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Background There is limited prospective or comparative data evaluating the HRQoL impact of intensive chemotherapy (IC) in older adults (age ≥60 years) with AML. In the recent EA E2906 phase 3 study of '7&3' (daunorubicin & cytarabine) vs. clofarabine (CLO), a putative lower intensity therapy, we incorporated a prospective patient-reported outcomes (PRO) assessment of HRQoL and fatigue to understand treatment impact from the patients' (pts) perspective. Methods E2906 study design and results have been presented previously [n=727, med. age 68 years (range 60-86), randomized 1:1 to ‘standard’ ‘7&3‘ & high dose cytarabine (Arm A) vs. single agent CLO (Arm B), as remission induction (Step 1) and consolidation (Step 2), respectively]. There was no difference in composite complete remission (CCR, 50%) or 30-day mortality rates (8.5%), and in primary analysis CLO was inferior for Overall Survival. HRQoL was a key secondary protocol endpoint. PROs assessed HRQoL and leukemia-specific symptoms and concerns using Functional Assessment of Cancer Therapy-Leukemia scale (FACT-Leu), & Fatigue using FACT-Fatigue subscale. PROs were administered at prespecified time points: (1) Baseline; (2) Cycle 1 at nadir (approx. Day 15); (3) End of Step 1 restaging (approx. D 40); (4) Beginning of Step 2 (1 st consolidation, approx. D 45); and (5) 2 nd cycle consolidation/End Step 2 (approx. D 60). The FACT-Leu Trial Outcome Index ( TOI) was calculated by summing physical well-being, functional well-being, and leukemia-specific concerns subscales to create a single composite score. Higher TOI scores correspond to better HRQoL. The primary endpoint was to evaluate TOI difference from randomization to day 30 after induction therapy between arms, evaluated using Wilcoxon rank sum test. We also compared Clinically Meaningful differences (CMiD) in TOI (defined as patient change ≥½ standard deviation from baseline TOI) between arms, using the X2 test. Pts not completing at least 2 assessment forms (including baseline) were excluded. Testing of constructs of Physical Well-being (PWB), Functional, Leukemia & Fatigue scales demonstrated high Cronbach's a values (a >0.7) except for PWB (a=0.672) at a single time point (End of Step 2). Results Baseline TOI was available for n=489, and 364 pts (n=182 each Arm) were evaluable in this planned analysis. Evaluating CMiD during Cycle 1 induction, pts in Arm B were less likely to experience ‘Worse’ TOI score (32% vs. 40.7%, Arm A), more likely to maintain stable TOI scores (49.1% vs. 39%, Arm A), and had a similar proportion of ‘Better’ TOI scores (20.3%, A vs. 18.9%, B) although differences were not significant (p=0.1389). Conversely in cycle 1 consolidation, more patients in Arm A experienced Better TOI (45.1% vs. 29.2%, Arm B), fewer had stable TOI (45.1% vs. 58.3%, Arm B), and rates of ‘Worse’ TOI were similar (9.8%, A vs 12.5%, Arm B), again differences were not significant (p=0.2616). There was no difference in Fatigue scores between Arms (p=0.49). We evaluated whether TOI and Fatigue scores could predict the ability to complete protocol therapy. In univariate analysis baseline TOI (p=0.0059) and Fatigue (p=0.0057) were associated with Step 1 completion, however on multivariate analysis (adjusting for age, sex, and Arm) were no longer significant [TOI, Odds Ratio (OR) 1.03 (0.98-1.08, p=0.27); Fatigue, OR 1.03 (0.96-1.11, p=0.42)]. There was a borderline association of TOI with Step 2 completion [TOI OR 1.10 (1.00-1.23, p=0.06)]. Using a multivariable linear mixed effects model, we observed similar and significant changes in TOI scores in both Arms, demonstrating the effect of IC & CLO on HRQoL (Figure). Comparing to baseline, TOI scores decreased significantly at C1 induction nadir (-4.0873, p<0.0001), and increased by 5.0762 (p=0.0004) at end Step 1, by 6.9047 at cycle 1 consolidation (p<0.0001), and by 11.4601 (p<0.0001) at end Step 2. Differences were mainly apparent in those who achieved CCR, and there was significant attrition in PRO responses in non-CCR pts. Conclusions Older adults experienced significant improvement in HRQoL after nadir regardless of therapy, and those achieving CCR report significantly higher scores. We did not observe differences in leukemia specific HRQoL or fatigue between treatment Arms (7&3 vs. CLO). Patient-reported HRQoL & Fatigue was not predictive of completion of protocol therapy. These results serve as a benchmark for expectations with IC in older adults.

Introduction Atrial fibrillation/flutter (Afib) contributes independently to the hematopoietic cell transplant comorbidity index (HCTCI) and is a known complication of allogeneic hematopoietic transplantation (AlloHCT) which has been linked to inferior outcomes, particularly in older patients. An electrocardiogram (ECG)-based artificial intelligence (AI) algorithm to predict Afib and cardiac contractile dysfunction risk has been validated (Lancet 394:861, 2019). We hypothesized that assessment of pre-transplant Afib risk using the AI algorithm may predict future development of Afib and help identify patients at higher risk for this complication. Methods 191 consecutive MDS patients undergoing AlloHCT with curative intent using myeloablative (28.3%) or reduced intensity conditioning (62.3%) in the Mayo Clinic Comprehensive Cancer Center (Rochester, Jacksonville, Phoenix) between November 2015 and January 2022 were included in this retrospective analysis. Primary outcome was Afib within 100 days and 365 days of transplantation, and we also assessed the outcomes of Death and Relapse. Revised IPSS (IPSS-R) and HCTCI scores were included for all patients. Elevated Afib risk score using the AI algorithm was calculated from pre-transplant ECG, performed during vital organ testing at AlloHCT clearance. In addition to left ventricular (LV) ejection fraction (EF) we evaluated detailed echocardiographic (Echo) parameters including LV volume and mass indices, left atrial volume index (LAVI), maximum trans mitral flow velocities during LV filling (E velocity) and during the diastolic phase due to atrial contraction (A velocity), the velocity of the annulus away from the apex during the protodiastolic phase (e' velocity), E/A and E/e' ratios, the presence of valvular disease, and right ventricular systolic pressure (RVSP). We performed an analysis using a Cox proportional hazards regression models (adjusting for age and sex) to evaluate associations with Afib risk, Relapse, and Overall Survival. Results The median age was 64 years (18-75), 58.6% were male, 6.9% non-white race, and 3.7% Hispanic/Latino ethnicity. Most patients had an HCTCI score of 0-3 (76.3%). GVHD prophylaxis was predominantly with calcineurin inhibitor-based regimes plus/minus methotrexate or mycophenolate mofetil (83.8%). 5.2% of patients had a history of Afib before transplant. Non-relapse mortality was 7.9% at 100 days, and 18.3% at 365 days. N=25 patients (13.1%) developed Afib within 100 days, and n=28 (14.7%) within 1-year after AlloHCT. On multivariable analysis, Age [Hazard Ratio (HR) 2.83, 95% Confidence Interval (CI) 1.36-5.89, p=0.0055] and Echo parameters [including LAVI (HR 2.10, CI 1.23-3.58, p=0.0067), E velocity (HR 3.28, CI 1.29-8.80, p=0.013), E/A ratio (HR 3.74, CI 1.75-7.97, p=0.0006), E/e ' ratio (HR 1.81, CI 1.07-3.07, p=0.026) and RVSP (HR 1.68, CI 1.04-2.70, p=0.032)] were significantly associated with Afib risk; elevated AI risk score was significant in the univariate model (HR 2.74, CI 1.15-6.53, p=0.023) but was borderline in the multivariate model (HR 2.34, CI 0.98-5.60, p=0.056) ( Table 1). Based on previous observations we evaluated the association of AI and Echo parameters with Relapse and Death after AlloHCT ( Table 1). Age (HR 1.32, CI 1.01-1.71, p=0.041) and IPSS-R (HR 1.20, CI 1.08-1.33, p=0.0009) were significantly associated with Death after AlloHCT, while HCTCI (HR 1.10, CI 1.00-1.22, p=0.052) and higher LV EF (HR 0.63, CI 0.38-1.06, p=0.084) were borderline. For Relapse, only IPSS-R (HR 1.52, CI 1.31-1.75, p=1.22E-08) was significant, while increase Echo E velocity was of borderline significance (HR 0.45, CI 0.20-1.02, p=0.057). Conclusions Afib is a common post-AlloHCT complication and is more frequent with increasing Age. Echo parameters (specifically E/A ratio) predict significantly higher Afib risk, while the baseline ECG AI algorithm was of borderline significance. The selection of patients with lower HCTCI scores, and the low background prevalence of Afib in this cohort (i.e., selection of patients with lower baseline cardiac morbidity) are possible explanations for non-significance of the AI algorithm. As anticipated Age and IPSS-R are the greatest predictors of Death after AlloHCT, although the suggestion of an association with baseline Echo parameters highlights the importance of identifying those who may benefit from preemptive Cardiology intervention.

Background: Non-transplant treatment options in myelofibrosis (MF) are palliative in scope and include JAK2 inhibitors (JAKi): ruxolitinib, fedratinib, pacritinib, and momelotinib. All four JAKi are effective in reducing spleen size and alleviating symptoms. In addition, pacritinib and momelotinib exhibit erythropoietic effect, attributed to alleviation of ineffective erythropoiesis through inhibition of activin A receptor type-I. In the current study, we sought to identify molecular or clinical predictors of response to pacritinib in MF patients treated outside of clinical trials. Methods: The current study was conducted under an institutional review board approved minimum risk protocol that allowed retrospective collection and analysis of data from patient records (Mayo Clinic, Rochester, MN; Scottsdale, AZ; and Jacksonville, FL). Anemia response assignment was restricted to patients with baseline hemoglobin level of <10 g/dL and required, for transfusion dependent cases, achieving transfusion independence and, for transfusion-independent cases, an increase in hemoglobin of ≥1.5 g/dL, both sustained for a minimum 2 months; spleen response was clinically vetted but was also supported by radiologic imaging when available and required a ≥50% decrease in palpable splenomegaly for spleen size >10 cm or the spleen becoming not palpable for a spleen size 5-10 cm at base line. Symptom response was adjudicated by central review and required a marked or moderate improvement to qualify as response; because of the retrospective nature of the study, symptom burden assessment by formal criteria was not attempted. Leukocyte cutoff level used for response analysis was determined by receiver operating characteristic curve analysis. Conventional statistical methods were applied using JMP Pro 16.0.0 software (SAS Institute, Cary, NC, USA). Results: We identified 36 NGS-annotated patients with MF who received pacritinib therapy between April,2022 and June,2023 (median age 66 years; 56% males). Twenty-five (69%) patients had failed previous JAKi therapy while 11 (31%) were JAKi-naïve. Eighteen (50%) patients were transfusion-dependent while the median (range) counts were 106 x 10(9)/L (14-578) for platelets, 6.6 x 10(9)/L (1.2-112.8) for leukocytes, and 9 x 10(9)/L (5-12.4) for hemoglobin; leukocyte count was ≥15 x 10(9)/L in 11 (31%) patients and hemoglobin <10 g/dL in 29 (81%). Karyotype was unfavorable in 12 (34%) patients. Driver mutation distribution was JAK2 55%, CALR 27%, MPL 11%, and triple-negative 5%. NGS revealed mutations involving ASXL1 36%, U2AF1 13%, IDH1 13%, SF3B1 13%, K/NRAS 5%, SRSF2 8%, and EZH2 5%. Pacritinib was started at 200 mg BID in 9 (25%) patients and at lower doses in the remaining. Median duration of pacritinib therapy was 4 months (range 1-15). Anemia response was documented in 5 (17%) of the 29 patients with baseline hemoglobin <10 g/dL, spleen response in 12 of 28 evaluable (42%) and symptom response in 18 (50%). Improvement in symptoms was always accompanied by both anemia (p=0.008) and spleen (p=0.01) response; by contrast, there was no significant correlation between anemia and spleen responses (p=0.9) (Table 1). Significant correlations with molecular or clinical variables were mostly apparent for spleen response, which was more likely to occur in the absence of ASXL1 mutation (61% vs 10%; p=0.006), with leukocyte count <15 x 10 (9)/L (55% vs 0%; p=0.005), and in JAKi-naïve vs previously-exposed cases (75% vs 30%; p=0.03; Table 1); significance was sustained by all three risk factors during multivariable analysis; the prognostic impact of ASXL1 (p=0.02 vs 0.01) and leukocytosis (p=0.01 vs 0.07) was apparent in both JAKi-naïve vs JAKi-exposed cases. Anemia response was non-significantly (p=0.27) higher in transfusion-independent (27%) vs dependent (11%) cases, at baseline, and was more likely (p=0.04) to occur in patients starting at lower dose levels. Treatment-emergent adverse events included diarrhea 44%, nausea/vomiting 19%, and grade-3/4 thrombocytopenia 38% or neutropenia (11%). Conclusions: ASXL1 mutation and leukocytosis (>15 x 10 9/L) are independently associated with inferior spleen response to pacritinib, in both JAKi-naïve and JAKi-exposed myelofibrosis. These observations are important for individualized treatment selection.

Background: According to the international consensus classification (ICC), diagnosis of myelodysplastic syndromes (MDS) with del(5q) requires presence of i) del5q, alone or associated with no more than one other cytogenetic abnormality, exclusive of -7/del(7q), ii) <5% bone marrow (BM) and <2% circulating blasts, and iii) the absence of “multi-hit” TP53 ( Arber et al. Blood 2022;140: 1200). We have recently reported on TP53 variant allele frequency (VAF) ≥22% being the sole genetic predictor of inferior survival in MDS-del(5q) (Fleti. et al. AJH 2023;98:E76). In the current study, we examined the additional prognostic impact of therapy-related setting, in the context of TP53 VAF and other risk factors. Methods : The current study included patients with MDS-del(5q) who were seen at the Mayo Clinic or Moffitt Cancer Center, USA. Diagnosis of MDS-del(5q) and therapy-related qualification was according to ICC criteria ( Arber et al. Blood 2022;140: 1200), with the exception that patients with biallelic or multi-hit TP53 were included to allow unbiased analysis of impact on prognosis. Patient selection was based on availability of mutation information from next-generation sequencing (NGS). The latter was assessed either at diagnosis or at different time points during the disease course, but at least 3 months before leukemic transformation. Otherwise, all analyses, including estimation of overall and leukemia-free survival, were based on variables collected at time of initial diagnosis of MDS-del(5q). TP53 mutation VAF threshold of 22% was considered based on our previously published report cited above. Age cutoff at 67 years was determined by ROC analysis. Conventional statistical methods were applied using JMP Pro 16.0.0 software (SAS Institute, Cary, NC, USA). Results: A total of 210 patients (median age 72 years; 65% females), meeting the above-stipulated criteria for MDS-del(5q), were considered: 172 primary and 38 therapy-related. Table 1 outlines clinical and laboratory characteristics obtained at the time of diagnosis: 42% were transfusion-dependent, 69% had hemoglobin level <10 g/dL, 30% platelet count <150 x 10(9)/L, and 15% carried additional cytogenetic abnormality. NGS data performed either at diagnosis or at least 3 months prior to leukemic transformation was available in 146 patients; the most frequent mutations were TP53 (21%), SF3B1 (16%), DNMT3A (12%), TET2 (12%), ASXL1 (10%), and JAK2 (7%) (Table 1). At a median follow-up of 3.9 years (range 0.002-18.5) for living patients, 95 (45%) deaths and 34 (16%) leukemic transformations were recorded; treatment undertaken included lenalidomide in 162 (77%) cases. NGS data-exclusive multivariable analysis that included all 210 patients identified therapy-related setting (p<0.01; HR 2.9; Figure 1a), age >67 years (p=0.01; HR 1.8), transfusion-dependency (p=0.04; HR 1.5), and platelet count <150 x 10(9)/L (p=0.03; HR 1.6), as independent predictors of inferior survival. The significant effect of age and platelet count was sustained when analysis was limited to patients with primary MDS-del(5q) but lost when applied to therapy-related disease. NGS data-inclusive multivariable analysis, which was applicable to the subset of 146 patients, identified, as risk factors, therapy-related setting (p<0.01; HR 2.3) and TP53 VAF ≥22% (p<0.01; HR 2.4; Figure 1b) while age >67 years sustained borderline significance (p=0.07; HR 1.8). Figure 1c depicts survival data based on the presence or absence of TP53 VAF ≥22% and therapy-related qualification; low-risk with no risk factors (N=112; median survival 11.7 years; 5/10-year survival 73%/52%) and high-risk with one or both risk factors (N=34; median survival 4 years; 5/10-year survival 42%/14%); leukemia-free survival was affected by TP53 VAF ≥22% (p<0.01) but not therapy-related setting (p=0.13). Conclusions : The current study highlights TP53 VAF and therapy-related setting as the most prominent risk factors for survival in MDS-del(5q) and proposes a simple risk model that distinguishes patients with a projected 10-year survival that exceeds 50%, in the absence of both risk factors, and plummets to 14%, in the presence of one of the two risk factors. Accordingly, allogeneic stem cell transplant might be deferred in the former instance while it should be pursued sooner than later, in the latter instance.

Introduction: Germline DEAD-box RNA helicase-1 mutant (DDX41) predisposition syndrome ( DDX41-MT-GPS) is one of the most frequent hereditary predisposition syndromes in adults with myeloid neoplasms (MN-2-5%). Somatic mosaicism involving the unmutated DDX41 allele (e.g., R525H) as a potential mechanism for myeloid evolution has been reported in 39-50% of patients (pts). In addition, given the later age of onset, somatic mosaic states composed of age-related clonal hematopoiesis (ARCH) (e.g., DNMT3A, ASXL1, TET2, and TP53), with reported frequencies less than expected in MDS and AML, have been documented. We conducted this study to define the somatic mosaic landscape in DDX41-MT-GPS . Methods: After approval from the Mayo Clinic IRB the prospective GPS database was queried for pts with DDX41-MT GPS. Germline confirmation was conducted on skin fibroblast-, or hair follicle-derived DNA. Somatic CH testing was conducted using a targeted NGS panel as previously described. Given the high frequency of variants of undetermined significance (VUS), comparisons were made between pathogenic ( DDX41path) and DDX41VUS. Results: We identified 106 pts with DDX41-MT-GPS, of which 83 (78%) met criteria for MN, 16 (15%) for CH/CCUS (clonal cytopenias of undetermined significance), while 7 (6%) were unaffected carriers. Somatic mosaicism in DDX41-GPS patients without MN Sixteen DDX41-MT pts without MN met criteria for CH/CCUS ( DDX41path [n=4] and DDX41VUS [n=12]; median age 69 years (yrs) (range [R], 19-78) ( DDX41path [69 yrs] and DDX41VUS [67 yrs], p=0.85), with a male predilection (75%). Four (25%) pts had somatic DDX41 MT (R525H [n=3] and A376T [n=1]) with median variant allele frequency (VAF) 10.5% (R, 5-27); 2 (50%) pts with germline DDX41path had R525H (VAF; 5% and 13%) and 1 (8%) pt each with germline DDX41VUS had R525H (VAF 5%) and A376T (VAF 27%) somatic variants, respectively. Abnormal cytogenetics (CG) were observed in 2/13 evaluable (15%) pts ([+8 and del20q]) in the germline DDX41path group only (p= 0.05). ARCH co-mutations were observed in 11 (69%) pts, not significantly (NS) different between DDX41path (75%) and DDX41VUS (75%), p= 0.66. Individual co-mutations: DNMT3A (25% vs 16%, p= > 0.99), ASXL1 (25% vs 8%, p=0.71), TET2 (25% vs 8%, p= >0.99), and JAK2 (0% vs 8%, p= >0.99) were NS different between the two groups. Somatic mosaicism in DDX41-GPS patients with MN Eight-three pts met criteria for MN ( DDX41path [n=43] and DDX41VUS [n=40]; median age 67 yrs (range [R], 27-92), with a male predilection (58%). Fifty-four (65%) pts had MDS ( DDX41path [55%] and DDX41VUS [45%], p=0.55) and 29 (35%) had AML ( DDX41path [41%] and DDX41VUS [59%], p=0.65). Overall, 15 (18%) pts had somatic DDX41 MT; 12 (80%) pts with DDX41path and 3 (20%) pts with DDX41VUS (p= 0.003). The median VAF of somatic DDX41 MT was 12% (R, 5-37), NS different between DDX41path (10.5%) and DDX41VUS (12%) (p=0.08). The most common somatic DDX41 MT was R525H (66% [n=10]), significantly associated with DDX41path (9/10 [90%]), p=0.01. ARCH was observed in 17 (20%) pts, significantly higher in DDX41path (76%) compared to DDX41VUS (24%), p= 0.03. Abnormal CG were observed in 10/73 evaluable (14%) pts (-Y [n=2], del 20 [n=3], del 5q [n=2], del 7q [n=1], t (3;8) [n=1] and complex CG [n=1]), higher in DDX41path (70%) compared to DDX41VUS (30%) with p value >0.99. We compared the spectrum of CH between DDX41 MT CH/CCUS and MN pts ( Table 1) and found no difference in the proportion of pts with somatic DDX41 MT (p= 0.52) and ARCH/myeloid MT (p= 0.56). The individual occurrences of DNMT3A (p= 0.49), ASXL1 (p= 0.71), TET2 (p=0.59), JAK2 (p>0.99) and TP53 (p= 0.56) mutations were NS different between the two groups ( Figure 1). Conclusion: We define the somatic mosaic landscape in DDX41-MT GPS and demonstrate that somatic mutations involving the other allele, especially R525H, are seen in ~20% of pts (>80% of R525H present in MN). The frequency and composition of ARCH and myeloid driver mutations was lower than expected for the age of presentation, in comparison to de novo and secondary MDS/AML and occurred more frequently in DDX41path compared to DDX41VUS. Forty-two % (n=41), including 37% with MN, did not have somatic mosaicism, underscoring the fact that mechanisms of leukemia progression remain to be defined in subsets of affected pts.

BACKGROUND: Recently proposed World Health Organization (WHO, 5 th edition) and International Consensus Classification (ICC) recognized myeloid neoplasms (MN) harboring TP53-mutated ( TP53mut) as a separate entity. However, there are critical differences between the two classifications regarding allelic-status, variance allele frequency (VAF) cut-off and blast categories, that may lead to under- or overestimation of the risk. METHODS: We analyzed MN harboring TP53mut (VAF ≥2%, n=536) managed at Mayo Clinic (USA) and South Australia Health Network (Australia). ICC (Arber et al, Blood 2022) and WHO (Bluebook, Beta v2) definitions were used to stratify MN harboring TP53mut. RESULTS: Of 536 cases, 379 (71%) had myelodysplastic syndromes (MDS) (<20% blasts) and 157 (29%) had acute myeloid leukemia (AML). Using WHO, 160 (42%) of 379 were classified as MDS-bi TP53 as they harbored 2 TP53mut (n=115; 30%) or 1 TP53mut plus confirmed loss of heterozygosity (LOH) or copy neutral LOH (cnLOH) of TP53 locus (n=45; 12%). Sixty-two (16%) TP53mut MDS with VAF >49% were classified as presumptive MDS-bi TP53. Of the 157 cases with 1 TP53mut VAF ≤49%, 17 confirmed to have an intact wild-type TP53 copy and were classified as monoallelic. While 140 (89%) cases did not have copy number variation (CNV) analysis. We next evaluated the number of TP53mut cases classified differently by WHO and ICC. As WHO does not recognize TP53mut AML as a separate entity, 157 (29%) TP53mut AML were not classifiable. 46% (174/379) of the TP53mut MDS including 48 (30%), 12 (19%) and 79 (65%) of bi TP53, presumptive bi TP53 and monoallelic TP53mut MDS according to WHO were classified differently by ICC ( Figure 1A). Discordance between the two classifications were predominantly driven by: (i) The difference in VAF cut-off. Sixty patients (11%) with TP53mut VAF <10% were excluded from the ICC classification of TP53mut MN as it mandates TP53mut VAF cut-off ≥10%. 11 (18%) and 41 (68%) of these had bi TP53, monoallelic TP53mut MDS by WHO criteria while 8 (13%) had AML. Importantly, within the VAF <10% cohort, median overall survival (OS) of 2 TP53mut or 1 TP53mut with 17p13.1 (hereafter 17p) deletion or complex karyotype (CK, n=30) was significantly poor compared to 1 TP53mut VAF <10% (11.6 vs 32.4 months; P =0.002, Figure 1B), suggesting that ICC may underestimate the poor prognosis of multi-hit or multi-hit equivalent TP53mut MN with VAF <10%. (ii) The difference in bone marrow blast cut-off. The underlying assumption by WHO is that prognosis of bi TP53mut MDS is poor irrespective of blast percentage category (0-9% vs 10-19%). In contrast, ICC considers that TP53mut MDS/AML (blasts 10-19%) is associated with poor prognosis irrespective of TP53 allelic status. Median OS of TP53mut MDS with 10-19% blasts was significantly poor compared to blast 0-9% (6.4 vs 11.6 months, P <0.0001). Second, median OS of bi TP53mut was significantly poor than monoallelic TP53mut in MDS- blast 0-9% (10.1 vs 15.9 months; P =0.0001) but not in blasts 10-19% (6.8 vs 6.2 months; P =0.19). Hence, exclusion of monoallelic TP53mut MDS with blast 10-19% as TP53mut MN from the WHO classification may underestimate the poor prognosis. (iii) The difference in the definition of biallelic and multi-hit TP53 loss. 35 cases with 1 TP53mut VAF ≤49%, had 17p deletion but did not have CNV analysis to confirm the loss of TP53 locus and could not be classified further using WHO. ICC classified 18 (50%) of these cases as multi-hit. Median OS of 1 TP53mut VAF ≤49%, and 17p deletion on karyotype was significantly poor than 1 TP53mut (VAF ≤49%without 17p deletion on karyotype (6.4 vs 14.6 months, P =0.001). (iv) The difference in the definition of multi-hit equivalent. 32% (33/104) WHO defined monoallelic cases without available CNV data, were classified as multi-hit-equivalent by ICC as they harbored CK. However, WHO does not consider CK as presumptive evidence of bi TP53. Median OS of 1 TP53mut VAF ≤49% with CK was significantly poor compared to 1 TP53mut without CK (8.2 vs 26.9 months, P =0.0008). CONCLUSION: Our study provides evidence that poor prognosis of ‘multi-hit’ TP53 with VAF <10% is underestimated by ICC. On the other hand, poor prognosis of monoallelic TP53 MDS with 10-19% blasts as well as 1 TP53mut VAF ≤49% in the presence of CK is underestimated by WHO. These data suggest that both classifications can be further refined.

Abstract Enasidenib (ENA) is an inhibitor of isocitrate dehydrogenase 2 (IDH2) approved for the treatment of patients with IDH2-mutant relapsed/refractory acute myeloid leukemia (AML). In this phase 2/1b Beat AML substudy, we applied a risk-adapted approach to assess the efficacy of ENA monotherapy for patients aged ≥60 years with newly diagnosed IDH2-mutant AML in whom genomic profiling demonstrated that mutant IDH2 was in the dominant leukemic clone. Patients for whom ENA monotherapy did not induce a complete remission (CR) or CR with incomplete blood count recovery (CRi) enrolled in a phase 1b cohort with the addition of azacitidine. The phase 2 portion assessing the overall response to ENA alone demonstrated efficacy, with a composite complete response (cCR) rate (CR/CRi) of 46% in 60 evaluable patients. Seventeen patients subsequently transitioned to phase 1b combination therapy, with a cCR rate of 41% and 1 dose-limiting toxicity. Correlative studies highlight mechanisms of clonal elimination with differentiation therapy as well as therapeutic resistance. This study demonstrates both efficacy of ENA monotherapy in the upfront setting and feasibility and applicability of a risk-adapted approach to the upfront treatment of IDH2-mutant AML. This trial is registered at www.clinicaltrials.gov as #NCT03013998.

SummaryVenetoclax (VEN) is an FDA‐approved selective inhibitor of B‐cell leukaemia/lymphoma‐2 (BCL‐2), used for treating elderly or unfit acute myeloid leukaemia (AML) patients unable to undergo intensive chemotherapy. Combining VEN with hypomethylating agents (HMAs) has shown impressive response rates in high‐risk myelodysplastic syndromes (MDS) and relapsed/refractory AML. However, the efficacy of VEN and HMAs in treating DDX41‐mutated (mDDX41) MDS/AML patients remains uncertain. Despite the favourable prognostic nature of mDDX41 MDS/AML patients, there is a lack of clinical experience regarding their response to different treatment regimens, leading to an unknown optimal therapeutic approach.