Begna, Kebede

e18607 Background: Progression to myelofibrosis (MF) is associated with worse survival and influences treatment decisions, yet predictors of fibrotic progression in polycythemia vera (PV) and essential thrombocythemia (ET) remain poorly characterized. Methods: Patients with pathologically confirmed PV or ET were identified from a retrospective chart review. Demographics (age, sex, race, ethnicity), clinical features (thrombosis and bleeding history, performance status, symptom burden, organomegaly), bone marrow pathology (cellularity, trilineage hematopoiesis, megakaryocyte proliferation and atypia, fibrosis grade), molecular markers ( JAK2 , CALR , MPL , ASXL1 , EZH2 , TET2 , SRSF2 , IDH1/2 , SF3B1 , TP53 ), cytogenetics, laboratory values, and treatment history (phlebotomy, hydroxyurea, interferon, ruxolitinib) at first bone marrow biopsy were recorded. MF progression was defined as hematologist-confirmed transformation to MF. Kaplan-Meier analyses estimated median MF-free survival (MFS), defined as time to MF progression or death. Univariable followed by multivariable Cox proportional regression were performed to identify candidate MFS predictors. The proportional hazards assumption was assessed using Schoenfeld residuals. Hazard ratios (HR) with 95% confidence intervals (CI) were computed, with p<0.05 indicating statistical significance. Results: A total of 505 PV and 198 ET patients were identified. The majority were White (PV: 92%; ET: 86%). PV patients were predominantly male (54%) whereas ET patients were predominantly female (66%). MF progression occurred in 160 (32%) PV and 32 (16%) ET patients. Death was observed in 139 (28%) PV and 10 (5%) ET patients. Median MFS was 158.5 months (95% CI: 143.0-183.0) for PV and 308.0 months (95% CI: 175.0-NR) for ET. In PV, older age at diagnosis (HR 1.04; 95% CI: 1.02-1.07; p<0.001) and shorter time since PV or ET diagnosis to biopsy (HR 0.995; 95% CI: 0.990-0.999; p=0.048) independently predicted worse MFS. In ET, bone marrow hypercellularity (HR 5.67, 95% CI: 1.40-23.0, p=0.015) independently predicted worse MFS. Conclusions: PV patients demonstrated shorter MFS compared to ET. Older age at diagnosis in PV, whereas bone marrow hypercellularity in ET was significantly associated with fibrotic progression or death. Active surveillance of at-risk patients may facilitate early detection and timely treatment initiation. Disease Variable HR (95%CI) P-value PV Age at diagnosis 1.04 (1.02-1.07) <0.001 Time since PV or ET diagnosis to biopsy 0.995 (0.990-0.999) 0.048 ET Bone marrow hypercellularity 5.67 (1.40-23.0) 0.015

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.

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 -

6530 Background: Venetoclax (Ven) plus hypomethylating agents (HMA) is standard frontline therapy for newly diagnosed AML (ND-AML) patients unfit for intensive chemotherapy and is also being considered in younger and fit patients (Fathi, Blood 2025). However, consolidation with allogeneic stem cell transplant (ASCT) is often required to secure durable remission. The current study examines predictors of post-transplant survival (PTS) in the particular scenario. Methods: ND-AML patients who received upfront Ven+HMA and underwent ASCT were retrospectively studied. PTS, relapse rate, and non-relapse mortality (NRM) were evaluated. Results: 111 ND-AML patients (58% male, 60% secondary/therapy-related, median age 70 [37-80 years]) received median 3 cycles of Ven-HMA. 22% had complex karyotype. Mutations at diagnosis included RUNX1 (18%), SRSF2 (17%), TP53 (16%), ASXL1 , IDH2 , K/NRAS and TET2 (14% each), STAG2 (11%), DNMT3A (8%) and at time of ASCT (N=78 evaluable); RUNX1 (8%), NPM1 (6%), TP53 and ASXL1 (5% each), and SRSF2 and TET2 (4% each). At ASCT, all patients were in CR/CRi; 88% after Ven-HMA and 12% after additional bridging therapy. MRD by flow cytometry was detected in 18 (24%) of 76 evaluable patients and complex karyotype in 8 (9%) of 94. Donors were mostly HLA-matched unrelated (75%), with 51% receiving fludarabine/melphalan conditioning and 67% post-transplant cyclophosphamide (PTCy). At a median follow-up of 30 months, 42 patients (38%) have died including 18 (40%) from relapse. Median PTS was not reached (NR) with 1-2-3-year survival of 69%/60%57%. On multivariate analysis, age ≥65 years (median NR vs 10 months p<0.01), STAG2 (NR vs 44 months; p=0.04), and DNMT3A mutations (NR vs.NR p=0.05) were associated with superior PTS. In analysis limited to variables at time of ASCT, age ≥65 years remained significant (p<0.01) while TP53 mutations, donor type, and MRD status were not (p>0.1). Patients <65 years more often received bridging therapy compared to ≥65 years (23% vs 7%; p<0.05); excluding salvage-treated patients did not change survival results. 18 patients (16%) experienced post-ASCT relapse with median RFS of 7 months. Relapse rates at 1/2/3 years were 22%, 30% and 31% and NRM 13%, 24%, 46%, respectively. Patients <65 years had a higher 1 yr relapse incidence than those ≥65 years (36% vs 18%; p=0.01), with similar NRM (p=0.58). PTCy was not associated with relapse (p=0.66) but showed a borderline association with higher NRM (1-/2-/3-year 17%/31%/58% vs 4%/7%/16% in non-PTCy recipients; p=0.06). GVHD rate was 44% (50% ≥grade 2) with no association with relapse (p=0.43) or NRM (p=0.99). Conclusions: In the current study, older age (>65 years), including >75 years, was independently associated with superior PTS in ND-AML patients receiving Ven-HMA. By contrast, PTS was not affected by genetic profile at the time of ASCT, donor type, conditioning regimen, or GVHD prophylaxis.

Abstract Introduction Management of acute leukemia (AL) during pregnancy remains challenging. In the first trimester, chemotherapy is toxic to the fetus, while delaying treatment may endanger maternal health, often prompting recommendations for pregnancy termination. In later trimesters, although the risk of congenital malformations decreases, complications such as preterm labor remain prevalent. Delivery prior to chemotherapy may be considered in advanced gestation. This study aimed to describe maternal and fetal outcomes of patients diagnosed with AL during pregnancy. Methods Following institutional review board approval, we retrospectively identified pregnant patients diagnosed with AL between 1995 and 2025 across Mayo Clinic sites (Minnesota, Arizona, Florida). We recorded leukemia subtype, treatment course, maternal and fetal outcomes. Results We identified 18 patients diagnosed with AL during pregnancy, including 11 with acute myeloid leukemia (AML) and 7 with acute lymphoblastic leukemia (ALL). Ten were diagnosed in the first trimester, 3 in the second, and 5 in the third. In the AML group (n=11; median age 30 years, range 18-42), one patient had acute promyelocytic leukemia (APL). ELN 2022 risk stratification was favorable in 5 (45%), intermediate in 4 (36%), and adverse in 2 (18%). In the ALL group (n=7; median age 23 years, range 19-34), 5 had B-ALL (one Philadelphia chromosome-positive) and 2 had T-ALL. All ALL cases were diagnosed in the first trimester. Among first-trimester AMLs, 2 of 3 had core-binding factor (CBF) AML. All eight patients diagnosed in the second and third trimesters had AML (1 APL, 2 CBF AML, 1 KMT2A-rearranged, 1 with DEK::NUP214 fusion, 1 complex karyotype including t(8;21), 2 with normal karyotype). Overall, 15 (83%) patients achieved complete remission (CR) or CR with incomplete count recovery (CRi) after initial induction. One patient had refractory disease and achieved partial remission after salvage, another had refractory disease and achieved CR after multiple lines of therapy, and a third achieved CR after FLAG-idarubicin and revumenib. Five patients received chemotherapy during pregnancy (3 in the first trimester, 1 in the second, 1 in the third); two of these resulted in live births. Among the 10 patients diagnosed in the first trimester, all underwent therapeutic or spontaneous abortion. Of the 3 second-trimester diagnoses, 2 underwent spontaneous or therapeutic abortion at 15 weeks. The third received 7+3 induction at 24 weeks for KMT2A-rearranged AML, followed by preterm delivery at 26 weeks and re-induction with FLAG-idarubicin plus revumenib, achieving CR. Among the 5 third trimester diagnoses, 4 delivered preterm infants (median gestational age 33 weeks) prior to chemotherapy. One patient received 7+3 at 29 weeks and delivered a viable preterm infant at 36 weeks. At a median follow-up of 6.5 years, 5 of 11 patients with AML (45%) and 3 of 7 patients with ALL (43%) died, mostly due to disease progression. Median overall survival was not reached in either group. Causes of death were as follows: 1 of AML, 1 of ALL, 3 of acute stem cell transplant (SCT) complications, 1 of chronic SCT complications, 1 of Hodgkin lymphoma, and 1 of pneumonia. Among patients diagnosed in the second and third trimesters (n=8, all with AML), 6 (75%) resulted in live births: 5 of 5 (100%) third-trimester diagnoses and 1 of 3 (33%) second-trimester diagnoses. All received intensive induction: 7+3 (n=5), 7+3 + ATRA (n=1), 7+3 + gilteritinib (n=1), and 7+3 + nilotinib (n=1). Of the second-trimester group, only one received induction prior to delivery; she later achieved CR with FLAG-ida and revumenib. Among the third-trimester group, one patient received chemotherapy prior to delivery and achieved CR followed by SCT. All but one of the 8 AML patients achieved CR after initial therapy. Conclusions Successful pregnancy outcomes were achieved in 75% of patients diagnosed with AML during the late second or third trimester. Notably, 5 (28%) of patients received chemotherapy during pregnancy. Larger, multi-institutional cohorts are warranted to further characterize the incidence and outcomes of AL in pregnancy.

Abstract Introduction Blast transformation (BT) in CMML occurs in 15-30% of patients (pts) with a median overall survival (OS) &lt;6 months (mo). While clonal evolution can be observed, biological mechanisms of BT remain unknown for many pts. Using paired samples from chronic phase (CP) and at BT, this study defines the cytogenetic and molecular landscape of BT-CMML. Methods BT-CMML pts from Mayo Clinic (n=153, 31%), MD Anderson (n=195, 40%), and 7 centers of the Groupe Francophone des Myélodysplasies (n=145, 29%) were included after IRB approval. ICC 2022 criteria defined CMML and AML. Pt data were collected at initial diagnosis or referral at CP and again at BT. Clonal dominance was inferred from a natural log-fold difference of mutation variant allele fractions (VAF). OS was censored at allogeneic stem cell transplant (alloSCT). Single-cell multiomic analyses used the Tapestri platform (Mission Bio). Statistics used R. Results Among 1,883 cases of CMML with a median follow up of 96 mo, 493 (26%) underwent BT. The median age at CP and BT was 69 and 71 years, respectively. BT-CMML pts were predominantly male (69%) and had proliferative CMML (53%) or CMML-1 (69%) in CP; 39% and 33% were considered high-risk by CPSS-Mol and BLAST-Mol criteria, respectively. The median time to BT was 16 mo (interquartile range 7-35 mo) and was not different in males vs females (p=0.60). Compared to their CP parameters (p&lt;0.001 each), pts at BT had lower median hemoglobin (10.8 vs 9.2 g/dL) and platelets (100 vs 44 x109/L) but higher leukocytes (13.9 vs 16.3 x109/L), peripheral blasts (0% vs 14%), and bone marrow blasts (6% vs 32%). Blasts exhibited mostly monocytic (57%) or immature myeloid (40%) differentiation. Abnormal karyotypes (AK) were more prevalent at BT (25% vs 62%, p&lt;0.001). Among 318 pts with paired karyotype data, 221 (69%) had a normal karyotype (NK) in CP, of which 123 (56%) remained normal at BT and 98 (44%) acquired new abnormalities. Conversely, 97 (31%) pts had an AK in CP, of which 67 (69%) acquired abnormalities or increased clonal metaphases (6%), 23 (24%) remained stable, and 7 (7%) reverted to a NK at BT. Overall, 46% acquired and 8% lost a clonal cytogenetic abnormality, while 46% remained unchanged. Numeric (37%) and structural (30%) changes were most common. Complex (12% vs 3%) and monosomal (5% vs 2%) karyotypes were more frequent at BT than in CP. Only 6 (2%) pts acquired an AML-defining rearrangement at BT. Mutational data were available for 248 paired cases. The number of somatic mutations was higher at BT (median 3 vs 4, p&lt;0.001). Mutations in RUNX1 (27% vs 39%), NRAS (23% vs 33%), KRAS (11% vs 17%), FLT3 (6% vs 15%), NPM1 (0% vs 11%), IDH2 (5% vs 11%), and CEBPA (3% vs 10%) were more frequent at BT (all p&lt;0.05). At BT, the average VAF of the dominant clone increased in 32%, decreased in 35%, and remained unchanged (delta ≤5%) in 33%. The most frequent dominant clones both in CP and at BT had mutations in TET2 (8% vs 4%) or co-dominant mutations involving SRSF2-TET2 (7% vs 3%). Mutational clonal evolution was observed in 72%, with mutations gained in 45% and lost from the dominant clone in 19%. The most gained mutations at BT were in NRAS (15%) and RUNX1 (13%). Single cell proteogenomic analyses in 4 selected CP and BT pts shed light on the impact of NRAS and RUNX1 mutations on clonal hierarchies and differentiation. Among 196 fully evaluable cases, a new cytogenetic and/or molecular aberration was uniquely gained in 106 (54%) cases and lost in 9 (5%), with 40 (20%) both gaining and losing a genetic alteration. Forty-one (21%) patients had no identifiable genetic change between CP and BT, suggesting driver alterations outside of that detected by routine analyses. Median OS was 31 mo from CMML diagnosis and 5.6 mo from BT. Compared to supportive care, treatment in CP did not prolong median time to BT (14 vs 17 mo, p=0.91) or OS (35 vs 29 mo, p=0.05), regardless of intensity. After BT, median OS was 1.2 mo with supportive care (n=83), 8.7 mo with a hypomethylating agent (HMA, n=39), 10 mo with HMA plus venetoclax (n=37), 7.8 mo with chemotherapy (n=91), and 31 mo in pts who underwent alloSCT (n=57). Conclusions In this large BT-CMML cohort, cytogenetic (46% gained, 8% lost) or mutational (45% gained, 19% lost) driver events were identified in 79% of pts, with 21% having no identifiable changes by conventional testing. Whole genome/transcriptome analyses are underway in this subgroup to identify novel drivers of BT.

Abstract Background: TP53-mutated myeloid neoplasms (MNs) represent one of the most lethal subgroups of blood cancers. The World Health Organization (WHO-5) recognize TP53-mutated (TP53mut) myelodysplastic syndrome (MDS) and International Consensus Classification (ICC) recognize TP53mut MDS and acute myeloid leukaemia (AML) as distinct disease entities, acknowledging their dismal prognosis and the urgent need for novel therapeutic strategies. However, key discrepancies exist between the classifications, creating uncertainty in diagnosis, influencing therapeutic decisions, and complicating clinical trial enrolment for patients with uniformly poor survival. Importantly, neither classifications included TP53-mutated myelofibrosis (MF), other myeloproliferative neoplasms (MPN), and MDS/MPN overlap syndromes, despite growing evidence that these cases carry similar adverse outcomes. To address these critical gaps, we conducted a comprehensive analysis across the full spectrum of TP53-mutated MN. Methods: We included TP53mut cases with variant allele frequency (VAF ≥2%) of AML, MDS, MDS/MPN overlap, myelofibrosis and other MPN managed at the Mayo clinic (Rochester, USA) and Local Health Network in South Australia (Australia). Cases were classified according to the revised 4th edition WHO classification (WHO-4R). Biallelic TP53 loss was defined as: (i) ≥2 mutations with VAF ≥2%; (ii) single TP53mut with VAF ≥2% plus 17p loss on karyotype, FISH, or SNP array; or (iii) single TP53mut with VAF ≥50% with or without 17p loss. Monoallelic loss was defined as a single TP53mut with VAF &lt;50% without 17p loss or copy neutral loss of heterozygosity. The primary endpoint was overall survival (OS) from diagnosis, censored at allogeneic transplantation. Conditional inference tree analysis was performed to define the effect of individual predictors on OS. Results: We identified 853 TP53mutMN cases including WHO-4R-defined AML (BM/PB blasts ≥20%, n=314; 36.8%), MDS with excess blasts-2 (EB-2; BM 10–19% or PB 5–19%, n=129; 15.1%), MDS-EB-1 (BM 5–9% or PB 2–4%, n=100; 11.7%), and MDS with low blasts (LB; BM &lt;5% and PB &lt;1%, n=228; 26.7%). MF included chronic phase (MF-CP, n=48; 5.6%), accelerated phase (MF-AP, n=7; 0.8%), and blast phase (MF-BP, n=17; 2.0%). Additional cases comprised other MPN-chronic phase (n=3, 0.4%) and MDS/MPN overlap syndromes (n=7, 0.8%). Of 848 evaluable TP53mut MN, 616 (72.6%) harbored biallelic TP53 loss and 232 (27.4%) had monoallelic loss, with 42.4% (n=98) of monoallelic cases harboring a complex karyotype (CK). Biallelic loss was highly prevalent in AML (83.1%), MDS (70.4%), and MDS/MPN overlap (71.4%), but was less frequent in cases with MPN (33.3%) and MF-chronic phase (25.0%). Across the spectrum, the frequency of biallelic loss increased stepwise with disease progression, rising from MDS-LB (62.8%) to MDS-EB1 (76.0%), MDS-EB2 (79.5%), AML (83.1%), and MF-AP/BP (79.2%) (P&lt;0.0001). In multivariable analysis, WHO-4R category, TP53mut VAF, biallelic loss and CK were independent predictors of poor survival in TP53mut MN. Conditional inference tree analysis stratified the cohort into seven prognostic groups with distinct median OS: (1) AML, MF-BP/AP, and MDS/MPN overlap regardless of mono/biallelic and CK status (n=335, 39.7%; median OS 4.0 months); (2) MDS-EB1/EB2 with biallelic loss or monoallelic plus CK (n=212, 25.1%; 7.2 months); (3) MDS-LB, MF-CP and MPN with CK (n=156, 18.5%, OS 10.2 months); (4) biallelic MDS-LB (n=28, 3.3%; OS 15.6 months), (5) monoallelic MDS-EB1/EB2 without CK (n=20, 2.4%; OS 26.2 months), (6) monoallelic MDS-LB without CK (n=57, 6.7%; OS 33.4 months), and (7) MF-CP and other MPN without CK (n=36, 4.3%; OS 37.0 months). This analysis defines a clear stepwise risk gradient, identifying subsets with extremely poor prognosis versus a relatively indolent disease. Conclusions: This is the first study to evaluate the prognostic impact of TP53mut MN across the entire MN spectrum, providing a framework for future refinement of TP53-driven disease classification. Key findings include: (i) MF-AP/BP and MDS/MPN overlap exhibit survival outcomes as dismal as AML, irrespective of the TP53 allele status; and (ii) complex karyotype is a surrogate for “biallelic equivalent”, refining risk interpretation in monoallelic cases. Overall, our study defines seven prognostic subgroups spanning all TP53mut MN, offering a foundation for risk-adapted clinical trial design and future classification updates.

Abstract Background: TP53-mutated (TP53mut) myeloid neoplasms (MN) are a biologically and clinically distinct subgroup of blood cancers associated with extremely poor outcomes and limited response to conventional therapies. In some patients, MN are preceded by clonal cytopenia of undetermined significance (CCUS). Prior cytotoxic exposure (treatment related, TR) is an independent predictor for survival in CCUS (Li et al, Blood Adv. 2024). As TP53mut CCUS and MN are enriched in TR cases, the interaction between cytotoxic exposure and TP53mut status on the risk of progression and survival remains unclear. Methods: Adult patients with CCUS who were evaluated at the Mayo Clinic or South Australian myelodysplastic syndrome (MDS) Registry (Adelaide, Australia) were included. CCUS and MDS were defined according to the 5th edition of the WHO classification for MN (Khoury et al, 2022), except for the exclusion of cases harboring MDS-defining cytogenetics. Next-generation sequencing was performed using a targeted panel covering genes commonly mutated in MN. In cases with &gt;1 TP53mut, VAFs were summed. Survival outcomes were assessed by Kaplan-Meier with log-rank testing. Univariate and multivariate analyses were estimated using Cox proportional hazards regression. Results: Of 320 CCUS cases, 50 (15.6%) harbored TP53mut (TP53mut CCUS), whereas 270 (84.4%) were wild-type (TP53wt CCUS). Median age at diagnosis was 71 years (range 16-99). TP53mut CCUS had a greater proportion of females (60% vs 33.7%, p&lt;0.001) and TR (66% vs 23%, p&lt;0.001) compared to TP53wt. Hematologic parameters including hemoglobin, red cell distribution width, mean corpuscular volume, white blood count, absolute neutrophil count, platelets, and bone marrow blasts were comparable between the two groups. Almost all TP53mut (n=48, 96%) were located in the DNA-binding domain and the median variant allele frequency (VAF) was 9% (range 2-46%). Five (10%) cases harbored 2 TP53mut. The distribution of TP53mut VAF among patients was as follows: ≤2.5% (n=2), 2.5-5% (n=10), 5-10% (n=19), 10-20% (n=11), and ≥20% (n=7). The proportion of cases with cytogenetic abnormalities was smaller in TP53mut compared to TP53wt CCUS(12% vs 25.9%, p=0.035). Both cohorts had a comparable median number of mutations: 2 (range 0-7) in TP53mut and 2 (range 0-5) in TP53wt. The most common co-mutations in TP53mut CCUS were TET2 (n=8, 17.8%), PPMD1 (n=7, 15.6%), DNMT3A (n=6, 13.3%), ASXL1 (n=6, 13.3%), and SRSF2 (n=4, 8.9%). At last follow up, the rate of progression was comparable between TP53mut and TP53wt CCUS (12% vs 22%, p=0.13). Median time to MN progression was not reached in TP53mut and 6.25 months in TP53wt CCUS (p=0.5197). A significantly higher proportion of TP53mut cases acquired complex cytogenetics compared to TP53wt cases (33% vs 2%, p=0.024) at MN progression. Of 20 deaths observed in the TP53mut cohort, non-myeloid hematologic malignancies (n=6, 30%), infections (n=5, 25%), and TP53mut MN (n=4, 20%) were the 3 most common causes. With a median follow-up of 4 years (IQR 1.2-4.8), median OS was longer in de novo (dn) cases (8.7 years for dn TP53wt; not reached for dn TP53mut) and shorter in TR cases (3.3 years for TR TP53wt; 4.8 years for TR TP53mut). Notably, TP53mut showed no independent prognostic impact in the entire cohort, or when stratified by TR vs dn CCUS. On multivariate analysis that included TP53mut status, factors independently associated with inferior OS included prior therapy (HR 2.21, 95% CI 1.41-3.45, p&lt;0.001), anemia (HR 4.1, 95% CI 1.88-8.99, p&lt;0.001), and thrombocytopenia (HR 2.38, 95% CI 1.43-3.95, p&lt;0.001). Similarly, TR CCUS (HR 1.6, 95% CI 1.06-2.4, p=0.03) and anemia (HR 2.15, 95% CI 1.25-3.7, p=0.006) were independently associated with inferior progression free survival. Conclusion: TP53 mut in CCUS did not independently predict inferior survival or increase leukemic transformation. While TP53mut CCUS were less likely to harbor cytogenetic abnormalities at diagnosis, significantly more cases harbored genomic instability at leukemic transformation. The poor outcomes attributed to TP53mut CCUS were driven by prior cytotoxic exposure, cytopenia – particularly anemia, and non-leukemic causes of death. These findings suggest risk stratification in CCUS should prioritize clinical context over TP53mut status alone.

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 &lt;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 &lt;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 Introduction: While newly diagnosed patients (pts) with acute myeloid leukemia (AML) who are ineligible for intensive chemotherapy have prolonged survival outcomes with venetoclax plus azacitidine (VEN+AZA) over AZA alone (2-year overall survival rate: 37.5% vs 16.9%), more can be done to further enhance outcomes (Pratz et al., 2024). CD123 is overexpressed on AML blasts and leukemia stem cells in AML. Pivekimab sunirine (PVEK) is a first-in-class antibody-drug conjugate comprised of a high-affinity anti-CD123 antibody, a cleavable linker, and an indolinobenzodiazepine pseudodimer payload. Previously, in pts with CD123-positive AML, PVEK combined with VEN+AZA demonstrated robust response rates with a manageable safety profile (Daver et al., 2023). Here we report a subgroup analysis from a preliminary cohort of frontline (1L)-treated pts with AML. Methods: Data are from the dose expansion phase of an ongoing, open-label, multicenter, fully enrolled, Phase 1b/2 study of PVEK+VEN+AZA in adults with 1L unfit AML deemed CD123-positive by investigator. Unfit pts were aged ≥75 years (yr), or aged &lt;75 yr with Eastern Cooperative Oncology Group performance status (ECOG PS) score 2–3, or ≥1 defined comorbidity. Pts received PVEK (0.045 mg/kg, intravenous [IV]) on Day (D) 7 plus VEN (400 mg equivalent, oral) daily in a 28-D cycle (cohort 1 received ≥14 D of VEN; cohort 2 received 28 D of VEN) plus AZA (up to 75 mg/m2, subcutaneous or IV) on D1–7. Bone marrow assessments were performed by D12–14 (cohort 1) or D18–21 (cohort 2) to determine VEN duration in cycle 1 and at the end of every subsequent cycle to assess responses and myelosuppression. The primary endpoint was antileukemia activity (complete remission [CR] rate) and measurable residual disease (MRD) assessments. Responses were determined using the modified European LeukemiaNet 2017 criteria (plus CR + partial hematologic recovery [CRh]). MRD-negativity was defined centrally as &lt;0.1% using multiparameter flow cytometry. Safety was assessed as a secondary endpoint. Results: Among 1L unfit pts with CD123-positive AML (n=49), the median (range) age was 77 (58–85) yr, with most pts aged ≥75 yr (n=36 [74%]). Forty-two (86%) pts reported an ECOG PS ≤1, 14% (n=7) had secondary AML, and 20% (n=10) and 51% (n=25) had intermediate or adverse cytogenetic risk, respectively; 65% (n=32) and 35% (n=17) were reported as TP53wt or TP53mut, respectively. Eight (16%) pts bridged to stem cell transplant. The median (range) number of treatment cycles and duration of treatment were 4 (1–20) and 5.5 (0.7–22.7) months (mo), respectively, for PVEK; 4 (1–20) and 5.1 (0.9–22.9) mo for VEN; and 4 (1–21) and 5.7 (0.9–23.4) mo for AZA. For cohort 1 (n=10), the median (range) duration of VEN was 4.5 (2.1–22.9) mo, and for cohort 2 (n=39), the median (range) duration of VEN was 5.7 (0.9–15.2) mo. With a median (range) follow-up of 10 (1.2–26.7) mo, 63.3% (95% CI: 48.3%–76.6%) of pts achieved CR, 79.6% (95% CI: 65.7%–89.8%) achieved CR/CR with incomplete hematologic recovery (CRi), and 73.5% (95% CI: 58.9%–85.1%) achieved CR/CRh; morphologic leukemia free state was achieved in 4% (n=2) of pts. Of pts who achieved CR or CR/CRi with a MRD-evaluable sample, 92% (23/25) and 90% (27/30) achieved flow cytometry MRD-negativity (&lt;0.1%) respectively. The most common (≥50% of pts) any grade treatment-emergent adverse events (AEs) were neutropenia/neutrophil count decreased and thrombocytopenia/platelet count decreased (both 69%); constipation (61%); and peripheral edema (51%). Three pts (6%) experienced AEs leading to discontinuation (myocardial infarction/soft tissue infection/thrombocytopenia) and 2 pts had AEs leading to death (respiratory failure/pancytopenia). Conclusions: Unfit pts with newly diagnosed CD123-postive AML demonstrated high CR rates with PVEK+VEN+AZA. These robust response rates were observed across the select mutational profiles tested. Follow up with duration of response and survival estimates among all pts, by molecular subgroups and MRD negativity status, are being evaluated. Triplet therapy in unfit 1L pts with CD-123–positive AML was well-tolerated, and no new safety signals were observed. These data highlight the need to further evaluate this regimen in a randomized trial.