Citations

Abstract Myelodysplastic syndromes (MDS) are clinically and biologically diverse disorders, emphasizing the need for personalized treatment approaches. The International Working Group for Prognostication of MDS (IWG_PM) recently introduced a molecular classification, referred to as the MDS taxonomy, that categorizes patients into 16 subgroups based on 21 gene mutations, 6 cytogenetic abnormalities, and loss of heterozygosity (LOH) at TP53 and TET2 loci. This study sought to validate and enhance the clinical relevance of the MDS taxonomy by analyzing a large retrospective cohort ( n = 5136) and transcriptomic data from a prospective cohort ( n = 477). The taxonomy successfully identified subgroups with distinct clinical characteristics and disease progression patterns. However, incorporating gene interactions from taxonomy subgroups did not improve the prognostic performance of the Molecular International Prognostic Scoring System (IPSS‐M). We further assessed whether the taxonomy could guide management in patients receiving disease‐modifying therapies. Except for the “ TP53 ‐complex” subgroup, taxonomy classifications were not predictive of hypomethylating agent response or transplant outcomes. Nonetheless, they correlated with overall survival, suggesting that while both IPSS‐M and the taxonomy capture disease biology, other non‐genetic factors may influence treatment response. RNA sequencing confirmed the biological distinctiveness of the taxonomy groups. Transcriptomic profiling of CD34+ bone marrow cells revealed unique, homogeneous gene expression patterns, particularly within the AML‐like, bi TET2 , SF3B1 , and TP53 ‐complex subgroups. Further integration of multi‐omics data may refine MDS classification, improving clinical decision‐making and guiding the development of targeted therapies.

VEXAS syndrome is a clonal hemato-inflammatory disorder impacting older, predominantly male patients, characterized by systemic inflammation and progressive bone marrow failure. It is caused by somatic mutations in UBA1, an X-linked gene, essential for initiating cellular ubiquitination. Loss-of-function mutations, most commonly M41 missense variants, lead to decreased expression of the cytoplasmic isoform, UBA1b, resulting in accumulation of misfolded proteins and activation of the endoplasmic reticulum stress pathway. Patients classically present with systemic and often refractory inflammation, requiring chronic glucocorticoid treatment and targeted immunosuppressive therapies. A central hallmark of this syndrome is progressive bone marrow failure and associated cytopenia, with a diagnosis of myelodysplastic syndromes (MDS) being reported in approximately 30-50% of patients while only 1% of unselected MDS patients have UBA1 mutations. This review examines current literature on distinct MDS features reported in VEXAS syndrome. We first summarize the defects and alterations in the hematopoietic system from UBA1 mutations, including associated peripheral blood and bone marrow findings. Next, we describe the histological and molecular characteristics of patients with VEXAS syndrome, with and without MDS, and review potential treatment strategies, including responses to hypomethylating agents. Finally, we highlight that VEXAS-associated MDS is a challenging diagnosis but one with unique clinical, laboratory, and morphological features, including prognostic implications.

ABSTRACT Hypomethylating agents (HMA) and allogeneic hematopoietic stem cell transplantation (alloHSCT) have both demonstrated remissions in VEXAS; however, comparative data is lacking. We conducted a multicenter, retrospective analysis of 66 patients diagnosed with VEXAS syndrome treated with HMA ( n = 35) or alloHSCT ( n = 31). Baseline characteristics such as genetics, co‐morbidities, and performance status were balanced between the groups, except older age in the HMA group. Median follow‐up from therapy initiation was 18 months (95% CI: 11–26), and 14 (21%) deaths were reported (alloHSCT n = 3; HMA n = 11). Among all evaluable patients within the alloHSCT cohort, all patients achieved molecular remission, and a substantial proportion of patients discontinued glucocorticoids (58%). In contrast, HMA therapy was associated with lower but meaningful rates of molecular remission (22%) and glucocorticoid discontinuation (6%). In a real‐world setting, HMA therapy was associated with a high discontinuation rate related to toxicity or lack of response. On multivariable analysis adjusted for age and Charlson Comorbidity Index, alloHSCT was associated with improved overall survival (HR = 0.20, 95% CI: 0.05–0.81; p = 0.024). This association remained consistent across multiple ancillary sensitivity analyses, including restriction to transplant‐eligible patients, patients aged ≤ 75 years, 1:1 matching, and propensity score‐based weighted analyses. Although limited by retrospective design, these findings suggest that alloHSCT remains an attractive and potentially curative strategy in selected patients with VEXAS. Prospective validation of these findings is warranted.

Abstract Germline variants in DDX41 are the most frequent genetic predisposition to adult hematologic malignancies. The most common variants are truncating, implicating loss of function in the pathogenesis. However, non-truncating variants account for 30-40% of cases, and their impact on essential DDX41 functions remains unknown. We utilized a genetic complementation assay to assess the functionality of 10 recurrent germline non-truncating variants of DDX41. All variants restored viability to Ddx41 -deficient hematopoietic progenitor cells at exogenous expression levels. In contrast, the hotspot mutant p.R525H, which is somatically acquired at disease onset in >50% of patients, failed to restore viability. CRISPR-based modeling in cell lines and mice revealed heterogeneity: some variants were non-functional at endogenous expression levels whereas others maintained complete functionality, supporting normal cell proliferation and even lifelong hematopoiesis in a homozygous setting. Notably, co-expression of p.R525H with some variants caused impaired hematopoietic progenitor cell viability, indicating a dominant-negative effect of p.R525H. In contrast, other variants, all classified as variants of unknown significance, were unaffected by the presence of p.R525H. A screen of 100 disease-associated variants confirmed that many non-truncating germline variants are susceptible to p.R525H-mediated dominant-negative effects, whereas wild-type DDX41 is not. These findings indicate that DDX41 variant curation is complicated by variable effects on functionality and variant-specific interactions with somatically-acquired DDX41 mutations. The dominant-negative effect of p.R525H provides a mechanistic basis for the conclusion of recent patient cohort analyses that co-occurrence with a somatic hotspot mutation is a reliable indicator of DDX41-driven disease in carriers of non-truncating variants.

e18524 Background: Venetoclax (Ven) in combination with hypomethylating agents (HMA) is FDA-approved front-line therapy for elderly or unfit patients with newly-diagnosed acute myeloid leukemia (ND-AML); however, majority relapse or are refractory ( Pratz AJH 2024 ). We examined survival outcomes in the setting of frontline Ven-HMA failure. Methods: ND-AML patients with failure to achieve complete remission (CR/CRi) or loss of CR/CRi after front-line Ven+HMA, excluding post-transplant relapse were retrospectively studied. Response was evaluated per European Leukemia Net 2022 criteria ( Dohner Blood 2022 ). Results: 356 patients with ND-AML (median age 75 years; 65% males; 55% secondary) receiving frontline Ven+HMA (median; 3 cycles (1-26), had refractory [n=219 (62%)], or relapsed disease [137 (38%)]. At diagnosis, karyotype was complex in 142/347 (41%). Mutations involved TP53 (29)%, ASXL1 (19%), RUNX1 (17%), SRSF2 (15%), KRAS/NRAS (13%), IDH2 (7%), FLT3-ITD (7%), NPM1 (6%) and IDH1 (5%). At treatment failure, complex karyotype was present in 72/180 (40%), including 55 from baseline. In 137 patients with paired NGS, mutations persisted in TP53 (88%), IDH1 (86%), IDH2 (78%), NPM1 (75%), K/NRAS (73%), RUNX1 (70%), FLT3-ITD (65%) mutations. Mutations were acquired in a minority [ IDH1 / IDH2 (2% each) TP53 (3%), NPM1 (4%), FLT3-ITD (5%) K/NRAS (6%)]. Clearance of mutations were infrequent for TP53 (12%) and IDH1 (14%). At median follow-up of 4 months (mo) (0-80) from the time of relapse/refractory disease, 320 (90%) patients have died, with median survival of 4 mo (1-2-3 yr survival 19%/8%/5%). On multivariate analysis, peripheral blasts >20%, complex karyotype, and wild-type IDH1 were independent predictors of inferior survival, while allogeneic stem cell transplant (ASCT) was associated with improved survival. A 3-point prediction model based on peripheral blasts ≥20%, complex karyotype, and wild-type IDH1 stratified patients into low-, intermediate-, and high-risk groups, with median survival of 7, 3, 2 months, respectively (p<0.01). 13 patients underwent ASCT (median survival; 22.5 mo; 3-yr survival 33%), from low (n=10) or intermediate-risk groups (n=3). Salvage therapy (n=170, 48%) yielded CR/CRi of 31% for Ven+HMA (n=36), 54% intensive chemotherapy (n=26), 50% FLT3 inhibitors (i) (n=22), 37% IDH1/2i (n=19), 25% other regimens (n=69). Median survival was similar: Ven+HMA 8 mo, intensive chemotherapy 10 mo, FLT3i 6.5 mo, IDH1/2i 14 mo, other regimens 6 mo, but inferior with supportive care (2 mo; p<0.01). Conclusions: The current study identifies peripheral blasts ≥20%, complex karyotype, and wild-type IDH1 as predictors of inferior survival in ND-AML relapsed/refractory to front-line Ven+HMA and underlines that while no specific salvage therapy conferred superior outcomes, ASCT was indispensable for long-term survival.

6588 Background: TET2 is the most frequently mutated gene in chronic myelomonocytic leukemia (CMML) and has been associated with favorable outcome, with recent studies suggesting a more pronounced prognostic impact in the presence of ≥2 TET2 mutations ( Csizmar et al. leukemia 2025;39:2030; Kynning et al. Br J Haematol. 2025 Nov 25. doi: 10.1111/bjh.70264 ). We sought to determine if this particular observation extended to patients with ≥3 TET2 mutations ( TET2 MUT ) and also held true in the context of recently reiterated genetic risk factors. Methods: The current study was conducted under institutional review board approved minimum risk protocols allowing retrospective patient data collection and analysis. Diagnostic criteria were according to the International Consensus Classification (Arber et al. Blood 2022. 140:1200). All statistical analyses were conducted using JMP 18 software. Results: 536 CMML patients who underwent CLIA-approved NGS testing were stratified according to the number of TET2 MUT : 221 (41%) wild-type, 148 (28%) with one, 153 (29%) 2, and 14 (2%) ≥3 TET2 MUT . Co-mutation frequencies with significant differences between one vs. two TET2 MUT included ASXL1 (46% vs. 29%; p<0.01), KRAS (7% vs. 14%; p=0.02) and SETBP1 (5% vs. 0.6%; p=0.02). Phenotypic comparisons revealed preponderance of prognostically favorable traits associated with wild-type TET2 but no significant differences between one vs. two TET2 MUT . In age-adjusted univariate analysis, transplant-censored overall survival (TCOS), calculated from the time of mutation detection, was superior in patients with one (p<0.01; HR 0.7) or 2 (p<0.01; HR 0.4) but not ≥3 (p=0.4) TET2 MUT , vs. those with wild-type TET2 . TCOS was also superior with 2 vs. 1 (p=0.02; HR 0.7) but not with ≥3 vs. 1 (p=0.7) TET2 MUT ; the results were similar when TCOS was calculated from the time of diagnosis. Multivariable analysis confirmed the survival advantage of exactly two TET2 MUT vs. wild-type TET2 (p<0.01; HR 0.5), one TET2 MUT (p<0.01; HR 0.6), or ≥3 TET2 MUT (p<0.01; HR 0.4), after adjusting for age, sex, anemia, circulating blasts ≥2%, and leukocyte count ≥13×10⁹/L. The favorable impact of exactly two TET2 MUT persisted in CMML-MD and CMML-MP and remained independent of TET2 VAF, mutation type, karyotype, and other prognostically relevant mutations. This association was sustained in the BLAST (p<0.01; HR 0.5) and CPSS-mol (p=0.02; HR 0.7) models, but not in BLAST-mol model (p=0.12). Conclusions: Mechanistic explanation for this novel observation includes the possibility that TET2 mutational categories based on mutation count reflect distinct biological states rather than having a simple linear effect. The persistence of this signal despite adjustment for established molecular and genetic risk factors supports its consideration in the development of future CMML prognostic models.

6525 Background: Venetoclax plus hypomethylating agent (Ven-HMA) is the standard treatment for unfit patients with newly diagnosed acute myeloid leukemia (ND-AML), with Ven typically administered for 28 days (d) per cycle (DiNardo NEJM 2020) . However, the optimal duration of Ven across risk groups remains unclear. We examined survival outcomes with Ven 7, 14, 21, and 28d in ND-AML, in the context of European LeukemiaNet (ELN) and Mayo Genetic risk models. Methods: ND-AML patients receiving Ven-HMA at the Mayo Clinic were retrospectively studied. Patients were stratified by ELN 2024 (Döhner Blood 2024) and Mayo Genetic risk (Gangat Am J Hematol 2025) , and analyzed using standard statistical methods. Results: 540 patients (median age 75 years, 52% de novo) received HMA with Ven for 7d ( n =33), 14d ( n =117), 21d ( n =96), or 28d ( n =294). ELN and Mayo risk distributions were 22%/35% high, 18%/56% intermediate, 60%/9% low risk, respectively. Baseline characteristics were comparable. CR/CRi rates were comparable across Ven durations, with the exception of lower CR/CRi with 7d vs 21d (p=0.04). Risk-stratified CR/CRi showed variations across Mayo and ELN groups but without significant differences based on Ven duration (Table). Allogeneic transplant rates were 15%, 18%, 18%, 20% for 7, 14, 21, 28d (p=0.86). At a median followup of 37.7 months, median overall survival (OS) differed by ELN risk (6.6, 11.9, 20 months) and Mayo genetic risk (7.8, 17.4 months, not reached (NR)), for high, intermediate, low risk (p<0.01), respectively. Median OS was comparable across Ven 7, 14, 21, 28 d (13, 13, 17, 14 months; p=0.84), with corresponding 1/3/5-year survival rates (Table). 30/60d mortality differed by Ven duration; 7d 10%/20%, 14d 7%/15%, 21d 4%/13%, 28d 4%/6%. Compared with 28d, 30d mortality was higher with 7d and 14d (p=0.07/0.03), and 60d mortality was higher with 7d, 14d, and 21d (p=0.02/0.01/0.05). OS was comparable across Ven durations within ELN intermediate/low risk and all Mayo risk groups, except among ELN high risk, patients receiving 14d Ven had inferior OS compared with 21d and 28d (p<0.01). Cumulative incidence of relapse at 1 year was similar among patients receiving 14, 21, 28d Ven (16%, 18%, 18%;p >0.1). Conclusions: Survival outcomes were comparable across Ven 7, 14, 21, 28 d in ND-AML, with outcomes driven by Mayo Genetic and ELN risk. Despite differences by Ven duration in high-risk groups, higher early mortality with 7d and 14d likely reflects treatment selection. Prospective trials are needed to establish risk adapted Ven dosing strategies. 7 (N=33) 14 (N=117) 21 (N=96) 28 (N=294) P-value CR/CRi (%) 52 63 72 65 0.19 7≠21 Mayo Risk High 33 49 58 55 0.53 - Intermediate 55 69 80 69 0.17 7≠21 Low 100 85 80 84 0.84 - ELN Risk High 33 30 57 53 0.21 - Intermediate 33 59 64 56 0.63 - Low 62 74 80 73 0.46 - Median OS (months) 13 13 17 14 0.84 - 1/3/5-year survival (%) 53/NR/NR 51/25/22 56/23/20 55/27/20 >0.1 -

5045 Background: Radioligand therapy with radium-223 (Rad) and lutetium-177 (Plu) demonstrates notable hematologic toxicities in patients (pts) with prostate cancer (PC), including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Delivery of ionizing radiation to the bone microenvironment is a known risk factor for accelerating clonal hematopoiesis, although the incidence of clonal cytopenias with these agents is not well characterized. We hypothesized that pts treated with Rad and/or Plu would have higher risk of clonal cytopenia of undetermined significance (CCUS) vs matched controls in the “real-world”. Methods: We performed a retrospective study using de-identified aggregate data from the TriNetX US Research Collaborative Network from January 2010 to December 2025. Adult males with PC who received ≥1 administration of Plu and/or Rad were included; pts with prior myeloid malignancy were excluded. Primary outcomes were incidence of CCUS and MDS. Propensity score matching (PSM) was performed based on age, race, prior diagnosis of leukopenia, anemia, thrombocytopenia, or pancytopenia. Risk ratios (RR) with 95% confidence intervals (CI) were calculated. Results: We identified 2,569 pts treated with Plu alone and 2,007 treated with Rad alone and compared them with pts with advanced PC without exposure to either agent (unexposed control) (Table 1). After PSM, the incident risk of CCUS was greater in Rad-exposed pts (RR 2.62, 95% CI 1.45 – 4.73, p < 0.001) while Plu was not associated with a significant increase in CCUS or MDS. Direct comparison after PSM (n=1,433) demonstrated lower risk of pancytopenia (RR 0.46, 95% CI 0.37 – 0.56, p <0.001) and CCUS (RR 0.41, 95% CI 0.20 – 0.81, p =0.008) in Plu vs Rad. In unadjusted analysis, pts receiving both Plu and Rad had increased incidence of CCUS vs Plu alone (RR= 3.64, 95% CI 1.87 - 7.07, p <0.001) and higher risk of MDS vs either agent alone. Conclusions: This “real-world” analysis demonstrates that compared with unexposed controls, Rad – but not Plu – is associated with an increased risk of CCUS. Treatment with Plu and Rad portends a higher risk of CCUS than Plu alone, as well higher risk of MDS than either drug alone. Study limitations include its retrospective nature, missing/ unknown data (e.g. bone marrow and mutation analysis), and potential selection and confounding biases. As treatment sequencing evolves for pts with metastatic PC, further evaluation of clonal hematopoiesis, MDS/AML with adequate sample size and follow up in this population is warranted. ¹⁷⁷Lu-PSMA-617 Exposed(n = 2,569) Unexposed(n =2,569 ) Risk Ratio (95% CI) p -value CCUS 1.03% (26) 0.67% (17) 1.54 (0.84 – 2.82) 0.16 MDS 0.94% (24) 0.55% (14) 1.72 (0.89 – 3.32) 0.10 Radium-223 Exposed(n = 2,007) Unexposed(n = 2,007) Risk Ratio (95% CI) p -value CCUS 1.97% (39) 0.75 (15) 2.62 (1.45 – 4.73) <0.001 MDS 0.85% (17) 0.75% (15) 1.13 (0.57 – 2.26) 0.72