Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative therapy for myelofibrosis (MF), yet graft dysfunction remains a significant complication. In this single-center retrospective study, we analyzed 48 adults with primary or secondary MF who underwent allogeneic HSCT between 2012 and 2023 to characterize the incidence, risk factors, and outcomes of graft dysfunction, including primary graft failure (PrGF) and poor graft function (PoGF). Graft dysfunction occurred in 25% of patients, with PrGF in 14.6% and PoGF in 10.4%. Higher disease burden, splenomegaly and post-transplant cyclophosphamide–based graft vs host disease (GVHD) prophylaxis were significantly associated with graft dysfunction. Transplant-related variables, including conditioning intensity, donor type, graft source, and HLA matching, were not associated with graft dysfunction. All patients with PoGF who received CD34⁺-selected stem cell boost (SCB) achieved hematopoietic recovery and survived beyond 2 years post-transplant, whereas PrGF was associated with early mortality, with a median survival of 127 days posttransplant. These findings demonstrate that graft dysfunction is common after HSCT in MF and driven predominantly by disease-related factors. PrGF and PoGF represent biologically and clinically distinct entities with markedly different prognoses and therapeutic windows, and early intervention with SCB offers an effective salvage strategy for selected patients.

PURPOSE:As risk stratification for patients with AML treated with lower-intensity venetoclax-based therapy remains suboptimal, we developed and validated a prognostic model integrating clinical, cytogenetic, and molecular features. METHODS:We assembled a multinational data set comprising 2,092 adults with newly diagnosed AML treated with hypomethylating agents plus venetoclax (HMA + VEN). One thousand nine hundred eighteen patients with complete data were randomly divided into training (70%) and internal validation (30%) cohorts. Two independent external validation cohorts were assembled (n = 500 and n = 222). Modeling overall survival (OS), Elastic Net regression was applied in 1,000 bootstrap samples from the training cohort to select variables for a Ridge regression, which generated a continuous Prognostic Risk Integration for Survival Modeling (PRISM) score and risk categories based on tertiles (PRISM-3: low, moderate, high). These PRISM indices were then computed for the validation cohorts and compared with the 4-gene classifier (based on mutations in FLT3-ITD, N/KRAS, and TP53). RESULTS:PRISM integrated 17 clinical and genomic variables and demonstrated a linear association with OS. PRISM-3 stratified survival consistently across all cohorts (median OS: 25.1-28.8 months for low risk, 12.5-14.7 months for moderate risk, and 5.8-6.7 months for high risk; P < .001). Compared with the 4-gene classifier, PRISM-3 reassigned approximately 40% of patients (and >50% of those with favorable risk) and demonstrated significantly better discrimination in validation cohorts (C-index 0.63-0.65 v 0.59-0.61; P < .05). CONCLUSION:PRISM is a validated prognostic model for patients with AML receiving HMA + VEN that improves survival risk stratification beyond current standard tools and supports individualized, risk-adapted clinical decision making. The model, the PRISM-AML Risk Calculator, is publicly available.

Azacitidine (Aza) plus venetoclax (Ven) is standard treatment for older/unfit patients with newly diagnosed (ND) acute myeloid leukemia (AML). The approved 28-day (D) Ven schedule is associated with prolonged cytopenias, causing frequent dose reductions and cycle delays. Retrospective studies show similar efficacy and reduced toxicity with abbreviated Ven dosing, but prospective data is lacking. We conducted OPTI-AML(NCT03013998), a prospective randomized phase 2 trial comparing 28D Ven (AV28) versus 14D (AV14) with Aza (75mg/m²x7D) for C1-2 in genomically agnostic ND-AML patients ≥60 years. The primary endpoint was complete remission (CR) rate achieved at any time with two cycles of therapy. Between 2023-2025, 169 patients received AV28 (n=83) or AV14 (n=86). CR across two cycles was 49.4% (AV28) versus 43% (AV14); difference of 6.4% [90%CI:-6.1% to 19.0%], not meeting non-inferiority criteria. Patients with NPM1/ IDH2 mutations had higher CR rates with AV28 (60.9% vs. 33.3%), while CR rates were equivalent (45%) for other subgroups. Composite CR rates were 80.7% (AV28) versus 68.6% (AV14) and MRD negativity was similar (77.6% vs. 76.5%). Although AV28 had more frequent treatment interruptions, count recovery after C2, grade ≥3 adverse events and early mortality were similar. In conclusion, the study did not demonstrate non-inferiority of AV14 compared with AV28 during C1-2 in an unselected ND-AML cohort. However, as the confidence interval for the difference covered 0, CR rate for AV28 was not significantly different than AV14. Certain subgroups may benefit from prolonged Ven exposure, but these findings require validation in larger studies, especially as triplet regimens evolve.

Introduction Allogeneic hematopoietic stem cell transplantation (HSCT) is potentially curative for hematologic malignancies. Donor availability remains limited for non-Caucasian patients due to human leukocyte antigen (HLA) diversity and registry underrepresentation, leading to greater use of mismatched unrelated and haploidentical (Haplo) family donors. Advances in graft vs host disease (GVHD) prophylaxis, including post-transplant cyclophosphamide (PTCy), have improved outcomes in mismatched settings. Whether these strategies have reduced racial disparities in HSCT outcomes remains unclear. Methods We performed a single-institution retrospective study of 818 consecutive patients undergoing their first allogeneic HSCT for hematologic malignancies from 2012–2022. Patients were stratified by self-reported race and ethnicity to evaluate whether PTCy reduced outcome disparities. This analysis compared clinical variables and outcomes between Black and non-Hispanic White (NHW) patients, focusing on overall survival (OS), relapse-free survival (RFS), and GVHD incidence. Results Of 818 patients, 15% were Black and 75% NHW. Black patients were younger (52 vs 59 yrs, p<0.001), had a lower HCT-CI score (p<0.01), and had younger donors (37.5 vs 51.5 yrs, p<0.001) than NHW patients. Black patients had lower access to matched unrelated donors (16.9% vs 57%, p<0.001), but had higher use of related donors (54.0% vs 28.6%, p<0.001) such as Haplo transplants with PTCy (25% vs 4.6%, p<0.0001).Despite increased use of alternative donors, Black patients had lower rates of acute GVHD compared with NHW patients (29% vs. 37.1%; p = NS), with similar chronic GVHD incidence. Table 1 shows outcomes among Black patients demonstrating a trend toward improved survival using mismatched related vs mismatched unrelated donors: 2-year overall survival was (71% vs. 52.8%, p = NS). Of note, for all patients, OS and RFS were similar between Black and NHW patients. Conclusions Outcomes for Black patients support the use of family donors, including Haplo with PTCy, when a matched donor is unavailable. Post-transplant outcomes were comparable between Black and NHW patients, despite the more frequent use of HLA-mismatched donors. PTCy-based Haplo HSCT appears to mitigate donor registry inequities. Our data suggests that for Black patients without access to a matched donor, selection of a Haplo family donor may be preferable over a mismatched unrelated donor, a result that needs confirmation in a larger data set.

Gene mutations and chromosome abnormalities are important components of prognostication in acute myeloid leukemia (AML). Here we assessed whether DNA methylation patterns in AML patients can augment risk assessments provided by genetic and other markers to better predict outcomes. Unsupervised DNA methylation patterns separating patients into 13 DNA methylation subtypes (epitypes) were used to classify 1,262 patients with de novo AML. Epitypes were predominantly comprised of a predominant genetic alteration; however, some patients within epitypes lacked cardinal alterations and were termed genetic alteration-like. Interestingly, patients displaying alteration-like DNA methylation patterns of CEBPAbZIP, FLT3-ITD, core-binding factor, KMT2A-rearrangements and other abnormalities displayed outcomes similar to patients with actual cardinal alterations. We further derived a DNA methylation signature enriched in patients with FLT3-ITD mutations that involved hypomethylation of STAT binding sites, termed the STAT hypomethylation signature (SHS). SHS positivity identified patients with inferior outcomes further adding to the prognostic significance of FLT3-ITD. Machine learning modeling revealed these DNA methylation signatures together significantly added to genetic, demographic and clinical markers to predict remission, relapse and overall survival. In summary, DNA methylation signatures capture patients who mimic cardinal genetic mutations providing additional prognostic information that may be used to in concert with standard genetic markers.

For myelofibrosis (MF) patient's undergoing hematopoietic stem cell transplant (HSCT) engraftment failure is a life-threatening challenge, largely due to primary graft failure (PGF) and/or prolonged poor graft function (PGFxn). Although medical management of MF patients has improved with the introduction of JAK2 inhibitors, HSCT remains the only potentially curative option. In this single center retrospective analysis, we studied a cohort of 50 consecutive patients with primary MF or secondary MF (post ET/PV) who underwent allogeneic HSCT at our institution between 2012 and 2023. PGF was defined according to the CIBMTR definition as failure to achieve a sustained ANC ≥ 500/uL by posttransplant day 30. We defined PGFxn as prolonged platelet transfusion dependence and/or growth factor dependence necessitating a CD-34 selected stem cell boost (SCB). Survival outcomes were censored at 2 yrs post-transplant to avoid time bias. The median age at transplant of 63.5 years (range 35-74 years). The cohort was predominantly male (n=28; 56%), Caucasian (n=41; 82%) and most had JAK2 mutated (n=36, 72%) primary MF (n=47; 94%). The median Dynamic International Prognostic Scoring System (DIPSS) score at transplant was 2 (Intermediate-1 risk). The majority of patients received a JAK2 inhibitor prior to transplant (80%, n=40). The graft source was peripheral blood stem cells for 45 patients (90%), and bone marrow for 5 patients (10%). Reduced intensity conditioning (RIC) regimens were used in 38 cases (76%), and myeloablative regimens in 12 cases (24%). Donors included matched unrelated donors in 28 cases (56%), matched related donors in 15 (30%), mismatched unrelated donors in 6 (12%), and a haploidentical related donor in 1 case (2%). GVHD prophylaxis consisted of MTX/tacrolimus-based regimens (n=35; 70%), post-transplant cyclophosphamide (PTCy)-based prophylaxis (n=9; 18%) or other regimens (n=6; 12%). Eight patients (16%) met criteria for PGF, and 5 additional patients (10%) had PGFxn for which they received a CD-34 selected stem cell boost. Primary Graft Failure Group (n=8): All patients had donor predominant chimerism in blood and/or marrow. Two PGF patients received early SCB (on days 93 and 151 post-transplant) with subsequent improvement in hematopoiesis, and both survived beyond 2 yrs post-transplant. One patient received a second transplant from a different donor and died shortly thereafter without engraftment. Among patients with PGF, 3 patients (37.5%) died before posttransplant day 100 with cause of death being infection. The 2-year OS of the PGF group was 40%. Poor Graft Function Group (n=5): All patients had donor predominant chimerism in blood and/or marrow. PGFxn patients all received a SCB at a median of post-transplant day 99 (day range 34-141), and all had improvement in hematopoietic function. 2 year OS for the PGFxn group was 75%. Predictive Factors for Impaired Graft Function: In univariate analysis, the only significant associations with either PGF or PGFxn were DIPSS score >3 (p=0.026), and PTCy based GVHD prophylaxis [p=0.019; OR = 7.07, 95% CI: 1.57-31.86]. Notably, graft source, HLA matching and conditioning intensity were not predictive of impaired graft function in our series. Conclusion: These findings confirm previous observations that impaired graft function is relatively common after allogeneic transplantation for MF. Our data suggests that PGF and PGFxn may be associated with advanced disease burden reflected by the higher DIPSS scores, as well as the use of PTCy-based GVHD prophylaxis. SCB was used as a rescue intervention in both PGF and PGFxn groups, with generally favorable outcomes. Unfortunately, the feasibility of arranging a prompt SCB can be challenging, particularly with registry donors. Further analyses of larger data sets are warranted to inform selection of the best GVHD prophylaxis strategies as well as optimization of selection criteria for earlier consideration of stem cell boost in this challenging patient population.

Venetoclax (VEN) combined with hypomethylating agents (HMA) has improved response rates in elderly or unfit acute myeloid leukemia (AML) patients, yet 30–40% of treated individuals fail to achieve durable remissions. Traditional genomic risk stratification alone (e.g., ELN 2022) does not capture the dynamic interplay of pro- and anti-apoptotic signals that drive treatment sensitivity or resistance. To better resolve the apoptotic signaling mechanisms driving the VEN + HMA response, we employed the single-molecule protein interaction detection (SPID) platform, which enables high-resolution imaging of endogenous protein–protein interactions (PPIs) (Chun et al., Nat Biomed Eng, 2024). Using this platform, we quantified 12 BCL2-family PPIs in pre-treatment AML samples from 47 patients at Winship Cancer Institute. In a subset of 28 patients, paired pre- and on-treatment samples were analyzed to track VEN+HMA-induced PPI remodeling. Each assay measured complex occupancy between anti-apoptotic proteins (BCL2, BCL-xL, MCL1) and their pro-apoptotic binding partners (e.g., BAX, BIM, BAK), normalized to total protein levels. Somatic mutations were defined by targeted sequencing. Baseline PPI analysis revealed mutation-specific rewiring of apoptotic complexes that clarify differential VEN + HMA responses. AMLs with isolated FLT3-ITD mutations (without NPM1 or DNMT3A co-mutations) exhibited marked alterations in BCL2-family PPIs compared to FLT3-ITD–wildtype AML. These included elevated BCL2–BIM complexes, increased levels of unoccupied BCL-xL and MCL1, and higher total BCL-xL and MCL1 protein levels—suggesting enhanced buffering capacity for BIM and BAX, which may be displaced by VEN. In contrast, AMLs with isolated NPM1 mutations showed minimal or modest PPI shifts, indicating a more apoptotically primed state at baseline. Notably, co-mutations of FLT3-ITD with either DNMT3A or NPM1 synergistically increased anti-apoptotic complex formation beyond levels seen with single mutations, establishing FLT3-ITD as the dominant driver of baseline apoptotic rewiring. These findings suggest a mutational hierarchy in regulating anti-apoptotic dependency, with FLT3-ITD exerting the strongest effect, followed by DNMT3A and NPM1. Paired-sample analysis revealed dynamic, response-associated shifts in BCL2 family PPIs during VEN + HMA therapy. In responders, VEN-induced displacement of BAX from BCL2 was accompanied by high BCL2 occupancy (low levels of unoccupied BCL2), consistent with effective apoptotic engagement. In contrast, non-responders exhibited persistent or increased BCL2–BAX complexes with low BCL2 occupancy (high levels of unoccupied BCL2), suggesting inefficient VEN binding and impaired apoptotic activation. Notably, all TP53-mutant AMLs showed stable or increased BCL2–BAX complexes and elevated unoccupied BCL2 on-treatment relative to pre-treatment profiles, indicative of persistent apoptotic resistance. In contrast, NPM1- and IDH1/2-mutant AMLs demonstrated the opposite pattern—reduced BCL2–BAX occupancy and increased BCL2 occupancy following VEN-HMA treatment—consistent with effective apoptosis induction. Additionally, VEN + HMA treatment led to marked displacement of BAK from BCL-xL and MCL1 in IDH1/2-mutant AMLs, further highlighting distinct, mutation-specific apoptotic rewiring that underlies VEN sensitivity or resistance. This integrative PPI–genomic analysis establishes a mechanistically grounded framework for predicting response to VEN + HMA therapy in AML. By linking mutation-specific apoptotic rewiring to quantitative single-molecule measurements of BCL2 family PPIs, we uncovered complex interaction patterns that are not detectable by conventional protein assays. Together, this work supports the development of a next-generation, biomarker-driven strategy for VEN + HMA therapy in AML, with the potential to guide personalized treatment decisions and improve clinical outcomes.

Olutasidenib is a potent, selective, oral, small molecule inhibitor of mutant IDH1 (mIDH1) which induced durable remissions in high-risk, relapsed/refractory (R/R) mIDH1 AML patients in a phase 1/2 trial. We present a pooled analysis from multiple cohorts of the phase 1/2 trial of patients with R/R AML who received combination olutasidenib and azacitidine therapy. Adult patients with mIDH1R132 AML received 150 mg olutasidenib twice daily plus standard-of-care azacitidine (OLU + AZA) and were evaluated for response and safety. Sixty-seven patients with R/R mIDH1R132 AML received combination OLU + AZA. Median age was 66 years (range 28–82) and 54

PURPOSE:Azacitidine and venetoclax is a standard frontline treatment regimen for newly diagnosed older adults with AML; however, long-term outcomes remain poor. Revumenib is an oral menin inhibitor with clinical activity in AML patients with nucleophosmin-1 mutation (NPM1m) or lysine methyltransferase 2A rearrangements (KMT2Ar). METHODS:We conducted a phase I dose-escalation and expansion study of azacitidine, venetoclax, and revumenib at two dose levels (113 mg or 163 mg orally every 12 hours in combination with strong cytochrome P450 inhibitor azoles) in patients aged 60 years and older newly diagnosed with AML with NPM1m or KMT2Ar (ClinicalTrials.gov identifier: NCT03013998). RESULTS:Overall, 43 patients were enrolled and treated. There was no maximal tolerated dose identified. Differentiation syndrome was present in eight (19%) patients and QTc Fridericia prolongation was present in 19 (44%) patients, and neither required permanent discontinuation of revumenib. The overall response rate with an intention-to-treat population was 88.4% (95% CI, 74.9 to 96.1; NPM1m: 85.3%; KMT2Ar: 100%), the rate of composite complete remission (complete remission [CR] + CR with partial or incomplete hematologic recovery) was 81.4% (95% CI, 66.6 to 91.6; NPM1m: 79.4%; KMT2Ar: 88.9%), and the rate of CR was 67.4% (95% CI, 51.5 to 80.9; NPM1m: 65%; KMT2Ar: 78%). No patient had refractory disease after 1-2 cycles of treatment. The median time to first response was 28 days, and 84% of responders achieved remission within the first cycle. All 37 patients evaluated had no evidence of measurable residual disease by a centralized flow cytometry assay. CONCLUSION:In older adults newly diagnosed with NPM1m or KMT2Ar AML, the combination of azacitidine, venetoclax, and revumenib was able to be safely administered with high rates of CR and clinical activity.

e18561 Background: The introduction of JAK2 inhibitors has improved symptom control for patients with myelofibrosis (MF), but allogeneic hematopoietic stem cell transplant (HSCT) remains the only curative option. A significant challenge for patients with MF undergoing HSCT is poor or delayed hematopoietic engraftment (PGF), presumably reflecting the challenge of establishing a stable hematopoietic niche in a fibrotic marrow space. Methods: We retrospectively studied a cohort of 41 consecutive patients with primary MF and post-ET/PV MF who received an HSCT from 2012 to 2023 at our institution. We examined patient and HSCT-specific variables influencing poor engraftment necessitating a CD 34+ stem cell boost (SCB) for poor graft function following transplantation. We used a logistic regression model to analyze various factors, including age, graft source, donor type, match grade, CMV seropositivity, acute and chronic graft vs host disease (GVHD), conditioning regimens, GVHD prophylaxis, DIPSS, HCT-CI score, and mutations in JAK2, MPL, and CALR. Results: Six of the 41 patients (15%) received a SCB because of poor engraftment. This rate is significantly higher compared to the 1.4% of acute myeloid leukemia/acute lymphoblastic leukemia (AML/ALL) patients and 3.8% of myelodysplastic syndrome (MDS) patients who required an SCB at our institution. The most common reason for SCB was for pancytopenia in 5 patients and bicytopenia (anemia and thrombocytopenia) in 1 patient. All six MF patients receiving SCB had originally received a peripheral blood stem cell graft, and all had received a JAK2 inhibitor prior to transplant. The median time from transplant to SCB was 112 days. However, we did not identify any statistically significant predictors of the need for an SCB. Two year overall survival was 83% in the SCB group vs 54% in the non-SCB group (p=NS). Infection was the primary cause of non-relapse mortality among patients receiving SCB. We also found that the SCB group had numerically lower rates of acute GVHD but had slightly higher rates of cGVHD (p=NS). Conclusions: We acknowledge that our analysis is limited by the small sample size. However, despite the challenges of poor graft function in MF patients undergoing HSCT, our findings suggest that favorable outcomes are possible if hematopoietic and immune reconstitution is successfully achieved following SCB.

Background: The 4-gene molecular prognostic risk score (mPRS) improves overall survival (OS) prediction in patients (pts) with newly diagnosed AML (ND-AML) treated with hypomethylating agents (HMA) and venetoclax (VEN). Yet given the broad clinical and molecular heterogeneity of AML, risk stratification remains suboptimal. We consolidated a large international cohort of ND-AML pts treated with lower-intensity regimens including HMA or low-dose cytarabine (LDAC) plus VEN to improve OS prognostication. Methods: We analyzed 2,273 ND-AML adult pts who received frontline VEN with HMA (n=2,222) or LDAC (n=51) at an academic medical center in the US, UK, France, Germany, or Italy who had complete clinical, cytogenetic, and molecular data. An initial set of 1,974 patients were split into a training (TC, N=1,339) and internal validation (VC, N=635) cohorts, stratifying on key clinical variables (de novo vs. secondary AML, TP53 and IDH2 mutations, hematopoietic cell transplantation [HCT], death). An additional N=299 patients, acquired later, were utilized as an external validation set. OS was measured from therapy start, estimated with Kaplan-Meier curves, and compared across risk groups using the log-rank test. HCT was considered a time-dependent covariate. OS discrimination was estimated by Harrell's C-index (C). Clinical and genomic features (with a frequency ≥ 4% required for nominal features) were included in model development. Cox L1-penalized regression of OS applied to 1,000 bootstrap samples from the TC was used to identify stable features (selected with a consistent direction in ≥75% of bootstrap iterations). These features were entered into a robust Cox model. Non-significant genes “ResMut” were grouped according to their directional effect on OS to create “ResMut-fav” denoting the presence of ≥1 mutation in a favorable set of residual genes. The final robust Cox model beta coefficients were added to calculate patient-specific risk PRISM scores. Quartiles of PRISM scores defined four clinical PRISM risk groups: low (L), moderate (M), high (H), and very-high (VH). Results: In the TC, median pt age was 74 years; 61% were male. 41% had secondary AML (sAML), arising from an antecedent hematologic disorder (sAML-AHD) in 33% (11% with treated AHD) and from prior therapy in 8%. The mPRS distribution was 56% higher-, 22% intermediate-, and 22% lower-benefit. HCT rate was 12%. The final PRISM model included age, sex, sAML-AHD, ELN 2022 complex karyotype and other adverse-risk cytogenetic abnormalities, and adverse mutations in KRAS, PTPN11, FLT3-ITD, JAK2, ASXL1, and TP53. Favorable features included diploid karyotype, mutations in RUNX1 or IDH2, and ResMut-fav (comprising CEBPA, BCOR, IDH1, SF3B1). For TC pts, at median follow-up of 20.8 months (mo), median OS (mOS) was 12.2 mo (95% CI: 10.9–13.6). Higher PRISM scores were associated with worse OS (1-unit increase HR: 2.50; 95% CI: 2.21–2.82; C: 0.654). Median OS by PRISM risk group L/M/H/VH was 29.6, 17.6, 11.3, and 5.6 mo (C: 0.641; p<0.001). PRISM risk groups improved OS discrimination vs. mPRS (C: 0.641 vs. 0.583, p<0.001), with similar benefit after adjusting for HCT (C: 0.650 vs. 0.594, p<0.001). There were no significant differences in considered variables between the TC and VC. In the VC, median follow-up was 24.4 mo and mOS 13.0 mo (95% CI: 11.5–14.8). The PRISM score was significantly associated with OS (1-unit increase HR: 2.28; 95% CI: 1.91–2.71; C: 0.653). Median OS by PRISM group L/M/H/VH was 24.4, 15.0, 11.7, and 5.8 mo, similar to rates observed in the TC. PRISM risk groups outperformed mPRS (C: 0.648 vs. 0.613, p=0.002), including after adjusting for HCT (C: 0.659 vs. 0.629, p=0.018). The external validation cohort was marginally older (median age 75 years) with fewer HCT recipients (8%) compared to the initial TC/VC. Higher PRISM scores remained highly associated with OS (1-unit increase HR: 2.49, 95% CI: 1.92-3.24; C: 0.661). Median OS by PRISM group L/M/H/VH was 28.8, 13.9, 12.5, and 6.3 mo. PRISM risk groups had better OS discrimination than mPRS (C: 0.648 vs. 0.584, p=0.010), including after adjusting for HCT (C:0.662 vs. 0.607, p=0.004). Conclusions: Integration of prognostically relevant clinical and genomic features into the PRISM score and subsequent PRISM risk groups enables improved discrimination of survival following lower-intensity HMA/LDAC+VEN therapy in patients with ND-AML compared to current risk classification frameworks.

Venetoclax (VEN), in combination with hypomethylating agents (HMAs) such as azacitidine or decitabine, is a widely used treatment for AML patients, yet the molecular biomarkers contributing to sensitivity to the VEN+HMA regimen remain incompletely elucidated, particularly with regard to the role of BCL2-family proteins. In this study, we retrospectively collected BMMCs or PBMCs from AML patients prior to initiation of VEN+HMA therapy at Winship Cancer Institute of Emory University. A total of 47 specimens were analyzed, including 33 from newly diagnosed AML patients and 14 from relapsed or refractory AML cases at the time of sample collection. Clinical outcomes were categorized based on the best response to VEN+HMA therapy, with refractory cases labeled as "NR" (non-responders; 17 patients) and all other cases labeled as "R" (responders; 26 patients). To investigate protein interactions between the BCL2 family, we employed the Single-molecule Protein Interaction Detection (SPID) platform (Chun et al., Nat. Biomed. Eng., 8, 2024). 12 distinct protein biomarkers were assessed based on three anti-apoptotic proteins: BCL2, BCLxl, and MCL1. ROC analysis was performed to evaluate the association between individual biomarkers and clinical outcomes of VEN+HMA therapy. To develop a predictive model incorporating BCL2-family biomarkers, we utilized a linear model rectified with a ReLU activation function. The trained model was interpreted using SHAP value analysis. To enhance the variability of biomarkers, we calculated normalized protein complex levels relative to protein levels. For example, the BCL2-BAX complex level was divided by the BCL2 protein level to assess the fraction of occupied BCL2 across samples. Among the 21 biomarkers analyzed, the normalized BCLxl-BAK complex level demonstrated the strongest predictive performance, with an AUC of 0.734 (95% CI: 0.536-0.859) for distinguishing responders to VEN+HMA therapy. We developed a response prediction model for VEN+HMA therapy with 12 biomarkers, and achieved performance with 96.2% sensitivity and 100% specificity. Interpretation of the model using SHAP analysis revealed key contributors to sensitivity and resistance to the VEN+HMA regimen. Specifically, Higher levels of the BCL2-BAX and BCLXL-BAK complexes were associated with sensitivity to VEN+HMA therapy. Conversely, lower levels of the BCL2-BIM and MCL1-BIM complexes were linked to resistance to the treatment. Notably, the expression level of MCL1 (measured after heat denaturation) significantly influenced sensitivity to VEN+HMA therapy. This study highlights the potential of BCL2-family interaction profiles in developing a response prediction model for VEN+HMA sensitivity. Further model refinement and validation in independent cohorts are essential to improve its predictive performance and reliability. Byungsan Choi, Yunseo Lee, Lilly Gu, Keonho Lee, Eunyoung Kim, Martha L. Arellano, William G. Blum, Hongwon Lee, Janghee Woo. Development of a response prediction Model for venetoclax-based therapy utilizing molecular interactions among BCL2 family members [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2056.

Olutasidenib is a potent, selective, oral inhibitor of mutated IDH1 (mIDH1) approved for the treatment of relapsed or refractory (R/R) mIDH1 AML. The phase 2 pivotal cohort (NCT02719574) demonstrated efficacy and tolerability of olutasidenib, with a complete remission (CR)/CR with partial hematologic recovery (CRh) rate of 35% and a median duration of CR/CRh of 25.3 months. This analysis evaluated baseline characteristics and changes in platelet count, hemoglobin levels, and blast percentages by time to response (TTR) among patients in the pivotal cohort. Adult patients with R/R mIDH1 AML were treated with olutasidenib 150 mg BID. Patients were stratified by best overall response and TTR: <2 months, 2 to 4 months, and >4 months. Hematologic characteristics, including platelet counts, hemoglobin levels, and blast burden were evaluated over the course of olutasidenib treatment. Among 147 efficacy-evaluable patients, the median age was 71.0 years (range 32.0, 87.0) and 50% were female. Mean baseline hemoglobin levels, platelet counts, and blast percentages were 9.7 g/dL, 87.2×109/L, and 45.2%, respectively. In the overall cohort (N=147), increases in hemoglobin were seen early in the course of treatment and levels continued to increase over 12 cycles; a mean of 11.0 g/dL was seen at cycle 6. Similarly, platelet counts increased and blast percentages decreased over the course of treatment, with a mean platelet count of 136.3×109/L and blast percentage of 14.2% at cycle 6. A total of 71 patients (48%) achieved overall response criteria; 47 patients (32%) achieved CR and 51 (35%) achieved CR/CRh. Among CR/CRh responders, 28 (55%) achieved a response in <2 months, 17 (33%) from 2 to 4 months, and 6 (11.7%) at >4 months. Patients with TTR >4 months had lower baseline platelet counts and hemoglobin levels and higher blast percentages compared with earlier responders. Mean hemoglobin level of 12 g/dL was achieved by cycle 4, 6, and 8 in <2, 2-4, and >4 month TTR groups, respectively. Mean blast count below 5% was achieved by cycle 2 in the <2 month TTR group, by cycle 4 in the 2-4 month TTR group, and by cycle 6 in the >4 month TTR group. Additionally, in 37 patients (25%) who had a best response of stable disease (SD), several showed improvement in platelets and hemoglobin levels by end of treatment, including 7 of 21 (33%) who were previously transfusion-dependent for platelets became independent and 7 of 23 (30%) who were previously transfusion-dependent for red blood cells became independent. Later responders tended to have lower baseline platelet counts and higher bone marrow blast percentages, suggesting lower hematopoietic reserve and greater disease burden. Some patients with best overall response of SD experienced modest improvements in hematologic parameters, including platelets, hemoglobin, and transfusion independence. These findings suggest that continuing olutasidenib treatment beyond 2 cycles may offer hematologic benefits, even in the absence of an early clinical response.

Hepatocyte growth factor (HGF) is an autocrine produced cytokine that has been identified to be released by acute myeloid leukemia (AML) cells, promoting leukemia expansion and survival through multiple signaling pathways. Higher HGF levels in AML and activation of the MET signaling pathway has been associated with shortened overall survival but fortunately this pathway does not appear to be required for normal hematopoiesis, suggesting that it's an ideal target for inhibition. Ficlatuzumab is a first-in-class anti-hepatocyte growth factor (HGF) antibody that has been previously tested in numerous clinical trials. In a primary induction refractory AML population, ficlatuzumab in combination with high dose cytarabine had a complete response of 53% with minimal toxicities (NCT02109627). Notably, there is minimal or no evidence of ficlatuzumab-related myelosuppression making it an ideal candidate for combination with venetoclax (ven) and azacitidine (aza). Ven/aza has been a practice changing regimen for AML patients who are not candidates for intensive induction therapy. However, this treatment is still not curative and long-term outcomes are poor. We designed a phase 1b/2 study evaluating ficlatuzumab in combination with ven/aza in newly diagnosed older AML patients is as part of Blood Cancer United's Beat AML Master Trial. This is a US-based, multicenter, sub-study of the Beat AML Master Trial (NCT03013998) in which newly diagnosed AML patients age ≥ 60 years are assigned to an investigational therapy based on cytogenetic and central genomics. Patients eligible for this sub-study will not be candidates for intensive induction therapy and will have any genetics, ECOG status ≤ 2, and adequate organ function. The study is designed as a phase 1b safety lead-in followed by a phase 2 with two randomized dose levels. The primary objective of phase 1b is to determine the feasibility of giving ficlatuzumab in combination with ven/aza. The primary objective of phase 2 is to determine the complete remission (CR) rate and composite CR rate at the dose identified in phase 1b and a lower dose. Secondary objectives in both phases will evaluate safety, tolerability, survival, duration of remission, pharmacokinetics, and immunogenicity. A comparison of remission rates to a genetically matched control population receiving ven/aza alone will also be performed. The phase 1b portion of the study utilizes a Bayesian optimal interval design with a target toxicity rate of 25% to identify a safe dose of ficlatuzumab. The pre-specified sample size is 12 patients and will include two dose levels of ficlatuzumab (DL1: 20 mg/kg; DL-1: 15 mg/kg) in combination with ven (400 mg/day, dose adjusted based on antifungals) and aza (75 mg/kg). During induction cycles, ficlatuzumab is dosed 2 days per cycle (days 1 & 15), ven for 28 days, and aza for 7 days. Patients who achieve a marrow remission after up to two induction cycles proceed to continuation therapy cycles. Dose-limiting toxicities will be assessed during induction cycle 1. During continuation therapy cycles, ficlatuzumab will be administered 2 days per cycle (days 1 & 15), ven for 14 days, and aza for 7 days. There must be recovery of neutrophils ≥ 500/uL and platelets ≥ 50,000/uL to proceed to any continuation phase cycle. Patients may continue treatment for up to 24 cycles or until relapse. Upon completion of Phase 1b, a phase 2 study will be conducted utilizing a Simon's two-stage design. The null hypothesis that the CR rate is 35%, based on VIALE-A, will be tested against an alternative hypothesis of 55%. The first stage will require 6 of 14 patients achieving CR in order to proceed to the second stage. At the end of the second stage, the primary endpoint would be met if 21 of 44 total patients achieve CR. The phase 2 design will be applied separately to the two arms of the study evaluating the 2 doses of ficlatuzumab: (1) dose identified in phase 1b (15 or 20 mg/kg) and (2) a lower dose of 10 mg/kg. The phase 2 study will be conducted in the same manner as the phase 1b study. Exploratory objectives will assess pharmacodynamic markers of ficlatuzumab (HGF and others) and their correlation with response and toxicities. Potential additional studies will explore biomarkers of response and resistance to ficlatuzumab using multiomic platforms. The study will begin enrollment in fall 2025 at all Beat AML research sites.

Background Common targets for T-cell–redirecting immunotherapies in AML and MDS have previously presented challenges. CLN-049 is a humanized bispecific T-cell engager with dual binding specificities for FLT3 (both wild-type and mutant forms) and CD3 on a human IgG1 backbone. As a cell surface target for immunotherapy, FLT3 is expressed on >80% of AML blasts but on only a limited number of normal hematopoietic precursors and dendritic cells. In preclinical studies, CLN-049 effectively redirects T cells to kill FLT3-expressing AML blasts within the blood and bone marrow (BM). We report results from a phase 1 multiple ascending dose study evaluating the safety, tolerability, pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy of intravenously (IV) administered CLN-049 in patients (pts) with R/R AML and MDS (NCT05143996). Methods Pts aged ≥ 18 years with R/R AML or MDS were enrolled in dose escalation, 3+3 design. Testing for FLT3 expression prior to study entry was not required. CLN-049 was dosed IV using 1 or 2 step-up doses (SUD) in the first week of treatment (D1 ± D4) before weekly administration of the higher target dose (TD) (D8 onwards). Adverse events were graded by CTCAE v5, except cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS) that used Lee 2019 criteria. Response was assessed using ELN 2022 (AML) or IWG 2023 (MDS) criteria. Efficacy endpoints included complete response (CR) rate, composite complete response (CRc) rate (CR/CRi/CRh in AML or CR/CRL/CRh in MDS) and ORR (CRc + MLFS + PR). Best responses are reported. Results As of the June 9, 2025, data cut-off (DCO), 40 pts (34 AML, 6 MDS) had been enrolled across 7 cohorts (TD range 1.5–12 µg/kg). Median age was 72 years (range 25–84) with a median of 2 prior therapies (range: 1–8, AML; 1–3, MDS). Treatment-emergent adverse events (TEAEs) occurred in 95% of pts, leading to treatment withdrawal in 7.5%. All-grade (Gr) TEAEs occurring in > 10% of pts included CRS (40%), infusion-related reaction (35%), febrile neutropenia (FN), pneumonia, stomatitis, white blood cell (WBC) count decrease (17.5% each), and alanine aminotransferase increase, diarrhea, headache, hypomagnesemia, hypophosphatemia, platelet count decrease, and hypokalemia (12.5% each). Gr ≥3 TEAEs occurring in >10% of pts included FN, WBC count decrease (17.5% each), and pneumonia (12.5%). All CRS events were limited to Gr 1 or 2; the majority occurred after a SUD or TD1. One case of Gr 1 ICANS was reported in association with Gr 2 CRS after a 6 µg/kg SUD. Neither CRS nor ICANS led to treatment discontinuation. Three events of reversible transaminitis were observed in 2 pts (1 Gr 3 event at 9 µg/kg TD, 2 Gr 4 events at 12 µg/kg TD), all occurring in association with Gr 1–2 CRS. Transaminitis was restricted to pts receiving 1 SUD and was effectively mitigated by implementation of a second SUD, evidenced by 0 subsequent events in 12 pts receiving 2 SUD before the 12 µg/kg TD. At the DCO, 32 pts (29 AML, 3 MDS) were efficacy evaluable (≥1 response assessment). Anti-leukemic activity was observed at a TD of ≥ 6 µg/kg (23 pts, all AML), with a CR rate of 9% (2/23 pts), CRc rate of 30% (7/23 pts), and ORR of 57% (13/23 pts). In 9/23 pts achieving BM blasts <5%, 3 pts were MRD negative by flow cytometry; relapse was not observed in MRD-negative pts, and 1 has remained on study for > 6 months. At the highest TD studied thus far of 12 µg/kg (13 pts), CRc rate was 31% (4/13 pts), and ORR was 69% (9/13 pts). Responses were observed in pts with AML regardless of baseline genetic risk. Notably, among 5 pts with TP53-mutated AML treated at 12 µg/kg, 4 responses (2 CRh, 2 MLFS) were observed. At the doses tested, CLN-049 showed a dose-dependent increase in exposure with apparent nonlinear PK (driven by target-mediated drug disposition), moderate to high inter-subject variability, and limited accumulation. Consistent with the mechanism of action, clinical response correlated with a reduction in the frequency of FLT3-expressing blasts in the BM. Conclusions CLN-049 demonstrated an acceptable safety profile in a broad population of pts with R/R AML and MDS. Dose levels ≥ 6 µg/kg achieved promising anti-leukemic activity, including MRD negativity, in this heavily pretreated population. Responses were also observed in pts with TP53-mutated AML, a population with a particularly poor prognosis. Dose escalation continues in this ongoing study.

The FLT3 gene frequently undergoes mutations in acute myeloid leukemia (AML), with internal tandem duplications (ITD) and tyrosine kinase domain (TKD) point mutations (PMs) being most common. Recently, PMs and deletions in the FLT3 juxtamembrane domain (JMD) have been identified, but their biological and clinical significance remains poorly understood. We analyzed 1660 patients with de novo AML and found FLT3-JMD mutations, mostly PMs, in 2% of the patients. Patients with FLT3-JMD mutations had a higher relapse rate and shorter disease-free survival than those with FLT3-TKD, whereas their relapse rate, disease-free and overall survival were not significantly different from those of FLT3-ITD-positive patients. In vitro experiments showed that FLT3-JMD PMs transformed hematopoietic cells and responded well to type I and II FLT3 inhibitors. Molecular dynamics simulations were used to explore the conformational changes of JMD PMs relative to wild-type FLT3. These mutations exhibited constrained domain motions with wider gate openings, potentially enhancing drug binding. Altered residue interactions and structural changes shed light on their unique functional mechanisms, with increased allosteric pathways suggesting reduced interactions with other residues. We conclude that patients with FLT3-JMD PMs represent uncommon but important subset with distinct molecular and biological features, and may benefit from FLT3 inhibitors.

Abstract: IO-202 is a humanized immunoglobulin G1 monoclonal antibody with high affinity and specificity for leukocyte immunoglobulin–like receptor B4 (LILRB4; ILT3), which is predominantly expressed in monocytes and monocytic blasts. IO-202 induces antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis in vitro and in patients with leukemia. Herein, we present the phase 1a dose escalation data of IO-202 as monotherapy and in combination with azacitidine (AZA) in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) and R/R chronic myelomonocytic leukemia (CMML), and the phase 1b dose expansion data of IO-202 combined with AZA for the treatment of hypomethylating agent (HMA)–naïve CMML. IO-202 was well tolerated as monotherapy and in combination with AZA. Patients with R/R monocytic AML expressing high LILRB4 on leukemia blasts demonstrated clinical activity, including a complete response (CR) in dose escalation with IO-202 + AZA. In patients with HMA-naïve CMML, IO-202 + AZA led to a 27.8% CR rate and 66.7% overall response rate, based on the 2015 International Working Group response criteria for myelodysplastic/myeloproliferative neoplasms. All 18 efficacy-evaluable patients with HMA-naïve CMML (100%) achieved some form of investigator-assessed clinical benefit, including symptomatic improvement, a decrease in transfusions, reduced blasts and/or monocytes, and resolution of thrombocytopenia. Seven patients (38.9%) proceeded to allogeneic hematopoietic cell transplantation. Translational data suggest that efficacy favors patients with high LILRB4 expression, supporting the mechanism of action of IO-202. Overall, the data support a future pivotal study of IO-202 + AZA in patients with HMA-naïve CMML. This trial was registered at www.clinicaltrials.gov as #NCT04372433.