FLT3 Mutations Research Articles

Treatment Outcomes of Stem Cell Transplant in Patients with Acute Myeloid Leukemia Treated with Venetoclax in Combination with Hypomethylating Agents: Experience from Routine Clinical Practices in the United States

Background: Venetoclax (Ven) in combination with hypomethylating agents (HMAs) is approved in the United States (US) for treatment in patients (pts) with newly diagnosed (ND) acute myeloid leukemia (AML) who are ≥75 years old or unfit for intensive chemotherapy. In a Phase Ib open-label trial (NCT02203773) and the Phase III VIALE-A trial (NCT02993523), a total of 33 pts with ND AML who were treated with Ven+HMAs underwent a stem cell transplant (SCT). The observed 12-month overall survival (OS) was 74.3% post-SCT, and the median OS was 29.9 months for pts who were in remission at the time of SCT (Pratz et al. EHA 2023). This study aims to evaluate the treatment patterns and outcomes of pts with ND AML treated with Ven+HMAs who underwent SCT post-remission from routine clinical practices in the US. Methods: This was a retrospective cohort study using the Flatiron Health electronic health record-derived, US nationwide, de-identified database. Pts aged ≥18 years with ND AML who initiated first-line Ven+HMAs treatment within 30 days from AML diagnosis (Dx) between July 1, 2018, and November 30, 2022, with ≥2 visits recorded within 3 months of AML Dx, and ≥3 months of potential data available before the study end date (February 28, 2023) were included. Pts with acute promyelocytic leukemia, t(9;22), treated with HMAs before AML Dx and pts who received Ven treatment more than 14 days prior to AML Dx were excluded. Descriptive analysis on patient characteristics was conducted. The proportion of pts who achieved real-world response (defined as <5% bone marrow [BM] blast), median time from Ven+HMAs treatment initiation to last administration (TTLA), and median time from Ven+HMAs initiation to SCT were reported. For pts who received SCT post-remission, 100-day real-world OS (rwOS), 12-month rwOS, and 15-month rwOS were evaluated using Kaplan-Meier analyses. The starting point of Kaplan-Meier analyses was SCT, and pts were censored at the last activity date. Results: Overall, 988 pts with ND AML treated with Ven+HMAs met the study criteria. A total of 51% (n=503/988) of pts achieved real-world response, of which 11% (n=57/503) subsequently underwent SCT post-remission. In pts with SCT post-remission (n=57) vs pts without SCT post-remission (n=446), the median age was 67 years vs 76 years, 30% (n=17/57) vs 30% (n=134/446) had secondary AML, and 60% (n=34/57) vs 24% (n=107/446) were treated at academic centers, respectively. Excluding pts with unknown cytogenetic and molecular data, the European LeukemiaNet (ELN) 2017 risk in pts with vs without SCT post-remission was favorable for 16% (n=7/43) vs 21% (n=76/355), intermediate for 33% (n=14/43) vs 26% (n=93/355), and adverse for 51% (n=22/43) vs 52% (n=186/355), respectively. Among pts with available molecular testing, FLT3 mutation in pts with SCT vs pts without SCT post-remission was 19% (n=5/26) vs 20% (n=48/245); IDH1/2 mutation was 33% (n=9/27) vs 35% (n=95/275); and TP53 mutation was 47% (n=9/19) vs 28% (n=54/192), respectively. Of the 57 pts who underwent SCT post-remission, the median (interquartile range [IQR]) TTLA on Ven+HMAs was 4.0 (3.0-5.3) months and the median (IQR) time from Ven+HMAs initiation to SCT was 5.4 (4.4-6.8) months. At a median follow-up of 8 months from SCT post-remission, the 100-day rwOS was 92%, 12-month rwOS was 52%, 15-month rwOS was 49%, and the median rwOS was 13.0 (95% confidence interval: 8.2-not reached) months ( Figure). Conclusions: In this study, similar to findings from clinical trials, we observed a subset of pts with ND AML treated with Ven+HMAs underwent SCT post-remission in routine clinical setting. Compared with pts who did not undergo SCT post-remission, pts who underwent SCT post-remission were younger, and more of these pts received care in academic centers. Of the Ven+HMAs-treated pts who underwent SCT post-remission, more pts treated in the routine clinical setting had the poor prognostic TP53 mutation than pts enrolled in the aforementioned clinical trials. In this study, most pts remained alive 100 days after SCT. The rwOS results observed in this study suggest that Ven+HMAs post-remission is a potential bridge to SCT in pts who are ineligible for intensive chemotherapy.

Assessment of SIRT1-SIRT7 and TP53 Genes Expression in Patients with Acute Myeloid Leukemia

BACKGROUND Sirtuins ( SIRTs) are a family of histone deacetylases with 7 representatives ( SIRT1-7), which affect cell survival and metabolism. They influence gene expression by interacting with histones and transcription factors, or directly modulate pathways associated with cell survival, for instance by downregulating p53, thus potentially contributing to cancerogenesis. On the other hand, SIRTs may function as tumor suppressors depending on cellular context. While the role of SIRTs expression is widely discussed in solid neoplasms, they have not been comprehensively evaluated in acute myeloid leukemia (AML) yet. AIMS To investigate the prognostic importance of initial SIRTs expression in AML patients (pts) and its relationship with the expression of TP53. METHODS The study included 40 newly diagnosed AML pts (19 women, 21 men), with a mean age of 62 years (range: 26-87). Low-, intermediate- or high-risk AML according to European LeukemiaNet (ELN) 2022 stratification was diagnosed in 6 (15%), 13 (32.5%), and 21 (52.5%) of pts respectively. The expression of SIRT1-7 and TP53 was examined by real-time PCR using the TaqMan chemistry and the QuantStudio7 thermal cycler (Applied Biosystems-Thermo Fisher Scientific). The reference genes were selected using GeNorm and NormFinder. The mRNA levels were normalized by the formula ∆Ct = Ct(reference) - Ct(particular mRNA). Group comparisons were performed using Welch's t-test. Pearson correlation evaluated the relationship between individual gene expression. Overall survival (OS) was assessed by the Kaplan-Meier method with the log-rank test. Cox proportional hazard regression of clinical factors and genes expression for predicting OS was performed. RESULTS FLT3 ITDor TKD mutations were present in 10 (25%) of pts, NPM1 in 9 (23%), and IDH1 or IDH2 in 6 (15%). 14 (35%) of the study group were diagnosed with AML with myelodysplasia-related cytogenetic abnormalities, AML progressed from myelodysplastic syndrome, or therapy-related AML (secondary AML, sAML). Standard induction chemotherapy was given in 42.5% of pts, 25% were treated with azacitidine+venetoclax (Aza+Ven), and other non-intensive therapies were administered to 32.5%. SIRT4 expression was detected in 92.5% of pts, while expression of the other genes studied was found in all pts. There were no differences in SIRT 1-7 expression in terms of ELN2022 risk stratification. However, TP53 was downregulated in the high-risk group (fold change - FC=0.6, p=0.004). In pts with FLT3 mutation, SIRT7 was downregulated (FC=0.8, p=0.07), while in both NPM1 and IDH1/2 mutated groups, we showed upregulation of TP53 (FC=1.5, p=0.03, and FC=1.5, p=0.001, respectively). Moreover, in older pts (>60 years old) TP53 was downregulated (FC=0.7, p=0.02). In sAML group SIRT3 and TP53 were downregulated (FC=0.7, p=0.08, and FC=0.7, p=0.05, respectively). Significant positive correlations were shown between the expression of individual SIRTs, and it was most strongly expressed between SIRT2 and SIRT6 (r=0.85, p=0.00), SIRT2 and SIRT7 (r=0.81, p=0.00), and SIRT6 and SIRT7 (r=0.76, p=0.00). The median follow-up was 6.7 months (95% CI: 4.5-9.1). The median OS in the study cohort was not reached. There were no significant differences in treatment response or OS considering each SIRT expression level. However, pts with higher TP53 expression (> median) presented longer OS (median OS not reached vs 5.8 months (95% CI:1.3-5.8, p=0.05) [Figure 1]. In the multivariate Cox proportional hazard model for OS, upregulation of TP53 (HR 0.25, 95%CI: 0.08-0.60, p=0.01), age (HR 1.06, 95%CI: 1.01-1.12, p=0.03), as well as initial albumins (HR 0.01, 95%CI: 0.00-0.07, p=0.01), and LDH levels (HR 1.00, 95%CI: 1.00-1.01, p=0.01) were factors influencing the outcome [Table 1]. CONCLUSIONS The expression of SIRTs in AML presented no evident impact on treatment outcome. However, our study revealed that higher TP53 expression was associated with longer OS. Moreover, TP53 upregulation was found in pts with certain mutational profiles, while downregulation in the elderly and those with sAML. The analysis indicates that SIRTs expression may also vary markedly depending on the clinical and molecular context. The expression of individual SIRTs is closely correlated with each other, but these preliminary results did not show their direct relationship with TP53 expression. Further studies on SIRTs are needed to assess their impact on AML.

Evaluation of Neddylation and Apoptosis-Related Gene Expression in Patients with Acute Myeloid Leukemia

Introduction Regulated cell death (RCD) is a process commonly dysregulated in patients (pts) with acute myeloid leukemia (AML), resulting in the survival of genetically unstable cells. Apoptosis, as the best-known form of RCD, interacts with neddylation, a process that contributes to tumorigenesis and apoptosis resistance. Aims This study was conducted to determine the expression of the selected genes involved in the neddylation pathway and to assess their clinical importance along with selected interacting proapoptotic genes. In addition, we correlated the expression levels of these genes with known prognostic factors in AML and determined their impact on the survival of AML pts. Methods The expression of selected proapoptotic genes BIK, BAX, BAK, BCL2L11, BBC3 , PMAIP1 CASP3, CASP7, and neddylation-related genes: CUL1, CUL2 , CUL4A, CUL5, CUL7, CUL9, NEDD8 was determined in duplicates in bone marrow samples of newly diagnosed AML pts. Real-Time PCR was carried out using the TaqMan chemistry and the QuantStudio7 thermal cycler (Applied Biosystems-Thermo Fisher Scientific). Gene expression was normalized using reference genes selected by the Normirazor tool. The normalization was performed by ∆Ct = Ct (reference) - Ct (mRNA of interest). This approach results in higher values for higher mRNA expression. Differential expression analysis was performed using a Welch t-test. Kaplan-Meier method with the log-rank test was used to assess overall survival (OS). Results In a prospective study, we included 40 newly diagnosed AML pts (mean age 62; range 26-87) with a median (m) follow-up of 6.7 months (95% CI: 4.5-9.1). High-risk AML was present in 52.5%, intermediate-risk in 32.5%, and low-risk in 15% of pts, according to European LeukemiaNet (ELN) 2022 risk stratification. NPM1 mutation was present in 23%, whereas FLT3 ITD or TKD mutation in 25% of pts. Intensive treatment was introduced in 43% of pts, while 25% were treated with azacitidine+venetoclax. Non-intensive treatment with azacitidine in monotherapy was administered to the remaining pts. BAK expression was detected in 70%, BIK in 98%, while expression of the other genes was found in all pts. In the high-risk group, we detected lower expression of both proapoptotic BAX (fold change - FC=0.7, p=0.01) and BIK gene (FC=0.4, p=0.01), as well as lower expression of CUL9 (FC=0.7, p=0.03). Accordingly, in pts with NPM1 mutation we revealed upregulation of BIK (FC=6.1, p=0.001), and CUL9 (FC=1.6, p=0.01). Whereas pts with FLT3 mutation had lower expression of proapoptotic BBC3 (FC=0.5, p=0.01), and neddylation-related CUL1 (FC=0.6, p=0.01). In cases of initial bone marrow blasts infiltration above median value (>49%) BCL2L11 CUL5 , NEDD8 and PMAIP1were downregulated ( p=0.001-0.02), while CUL7 ( p=0.00) and CASP3 ( p=0.04) were upregulated. Patients with initial white blood cell count >20 G/l had lower expression of BCL2L11 ( p=0.005), and CUL4A ( p=0.02), while higher expression of CASP7 ( p=0.04). The mOS in the study cohort was not reached. OS was longer in pts with higher (> -2.061, cutoff was determined with CutOff Finder) BAX expression (log-rank: p=0.03) [Figure 1]. The mOS was not reached in this group, whereas the mOS in pts with lower BAX expression was 1.3 months (95% CI: 0.6-1.3). In univariate Cox regression analysis, higher BAX expression (HR 0.31, 95%CI: 0.11-0.84, p=0.022), higher albumin level (HR 0.13, 95%CI: 0.04-0.41, p=0.0004), and intensive treatment (HR 0.18, 95%CI: 0.04-0.69, p=0.012) were factors influencing the outcome. In the multivariate model for OS, higher expression of BAX (HR 0.03, 95%CI: 0.003-0.33, p=0.004) retained its significant protective effect in the context of established prognostic factors [Table 1]. Conclusions To our knowledge, we were the first to evaluate such a complex spectrum of neddylation and apoptosis-related genes in AML. We revealed dysregulation of these genes in AML. Our data indicate that upregulation of BAX at the diagnosis is associated with longer OS. Moreover, we reported significantly lower BAX expression in ELN high-risk group. Thus, indicating BAX may be a potential prognostic factor in AML. Our preliminary results did not prove significant differences in the effect of neddylation gene expression levels on the prognosis of AML patients. As studies are emerging on the potential of neddylation-targeted therapies, we are conducting further research to verify the effect of neddylation on AML.

CLAG-Based Chemotherapy in Previously Untreated AML Patients: 12 Year Follow-up

Introduction: The 7+3 combination of cytarabine plus an anthracycline is the most commonly used induction regimen for AML in the US. There is evidence FLAG-IDA may be superior to 7+3 (Solh et al Leuk Res 2020), and that cladribine is superior to fludarabine (Holowiecki et al JCO 2012). Currently we report the results of CLAG-based chemotherapy in newly-diagnosed AML patients. Methods: This single-center retrospective cohort studied all patients with newly-diagnosed AML who received CLAG-based induction therapy (with or without an anthracycline, depending on cardiac function) between February 2011 and June 2023. Chemotherapy consisted of cladribine 5 mg/m 2 daily times 5 days, cytarabine 2 gm/m 2 over 4 hrs daily times 5 days (given 2 hours after the completion of each cladribine dose), plus G-CSF 300 ug daily during chemotherapy and then based on weight after that. Patients with adequate cardiac function also received 3 days of mitoxantrone 12 mg/m 2 (CLAG-M) or idarubicin 12 mg/m 2 (CLAG-IDA) on days 1-3 or 2-4. Many of these patients were treated prior to the current era of targeted therapies and thus most received chemotherapy without targeted agents. Post-remission therapy was given at the physician's discretion based on the patient's tolerance of induction chemotherapy. Complete response (CR) was defined as less than 5% blasts in the marrow with recovery of ANC >1000/mm 3 and platelets >100,000/mm 3. Lesser responses included CRi, CRp and PR. All others were considered failures or early deaths (within 30 days). This study was approved by the IRB of New York Medical College. Results: We analyzed all 87 newly-diagnosed AML patients that were treated with CLAG-based induction therapy (CLAG alone: 10%, CLAG-IDA: 87%, CLAG-M: 3%). 4 patients with a FLT-3 mutation received a FLT-3 inhibitor concurrently. Post-remission therapy included allo transplant (13%), further CLAG+/- IDA, reduced to 4+2 days (84%), HiDAC (27%), and hypomethylators (36%), in that order of priority. The intensity of the post-remission therapy was matched with the perceived ability of the patient to tolerate it. Many patients received more than one post-remission therapy in sequence. The median age of the cohort was 65 (33-85) years. 59% were male, 47% were smokers, 6% had prior MDS and 13% had therapy-related AML. The median baseline WBC was 9.7 (0.4-392) k/mm 3. 10% of patients were stratified as favorable ELN cytogenetic risk, 45% as intermediate, and 45% as adverse. TP53 mutation was present in 22% patients and FLT3 mutation in 14% patients. CR was obtained in 67% of patients overall and did not differ significantly by age (<60: 65%, 60-70: 70%, >70: 64%). Early deaths (within 30 days) were more common in older patients (<60: 3%, 60-70: 3%, >70: 8%). The CR rate was similar across all cytogenetic risk groups (good risk: 67%, intermediate risk: 68%, poor risk: 62%) and was favorable in patients with a TP53 mutation (68%), as well as those with therapy-related AML (69%). The median overall survival (OS) was 13 months. By cytogenetic risk the median OS was good: not reached, intermediate: 25.6 months and poor: 6.8 months (Figure 1). It should be noted that two patients with good risk cytogenetics who expired included an 80-year-old woman with therapy-related AML after treatment for breast cancer who declined further therapy after cycle 1 and survived 20 months with no further therapy, as well as a second unvaccinated patient who expired due to complications of COVID. Median OS by age was <60: 18 months, 60-70: 25.6 months and >70: 8 months (Figure 2). Median overall survival for patients with TP53 mutation was 5.6 months. Conclusion: CLAG provides an alternative induction regimen to 7+3. Interestingly, in contrast to 7+3, CR rates did not differ significantly by age or cytogenetic risk group. The older patients treated on this trial were a select group that were considered eligible for intensive chemotherapy. Many of the patients on this trial would be treated differently today, with the availability of more targeted therapies. However the relatively high response rates in patient with poor risk cytogenetics and/or TP53 mutation gives fit patients the opportunity of pursuing stem cell transplantation.

Optimizing FLT3 Inhibitor Use in Adult Acute Myeloid Leukemia with FLT3 Mutations Using Proteomics

CONCLUSION FLT3 mutations are the most frequent genetic alteration in adult Acute Myeloid Leukemia (AML). The use of FLT3 inhibitors (FLT3I) has improved outcome among FLT3 mutant patients, but not all benefit. We developed a proteomic-based approach to stratify patients according to their response to FLT3I therapy. The expression of 429 proteins (339 total, 90 post-translational modified) was measured by Reverse Phase Protein Arrays (RPPA) in fresh samples from 805 newly diagnosed AML patients, with levels normalized to normal CD34+ cells. Of 137 with FLT3 ITD or D835 mutations, 54 who were treated with FLT3I (Sorafenib=22, Quizartinib=11, Midostaurine=6, Gilteritinib=4 and Crenolanib=1) combined with other agents (Hypomethylating agents (HMA)=23, HMA+Venetoclax (VTX)=5, Idarrubicin+Cytarabine (AraC)+Purine Analogs (IA+Pur)=19, IA+Pur+VTX=2, AraC=3, Fludarabine+AraC (FA)=1, none=1) were selected for analyses. Proteins prognostic for Overall Survival (OS) and Complete Remission Duration (CRD) were identified using pairwise LogRank tests (p < 0.05) adjusted for False Discovery Rate, followed by unbiased hierarchical clustering. Continuous and categorial variables were compared with Wilcoxon, Kruskal-Wallis or Fisher's Exact test with simulated p-values (10000 replicates). Cox proportional hazards models (CoxPH) were developed for Uni-(UV) and Multi-variate (MV) analysis. Deep neural network analysis using random forest models identified proteins most predictive of cluster assignment. 28 proteins were individually prognostic for both OS and CRD and divided patients into 3 clusters (Fig. 1: C1=red, C2=blue, C3=green). The distribution of nearly all other clinical and molecular features did not differ between clusters, including: age, gender, race, cytogenetic risk and AML group. Co-occurrence with other mutations was not biased, except for FLT3+TET2 and FLT3+TET2+NPM1 mutants, more frequent in C1. OS was significantly longer (Fig. 2), in C1 (Median: C1>84mo, C2=14.8mo, C3=11.4mo; p<0.001) as was CRD (Median: C1>84mo, C2=8.6mo, C3=5.7mo; p<0.05). A similar OS pattern was observed for mutation combos, including with NPM1 or DNMT3a but not if IDH, CEBPa, TET2, or ASXL1 mutation were present. It was also seen when patients were divided by gender, age groups (except >70yo), primary, but not secondary AML, diploid karyotype and intermediary cytogenetic risk, and with Sorafenib or IA+PR therapies. In the UV CoxPH model for OS, C1, C2 and C3 were predictive (HR=1, 4.1, 7.5; p=ref., 0.037, 0.009), along with age, secondary AML, complex karyotype, Trisomy 6 and IDH1 mutation. In the MV model for OS, only C1, C2 and C3 (HR=1, 3.3, 4.8; p=ref., 0.011, <0.001), and age were predictive. In the CRD UV model, C1 and C3 (HR=1, 3.3, 4.8; p=ref., 0.072, 0.022), age, secondary AML, and mutations in ASLX1, PTPN11, RAS, TP53 and WT1 were predictive. Only C1 and C3 were predictive in the MV model for CRD (HR=1, 2.9, 6.3; p=ref., 0.16, 0.04). The predictive proteins, are biased towards specific cellular processes, mainly: proliferation and metabolism (RHEB, GSKA_B, SDHA, AKT1, AKT2 and TYRO3), cell cycle and DNA damage response (CDKN2A, DDB1, SIRT6, SLFN11 and WEE1), cellular adhesion and cytoskeleton organization (MYH9.pS1943, PAK4 and PXN), and apoptosis (AIFM1, BBC3 and BCL2L11). Key differences between clusters included: higher FOS in C1, and higher CDKN2A, MYH9.pS1943, PXN, PAK4, SDHA, BBC3 in both C2 and C3, with higher levels of these in C3. Since PAK4, PXN and MYH9 are connected to cellular motility/migration and inhibitors for those proteins are available, there is a therapeutic opportunity to overcome FLT3I resistance in C2/C3 patients. Moreover, we identified a set of 6 proteins (FOS, AKT1, PXN, SMARCA2, CDKN2A and DPF2) that predicted cluster assignment with 97.5% accuracy, making rapid patient stratification possible in the clinical setting. Protein profiling identified cohorts of FLT3 mutant patients that achieved the highest benefit from FLT3I addition, regardless of all other clinical or molecular characteristics. We identified targetable proteins that are elevated in adverse signatures, and hypothesized that these may be targets for modulation to improve FLT3I response. Moreover, a small set of 6 proteins accurately classifies patients and could be used clinically to triage patients for treatment recommendation.

Notable Efficacy of Co-Treatment with FHD-286, a Dual BRG1/BRM ATP-Ase Inhibitor, and Menin or BET Inhibitor, Decitabine or Venetoclax Against AML with MLL-r or Mutant NPM1

BRG1 (SMARCA4) and BRM (SMARCA2) are the core ATPase within the multi-protein, ATP-dependent, chromatin remodeling BAF complexes that regulate gene transcription. FHD-286 is a potent, selective, orally administered, inhibitor of BRG1/BRM in early clinical development as a therapy for AML. In present studies, we determined that exposure to FHD-286 (10 to 100 nM) for 4 to 7 days induced CD11b and morphologic features of differentiation and loss of viability in AML cell lines (MOLM13, MV4-11 and OCI-AML3) and patient-derived (PD) AML cells with MLL1r or mtNPM1. Notably, FHD-286 also induced significant lethality in Menin inhibitor (MI) resistant AML cell lines and PD AML cells lacking Menin mutations. ChIP-Seq analysis showed that exposure to FHD-286 significantly reduced the occupancy of BRG1 and H3K27Ac on the chromatin and reduced the core transcriptional regulatory circuitry in MOLM13 cells. FHD-286 treatment concordantly reduced genome-wide ATAC-Seq and RNA-Seq peaks, with negative enrichment at the gene-sets of MYC and E2F targets, mTORC1 signaling, translation initiation/elongation and DNA replication. scRNA-Seq analysis in PD AML bone marrow cells with MLL1r or mtNPM1 showed significant decline in the myeloid/erythroid progenitor (MEP) cells. Mass spectrometry conducted on FHD-286-treated vs control cells revealed a significant decline in the protein levels of c-Myc and its targets, as well as of PLK1, BCL2, PU.1 and CDK4, but exhibited increased levels of HEXIM1, CDKN1A/1B, CEBPα and CD11b. Moreover, CyTOF analysis of PD AML cells with MLL1r or mtNPM1 showed significant decline in the protein levels of c-Myc, PU.1, BRG1, MEF2C, PBX3, BCL2 and MCL1, but exhibited increased levels of cleaved PARP and Caspase-3 in the AML stem/progenitor cells defined by high expression of CLEC12A, CD123, CD99 and CD33 but low expression of CD11b. A domain-specific CRISPR screen targeting epigenetic regulators revealed significant co-enrichments with FHD-286 treatment of the gRNAs against BRD4 and LSD1, suggesting them as the epigenetic mechanisms of FHD-286 resistance. Consistent with findings noted above, co-treatment with FHD-286 and venetoclax, BET inhibitor (OTX015), decitabine or MI (SNDX-50469) exerted synergistic lethality in AML cell lines (MOLM13, MV4-11 and OCI-AML3) and PD AML cells with MLL1r or mtNPM1 (delta synergy scores between 10 to 33 by the ZIP method). In a PD xenograft (PDX) model of MLL1r AML with FLT3 mutation, monotherapy with FHD-286 (oral gavage) for 4 to 6-weeks was significantly effective in reducing AML burden and improving overall survival. Separately, in vivo FHD-286 treatment vs vehicle control, also significantly inhibited the AML-initiating potential, by reducing the AML burden and improving survival of the re-engrafted mice with the FHD-286-treated PDX cells. Moreover, co-treatment with FHD-286 and venetoclax or decitabine or OTX015, vs each drug alone, or vehicle control, significantly reduced the AML burden and improved survival, without significant toxicity in the PDX model. Finally, co-treatment with FHD-286 and OTX015 or SNDX-5613 (oral gavage) was significantly more effective than each drug alone in reducing the AML burden and overall survival of mice engrafted with a separate PDX model of AML cells with mtNPM1 and FLT3-ITD, without significant toxicity. These findings demonstrate the pre-clinical efficacy of FHD-286-based rational combinations and underscore their promise against AML with MLL1r or mtNPM1.

Identification of Unexpected Responders to Gilteritinib in a Cohort of FLT3-WT AML Patients Using Ex-Vivo Testing

Introduction: Despite the numerous significant advances in leveraging actionable genetic biomarkers, targeted therapies continue to exhibit limited success in AML. This may be attributed to the genetic heterogeneity and plasticity of cancer cells, which ultimately overrides the driving force of individual mutations and their resulting phenotypes. In the face of this well-known challenge, there is a growing promise of functional assays that can leverage the integrated phenotypic response of cancer patients' cells to determine treatment schemes in a personalized manner. In addition, functional testing holds the potential to identify elusive responders to targeted therapies in cohorts of patients who do not present the actionable mutations that are used as biomarkers for prescription. Aim: To perform pre-clinical correlation studies between FLT3 mutational status and the ex-vivo response to Gilteritinib using a functional assay of Patient Micro Avatars (PMAs) developed at OncoPrecision. Materials and Methods: Ex-vivo testing with PMAs was performed to evaluate the ex-vivo response to Gilteritinib in 67 bone marrow or peripheral blood samples from patients diagnosed with different AML subtypes (de novo, relapsed/refractory and secondary). Pathological subpopulations were analyzed using lineage markers and survival of blasts was assessed using flow cytometry. Samples were classified as “responders” and “non-responders” using in-house supervised and non-supervised machine learning tools. In parallel, samples were analyzed by NGS and molecular biology to identify mutations and internal tandem duplications in the FLT3 gene. Finally, FLT3 alterations were correlated with the phenotypic response obtained in the functional assay using statistical analysis to compare mutant and non-mutant frequencies in the two groups. Results: The results of the phenotypic screening revealed that ~70% of patients with FLT3 mutations exhibited a strong response to Gilteritinib, which is in line with the presence of the actionable genetic biomarker (Figure). The fact that the remaining ~30% of mutated patients presented a poor response to Gilteritinib suggests the existence of acquired mechanisms of resistance that are dominant over the mutational status of FLT3. Interestingly, we also identified a large group of FLT3wt patients (~30%) which showed a phenotypic response to Gilteritinib equivalent to the one observed in FLT3mut patients (Figure). This finding unveils the existence of a subpopulation of FLT3wt patients who may benefit from Gilteritinib treatment and cannot be identified using conventional genetic testing. Conclusions: The present study highlights the reach of functional testing as a powerful tool to predict Gilteritinib resistance in FLT3mut backgrounds and to identify exceptional responders in FLT3wt backgrounds, creating opportunities for AML patients beyond the currently available genetic biomarkers.

The Efficacy and Safety of CLAG±Ida/Mito+Ven As Salvage Therapy of Relapsed/Refractory Acute Myeloid Leukemia

Purpose: As known CLAG±Ida/Mito regimen is recommended by different guidelines as a chioce for salvage therapy of relapsed/refractory acute myeloid leukemia (RR-AML). Recent study showed venetoclax (Ven) added to CLAG+Ida as frontline treatment of AML acquired a good response and well toleration. Yet, how CLAG±Ida/Mito+Ven works in the salvage therapy of RR-AML remains unclear. Aim of this study was to analyze the efficacy and safety of CLAG±Ida/Mito+Ven as salvage therapy of RR-AML. Methods: A single center, retrospective study was performed. Patients with RR-AML, who were salvagedly treated with CLAG±Ida/Mito+Ven during July 2021 to June 2023, were included. CLAG±Ida/Mito+Ven: cladribine 5mg/m 2 day 1-5, cytarabine 1-1.5g/m 2 day 1-5, PEG-G-CSF 6mg day 0, idarubicin 6mg/m 2 day 1-3 or mitoxantrone 6mg/m 2 day 1-3 (lipo-Mito 20mg/m 2 day 1), Ven 400mg day 2-8. Results: 33 patients were included, with a median age of 42(15-72) years old, male to female 17/16, de novo/sAML 31/2, refractory/relapsed 17/16, ELN-low /intermediate/high risk 7/10/16. They previously received median 2(1-12) cycles of chemotherapy, including 2 relapsed after allogeneic hematopoietic stem cell transplantation (allo-HSCT), 14 with prior hypomethylating agents (HMA). Among the 33 patients with CLAG+Ven, 3 were combined with Mito, 1 with Ida, 15 with FLT3 inhibitors. After one cycle of salvage therapy, 24(72.7%) acquired response, including 22(66.7%) with CR/CRi, 15(45.5%) with MRD-negative (accounting for 68.2% of the patients with CR/CRi). Multivariate analysis showed that prior HMA, FLT3 mutation and ELN-high risk were the independently poor factors for CR/CRi. With a median follow-up of 3(1-23) months, 15(45.5%) patients were bridged to allo-HSCT, 3(12.5%) relapsed, 5(15.2%) died, including 3 died of leukemia progression and 2 with transplant-related motality. Patients obtaining CR/CRi had significantly longer overall survival (mOS, 19.8(15.8-23.8) months) than those without (mOS, 5.1(2.7-7.5) months, P=0.013). Patients being bridged to allo-HSCT also had significantly better OS than those without. During the salvage therapy, the median duration of agranulocytosis was 19(11-40) days. 25(75.6%) patients underwent manageable infection. The motality of the 30 and 60 day were 0. Conclusion: CLAG±Ida/Mito+Ven might be a chioce for salvage therapy of RR-AML, with the CR/CRi rate of 66.7%, MRD-negative rate of 68.2% and well toleration. Key words: CLAG, venetoclax, salvage therapy, relapsed/refractory, acute myeloid leukemia

A Phase 1b/2 Trial of Liposomal Cytarabine and Daunorubicin (CPX-351) in Intermediate to High-Risk Acute Myeloid Leukemia for Patients Who Have Failed an Initial Cycle of Induction Chemotherapy

Introduction Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy with a high rate of recurrence following standard chemotherapy that continues to have a poor prognosis. While there have been numerous recent advances in the treatment of AML, seven days of continuous infusion cytarabine combined with three doses of an anthracycline medication (7+3) remains the most common backbone treatment for younger (<60) patients. Following 7+3 treatment, patients are typically assessed by a bone marrow biopsy 14-21 days after initial treatment, and 20%-30% of patients will have persistent disease at this time. This residual disease is typically treated with an additional round of the same induction treatment at a full or slightly reduced dose. Unfortunately, a complete response (CR) following re-induction is infrequent in intermediate and high-risk AML patients (CR rates of 35% and 18%, respectively). We have performed mass cytometry studies of AML cell cycle state and find that in patients with residual disease at day 14-21 of induction, leukemia stem and progenitor cells have a low proliferative fraction. We hypothesize that this low rate of proliferation reduces the effectiveness of re-induction therapy and could be countered using CPX-351, which is FDA-approved for treatment of therapy-related AML and AML with myelodysplasia-related changes. CPX-351 is a formulation of cytarabine and daunorubicin in a liposomal structure at an optimal 5:1 molar ratio that has been shown to be preferentially absorbed by hematopoietic cells and to persist in serum and bone marrow for significantly longer than traditional 7+3 chemotherapy. We hypothesize that the unique properties of CPX-351 will better target quiescent leukemia stem and progenitor cells and we thus designed a phase 1b/2 study to determine the safety and efficacy of CPX-351 as re-induction treatment for patients with intermediate and high-risk AML with residual disease after a first round of induction. Patients and Methods Eight patients with intermediate or high-risk AML who had failed to achieve hypocellular marrow 14-21 days following initial treatment with traditional 7+3 cytarabine and daunorubicin were treated with CPX-351 re-induction in the phase 1b portion of the study with a CPX-351 dose of daunorubicin 44 mg/m 2 and cytarabine 100 mg/m 2 given two or three times every 48 hours. Concomitant midostaurin (days 8-21) was allowed for patients with FLT3 mutations (Patients #1 and #8). Four patients were ELN intermediate-risk and four adverse-risk; mean blast count before re-induction was 45%. Patients were assessed weekly for signs of toxicity and for treatment response. Samples were collected from bone marrow biopsies performed before and after treatment for correlative mass cytometry studies using a 50-antibody panel to determine cell cycle state, intracellular signaling markers, and DNA damage response. Results Of the eight patients treated to date, six received two doses of CPX-351 and two received three doses. Of the six patients receiving two doses, five achieved a morphologic CR (two with residual genetic alterations), and one patient achieved a CRi. Two patients received three doses of CPX-351, with one achieving a PR and the other MLFS. Five of the eight patients were able to proceed to an allogeneic stem cell transplant. Consistent with previous studies of CPX-351, treatment was well-tolerated, almost all grade 3 or 4 toxicities were due to cytopenias (including two DLTs for delayed count recovery) and the only significant drug-related non-hematologic toxicity was a decrease in cardiac ejection fraction in patient #1. All treated patients survived >150 days and all were able to receive additional AML-directed therapy or HSCT after CPX-351 treatment. Due to slow accrual, hematologic toxicity, and the 100% CR/CRi rate in the two-dose group, the trial was amended to use two doses for the phase 2 portion, and an additional study site was opened. Study accrual is ongoing with a target of 20 additional patients in the phase 2 portion. Conclusion This ongoing phase 1b/2 trial of CPX-351 (liposomal cytarabine and daunorubicin) as re-induction treatment for intermediate and high-risk AML has been safe and tolerable with early treatment outcomes that appear to be much better than reported historical controls. Correlative studies by mass cytometry will further establish the mechanistic reasons for the observed responses.

Clonal Heterogeneity and Evolution during Treatment in High Hyperdiploid B-Cell Acute Lymphoblastic Leukemia

Introduction: Acute lymphoblastic leukemia (ALL), the most common pediatric malignancy, is caused by the accumulation of multiple genomic aberrations in developing lymphocytes. In children, high hyperdiploidy (HeH) is the most prevalent subtype of B-cell ALL (B-ALL), which is associated with a superior outcome. However, because of the high incidence of HeH B-ALL in children, this subtype is responsible for about 25% of all relapses. The prediction of relapse remains difficult, especially in these good risk subtypes. Recent studies indicate that ALL is a heterogeneous disease, with multiple leukemia clones at diagnosis, each having a distinct set of mutations. We hypothesize that these different subclones have a different sensitivity to treatment and that samples with more heterogeneity are more prone to relapse. We used single-cell sequencing to determine the clonal heterogeneity of HeH B-ALL at diagnosis and followed the clonal evolution during chemotherapy treatment. Methods: Bone marrow samples of 11 patients with HeH B-ALL were collected at diagnosis, during treatment (for 9 cases) and at relapse (for 1 case) (Table 1). Samples during treatment were enriched for leukemia cells using magnetic antibodies targeting cell membrane markers (CD10, CD19, CD34) with the MARS® gentle sorter. We performed targeted single-cell DNA sequencing with the Mission Bio Tapestri® Platform, using our custom amplicon panel of 414 amplicons across 39 commonly mutated genes. This method detected single nucleotide variants (SNVs) and small insertions/deletions (indels) based on targeted PCR amplification in about 4000 cells per sample. Results: We sequenced diagnostic samples from 11 HeH B-ALL patients. For 9 patients we also tested samples during treatment, either at day 15 of treatment (1 case) or at the end of induction (EOI) (8 cases), and for 3 cases an additional sample at the end of consolidation (EOC). Furthermore, for one patient, we analyzed samples of 3 subsequent relapses. In total, 117,148 single cells were processed, with an average of 4500 cells per sample. We detected multiple subclones in almost all diagnostic samples (9/11), ranging from 2 to 10 subclones per case. Most frequently mutated genes were KRAS, NRAS, PTPN11 and FLT3, as well as NSD2. Four cases had 2 or more different KRAS and/or NRAS subclones. Three cases had a subclone with a KRAS/ NRAS mutation co-occurring with a NSD2 mutation. For the patients with multiple subclones at diagnosis, we subsequently performed single-cell analysis on one or more follow-up samples, either during treatment or at relapse. In the samples taken at EOI, we detected residual leukemia cells in all 8 cases: multiple subclones were detected in 5 cases and only one subclone persisted in 3 cases. Residual leukemia cells were also detected in all samples collected at EOC, though in a lesser amount as compared to the previous timepoint sequenced. Interestingly, in the matched diagnosis-relapse case, we found that a minor subclone with a NSD2, PTPN11and KRAS mutation became the dominant clone at first relapse (Figure 1). Conclusions: Single-cell DNA sequencing reveals a strong genetic heterogeneity in HeH B-ALL based on a variety of mutations in KRAS, NRAS, PTPN11, FLT3 and NSD2. RAS mutations and FLT3 mutations are mutually exclusive in subclones, whereas NSD2 mutations and RAS mutations are frequently co-occurring in the same subclone. This cooperation is highlighted in our relapse patient, having a minor subclone with a KRAS and NSD2 mutation at diagnosis that became the largest subclone at relapse. Even though few leukemia cells persisted during treatment, we were able to genetically identify the residual subclones with a potentially higher therapy resistance.

Impact of PTPN11 Mutations in De Novo, Secondary and Relapsed/Refractory Acute Myeloid Leukemia

Background Somatic mutations in the protein phosphatase non-receptor type 11 ( PTPN11) gene occur frequently in children with juvenile myelomonocytic leukemia and less commonly in adults with AML, being present in less than 5% of reported cases. Uncertainty exists regarding the prognostic impact of PTPN11 mutations in AML, largely owing to their observed rarity. Some retrospective studies have identified PTPN11 mutations as deleterious prognostic markers in AML, though others have noted that their negative impact is mitigated by concurrent NPM1 mutations, which frequently co-occur. We analyzed the outcomes of patients at our institution with AML and PTPN11 mutations in order to add to the literature regarding the relevance of this mutation. Methods We conducted a retrospective case series of patients at a single-center, tertiary-care institution who were diagnosed with AML between January 1 st, 2020 and June 1 st, 2023. Inclusion criteria included: 18 years of age or older, primary follow-up at the study institution, documented diagnosis of AML and identification of a PTPN11 mutation by NGS. Outcomes of interest included cytogenetic and molecular profiles, response to induction or salvage therapy, progression-free survival (PFS) and overall survival (OS). Results Twenty-two (12 men and 10 women) patients with PTPN11 mutant AML were identified. The median age at diagnosis was 60 years (range, 31-89 years). Nineteen patients had a PTPN11 mutation identified at diagnosis and 3 had a PTPN11 mutation appear at the time of relapse. Nine patients with de novo AML had PTPN11 mutations identified at diagnosis. Six were female and the average age at diagnosis was 60 years (range, 44-89 years). The most common co-occurring mutations were NPM1 (8 patients), DNMT3A (3 patients), TET2 (2 patients) and FLT3-TKD (2 patients). Cytogenetics were normal or non-adverse in 8 patients, and complex/adverse-risk in 1 patient. Seven patients received treatment - 4 with intensive chemotherapy and 3 with a hypomethylating agent (HMA) + venetoclax. Treatment response was CR/CRi in 6 patients (85.7%). At a median follow-up of 195 days, median PFS and OS were not reached. Two patients relapsed at 76 and 139 days after response. No patients received an allogeneic transplant in first remission. Ten patients with therapy-related or secondary-AML (t/s-AML) were identified, all with PTPN11 mutations noted at the time of AML diagnosis. Two patients had preceding MDS and 3 had preceding MDS/MPN. Median age was 63 years (range, 31-70 years). The most common co-occurring mutations were RUNX1 (5 patients), FLT3-ITD (2 patients) and NRAS/KRAS (3 patients). Chromosome 7 abnormalities were present in 4 of 5 patients with RUNX1 mutations. Cytogenetics were complex or adverse-risk in 9 patients. Eight patients received treatment - 6 with intensive chemotherapy and 2 with HMA + venetoclax. Treatment response was CR/CRi in 3 patients (37.5%). Median PFS was 183 days and median OS in treated patients was 307 days. The only patient with an ongoing response at the time of data cut-off received an allogeneic transplantation in CR1. Three patients with AML had emergence of a PTPN11 mutation at the time of relapse, at 245, 343 and 2262 days after initial diagnosis. PTPN11 was the only new mutation identified in 2 patients, and emerged in conjunction with an NRAS and KDM6A mutation in 1 patient. One patient received treatment, attaining a CRi after HMA + venetoclax, but relapsed 112 days later. The other 2 patients passed at 10 and 21 days after relapse. Conclusions PTPN11 mutations were relatively rare, occurring in only 22 patients with AML during a 3.5-year time span. Stark differences were noted in patients with de novo AML versus t/s-AML and PTPN11 mutations. De novo AML patients frequently demonstrated NPM1 mutations and a normal karyotype, while t/s-AML patients frequently had RUNX1 and FLT3 mutations, as well as adverse cytogenetics. Although the impact of PTPN11 mutations in AML may be influenced by concurrent NPM1 mutations or cytogenetic characteristics, the context of AML may ultimately have the largest impact.

Clinical Characteristics, Genetic Profile and Prognosis of Adult Acute Myeloid Leukemia with NUP98 Rearrangement

Introduction: Nucleoporin 98 ( NUP98) rearrangement has been proposed in 2022 as one type of acute myeloid leukemia (AML) with defining genetic abnormalities. It occurred more often in pediatric leukemia with poor outcome. However, in adult AML with NUP98 rearrangement, patients may show different clinical characteristics, genetic profile and outcome, as we reported here. Method: We retrospectively collected and analyzed the data of adult AML patients with NUP98 rearrangement who were diagnosed at Shanghai Institute of Hematology from May 2019 to December 2022, including clinical characteristics, laboratory examination, genetic abnormalities, treatment strategies and outcome. All patients underwent next generation sequencing and RNA sequencing. Result: A total of 21 AML patients with NUP98 rearrangement were included in this study, counting for 2.3% of all AML patients (930 cases). The median age was 40 (19-64) years old. The median white blood cell and platelet count was 31.1 (1.5-313.6) and 48 (15-140) ×10 9/L, respectively. Interestingly, 11 (52.4%) patients suffered from severe or fatal hemorrhage irrelative with platelet count or coagulative function, including 4 cerebral bleeding (3 died), 1 urgent uterine bleeding, 1 gastro-intestinal bleeding, 1 retina bleeding and 4 massive bleeding of subcutaneous soft tissue or mucous membranes. The FAB types involved M2, M4 and M5. Eight patients carried normal karyotype, 6 were found with t(7;11)(p15;p15), all of whom had NUP98::HOXA9 fusion gene, 2 with +8 and 1 complex karyotype. According to ELN 2022 risk classification, 14 (66.7%) were at intermediate risk and 6 (28.6%) at adverse risk, 1 unclassified. Five fusion partners with NUP98 were detected: NUP98::NSD1 (11 cases), NUP98::HOXA9 (7 cases), NUP98::HOXA11, NUP98::HMGB3 and NUP98::TNRC18 (each with 1 case). Of which NUP98::TNRC18 was first reported by our center (see Cheng WY, et al. Proc Natl Acad Sci U S A. 2022;119(49):e2211429119). NUP98 rearrangement also co-existed with several mutations. FLT3-ITD (12 cases, of which 10 were co-existed with NUP98::NSD1) and WT1 (7 cases) were most frequently occurred. Patients with relapse/refractory disease had more additional mutations than de novo status (Figure 1). Nineteen patients were treated with standard dose of “7+3” induction therapy, and 2 with hypomethylating agents (HMA) plus venetoclax (VEN). Complete remission (CR) was achieved by 8 (38.1%) patients after first induction, 2 (9.5%) early deaths were both due to cerebral hemorrhage. Salvage induction varied from intensive chemotherapy (IC, including “7+3” and CLAG±M) to low-intensity therapy (LIT, including priming chemotherapy±HMA and HMA+VEN). FLT3 inhibitors (FLT3i) were added to 5 patients carrying FLT3-ITD, and they all achieved CR. A total of 15 (71.4%) patients achieved CR after 1-2 courses of induction (8 mainly benefited from IC, 7 mainly benefited from LIT±FLT3i), 1 survived from allogeneic hematopoietic stem cell transplantation (allo-HSCT) without reaching remission before, and 3 died from refractory disease within 6 months. Three patients relapsed after CR, 2 died without allo-HSCT, and the other one survived after CR2 and sequential allo-HSCT. A total of 14 patients underwent allo-HSCT after CR, 7 were measurable residual disease (MRD) negative and 7 were positive by flow cytometry before HSCT, none of them relapsed till the last follow-up. With a median follow-up time of 19.2 months, the median overall survival (OS) and event-free survival (EFS) were not reached, estimated 2-year OS and EFS rate were 66.7% and 57.1%, respectively. For patients achieving CR or not, the median OS were not reached vs 3.2 months (95% CI 0-8.361, P<0.001, Figure 2). Ten patients were diagnosed with NUP98::NSD1 co-occurring with FLT3-ITD (once considered as unfavorable prognosis), ending up with a CR rate of 70%, and a 2-year OS and EFS rate of 80% and 60%, respectively, making no significant difference compared to others ( P=0.236 and 0.725, respectively). Conclusion: Adult AML with NUP98 rearrangement may combine with a set of partner fusion genes and mutations, with NUP98::NSD1 and FLT3-ITD as the most common combination. Both IC an LIT can induce CR, and FLT3i will benefit those with FLT3 mutations, also prevention of fatal bleeding should be paid attention to. After achieving CR with whatever method and whatever MRD status, allo-HSCT is the key to long-term survival.

Metformin Potentiates Gilteritinib Sensitivity Via Targeting PLK1 Signaling: A Strategy to Improve Outcomes and Reduce Costs in Treating FLT3-Mutated Acute Myeloid Leukemia

FLT3 mutations (including FLT3-ITD and FLT3-TKD), occurring in ~30% of acute myeloid leukemia (AML) patients, signal poor prognosis due to elevated relapse risk. Albeit FLT3 tyrosine kinase inhibitors (FLT3 TKI) demonstrated efficacy in treating FLT3-mutated AML in the clinic, there are issues such as high cost, side effects, and high rate of drug resistance/relapse. Hence, an affordable, efficient treatment with lower side effects is needed. Metformin (MET), a cost-effective anti-diabetic drug with minimal side effects, has demonstrated anti-tumor effects (Dowling R et al. Cancer Res. 2007). Here we aimed to determine if combining MET with FLT3 TKI, like Gilteritinib (GLT), could enhance efficacy, reduce side effects and costs in treating FLT3-mutated AML. To this end, we first assessed the IC50 values of MET and GLT across various AML cell lines including those carrying FLT3/ITD (MOLM13, MV4-11, and MA9.3-ITD), FLT3 TKI resistant cells (MOLM13-RES) and those carrying FLT3 wild-type (FLT3/WT) (THP1, NOMO1 and Kasumi-1). MET's IC50 S were consistent (7.284 -12.76 mM) (Fig. 1A), while GLT's varied, with lower values in FLT3/ITD cells (10 nM) and higher in FLT3 TKI resistant (241 nM) and FLT3/WT cells (334-1,053 nM) (Fig. 1B). Using the Chou-Talalay Method, a Combination Index (CI) below 1 in FLT3/ITD and MOLM13-RES cells indicated synergy, whereas it showed antagonism (CI>1) in FLT3/WT cells (Fig. 1C). Both MET and GLT induced cell cycle arrest and apoptosis, with Combo1 (GLT 5 nM + MET 5 mM) matching GLT 10 nM effects; Combo2 (GLT 10 nM + MET 10 mM) amplified these effects (Fig. 1D and E). We next evaluated the potential synergistic effect of MET and GLT in treating TKI-resistance AML in vivo using NRGS mice xeno-transplanted with MOLM13-RES cells. Both bioluminescence imaging and flow cytometry assays showed each treatment alone reduced leukemia burden, and their combination had a synergistic effect, reducing AML burden dramatically (Fig. 1F). While MET or GLT alone doubled overall survival compared to vehicle treatment (56-62 days vs. 26 days), ~90% of the mice treated with the Combo survived over 120 days (Fig. 1G) and their leukemia burden was still minimal, highlighting the synergistic effect and the promising therapeutic potential of this combination in treating FLT3-mutated AML (even with TKI-resistance). To understand the underlying molecular mechanism(s), we performed RNA-seq with vehicle- or drug-treated MOLM13-RES cells, followed by pathway analysis and validation/mechanistic studies, we identified Polo-like kinase 1 (PLK1) as a key target of MET and GLT (Fig. 1H). PLK1's expression is notably suppressed by both treatments (Fig. 1I). Mimicking MET treatment, PLK1 knockdown enhanced GLT sensitivity, reducing IC50 from 259.2 nM to 47-60 nM (Fig. 1J). Conversely, PLK1 overexpression increased GLT's IC50 7-fold (13.07 nM to 95.94 nM) (Fig. 1K), largely reversing MET's effect (data not shown). PLK1, a crucial serine/threonine-protein kinase, influences multiple signaling pathways such as MAPK and mTOR pathways. Upon treating MOLM13 or MOLM13-RES cells with MET and GLT alone or combined, the PLK1 levels and phosphorylation levels of FLT3, STAT5, ERK, and mTOR were decreased, with the most significant decrease occurred upon the combined treatment (Fig. 1L). Depletion and overexpression of PLK1 decreased and increased these phosphorylation levels, respectively (data not shown). Together, our findings suggest that the synergistic therapeutic effect of MET and GLT in treating FLT3-mutated AML is likely through synergistically targeting PLK1 and its downstream pathways. Meanwhile, we executed a retrospective clinical study of FLT3/ITD AML patients who were also diagnosed with diabetes. Metformin users showed a notably longer median OS (13.2 months) than non-MET users (4.5 months, P=0.0197) (Fig. 1M). Despite FLT3/ITD status, FLT3 TKIs were seldom used in China due to high cost. Additionally, PLK1 level was dramatically higher in FLT3/ITD AML cases than in both healthy and FLT3/WT cases (P<0.001) (Fig. 1N), implying PLK1's role in FLT3/ITD's poor prognosis. In summary, our findings suggest a potential synergistic approach in treating FLT3-mutated AML using MET and GLT. This approach could reduce side effects and costs (crucial for developing countries) and improve outcomes. Larger clinical trials are needed to confirm these promising initial findings.

Evaluation of Synergistic Anti-Leukemic Efficacy of PHI-101 in Preclinical Model of FLT3-ITD Acute Myeloid Leukemia

Background: AML is a heterogeneous disease with an overall cure rate of 40-50%. Some types of AML have even poorer prognosis with FLT3 mutant AML patients having only a 20-25% cure rate with chemotherapy alone. In order to improve the outcome for this high-risk AML, a number of tyrosine kinase inhibitors (TKI) have been developed and to date. Given the difficulty of identifying appropriate targets and treatment options for AML, combining drug options for AML treatment may produce clinical benefits. PHI-101 is a selective next-generation type I FLT3 inhibitor that shows potent anti-leukemic activity against AML samples harboring FLT3-ITD and/or TKD mutations. In a clinical trial, PHI-101 demonstrates significant clinical responses and tolerability in refractory or relapsed AML patients as monotherapy. To investigate the optimal way to combine PHI-101 with other therapies, a number of other drugs utilized in treating AML were tested both, in vitro and in vivo to determine synergistic or additive effects that might improve efficacy for relapsed/refractory/elderly FLT3 mutant AML patients. Study Design and Methods: Combination effects of simultaneous versus sequential treatment of PHI-101 with other agents, including daunorubicin, cytarabine, venetoclax (Ven), and azacytidine (Aza) were tested using human leukemia cell lines harboring FLT3-ITD mutations (MV4-11, Molm13, Molm14) or FLT3-wild type as controls. The cell growth inhibition was assessed by CCK-8, MTT and/or CellTiter-Glo assays as well as annexin V-binding by flow cytometry and the Chou-Talalay method was used to calculate the combination index (CI. using Compusyn software. The potential mechanisms of effect on combination therapy were explored by Western blotting of a variety of signal transduction pathways including FLT3 phosphorylation and downstream pathways BCL-2 family expression, and DNA damage. The MV4-11 xenograft mouse model was used to assess in vivo efficacy of PHI-101 combination therapy. Results: Among the substances tested for combination therapy with PHI-101 in FLT3-ITD cell lines MV4-11 and Molm14 cell lines, Aza and Ven treatment both showed synergy with both simultaneous and sequential treatment. Ven was highly synergistic when used simultaneously with PHI-101 in MV4-11 cells. Cell growth inhibition effect (GI 50) of PHI-101, Aza, and Ven used alone was measured first to calculate the CI in combination with increasing concentrations of each drug together of treatment for 72hrs. The GI 50 of PHI-101 in FLT3-mutant cell lines (MV4-11, Molm13, Molm14) were 7.0, 3.8, and 3.4 nM, respectively. The GI 50 of the gilteritinib was 5.7, 10.2, and 10.8 nM, respectively. On the other hand, the GI 50 of Aza were 198.9, 140.4, and 85.4 nM, that of Ven were 38.2, 8.4, and 56.5 nM. PHI-101 was the most efficient antitumor agent compared to other drugs tested in this study. The CI of Aza and PHI-101 was 0.01216 (EC 50), 0.05981 (EC 75), 0.29468 (EC 90) in MV4-11 cells. The observed synergistic effects were confirmed in the other FLT3-ITD cell lines as well. PHI-101 and venetoclax combined therapy in MV4-11 showed synergism (CI<0.1), and the CI was 0.00002 (EC 50), 0.00104 (EC 75), 0.01243 (EC 90). By Western blotting, the combination of Aza or Ven with PHI-101 resulted in a significant induction of p-H2AX and PARP cleavage in the FLT3-ITD cell lines (MV4-11), but not in FLT3-WT cell lines (THP-1). To further validate the synergistic anti-leukemic activity of PHI-101 with these agents, MV4-11-derived mouse xenograft models were generated and treated at various doses. In the MV4-11-xenograft model, PHI-101 alone or combined with Ven or Aza significantly decreased tumor volume. In line with the cell viability data, Ven and Aza combined with PHI-101 induced significant cell-killing in vivo. Conclusion: Treatment of AML cells with the combination of Ven or Aza with PHI-101 in vitro induced rapid induction of apoptosis and inhibition of cell growth that showed significant synergy. In vivo data showed improved efficacy for the combination treatment with these agents. In vitro and in vivo data from the preclinical AML models provides a rationale to evaluate the activity of PHI-101 in combination for patients who are ineligible for more intensive chemotherapeutic induction therapy. Improved anti-leukemic efficacy by combined therapy with PHI-101 represent a promising therapeutic strategy for newly diagnosed or R/R FLT3-mutant AML patients

Efficacy and Safety of Clifutinib, a Novel, Highly Selective, Oral FLT3 Inhibitor, in Patients with FLT3-Mutated Relapsed or Refractory Acute Myeloid Leukemia：Updated Results from a Phase I Study

Background: Patients with relapsed/ refractory (R/R) FLT3-internal tandem duplication positive (FLT3-ITD+) acute myeloid leukemia (AML) have limited treatment options and poor prognosis. Clifutinib is a novel, highly selective, oral FLT-3 inhibitor with potent activity against FLT3-ITD(+) leukemic models both in vitro and in vivo. This study is a first-in-human study of clifutinib, with the purpose of evaluating the safety, tolerability, efficacy, and pharmacokinetic (PK) profile in Chinese patients with R/R FLT3-mutated AML (NCT04827069). Methods: Patients aged ≥18 years with AML who were refractory to ≥ 2 cycles of standard induction chemotherapy or relapsed after achieving remission from previous treatments were enrolled. Previous use of FLT3 inhibitors were allowed. The study included two parts, a dose-escalation part (10 to 100 mg/day cohorts) and a dose-expansion part (40 and 70 mg/day cohorts). The primary endpoints were safety and tolerability, and the secondary endpoints were efficacy [CR(complete remission)/CRh (complete remission with partial hematologic recovery) rate, composite complete remission (CRc: CR+CRh+CRi, CRi defined as complete remission with incomplete hematological recovery) rate, TTR (time to remission), duration of remission (DOR), and overall survival (OS)] and pharmacokinetics (PK). Results: As of May 2023, 75 patients (pts) were enrolled (Figure 1), with a median age of 55 years (range:18-80), and 96.0% pts were FLT3-ITD(+) or TKD(+) [80.0% with ITD(+)/TKD(-), 9.3% with ITD(+)/TKD(UK), 5.3% with ITD(+)/TKD(+), 1.3% with ITD(-)/TKD(+)], 58.7% pts had received ≥2 lines of previous treatment, and 32.0% pts exposed to FLT3 inhibitors. 3 pts experienced dose-limiting toxicities (DLT): one out of 6 pts in the 55 mg/day cohort (Grade 3 QTcF prolongation with ΔQTcF =71 ms) and 2 out of 6 pts in the 100 mg/day cohort (Grade 3 nausea and Grade 3 atrial fibrillation). Therefore, the maximum tolerated dose of clifutinib was 70 mg/day. The most common (rate ≥20%) treatment-related adverse events (TRAEs) included leukopenia (70.7%), thrombocytopenia (68%), neutropenia (64%), anemia (48%), lymphopenia (26.7%), pneumonia (26.7%), hypokalemia (26.7%), aspartate aminotransferase increased (22.7%), alkaline phosphatase increased (21.3%) and alanine aminotransferase increased (20.0%). Grade ≥3 TRAEs occurring in ≥20% pts were leukopenia, thrombocytopenia, neutropenia, anemia, lymphopenia, and pneumonia. Approximately dose-proportional PK parameters were observed across 40-100 mg/day dose range for both single and repeat dosing (the parent drug might approach saturation at 100 mg/day), and median t max ranged from 2 to 6 hours. For efficacy, responses occurred in 28 (40.6%) of 69 FLT3-ITD(+) or TKD(+) efficacy evaluable pts, including 5 (7.2%) CR, 5(7.2%) CRh, 17 (24.6%) CRi, 1 (1.4%) MLFS, and the median TTR was 32 days (range: 26-149 days). The efficacy was better in the 40 mg/day group compared to 70 mg/day and 40-100 mg/day groups, with CR/CRh rate of 21.2% (7/33) vs 8.3% (2/24) vs 14.5% (10/69), CRc rate of 48.5% (16/33) vs 33.3% (8/24) vs 39.1% (27/69), and median DOR of CR/CRh was 3.2 months (95% CI:1.9, NA) vs 0.9 months (95% CI: NA, NA ) vs 3.2 months (95% CI: 0.9, 7.4 ), the median OS was 6.5 months vs 5.4 months vs 6.3 months, respectively. Among FLT3-ITD(+)/TKD(-) subjects administered with clifutinib 40 mg/day, the CR/CRh rate was 23.1% (6/26) with 3 patients achieved CR, median DOR of CR/CRh was 3.7 months, the CRc rate was 53.8% (14/26), and median OS was 7.4 months. Compared to FLT3-ITD(+) or TKD(+) pts, 40 mg dose group exhibited better efficacy in FLT3-ITD(+)/TKD(-) pts. In addition, clifutinib exhibited more potent anti-leukaemic activity in patients received only one line of previous treatment. Among patients experienced only one line treatment of 40 mg dose group, the CR/CRh rate was 30.8% (4/13), the CRc rate was 53.8% (7/13), and the median OS was 7.9 months (Table 1) . Conclusion: This phase 1 study has demonstrated an acceptable safety profile and a significant anti-leukaemic activity of clifutinib in FLT3 mutant R/R AML, with the best response at the dose of 40 mg/day in FLT3-ITD(+)/TKD(-) AML. A confirmatory phase 3 study is currently ongoing to further evaluate the efficacy and safety of clifutinib dosed at 40 mg/day in R/R AML pts after first-line therapy with FLT3-ITD(+)/TKD(-) (NCT05586074). Keywords: Acute myeloid leukemia, FLT3 inhibitor, Clifutinib

Lintuzumab-Ac225, a CD33-Directed Antibody Radiotherapy, Targets AML in a Mutation Agnostic Manner

Introduction Acute myeloid leukemia (AML) is a highly heterogeneous hematologic malignancy with a poor survival prognosis. Recurrent gene mutations are the major obstacle that impact treatment efficacy of AML patients. Actimab-A, an anti-CD33 antibody conjugated with Actinium-225 (Ac-225) alpha particle-emitting radionuclide (lintuzumab-Ac225), has demonstrated promising therapeutic responses in AML patients, including in combination trials with chemotherapy regimen CLAG-M and targeted therapy venetoclax. Because lintuzumab-Ac225 broadly targets myeloid cells via CD33, we hypothesized that anti-leukemic activity is agnostic of genetic abnormalities commonly found in relapsed/refractory AML, including FMS-like tyrosine kinase-3 ( FLT3) mutations and mixed lineage leukemia ( MLL) rearrangements. While small molecule FLT3 and menin inhibitors that target these patient subpopulations show anti-leukemic benefit, most patients eventually relapse. This study uses preclinical models to evaluate the anti-leukemic activity of lintuzumab-Ac225 in FLT3 and MLL mutation harboring AML cells as either a single agent or in combination with FLT3 or menin inhibitors. Methods Lintuzumab-Ac225 was generated by conjugating lintuzumab with p-SCN-Bn-DOTA and subsequently radiolabeled with Ac-225. A viability assay was performed using flow cytometry to assess the response of the FLT3 mutant and MLL rearranged AML cell line MV-4-11 to lintuzumab-Ac225, FLT3 inhibitor (Gilteritinib) or MLL inhibitor (Revumenib) single agents and the combinations. Furthermore, the effects of lintuzumab-Ac225 on AML growth in vivo were investigated using the subcutaneously injected MV-4-11 leukemia xenograft model in nude mice. Results Treatment of MV-4-11 AML cells with lintuzumab-Ac225 revealed a dose-dependent reduction of leukemia cell viability which was significantly more potent relative to cold lintuzumab. Single agent cytotoxicity of Gilteritinib or Revumenib was also observed, but the combination of lintuzumab-Ac225 with FLT3 or MLL inhibitors was additive and synergistic at all dose levels studied. In a preclinical AML model in vivo, each inhibitor delayed tumor growth as a monotherapy. However, the combination of each of these inhibitors with lintuzumab-Ac225 demonstrated statistically significant enhanced tumor control in the MV-4-11 AML model. Conclusions Lintuzumab-Ac225 has potent anti-leukemic activity in AML cells harboring FLT3 or MLL genetic abnormalities. Combination of CD33-targeted radiation with either FLT3 or menin inhibitors significantly improves AML control, suggesting how FLT3 and/or menin efficacy may be augmented by radiation-induced DNA damage. The combination of lintuzumab-Ac225 to existing mutation-targeted standard-of-care may enhance AML targeting and treatment durability versus single-agent approaches.

DNMT3A Mutants Are Enriched in NPMc+ AML and Associated with Adverse Outcome in Childhood AML

Background: Somatic mutations in the DNA methyltransferase 3 alphagene (DNMT3A) are common in adult acute myeloid leukemia (AML), but are rare events in childhood AML (Ho, Ped Blood Cancer, 2011). Missense mutations occur most frequently in the catalytic domain at R882, resulting in loss of enzyme methylation activity and the ability of the enzyme to bind DNA. DNMT3Amutations are associated with adverse outcome in adults, while their impact is understudied in childhood AML. Our objective was to identify the prevalence of DNMT3A -mutated AML across the childhood age spectrum utilizing a large cohort of patients enrolled on pediatric trials and compare findings with adult cohorts. Methods: Pediatric patients treated on two consecutive COG trials with publicly available data were included (n=1607). Mutational profiling was performed by whole genome and transcriptome sequencing methods. Prevalence of DNMT3Amutations, co-occurring mutations, and outcomes (5-year event-free [EFS] and 5-year overall survival [OS]) were analyzed. Results: The prevalence of DNMT3Amutations amongst the entire childhood cohort was 1.2% (n=20/1607). DNMT3A mutations were absent in children <10 years with increased incidence up to 2.6% in patients >10yrs of age. All variants were missense, with the exception of one nonsense mutation and alterations at the 882 residue were the most common (70%). Most importantly, all but 4 DNMT3A mutations occurred in patients with NPM1 mutations (NPMc+; 80%). Conversely, DNMT3A mutations were seen in 9% of all NPM positive patients, demonstrating unique enrichment of this mutation within the NPM1 mutant cohort. Further, R882 mutations were seen in all but a single patient with the dual NPM/DNMT3A variant. It is notable that 11 patients harbored additional FLT3-ITD mutations (triple positive), which we have previously reported to be associated with adverse outcome in adults. In addition to mutations in NPM1 and FLT3, co-occurring variants with DNMT3A were also found in PTPN11 (35%), and WT1, IDH1/2 and MYC each at 10% frequency (Fig.A). Given the recent report of association of NPM1 mutation genotype and association of Type D mutation with adverse outcome (Pigazzi, ASH 2023), we evaluated NPM1 mutation genotype in those with cooperating DNMT3A mutation which demonstrated lack of association of DNMT3A mutations and Type D NPM1 mutations. Current risk classification in COG pediatric AML trials treat NPMc+ patients as favorable risk. Given the prevalence of DNMT3A mutations in NPMc+ patients we inquired whether DNMT3A mutations might modify outcome in this population. The 5 yr EFS estimates for NPMc+; patients with and without DNMT3A was 26.8% vs. 74.8% (p<0.0001; Fig.B) with a corresponding OS estimate at 5yrs of 60.3% vs. 82.2% (p=0.0169). We further concluded that presence or absence of FLT3-ITD does not impact the adverse outcome with similar 5 yr EFS for those with dual NPM1/DNMT3A or triple NPM1/DNMT3A/FLT3-ITD positive AML(20.0% vs. 30.3%respectively). These data are consistent with the adult DNMT3A data previously presented last year (Torabi; ASH 2022; abstract #306) regarding clinical implications of DNMT3A mutation in the setting of cooperating NPM1 mutation. Conclusion: Mutational profiling of children with AML identified DNMT3A mutations in adolescents and young adults and is enriched in those with NPMc+ mutations. As NPMc+ patients are considered to be favorable risk, knowledge of DNMT3A mutations would provide additional information for more precise risk stratification in childhood AML. Children with de novo AML and dual DNMT3A/NPM1 mutations remain at high risk of relapse and adverse outcome regardless of FLT3-ITD status.

DNA Damage Response Constrains Cell Growth and Drives Clonal Hematopoiesis in Telomere Biology Disorders

Telomere biology disorders (TBD) are inherited diseases caused by genetic defects in telomere maintenance. Patients with TBD have critically shortened telomeres, leading to bone marrow failure (BMF) and an increased risk of myeloid neoplasms (MN). We conducted a study to understand the genetic changes driving clonal evolution in TBD patients and their distinct mechanisms compared to normal aging and sporadic myelodysplastic syndrome (MDS). We analyzed acquired genetic alterations in hematopoietic cells from 105 TBD patients. The diagnosis of TBD was made using a combination of clinical history, germline mutation status, and telomere length. Germline mutations were identified in 84% of patients, a family history consistent with TBD was seen in 46%, and 76% of patients had lymphocyte telomere lengths (TL) <1st %ile for their age, while 22% fell between the 1st and 10th %ile. Complications observed in our cohort included BMF (42%), myeloid neoplasms (17%), solid tumors (17%), cirrhosis (14%), and interstitial lung disease (34%). Clonal hematopoiesis was detected in 44 of 105 patients (42%), including 8 of 27 (30%) patients 18 years or younger. Somatic genetic alterations primarily involved the DNA damage response (DDR) pathway, with ATM and TP53 being the most frequently mutated genes (11 ATM mutations in 5 of 80 patients; 5 TP53 mutations in 4 of 84 patients; Fig. 1). Mutations typical of age-related clonal hematopoiesis were seen in 4 patients (3 ASXL1, 1 TET2). Somatic reversion of TBD germline lesions was found in 7 patients. Additionally, 11 somatic mutations were detected in genes involved in DDR, telomere maintenance, and cell senescence, including KAT6B, PALB2, TELO2, TOP1, and RTEL1. MDS-associated gene mutations were found in 15 patients (18%), 8 in the setting of MN. The most common mutations affected spliceosome genes with U2AF1 p.S34F and SF3B1 being most notable, including 1 U2AF1 S34F identified in a 15-year-old. Mutations in NPM1, RUNX1, WT1, SF3B1, and FLT3 were identified only after malignant transformation. Acquired cytogenetic changes were observed in 16 of 87 evaluable patients (18%), 8 in the setting of MN, and included gain of 1q in 5 patients (5.7%). Two patients with TP53 mutations developed a complex karyotype (Fig 1). To understand selective pressures contributing to clonal hematopoiesis development in TBD, we analyzed transcriptional changes in bone marrow (n=2) and peripheral blood (n=1) mononuclear cells (MNCs) of 3 TBD patients with different germline lesions using single cell RNA sequencing (scRNASeq). MNCs from TBD patients exhibited significant differences compared to healthy controls, showing downregulation of MYC targets, reduced translation, cell cycle arrest, and upregulation of ATM-dependent DDR pathway and FAS pathway (Fig 2). We hypothesized that mutations in DDR pathway genes, particularly somatic ATM loss, enable TBD hematopoietic stem and progenitor cells to overcome telomere-induced DDR induction and premature senescence. Consistent with our hypothesis, low dose ATM inhibition in TBD patients' fibroblasts significantly enhanced growth rate of TERC-mutated and DKC1-mutated cells, whereas control fibroblasts were unaffected. Somatic mutations in ATM in our cohort were typically observed in patients with TERC-mutated TBD (3 of 5, 3 of 34 with TERC-mutated TBD), very low TL, and extra-hematopoietic manifestations. Of the 11 ATM mutations, 3 were predicted loss of function and 4 were missense kinase domain mutations, known or predicted to result in loss of kinase activity. Somatic ATM loss occurred both as heterozygous or compound heterozygous mutations. The development of ATM mutations alone was not causative of malignancy; however, 2 patients with somatic ATM mutations developed myeloid neoplasms after acquisition of additional mutations (subclonal mutation in NPM1 in one patient and clonal replacement with a TP53-mutant clone in another patient). In conclusion, our findings highlight the role of telomere dysfunction-induced DDR and cellular senescence in bone marrow failure and clonal selection in TBD. ATM loss selectively enhances growth of TBD cells by inhibiting DDR activation which may ameliorate marrow failure but has the potential to increase the risk of myeloid neoplasms after acquisition of additional genetic events. Future studies should explore the possibility of a therapeutic window involving very low doses of ATM inhibition in TBD.

Outcomes of Extramedullary Acute Myeloid Leukemia with Gemtuzumab Ozogamicin: Real-World Experience

Introduction: Extramedullary AML (EM AML) is characterized by the presence of leukemic cells in organs or tissues outside of the blood or bone marrow and remains a therapeutic challenge with dismal response rates to standard chemotherapy and short overall survival. Gemtuzumab Ozogamicin (GO) is an anti-CD33 antibody drug conjugate currently approved for single-agent therapy or in combination regimens for CD33+ relapsed/refractory (R/R) or newly diagnosed (ND) AML, respectively. Although GO is an active drug in AML, the optimal employment of this agent for treatment of EM AML at initial diagnosis, or at relapse, remains to be defined. Methods: A retrospective chart review on outcomes of GO in adults with EM AML at our institute from 2000 to 2023 was performed. Variables collected included age, sex, type of myeloid malignancy, and European LeukemiaNet (ELN) risk, bone marrow, peripheral blood and radiographic involvement, Response Evaluation Criteria in Solid Tumors (RECIST), prior lines of treatments, including stem cell transplant, next-generation sequencing (NGS), cytogenetics, mutational profile, and overall survival (OS). We screened patients with a diagnosis of EM AML who received GO at any point during their EM AML therapy. Patients with only CNS involvement as the extramedullary site were excluded. The aims of this study were to characterize responses and potential clinical benefit of EM AML to GO based regimens in the upfront and R/R settings. Results: 32 patients(pts) with EM AML received GO: 8 (25%) were ND and received GO-based induction regimen, while 22 (68.75%) received GO for R/R AML, and 2 (6.25%) patients received GO both at initial diagnosis and relapse. The median age of patient with ND EM AML was 66 years (y) (range: 28-84), and 60.5 (43-73) y in R/R EM AML. Twenty-four (75%) were men. One (12.5%) ND EM AML and 5 (10.1%) R/R EM AML had >1 extramedullary sites involved. The most frequent sites of EM-AML were skin (25%), lymph nodes (25%), soft tissues (25%), solid organs (25%), and visceral body cavity fluids (12.5%). Based on ELN 2022 risk group criteria, 17 patients were adverse, 8 with intermediate, and 3 with favorable risk. Next-Generation Sequencing (NGS) available for 21 patients identified mutations in TP53 (14.28%), FLT3 (19.04%), NPM1 (19.04%), KMT2A (19.04%), and ASXL1 (19.04%) as the most common mutations. Normal karyotype was noted in 6 (25%) R/R EM AML, while complex karyotype was present in 1 (12.5%) ND EM AML and 10 (41.67%) of R/R EM AML. While none of the ND pts had prior myeloid malignancy, R/R pts had prior AML (15), MDS (2), MDS-EB (1), CMML (1), therapy-related AML (1), myelofibrosis (1), and myeloid sarcoma (1). Concomitant bone marrow involvement at identification of EM AML was present in most ND cases (7/8, 88%) and R/R settings (16/23, 69.56%) (Table 1). Combination 7+3 plus GO was most frequently administered for ND EM AML (3/8) and R/R EM AML (8/24, 33%). Eleven patients had measurable radiologic findings prior to and following GO. Median OS was 10.91 months (m) (range: 0.2 to 27.1) for ND EM AML and 1.58 m (range: 0.7 to 7.5) for R/R EM-AML (Figure 1). 3 of 8 newly diagnosed EM-AML underwent allogeneic bone marrow transplant (AlloBMT) after GO based induction, followed by relapsed EM AML in 1 patient. Despite 50 percent of R/R EM AML pts undergoing prior AlloBMT, none had a durable disease-free response and received GO after relapse. Based on RECIST criteria, 7 of 11 (63.63%) pts achieved a response including 1 Complete Response (disappearance of all target lesions), 6 Partial Response (at least a 30% decrease in the sum of target lesions), and 2 Stable Disease (neither sufficient shrinkage nor increase). The 30-day mortality for ND and R/R were 12.5% and 8.33%, respectively. The 60-day mortality for ND and R/R were 25% and 50%, respectively. Conclusion: Our real-world single-institute experience in patients with EM AML suggests that GO combined with chemotherapy in the upfront setting results in promising outcomes with high overall response rates (CR 50%, PR 13%) by RECIST criteria, durable remissions, and prolonged overall survival in largely favorable and intermediate risk AML. However, despite high partial response rates (4% CR, 50% PR) following GO-based therapy in R/R EM AML, survival was less than 2 months likely due to the high proportion of patients in this cohort with poor risk disease. Further investigations and larger studies are warranted to establish the optimal use of GO in EM AML.

Validation of the Prognostic Risk Signatures for Older Patients with Acute Myeloid Leukemia Treated with Hypomethylating Agents and Venetoclax

Introduction: Hypomethylating agents (HMA) with Venetoclax (Ven) is the standard of care for patients with acute myeloid leukemia (AML) ≥ 75 yrs of age or not candidates to intensive treatment. Döhner, et al. (ASH 2022) demonstrated that the European LeukemiaNet (ELN) risk classifications do not accurately predict prognosis in HMA-Ven treated patients. A prognostic risk signature classification (PRSc) was proposed, stratifying patients by RAS, FLT3 and TP53 mutations alone. We report a validation of this PRSc in a large cohort of patients treated with HMA-Ven. Methods: This unicentric analysis included patients older than 60 years old with newly diagnosed treated with HMA-Ven in different treatment protocols. Responses were assessed with the ELN-2022 criteria. The PRSc allocated patients with [ K/N]- RAS or FLT3-ITD mutations in the intermediate benefit group, patients with TP53 in the lower benefit group, whereas patients with AML lacking these mutations were allocated in the higher benefit group. Cumulative incidence (CI) was calculated for pts achieving remission with death and relapse as competing events. Results: A total of 179 patients were included, diagnosed between 11/2014 and 12/2021. Median age was 74 yrs old (range, 61-89) and 58% were male. 31% of patients had diploid cytogenetics and 35% had complex karyotype. According to the ELN 2022 risk category, 30 (17%), 15 (8%) and 114 (64%) patients were allocated in the favorable, intermediate and adverse risk group, respectively. According to the PRSc, 75 (42%), 31 (17%) and 54 (30%) were allocated in the higher, intermediate and lower benefit group, respectively. In the PRSc intermediate benefit group, 21 patients had NRAS mutations, 9 patients had KRAS mutation and 7 patients had FLT3-ITD. Patients received treatment with decitabine 10 days with Ven (n=89, 50%), decitabine 5 days with Ven (n=69, 38%), oral decitabine 5 days with Ven (n=14, 8%) and Azacitidine 7 days with Ven (n=7, 4%). The overall response rate (ORR) was 70% (126/179), including 96 pts (54%) achieving complete remission (CR) rate and 30 (17%) having CR with incomplete hematologic recovery (CRi). The ORR for patients allocated in the ELN 2022 favorable, intermediate and adverse risk was 90% (27/30), 93% (14/15) and 63% (72/114). According to the PRSc, the ORR was 87% (65/75), 55% (17/31) and 59% (32/54) for patients of the higher, intermediate and lower benefit group, respectively. The median number of cycles to best response was 1 (1-8), and 22 patients (12%) underwent allogeneic stem cell transplantation. After a median follow-up of 35 months, the median overall survival (OS) was 11 months. According to the ELN 2022 classification, the mOS was 44, 13 and 8 months (p<0.001, C-index=0.6). When applying the PRSc, the median OS was 30, 12 and 5 months for higher, intermediate and lower benefit group (p<0.001, C-index=0.66). Median event-free survival (EFS) was 8 months, being 30, 8, and 5 months for ELN 2022 favorable, intermediate and adverse group, respectively (p<0.001, C-index=0.62). When applying the PRSc, the median EFS was 18, 8 and 4 months for higher, intermediate and lower benefit group, respectively (p<0.001, C-index=0.65). The 2-yr CI of relapse and death was 47% and 22%, respectively. By the ELN 2022 subgroups, the 2-yr CI of relapse was 29%, 43% and 55% for favorable, intermediate and adverse groups, respectively (p=0.1). The 2-yr CI of death was 12%, 21% and 25% for favorable, intermediate and adverse groups, respectively (p=0.4). By the PRSc, the 2-yr CI of relapse was 26%, 70% and 60% for higher, intermediate and lower benefit group, respectively (p=0.004). The 2-yr CI of death was 20%, 6% and 33% for higher, intermediate and lower benefit group, respectively (p=0.1). Conclusion: The PRSc classification can stratify 3 different groups of patients with distinct outcomes. In the present study the 3 categories defined by the PRSc have very similar survival than the median OS previously reported (27, 12 and 5 months for higher, intermediate and lower benefit group), with a better performance according to the C-index. Signaling mutations ( RAS or FLT3-ITD) as well as TP53 mutations represent a challenge with HMA-Ven, in which novel treatments or combinations are warranted to improve outcomes.