Mangaonkar, Abhishek A.

Background: The 2022 European LeukemiaNet (ELN) genetic-risk stratification for acute myeloid leukemia (AML), assigns favorable prognosis to t(8;21)(q22;q22.1)/ RUNX1:: RUNX1T1, inv(16)(p13.1q22) or t(16;16)(p13.1;q22)/ CBFB:: MYH1, NPM1 mutations without FLT3-ITD or adverse karyotype, and bZIP in-frame CEBPA mutations (Döhner , Blood, 2022 ). This risk stratification was derived from intensively treated patients; accordingly, prognostication in ELN favorable genetic risk AML, following venetoclax and hypomethylating agent (VEN-HMA) therapy, remains unclear and was the subject of the current study. Methods: Under an institutional review board approved minimum risk protocol, the Mayo Clinic database was searched to identify AML patients with favorable genetic risk, who received treatment with VEN-HMA in the frontline setting. All patients received at least one cycle of either azacitidine 75 mg/m 2 days 1-7 or decitabine 20 mg/m 2 days 1-5 with VEN dose adjusted based on azole antifungal prophylaxis. Genetic risk stratification and treatment response were assessed according to the 2022 ELN criteria. Survival was estimated from the time of VEN-HMA treatment start to last follow-up or death. Results: Patient characteristics A total of 46 newly-diagnosed AML patients with ELN 2022 favorable genetic risk [ NPM1 mutation, n=36 (78%), CEPBA bZIP mutation, n=7 (15%) and t(8;21)(q22;q22.1)/ inv(16)(p13.1q22), n=4 (9%)] received a median of 4 cycles (range 1-32) of VEN-HMA. Median age was 71 years, with 63% males, and 87% de novo AML. Additional mutations frequently involved TET2 in 17/43 (40%), DNMT3A in 14/45 (31%), SRSF2 in 10/43 (23%), K/NRAS in 10/45 (22%), IDH1 in 8/46 (17%), FLT3-TKD in 7/46 (15%), ASXL1 in 6/43 (14%) and IDH2 in 6/46 (13%),of informative cases.Myelodysplasia (MDS)-related gene mutations ( ASXL1, RUNX1, BCOR, EZH2, SRSF2, U2AF1, SF3B1, STAG2, and/or ZRSR2) were present in 15 of 40 (38%) of patients (93% males). Predictors of response Of the 39 (85%) patients that achieved complete remission, with (CR) ( n=24; 52%), or without count recovery (CRi) ( n=15; 33%); CR/CRi rates were not significantly higher in patients with NPM1 mutations (89%), t(8;21)(q22;q22.1)/ inv(16)(p13.1q22) (75%), or CEPBA bZIP mutations (67%) ( p=0.37). Among patients achieving CR/CRi, measurable residual disease by multiparametric flow cytometry was negative in 15 of 16 (94%) of evaluable cases after cycles 1 or 2. In addition, NPM1 qPCR was negative in 15 of 24 (63%) informative patients. Median time to response was 1.2 months with median response duration of 9.4 months. CR/CRi rates were significantly higher in females vs males (100% vs 76%, p=0.01), and in the absence vs presence of MDS-related gene mutations (96% vs 60%, p=0.004). Multivariable analysis confirmed superior response in the absence of MDS-related gene mutations ( p=0.04). Predictors of survival At a median follow-up of 10.6 months (range; 1.1-51 months), 21 patients (46%) have died, 9 relapsed (23% of those achieving CR/CRi), and 6 (13%) underwent allogeneic hematopoietic stem cell transplant. Median overall survival was 21 months with 1/2/3-year survival rates of 65%/41%/41% (Figure 1a); median relapse-free survival (RFS) was not reached; 1/2/3-year RFS rates were 81%/66%/57% (Figure 1b). Overall survival was superior in patients achieving CR/CRi (23 months vs 5.6 months; p<0.01), in females vs males (not reached vs 9.7 months; p<0.01), and in the absence of MDS-related gene mutations (not reached vs 5.6 months; p=0.01) (Figure 1c). Subsequent multivariable analysis identified female gender ( p=0.01), and absence of MDS-related mutations ( p=0.17) as independent predictors of superior survival. Similar results were obtained when analysis was restricted to NPM1 mutated patients. Conclusions: In the current retrospective study, VEN-HMA therapy in elderly/unfit AML patients with ELN 2022 favorable genetic risk, resulted in response rates that were comparable to those previously appreciated from published reports of patients receiving intensive induction therapy; however, follow-up in the current study was too short to accurately assess long-term overall and relapse-free survival impact. Our study also highlights the adverse prognosis retained by MDS-related gene mutations.

Introduction and background Key factors that relate to worse quality of life (QoL) in acute leukemia patients were identified in a global survey conducted by the Acute Leukemia Advocates Network (ALAN) such as age, gender, socioeconomic state, social functioning (e.g., worries about family and friends, feeling isolated, finances, etc.[ Pemberton-Whiteley et al, 2023]). These factors should be taken into consideration by healthcare professionals caring for acute leukemia patients to enable a robust support system. The role of patient organizations (PO) in the care of the patient and family is becoming increasingly important, however, patients are often not aware of the existence of POs and physicians and providers are often unsure of the role and benefits of PO, which then leads to a delay in patients reaching out to POs (for information, education resources, support resources [support groups, online chat, peer-to-peer support, financial support, psychological support, carer support], etc.). To date, there is limited evidence showing the importance of support offered to patients and their families. The ALAN, the Mayo Clinic and a national PO, are conducting a study that aims to assess both retrospectively and prospectively the benefits of active referrals to PO for patients with acute leukemia. Hypothesis We hypothesize that active referrals of adult patients with acute leukemia to PO at diagnosis has a positive impact on patient-reported outcomes and patient experience. Methods Here we present the study methodology that uses a quantitative method via administration of surveys at different timepoints. We plan to do both a retrospective and prospective evaluation of patients (target N=200) previously referred and new patients with a diagnosis of acute leukemia. There are 4 scenarios which are presented in Figure 1. For patients already diagnosed and evaluated at Mayo Clinic (scenarios 3 and 4), we will contact them either via email or portal message to see if they are interested in the study. A study consent form will be sent to them. If they indicate interest and consent, they will be contacted to understand whether they were referred to or sought help from PO around the time of their diagnosis or subsequently, and a questionnaire will be sent to them to assess if PO services helped them in their disease or treatment course. For newly diagnosed patients (scenarios 1 and 2), active referral to PO using PO referral online form will be provided and they will receive study consent form during their first visit at Mayo Clinic. A questionnaire will be sent to them to understand if they used the services from PO after the referral and if yes, to assess if PO services helped them in their disease or treatment course. In addition, every month from diagnosis up to 6 months, all patients who consented to take part in the study will be asked to complete the validated HM-PRO QoL assessment tool (an instrument designed to measure patient-reported outcomes in those with hematological malignancies), to assess QoL and symptoms and change over time. Conclusion This is a pilot study aiming at building evidence on the importance of support offered to patients and their families and demonstrating the impact of an active referral at diagnosis. 1 Pemberton-Whiteley Z, Nier S, Geissler J, Wintrich S, Verhoeven B, Christensen RO, Salek S, Oliva EN, Ionova T, Bradley J. Understanding quality of life in patients with acute leukemia, a global survey. J Patient Cent Res Rev. 2023;10:21-30

Background Venetoclax (Ven) in combination with hypomethylating agent (HMA) is the standard treatment for newly diagnosed elderly/unfit patients with acute myeloid leukemia (AML). Treatment options for patients with relapsed/refractory (RR) disease following Ven-HMA are limited in the absence of targetable mutations. In a recent phase 2 study, the addition of Ven to cladribine (CDA) plus low-dose cytarabine (LDAC), in newly-diagnosed elderly/unfit AML, resulted in complete remission with (CR) or without (CRi) count recovery rate of 93% ( J Clin Oncol 20;40(33)). In the current study, we share our experience with this regimen in patients relapsed or refractory to Ven-HMA, treated outside of clinical trials. Methods Under an institutional review board approved minimum risk protocol, the Mayo Clinic (MN, AZ, FL) database was searched to identify patients with AML who failed treatment with Ven-HMA and subsequently received at least one cycle of salvage therapy with Ven-CDA-LDAC: Ven 100-400 mg, dose adjusted, d1-21, CDA 5 mg/m 2 d1-5, LDAC 20 mg twice daily d1-10, outside of clinical trials. Cytogenetic and molecular studies were performed at the time of Ven-CDA-LDAC initiation in most cases, by conventional karyotype and next-generation sequencing, respectively. The 2022 European LeukemiaNet (ELN) criteria were applied to define risk and response. Survival was calculated from the time of Ven-CDA-LDAC treatment start to last follow-up or death. Results Patient characteristics A total of 39 RR AML patients (median age 65 years, 67% male, 64% de novo), with prior exposure to Ven-HMA, received Ven-CDA-LDAC (median 1 cycle; range 1-5). Study patients had received one ( n=16), two ( n=14), three ( n=5), four ( n=2), five ( n=1) or nine ( n=1) prior therapies, including Ven-HMA. Nine (23%) patients had relapsed following allogeneic hematopoietic stem cell transplant (AHSCT). ELN cytogenetic risk included intermediate (46%, n=18), and adverse (54%, n=21). Mutations involved TP53 in 9 patients (23%), K/ NRAS in 8 (21%), RUNX1 in 7 (18%), TET2 in 6 (15%), ASXL1 in 5 (13%), and STAG2 in 5 (13%). Response and toxicity Eleven (28%) patients achieved CR ( n=2; 5%) or CRi ( n=9; 23%); median time to response was 1 month and median response duration 3.4 months. In addition, 2 (5%) patients each experienced partial remission (PR) and bone marrow aplasia without fulfilling criteria for morphologic leukemia free state. Measurable residual disease (MRD) was negative by multiparametric flow cytometry in 2 of 7 (29%) informative CR/CRi cases. CR/CRi rates were higher in females (54% vs 15%; p=0.01), de novo vssecondary AML (40% vs 7%; p=0.02), and absence of adverse karyotype (50% vs 9%; p<0.01), K/NRAS (35% vs 0%, p=0.01), ASXL1 (32% vs 0%, p=0.05), or STAG2 mutations (32% vs 0%, p=0.05) (Table 1). Multivariable analysis confirmed superior response in de novo AML (p<0.01), absence of adverse karyotype, (p<0.01), and absence of K/NRAS mutations (p=0.02). CR/CRi rates were not significantly affected by relapsed vs refractory setting ( p=0.95), number of prior therapies ( p=0.51), prior AHSCT ( p=0.64), or TP53 mutations ( p=0.64) (Table 1). Treatment-emergent toxicities included infections (49%, n=19), comprising bacteremia ( n=11), pneumonia ( n=10), peri-rectal abscess ( n=6), and laboratory evidence of tumor lysis syndrome (3%, n=1). Survival At a median follow-up of 3.9 months, from initiation of Ven-CDA-LDAC, 31 deaths (79%), 6 relapses (15%), and 7 AHSCT (18%; including 5 in CR/CRi, 1 in aplasia) were documented. Median survival following Ven-CDA-LDAC was 4.6 months, and superior in the presence vs absence of CR/CRi (8.1 vs 2.9 months; p=0.01), and in patients receiving AHSCT (10.5 vs 3.4 months; p=0.02). Absence of adverse karyotype was also associated with superior survival (6 vs 3.4 months; p=0.05). Multivariable analysis confirmed the favorable survival impact of CR/CRi ( p=0.03) and AHSCT ( p=0.05); survival impact was not apparent for secondary AML ( p=0.29) or K/NRAS ( p=0.70) or TP53 ( p=0.10) mutations. Conclusions The current study suggests transplant bridging value for Ven-CDA-LDAC in AML patients relapsed or refractory to Ven-HMA, especially in the absence of adverse karyotype or K/NRAS mutation. AHSCT and achievement of CR/CRi appear to be indispensable for favorable post-Ven-CDA-LDAC survival.

INTRODUCTION: The Stromal Antigen 2 ( STAG2), on Xq25, is the most common cohesin complex gene mutated in myeloid neoplasms (MN) (5-10%). STAG2 mutations ( STAG2m) were incorporated in the ELN2022 as AML-MDS defining genetic mutations inferring poor prognosis and is a genetic marker in IPSS-M risk stratification. The PHD-finger protein 6 ( PHF6) gene, on Xq26.3, is a tumor suppressor gene, mutated in 3% of MN, and is more common in T-ALL. PHF6m is believed to be a late event in MN with little data on its prognostic implications in MN. Both STAG2m and PHF6m are more prevalent in males, but their implications on the clinical presentation of MN have not been compared prior. METHOD: Our study is a multicenter study at Mayo Clinic (Rochester, Florida, Arizona). After IRB approval, we retrospectively analyzed charts of 7935 patients who had NGS between 2016-2022. STAG2m was found in 96 patients, and PHF6m in 116 (including 3 with concurrent STAG2m and PHF6m). We excluded 4 PHF6m patients who had T-ALL. Data was captured at time of NGS. MDS risk stratification was by IPSS-M and AML by ELN2022. Overall survival (OS) was calculated from date of NGS to date of last follow-up. BlueSky Software was used for statistical analysis. RESULTS: Characteristics: We compared 96 STAG2m vs 112 PHF6m MN patients. Of STAG2m cases, 78% were male vs 76% in PHF6m MN. Median age was 72 vs 73 years, respectively. Diagnoses included AML (29% of STAG2m vs 34% of PHF6m MN), MDS (54% vs 28%), MDS/MPN (10% vs 21%) and MPN (3% vs 9%). MDS was more common among STAG2m MN (p<.001) while MDS/MPN was more common among PHF6m MN (=.05). MDS-IB was the most common subtype in both (69% vs 52% in STAG2m vs PHF6m MDS). MDS-LB and 5q subtypes were only found in PHF6m MDS, and there was more PHF6m MDS-RS (13% vs 2%). Median IPSS-M score was 0.9 vs 0.8 in STAG2m vs PHF6m MDS (both high-risk). Majority of STAG2m AML were adverse risk (96%) while PHF6m AML were intermediate (79%) (p<.001). AML cases included 43% vs 30% secondary AML (sAML) in STAG2m vs PHF6m AML. Among STAG2m and PHF6m MN, 17% of each were tMN. Cytogenetic abnormalities were more common in PHF6m MN (50% vs 31%, p=.005). The median bone marrow (BM) blasts count among STAG2m MN was 7% vs 4% in PHF6m MN (p=.03). Genetic characteristics: STAG2m were nonsense, frameshift and splice site (54%, 36% and 11%). PHF6m were nonsense, frameshift, splice site, missense and start loss variant mutations (44%, 33%, 12%, 10% and 1%). The median variant allele frequency (VAF) of STAG2m MN was 50% compared to 32% in PHF6m MN (p=.008). Co-mutations: The median number of co-mutations was 3 in STAG2m and 4 in PHF6m MN (p=.04). The most common were TET2m (37% in STAG2m MN vs 45% in PHF6m MN), RUNX1m (31% in both), SRSF2m (39% vs 20%), ASXL1m (66% vs 38%), BCORm (19% vs 6%), U2AF1m (13% vs 14%) and IDH2m (18% vs 7%). ASXL1m, SRSF2m, BCORm, IDH2m and SF3B1m were more common among STAG2m MN (p=<.001, .003, .006, .02, .09). JAK2m, IDH1m are more common among PHF6m MN (p=.02, .06). Survival: Of STAG2m and PHF6m MN, 70% and 72% of patients received treatment. HSCT was performed in 23 (24%) and 23 (21%) of STAG2m and PHF6m patients, including AML (n=9, n=10), MDS (n=12, n=8), MDS/MPN (n=2, n=2). OS among STAG2m and PHF6m MN was 20.5 and 22.1 months, respectively. OS among AML cases was 13.5 vs 21 months (p=.6) in STAG2m vs PHF6m, was NR vs 22 months (p=.4) in MDS, 11.7 vs 17.6 months in MDS/MPN (p=.4), and 10.4 vs 27.4 months (p=.5) in MPN. There was no difference between males and females in either STAG2m or PHF6m MN. HSCT led to longer OS among both STAG2m (NR vs 19.9 months, p=.01) and PHF6m MN patients (NR vs 17.6 months, p=.07). Among AML patients, HSCT did not significantly impact OS (18 vs 9.6 months, p=.3 and 25.1 vs 21 months, p=.2, in STAG2m and PHF6m). HSCT improved OS in STAG2m MDS (NR vs 20.5 months, p=.03). In PHF6m MDS, OS was 22.1 vs 13.1 months in HSCT vs non-HSCT (p=.3). CONCLUSION: STAG2m and PHF6m are 2 X-linked mutations that occur in MN. Both commonly occur in elderly males. MDS was the most common diagnosis in STAG2m MN. STAG2m co-occurred particularly with SRSF2m ASXL1m and BCORm, which are associated with poor prognosis. In our cohort, STAG2m AML carried a poorer prognosis than PHF6m AML. Our study confirms the ELN2022 AML risk stratification. MDS risk classification and OS did not differ between STAG2m and PHF6m in our cohort. A larger cohort is required to confirm our findings and may provide stronger validation.

Introduction Chronic myelomonocytic leukemia (CMML) can be classified into dysplastic (dCMML) and proliferative (pCMML) subtypes based on a white blood cell count (WBC) ≥ 13 x 10 9/L for pCMML. Though this cutoff may seem arbitrary, there is evidence that pCMML is a unique biological entity with a distinct molecular profile and worse outcomes (Carr RM, et al. Nat Commun. 2021). We hypothesized that contemporary CMML prognostic scoring systems - such as the Mayo Molecular Model (MMM; Patnaik MM, et al. Leukemia. 2014) and the CPSS-Molecular Model (CMM; Elena C, et al. Blood. 2016) - would not adequately risk-stratify pCMML patients. Moreover, while truncating ASXL1 mutations are considered a high-risk feature in CMML, their prognostic relevance in pCMML is unknown. Methods After IRB approval, we compiled a large (n = 888), molecularly-annotated database of CMML patients seen at two US medical centers (Mayo Clinic and MD Anderson) via retrospective chart review. All statistical analyses considered the clinical and laboratory parameters obtained at the time of presentation. The cohort was divided into dCMML and pCMML subgroups, which were analyzed independently alongside the entire cohort. Categorical variables were compared by Fisher exact or Pearson χ 2 tests and continuous variables by Mann-Whitney U tests. Univariate and multivariate analyses were performed using Cox proportional hazards regression models. Survival was assessed via the Kaplan-Meier method. P-values < 0.05 were considered significant. Calculations were performed using the BlueSky Statistics (v10.3.1) interface for R. Results We identified 474 (54%) dCMML cases and 410 (46%) pCMML cases with median age 71 years and 67% males. Patients with pCMML were more likely to have higher AMC (5.1 vs 1.5 x 10 9/L, p < 0.0001), circulating immature myeloid cells (IMC; 65% vs 36%, p < 0.0001) and abnormal karyotypes (37% vs 30%, p = 0.0187). They were also overrepresented in higher-risk categories of the MMM and CMM compared to dCMML (p < 0.0001 for each model). The number of somatic mutations was higher in pCMML than dCMML (mean 3.0 vs 2.6, p = 0.0050). Mutations in ASXL1 (53% vs 39%), NRAS (21% vs 11%), CBL (18% vs 12%), SETBP1 (14% vs 7%), JAK2 (10% vs 3%), CEBPA (5% vs 2%), GATA2 (3% vs 0%), and FLT3 (3% vs 1%) were more frequent while mutations in TET2 (38% vs 48%), SF3B1 (2% vs 8%), ZRSR2 (2% vs 8%), and NPM1 (1% vs 3%) were less frequent in pCMML compared to dCMML, respectively (p < 0.05 for all). Though the MMM and CMM effectively stratified the dCMML group, they did not provide meaningful risk stratification in the pCMML group (MMM p < 0.05 overall but could not distinguish between low and intermediate-1/2 or intermediate-1 and high risks; CMM p > 0.05). Likewise, there was no difference in the median overall survival (OS) or leukemia free survival (LFS) when pCMML patients were stratified by truncating ASXL1 mutations( Figure 1A). We then sought to better risk stratify pCMML. Univariate analysis identified increasing age, male gender, abnormal karyotype, and elevated WBC, ANC, and AMC as adverse predictors for OS. In addition, the presence of IMC and peripheral blood (PB) blast % were adverse factors for LFS, while age was not significant for LFS. None of the aforementioned mutations were significant in the univariate model for OS, whereas GATA2 and NPM1 mutations were significant for LFS. In multivariate analysis for OS, only male gender and AMC ≥ 10 x 10 9/L retained significance. In multivariate analysis for LFS, male gender, AMC ≥ 10 x 10 9/L, and peripheral blasts ≥ 5% remained significant; GATA2 and NPM1 mutations were not significant. These variables risk-stratified pCMML patients based on the presence of 0, 1, or ≥ 2 risk factors ( Figure 1B). In comparison, OS was 40.7 months (95% CI 35.2 - 50.1 mo.) for dCMML patients, 20.1 months (95% CI 18.2 - 22.7 mo.) for pCMML patients, and 31.8 months (95% CI 28.4 - 33.5 mo.) for the entire cohort. At last follow up, 586 deaths (66%) and 168 AML transformations (19%) were recorded in the cohort. Deaths in dCMML vs pCMML were 294 (62%) vs 291 (71%; p = 0.0067), with AML transformations in 83 (18%) vs 84 (21%; p = 0.2055) patients, respectively. Conclusions Truncating ASXL1 mutations, along with ASXL1-mutation weighted CMML prognostic models failed to effectively risk stratify pCMML patients. In pCMML, male gender and AMC ≥ 10 x 10 9/L, effectively risk stratified for OS, while these factors along with PB blasts ≥ 5% effectively risk stratified for LFS.

Introduction: Chronic myelomonocytic leukemia (CMML) is a myeloid neoplasm with limited therapeutic options and dismal outcomes. Truncating mutations in the epigenetic modifier ASXL1 are common and lead to a proliferative disease phenotype, resistance to epigenetic therapies, and higher rates of AML transformation. ASXL1-mutant CMML is characterized by widespread epigenetic remodeling and up-regulation of key leukemogenic driver genes (e.g. HOXA9 and its co-factor MEIS1). There is a genotype-specific activation of enhancers in ASXL1-mutant CMML that is associated with up-regulation of these leukemogenic driver genes. Here, we test the hypothesis that disrupting the oncogenic interactions at these genotype-specific enhancers can be exploited for therapeutic benefit. Methods: We identified activated enhancers specific to ASXL1-mutant CMML as previously described ( Binder et al. Nat Commun 2022;13(1):1434). To disrupt the E2542605 enhancer, we created unique mapped single guide RNAs (confirmed by BLAT). We generated a ribonucleoprotein complex using the Alt-R CRISPR-Cas9 system (IDT Technologies, Coralville IA). We combined the RNP along with Electroporation Enhancer to 3x10^5 cells of the monocytic cell line U937 in 20uL strip-wells provided by the SF Cell Line 4D-Nucleofector X Kit (Lonza, Basel, Switzerland). To deliver the RNP, U937 cells were electroporated via listed cell line specific protocol by the Amaxa 4D-Nucleofector (Lonza). Forty-eight hours post-electroporation, cells were split and sequenced for E2542605 genomic structure disruption. In parallel, RNA was harvested, converted to cDNA and qPCR for HOXA9 and MEIS1 expression was performed using PrimeTime qPCR FAM labeled probe assays (IDT). Gene expression was determined using delta-delta Ct method. For assessment of selective sensitivity of ASXL1 / enhancer interactions, we performed progenitor colony forming assays using primary bone marrow mononuclear cells from CMML patients with or without ASXL1 mutations and healthy normal controls (n=2 in each category), exposed to increasing concentrations of the dual p300/CBP and BET bromodomain inhibitor EP31670. Briefly, we plated cells in methocellulose fortified with recombinant human cytokines supporting hematopoietic growth in duplicate, in a range of EP31670 concentrations. After 10 days, visible hematopoietic colonies were quantified and characterized. IC 50 values were generated using non-linear regression log(EP31670) vs. normalized response. Results: We computationally identified candidate transcriptional regulators enriched at the activated enhancers specific to ASXL1-mutant CMML, including BRD4 (FDR<2.57x10 -370), CBP (FDR=2.56x10 -217), and p300 (FDR=6.36x10 -93). We selected the ASXL1-mutant-specific enhancer E2542605 (predicted to drive HOXA9 expression), given the up-regulation of HOXA9 in ASXL1-mutant CMML (log 2-fold change +2.05, FDR=0.006, n=14). We disrupted E2542605 using two different CRISPR guides, leading to a PCR trace detection of a 14bp deletion and a 26bp indel in the E2542605 enhancer region, respectively. Both enhancer disruptions led to a down-regulation of its putative target gene HOXA9: Mean relative fold-change 0.36 (p=0.001, n=3) and 0.65 (p=0.046, n=3), respectively ( Fig. 1a). We then used a pharmacologic approach (EP31670) to target the candidate transcriptional regulators involved in the oncogenic interaction at these ASXL1-mutant-specific enhancers. We observed selective sensitivity to growth of CMML colonies (particularly ASXL1-mutant colonies) compared to ASXL1-wild type cases and normal bone marrow controls ( Fig. 1b). Conclusions: In CMML patients, truncating ASXL1 mutations are associated with the activation of genotype-specific enhancers and the recruitment of an extended repertoire of transcriptional regulators including BRD4, CBP, and p300. In a model system, the disruption of an enhancer predicted to govern the expression of the leukemogenic driver HOXA9, led to a significant down-regulation of HOXA9 expression. Pharmacologically disrupting the oncogenic interaction at such enhancers with EP31670 in primary patient samples led to significant therapeutic effects at nanomolar drug concentrations in a genotype-specific manner. Oncogenic interactions at activated enhancers are viable therapeutic targets in ASXL1-mutant CMML and warrant further clinical investigation.

INTRODUCTION Telomere biology disorders (TBDs) are multisystem diseases caused by accelerated telomere shortening that can present with bone marrow failure and pulmonary fibrosis, among other abnormalities. TBD diagnosis is considered when average blood telomere length (TL) measured by clinical flowFISH is <1 st percentile and/or a pathogenic variant in telomere maintenance genes (most commonly TERT, TERC, RTEL1) is identified. Pathogenic variants in genes coding for the telomerase protein ( TERT) and RNA component ( TERC) decrease telomerase activity. Similarly, variants in RTEL1 result in defective unwinding of the t-loop at telomere ends, increasing the levels of free t-circles in cells. Variants in these genes are often classified as variants of uncertain significance (VUSs by ACMG criteria) with additional efforts needed for variant curation. To address this, we describe results of functional testing performed in TBD patients with VUSs involving TERT, TERC, and RTEL1. METHODS TBD suspected patients were identified through the Pre-Myeloid Cancer and Bone Marrow Failure Clinic (Mayo Clinic) where they underwent clinical flowFISH and genetic testing for TBD related genes. Informed consent was obtained with approval from the Mayo Clinic Institutional Review Board. Viable peripheral blood and bone marrow samples were collected along with age matched healthy volunteers. Telomerase activity was measured in samples with TERT and TERC variants through telomeric repeat amplification protocol (TRAP) assays using the TRAPeze XL Telomerase Detection Kit (MilliporeSigma) following manufacturer instructions. HCT116 cells were used as positive controls while heat inactivated samples served as negative controls. Fluorescence was measured in a SpectraMax plate reader. Percentage of total product generated (TPG) relative to healthy age matched controls was calculated. T-circle detection assays were used on RTEL1 samples based on the protocol by Zhang et al. (2017). Final southern blotting was completed using the TeloTAGGG Telomere Length Assay Kit (Roche), and t-circle bands were visualized in a c600 GEL Imaging System (Azure Biosystems). RESULTS Ten patients (mean age = 53 years (27-71), 50% female) were included in our study. Patients 1 to 5 presented VUS in TERT (n=4) or TERC (n=1) and TL <1 st percentile in lymphocytes and/or granulocytes. Patient 6 carried a known pathogenic variant in RTEL1 and was included as a positive control. Patients 7 to 9 with RTEL1 variants presented TL close to the 10 th or between the 1 st-10 th percentile. No TL results were available for patient 10 but was tested due to the presence of a VUS in RTEL1 (Table 1). Similarly, while patient 7 carried a likely pathogenic variant, it was tested due to presenting lymphocyte TL between the 1 st-10 th percentile. TRAP results indicated decreased telomerase activity compared to age matched controls in all samples with TERT and TERC variants suggesting a pathogenic effect (52.%, 10.7%, 48.7%, 4.4% and 5.2% of TPG compared to age matched controls, respectively) (Table 1). On the other hand, t-circles were only seen in patient 6 (Figure 2). DISCUSSION We used TRAP and t-circle assays to explore the telomerase activity and presence of t-circles in patient samples with TERT/TERC and RTEL1 variants. In the case of TERT/TERC, we observed a reduction of telomerase activity in all samples. Together with blood TL below the 1 st percentile, this suggests that these variants are indeed deleterious (Table 1). However, since patient 4 presented two TERT VUSs, additional testing is needed to conclude how each variant impacts telomerase activity independently. In regard to RTEL1 variants, we observed t-circles in patient 6 as expected. No t-circles could be seen on all remaining samples, including patient 7 who carried a variant classified as likely pathogenic (Figure 1). This in-frame deletion has been described once in a TBD family (Cogan et al. 2015) but was not functionally tested. This result, together with the borderline TL seen in this patient, may suggest that some compensatory mechanism exists on this sample, or that the deleterious effect of the variant is not strong enough to be detected by our assay. Further studies are currently ongoing by our group to validate these results using a cell-based transfection disease model. In summary, we show that functional testing can be a helpful tool to determine pathogenicity of VUSs in TERT/TERC and RTEL1.

Background: Clonal cytopenia of undetermined significance (CCUS) is characterized by the presence of a clone with somatic mutations in genes associated with myeloid neoplasms (MN) or abnormal cytogenetics, along with unexplained and persistent cytopenias in the absence of significant marrow dysplasia. CCUS is considered a premalignant state with a risk of progression to MN. The clinical outcomes of patients (pts) with high risk CCUS (Weeks et al, NEJM Evidence 2023) may be similar that of some patients with myelodysplastic syndromes (MDS). This study aims to predict the outcomes of CCUS patients using the molecular international prognostic scoring system (IPSS-M) developed for MDS. Methods: A retrospective analysis was conducted in patients diagnosed with CCUS between 2015 and 2023, we included patients harboring pathogenic mutations (MUT) identified through next-generation sequencing (NGS) testing at two institutions: Mayo Clinic and the University of Texas Southwestern Medical Center, Dallas, TX, USA were included. Progression was considered present if patients with CCUS progressed into myeloid neoplasm at follow up. Statistical analysis was performed using JMP® 17.1.0 Software. IPSS-M risk scores were calculated via the IPSS-M Risk Calculator (mds-risk-model.com). Results: A total of 103 patients were included in the study. The median age was 72 years, the majority were male patients (73%), and the median bone marrow blast % at the time of NGS was 1%. Forty-five % had an isolated mutation in a single gene, and 55% had co-mutations in ≥1 gene. The median number of mutations was 2 (range 1 - 5), occurring across 43 different genes. The most common mutations were in TET2 (N=28; 27%), ASXL1 (N=21; 20%), SRSF2 (N=21; 20%), U2AF1 (N=18; 17%), DNMT3A (N=16; 16%), and TP53 (N=12; 12%). Additionally, 25% of patients had an abnormal karyotype. Hematologic and genetic characteristics are summarized in (Table 1A). The median IPSS-M score was -0.9 (-3 to +2.34) and the median IPSS- Revised (R) score was 2 (0 - 6). The majority of patients had low (L) IPSS-M risk category (53%), followed by moderate low (ML) (19%) and very low (VL) (17%). Per IPSS-R, the majority had low-risk category (47%), followed by VL (38%) and intermediate (14%). Overall, 26 (25%) pt died after a median follow-up of 34 months and 21% progressed to MN (MDS 14 & CMML 8), and 1 patient with MDS and 1 with CMML progressed to secondary AML (2%). The median overall survival (mOS) was not reached, with a 2-year estimated (YE) OS and leukemia-free survival (LFS) of 80%. Predictive Power: When utilizing the IPSS-M risk category ( L, M, H) * by combining the risk categories into L *(L+VL), M * (ML+MH), and H *(H+VH) to overcome the low sample size limitation, it significantly predicted OS (p < .0001) ( Figure 1A) and median MN-free survival (FS) (p < .0001) ( Figure 1B). The 2YE-OS rates by IPSS-M risk category were as follows: VL - 93%, L - 87%, ML - 75%, high (H) - 25%, very high (VH) - 0% and the 2YE-OS rates by IPSS-M ( L, M, H) are summarized in Table 1B. IPSS-M hazard ratio (HR) for OS was 1.6 for ( M*) compared to 25 for ( H *) risk category (p < .0001). The ( L *) category, being the largest, was used as the reference level. Conclusion: This study provides the first real-world experience of using the IPSS-M and a modified version of the IPSS-M ( L, M, H) * risk category model to predict survival and progression into MN in CCUS (MUT) pt. The IPSS-M risk category was found to be a significant predictor of OS and MN-free survival. We propose that larger cohorts are needed to validate our findings.

Introduction: Clonal dendritic cell (DC) aggregates in chronic myelomonocytic leukemia (CMML) are seen in approximately 20-30% patients at diagnosis. Previously, these were thought to be comprised of CD123+ plasmacytoid DCs but our data has suggested that these are heterogenous and comprise of myeloid DCs, monocytes, and myeloid-derived suppressor cells. Furthermore, these aggregates uniformly express immune checkpoints such as indoleamine 2,3-dioxygenase-1 (IDO), associate with an IDO-specific systemic impact (increased trytophan catabolism), and expanded regulatory T cell population in CMML, suggesting a role in inducing immune tolerance. DC aggregates are also associated with increased risk of acute myeloid leukemia (AML) transformation and resistance to hypomethylating agents, highlighting that they are important for disease progression in CMML (Mangaonkar A et al. Blood Adv 2020). We performed this study to decipher the architecture of a CMML DC aggregate to understand the complex inter-cellular interactions, and assess their impact on the adaptive immune system. Methods: In this study, we used archival fresh-frozen paraffin-embedded (FFPE) bone marrow biopsy specimens obtained from CMML patients, and isolated monocytes (CD14+ magnetic bead sorting) and lymphocytes (CD14-ve fraction) from untreated CMML and age-matched normal control (NC) peripheral blood mononuclear cells (PBMCs). DCs were cultured from monocytes using a commercial protocol. Spatial architecture of the CMML BM microenvironment was interrogated through multiplex imaging of FFPE samples by co-detection by indexing (CODEX) using 30 markers (CCR6, CD107a, CD11c, CD20, CD21, CD31, CD3e, CD4, CD44, CD45, CD45RO CD56, CD68, CD8, E-Cadherin, FoxP3, HLA-DR, CD14, CD16, CD11b, CD33, CD15, CD66b, CD123, CD303, CD34, CD163 and IDO). Single-cell transcriptomic signatures were analyzed using the 10X single cell Fixed RNA profiling platform, and validated using bulk RNA seq (Illumina stranded mRNA prep) from isolated and cultured cells. Impact of DCs on lymphocytes was assessed via autologous mixed DC-T culture experiments. Results: BM FFPE samples from 5 CMML cases (3 with DC aggregates) were included for multiplex imaging via CODEX. Results confirm the significant interactions of CD8+ and CD4+ T cells with CD123+/HLA-DR+ DCs within a CMML DC aggregate (Fig. 1A). Upon quantitative assessment of cell-cell interactions, IDO+/CD8+T ( P=0.006), IDO+/MDSC ( P=0.005), and IDO+/macrophage ( P=0.001) interactions were significantly increased in CMML samples with versus without DC aggregates . Specific findings were validated using single-stain immunohistochemistry and multiplex immunoflourescence staining. Next, in order to assess transcriptomic signatures within BM at the single-cell level, we chose two cases; CMML (BM aspirate blast% 1, WBC 49.6 x 10 9/L, ASXL1/GATA2/SETBP1/SRSF2 mutations) and AML transformed from CMML (BM aspirate blast% 81, WBC 152 x 10 9/L, NPM1/DNMT3A/TET2 mutations). Approximately, 10,000 cells were obtained and analyzed with cell type annotation through human PBMC reference (Azimuth). Results show an expanded regulatory T cell population in AML compared to CMML (UMAP plot, Fig. 1B), suggestive of immune tolerance. In order to validate findings and perform functional experiments, we used sorted monocytes and cutured DCs from CMML and NC. DC phenotype was confirmed both through visual inspection and flow cytometry, and clonality was confirmed through Sanger sequencing (for previously identified mutations). Differential gene expression analysis through bulk RNAseq showed significant differences between CMML and NC lymphocytes with immunoinhibitory receptor, LILRB2 (log2fold change=7.05, adjusted P=0.0002) being one of the top five significantly upregulated genes, further confirming immune tolerance. Finally, mixed autologous DC-lymphocyte reaction (1:4 ratio) experiments demonstrated that DCs induce T cell tolerance in CMML (expansion of exhausted PD1/TIM3/LAG3+ CD8 T cells) when compared to NC. Conclusion: Clonal dendritic cell aggregates within the CMML bone marrow microenviroment interact with T cells and induce immune tolerance. This represents a novel mechanism of disease progression in CMML with potential therapeutic targets (IDO, LILRB2, and/or CD123).

Background: Venetoclax (Ven) in combination with hypomethylating agent (HMA) is the preferred treatment for elderly/unfit patients with newly-diagnosed acute myeloid leukemia (AML). Current prognostication for AML is based on European LeukemiaNet (ELN) genetic risk stratification which has limited applicability in patients treated with Ven-HMA ( Blood, 2022). Accordingly, our primary objective was to determine predictors of treatment response and survival outcomes in treatment-naïve AML patients receiving Ven-HMA. Methods: Our study population was recruited from Mayo Clinic (MN, FL, AZ), after institutional review board approval and based on documentation of newly-diagnosed AML treated with Ven-HMA outside of clinical trials between November 2018 and April 2023. Cytogenetic and molecular studies were performed by conventional karyotype, and next-generation sequencing, respectively. Response was assessed according to the 2022 ELN criteria Results: Patient characteristics A total of 301 newly-diagnosed AML patients (median age 73 years, 66% male, 62% de novo) received a median of 3 cycles (range 1-48) of azacitidine 75 mg/m2 days 1-7 ( n=100) or decitabine 20 mg/m2 days 1-5 ( n=201) with Ven. ELN 2022 cytogenetic risk included favorable (1%, n=4), intermediate (61%, n=184) or adverse (38%, n=113). Mutations involved TP53 in 77/301 (25%), ASXL1 in 54/279 (19%), RUNX1 in 54/296 (18%), NPM1 in 44/299 (15%), DNMT3A in 40/296 (13%), K/NRAS in 41/296 (14%), IDH1 in 20/301 (6%), IDH2 in 30/301 (10%), FLT3-ITD in 25/301 (8%) and DDX41 in 9/247 (4%) of informative cases. Predictors of response Complete remission, with (CR) or without (CRi), count recovery, was documented in 182 (60%) patients, including CR in 36% and measurable residual disease (MRD) negative by flow cytometry in 77% of 105 informative cases that achieved CR/CRi. Median time to CR/CRi was 1.4 months. In univariate analysis, CR/CRi was more likely to occur in the presence of NPM1 mutation, (86% vs. 56%; p < .01), IDH2 mutation, (80% vs. 58%; p = .02), DNMT3A mutation, (78% vs. 57%; p = .01), or DDX41 mutation, (100% vs. 58%; p <.01), and in the absence of adverse karyotype, (71% vs. 42%; p < .01), TP53 mutation, (67% vs. 40%; p <.01), FLT3-ITD mutation, (63% vs. 36%; p = .01), or RUNX1 mutation, (64% vs. 44%; p = .01); in multivariable analysis, adverse karyotype, ( p < .01), FLT3-ITD ( p < .01), RUNX1 ( p < .01), NPM1 ( p = .03), IDH2 ( p = .04), and DDX41, ( p = .01) mutations remained significant. Predictors of survival After a median follow-up of 8.5 months (range 0.5-56), 13.2 months for living patients, 174 (58%) deaths, 73 relapses (40% of those achieving CR/CRi), and 41 (14%; including 35 in CR/CRi) allogeneic hematopoietic stem cell tranplants (AHSCT) were documented. In univariate analysis of pre-treatment variables, thrombocytopenia < 100 x 10 9/l, (HR 1.5, 95% CI 1.03-2.2; p = .03), adverse karyotype, (HR 2.8, 95% CI 2.1-3.8; p < .01) TP53 mutation, (HR 2.5, 95% CI 1.8-3.5; p < .01), or absence of IDH2 mutation, (HR 3.5, 95% CI 1.7-7.6; p < .01) predicted inferior survival. Failure to achieve CR/CRi (HR 4.5, 95% CI 3.3-6.1; p < .01) was also associated with inferior survival and in multivariable analysis, failure to achieve CR/CRi, (HR 3.4, 95% CI 2.5-4.8; p< .01), presence of adverse karyotype, (HR 1.6, 95% CI 1.1-2.6; p = .02), TP53 mutation, (HR 1.6, 95% CI 1.002-2.4; p = .04), and absence of IDH2 mutation (HR 2.2, 95% CI 1.004-4.7; p = .04) were identified as risk factors for survival. Subsequent HR-weighted scoring resulted in three-tiered risk stratification: low (0-1 point; n= 130), intermediate (2-3 points; n= 105), and high (4-5 points; n= 66), with respective median survival (3-year rate) of 28.9 (48%), 9.6 (6%), and 3.1 (0%) months ( p < .01) (Figure). AHSCT had an independent favorable impact on survival (HR 0.3, 95% CI 0.1-0.6; p < .01), most apparent in low ( p =0.04), and intermediate ( p <.01), as opposed to high ( p = .06) risk. Conclusions: In the current single institutional series of Ven-HMA treated newly-diagnosed AML, response to Ven-HMA was the foremost predictor of survival. Additional risk factors for survival included adverse karyotype, presence of TP53 and absence of IDH2 mutations. These observations allowed for a three-tiered genetics-enhanced survival model with CR/CRi as a backbone, and also confirmed survival advantage from AHSCT, regardless of risk category.