive methods), development of CRS, and pre-CAR BM blasts < 5% were associated with improved PFS; prior ino exposure was negatively associated with PFS (p < 0.05). Age, sex, Ph status, TP53 status, and neurotoxicity development were not associated with PFS. In a multivariable model incorporating ALL type, prior HCT, prior ino/blina, and pre-CAR blast burden, as well as consolidative HCT as a time-varying covariate, only MRD negativity by ClonoSeq NGS with at least 10-6 sensitivity retained statistical significance (PFS hazard ratio 0.34, 95% confidence interval (CI) 0.15-0.77, p = 0.005). Pts who were MRD- by ClonoSeq NGS on D28 and received no maintenance had favorable 6m PFS of 76% (95% CI: 59-98%) and OS of 100% with a median follow up of 6.3 months in this subgroup. Among those in MRD- CR by NGS, HCT as a time-varying covariate was not associated with improved PFS (HR 0.6, p = 0.6). Conclusions: In a large real-world cohort of adults with R/R B-ALL infused with brexu cel, we identified practice variation regarding the use of consolidative HCT. Among brexu cel recipients who entered an MRD- CR, we identified ClonoSeq NGS MRD negativity as a novel predictive factor of favorable oncologic outcomes, even without a consolidative HCT. Similar results have been obtained in pediatric ALL patietns ftreated with 41BB-based tisagenleucleucel (Pulsipher et al., Blood Cancer Discovery 2022). Longer follow-up is needed to validate the safety of omitting consolidative HCT in such pts, but these results encourage the potential for definitive therapy with brexu cel when D28 ClonoSeq NGS MRD is negative.