Incidence and Characteristics of Central Nervous System Involvement in Adult Acute Myeloid Leukemia Patients

Features of central nervous system (CNS) involvement in acute myeloid leukemia (AML) are not well-defined. Unlike acute lymphoblastic leukemia, there are limited guidelines for the use of intrathecal chemotherapy with induction for AML, and institutional practices vary. Unfortunately, AML patients with CNS involvement often have worse outcomes compared to those without CNS involvement (Del Principe et al., 2018; Rozovski et al., 2015). It is important to better understand the incidence and predictive clinical and features of CNS involvement in AML to identify patients for diagnostic testing and intrathecal chemotherapy. This retrospective analysis evaluated the incidence and characteristics of CNS involvement in adult AML patients at our institution. CNS screening is recommended for AML patients with specific characteristics, including CNS symptoms, monocytic phenotype, FLT3-internal tandem duplication gene mutation, and hyperleukocytosis (>100,000 white blood cells per microliter). Treatment recommendations for CNS involvement include intrathecal methotrexate, intrathecal cytarabine, or a combination of both. In this IRB-approved retrospective study, medical records were analyzed from the University of Kansas Medical Center from years 2015-2020. Patients were selected by searching the electronic medical record for adult AML patients who received a diagnostic lumbar puncture. Characteristics of interest included presence of CNS symptoms, monocytic phenotype, FLT3 mutation, and hyperleukocytosis. Characteristics that prompted CNS screening were recorded for each patient. Additional data collection included next-generation sequencing (NGS), cytogenetic results, and whether CNS screening occurred during an initial diagnosis or during an AML relapse. Lastly, the number of intrathecal chemotherapy doses was recorded for each patient. The incidence of CNS involvement was determined by dividing the number of newly diagnosed AML CNS-positive patients by the total number of newly diagnosed AML patients. Screening detection rates were determined by dividing the number of CNS-positive patients with each characteristic by the total number that received a lumbar puncture. The percentage of CNS-positive patients with each characteristic was determined by dividing the number with each specific characteristic by the total number of CNS-positive patients. The number of intrathecal chemotherapy doses required for CNS clearance was determined using data only from patients that achieved CNS clearance. Forty-eight patients met current guidelines for CNS screening; 25 were CNS-positive and 23 were CNS-negative (overall screening detection rate of 52%). The incidence of CNS involvement among all newly diagnosed adult AML patients was 3.24%. Screening detection rates were 58% for patients with 3 characteristics, 60% for 2 characteristics, 45% for CNS symptoms, and 30% for monocytic phenotype. Not enough patients presented with the FLT3 mutation or hyperleukocytosis in isolation to calculate accurate detection rates. The CNS-positive group consisted of 28% with 3 characteristics, 24% with 2 characteristics, 20% with CNS symptoms, 12% with monocytic phenotype, 4% with FLT3 mutation, 4% with hyperleukocytosis, and 36% were screened during a relapse rather than at initial diagnosis. Two patients were CNS-positive without any of our characteristics of interest (screened due to extramedullary involvement at presentation and the other was screened as part of pre-transplant evaluation). Seventeen patients achieved CNS clearance with 41% requiring 1 dose of intrathecal chemotherapy, 35% requiring 2 doses, and 24% requiring more than 2 doses. NGS and cytogenetic results did not reveal any additional associations. This data indicates that current AML CNS screening guidelines appear to properly identify a patient population at risk for CNS involvement. At our institution, 52% of screened patients were CNS-positive. This analysis also revealed a diverse distribution of characteristics among AML patients with CNS involvement, and patients commonly presented with multiple risk factors. These results emphasize the need for ongoing research to further delineate CNS involvement risk factors in AML. This data will be used for current policy analysis at our institution and potentially prospective studies to better evaluate outcomes for AML patients with CNS involvement. Figure 1 Figure 1. Disclosures Lin: AbbVie, Aptevo Therapeutics, Astellas Pharma, Bio-Path Holdings, Celgene, Celyad, Genentech-Roche, Gilead Sciences, Incyte, Jazz Pharmaceuticals, Novartis, Ono Pharmaceutical, Pfizer, Prescient Therapeutics, Seattle Genetics, Tolero, Trovagene: Research Funding.

FDA Cleared Companion Diagnostics (CDx) Tests (IDH1, IDH2 and FLT3) for Acute Myeloid Leukemia (AML) Patient Care

Acute myeloid leukemia (AML) is one of the most lethal blood cancers from which nearly 10,000 people die in the United States each year. While therapies for other blood cancers have made some progress, the standard of care for AML, a combination of toxic chemotherapies, has changed very little over the past four decades. In recent years the US Food and Drug Administration (FDA) has been very active in approving targeted therapeutic drugs for AML patients including Midostaurin (Rydapt; 2017) and Gilteritinib (Xospata;2018) for FLT3 mutations; Enasidenib (Idhifa; 2017) for IDH2 mutations and Ivosidenib (Tibsovo; 2018) for IDH1 mutations. Additionally, the Leukemia and Lymphoma Society's Beat AML Master Clinical Trial has shown that waiting for molecular results prior to treatment decision leads to better outcomes. Versiti Blood Center of Wisconsin Diagnostics laboratory which is certified under the Clinical Laboratory Improvement Amendments (CLIA) and qualified to perform high complexity clinical laboratory testing has performed the verification studies and offers two companion diagnostics tests for IDH1 and IDH2 mutations for AML patients. Also, in collaboration with Invivoscribe Inc., the AML patient can be tested for Leukostrat CDx FLT3 mutations assay so that the same AML patient can get three CDx test results leading to available drug therapy treatment decision making by physicians. IDH1 CDX Test: IDH1 CDx is indicated as an aid in identifying AML patients with an IDH1 mutation for treatment with ivosidenib (TIBSOVO®). Mutations in codon R132 of IDH1 can be found in 6% to 10% of AML patients. The IDH1 CDx test detects five IDH1 mutations R132H (CAT), R132C (TGT), R132G (GGT), R132S (AGT), and R132L (CTT) using PCR technology with homogeneous real-time fluorescence detection. The assay sensitivity for these five IDH1 mutations is 100% at variant allele frequencies of 2% and higher and 98% or greater at variant allele frequencies of 1% and higher. This test has been approved by the FDA as companion diagnostic device (PMA number P170041). IDH2 CDx: IDH2 CDx is indicated as an aid in identifying AML patients with an IDH2 mutation for treatment with IDHIFA® (enasidenib). Mutations in the R140 and R172 codons of IDH2 8% to 19% of AML patients.The IDH2 CDX test detects nine IDH2 mutations (R140Q, R140L, R140G, R140W, R172K, R172M, R172G, R172S, and R172W) using PCR technology with real-time fluorescent detection. The assay sensitivity for these nine IDH2 mutations is 99.8% or greater at variant allele frequencies of 2% and higher or 93.5% or greater at variant allele frequencies of 1% and higher. This test has been approved by the FDA as companion diagnostic device (PMA number P170005). FLT3 CDx: The FLT3 Leukostrat® CDx Assay is the FDA approved (PMA number P160040) predictive test for the efficacy of midostaurin (RYDAPT®) therapy in all AML patients, regardless of cytogenetics and efficacy of gilteritinib (XOSPATA ® ) therapy in relapsed or refractory AML patients. FLT3 is one of the most commonly mutated genes in AML with 30% of patients at the time of diagnosis 1. The most prevalent type of FLT3 mutation is an internal tandem duplication (ITD) in the juxtamembrane domain. The second most common mutation type in the FLT3 gene is a tyrosine kinase domain (TKD) point mutation in the codon for an aspartate (D835) or an isoleucine (I836) residue. The LeukoStrat® CDx FLT3 Mutation Assay is a PCR-based, in vitro diagnostic test designed to detect internal tandem duplication (ITD) mutations and the tyrosine kinase domain (TKD) mutations D835 and I836 in genomic DNA extracted from mononuclear cells obtained from peripheral blood or bone marrow aspirates of patients diagnosed with AML. Versiti Blood Center sends the patient specimens to Invivoscribe Inc. where the LeukoStrat® CDx FLT3 Mutation Assay is performed and the interpretive comments are included in the patient report by Versiti. From our experience pathologists and treating physicians want molecular test results as fast as possible, especially for the actionable gene mutations in IDH1, IDH2 and FLT3. The IDH1 CDx, IDH2 CDx and FLT3 CDx tests are highly sensitive and Versiti provides average turn around time of 3 business days which enable rapid decision making on the recently available drug therapies for AML patients. We strongly recommend that the IDH1 CDx, IDH2 CDx and FLT3 CDx tests should be performed on all AML patients for better care. Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: In recent years the US Food and Drug Administration (FDA) approved targeted therapeutic drugs for AML patients including Midostaurin (Rydapt; 2017) and Gilteritinib (Xospata;2018) for FLT3 mutations; Enasidenib (Idhifa; 2017) for IDH2 mutations and Ivosidenib (Tibsovo; 2018) for IDH1 mutations.

Impact of FLT3 Mutation Clearance after Front-Line Treatment with Gilteritinib Plus Azacitidine, or Gilteritinib or Azacitidine Alone in Patients with Newly Diagnosed AML: Results from the Phase 2/3 Lacewing Trial

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 <10 −4 or <10 −3, where 10 −4 was based on previously published findings in patients with relapsed or refractory FLT3mut+ AML who were treated with gilteritinib (Altman JK et al., Cancer Med. 2021;10[3]:797-805) and 10 -3 was an additional exploratory threshold used because it provided a more balanced distribution of patients, given the small number of patients achieving mutation clearance at the 10 -4 threshold. 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.

FLT3 Gene Mutation in Acute Myeloid Leukemia: Correlation with Hematological, Immunophenotypic, and Cytogenetic Characteristics

Introduction In acute myeloid leukemia (AML), FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is a common driver mutation associated with high tumor burden and poor prognosis. This mutation is common in normal karyotype AML and such patients have high leukocyte count. The presence of this mutation can be predicted by certain hematological and immunophenotypic characteristics in day-to-day practice. Objective This study was undertaken to assess the strength of association between FLT3 gene mutation and hematological and immunophenotypic characteristics. Materials and Methods Morphological, hematological, immunophenotypic, and cytogenetic characteristics of FLT3 mutations recorded in 424 patients of AML in adults and children between 2016 and 2019 in a tertiary care cancer center in Western India. Blasts were classified according to French-American-British method. Tumor burden was assessed by serum lactate dehydrogenase (LDH) levels, leucocyte count, and peripheral smear blast percentage. Results Out of 424 cases, FLT3-ITD and FLT3-tyrosine kinase domain mutation were found in 72 and 25 AML patients, respectively. Patients with FLT3 mutation had high tumor burden, characterized by high leukocyte count (p < 0.001), peripheral blood (p = 0.01) and bone marrow (p = 0.03) blast percentage, and high serum LDH (mean 777.8 vs. 586; p = 0.10) compared with FLT3-negative patients. They also featured high platelet count (p < 0.001). Morphological, immunophenotypic, and cytogenetic characteristics also have been presented in the study. Conclusion Observations of the study suggest the presence of definitive hematological and immunophenotypic characteristics along with raised serum LDH levels serve as surrogate markers and indicators of FLT3 mutation in AML patients.

Synergistic targeting of FLT3 mutations in AML via combined menin-MLL and FLT3 inhibition

The interaction of menin (MEN1) and MLL (MLL1, KMT2A) is a dependency and provides a potential opportunity for treatment of NPM1-mutant (NPM1mut) and MLL-rearranged (MLL-r) leukemias. Concomitant activating driver mutations in the gene encoding the tyrosine kinase FLT3 occur in both leukemias and are particularly common in the NPM1mut subtype. In this study, transcriptional profiling after pharmacological inhibition of the menin-MLL complex revealed specific changes in gene expression, with downregulation of the MEIS1 transcription factor and its transcriptional target gene FLT3 being the most pronounced. Combining menin-MLL inhibition with specific small-molecule kinase inhibitors of FLT3 phosphorylation resulted in a significantly superior reduction of phosphorylated FLT3 and transcriptional suppression of genes downstream of FLT3 signaling. The drug combination induced synergistic inhibition of proliferation, as well as enhanced apoptosis, compared with single-drug treatment in models of human and murine NPM1mut and MLL-r leukemias harboring an FLT3 mutation. Primary acute myeloid leukemia (AML) cells harvested from patients with NPM1mutFLT3mut AML showed significantly better responses to combined menin and FLT3 inhibition than to single-drug or vehicle control treatment, whereas AML cells with wild-type NPM1, MLL, and FLT3 were not affected by either of the 2 drugs. In vivo treatment of leukemic animals with MLL-r FLT3mut leukemia reduced leukemia burden significantly and prolonged survival compared with results in the single-drug and vehicle control groups. Our data suggest that combined menin-MLL and FLT3 inhibition represents a novel and promising therapeutic strategy for patients with NPM1mut or MLL-r leukemia and concurrent FLT3 mutation.

Streamline - Retrospective Cohort Study of Relapsed or Refractory (R/R) FLT3-Mutated Acute Myeloid Leukemia (AML): Real-World Treatment, Testing Patterns, and Outcomes

Introduction: The past decade in AML research has led to increased emphasis on disease-related mutations and associated targeted therapies. FMS-like tyrosine kinase 3 (FLT3) mutations (FLT3+) are found in about 30% of AML patients and confer a poorer prognosis. Also, the availability of targeted therapies increases the value of testing for FLT3+ AML. A paucity of data exists regarding the real-world FLT3 testing rates in AML patients in both the newly diagnosed and R/R settings. As the treatment landscape for patients with R/R FLT3+ AML expands, it is important to understand how utilization of these therapies and trends in FLT3 testing impact patient outcomes in real-world settings. These updated results examined FLT3 testing trends, treatment patterns, and overall survival (OS) in patients with R/R FLT3+ AML. Patients were grouped based on the FDA approval of the second-generation FLT3 inhibitor gilteritinib (pre-gilteritinib approval vs. post-gilteritinib approval). Methods: This ongoing (01/01/2015-4/17/2020) retrospective study uses electronic medical record data of US patients from a network of 400+ oncology practices maintained in the Definitive Oncology Dataset, including practices affiliated with CancerLinQ. Eligible adult (≥18 years) patients who had a confirmed diagnosis of AML, FLT3+ status, and had ≥1 R/R event between 01/01/2015 and 02/20/2020 were included. FLT3 testing trends included testing performed at initial diagnosis, re-testing performed in the R/R setting, and changes in FLT3 mutation status. Treatment patterns included all systemic anticancer therapies received (including supportive care) for R/R FLT3+ AML. OS was measured from the first R/R event; patients without evidence of death were censored at the last observed visit. Kaplan-Meier analysis was applied to evaluate differences in OS by subsequent hematopoietic stem cell transplant (HSCT) status. Results: Data from 175 patients (50.9% male, n=89) with R/R FLT3+ AML were evaluated (n=124 pre-gilteritinib; n=51 post-gilteritinib). Most patients were White (72.0%; n=126) with a median age of 62 years (range: 20-86) at first R/R event. Median length of follow-up was limited for the post-gilteritinib cohort (9.2 months vs. 15.0 months for pre-gilteritinib, P&lt;0.001). Patients tested for FLT3 mutations at initial AML diagnosis increased from 84.7% (n=105/124) in the pre-gilteritinib cohort to 98.0% (n=50/51) in the post-gilteritinib cohort, and the rates of re-testing increased from 29.5% (n=31/105) to 46.0% (n=23/50) across the two cohorts (Figure 1). After the first R/R event, 18.9% (n=33/175) reported changes in their FLT3 mutation status. Seventy-four different treatment combinations were utilized at the first R/R event. Use of FLT3 tyrosine kinase inhibitors (TKIs), either alone or in combination with chemotherapy, increased from 30.6% (n=38/124) in the pre-gilteritinib cohort to 49.0% (n=25/51) in the post-gilteritinib cohort (Table 1). In the pre-gilteritinib cohort midostaurin (52.6%, n=20/38) and sorafenib (32.4%, n=13/38) were the most commonly prescribed FLT3 TKIs. In the post-gilteritinib cohort, the most common FLT3 TKI was gilteritinib (52.0%, n=13/25). Median OS (95% CI) across all patients at the first R/R event was 13.4 (9.0-17.6) months in the pre-gilteritinib cohort and 12.9 (7.0, NA) months in the post-gilteritinib cohort. Median OS was significantly shorter among patients that did not receive HSCT among all patients and the subset of treated patients (P&lt;0.05 for both values). Median OS for patients with no HSCT was 3.9 months longer in the post-gilteritinib cohort versus the pre-gilteritinib cohort (Table 2). Conclusion: An increase in FLT3 TKI use (both monotherapy and in combination) and a decrease in high-intensity chemotherapy was observed across the two cohorts. In the 18-month post approval period, FLT3 TKI use increased 60% with gilteritinib accounting for more than half of FLT3 TKIs used in the R/R setting. FLT3 re-testing increased by 55% in the R/R setting between the two cohorts; however, re-testing is suboptimal and there is a need to re-test as patients progress. Among pre- and post-treated patients that did not receive HSCT, there was an improvement in OS by almost 4 months, possibly due to increased use of targeted FLT3 TKIs. With recent approval of these targeted therapies, it will be important to continue to monitor FLT3 testing, treatment patterns, and clinical outcomes. Disclosures Zeidan: Celgene / BMS: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Ionis: Consultancy, Honoraria; BeyondSpring: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Research Funding; Otsuka: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; CCITLA: Other; Astex: Research Funding; Cardinal Health: Consultancy, Honoraria; Trovagene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Leukemia and Lymphoma Society: Other; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Jazz: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Taiho: Consultancy, Honoraria; Aprea: Research Funding; ADC Therapeutics: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; MedImmune/Astrazeneca: Research Funding; Acceleron: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Incyte: Consultancy, Honoraria, Research Funding; Cardiff Oncology: Consultancy, Honoraria, Other. Gilligan:ConcertAI: Current Employment. Grinblatt:Astellas: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Alexion: Speakers Bureau. Elsouda:Astellas: Current Employment. Sullivan:Astellas Pharma: Current Employment. Pandya:Astellas Pharma, Inc.: Current Employment.