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Background: Fms-like Tyrosine Kinase 3 (FLT3) has an important role to perform in hematopoietic malignancy pathogenesis. Hence the focus of several studies has recently been FLT3. Objective: To determine the molecular characterization of FLT3 mutation in patients of acute leukemia. Methodology: This descriptive analysis was carried out from January 2018 to December 2018 upon a sample of 94 newly diagnosed cases of acute leukemia (chosen via non-probability, consecutive sampling) presenting to the Department of Pathology, Liaquat University of Medical & Health Sciences, Jamshoro. After taking informed written consent, Data were obtained from laboratory records and patient interviews were noted down with the help of structured questionnaire. SPSS v. 20.0 was used for analysis of the obtained data. Results: The mean age of participants was 41 years (±19 SD). 59.57% of the sample comprised of males while the remaining 40.43% were females. Among the total of 94 patients studied, patients with acute lymphoblastic leukemia (ALL) were 41 in number while those with acute myeloid leukemia (AML) were 53. The polymerase chain reaction verified FLT3 mutations in 6 (11.32%) out of 53 AML cases and 2 (4.88%) among 41 ALL cases. In acute myeloid leukemia (AML) FLT3 mutation was more prevalent among the older age set (51 and above), while in acute lymphoblastic leukemia (ALL) the FLT3 mutation was more commonly seen a comparatively younger patient age set (21 to 30 years). Conclusion: It was found out that the FLT3 mutations are not uncommon in our study setting. With a greater prevalence observed among older male patients. AML was more common than ALL, with greater incidence rate of FLT3 mutations observed in the AML patients.

Background Patients diagnosed with acute myeloid leukemia with a FLT3 mutation (FLT3+ AML) have historically had poor outcomes. While the addition of the FLT3 inhibitors to induction therapy has been shown to improve survival outcomes in FLT3+ AML, interactions and overlapping toxicities between FLT3 inhibitors and standard of care medications used during induction therapy (e.g. azole antifungals, anthracyclines) and logistical barriers have complicated their use. To avoid these concerns, our institution has opted to defer initiation of midostaurin until after completion of induction therapy. However, to our knowledge no study confirming the effectiveness of this strategy for real world FLT3 inhibitor use has been published. Methods We performed a single center, propensity-score matched, retrospective cohort study characterizing efficacy and safety of our strategy for use of FLT3 inhibitors in the treatment of FLT3+ AML. The primary outcome was median event-free survival (EFS), while secondary endpoints included median overall survival (OS), overall response rate (ORR), 30-day mortality, duration of neutropenia, duration of thrombocytopenia, consolidation cycle delays, documented infections, and all-cause hospital readmission. Results A total of 83 FLT3+ AML patients treated with intensive induction therapy were included in the study, of whom 48 were propensity-score matched and analyzed. Baseline characteristics were similar between the patients who received a FLT3 inhibitor after induction therapy and the historical control arm. Median EFS was not significantly different but compared favorably between the FLT3 inhibitor cohort and historical controls (not reached vs 8 months, p = 0.343) with 18-month EFS of 54% and 43% for the two cohorts, respectively. Similarly, no significant differences were noted with regard to median OS (not reached vs 28.7 months, p = 0.752), ORR (79.2% vs 79.2%), or safety outcomes between groups. Conclusion Compared to historical controls, addition of a FLT3 inhibitor to intensive chemotherapy post-induction may improve EFS or OS in a real world patient cohort with longer follow-up and a larger sample size. The omission of midostaurin in induction allowed for the use of an azole antifungal and the intensification of anthracycline dose may have contributed to high remission rates in both groups.

The t(1;11)(p32;q23) translocation is a rare but recurrent cytogenetic aberration in acute myeloid leukemia (AML) and B-cell acute lymphoblastic leukemia (B-ALL). This translocation was initially shown to form a fusion gene between KMT2A exon 8 at 11q23 and EPS15 exon 2 at 1p32 in AML. Activating mutations of FLT3 are frequently found in AML but are very rare in ALL. Here, we describe a 75-year old woman who was diagnosed with B-ALL since her bone marrow was made up of 98.2% lymphoblasts. These blasts were positive for CD19, CD22, CD79a, CD13, and CD33 but negative for CD10 and myeloperoxidase. The karyotype by G-banding and spectral karyotyping was 46,XX,t(1;11)(p32;q23). Expression of KMT2A/EPS15 and reciprocal EPS15/KMT2A fusion transcripts were shown: KMT2A exon 8 was in-frame fused to EPS15 exon 12, indicating that this fusion transcript was a novel type. Considering three reported B-ALL cases, EPS15 breakpoints were markedly different between AML (exon 2) and B-ALL (exons 10-12). Furthermore, an uncommon type of FLT3 mutation in the juxtamembrane domain was detected: in-frame 4-bp deletion and 10-bp insertion. Accordingly, our results indicate that the novel type of KMT2A/EPS15 fusion transcript and FLT3 mutation may cooperate in the pathogenesis of adult B-ALL as class II and class I mutations, respectively.

The prognosis of patients with relapsed or refractory acute myeloid leukemia (R/R AML) is dismal with salvage standard approaches, and mutations of FMS-like tyrosine kinase 3 ( FLT3) gene, occurring in around 30% of AML patients may confer even poorer outcomes. Several targeted tyrosine kinase inhibitors have been developed to improve FLT3-mutated AML patient´s survival. Gilteritinib, a highly specific second-generation class I oral FLT3 inhibitor, has demonstrated superiority to salvage chemotherapy (SC) in R/R FLT3 mutated AML based on significantly longer OS in the gilteritinib arm than in the SC arm. Gilteritinib is generally well tolerated, but some clinically relevant adverse events should be monitored, especially myelosuppression, QTc prolongation and differentiation syndrome, usually manageable (dose reductions, interruption or discontinuation) and reversible. We discuss clinical development, efficacy, safety and mechanisms of resistance of gilteritinib in the treatment of R/R patients with FLT3 mutated AML.

The FLT3 inhibitor gilteritinib has clinical activity in patients with FLT3‐mutated (FLT3 mut+) relapsed/refractory (R/R) acute myeloid leukemia (AML). The impact of FLT3 mutation clearance and the achievement of composite complete remission (CRc) and complete remission/complete remission with partial hematologic recovery (CR/CRh) on overall survival (OS) in patients with FLT3 mut+ R/R AML treated with single‐agent gilteritinib in a phase 1/2 trial were evaluated. Using next‐generation sequencing, a FLT3‐ITD variant allele frequency of ≤10−4 was used to define FLT3‐ITD clearance in patients with no morphologic leukemia (ie, CRc). A total of 108 patients with FLT3‐ITD‐positive (FLT3‐ITD+) R/R AML were analyzed; 95 of these patients had received ≥80‐mg/day gilteritinib. Ten of the 95 patients had FLT3‐ITD clearance; eight of these 10 patients achieved CRc and were considered negative for measurable residual disease. There was a trend toward longer OS in patients who attained CRc with FLT3‐ITD clearance (131.4 weeks) versus those who achieved CRc and did not have FLT3‐ITD clearance (n = 41; 43.3 weeks; HR = 0.416; p = 0.066). Among patients treated with ≥80‐mg/day gilteritinib who achieved CR/CRh (n = 24), seven had FLT3‐ITD clearance. Among patients who received 120‐mg/day gilteritinib, those who achieved CR/CRh had a longer median OS (70.6 weeks) and higher 52‐week survival probability (66.7%) than patients who did not achieve CR/CRh (n = 71; median OS, 41.7 weeks; 52‐week survival probability, 20.2%). Overall, these data suggest that gilteritinib can induce deep molecular responses in patients with FLT3‐ITD+ R/R AML, and in the setting of CRc or CR/CRh, these responses may be associated with prolonged survival., In patients with FLT3‐mutated relapsed/refractory acute myeloid leukemia, the FLT3 inhibitor gilteritinib induced deep molecular responses characterized by FLT3–internal tandem duplication (FLT3‐ITD) mutation clearance. Among patients who achieved morphologic remission with gilteritinib therapy, FLT3‐ITD mutation clearance was associated with a trend toward longer survival.

(1) Background: The aim of our study was the complex assessment of WT1 variants and their expression in relation to chromosomal changes and molecular prognostic markers in acute myeloid leukemia (AML). It is the first multidimensional study in Polish AML patients; (2) Methods: Bone marrow aspirates of 90 AML patients were used for cell cultures (banding techniques and fluorescence in situ hybridization), and to isolate DNA (WT1 genotyping, array comparative genomic hybridization), and RNA (WT1 expression). Peripheral blood samples from 100 healthy blood donors were used to analyze WT1 rs16754; (3) Results: Allele frequency and distribution of WT1 variant rs16754 (A;G) did not differ significantly among AML patients and controls. Higher expression of WT1 gene was observed in AA genotype (of rs16754) in comparison with GA or GG genotypes—10,556.7 vs. 25,836.5 copies (p = 0.01), respectively. WT1 mutations were more frequent in AML patients under 65 years of age (p < 0.0001) and affected relapse-free survival (RFS). The presence of NPM1 or CEBPA mutations decreased the risk of WT1 mutation presence, odds ratio (OR) = 0.11, 95% CI 0.02–0.46, p = 0.002 or OR = 0.05, 95% CI 0.006–0.46, p = 0.002, respectively. We observed significantly higher WT1 expression in AML CD34+ vs. CD34−, −20,985 vs. 8304 (p = 0.039), respectively. The difference in WT1 expression between patients with normal and abnormal karyotype was statistically insignificant; (4) Conclusions: WT1 gene expression and its rs16754 variant at diagnosis did not affect AML outcome. WT1 mutation may affect RFS in AML.

Background Second-generation FLT3-inhibitors (FLT3i) demonstrated single-agent composite CR rates (CRc) of 45–55% in patients with relapsed/refractory (R/R) FLT3-mutated AML in phase II/III trials. However, > 85% of patients treated were prior FLT3i naïve. The response rates to sequential FLT3i exposure remain poorly defined. Methods We retrospectively reviewed patients with FLT3-mutated AML between November 2006 and December 2019. Results In frontline patients treated with a FLT3i (cohort 1), the CRc rates and median overall survival (OS) with the first (n = 56), second (n = 32), and third FLT3i-based (n = 8) therapy were 77%, 31%, and 25%, and 16.7 months, 6.0 months, and 1.4 months, respectively. In patients receiving a FLT3i-based therapy for the first time in a R/R AML setting (cohort 2), the CRc rates and median OS were 45%, 21%, and 10%, and 7.9 months, 4.0 months, and 4.1 months with the first (n = 183), second (n = 89), and third/fourth (n = 29) FLT3i-based therapy, respectively. In cohort 1, CRc rates with single-agent FLT3i (n = 21) versus FLT3i-based combinations (n = 19) in second/third sequential FLT3i exposures were 19% versus 42%, respectively. In cohort 2, the CRc rates with single-agent FLT3i (n = 82) versus FLT3i-based combinations (n = 101) in first FLT3i exposure were 34% versus 53%, respectively, and those with single-agent FLT3i (n = 63) versus FLT3i-based combinations (n = 55) in second/third/fourth sequential FLT3i exposures were 13% versus 25%, respectively. Conclusion CRc rates drop progressively with sequential exposure to FLT3i’s in FLT3-mutated AML. In all settings, CRc rates were higher with FLT3i-based combinations compared with single-agent FLT3i therapy in similar FLT3i exposure settings.

Approval of midostaurin, a multikinase inhibitor, in combination with chemotherapy for the treatment of adults with newly diagnosed FLT3 mutation–positive acute myeloid leukemia, was based on the p...

Tyrosine kinase domain (TKD) mutations contribute to acquired resistance to FMS-like tyrosine kinase 3 (FLT3) inhibitors used to treat FLT3-mutant acute myeloid leukemia (AML). We report a cocrystal structure of FLT3 with a type I inhibitor, NCGC1481, that retained potent binding and activity against FLT3 TKD and gatekeeper mutations. Relative to the current generation of advanced FLT3 inhibitors, NCGC1481 exhibited superior antileukemic activity against the common, clinically relevant FLT3-mutant AML cells in vitro and in vivo.

Background. FLT3 gene is an important prognostic molecular marker in acute myeloid leukemia (AML). However, the detection of FLT3 mutations presents a challenge. Aim. To compare techniques used for the detection of FLT3 mutations, and to develop a test-system based on polymerase chain reaction (PCR) for quick and reliable determination of FLT3 mutation status. Materials & Methods. Bone marrow samples obtained from AML patients were subjected to examination. To detect FLT3-ITD и FLT3-TKD mutations PCR was performed with subsequent agarose gel electrophoresis visualization. The results were verified by Sanger sequencing. The data obtained using our test-system were compared with widely applied commercial kit ‘FLT3 Mutation Assay for Gel Detection’ by Invivoscribe. Results. To determine the FLT3 mutation status a PCR test was developed. This technique was validated on 22 bone marrow samples obtained from AML patients. FLT3-ITD mutation was detected in 4 patients, 3 patients showed FLT3-TKD mutation. In 1 patient both mutations were identified. These results fully corresponded to the molecular genetic analysis of FLT3, performed by ‘FLT3 Mutation Assay for Gel Detection’. The chosen technique was validated using Sanger sequencing data analysis. Conclusion. The article offers the review of all existing FLT3 mutation screening techniques and describes the experience of developing the PCR test for FLT3-ITD and FLT3-TKD mutation detection. The chosen technique is affordable and easy to use compared with the others. The present study with its applied nature can provide guidance for both doctors and researchers.

Background: Associated with poor prognosis, FMS-like tyrosine kinase 3 (FLT3) mutation appeared frequently in acute myeloid leukemia (AML). Herein, we aimed to identify the key genes and miRNAs involved in adult AML with FLT3 mutation and find possible therapeutic targets for improving treatment. Materials: Gene and miRNA expression data and survival profiles were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. EdgeR of R platform was applied to identify the differentially expressed genes and miRNAs (DEGs, DE-miRNAs). Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed by Metascape and DAVID. And protein-protein interaction network, miRNA-mRNA regulatory network and clustering modules analyses were performed by STRING database and Cytoscape software. Results: Survival analysis showed FLT3 mutation led to adverse outcome in AML. 24 DE-miRNAs (6 upregulated, 18 downregulated) and 250 DEGs (54 upregulated, 196 downregulated) were identified. Five miRNAs had prognostic value and the results matched their expression levels (miR-1-3p, miR-10a-3p, miR-10a-5p, miR-133a-3p and miR-99b-5p). GO analysis showed DEGs were enriched in skeletal system development, blood vessel development, cartilage development, tissue morphogenesis, cartilage morphogenesis, cell morphogenesis involved in differentiation, response to growth factor, cell-substrate adhesion and so on. The KEGG analysis showed DEGs were enriched in PI3K-Akt signaling pathway, ECM-receptor interaction and focal adhesion. Seven genes (LAMC1, COL3A1, APOB, COL1A2, APP, SPP1 and FSTL1) were simultaneously identified by hub gene analysis and module analysis. SLC14A1, ARHGAP5 and PIK3CA, the target genes of miR-10a-3p, resulted in poor prognosis. Conclusion: Our study successfully identified molecular markers, processes and pathways affected by FLT3 mutation in AML. Furthermore, miR-10a-3p, a novel oncogene, might involve in the development of FLT3 mutation adult AML by targeting SLC14A1, ARHGAP5 and PIK3CA.

The fms-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib is indicated for relapsed or refractory (R/R) FLT3-mutated acute myeloid leukemia (AML), based on its observed superior response and survival outcomes compared with salvage chemotherapy (SC). Frontline use of FLT3 tyrosine kinase inhibitors (TKIs) midostaurin and sorafenib may contribute to cross-resistance to single-agent gilteritinib in the R/R AML setting but has not been well characterized. To clarify the potential clinical impact of prior TKI use, we retrospectively compared clinical outcomes in patients with R/R FLT3-mutated AML in the CHRYSALIS and ADMIRAL trials who received prior midostaurin or sorafenib against those without prior FLT3 TKI exposure. Similarly high rates of composite complete remission (CRc) were observed in patients who received a FLT3 TKI before gilteritinib (CHRYSALIS, 42%; ADMIRAL, 52%) and those without prior FLT3 TKI therapy (CHRYSALIS, 43%; ADMIRAL, 55%). Among patients who received a prior FLT3 TKI in ADMIRAL, a higher CRc rate (52%) and trend toward longer median overall survival was observed in the gilteritinib arm versus the SC arm (CRc = 20%; overall survival, 5.1 months; HR = 0.602; 95% CI: 0.299, 1.210). Remission duration was shorter with prior FLT3 TKI exposure. These findings support gilteritinib for FLT3-mutated R/R AML after prior sorafenib or midostaurin.

Introduction FLT3 inhibitors have been recently introduced as novel treatment targets in patients with FLT3-mutated acute myeloid leukemia (AML). Midostaurin is an oral multikinase inhibitor that targets multiple receptor tyrosine kinases including FLT3 and has been approved for the treatment of AML with FLT3 mutations in patients candidates for intensive chemotherapy. This article presents an updated overall overview of the use of midostaurin in clinical practice. Areas covered Tests and examinations to be performed before the use of midostaurin, antifungal and antimicrobial treatment, as well as antifungal and antimicrobial prophylaxis are discussed. Practical tips for the treatment of QTc interval prolongation and heart failure are also presented. Expert opinion Midostaurin is the first agent showing significant survival benefit when combined with chemotherapy in FLT3-mutated AML patients. Optimal use of midostaurin should be a priority, being essential to know the interactions with other drugs like strong CYP3A4 inhibitors or inducers, which are particularly used in the concomitant treatment of AML patients and may increase toxicity or decrease therapeutic benefit. The active role of hematologists and nursing teams is crucial to ensure patient adherence to midostaurin treatment and to minimize adverse effects by administrating the optimal dose for each situation.

Background Midostaurin, a multikinase inhibitor with significant activity against FLT3, was approved in combination with chemotherapy (CT) for treatment of pts with newly diagnosed (ND) FLT3-mutated AML based on the CALGB 10603/RATIFY trial (NCT00651261; Stone et al, NEJM 2017). The A2408 study (NCT03379727) confirmed the efficacy/safety of midostaurin in FLT3-mutated AML and extended the findings to older pts (≥60 y) and different CT regimens (Sierra et al, ASH 2020). As midostaurin inhibits both mutant and wild-type (WT) FLT3 (Weisberg et al, Cancer Cell 2002), the UNIFY trial (NCT03512197) was conducted to evaluate midostaurin in FLT3-mutation negative (MN) AML. Here, we report clinical outcomes and MRD results from UNIFY. Methods This randomized, double-blinded, multicenter, placebo (PBO)-controlled, ph 3 study evaluated midostaurin + CT in pts with ND FLT3-MN (mutant to WT signal ratio Results UNIFY was stopped in Sep 2019 on the recommendation of the data monitoring committee, based on an interim analysis of EFS (N = 359; HR, 1.08 [95% CI, 0.78-1.5]; data cutoff, 15 May 2019) that met the futility criterion. Final analysis occurred after the last pt discontinued and the study was closed (data cutoff, 31 Mar 2021). 501 pts were randomized to midostaurin (n = 250) or PBO (n = 251). Median age was 56 y (54% MRD was analyzed irrespective of treatment because no difference in MRD− rates was found between midostaurin and PBO (Table). Among randomized pts, 205 (41%) were MRD− ( Conclusion Results from UNIFY are consistent with the safety/tolerability profile previously reported for midostaurin, but do not show efficacy for midostaurin in FLT3-MN AML; this suggests that the clinical effect of midostaurin in AML is primarily in the FLT3-mutated setting. Exploratory MRD analyses (to be interpreted with caution due to limited follow-up, as the study was stopped 1.2 y after first pt was randomized) suggest a trend toward longer survival for pts in remission who are MRD− at the end of IND and support the utility of assessing MRD via a combined LAIP/DfN approach. Figure 1 Figure 1. Disclosures Cloos: Takeda: Research Funding; Helsinn: Other: MRD assessments; Navigate: Patents & Royalties: Royalties for MRD analyses; DC-One: Other: MRD assessments, Research Funding; Genentech: Research Funding; Janssen: Research Funding; Novartis: Consultancy, Other: MRD assessments, Research Funding; Astellas: Speakers Bureau; Merus: Other: MRD assessments, Research Funding. Montesinos: Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Forma Therapeutics: Consultancy; Stemline/Menarini: Consultancy; Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Tolero Pharmaceutical: Consultancy; Glycomimetics: Consultancy; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Agios: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau. Fiedler: Daiichi Sankyo: Consultancy, Other: support for meeting attendance; Pfizer: Consultancy, Research Funding; Celgene: Consultancy; Morphosys: Consultancy; Abbvie: Consultancy, Honoraria; Jazz Pharmaceuticals: Consultancy, Other: support for meeting attendance; Amgen: Consultancy, Other: support for meeting attendance, Patents & Royalties, Research Funding; Servier: Consultancy, Other: support for meeting attendance; Stemline: Consultancy; Novartis: Consultancy; ARIAD/Incyte: Consultancy. Müller: GSK: Consultancy; Janssen: Other: Honoraria for educational event; Celgene/BMS: Honoraria; Abbvie: Honoraria; Jazz: Honoraria; Amgen: Honoraria; Sandoz/Novartis: Honoraria; Sanofi: Honoraria; Takeda: Honoraria. Sica: Pfizer: Honoraria. Westermann: Astellas: Honoraria; Pfizer: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; BMS: Honoraria; Novartis: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Stem Cell Line: Consultancy, Honoraria. Döhner: Pfizer: Research Funding; Jazz: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Helsinn: Consultancy, Honoraria; Berlin-Chemie: Consultancy, Honoraria; Agios: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Astex: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; GEMoaB: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding; Ulm University Hospital: Current Employment; Novartis: Consultancy, Honoraria, Research Funding; Oxford Biomedicals: Consultancy, Honoraria. Levis: Pfizer: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen, Astellas Pharma, Daiichi-Sankyo, FujiFilm, and Menarini: Honoraria; Astellas and FujiFilm: Research Funding; Takeda: Honoraria. Ossenkoppele: Jazz: Consultancy, Honoraria; Abbvie, AGIOS, BMS/Celgene Astellas,AMGEN, Gilead,Servier,JAZZ,Servier Novartis: Consultancy, Honoraria; Agios: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Servier: Consultancy, Honoraria. Stone: Astellas: Membership on an entity's Board of Directors or advisory committees; Onconova: Consultancy; Aprea: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy; Actinium: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy; Bristol Myers Squibb: Consultancy; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Foghorn Therapeutics: Consultancy; Innate: Consultancy; Janssen: Consultancy; Jazz: Consultancy; Celgene: Consultancy; Boston Pharmaceuticals: Consultancy; BerGen Bio: Membership on an entity's Board of Directors or advisory committees; Gemoab: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Agios: Consultancy, Research Funding; Macrogenics: Consultancy; Syndax: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy, Research Funding. Koenen: Novartis Pharma AG: Current Employment. Bengoudifa: Novartis Pharma AG: Current Employment. Cheng: Novartis Pharmaceuticals Corporation: Current Employment. Medts: Novartis Pharma AG: Current Employment. Heidinger: Novartis Pharma AG: Current Employment. Sachs: Novartis Pharma AG: Current Employment. Sierra: Janssen: Other: Educational grant; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Other: Educational grant; Amgen: Other: Educational grant; Pfizer: Honoraria; BMS Celgene: Honoraria, Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau; Alexion: Other: Educational grant; Jazz Pharmaceuticals: Research Funding.

Simple Summary AML is a genetically heterogeneous disease with a median age of diagnosis between 60 and 70 years. Thus, many AML patients are not eligible for intensive chemotherapy. Often, the disease is accompanied by a poor prognosis due to high-risk genetic features or due to antecedent hematologic disorders (e.g., myelodysplastic syndrome). Therefore, AML treatment remains a challenge; even after intensive chemotherapy and allogeneic stem cell transplantation (alloHSCT), AML relapses are regularly observed. Thus, new concepts of AML therapy, considering tailored treatment approaches after comprehensive molecular diagnostic or implementing new immunotherapeutic strategies, are urgently needed. This review provides a detailed overview of recent developments and current promising concepts to improve the treatment and the outcome of AML patients. Abstract Treatment of acute myeloid leukemia (AML) has improved in recent years and several new therapeutic options have been approved. Most of them include mutation-specific approaches (e.g., gilteritinib for AML patients with activating FLT3 mutations), or are restricted to such defined AML subgroups, such as AML-MRC (AML with myeloid-related changes) or therapy-related AML (CPX-351). With this review, we aim to present a comprehensive overview of current AML therapy according to the evolved spectrum of recently approved treatment strategies. We address several aspects of combined epigenetic therapy with the BCL-2 inhibitor venetoclax and provide insight into mechanisms of resistance towards venetoclax-based regimens, and how primary or secondary resistance might be circumvented. Furthermore, a detailed overview on the current status of AML immunotherapy, describing promising concepts, is provided. This review focuses on clinically important aspects of current and future concepts of AML treatment, but will also present the molecular background of distinct targeted therapies, to understand the development and challenges of clinical trials ongoing in AML patients.

FMS-like tyrosine kinase 3 (FLT3) is among the most common driver genes recurrently mutated in acute myeloid leukemia (AML), accounting for approximately 30% of cases. Activating mutations of the FLT3 receptor include internal tandem duplications (ITD) that map to the auto-inhibitory juxtamembrane (JM) domain or point mutations within the tyrosine kinase domain (TKD). Several FLT3 tyrosine kinase inhibitors have been developed in the last few years, but midostaurin is currently the only one approved for the treatment of newly diagnosed patients harboring FLT3 mutations. Here we describe for the first time a novel in-frame deletion in exon 14 (JM domain) of the FLT3 gene, that we identified in a young woman with CBFb-MYH11-positive AML. We demonstrated that this novel FLT3 variant is pathogenic, since it is responsible for constitutive activation of FLT3 receptor. Finally, ex-vivo studies demonstrated that this novel mutation is sensitive to midostaurin.

Background Core binding factor acute myeloid leukemia (CBF-AML) belongs to favorable risk group in AML. However, approximately 50% of patients with CBF-AML remain incurable and their outcomes are also determined by the various co-occurring mutations. Though, FMS-like tyrosine kinase-3(FLT3) mutation in AML is associated with poor survival, the prevalence and prognostic significance of FLT3 mutations among CBF-AML is unknown. Patients and methods We performed a systematic review and meta-analysis to assess the prevalence of FLT3 mutations (ITD and TKD) among patients with CBF-AML. The pooled prevalence of FLT3 mutations was estimated for patients with CBF-AML, t(8;21) and Inv(16). Pooled odds ratio was calculated to compare the prevalence of various FLT3 mutations within the 2 subsets of CBF-AML. A random effects model was adopted for analysis when heterogenicity existed (Pheterogenicity 50%). Otherwise, a fixed effects model was used. Results The pooled prevalence of any FLT3 mutations among patients with CBF-AML was available from 18 studies and was 13% (95% CI: 10%-16%; I2 = 79%). Comparison of prevalence of FLT3 mutations between the 2 subgroups of CBF-AML showed that patients with t(8;21) had a higher prevalence of FLT3-ITD [pooled odds ratio(OR): 2.23 (95% CI:1.41-3.53, P Conclusion The prevalence of FLT3-TKD mutation was commoner among Inv(16) AML while FLT3-ITD mutation was commoner among t(8;21) AML. Uniform reporting of outcomes is essential to understand the prognostic significance of FLT3 mutations among CBF-AML.

Background and Methods: FLT3-internal tandem duplication (FLT3-ITD) is a type of mutation present in approximately 20-30% of patients with acute myeloid leukemia (AML) and is associated with poor prognosis. We performed a comprehensive genome profiling assay in patients with relapsed and refractory (R/R) AML, using the Foundation One Heme (F1H) panel, as a part of hematologic malignancies (HM)-SCREEN-Japan 01 (UMIN000035233), an actionable mutation profiling multicenter study. In this study, we analyzed the high frequency of FLT3 mutations in patients with R/R AML and found several patients who were positive for FLT3-N676K, a subclonal gene without concurrent ITD. Moreover, clonal evolution was observed in most patients who received kinase inhibitors, suggesting that mutations in signaling pathways downstream of FLT3 and activation of alternative pathways contribute to resistance mechanisms after FLT3 inhibitor treatment. Upon treatment failure during gilteritinib or quizartinib monotherapy, we can switch to another FLT3 inhibitor treatment in Japan. However, few reports have investigated clonal evolution after multiple FLT3 inhibitor treatment failure, and the mutational resistance profile remains unknown. Thus, we extended our investigation to examine clonal evolution during the progression of leukemia harboring FLT3-ITD and tyrosine kinase domain mutation (TKD) mutations. In this study, we performed serial comprehensive genome profiling analyses to evaluate time-dependent changes in genomic profiles of patients receiving the FLT3 inhibitors gilteritinib, and quizartinib in AML. Results: This study was initiated in January 2019, and 91 patients were recruited by March 2020. The median turnaround time between sending specimens and receiving results was 15 days (9 to 56 days). In this study, a higher incidence of FLT3 mutations was observed in patients with AML (28.6%, 26/91), and those with relapse/refractory (R/R) AML (64.8%, 59/91), FLT3-ITD (20.3%, 12/59), and FLT3-TKD (15.3%, 9/59), than previously reported in newly diagnosed patients. Particularly, FLT3 mutations were much more frequently observed in patients with R/R AML (35.6 %, 21/59), whereas those with newly diagnosed AML unfit for standard treatment (15.6 %, 5/32). Furthermore, FLT3-TKD mutations were found in 10 patients, who were potential candidates for treatment with FLT3 inhibitors, such as gilteritinib. The N676K mutation within the FLT3 tyrosine kinase domain 1, which is not detectable through conventional mutational analyses, was observed using a multiplex polymerase chain reaction in 19.2% (5 of 26) of patients who were FLT3mutation-positive, including those with subclonal mutations. Moreover, patients with RUNX1 mutation were present in this cohort, and this finding supports previous reports showing the association between the core binding factor protein complex and FLT3 N676K mutation in leukemia. Interestingly, FLT3-ITD mutations usually occur in the juxtamembrane domain, but we found three patients with other abnormalities, including ITDs in the tyrosine kinase domain, which are associated with poor prognosis. Meanwhile, during FLT3 inhibitor treatment, the resistant clonal expansion was observed due to activation of alternative pathways such as NRAS pathway or acquired FLT3 mutation. Not only activating these alternative pathways, but the cases in which TKD point mutation was added to FLT3-ITD, or new mutations were acquired without the additional mutation site among the cases showing FLT3 inhibitor resistance as the treatment progressed. Conclusions: We conclude that F1H mutational analyses for R/R AML harboring FLT3-ITD/TKD mutations may reveal novel therapeutic targets that are sensitive to FLT3 inhibitors. Moreover, improved biomarker analysis methods for detecting additional FLT3 alternations, like FLT3 N676K, could guide patient selection for the most suitable anti-FLT3 therapies. Furthermore, serial comprehensive genome profiling analysis at the time of AML progression, especially after tyrosine kinase inhibitor treatment, will provide valuable information for clinical decision-making. Table Disclosures Shibayama: Fujimoto: Honoraria; Pfizer: Honoraria; Bristol-Myers Squibb: Honoraria; Otsuka: Honoraria; Kyowa Kirin: Honoraria; Chugai: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Daiichi Sankyo: Honoraria; Nippon Shinyaku: Honoraria, Research Funding; Sumitomo Dainippon: Honoraria, Research Funding; Merck Sharp & Dohme: Research Funding; Takeda: Honoraria, Research Funding; Ono: Honoraria, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Eisai: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Taiho: Research Funding; Shionogi: Research Funding; Teijin: Research Funding; Astellas: Research Funding; Sanofi: Honoraria; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundi Pharma: Honoraria. Yamauchi:Otsuka: Research Funding; Ono Pharmaceutical: Honoraria; Chugai: Honoraria; Abbie: Research Funding; Solasia Pharma: Research Funding; Astellas: Research Funding; Daiichi Sankyo: Research Funding; Pfizer: Honoraria, Research Funding. Gotoh:Eisai: Honoraria; Alexion pharmaceuticals: Research Funding; Ono Pharmaceutical: Honoraria; Nippon Shinyaku: Honoraria; Takeda pharmaceutical: Honoraria; Taiho pharmaceutical: Honoraria; Chugai: Honoraria; Novartis: Research Funding. Yamamoto:Chugai: Consultancy, Honoraria, Research Funding; Eisai: Consultancy, Honoraria, Research Funding; Sanofi: Honoraria; Sumitomo Dainippon: Honoraria; Stemline Therapeutics: Consultancy; Otsuka: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria; IQIVA/HUYA: Honoraria; HUYA: Consultancy; IQIVA/Incyte: Research Funding; Solasia Pharma: Research Funding; SymBio: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Yakult: Research Funding; Zenyaku: Research Funding; Astra-Zeneca: Consultancy, Research Funding; Bayer: Research Funding; Bristol-Myers Squibb: Honoraria; Aichi Cancer Center: Current Employment; Kyowa Kirin: Honoraria; Meiji Seika Pharma: Consultancy, Honoraria; Mochida: Honoraria; Gilead Sciences: Research Funding; Daiichi Sankyo: Consultancy; MSD: Consultancy, Honoraria, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding; Nippon Shinyaku: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Ono: Consultancy, Honoraria, Research Funding; Janssen: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Fujishima:Pfizer: Speakers Bureau. Takahashi:Novartis Pharma KK: Honoraria, Research Funding; Pfizer Japan Inc.: Honoraria, Research Funding; Bristol-Myers Squibb Company: Honoraria. Usuki:Apellis: Research Funding; Alexion: Research Funding, Speakers Bureau; Novartis: Research Funding, Speakers Bureau; Chugai: Research Funding. ONO:Astellas Pharma Inc.: Honoraria; TAIHO PHARMACEUTICAL CO., LTD.: Research Funding; Mundipharma K.K.: Honoraria; Otsuka Pharmaceutical Co., Ltd.: Honoraria; Novartis Pharma KK: Honoraria; Celgene: Honoraria, Research Funding; Bristol-Myers Squibb Company: Honoraria; Pfizer Japan Inc.: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria, Research Funding; ONO PHARMACEUTICAL CO., LTD.: Honoraria, Research Funding; Takeda Pharmaceutical Company Limited.: Honoraria; Kyowa Kirin Co., Ltd.: Honoraria, Research Funding; DAIICHI SANKYO COMPANY, LIMITED.: Honoraria; Janssen Pharmaceutical K.K: Honoraria; Eisai Co., Ltd.: Honoraria. Kuroda:Sysmex: Research Funding; Otsuka Pharmaceutical: Honoraria, Research Funding; Astellas Pharma: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; Ono Pharmaceutical: Honoraria, Research Funding; Nippon Shinyaku: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Asahi Kasei: Research Funding; Shionogi: Research Funding; Dainippon Sumitomo Pharma: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Kyowa Kirin: Honoraria, Research Funding; Janssen Pharmaceutical K.K: Consultancy; Eisai: Honoraria, Research Funding; Fujimoto Pharmaceutical: Honoraria, Research Funding; Taiho Pharmaceutical: Research Funding; Bristol-MyersSquibb: Consultancy, Honoraria, Research Funding; Chugai Pharmaceutical: Honoraria, Research Funding; MSD: Research Funding. Izutsu:Incyte: Research Funding; Eisai: Research Funding; AstraZeneca: Research Funding; Abbvie pharmaceuticals: Research Funding; Chugai: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Symbio: Research Funding; Solasia: Research Funding; Janssen: Research Funding; Yakult: Research Funding; HUYA Japan: Research Funding; Sanofi: Research Funding; Daiichi Sankyo: Research Funding; Bayer pharmaceuticals: Research Funding; Ono Pharmaceutical: Research Funding. Minami:Novartis Pharma KK: Honoraria; Pfizer Japan Inc.: Honoraria; Takeda: Honoraria; Bristol-Myers Squibb Company: Honoraria.

Introduction The FMS-like tyrosine kinase 3 (FLT3) gene is mutated in ~20% of patients (pts) with AML ≥70 years (Schneider et al, 2012). Both FLT3-ITD and FLT3-TKD mutations (mut) are associated with AML proliferation and potentially targetable with small molecule inhibitors. The presence of a FLT3mut, particularly FLT3-ITD, often correlates with high leukemic burden and risk of relapse despite high response rates (Gale et. al, 2008). There is limited evidence of the effect of currently available therapies on treatment-naïve AML pts unfit for intensive treatment with FLT3mut. We evaluated the efficacy and safety of venetoclax (Ven) and Azacitidine (Aza) combination among treatment-naïve AML pts with co-morbidities and/or age ≥ 75 years, unfit for intensive treatment, and with FLT3mut. Methods Data were pooled from pts enrolled in a phase 3 study (NCT02993523, data cut-off: 04Jan2020) that compared pts treated with Ven+Aza or placebo (Pbo)+Aza, and a prior phase 1b study (NCT02203773, data cut-off: 19Jun2019) where pts were treated with Ven+Aza. Pts on Ven+Aza received Ven 400 mg daily orally (days 1-28) and Aza (75 mg/m2; days 1-7/28-day cycle). Disease assessments were performed per the modified International Working Group response criteria for AML. DNA was isolated from bone marrow aspirates collected from pts prior to the first dose of study drug and analyzed centrally. Pts with positive test results for FLT3; [Leukostrate FLT3 CDx for phase 3 study or MyAML panel (Invivoscribe) for Phase 1b study] were counted as mutation "detected"; pts with a negative test result were counted as mutation "not detected." Pts without a result either due to an inconclusive test or missing specimen were not included in the analyses. Results In this pooled analysis, FLT3mut was detected in 40 pts treated with Ven+Aza and 22 pts treated with Pbo+Aza. At baseline (Ven+Aza/Pbo+Aza), the median age was 75 (range: 49-91)/75 (65-85) years. Cytogenetic risks were: intermediate: 88%/96% and poor: 13%/5%, Eastern Co-operative Oncology Group performance scores were: 0-1: 40%/50% and 2-3: 60%/50%. 78%/86% had de novo AML, while 23%/14% had secondary AML. FLT3-ITD was detected in 28/13 and FLT3-TKD in 13/10 pts, respectively. FLT3-ITD allelic ratios were: Complete response (CR)+CR with partial hematologic recovery (CRh) rates in FLT3mut pts (Ven+Aza/Pbo+Aza) were 65% (95% CI:48%-79%)/18% (5%-40%) (Table) with a median duration of response (mDoR) 18.3 [95% CI: 10.1- not reached (NR)]/15.1 (13.9-NR) mos. Median time to first CR/CRh response was 1.0/3.2 months (mos). 43%/0% achieved CR+CRh by initiation of cycle (C) 2. Median overall survival (mOS) was 13.3 (95% CI: 8.4-23.5)/8.6 (5.9-14.7) mos, respectively. Among pts with FLT3-ITD, CR+CRh rates (Ven+Aza/Pbo+Aza) were 61% (95% CI: 41%-79%)/23% (5%-54%) with mDoR 17.4 (95% CI: 3.7-NR)/14.5 (13.9-15.1) mos. The median time to first CR/CRh response was 1.0/3.5 mos and 39%/0% pts achieved CR+CRh by initiation of C2. The mOS was 11.5 (95% CI: 6.4-23.5)/8.5 (6.1-20.3) mos, respectively. CR+CRh rates in pts with FLT3-TKD were 69% (95% CI: 39%-91%)/20% (3%-56%) with mDoR 18.3 (95% CI: 3.0-NR)/NR (15.1-NR) mos. The median time to first CR/CRh response was 1.0/2.7 mos and 46%/0% achieved a response by initiation of C2. The mOS was 19.2 (95% CI:1.8-NR/10.0 (0.2-14.7) mos, respectively. In pts treated with Ven+Aza, CR+CRh rates among pts with FLT3 detected/FLT3 not detected were 65% (95% CI: 48%-79%)/63% (56%-69%) with mDoR 18.3 (95% CI: 10.1-NE)/18.1 (15.3-NR) mos. The mOS was 13.3 (95%CI: 8.4-23.5)/14.1 (10.6-18.7) mos, respectively (Figure). Among pts treated with Ven+Aza, grade 3/4 hematologic adverse events (AEs) in pts with FLT3 detected/FLT3 not detected was 67%/77%, and included anemia (33%/25%), neutropenia (36%/33%), thrombocytopenia (39%/36%), and febrile neutropenia (36%/43%). Grade 3/4 hematologic AEs among pts with FLT3-ITD/FLT3-TKD treated with Ven+Aza was 67%/69%. Conclusion Ven+Aza compared to Aza monotherapy resulted in significantly higher CR+CRh rates among treatment-naïve pts with FLT3mut ineligible for intensive chemotherapy. In this unselected AML population, insufficient pt numbers in various subgroups limit the ability to draw conclusions regarding DoR and mOS for FLT3-ITD and TKD subgroups. There were no unexpected toxicities in the Ven+Aza arm. Future studies with larger sample sizes are warranted. Disclosures Konopleva: Ascentage: Research Funding; Amgen: Consultancy; Genentech: Consultancy, Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Forty-Seven: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Kisoji: Consultancy; Agios: Research Funding; Calithera: Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; AstraZeneca: Research Funding; AbbVie: Consultancy, Research Funding; Sanofi: Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Ablynx: Research Funding. Thirman:AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Syndax: Research Funding; TG Therapeutics: Research Funding; Tolero: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Gilead Sciences: Research Funding. Pratz:Millennium: Research Funding; Celgene: Other: Scientific Advisory Board; AbbVie: Other: Scientific Advisory Board, Research Funding; Astellas: Other: Scientific Advisory Board, Research Funding; Boston BioMedical: Consultancy; Agios: Other: Scientific Advisory Board, Research Funding; Daiichi Sankyo: Research Funding; Jazz Pharmaceutical: Consultancy. Letai:Flash Therapeutics: Membership on an entity's Board of Directors or advisory committees; Dialectic: Membership on an entity's Board of Directors or advisory committees; Chugai: Other: Lecture Fees; Novartis: Research Funding; AbbVie: Consultancy; Zentalis: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy. Pullarkat:AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dova: Consultancy, Honoraria; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kantarjian:Immunogen: Research Funding; Janssen: Honoraria; Sanofi: Research Funding; BioAscend: Honoraria; Abbvie: Honoraria, Research Funding; Oxford Biomedical: Honoraria; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Aptitute Health: Honoraria; BMS: Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; Delta Fly: Honoraria; Pfizer: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Ascentage: Research Funding; Adaptive biotechnologies: Honoraria; Novartis: Honoraria, Research Funding; Jazz: Research Funding. Dail:Genentech: Current Employment, Current equity holder in publicly-traded company. Duan:AbbVie: Current Employment, Other: may hold stock or options. Chyla:AbbVie: Current Employment, Current equity holder in publicly-traded company. Potluri:AbbVie: Current Employment, Other: may hold stock or stock options. Miller:AbbVie: Current Employment, Current equity holder in publicly-traded company. Dinardo:Takeda: Honoraria; Daiichi Sankyo: Consultancy, Research Funding; Novartis: Consultancy; Notable Labs: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Research Funding; Celgene: Research Funding; Agios: Consultancy, Research Funding; Calithera: Research Funding; ImmuneOnc: Honoraria. Wei:AbbVie: Honoraria, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Honoraria, Research Funding; Pfizer: Honoraria; BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Honoraria; Amgen: Honoraria, Research Funding; Walter and Eliza Hall Institute of Medical Research: Patents & Royalties; Genetech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Introduction: Mutations in the gene encoding for the FMS-like tyrosine kinase 3 (FLT3) are present in about 30% of adults with AML and are associated with shorter disease-free and overall s...

Introduction: FLT3 mutations are identified in 20–30% of acute myeloid leukemia (AML) and are associated with a poor prognosis due to chemotherapy refractory disease and short relapse-free survival...

Objectives To assess real‐world treatment patterns and healthcare resource utilization (HRU) among patients with FLT3–mutated (FLT3 mut) and FLT3–wild‐type (FLT3 wt) acute myeloid leukemia (AML). Methods Data were abstracted from medical charts of patients with AML from 10 countries. Patients were grouped based on their FLT3 mutation status, age (18‐64 or ≥65), and whether they were newly diagnosed (ND) or relapsed/refractory (R/R). Results Charts of 1027 AML patients were included (183 FLT3 mut 18‐64 ND; 136 FLT3 mut ≥65 ND; 181 FLT3 mut R/R; 186 FLT3 wt 18‐64 ND; 159 FLT3 wt ≥65 ND; 182 FLT3 wt R/R). Substantial heterogeneity was observed in treatment patterns for AML. Among ND patients 18‐64, the most common initial treatment was standard‐to‐intermediate dose cytarabine‐based therapies (43.2% for FLT3 mut and 55.9% for FLT3 wt); among ND patients ≥65, the most common initial treatment was hypomethylating agent‐based therapies (36.0% and 47.2%). Among R/R patients, the most common initial treatment after R/R was best supportive care only (39.8% and 24.7%). HRU was substantial across cohorts during both event‐free and post‐event periods. Conclusions Treatment patterns of AML were heterogeneous and FLT3 mut AML was treated more aggressively than FLT3 wt disease. HRU was substantial for all cohorts, particularly after relapse or treatment failure.

Acute myeloid leukaemia (AML) is a haematopoietic malignancy with a dismal outcome. Consequently, risk stratification based on more effective prognostic biomarkers is crucial to make accurate therapy decisions. T cell receptor gamma alternative reading frame protein (TARP) has been reported in prostate and breast cancers, but its correlation with AML remains unclear.Differential expression of TARP mRNA in different AML subtypes was analysed using the UALCAN online platform. Its relationship with baseline clinical attributes, survival and efficacy were analysed based on three GSE1159, GSE425 and GSE6891 microarray datasets downloaded from Gene Expression Omnibus (GEO) and Oncomine databases. Quantitative real-time PCR was performed to determine mRNA levels of TARP in bone marrow mononuclear cells (BMMCs) isolated from AML patients.TARP was significantly overexpressed in AML patients. In AML, relatively low TARP expression was associated with theOur findings suggest that TARP might be a potential prognostic marker of AML and serve as a promising immunotherapeutic target.

FLT3 mutations are the most frequently identified genetic alterations in acute myeloid leukemia (AML) and are associated with poor clinical outcome, relapse and chemotherapeutic resistance. Elucidating the molecular mechanisms underlying FLT3-dependent pathogenesis and drug resistance is a crucial goal of biomedical research. Given the complexity and intricacy of protein signaling networks, deciphering the molecular basis of FLT3-driven drug resistance requires a systems approach. Here we discuss how the recent advances in mass spectrometry (MS)-based (phospho) proteomics and multiparametric analysis accompanied by emerging computational approaches offer a platform to obtain and systematically analyze cell-specific signaling networks and to identify new potential therapeutic targets.

The prognostics implications of patients with acute myeloid leukemia harboring non-canonical FLT3 is unknown. The use of tyrosine kinase inhibitors in this patient population has not been previously reported. We report successful targeted therapy against non-ITD, non-D835 driver FLT3 alterations in two patient case studies with acute myeloid leukemia.

Fms-like tyrosine kinase-3 (FLT3) mutations occur in approximately 30% of acute myeloid leukemia (AML) cases, suggesting FLT3 as an attractive target for AML treatment. Early FLT3 inhibitors enhance antileukemia efficacy by inhibiting multiple targets, and thus had stronger off-target activity, increasing their toxicity. Recently, a number of potent and selective FLT3 inhibitors have been developed, many of which are effective against multiple mutations. This review outlines the evolution of AML-targeting FLT3 inhibitors by focusing on their chemotypes, selectivity and activity over FLT3 wild-type and FLT3 mutations as well as new techniques related to FLT3. Compounds that currently enter the late clinical stage or have entered the market are also briefly reported.

Background Early data suggest that patients undergoing salvage chemotherapy for relapsed or refractory (R/R) acute myeloid leukaemia (AML) have poor outcomes if infected with SARS-CoV-2, and nosocomial transmission has been a major problem worldwide. Gilteritinib is effective in R/R FLT3 mutated AML, is significantly less immunosuppressive and does not require hospital admission, however at the start of the pandemic this was not yet approved for routine use in all countries. In the United Kingdom, the National Health Service (NHS) made gilteritinib available as an emergency measure from late April 2020 to patients aged >16y with R/R FLT3 mutated AML, with the aim of reducing both mortality and healthcare resource use. We report a health-system-wide real world data collection for toxicity and patient outcomes across 27 NHS Hospitals. Methods Each patient was registered on a central NHS database, with clinicians certifying that their patient met the above criteria. Anonymised data were retrospectively collected by treating physicians. Gilteritinib dose, duration and toxicity information was requested for the first 4 cycles of therapy. Response definitions were as per European Leukaemia Network (ELN) guidelines. A total of 81 patients have been registered on the scheme, with outcomes reported here for those with follow-up information at a data cut on 1st August 2021. Results Fifty patients were included with a median age of 59y (range 19 - 77) and 50% male. The majority (83%) had an ECOG performance status of 0-1. AML was secondary to a previous haematological disorder in 12%, therapy-related in 4% and de novo in the remaining 84%. The disease was refractory to the last therapy in 38%. Most patients had previously received 1 (65%) or 2 (33%) lines of therapy, including intensive chemotherapy in a majority (86%). A FLT3 inhibitor had previously been administered to 45% and 35% were post allogeneic transplant. The FLT3 mutation was an internal tandem duplication (ITD) in 80% and tyrosine kinase domain (TKD) mutation in 22%. NPM1 mutations were detected in 34%. Next-generation sequencing results were available for 94% of patients, with mutations in IDH1 or IDH2 in 12.5%, ASXL1 in 2%, RUNX1 in 21% and no TP53 mutations. Patients spent a median 3.5 days in hospital in cycle 1, 0 days in cycles 2 and 3 and 1 day in cycle 4. In cycles 1, 2, 3 and 4, the median number of days of grade 4 neutropenia was 18, 7, 7.5, and 6.5 respectively, and the grade 4 thrombocytopenia was 2, 7, 0.5 and 0.5. The composite complete remission (CR) / CR with incomplete haematological recovery (CRi) rate was 27%. MRD data is being collected. The best response was morphological leukaemia free state (MLFS) in 4%, partial remission (PR) in 25% and refractory disease in 38%. The rate of combined CR/CRi did not differ in those with previous exposure to FLT3 inhibitors (23% vs 32%, p=0.6) or with past allogeneic transplant (29% vs 27%, p=0.3). There were no CR/CRi in patients with adverse cytogenetic risk. Median follow-up was 10.5 months (95%CI 7.3 - 12.3) with median overall survival (OS) 6.7 months (95%CI 4.5 - not reached). Mortality at day 30 was 0% and day 60 was 14%. 12-month overall survival was 38%. Patients who achieved a CR/CRi had a 12-month OS of 83%, and for PR this was 35%. Survival did not differ in those with previous FLT3 inhibitor exposure (HR 1.0, p>0.9) or allogeneic transplant (HR 0.63, p=0.3). Seven patients (14%) so far have been bridged with gilteritinib to allogeneic transplant. Conclusion Our data demonstrate that gilteritinib is well tolerated and clinically active in adults with relapsed FLT3 mutated AML. Importantly, during the COVID-19 pandemic, its availability has permitted the great majority of treatment to be delivered as an outpatient with significant resource saving at a time of critically constrained inpatient resources. Patients who achieve CR/CRi have good short-term outcomes and are able to proceed to a potentially curative allogeneic stem cell transplant. Figure 1 Figure 1. Disclosures Belsham: Celgene: Other: meeting attendance; Abbvie: Other: meeting attendance. Byrne: Incyte: Honoraria. Khan: Abbvie: Honoraria; Astellas: Honoraria; Takeda: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Novartis: Honoraria. Khwaja: Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Latif: Kite: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Speakers Bureau; Takeda UK: Speakers Bureau. Loke: Amgen: Honoraria; Daichi Sankyo: Other: Travel Support; Janssen: Honoraria; Novartis: Other: Travel Support; Pfizer: Honoraria. Munisamy: Jazz Pharmaceuticals: Speakers Bureau; Roche: Speakers Bureau. Murthy: Abbvie: Other: support to attend educational conferences.. Smith: Daiichi Sankyo: Speakers Bureau; Pfizer: Speakers Bureau; ARIAD: Honoraria. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dillon: Amgen: Other: Research support (paid to institution); Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Jazz: Other: Education events; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events.

Gilteritinib (Gilt), a FLT3 tyrosine kinase inhibitor (TKI), is approved for the treatment of relapsed/refractory (R/R) FLT3-mutated (FLT3 +)acute myeloid leukemia (AML). However, long-term survival is limited by the development of drug resistance mutations in persistent FLT3 + clones. Combination regimens may deepen response and improve outcomes. Venetoclax (Ven), a BCL-2 inhibitor, is approved in combination with hypomethylating agents for newly diagnosed AML not suitable for standard induction therapy. FLT3 + AMLhas been associated with clinical resistance to Ven. Still, FLT3 TKIs + Ven have demonstrated synthetic lethality in preclinical models, prompting this multicenter, open-label, phase 1b trial (NCT03625505) to evaluate Ven + Gilt for R/R AML. Here, we report final response and survival endpoints, and molecular clearance among patients (pts) treated at the recommended phase two dose (RP2D). The study design has been previously described (Daver, et al. ASH 2020, Abstract 333). Pts in the dose expansion cohort received Ven 400 mg + Gilt 120 mg (RP2D) daily in 28-day cycles, following Ven ramp-up. The primary endpoint was mCRc (complete response [CR] + CR with incomplete platelet recovery [CRp] + CR with incomplete blood count recovery [CRi] + morphologic leukemia-free state) to align with the ADMIRAL phase III trial (Perl, et al. NEJM 2019). Baseline co-mutations and serial FLT3 internal tandem duplications (ITD) allelic burden were assessed using the MyAML panel (Invivoscribe, San Diego, CA) and FLT3-ITD MRD assay with sensitivities of 5% and 0.001%, respectively. As of the data cut off of January 31, 2021, 54 pts were treated at the RP2D. Fifty-two pts (as assessed locally) had FLT3 +AML; 41 had FLT3-ITD only, 8 had tyrosine kinase domain only, 3 had both mutations, and 2 were FLT3 wild type (wt). Additional baseline characteristics are in Table 1. Grade 3 or 4 AEs occurred in 51 (94.4%) pts, and 39 (72.2%) pts had serious AEs. Grade 3 or 4 cytopenias occurred in 43 (79.6%) pts. AEs of special interest included tumor lysis syndrome (2 [3.7%]) and QT prolongation (1 [1.9%]). AEs leading to dosing interruptions (Ven, 27 [50%]; Gilt, 26 [48.1%]), reductions (Ven, 3 [5.6%]; Gilt, 4 [7.4%]), and discontinuation (Ven, 7 [13%]; Gilt, 7 [13%]) were reported for both study drugs. There was 1 treatment-emergent death of typhlitis. Among FLT3 + pts with post-baseline assessments (51/52), mCRc was achieved by 38 pts (74.5%; CR/CRp/CRi, 19 [37.3%] pts), with a median follow-up time of 12 mo (range: 0.8 - 20.1). The mCRc in pts with prior TKI (32) or prior Ven (10) use were 78.1% and 60%, respectively. The mOS among all FLT3 +pts was 10 mo (95%CI: 6.6, NE), with a median DoR (mDoR) of 5.4 mo (95% CI: 3.3, 6.6). Pts with FLT3-ITD had a mOS of 10.5 mo (95%CI: 6.8, NE), and a mDoR of 5.6 mo (95% CI: 3.3, 8.3). For the 14 pts who had a transplant, the mOS was not reached (95%CI: 10.0, NE) vs 6.89 mo (95%CI: 3.0, 10.5) for those who did not have a transplant (37). The mOS for pts with prior TKI or Ven was 9.6 (95% CI: 4.3, NE) and 10.5 mo (95% CI: 2.0, NE), respectively, with a mDoR of 9.6 (95% CI: 4.3, NE) and 6.2 mo (95% CI: 2.6, NE), respectively. The 60-day mortality rate was 11.8% (95% CI: 4.4, 23.9). The mCRc for NPM1 + and NPM1wt were 92.3% and 61.1%, respectively. mCRc for DNMT3A + and DMNT3A wt pts were 82.4% and 64.3%, respectively. WT1 + and WT1 wt mCRc were 66.7% and 77.3%, respectively. The mCRc for NPM1 + and DNMT3A + co-mutated pts was 100%. In a post hoc analysis of the 30 analyzable mCRc pts with at least one follow-up MRD assessment, 17 (56.7%) achieved molecular clearance defined as FLT3 allelic burden < 10 -2. The mOS of pts achieving mCRc with FLT3 allelic burden of < 10 -2 vs mCRc with FLT3 allelic burden ≥ 10 -2 (Figure 1) was not reached (95% CI: 9.76, NE) vs 6.83 mo (4.21, NE). Ven + Gilt achieved high mCRc in patients with R/R FLT3 + AML, with or without prior TKI exposure, and an encouraging mOS. FLT3 mutation clearance was seen in a majority of patients and associated with longer OS. Encouraging remission rates were observed across many genotypes and were particularly high among pts with NPM1 + +/- DNMT3A co-mutation. Cytopenias were common but manageable with appropriate Ven or Gilt dosing modifications. Serial NGS molecular data, as well as updated survival data will be presented at the meeting. Figure 1 Figure 1. Disclosures Daver: Hanmi: Research Funding; Abbvie: Consultancy, Research Funding; Trillium: Consultancy, Research Funding; Trovagene: Consultancy, Research Funding; Novimmune: Research Funding; FATE Therapeutics: Research Funding; Glycomimetics: Research Funding; Amgen: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Sevier: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; ImmunoGen: Consultancy, Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy, Other: Data Monitoring Committee member; Dava Oncology (Arog): Consultancy; Celgene: Consultancy; Syndax: Consultancy; Shattuck Labs: Consultancy; Agios: Consultancy; Kite Pharmaceuticals: Consultancy; SOBI: Consultancy; STAR Therapeutics: Consultancy; Karyopharm: Research Funding; Newave: Research Funding. Perl: Actinium: Consultancy; Genentech: Consultancy; Roche: Consultancy; Astellas: Consultancy, Research Funding; Forma: Consultancy; Syndax: Consultancy; Loxo: Consultancy; Fujifilm: Research Funding; Arog: Research Funding; BMS/Celgene: Consultancy; AbbVie: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Levis: Amgen, Astellas Pharma, Daiichi-Sankyo, FujiFilm, and Menarini: Honoraria; Astellas and FujiFilm: Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Jazz: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Ritchie: Astellas: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria; Celgene/BMS: Consultancy, Other: travel support, Speakers Bureau; Bristol Myers Squibb: Consultancy, Research Funding; NS Pharma: Research Funding; Incyte: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria; Jazz: Consultancy, Research Funding; Protaganist: Consultancy, Honoraria; ARIAD Pharmaceuticals: Ended employment in the past 24 months, Speakers Bureau; Pfizer: Consultancy, Research Funding. Litzow: Astellas: Research Funding; Omeros: Other: Advisory Board; Pluristem: Research Funding; AbbVie: Research Funding; Amgen: Research Funding; Actinium: Research Funding; Jazz: Other: Advisory Board; Biosight: Other: Data monitoring committee. McCloskey: Jazz: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Smith: AbbVie: Research Funding; Revolutions Medicine: Research Funding; Daiichi Sankyo: Consultancy; FUJIFILM: Research Funding; Astellas Pharma: Consultancy, Research Funding; Amgen: Honoraria. Schiller: Takeda: Research Funding; Trovagene: Research Funding; Tolero: Research Funding; Ono: Consultancy; Novartis: Consultancy, Research Funding; ASH foundation: Other: Chair-unpaid; Pfizer: Current equity holder in publicly-traded company, Research Funding; Incyte: Consultancy; Sanofi: Honoraria, Research Funding, Speakers Bureau; Ariad: Research Funding; Stemline Therapeutics, Inc.: Honoraria, Research Funding, Speakers Bureau; Ono-UK: Consultancy, Research Funding; Karyopharm: Research Funding; Kite/Gilead: Honoraria, Research Funding, Speakers Bureau; Onconova: Research Funding; Mateon: Research Funding; Sangamo: Research Funding; Samus: Research Funding; Regimmune: Research Funding; PrECOG: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Kaiser Permanente: Consultancy; Cyclacel: Research Funding; MedImmune: Research Funding; Ambit: Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Research Funding, Speakers Bureau; Jazz: Consultancy, Honoraria, Research Funding, Speakers Bureau; Elevate: Research Funding; Bio: Research Funding; Pharma: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Biomed Valley Discoveries: Research Funding; Eli Lilly: Research Funding; Sellas: Research Funding; Geron: Research Funding; Genentech-Roche: Research Funding; Gamida Cell Ltd.: Research Funding; FujiFilm: Research Funding; Forma: Research Funding; Delta-Fly: Research Funding; Deciphera: Research Funding; Daiichi-Sankyo: Research Funding; Constellation Pharmaceuticals: Research Funding; Celator: Research Funding; BMS/Celgene: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Astellas: Honoraria, Research Funding, Speakers Bureau; Arog: Research Funding; Actuate: Research Funding; Actinium Pharmaceuticals, Inc: Research Funding; Abbvie: Research Funding; Leukemia & Lymphoma Society: Research Funding; Bluebird Bio: Research Funding; Boehringer-Ingleheim: Research Funding; Cellerant: Research Funding; CTI Biopharma: Research Funding; Janssen: Research Funding; Kura Oncology: Research Funding; Pharmacyclics: Honoraria, Speakers Bureau; Millennium: Research Funding; National Marrow Donor Program: Research Funding; NIH: Research Funding; Onyx: Research Funding; Pharmamar: Research Funding; UC Davis: Research Funding; UCSD: Research Funding; Evidera: Consultancy; NCI: Consultancy; Novartis: Speakers Bureau. Bradley: AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Tiu: Astellas Pharma: Current Employment; Eli Lilly and Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Naqvi: Genentech/Roche: Current Employment, Current holder of stock options in a privately-held company. Dail: Genentech/Roche: Current Employment, Current equity holder in publicly-traded company. Siddani: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Wang: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Chyla: AbbVie: Current Employment, Current equity holder in publicly-traded company. Lee: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Altman: Astellas: Consultancy, Other: Advisory Board, Research Funding; AbbVie: Consultancy, Other: Advisory Board, Research Funding; Biosight: Consultancy, Other: Travel fees, Research Funding; Daiichi Sankyo: Consultancy; Kura Oncology: Consultancy; Syros: Consultancy; Theradex: Consultancy, Other: Advisory boards; GlycoMimetics: Other: Participation on an advisory board; ALZ Oncology: Research Funding; Amgen: Research Funding; Aprea: Research Funding; BMS: Research Funding; Boehringer Ingelheim: Research Funding; Fujifilm: Research Funding; Immunogen: Research Funding; Kartos: Research Funding; Kura: Research Funding. OffLabel Disclosure: Venetoclax is a B-cell lymphoma 2 inhibitor approved in combination with azacitidine, or decitabine, or low-dose cytarabine for the treatment of newly-diagnosed acute myeloid leukemia (AML) in adults who are age 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy. Gilteritinib is a kinase inhibitor indicated for the treatment of adult patients who have relapsed or refractory acute myeloid leukemia (AML) with an FLT3 mutation as detected by an FDA-approved test.

Background: The presence of measurable residual disease (MRD) after achievement of remission with induction therapy is a prognostic marker of relapse risk in patients with acute myeloid leukemia (AML). Gilteritinib is an oral FLT3 inhibitor approved as a single agent for the treatment of patients with FLT3-mutated (FLT3mut+) relapsed or refractory AML. Evaluation of gilteritinib in the front-line setting is under way. We evaluated FLT3 internal tandem duplication (FLT3-ITD) mutation clearance using two different thresholds and correlated mutation clearance with survival outcomes in patients with newly diagnosed AML ineligible for intensive chemotherapy who were treated with front-line gilteritinib plus azacitidine (AZA) or either agent alone in the phase 2/3 LACEWING trial. Methods: Adult patients with newly diagnosed FLT3mut+ AML ineligible for intensive induction chemotherapy received 28-day cycles of once-daily gilteritinib plus AZA in the Safety Cohort (80 or 120 mg/day gilteritinib plus 75 mg/m 2 AZA, Days 1-7) and in Arm AC (120 mg/day gilteritinib plus 75 mg/m 2 AZA, Days 1-7), gilteritinib (120 mg/day) alone in Arm A, or AZA (75 mg/m 2, Days 1-7) alone in Arm C. A subset of patients who had a best overall response of composite complete remission (CRc; defined as the sum of patients who achieved complete remission with or without complete hematologic or platelet recovery) and who had bone marrow-derived DNA samples available at baseline and at least one additional post-baseline timepoint were assessed for FLT3-ITD mutation clearance using next-generation sequencing. An Illumina ® sequencing platform was used to quantify FLT3-ITD and total FLT3 alleles. The FLT3-ITD variant allelic frequency (VAF) was defined as the ratio of FLT3-ITD to total FLT3 frequency. Data were analyzed using two different mutation clearance thresholds, FLT3-ITD VAF Results: The median age of patients enrolled in LACEWING was 77 years (range, 59-90), with 73% of patients aged >75 years. Although baseline characteristics of the overall LACEWING population were generally well balanced across treatment arms, higher proportions of patients treated with gilteritinib plus AZA (47%) or gilteritinib alone (59%) had an Eastern Cooperative Oncology Group (ECOG) performance status of ≥2 compared with patients treated with AZA alone (33%). Overall, 40 patients who achieved CRc and had sufficient DNA samples from bone marrow aspirates obtained at baseline and at least one additional post-baseline timepoint were included in the analysis (Safety Cohort, n=8; Arm A, n=7; Arm AC, n=17; and Arm C, n=8). Across both thresholds, the proportions of patients with FLT3 mutation clearance did not markedly differ between patients treated with gilteritinib or AZA (Table). In patients who received gilteritinib, FLT3-ITD mutation clearance using either threshold was associated with a similar increase in median overall survival (OS) compared to patients who did not achieve mutation clearance (Figure). Conclusions: Regardless of MRD threshold, rates of MRD negativity were not substantially different between newly diagnosed FLT3mut+ AML patients ineligible for intensive induction chemotherapy who received gilteritinib alone, gilteritinib plus AZA, or AZA alone. Advanced age coupled with a worse baseline ECOG performance score at baseline may have compromised treatment response and achievement of FLT3 mutation clearance in patients treated with gilteritinib. The mutation clearance thresholds used in this analysis showed similar median OS in patients who received gilteritinib. Figure 1 Figure 1. Disclosures Wang: Pfizer: Consultancy, Honoraria, Other: Advisory Board, Speakers Bureau; Genentech: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Honoraria, Other: Advisory Board; Novartis: Consultancy, Honoraria, Other: Advisory Board; Kura Oncology: Consultancy, Honoraria, Other: Advisory board, steering committee, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Takeda: Consultancy, Honoraria, Other: Advisory board; Kite Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Stemline Therapeutics: Consultancy, Honoraria, Other: Advisory board, Speakers Bureau; Mana Therapeutics: Consultancy, Honoraria; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Speakers Bureau; Rafael Pharmaceuticals: Other: Data safety monitoring committee; Gilead: Consultancy, Honoraria, Other: Advisory board; Daiichi Sankyo: Consultancy, Honoraria, Other: Advisory board; PTC Therapeutics: Consultancy, Honoraria, Other: Advisory board; Genentech: Consultancy; MacroGenics: Consultancy. Altman: Kartos: Research Funding; Theradex: Consultancy, Other: Advisory boards; Biosight: Consultancy, Other: Travel fees, Research Funding; Daiichi Sankyo: Consultancy; AbbVie: Consultancy, Other: Advisory Board, Research Funding; BMS: Research Funding; Amgen: Research Funding; Astellas: Consultancy, Other: Advisory Board, Research Funding; Fujifilm: Research Funding; ALZ Oncology: Research Funding; Immunogen: Research Funding; GlycoMimetics: Other: Participation on an advisory board; Syros: Consultancy; Kura Oncology: Consultancy; Boehringer Ingelheim: Research Funding; Aprea: Research Funding; Kura: Research Funding. Minden: Astellas: Consultancy. Wu: Astellas: Current Employment. Rich: Astellas Pharma Global Development, Inc.: Current Employment. Hill: Ligacept, LLC: Current holder of individual stocks in a privately-held company, Other: Stockholder; Astellas Pharma Global Development: Current Employment.

Background: FLT3 tyrosine kinase inhibitors (TKIs) have improved outcomes in clinical trials for patients with FLT3 mutation-positive acute myeloid leukemia (FLT3mut+ AML). Gilteritinib is the first FDA-approved (11/28/2018) targeted therapy for relapsed/refractory (R/R) FLT3mut+ AML in adults, although two other multikinase inhibitors, midostaurin and sorafenib, are used off-label in this population. This analysis characterized treatment duration for these three drugs in R/R FLT3mut+ AML, as little is known about the treatment of patients receiving a FLT3 inhibitor in the real world. Aim/Objective: To describe real-world treatment patterns of patients newly initiating a FLT3 TKI for R/R AML following the launch of gilteritinib. Methods: This was a post hoc analysis of a US-based retrospective cohort study using IBM MarketScan claims data (1/1/2007-10/30/2020) to evaluate real-world treatment patterns. Adult patients (≥18 years) with R/R AML who newly initiated a FLT3 TKI (ie, ≥1 claim for gilteritinib, midostaurin, or sorafenib) on or after 12/1/2018 were eligible for inclusion. Included patients were required to have continuous enrollment starting 180 days prior to first AML diagnosis through first FLT3 TKI initiated for R/R AML on or after 12/1/2018 (index date). FLT3 TKI treatment duration was calculated as the difference between the first claim and the last day of supply or end of enrollment/study, whichever occurred first. Treatments that were not discontinued prior to the end of the study period (10/30/2020) were censored. Treatment duration was estimated using Kaplan-Meier analysis, and the hazard ratio for discontinuation was estimated with a Cox proportional hazards model. Additional subgroup analyses were conducted based on prior FLT3 TKI exposure for R/R AML and use of FLT3 TKI therapy alone or in combination with chemotherapy. Data from the ProMetrics specialty pharmacy database (12/6/2018-3/3/2021) were also analyzed to establish a benchmark for gilteritinib and validate the treatment duration in the MarketScan results. Results: A total of 65 patients newly initiating FLT3 TKIs for R/R AML were identified in the MarketScan database. Mean patient age was 53.4 years and mean Quan-Charlson Comorbidity index score at baseline was 5.1. Most patients initiating FLT3 TKI therapy received gilteritinib (n=44 [68%]). Patients initiating gilteritinib compared with other FLT3 TKIs had the highest prior history of high-intensity chemotherapy (n=24 [47%]) and hematopoietic stem cell transplantation (n=16 [31%]). Midostaurin was the most common prior TKI for patients who initiated sorafenib (n=6 [50%]) or gilteritinib (n=28 [55%]). The median (95% CI) treatment duration was 150 (73-260) days for gilteritinib (n=51), 60 (15-210) days for sorafenib (n=12), and 54 (28-268) days for midostaurin (n=12). Treatment duration was significantly longer for patients receiving gilteritinib compared with midostaurin (P=.0018) and sorafenib (P=.0016) in the Cox proportional hazards model (Table) and the Kaplan-Meier analysis (P=.0021) (Figure). Differences in gilteritinib duration in patients with prior TKI treatment versus no prior TKI treatment and patients who used a FLT3 TKI alone versus in combination with chemotherapy were not statistically significant (Table). The median gilteritinib treatment duration in the MarketScan data (150 days) was aligned with the median duration in the ProMetrics specialty pharmacy data (154 days), which validates the MarketScan results. Conclusions: This early look at treatment patterns suggests a median duration of therapy for gilteritinib of 150 days. Importantly, gilteritinib treatment duration does not appear to differ based on prior TKI treatment or overlapping use with chemotherapy. Small sample sizes precluded adjusted comparisons between the treatments. Gilteritinib was the most commonly used treatment. The availability of new targeted therapies such as gilteritinib is promising for patients with R/R FLT3mut+ AML and is changing the therapeutic landscape for this aggressive AML subtype. Figure 1 Figure 1. Disclosures Grinblatt: Astellas Pharma, Inc.: Consultancy; Bristol Myers Squibb: Consultancy; Astra Zeneca: Consultancy; AbbVie: Consultancy. Han: Astellas Pharma, Inc.: Current Employment. Nimke: Astellas Pharma, Inc.: Current Employment. Feng: Astellas Pharma, Inc.: Current Employment. Sullivan: Astellas Pharma, Inc.: Current Employment. Pandya: Astellas Pharma, Inc.: Current Employment.

BACKGROUND: Current guidelines for AML ascribe disease-risk partly based on NPM1 and FLT3 mutational status. NPM1 mutations (mut) occur in 25%-30% of patients (pts) with AML and are associated with favorable prognosis in the absence of co-occurring FLT3-ITD. FLT3-ITD alterations are observed in ~15-30% of AML pts and confer poor prognosis, whereas the prognostic implication of FLT3-TKD point mutations (~7% of pts) is less clear. Post-IC, absence of MRD is associated with favorable relapse-free and overall survival (RFS/OS). In the randomized, phase 3 QUAZAR AML-001 trial, Oral-AZA (CC-486) significantly prolonged OS and RFS vs placebo (PBO) in older pts with AML in first remission after IC (Wei, NEJM 2020). It is of high interest to understand the effects of Oral-AZA in pts with NPM1 and/or FLT3 mutations, and whether their outcomes are influenced by post-IC MRD status. OBJECTIVE: Evaluate survival outcomes with Oral-AZA vs PBO in pts with NPM1mut ± FLT3mut at AML diagnosis (Dx), and OS by baseline (BL) MRD status (+/-) in pts with NPM1/FLT3 mutations. METHODS: In QUAZAR AML-001, pts aged ≥55 years with AML and NCCN intermediate or poor-risk cytogenetics at Dx were randomized 1:1 to receive Oral-AZA 300 mg or PBO QD within 4 mo after attaining first CR/CRi with IC (induction ± consolidation). NPM1 and FLT3 statuses (mut or wild-type [wt]) at AML Dx (before IC) were collected from pt diagnostic case report forms. MRD analyses were conducted by MFC (≥0.1% MRD+ cutoff) in bone marrow aspirate samples collected at screening (post-IC; ie, BL). OS and RFS were estimated from the time of randomization using Kaplan-Meier methods. Multivariate (MV) Cox regression analyses of the prognostic effects on OS/RFS were performed, with NPM1 and FLT3 mutational status and cytogenetic risk at Dx; post-IC MRD status (+/-) at BL, and randomized Tx (Oral AZA vs PBO) as variables. RESULTS: Of 472 pts enrolled , 469 (99.4%) had mutational data available at Dx, and the MRD-evaluable cohort comprised 463 pts (98.1%). In all, 137 pts (29%; Oral-AZA n = 66, PBO n = 71) had NPM1mut at AML Dx, and NPM1mut was significantly correlated with MRD- status at BL (post-IC)(P = 0.0178). Among pts with NPM1mut, OS was significantly improved in pts receiving Oral-AZA vs PBO, whether pts were MRD- (median 48.6 vs 26.2 mo, respectively) or MRD+ (median 39.4 vs 10.3 mo) at BL (both P < 0.0001) (Figure). While median OS for NPM1mut pts in the Oral-AZA arm was nominally improved for MRD- pts vs. those MRD+ (48.6 vs. 39.4 mo, respectively), median OS for NPM1mut pts in the PBO arm was substantially influenced by post-IC MRD status (26.2 vs 10.3 mo for MRD- and MRD+ pts, respectively) (Figure). Similarly, median RFS for pts with NPM1mut/MRD- in the Oral-AZA and PBO arms was 24.9 vs 9.9 mo, respectively, and for pts with NPM1mut/MRD+ was 19.4 vs 4.6 mo. In all, 66 pts (14.1%) had FLT3-ITD (n = 46) and/or FLT3-TKD mut (n = 24) at AML Dx; NPM1 and FLT3-ITD status was NPM1mut + FLT3-ITD - in 107 pts, NPM1mut + FLT3-ITD + in 30 pts, and NPM1wt + FLT3-ITD + in 16 pts. In the Oral-AZA arm, median OS in pts with FLT3mut was not meaningfully different from that in pts with FLT3wt (28.2 and 24.7 mo, respectively), but FLT3mut conferred a negative prognosis in the PBO arm (median OS 9.7 mo, vs 15.2 mo for FLT3wt pts). Risk of death was reduced 46% with Oral-AZA vs PBO in pts with FLT3mut (HR 0.54 [95%CI 0.25, 1.14]). When considering MRD status, median OS in FLT3mut/MRD- pts was 28.2 vs. 15.9 mo in the Oral-AZA (n = 14) and PBO (n = 17) arms, respectively, and was 24.0 vs 8.0 mo in FLT3mut/MRD+ pts (Oral-AZA, n = 16; PBO, n = 18). In MV analyses, Oral-AZA significantly improved OS vs PBO when adjusted for other variables (P = 0.035); NPM1 status (P = 0.001), FLT3status (P = 0.035), and cytogenetic risk at Dx (P < 0.001) were each also significantly predictive of OS, as was post-IC MRD status (P < 0.001). All except FLT3 status (P = 0.737) were significantly predictive of RFS. CONCLUSIONS: Oral-AZA prolonged OS and RFS vs PBO in pts with NPM1mut, with improvements beyond the prognostic benefit conferred by MRD-, suggesting that pts with NPM1mut and MRD- can attain substantial OS benefit with Oral-AZA maintenance. An OS benefit was also observed with Oral-AZA vs PBO in pts in FLT3mut at Dx, but outcomes may be confounded by co-occurring NPM1mut, so further investigation is needed. MV analyses confirmed the independent prognostic influence of Oral-AZA, NPM1 and FLT3 mutations at Dx, cytogenetic risk at Dx, and post-IC MRD status on OS. Figure 1 Figure 1. Disclosures Döhner: Janssen: Honoraria; Helsinn: Honoraria; Gilead: Honoraria; GEMoaB: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Berlin-Chemie: Honoraria; AstraZeneca: Honoraria; Astex Pharmaceuticals: Honoraria; Astellas: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Oxford Biomedica: Honoraria; Pfizer: Research Funding; Roche: Honoraria. Wei: Astellas: Honoraria; Novartis, Celgene, AbbVie, Servier, AstraZeneca, and Amgen: Research Funding; Novartis, Janssen, Amgen, Roche, Pfizer, Abbvie, Servier, BMS, Macrogenics, Agios, Gilead: Membership on an entity's Board of Directors or advisory committees. Roboz: Glaxo SmithKline: Consultancy; Helsinn: Consultancy; AbbVie: Consultancy; Jasper Therapeutics: Consultancy; Bayer: Consultancy; Novartis: Consultancy; Actinium: Consultancy; Agios: Consultancy; Blueprint Medicines: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Jazz: Consultancy; Daiichi Sankyo: Consultancy; Astex: Consultancy; Mesoblast: Consultancy; Amgen: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Bristol Myers Squibb: Consultancy; Janssen: Consultancy; Otsuka: Consultancy; Celgene: Consultancy; Janssen: Research Funding; Pfizer: Consultancy; Roche/Genentech: Consultancy. Montesinos: Agios: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Tolero Pharmaceutical: Consultancy; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Forma Therapeutics: Consultancy; Glycomimetics: Consultancy; Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau; Stemline/Menarini: Consultancy. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Ravandi: AstraZeneca: Honoraria; AbbVie: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Xencor: Honoraria, Research Funding; Syros Pharmaceuticals: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Research Funding; Novartis: Honoraria; Astex: Honoraria, Research Funding; Prelude: Research Funding; Taiho: Honoraria, Research Funding. Dombret: Amgen: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding; Servier: Research Funding; Abbvie: Honoraria; BMS-Celgene: Honoraria; Daiichi Sankyo: Honoraria. Sandhu: Celgene: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Amgen: Consultancy; Bioverativ: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy; Gilead: Consultancy. Skikne: Bristol Myers Squibb: Current Employment. See: Bristol Myers Squibb: Current Employment. Ugidos: Bristol Myers Squibb: Current Employment. Risueño: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Chan: Bristol Myers Squibb: Current Employment. Thakurta: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Beach: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Lopes de Menezes: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties.

KMT2A partial tandem duplication (KMT2A-PTD), characterized by a large internal duplication spanning 6-8 exons, has been documented in adult AML with a prevalence of 3-10% and is associated with poor outcomes. Despite the high prevalence of KTM2A fusions and known associated outcomes, prevalence and clinical implications of KMT2A-PTD has not been well characterized in childhood AML. We interrogated the transcriptome and associated clinical and genomic data from pediatric AML patients treated on COG AAML1031 to define the prevalence of KMT2A-PTD, frequency of co-occurring genetic mutations and outcomes associated with this variant. Ribo-depleted RNA seq data from 1,294 patients with AML (age 0-29 years) enrolled on COG AAML1031 with available cytogenetic, molecular, and clinical data were utilized. Gene fusions, internal tandem duplications (ITD) and partial tandem duplications (PTD) were detected by Cicero. Conventional karyotyping and mutational analysis including NGS were used to determine additional cytogenetic and molecular abnormalities. Response was measured by 5-year overall survival (OS), event-free survival (EFS), disease-free survival (DFS) and relapse risk (RR). Of the 1,294 patients studied, KMT2A-PTD was identified in 20 patients (1.5%). Evaluation of karyotype demonstrated striking paucity of karyotypic alterations with 75% with normal karyotype; 3 cases (15%) of trisomy 11 were identified. In contrast to KMT2A-rearranged (KMT2A-r) AML, which has the highest prevalence in young patients (median age 3.3 years), the median age with KMT2A-PTD was 13.4 years (p We evaluated the significance of KMT2A-PTD on clinical outcome. Patients with KMT2A-PTD had a poor response to induction therapy with a morphologic CR rate of 45% and rate of residual disease (MRD) positivity by flow cytometry after initial course of therapy was 40%. Additionally, high rates of relapse were noted for patients with KMT2A-PTD with a RR of 53%. EFS for patients with and without KMT2A-PTD was 39% vs. 46%, respectively (p=0.54) with a corresponding OS of 58% and 64% (p=0.61). Outcome analysis for the KMT2A-PTD cohort demonstrated dual KMT2A-PTD/FLT3-ITD patients had an EFS of 46% compared to 29% for KMT2A-PTD/non-ITD patients (p=0.62, Figure 1B). We inquired whether hematopoietic stem cell transplant (HSCT) may modify outcomes in patients with KMT2A-PTD. Of the 20 patients with KMT2A-PTD, 7 (35%) proceeded to HSCT in CR1, with the indication in 6 of 7 patients due to FLT3-ITD high allelic ratio (HAR, ≥0.4). Stem cell transplant recipients had a DFS of 83% vs. 0% for those who continued on protocol chemotherapy (p=0.002, Figure 1C) with corresponding OS of 100% vs. 43%, respectively (p=0.05). In this large cohort of childhood AML patients treated on AAML1031, we identified a small subset of patients with KMT2A-PTD and show the high prevalence of co-occurring FLT3 mutations. Although KMT2A-PTD patients with and without FLT3-ITD had similar outcomes, the cohort who received HSCT in CR1 (most with FLT3-ITD) experienced improved outcomes compared to the rest of the cohort, suggesting that intensification of therapy may benefit this group of patients overall. Further research into KMT2A-PTD in pediatric AML will guide future risk-adapted therapy and enhance understanding of biologic implications of this lesion, including whether altered KMT2A may serve as a therapeutic target as it may for KMT2A-r AML. Figure 1 Figure 1. Disclosures Pollard: Syndax: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees.

Background and Methods: FMS-like tyrosine kinase 3 (FLT3) internal tandem duplication (FLT3-ITD) and tyrosine kinase domain mutation (FLT3-TKD) are types of mutations present in approximately 30% of patients with acute myeloid leukemia (AML). Currently, FLT3 inhibitors (FLT3i) are available in clinical practice, and the second-generation FLT3i, gilteritinib and quizartinib, are being used in Japan. However, the actual epidemiology of FLT3 mutations and co-existing gene alterations, particularly resistance mechanisms after FLT3i treatment, have not been thoroughly investigated in a Japanese population. Therefore, we conducted an actionable mutation profiling multicenter study, Hematologic Malignancies (HM)-SCREEN-Japan 01 (UMIN000035233), in which a comprehensive genomic assay was performed using the FoundationOne Heme (F1H) panel for patients with relapsed/refractory (R/R) AML and patients with newly diagnosed AML who were ineligible for standard chemotherapy (ND unfit). Paraffin-embedded bone marrow samples were used for next-generation sequencing (NGS) examination using the F1H panel. We analyzed the relationships between FLT3 gene mutations and other mutations and then chronologically evaluated the variant allele frequency (VAF) of gene mutations in the genomic profiles of patients with AML receiving FLT3i. Results: Of the 171 patients who participated in this study, 49 (28.7%) had FLT3 mutations. FLT3-ITD and FLT3-TKD accounted for 59% and 43% of all cases of FLT3 mutations, respectively. Two patients (4%) were found to have dual mutations: one with FLT3-ITD plus FLT3-TKD and another with FLT3-ITD plus FLT3-F691L. Eight patients (4.5%) were found to have the FLT3-N676K mutation, which is sensitive to gilteritinib but undetectable by currently available PCR-based companion diagnostic tools in Japan. Frequently co-occurring mutations included those of NPM1 (37%), DNMT3A (33%), IDH1/IDH2 (27%), WT1 (24%), and RUNX1 (22%). Mutations in RAS pathway-related genes (e.g., KRAS, NRAS, and PTPN11) were observed in 15 patients (31%). No gene alteration showed statistically significant co-occurrence with the FLT3mutation. However, the median number of mutations that co-exist with FLT3-TKD was slightly higher than that of FLT3-ITD (four genes [3-5] vs. three genes [2-5]). Sequential changes in the VAF of each gene alteration were investigated in nine patients with FLT3 mutations who eventually gained resistance to FLT3i. It was suggested that there were various patterns in clone evolution. Some showed the acquisition of not only CBL or NRAS as RAS pathways, but also other driver mutations: one showed a persistent FLT3mutation, one showed FLT3-ITD plus FLT3-TKD, and one showed a newly acquired FLT3 mutation substituting an existing FLT3 mutation. We also found that founder mutations, such as the DNMT3Amutation, remain even after eradication of FLT3 mutation during treatment with FLT3i, which could be the cause of the outcome of complete remission with incomplete hematologic recovery. Conclusions: This is the first report to analyze R/R and ND unfit AML cases in a Japanese cohort using F1H NGS, revealing a higher incidence of FLT3-ITD/TKD mutations than previously reported. Therefore, F1H mutational analyses for R/R and ND unfit AML patients harboring FLT3-ITD/TKD mutations may reveal novel therapeutic targets that are sensitive to FLT3i. Samples from these patients showed non-canonical gain-of-function mutations, such as N676K, S451F, V592D, and F691L, which could guide the selection of optimal anti-FLT3 therapies. In addition, longitudinal NGS analysis revealed clonal evolution in cases in which resistance to the FLT3i, gilteritinib and quizartinib were observed. Time-dependent analysis of allele frequencies can help evaluate the details of leukemia clonal evolution and provide optimal treatment options. Figure Legends Fig.1 Overview of gene mutations using F1H NGS analyses. The color of each column indicates the type of genetic mutation. Blue column; point mutation/insertion/deletion, green column; fusion gene, purple column; dual mutations. Fig.2 The chronological changes of leukemic cells fractions bearing each gene mutations during treatment with FLT3 inhibitors, gilteritinib and quizartinib. Figure 1 Figure 1. Disclosures Shibayama: Otsuka: Honoraria; Pfizer: Honoraria; Bristol-Myers Squibb: Honoraria; Sanofi: Honoraria; Nippon Shinyaku: Honoraria; Fujimoto: Honoraria; Daiichi Sankyo: Speakers Bureau; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Chugai: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Research Funding; Novartis: Research Funding, Speakers Bureau; Eisai: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Research Funding, Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Ono: Research Funding, Speakers Bureau; Celgene: Research Funding; Mundi Pharma: Honoraria; Essentia Pharma Japan: Research Funding. Yamauchi: Otsuka: Research Funding; Ono Pharmaceutical: Honoraria; Pfizer: Honoraria, Research Funding; Chugai: Honoraria; Abbie: Research Funding; Astellas: Research Funding; Daiichi Sankyo: Research Funding; Solasia Pharma: Research Funding. Kondo: Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; Bristol-Myers Squibb Company: Honoraria; Novartis Pharma KK: Honoraria; Otsuka Pharmaceutical Co., Ltd.: Honoraria, Research Funding; Astellas Pharma Inc.: Consultancy, Honoraria; SANWA KAGAKU KENKYUSHO CO.,LTD.: Consultancy. Yamamoto: IQIVA/Genmab: Research Funding; Micron: Honoraria; Zenyaku: Honoraria, Research Funding; Yakult: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; SymBio: Honoraria, Research Funding; Solasia Pharma: Research Funding; Sanofi: Honoraria; Otsuka: Honoraria, Research Funding; Ono: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Nippon Shinyaku: Honoraria, Research Funding; Mundipharma: Research Funding; MSD: Honoraria; Meiji Seika Pharma: Consultancy, Honoraria, Research Funding; Kyowa Kirin: Honoraria; Janssen: Honoraria; HUYA: Consultancy; IQIVA/HUYA: Honoraria; IQIVA/Incyte: Research Funding; Eisai: Honoraria, Research Funding; Daiichi Sankyo: Honoraria; Chugai: Honoraria, Research Funding; Bristol-Myers Squibb/Celgene: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; ADC Therapeutics: Honoraria. Kuroda: Kyowa Kirin: Honoraria, Research Funding; Otsuka Pharmaceutical: Honoraria, Research Funding; Astellas Pharma: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; MSD: Research Funding; Abbvie: Consultancy, Honoraria; Ono Pharmaceutical: Honoraria, Research Funding; Eisai: Honoraria, Research Funding; Sysmex: Research Funding; Pfizer: Honoraria, Research Funding; Nippon Shinyaku: Honoraria, Research Funding; Shionogi: Research Funding; Asahi Kasei: Research Funding; Taiho Pharmaceutical: Research Funding; Fujimoto Pharmaceutical: Current Employment, Honoraria, Research Funding; Dainippon Sumitomo Pharma: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Chugai Pharmaceutical: Honoraria, Research Funding; Bristol-MyersSquibb: Consultancy, Honoraria, Research Funding; Janssen Pharmaceutical K.K: Consultancy. Usuki: Otsuka Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Novartis Pharma K.K.: Research Funding, Speakers Bureau; Ono Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Janssen Pharmaceutical K.K.: Research Funding; Celgene K.K.: Research Funding, Speakers Bureau; Takeda Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Nippon-Boehringer-Ingelheim Co., Ltd.: Research Funding; Mundipharma K.K.: Research Funding; Amgen-Astellas Biopharma K.K.: Research Funding; Nippon-Shinyaku Co., Ltd.: Research Funding, Speakers Bureau; Kyowa-Kirin Co., Ltd.: Research Funding, Speakers Bureau; Pfizer Japan Inc.: Research Funding, Speakers Bureau; Alexion Pharmaceuticals, Inc.: Research Funding, Speakers Bureau; Eisai Co., Ltd.: Speakers Bureau; MSD K.K.: Research Funding, Speakers Bureau; PharmaEssentia Japan KK: Research Funding, Speakers Bureau; Yakult Honsha Co., Ltd.: Research Funding, Speakers Bureau; Daiichi Sankyo Co., Ltd.: Research Funding, Speakers Bureau; Sumitomo-Dainippon Pharma Co., Ltd.: Research Funding; SymBio Pharmaceuticals Ltd.: Research Funding, Speakers Bureau; Gilead Sciences, Inc.: Research Funding; Bristol-Myers-Squibb K.K.: Research Funding, Speakers Bureau; Apellis Pharmaceuticals, Inc.: Research Funding; AbbVie GK: Research Funding, Speakers Bureau; Astellas Pharma Inc.: Research Funding, Speakers Bureau; Incyte Biosciences Japan G.K.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Sanofi K.K.: Speakers Bureau; Amgen K.K.: Research Funding. Yoshimitsu: Novartis: Honoraria; Takeda: Honoraria; Sanofi: Honoraria. Ishitsuka: Eisai: Other: Personal fees, Research Funding; Sumitomo Dainippon Pharma: Other: Personal fees, Research Funding; Genzyme: Other: Personal fees; Astellas Pharma: Other: Personal fees, Research Funding; Pfizer: Other: Personal fees; Novartis: Other: Personal fees; Janssen Pharmaceuticals: Other: Personal fees; Taiho Pharmaceuticals: Other: Personal fees, Research Funding; Mundipharma: Other: Personal fees; Takeda: Other: Personal fees, Research Funding; BMS: Other; Chugai Pharmaceutical: Honoraria, Other: Personal fees, Research Funding; Celgene: Honoraria, Other: Personal fees; Ono Pharmaceutical: Other: Personal fees, Research Funding; Kyowa Kirin: Other: Personal fees, Research Funding; Daiichi Sankyo: Consultancy, Other: Personal fees; MSD: Research Funding; Teijin Pharma: Research Funding; Otsuka Pharmaceutical: Other: Personal fees; Shire: Other; Mochida: Other: Personal fees, Research Funding; Asahi kasei: Research Funding; Eli Lilly: Research Funding; Huya Japan: Other: Personal fees. Ono: Kyowa Kirin Co., Ltd.: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Janssen Pharmaceutical K.K: Honoraria; Eisai Co., Ltd.: Honoraria; Astellas Pharma Inc.: Honoraria; Takeda Pharmaceutical Company Limited.: Honoraria; ONO PHARMACEUTICAL CO., LTD.: Honoraria, Research Funding; Otsuka Pharmaceutical Co., Ltd.: Honoraria; Pfizer Japan Inc.: Honoraria; Bristol-Myers Squibb Company: Honoraria; Novartis Pharma KK: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria, Research Funding; DAIICHI SANKYO COMPANY, LIMITED.: Honoraria; Mundipharma K.K.: Honoraria; TAIHO PHARMACEUTICAL CO., LTD.: Research Funding; Merck Sharp & Dohme: Honoraria, Research Funding. Takahashi: Kyowahakko-Kirin: Research Funding; Toyamakagaku: Research Funding; Otsuka Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Chugai: Research Funding; Eizai: Research Funding; Asahikasei: Research Funding; Ono: Research Funding. Iyama: SymBio Pharmaceuticals: Research Funding; Astellas: Honoraria; CSL Behring: Honoraria; Daiichi Sankyo: Honoraria; Otsuka Pharmaceuticals Factory: Honoraria; Otsuka Pharmaceuticals Factory: Honoraria; MSD: Research Funding; Nippon Shinyaku: Honoraria; Novartis: Honoraria; Otsuka: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Alexion Pharmaceuticals: Honoraria, Research Funding. Izutsu: Allergan Japan: Honoraria; Symbio: Honoraria, Research Funding; Pfizer: Research Funding; Ono: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; MSD: Research Funding; Janssen: Honoraria, Research Funding; Incyte: Research Funding; Genmab: Honoraria, Research Funding; Chugai: Honoraria, Research Funding; Beigene: Research Funding; Bayer: Research Funding; AstraZeneca: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Yakult: Research Funding; Takeda Pharmaceutical: Honoraria, Research Funding; Kyowa Kirin: Honoraria, Research Funding; HUYA Bioscience International: Research Funding; Eisai: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; FUJI FILM Toyama Chemical: Honoraria. Minami: Bristol-Myers Squibb Company: Honoraria; Pfizer Japan Inc.: Honoraria; Takeda: Honoraria; Novartis Pharma KK: Honoraria; Astellas: Honoraria; Ono: Research Funding; CMIC: Research Funding.

Introduction: FLT3 internal tandem duplication mutations are independent risk factors for worse overall survival (OS) and increased relapse risk in AML patients and thus are an attractive target fo...

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with inadequate treatment options. Approximately one-third of cases have a FLT3-ITD or FLT3-TKD mutation which leads to constitutive tyrosine kinase activation which contributes to leukemogenesis. The FLT3-ITD mutation is associated with a particularly poor prognosis. Midostaurin is a multi-kinase inhibitor active against the FLT3 receptor. Midostaurin was approved by the US FDA in April 2017 for treatment of newly diagnosed FLT3-mutant AML in combination with chemotherapy. Areas covered: Standard treatment of FLT3-mutant AML and outcomes. Early clinical development of midostaurin including pharmacokinetics and metabolism. The development of midostaurin in FLT3-mutant AML is then outlined including review of the phase I, II, and III trials of midostaurin as a single agent and in combination with chemotherapy. Expert commentary: The approval of midostaurin represents the first new therapy for AML in several decades. It is also the first targeted therapy approved for AML. Future studies will focus on defining mechanisms of resistance to midostaurin as well as establishing the role of midostaurin in combination with hypomethylating agents and as maintenance therapy. Second generation, more potent and selective FLT3 inhibitors are also in development; these agents need to be compared to midostaurin.

Dynamics of molecular response in AML patients with NPM1 and FLT3 mutations undergoing allogeneic stem cell transplant

Background: Despite widespread interest in pain management and opioid use across the United States, information on pain and opioid utilization in patients with relapsed or refractory acute myeloid leukemia (R/R AML) is lacking. Better understanding of patient-reported outcomes (PROs) specific to pain could be used to identify strategies to improve the quality of life in patients with R/R AML. Aim/Objective: To describe pain and opioid use in patients with FLT3 mutation-positive (FLT3mut+)R/R AML receiving either gilteritinib or salvage chemotherapy (SC) using PRO data collected from the ADMIRAL study (NCT02421939). Methods: ADMIRAL was a phase 3, open-label, multicenter, active-controlled randomized study comparing the efficacy and safety of gilteritinib to SC in patients with FLT3mut+ R/R AML. Pain was assessed using selected items from the Functional Assessment of Cancer Therapy - Leukemia (FACT-Leu; GP4 item: "I have pain") and the EuroQol 5-Dimension 5-Level Questionnaire (EQ-5D-5L; Pain/Discomfort domain). Data for these instruments were collected at baseline (BL), Day 1 of every treatment cycle, and end of treatment (EOT). A modified EOT (mEOT) was defined as the last PRO assessment before patient discontinuation, study data cut-off date, or patient death. Patients on high-intensity chemotherapy (HIC) were treated for up to two cycles depending on treatment response; as such, only changes from BL to Cycle 2 were evaluated. Opioid utilization, including percentage of patients using any opioid medication, specific medications, duration of use, and use by transfusion dependence, was also described. Analyses of the intention-to-treat population using analysis of covariance, including BL score, response to first-line AML therapy, and investigator-preselected SC as covariates, were conducted to estimate least squares mean (LSM) and compare the differences in pain question responses between treatment arms. Descriptive statistics were used to describe opioid utilization. Results: Of 371 eligible patients, 247 were randomized to gilteritinib and 124 to SC. The median age for both groups was 62 years and slightly more patients were female (gilteritinib, 53.0%; SC, 56.5%). Improvements at the mEOT from BL in the Fact-Leu GP4 item were observed in both gilteritinib (LSM -0.3) and SC (LSM -0.1). Scores also changed on the EQ-5D-5L at the mEOT from BL for both groups (gilteritinib, LSM 0.2; SC, LSM 0.3). No treatment differences were observed between gilteritinib vs SC on the change from BL to Cycle 2 or mEOT on the Fact-Leu GP4 item (LSM [95% CI] of -0.1 [-0.65, 0.38]; P=0.6016 and -0.2 [-0.53, 0.21]; P=0.3902, respectively) or on the EQ-5D-5L Pain/Discomfort domain (LSM [95% CI] of 0.2 [-0.21, 0.62]; P=0.3255 and -0.1 [-0.38, 0.23]; P=0.6288, respectively). During Cycles 1 and 2, no differences were identified between gilteritinib or SC on the percentage of patients using opioids (Cycle 1: 49.8% vs 55.6%; Cycle 2: 58.9% vs 62.7%, respectively) or the time-averaged duration of use (Cycle 1: 12.4 days vs 14.1 days; Cycle 2: 15.0 days vs 17.2 days, respectively). Patients on gilteritinib were less likely to use opioids during the first two cycles compared with patients on HIC, when stratified by chemotherapy intensity (Cycle 1: 49.0% vs 72.0%, P Conclusions: Patients with FLT3mut+ R/R AML receiving gilteritinib or SC demonstrated modest changes in responses to pain-related assessments at EOT compared with BL values. Opioids were used more frequently by patients receiving HIC regimens and transfusion-dependent patients receiving gilteritinib. These data suggest that treatments for FLT3mut+ R/R AML may impact opioid use; further study should be done to determine the relationships between these factors and their potential impact on overall quality of life. Disclosures Cella: DSI: Consultancy, Research Funding; Evidera: Consultancy; Ipsen: Consultancy, Research Funding; Mei Pharma: Consultancy; Oncoquest: Consultancy; ASAHI KASEI PHARMA CORP.: Consultancy; BMS: Consultancy, Research Funding; IDDI: Consultancy; Kiniksa: Consultancy; Novartis: Consultancy; Pfizer: Consultancy, Research Funding; Apellis: Consultancy; Alexion: Research Funding; Clovis: Research Funding; Janssen: Research Funding; Pled Pharma: Research Funding; PROMIS Health Org: Membership on an entity's Board of Directors or advisory committees, Other; BlueNote: Consultancy; Astellas: Consultancy, Honoraria; FACIT.org: Membership on an entity's Board of Directors or advisory committees, Other: President; Abbvie: Consultancy, Research Funding. Ritchie:Abbvie: Honoraria; Sierra Oncology: Honoraria; Novartis: Honoraria; Pfizer: Honoraria, Research Funding; Jazz pharmaceuticals: Honoraria, Research Funding; Incyte: Speakers Bureau. Kanda:Pfizer: Honoraria, Research Funding; Astellas Pharma: Honoraria, Research Funding; Janssen: Honoraria; Shionogi: Research Funding; Chugai Pharma: Honoraria, Research Funding; Otsuka: Honoraria, Research Funding; Celgene: Honoraria; Sumitomo Dainippon Pharma: Honoraria; Eisai: Honoraria, Research Funding; Novartis: Honoraria; Kyowa Kirin: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria; Takeda Pharmaceuticals: Honoraria; Alexion Pharmaceuticals: Honoraria; Shire: Honoraria; Daiichi Sankyo: Honoraria; Ono Pharmaceutical: Honoraria; Nippon Shinyaku: Honoraria, Research Funding; Mochida Pharmaceutical: Honoraria; Mundipharma: Honoraria; Sanofi: Honoraria, Research Funding; Meiji Seika Kaisha: Honoraria; Merck Sharp & Dohme: Honoraria. Ivanescu:Astellas: Other: IQVIA employee which is a contracted by Astellas. Pandya:Astellas Pharma, Inc.: Current Employment. Shah:Astellas: Current Employment.

Biologically, Acute myeloid leukemia (AML) is highly heterogenous. AML with cup-like blast morphology variant has been reported to have important role in risk group stratification and treatment implications. In pediatric age group, this morphology and its clinical implication is rarely discussed. Although this morphology variant is not stated in World Health Organization (WHO) classification of Tumours of Haematopoietic and Lymphoid Tissues, it is associated with poor outcome from the association with other features. A 10- year old girl diagnosed to have AML with this morphology variant is reported in this study. Her laboratory features were hyperleucocytosis, high D-dimer, and blasts morphology of cup-like cells and few mimic the bilobed features of acute promyelocytic leukemia (APML). Further investigation showed clinical and laboratory features similar to what had been reported before in adults, including the presence of adverse marker of Fms-like tyrosine kinase 3 (FLT3) mutation. She was treated with chemotherapy, following which the bone marrow examination documented marrow in remission. Unfortunately, she succumbed to the disease complication from sepsis and marrow failure after few months of diagnosis. Haemato-morphologists might consider this unique morphological recognition and correlate it with other findings, including molecular testing for proper clinical evaluation. The blast feature and haematological findings could predict the clinical behaviour of this type of AML and guide the patient management. This morphological variant serves an important role especially if molecular testing is not available in some parts of the world or at the time of presentation when the result is still pending.

Acute myeloid leukemia (AML) with FLT3-mutation carries a poor prognosis, and allogeneic stem cell transplantation (allo-SCT) is recommended at first complete remission (CR1). We assessed 462 adults (median age 50 years) with FLT3-mutated AML allografted between 2010 and 2015 from a matched related (40%), unrelated (49%), or haploidentical donor (11%). The median follow-up of alive patients was 39 months. Day-100 acute graft versus host disease (GVHD) grades II-IV and III-IV were encountered in 26% and 9%, whereas the 2-year incidence of chronic and extensive chronic GVHD were 34% and 16%, respectively. The 2-year incidences of relapse and nonrelapse mortality were 34% and 15%, respectively. The 2-year leukemia-free survival, overall survival (OS), and GVHD relapse-free survival (GRFS) were 51%, 59%, and 38%, respectively. In multivariate analysis, NPM1-mutation, transplantation in CR1, in vivo T-cell depletion, and posttransplant sorafenib improved OS, whereas more than one induction (late CR1) negatively affected OS. Similarly, NPM1-mutation, a haploidentical donor, T-cell depletion, and sorafenib maintenance improved GRFS, whereas late CR1 or persistent disease negatively affected it. In conclusion, FLT3-mutated AML remains a challenge even following allo-SCT. In vivo T-cell depletion and posttransplant sorafenib significantly improve OS and GRFS, and may be considered as standard of care. ispartof: Clin Hematol Int vol:1 issue:1 pages:58-74 ispartof: location:United States status: Published online

A 53-years old man with FLT3-ITD-mutant Acute Myeloid Leukemia relapsed ten months after hemopoietic allogeneic stem cell transplant as multiple cutaneous Myeloid Sarcomas. Molecular testing was performed on the core-needle biopsy of the lesion and since positive for the FLT3 mutation, a targeted-therapy with the tyrosine kinase inhibitor sorafenib as single agent was started, obtaining a sustained complete response. After 18 months of therapy patient relapsed on the previously involved sites, because of acquisition of sorafenib-resistant mutation and switched to systemic therapy. Sorafenib proved to be able to distribute in skin and subcutaneous tissues and could be safely used. Molecular testing on Myeloid Sarcoma can be therefore an innovative and effective approach in the management of extra medullary leukemia.

7020 Background: The advent of genomic sequencing technologies has revealed underlying genetic alterations, such as FLT3 mutations, that can be targeted in acute myeloid leukemia (AML). However, development of resistance limits the durability of response. Recent data has implicated that factors from the bone marrow microenvironment mediate initial resistance to FLT3 inhibitors (FLT3i) in AML. We combined high dimensional characterization techniques, time-of-flight mass cytometry (CyTOF) and RNA sequencing, to examine sequential marrow stromal samples from a subset of patients with FLT3 mutated AML treated with the FLT3i gilteritinib. Here, we report on the heterogeneity and evolution of cell surface and secreted factors over time. Methods: RNA sequencing of primary FLT3-ITD stromal samples (N = 29) from pre-study and on-treatment patients enabled prioritization of candidate targets for CyTOF. Target-specific purified antibodies were purchased pre-conjugated to metal lanthanides or conjugated in house according to manufacturer protocols (after validation via traditional flow cytometry). Primary stromal cells were cultured ex vivo until confluent and were harvested and stained according to a standardized protocol, and subsequently run on a Helios (Fluidigm) mass cytometer. A computational approach was employed to compensate and visualize data via the CATALYST R package. A total of four pre-treatment and four post-gilteritinib timepoint isolates (N = 8) were analyzed. Results: A 36-target mass cytometry panel revealed protein level differences in patients before and after gilteritinib therapy. Dimensional reduction techniques such as MDS and UMAP showed that samples taken from later timepoints clustered together compared to their earlier counterparts with respect to global protein expression. Inflammatory mediators such as IL1-beta and MCP-1 were upregulated in patient stroma soon after gilteritinib treatment and therefore potentially contribute to early resistance. Novel markers previously implicated in early resistance to targeted therapies in AML such as FGF2 and FGFR1 similarly peaked earlier in treatment, mimicking the clinical course of expression observed in marrow stroma of patients treated with another FLT3 inhibitor quizartinib (Traer et al. Cancer Res. 2016). Conclusions: Our findings show that primary marrow stroma evolves during gilteritinib treatment, and that stromal proteins previously reported to promote early resistance to FLT3i are also upregulated during gilteritinib resistance. The heterogeneity of stromal cell isolates detected by mass cytometry highlights the utility of high dimensional tracking of disease course in patients, and may enable a better understanding of how the temporal evolution of the marrow microenvironment contributes to development of resistance to targeted therapies such as gilteritinib and other FLT3i over time.

Based upon the clinical behavior of three patients, we suggest that the combination of low-dose Ara-C and all-trans retinoic acid may potentially be effective in some elderly patients, unfit for intensive chemotherapy, affected with NPM1-mutated acute myeloid leukemia without FLT3 mutations, warranting perspective clinical studies in these selected patients.

Whether or not FLT3 mutations are present and expressed within a leukemic hematopoietic stem cell has engendered some controversy. New evidence has now been presented on this issue that could change the way we manage the disease in the future.

Background: Conventional treatments for follicular thyroid cancer (FTC) can be ineffective, leading to poor prognosis. The aim of this study was to identify mutations associated with FTC that would serve as novel molecular markers of the disease and its outcome and could potentially identify new therapeutic targets. Methods: FLT3 mutations were first detected in a 29-year-old White female diagnosed with metastasized, treatment-refractory FTC. Analyses of FLT3 mutational status through next-generation sequencing of formalin-fixed, paraffin-embedded FTC specimens were subsequently performed in 35 randomly selected patients diagnosed with FTC. Results: FLT3 mutations were found in 69% of patients. FLT3 mutation-positive patients were significantly older than those that were FLT3 mutation-negative [median age at diagnosis 54 (36–82) versus 45 (27–58) ( p = 0.023)]. Patients over 60 years were 23 times more likely to be FLT3 mutation-positive ( p = 0.006). However, the number of FLT3 mutations did not correlate with age ( r-Pearson: –0.244, p-value: 0.25). A total of 26 mutations were identified in the FLT3 gene with 2–16 FLT3 mutations in each FLT3 mutation-positive patient (mean: 5.6 mutations/patient). Tyrosine kinase domain (TKD) mutations in the FLT3 gene were detected in 58% of FLT3 mutation-positive patients. All FLT3 mutation-positive patients with a disease stage of pT2N1 or worse harbored at least one mutation in the TKD of FLT3. Conclusions: There is a wide spectrum and high frequency of FLT3 mutations in FTC. The precise role of FLT3 mutations in the genesis of FTC, as well as its potential role as a therapeutic target, requires further investigation.