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Abstract Background: Isocitrate dehydrogenase (IDH) mutations are frequently implicated in the development of acute myeloid leukemia (AML). In a recent study (Salman MY, Blood Adv 2025), it was reported that IDH2 mutation subtypes, R140 and R172, may respond differently to intensive chemotherapy. In this study, we evaluated mid-cycle and end-of-cycle bone marrow blast responses in AML patients with IDH2 R140, IDH2 R172, and IDH1 R132 mutations, aiming to determine whether these subtypes exhibit different response dynamics. Methods: We reviewed the charts of AML patients diagnosed at Mayo Clinic, Rochester, between the years 2016 - 2023 that had available next generation sequencing (NGS) data. Institutional review board approval was obtained. All data were recorded at the time of AML diagnosis. Patients without molecular data or not treated with intensive chemotherapy (7+3 or CPX-351) were excluded from this study. Bone marrow blast percentages were assessed at mid-induction (days 14-21) and end of cycle (counts recovery). Blast clearance dynamics and complete remission rates were compared across IDH mutation subgroups and correlated with outcomes. GraphPad Prism 10.0.0 was used for statistical analysis. Results: Out of 381 AML patients, 31 had IDH2 mutations (23 with R140 and 8 with R172), and 8 had IDH1 mutations (all R132). Among patients with IDH2 mutations, those with R172 had numerically higher median mid-cycle bone marrow blast percentage compared to R140 (10% vs. 4%, p = 0.37). There was no significant difference in mid-cycle blast percentages between patients with IDH1 and IDH2 mutations (4.5% vs. 4%, p = 0.8). At mid-cycle, 68% of patients with IDH2 R140 had blast counts <5%, compared to 38% of those with IDH2 R172, suggesting a trend for faster mid-cycle clearance in the R140 group, though not statistically significant (OR 3.57, p = 0.2). In a broader comparison, 60% of IDH2-mutated patients and 50% of IDH1-mutated patients achieved blast clearance (blasts <5%) at mid-cycle, though not statistically significant (p = 0.7). At the end of the induction, patients with IDH2 R140 had significantly lower median bone marrow blast percentages compared to those with R172mutations (2% vs. 4%, p = 0.01). Similarly, patients with IDH1 mutations showed low blast counts compared to the IDH2 group (1.5% vs. 3%, p = 0.1). A higher proportion of IDH2 R140 patients achieved blast clearance compared to those with R172 mutations (100% vs. 75%, p = 0.06), while proportion of patients who achieved blast clearance were similar between IDH1 and IDH2 patients (87.5% vs 93.1%, P = 0.5). Analysis of overall complete remission rates (including both complete remission [CR] and CR with incomplete hematologic recovery [CRi]) within the IDH2-mutated group showed a higher rate in patients with the R140 mutation compared to those with R172 (87% vs. 75%), though the difference was not statistically significant (p = 0.5). When comparing IDH1- and IDH2-mutated patients, overall complete remission rates were 75% and 84%, respectively, with no significant difference observed (p = 0.6). Kaplan–Meier analysis of time to end-of-induction blast clearance revealed no statistically significant difference between IDH2 R140 and R172 patients (median time to clearance: 31 vs. 37 days, p = 0.3). Similarly, no difference was observed between IDH1 and IDH2-mutated patients (33 vs. 31 days, p = 0.9). Overall survival analyses showed no significant difference between IDH2 R140 and R172 groups (median 66.8 months vs not reached, P = 0.4). Likewise, no difference was observed between IDH1 and IDH2 patients (44.4 months vs not reached, P = 0.7), indicating similar overall survival across mutation subtypes. Conclusion: IDH2-R140 was associated with more effective blast cytoreduction following intensive induction compared to IDH2-R172. Although not statistically significant, IDH2 R172consistently showed trends toward higher blast percentages, delayed response, and lower overall complete remission rates. These findings align with the recent study reporting significantly slower blast reduction and delayed response in R172-mutated AML. Also, no significant differences were found between IDH1- and IDH2-mutated patients in terms of response kinetics or overall survival. Together, these findings highlight potential biological differences among IDH mutation subtypes that may impact treatment response and require further investigation in larger prospective cohorts.

Abstract Background: Population registries and the Alliance co-operative group database have highlighted racial disparities in AML survival attributed to differential prevalence and impact of oncogenic drivers on disease biology. However, the small number of Black patients with well-annotated genomic profiles limits the validity of these findings. The current study leverages ECOG-ACRIN cytogenetic and outcomes data from newly diagnosed adult AML patients treated on intensive chemotherapy-based clinical trials over three decades. Methods: Self-reported race was categorized as White, Black or Other. Descriptive statistics were used to summarize baseline characteristics using the Wilcoxon rank-sum and Fisher's exact tests. Multivariable Cox proportional hazards regression models evaluated the association between race and survival outcomes adjusting for age, hemoglobin, platelet count, white blood cell count, blast percentage, performance status and ELN cytogenetic risk score (RS). All Cox models were stratified by protocol. Subgroup analyses of overall survival (OS) and disease-free survival (DFS) were performed using Kaplan-Meier curves stratified by race using log-rank tests. All statistical tests were two-sided. Analyses included only patients with complete data for the variables of interest. Results: Data was collected across 10 phase II and III interventional trials for newly diagnosed adult AML that accrued patients between 1984 and 2019. The study population included 3469 White, 184 Black, and 156 Other patients with a Black representation of 1.1-11% across trials. Blacks were significantly younger at diagnosis with a median age of 47.9 years compared to 53.5 years in Whites (p<0.001). Racial groups were well matched for gender and performance status. Black race was an independent prognostic factor for inferior OS (HR 1.212, CI 1.01 – 1.453; p = 0.0383) and DFS (HR 1.313, CI 1.05-1.641; p = 0.017). Complete cytogenetic results were available for 117 Black and 2162 White patients and revealed no significant racial differences in the distribution of ELN 2017 cytogenetic RS, although core binding factor AML was non-significantly enriched in Black patients (12.8% vs 8.3%). No difference was observed between Blacks and Whites in the prevalence of complex karyotype (CK), CK with -5/del(5q), -7/del(7q), or -17/del(17p), and AML-MRC including +8 and del(20q). Notably, the ELN 2017 cytogenetic RS effectively predicted OS in Black (57.8 vs 14.2 vs 5.8 months in favorable, intermediate and adverse RS, p = 0.018), and White patients (60.1 vs 15.2 vs 7.1 months, p < 0.0004 for Whites) but only predicted DFS for White AML patients (p < 0.0001 for Whites, p=0.48 for Blacks). In patients with molecular data for FLT3-ITD (n=1218), CEBPA (n=576), TP53 (n=572), or NPM1(n=683), no racial difference in the prevalence of these mutations was observed. However, NPM1 mutations were associated with inferior OS in Blacks compared to Whites (19.1 vs 8.9 months; p = 0.0095). Black and White AML patients had similar responses with complete remission rates of 58.2% vs 57.5%, p=0.55, and treatment tolerability with 30-day mortality of 7.1% vs 8.9%, p=0.50. However, consolidation approaches differed significantly. Among patients that underwent stem cell transplant (SCT), a significantly higher percentage of White patients received allogenic SCT compared to Blacks (48.5% versus 37.1%, p <0.01). Conclusions: This study represents one of the largest race-based comparisons of cytogenetic abnormalities and clinical outcomes in prospective trials of intensive chemotherapy in AML . Our data confirms the independent prognostic relevance of race in AML survival and validates the predictive ability of the ELN 2017 cytogenetic RS for OS across racial groups. There is ancestry-based attenuation of the survival benefit of NPM1 mutations as previously reported, underscoring the need to tailor the current treatment approach to NPM1 mutated AML based on race. The availability of NGS data limited the genomic analysis to a subset of patients. Future studies should examine the depth of treatment response incorporating MRD biomarkers and explore the effect of race on co-occurring mutations and the leukemic stem cell transcriptome to better explain the observed disparities. Finally, persistent disparities in access to allo-SCT even within the context of clinical trials reinforces the need to address diversity in the stem cell donor pool and social barriers to transplant.

Abstract Introduction Nadir bone marrow biopsies (BM Bx) are routinely performed around day 14 to assess early response to AML intensive induction therapy. The presence of residual disease prompts initiation of reinduction therapy, often with another cycle of intensive chemotherapy. Whether there are characteristics of nadir BM Bx that predict for response to intensive reinduction is unknown. To evaluate this, we analyzed data from ECOG-ACRIN clinical trials in AML of intensive induction chemotherapy with nadir biopsy information available to determine predictors of outcomes after reinduction. Methods We included patients from ECOG-ACRIN E1900 (Fernandez NEJM 2009) and arm A of E2906 (Foran ASH 2015) who received induction therapy with daunorubicin and cytarabine (7+3), had residual disease (blasts ≥5% or cellularity ≥20%) at nadir BM Bx and received reinduction chemotherapy. Nadir BM Bx characteristics that were evaluated included blast percentage and cellularity as well as both absolute and relative (percentage change, e.g. 20% to 10% = -50%) differences calculated between diagnosis and nadir for each parameter. Complete remission (CR) after reinduction therapy, disease free survival (DFS) and overall survival (OS) were outcomes for all analyses. Logistic regression models were used to evaluate associations with CR, and Cox proportional hazards models were used for DFS and OS. For models evaluating changes in blast percentage or cellularity as predictors, baseline blast percentage or cellularity was included as a covariate, respectively. Results Of 1013 patients identified, 750 (74%) had a nadir biopsy, 233 (23%) had evidence of residual disease, received reinduction therapy, and were included in the primary analysis. The median age was 58 and 42% were female. Cytogenetic risk category (by ELN2017) was adverse in 31%, intermediate in 66% and favorable in 3%. The median nadir BM Bx blast was 30% (range 0 to +97%) and cellularity was 20% (0 to +100%). The median absolute difference in blast percentage between baseline and nadir BM Bx was -15% (-95% to +66%) with a median relative difference of -36% (-100% to +400%). After reinduction, 118 patients (52%) achieved a CR. Neither absolute difference in blast percentage (OR 0.99, 95%CI 0.98-1.00, p=0.20) nor relative difference (OR 1.00, 95%CI 0.99-1.00, p=0.33) predicted CR. There was similarly no association with DFS (HR = 1.00, 95%CI: 0.99-1.01, p=0.65) or OS (HR = 1.00, 95%CI 0.99-1.01, p=0.76). Blast reduction ≥50% similarly did not predict these outcomes. We also evaluated the impact of any reduction in blast percentage (responders) from baseline to nadir and again found no association with CR (OR 1.65, 95%CI 0.90-3.03, p=0.11). Similarly, there was no association with DFS (HR 0.74, 95%CI 0.51-1.09, p=0.13) or OS (HR 0.81, 95%CI 0.58-1.13, p=0.21) in responders vs nonresponders. No association with CR, DFS or OS were identified when performing the same analysis in intermediate and adverse cytogenetic subgroups. We found no association with CR when nadir cellularity was assessed as a continuous variable (OR 0.99, 95%CI 0.98-1.00, p=0.10) or by relative difference (OR 0.99, 95%CI 0.99-1.00, p=0.10). There was a trend towards association with absolute reduction in cellularity from baseline to nadir and CR (OR 0.99, 95%CI 0.98-1.00, p=0.06). No association was identified between relative difference in cellularity and DFS and OS, nor was there an association among cytogenetic risk subgroups with any outcome. Discussion In intensively treated patients with residual disease at nadir BM Bx (i.e. day 14) who received intensive reinduction, the likelihood of achieving a CR was not influenced by the magnitude of disease reduction nor the extent of disease at the time of nadir biopsy. Similarly, there were no nadir biopsy features that predicted DFS or OS after intensive reinduction therapy. Given alternative reinduction therapies such as hypomethylating agents and venetoclax are available, these results suggest that the decision to attempt a second intensive induction cycle following the unequivocal presence of residual disease should not be influenced by characteristics of the nadir BM Bx. Although patient-specific factors such as patient fitness may favor a switch to less intensive options, these results support consideration of intensive reinduction therapy in patients with residual disease at nadir biopsy, even without changes in blasts or cellularity.

Abstract Background In patients with myelofibrosis (MF) undergoing allogeneic hematopoietic cell transplantation (allo-HCT), graft-versus-host disease (GVHD) prophylaxis has traditionally included a calcineurin inhibitor (CNI) plus methotrexate (MTX). We conducted a retrospective study comparing the safety and efficacy of post-transplant cyclophosphamide (PTCy)-based GVHD prophylaxis to CNI-based regimens. Methods This study was approved by the Mayo Clinic IRB. Patients with myelofibrosis who underwent allo-HCT after 2016 at Mayo Clinic in Arizona and Florida were included. Categorical variables were compared using Chi-square or Fisher's exact tests. Overall survival (OS) was defined from transplant to death, and progression-free survival (PFS) from transplant to relapse or death. OS and PFS were estimated using Kaplan-Meier methods; univariate differences were assessed with log-rank tests. The cumulative incidence of acute and chronic GVHD and time to neutrophil and platelet engraftment were analyzed using competing risk models, with death as a competing event; differences were tested using Gray's test. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs). Results A total of 110 patients were included. 53 patients received PTCy-based prophylaxis (43 PTCy/Tac/MMF, 1 PTCy/CSA/MMF, 9 PTCy/Siro/MMF), while 57 received non-PTCy regimens (54 Tac/MTX +/- 39 T-cell depletion, 2 CSA/MMF, 1 Tac/MMF). Median age at transplant was 63 (range: PTCy 40-76; others 38-74) years in both groups; 59 were male (58.5% PTCy vs 49.1% others). Median Karnofsky Performance Status (KPS) and HCT–Comorbidity Index (HCT-CI) in patients receiving PTCy vs non-PTCy were 90 vs 80 and 1 vs 3, respectively. Conditioning intensity was similar: 22.6% myeloablative vs 21.7%, and 77.4% reduced-intensity vs 76.7% in PTCy and non-PTCy, respectively (p=1.000). Stem cell source was peripheral blood in all patients except one in the non-PTCy group who received bone marrow. 58 patients had primary MF (54.7% PTCy vs 50.9% others), and 52 had secondary MF (45.3% PTCy vs 49.1% others), including essential thrombocythemia (28.3% PTCy vs 31.6% others), polycythemia vera (17.0% vs 15.8%), and MPN-NOS (0% vs 1.8%). Median follow-up was 26.2 months (95% CI: 20.7-52.7) in the PTCy and 60.6 months (95% CI: 53.1-70.6) in the non-PTCy cohort. CD3 and CD33 donor chimerism ≥95% at day +100 was 66.7% and 86.7% in PTCy vs 63.6% and 92.7% in others, respectively (p=0.50); day +100 driver molecular mutations were present in 32.1% of PTCy and 32.0% of others (p>0.99). Rates of acute GVHD grades ≥2 and ≥3 were not statistically significant, in the PTCy group (37.7% vs 49.1% p=0.229 and 17.0% vs 22.8% p=0.445, respectively). Chronic GVHD (any grade) occurred in 42.3% of PTCy vs 38.2% of others (p=0.664), while moderate-to-severe cGVHD was lower with PTCy (21.2% vs 27.3% p=0.461). Platelet engraftment was significantly delayed in the PTCy group (median 33 vs 21 days, p=0.030). Median time to neutrophil engraftment was also delayed in the PTCy group (20 vs 17 days, adjusted p=0.025). Age-adjusted HR for time to platelet engraftment was 0.60 (95% CI: 0.41–0.90; p=0.014), and for neutrophil engraftment 0.65 (95% CI: 0.44–0.95; p=0.025), indicating significantly delayed hematopoietic recovery with PTCy. Graft failure occurred in 9.4% vs 5.3% (p = 0.48); primary 7.5% vs 3.5%, secondary 1.9% vs 1.8% in PTCy vs non-PTCy groups, respectively. Relapse or progression occurred in 11.3% of PTCy vs 17.5% of others (p=0.355); four patients in the non-PTCy group progressed to AML post-transplant, versus none in the PTCy group (p=0.119). 1-year TRM was 22.6% in the PTCy group and 14.0% in the non-PTCy group, p = 0.324. Median OS was 72.8 months in the PTCy group (95% CI: 49.9 months, upper limit not estimable [NE]) and 93.4 months in the non-PTCy group (95% CI: 48.5 months, upper limit NE), although the difference was not statistically significant (p=0.739). After adjusting for age and HCT-CI, there were no significant differences in PFS (adjusted HR 1.37; 95% CI: 0.73–2.56; p=0.331) or OS (adjusted HR 1.27; 95% CI: 0.64–2.51; p=0.498). Conclusions In myelofibrosis patients undergoing allo-HCT, PTCy-based GVHD prophylaxis showed similar rates of grade ≥2 acute and moderate-severe chronic GVHD compared to non-PTCy regimens. Engraftment was significantly delayed, while OS and PFS were comparable. PTCy appears to be a safe and viable alternative to CNI-based prophylaxis.

Abstract Introduction Survival following allogeneic hematopoietic cell transplantation (allo-HCT) has improved over the last several decades. Implementation of reduced-intensity conditioning and improvement in graft selection, graft vs. host disease (GVHD) prophylaxis and treatment, and infection disease management, among others, have contributed to reducing non-relapse mortality (NRM). The use of post-transplant cyclophosphamide (PTCy) for GVHD prophylaxis, in particular, has been associated with reduced incidence of acute and chronic GVHD in both HLA-matched related and matched unrelated donor allografts. In this study, we aim to determine prognostic factors for NRM (including early NRM defined as within 100 days post-transplantation), disease-related mortality (DRM), and overall survival (OS) in a large cohort of patients following allo-HCT. Methods Patients who received consecutive allo-HCT at our institution from 2009-2023 were included. Clinical data were collected from retrospective reviews of the electronic medical records. Patient- and transplant-related variables were compared between patients who died and those who were alive at 100 days post allo-HCT. Univariate and multivariate Cox proportional hazard models were used to identify prognostic associations between risk factors and OS. Kaplan-Meier method was used to evaluate OS. Log-rank test was used to compare OS between groups. Statistical significance was set to < 0.05. Results A total of 536 patients (male=285, 53%) were included. Median age at time of allo-HCT was 59 (range, 19-75) years. Most patients were White/Caucasian (n=232, 86%). The most common diagnoses included acute myeloid leukemia (AML) (n=110, 41%), myelodysplastic syndrome (n=52, 19.2%), myelofibrosis (n=23, 9%), B-cell acute lymphoblastic leukemia (B-ALL) (n=22, 8.1%), non-Hodgkin lymphoma (n=21, 8%), and chronic myeloid leukemia (n=10, 4%). The median follow-up for survivors was 4.2 (range, 1.1-14.4) years. A total of 80 (14.9%) patients died within 100 days with most deaths attributed to NRM (n=61, 76%). Specific causes of death included infection/sepsis in 22 (27.5%) patients, GVHD in 10 (12.5%), respiratory failure in 9 (11.2%), multiorgan failure in 5 (6.3%), graft failure in 5 (6.3%), and other causes in 10 (12.5%). Progressive disease was the cause of death in 19 (23.8%) patients. Male gender (HR=1.92; p= 0.006), remission status other than CR1 or CR2 for acute leukemia patients (HR=8.44; p<0.0001), non- PTCy strategies (HR=2.4; p= 0.0006), and earlier year of transplantation (HR=1.12; p=< 0.001) were associated with increased risk of mortality at 100 days on univariate analysis. Only use of TBI (HR=2.56, p=0.048) and earlier year of transplantation (HR=1.2; p=0.001) were associated with increased risk of DRM at 100 days post-allografting on univariate analysis. Pertaining to risk of NRM at 100 days, male gender (HR=1.89; p=0.02), diagnosis other than acute leukemia (HR=2.27; p=0.004), non-PTCy strategies (HR=2.44; p=0.003), and earlier year of transplantation (HR=1.1; p=0.004) were adversely associated with NRM. On multivariate analysis, only earlier year of transplantation was found to be associated with increased risk of DRM at 100 days (HR 1.15; p=0.049). Male gender (HR=1.78; p=0.035), diagnosis other than acute leukemia (HR=2.38; p=0.003), and non-PTCy strategies (HR=2.2; p=0.032), were associated with increased risk of NRM at 100 days. Conclusion Non-relapse mortality (NRM) accounted for most deaths within the first 100 days of allo-HCT, primarily due to infection/sepsis and GVHD. Factors associated with increased NRM included male gender and diagnoses other than acute leukemia. Significantly, post-transplantation cyclophosphamide (PTCy) was the only treatment strategy modification that decreased 100-day NRM and improved survival, independent of the transplantation year.

Abstract Background Myelodysplastic syndromes (MDS) develop from the acquisition of somatic mutations over years or decades. While some mutations are random stochastic events, others derive from extrinsic agents that promote genomic instability, including environmental exposures. Agent Orange (AO) is a phenoxy herbicide used by the U.S. military as a defoliant during the Vietnam War (1962-71), often diluted with gasoline to promote aerosolization, contaminated with the carcinogen dioxin during the manufacturing process, and linked to various cancers. We studied AO as a risk factor for MDS. Methods The prospective National Heart, Lung, and Blood Institute National MDS Natural History Study includes patients (pts) with suspected or recently diagnosed MDS enrolled from 6/2016-6/2024. Bone marrow samples underwent central pathology review, resulting in diagnoses including MDS, MDS/myeloproliferative neoplasm overlap (MDS/MPN), or clonal cytopenia of undetermined significance (CCUS). Pts completed detailed assessment for AO exposure and other risk factors for MDS development. Associations between AO exposure, mutation prevalence, and key covariates (demographics, diagnosis, military service, clinical history, cytogenetics and smoking) were assessed using univariate tests of association, multivariable regression and Cox regression models for survival and progression. Results Among 2115 enrolled pts, 1191 (56%) had a myeloid malignancy or precursor condition and 130 (6.1%) reported AO exposure, the majority (96%) male. Compared to unexposed pts, AO exposed pts were more likely to derive from the 1945-54 birth cohort (p<.001), of age to serve in Vietnam, and to have an ultimate diagnosis of MDS or CCUS vs. a non-clonal diagnosis (57% vs. 44%, p=.046). AO exposure was more common among Blacks (12% vs 6%, p=.02), specifically Black males (21% vs 9%, p=.006). AO exposure was marginally associated with International Prognostic Scoring System (IPSS)-R poor-risk cytogenetics (p=.066) and lower baseline platelet count (p=.072). In multiple regression analyses, risk of AO exposure was significantly higher for the 1945-1954 birth cohort (OR [95% CI]=10.3 [4.4-30.6], p<.001), among those with military service (OR=24.1 [11.9-55.8], p<.0001), and for Blacks vs Whites (OR=2.6 [1.2-5.5], p=.017). The crude risk of AO exposure trended higher for patients with MDS compared to idiopathic cytopenia of undetermined significance (ICUS; OR=2.1 [0.9-6.0],p=.13), but not in multivariable analysis (OR=1.3 [0.5-4.4, p=.60]). AO exposure trended toward an association with younger age at MDS diagnosis (p=.06) and toward having a prior primary malignancy (49% vs. 41%, p=.09): Compared to non-AO exposed pts, AO exposed pts had higher rates of prior prostate cancer (16% vs. 8%), notable given its documented association with AO exposure. AO exposure was not associated with a history of or intensity of cigarette smoking (p=.67). After accounting for age, diagnosis, sex, and military service, AO exposure was significantly associated with increased numbers of pathogenic variants in 53 genes (OR=1.2 [1.0-1.4], p=.02) and with having Very Poor/Poor risk IPSS-R cytogenetics (OR=3.7 [1.2-11.1], p=.02). AO exposed and non-exposed pts had similar overall survival (HR=1.1 [0.8-1.7], p=.50), but those exposed to AO had a higher risk of disease progression in the first two years following diagnosis (HR =1.9 [1.2-2.8], p=.004). AO exposed pts appeared more likely to have del (5q) (15% vs. 8%) and del (20q) (13% vs. 5%) karyotypic abnormalities, and TP53 (7.7% vs. 4.5%), STAG2 (5.1% vs. 2.8%), and NRAS mutations (3.4% vs. 1.7%), although sample sizes were small. Focusing on gene pathways, AO exposed pts appeared more likely to have abnormalities in RAS signaling (10.3% vs. 5.7%), cell cycle (7.7% vs. 4.5%), and cohesion complex pathways (6.0% vs. 3.1%), but less likely to have abnormalities in cytokine receptor pathways (0% vs. 4.5%). ConclusionsIn our representative national cohort of pts with at least one cytopenia, and for the first time, we demonstrated that AO exposure is associated with younger age at MDS diagnosis, ultimate MDS diagnosis, genetic complexity of MDS, increased risk of disease progression, and with Black race, despite Black individuals comprising just 16% of men who served in the Vietnam War and being less likely to have MDS than white individuals. AO should formally be recognized as a risk factor for the development of MDS.

PURPOSE Ziftomenib—a potent, highly selective, oral menin inhibitor—was well tolerated and demonstrated encouraging clinical activity as monotherapy for relapsed/refractory NPM1 -mutated ( NPM1 -m) and KMT2A -rearranged AML in the KOMET-001 phase I trial. METHODS In the registration-enabling phase II part of KOMET-001, patients with relapsed/refractory NPM1 -m AML received ziftomenib 600 mg once daily. The primary end point was the rate of complete remission with full hematologic recovery (CR)/CR with partial hematologic recovery (CRh). RESULTS From January 26, 2023, to May 13, 2024, 92 patients (median age, 69 years [range, 33-84]) were treated. The primary end point was met, with a CR/CRh rate of 22% (95% CI, 14 to 32; P = .0058); 61% were negative for measurable residual disease. Overall response rate was 33% (95% CI, 23 to 43), with a median duration of 4.6 months (95% CI, 2.8 to 7.4). Prespecified subgroup analyses showed comparable CR/CRh regardless of previous therapy, including venetoclax, or type of comutations. Median overall survival was 6.6 months (95% CI, 3.6 to 8.6). Common grade ≥3 treatment-emergent adverse events were febrile neutropenia (26%), anemia (20%), and thrombocytopenia (20%). Differentiation syndrome occurred in 25% of patients (15% grade 3; no grade 4-5) and was manageable with protocol-defined mitigation. Three patients (3%) discontinued treatment because of ziftomenib-related adverse events. CONCLUSION Ziftomenib demonstrated significant clinical benefit and deep responses in patients with heavily pretreated, relapsed/refractory NPM1 -m AML. Ziftomenib was well tolerated with a safety profile consistent with previous studies, including manageable differentiation syndrome, lack of clinically significant QTc prolongation, and low rates of myelosuppression.