Use Of Midostaurin Research Articles

Midostaurin shapes macroclonal and microclonal evolution of FLT3-mutated acute myeloid leukemia.

Despite the use of midostaurin (MIDO) with intensive chemotherapy (ICT) as the front-line treatment for FLT3-mutated acute myeloid leukemia (AML), complete remission rates are close to 60-70%, and relapses occur in over 40% of cases. Here we studied the molecular mechanisms underlying refractory/relapsed (R/R) situation in FLT3-mutated AML patients. We conducted a retrospective and multicenter study involving 150 patients with R/R AML harboring FLT3-ITD (n=130) and/or FLT3-TKD (n=26) at diagnosis assessed by standard methods. Patients were treated in front-line with ICT + MIDO (n=54) or ICT alone (n=96) according to the diagnosis date and label of MIDO. The evolution of FLT3 clones and co-mutations was analyzed in paired diagnosis-R/R samples by targeted high-throughput sequencing. Using a dedicated algorithm for FLT3-ITD detection, 189 FLT3-ITD microclones (allelic ratio [AR] < 0.05) and 225 macroclones (AR ≥ 0.05) were detected at both time points. At R/R disease, the rate of FLT3-ITD persistence was lower in patients treated with ICT + MIDO compared with patients not receiving MIDO (68% vs. 87.5%, P=0.011). In patients receiving ICT + MIDO, detection of multiple FLT3-ITD clones (referred to as "clonal interference") was associated with a higher FLT3-ITD persistence rate at R/R disease (multiple clones: 88% vs. single clones: 57%, P=0.049). Considering both treatment groups, if only 24% of FLT3-ITD microclones detected at diagnosis were retained at relapse, 43% of them became macroclones. Together, these results identify parameters influencing the fitness of FLT3-ITD clones and highlight the importance of using sensitive techniques for FLT3--ITD screening in clinical practice.

Improvement in Survival of Patients with FLT3 Mutated Acute Myeloid Leukemia: Results from a Retrospective Canadian Cohort

Introduction: FLT3 internal tandem duplication (ITD) mutations have been historically associated with inferior outcomes in patients with acute myeloid leukemia (AML) and an intermediate risk status as per the European LeukemiaNet (ELN) 2022 guidelines. In 2017, the US FDA granted approval to midostaurin for frontline treatment and a year later, gilteritinib for use in relapsed/refractory (R/R) AML. These agents began to be widely used in our provincial leukemia program in early 2018 as per the label indications. In this study, we compared clinical outcomes for patients with FLT3-ITD mutated AML before and after this change in British Columbia. Methods: We identified patients in our program database diagnosed with FLT3-ITD mutated AML from January 1, 2010 to December 31, 2021. Only patients receiving intensive chemotherapy with cytarabine and anthracycline were included. Patients were divided into two eras: 2010-2017 (era 1) and 2018-2021 (era 2). The two eras were compared in terms of patient characteristics, genetics, rate of complete remission (CR) and CR with incomplete count recovery (CRi), receipt of allogeneic stem cell transplant (alloSCT) and the overall and relapse free survival (OS and RFS). OS was calculated from diagnosis to death from any cause and was not censored at the time of alloSCT. RFS was calculated from CR/CRi to relapse. Patients without an event during the study period were censored at the time of last follow-up. Categorical variables were compared using Chi-square and Fisher exact tests and continuous variable were compared using paired T tests. Kaplan-Meier survival method and log rank test were used to estimate and compare survival. Uni- and multivariate analyses were performed in a Cox proportional regression model and alloSCT was considered as a time dependent covariate. Results: 169 patients were included (era 1=101, era 2=68). The median duration of follow up of the entire cohort was 17 months (range 0.5-148.6 months) and follow-up of surviving patients (n=70) was longer in era 1 vs. era 2 (median 88 months vs. 32 months, p&amp;lt;0.001). The median age of the entire cohort was 60 years (range 26-79 years) and it was comparable in both eras. Most patients had normal cytogenetics (era 1: 76%; era 2: 69%). NPM1 was mutated in 69/101 (68%) and 38/68 (56%) patients in eras 1 and 2 respectively. Due to lack of genetic data for era 1, we did not risk stratify based on the recent ELN classification. The rate of CR/CRi was 58/101 (57%) vs. 40/68 (59%) after induction chemotherapy and 78/101 (77%) vs. 58/67 (87%) (p=0.09) at any time in eras 1 and 2 respectively. AlloSCT was performed in 58% and 72% of patients in the two cohorts. Midostaurin was used in 82% and gilteritinib was used in 26% of era 2 patients in the second era. OS was significantly longer in era 2 (median OS 73 months vs. 11 months, HR (death) 6.2, p=0.012) (Figure). The 2-year OS rate was higher in era 2 (57%) than in era 1 (39%). In patients achieving CR/CRi, median RFS was longer in era 2 (51 vs. 16 months, p=0.43), although this was not statistically significant. In univariate Cox regression analysis the following factors were associated with improved OS: use of midostaurin (HR 0.487, 95% CI 0.304-0.779, p=0.003), diagnosis in era 2 (HR 0.583, 95% CI 0.38-0.895, p=0.014) and receipt of alloSCT (HR 0.346,) 95% CI 0.219-0.545, p&amp;lt;0.001). Other parameters including age, sex, NPM1 status and cytogenetics were not significant. In multivariate analysis including era, midostaurin and alloSCT, only the receipt of alloSCT was associated with significantly improved OS (HR 0.362, 95% CI 0.229 - 0.572, p&amp;lt;0.001) whereas use of midostaurin (HR=0.465, CI 0.207-1.042, p=0.063) and era (HR 1.12, 95% CI 0.538-2.34, p=0.76) were not significant. Conclusions: Our results show thatOS for patients with FLT3-ITD AML has improved in patients diagnosed in a more recent treatment era. Patients diagnosed after 2018 were more frequently treated with AlloSCT and FLT3-inhibitors, which may have resulted in improvements in OS. Our findings support the assignment of FLT3-ITD AML to theintermediate risk category as per the current ELN guidelines. A limitation of this study is the differences in follow-up time between eras, which may influence the event rate between the groups.

Clonal Dynamics of FLT3-ITD Positive Acute Myeloid Leukemia Patients with Relapsed/Refractory Disease Following Intensive Chemotherapy +/- Midostaurin

Introduction: Despite the wider use of midostaurin (MIDO) in combination with intensive chemotherapy (ICT) as the 1st-line treatment for FLT3-mutated acute myeloid leukemia (AML), complete remission (CR) rates are close to 60%, and relapses occur in over 40% of cases, demonstrating the ability of leukemic cells to resist and evade therapy ( Stone et al., NEJM 2017). Conventional fragment-length analyses of paired diagnosis/relapse samples have shown that FLT3-internal tandem duplications (ITDs) are retained in 80% and 50% of cases following ICT alone and MIDO+ICT respectively ( Schmalbrock et al., Blood 2021). Only limited data are available on the dynamics of FLT3-ITDs or other co-mutations in refractory patients (pts). Here, we conducted a retrospective study involving 115 pts with relapsed/refractory AML harboring FLT3-ITD at diagnosis. Materials and methods: Clonal evolution was examined in paired diagnosis/progression blood or bone marrow samples from 115 pts with FLT3-ITD+ AML treated with MIDO+ICT (n=33) or ICT alone (n=82). Among them, 21 pts had primary refractory disease (MIDO+ICT, n=8; ICT, n=13) and 94 pts relapsed after achieving CR (MIDO+ICT, n=25; ICT, n=69). FLT3-ITDs and co-mutations were screened on genomic DNA by high-throughput sequencing at both timepoints using a custom-designed panel. For accurate annotation and quantification of FLT3-ITDs from sequencing data, we used the recentlypublished FiLT3r algorithm ( Boudry et al., BMC Bioinformatics 2022). For each ITD detected, FiLT3r allelic ratio (AR) was assessed by the ratio between the mutated allele and the wild-type allele. Results: A total of 226 FLT3-ITDs were detected in 115 pts at AML diagnosis, among which 120 (53%) ITDs were found with an AR below 0.05 ( Figure 1). Among pts who achieved CR and experienced relapse (n=94), 48 had multiple FLT3-ITDs at diagnosis and 46 had a single FLT3-ITD at diagnosis. Overall, we observed a simplification of the FLT3-ITD repertoire upon relapse with the persistence of at least one initial clone in 8/12 [67%] and 24/36 [67%] pts with multiple ITDs receiving MIDO+ICT and ICT alone respectively. In relapsed pts who initially had a single FLT3-ITD clone at diagnosis, the addition of MIDO to ICT was associated with a higher rate of FLT3-ITD negativity compared to pts receiving ICT alone (6/13 [46%] vs 5/33 [15%]; P = 0.05) ( Figure 2). Interestingly, among 21 pts with primary refractory AML, we observed that FLT3-ITD mutation status became negative in 5/8 pts (62%) and 2/13 pts (15%) after induction with MIDO+ICT and ICT alone respectively. We then compared the initial characteristics between retained and lost FLT3-ITDs at AML relapse. Lost FLT3-ITDs had significantly lower AR than retained clones in both treatment groups. In order to limit the impact of sample dilution on the allele burden, we defined adjusted variant allele frequencies (VAFs) as the VAFs of FLT3-ITDs normalized to the VAFs of NPM1 mutations, whenever applicable. In so doing, we observed that adjusted VAFs of retained FLT3-ITDs increased at relapse, regardless of the treatment group (adjusted VAF, diagnosis vs relapse: 0.28 vs 0.86 and 0.88 vs 1.6 in the MIDO+ICT group and ICT alone group; P = 2.3e-03 and P = 2.4e-04). Importantly, an adjusted VAF higher than 1 was strongly suggestive of a homozygous state of FLT3-ITD. Such situation was found to be more prevalent at relapse in both treatment groups. Besides the selection of a dominant FLT3-ITD clone, other relapse-related changes including the acquisition of additional mutations will be presented. Conclusion: Our study of the clonal dynamics of AML with FLT3-ITD mutations provides insights into the mechanisms underlying therapy escape. Our data suggest that clonal interference characterized by multiple FLT3-ITD clones is associated with a greater ability to select a FLT3-ITD-positive clone at relapse in pts receiving MIDO+ICT. Although the addition of MIDO to ICT increases the probability of eradicating a single FLT3-ITD clone, FLT3-ITD+ relapses remain common following this combination, often with the selection of homozygous FLT3-ITD clones and/or the emergence of new mutations. Finally, our data in refractory situation emphasize the need to reassess mutational status at each stage of progression before implementing targeted therapy.

Treatment of Advanced Systemic Mastocytosis with Midostaurin: Practical Guidance for Optimal Therapy and Management.

Systemic mastocytosis (SM) is a rare disease with a range of clinical presentations, and the vast majority of patients have a KIT D816V mutation that results in a gain of function. The multikinase/KIT inhibitor midostaurin inhibits the D816V mutant and has a well-established role in treating advanced SM. Even if considered the standard of therapy, some open questions remain on optimizing midostaurin management in daily practice. The current review presents the opinions of a group of experts who met to discuss routine practice using midostaurin in patients with advanced SM. The efficacy and safety of midostaurin in Phase 2 trials are overviewed, followed by practical guidance for optimal therapy management and adverse events during therapy with midostaurin. Specific guidance is given for initiating therapy and evaluating response with midostaurin as general assessment and laboratory, instrumental, pathological, and molecular exams. Special consideration is given to dose interruption, reduction, and discontinuation of therapy, as well as adverse event management and supportive therapy. Patients should be informed about possible side effects and receive practical advice to avoid or limit them and antiemetic prophylaxis so that therapy with midostaurin can continue as long as clinical benefit is observed or until unacceptable toxicity occurs. Lastly, considerations on the use of midostaurin during the ongoing Covid-19 pandemic are made. The overall scope is to provide guidance that can be useful in daily practice for clinicians using midostaurin to treat patients with advanced SM.

Midostaurin in advanced systemic mastocytosis: A systematic review and meta-analysis.

e19084 Background: Midostaurin, an oral multikinase inhibitor including inhibition of KIT D816V, is approved for the treatment of advanced systemic mastocytosis (SM). Few studies have investigated the use of midostaurin in patients with advanced SM, but the data on its efficacy and safety in this population remains limited and uncertain. Therefore, we conducted this systematic review and meta-analysis to better assess the efficacy and safety of midostaurin in advanced SM. Methods: We systematically searched the following databases: PubMed/MEDLINE, Embase, and Cochrane through February 02, 2022, to include all studies that assessed the effect of midostaurin on clinical outcomes of patients with advanced SM. Our primary outcome was the overall response rate (ORR). The secondary outcomes included the rates of progressive disease (PD), stable disease (SD), and treatment discontinuation due to adverse events (AEs). All statistical analyses were performed using Open Meta Analyst (CEBM, University of Oxford). Pooled rates and corresponding 95% confidence intervals (CI) were calculated using DerSimonian-Laird/Random-effects approach. Results: Four studies (two clinical trials and two observational studies) with a total of 156 patients with advanced SM were included in the pooled analysis. The mean age of the patients was 59.6±15.8 years, and males represented 64.7% of total patients. The most common subtype of advanced SM was SM associated with hematological neoplasm (59%) followed by aggressive SM (23.1%). Three studies reported the KIT D816V mutation status, and 85.2% of patients were positive for KIT D816V mutation. The mean duration of treatment with midostaurin was 10±15.3 months. The pooled ORR was 60% (95% CI 46.5%-73.5%) over a mean follow-up duration of 41.1±38.7 months. The PD and SD rates were 12.8% (95% CI 7.6%-18%) and 10.6% (5.3%-15.9%), respectively. Treatment discontinuation due to AEs occurred in 25.6% (95% CI 18.8%-32.4%). The most common hematological grade ≥3 treatment-related AE was anemia (29%), while fatigue (7.1%) was the most common non-hematological grade ≥3 treatment-related AE. Conclusions: Our study demonstrated that midostaurin is very effective in patients with advanced SM with an acceptable safety profile. Our meta-analysis is hampered by a limited number of studies, a small sample size, and a lack of a control group. Future large-scale comparative studies are warranted to evaluate the efficacy and safety of midostaurin in these patients.

Practical tips for managing FLT3 mutated acute myeloid leukemia with midostaurin

ABSTRACT 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.

The use of midostaurin in aggressive systemic mastocytosis (ASM) with the c-KIT D816V mutation within The Emergency Access to Drug Technologies Programme

Aggressive systemic mastocytosis (ASM) is a very rare subtype of systemic mastocytosis (SM) and, together with systemic mastocytosis with an associated hematologic neoplasm (SM-AHN) and mast cell leukemia (MCL), it belongs to advanced systemic mastocytosis (AdvSM). Different strategies of systemic treatment are used in patients with AdvSM. The protocols base on the cladribine, interferon, allogeneic hematopoietic stem cell transplantation, polychemotherapy or the midostaurin — the only approved drug therapy in AdvSM. Options available in Poland — cladribine and interferon — are characterized by a non-lasting effect and, unfortunately, midostaurin still remains unreimbursed for patients. On October 5, 2018, The Polish Agency for Health Technology Assessment and Tariff System approved the midostaurin to be financed within The Emergency Access to Drug Technologies Programme in ASM with the c-KIT D816V mutation. Based on a case report, the following manuscript describes authors’ experiences with the use of midostaurin. The aim of the article is to present an overview of the current status of midostaurin in the treatment of ASM and to summarize the results of clinical trials, focusing on its effectiveness and safety. Authors, hereby, report a case of a patient diagnosed in 2000 with cutaneous mastocytosis (CM), that developed a transformation to ASM in 2015. The following lines of treatment were used: cladribine, pegylated interferon alpha, dasatinib. Significant side effects were observed after each line, without obtaining a lasting response to treatment. In July 2020, patient began a therapy with midostaurin. Afterwards, a normalization of peripheral blood count parameters together with reduction of serum tryptase level were observed, without noticing any adverse effects .

The use of midostaurin in the treatment of advanced systemic mastocytosis

Systemic mastocytosis (SM) is a rare myeloproliferative neoplasms (MPN) characterized by clonal growth and accumulation of mast cells in various organs, mainly in the skin, bone marrow, liver, spleen, and lymph nodes. In its advanced form, SM leads to impairment of their function. The clinical course is highly variable, ranging from slow to very aggressive with progressive multi-organ failure and a significant risk of leukemic transformation. Advanced SM is an indication for cytoreductive therapy. So far, various treatment strategies have been used, including cladribine (2-CDA), imatinib, interferon alpha (IFN-α), as well as classic cytostatics (hydroxycarbamide, cytarabine or fludarabine). However, none of the options mentioned provided satisfactory response rates. Currently, high hopes are related to midostaurin — a multi-pathway tyrosine kinase inhibitor The drug was approved for the treatment of advanced forms of SM by the US Food and Drug Administration (FDA) in April 2017 based on the satisfactory results of phase II clinical trial #CPKC412D2201. In this paper, we present case reports of two patients diagnosed with aggressive systemic mastocytosis (ASM) and systemic mastocytosis with an associated hematologic neoplasm (SM-AHN) treated with midostaurin as part of the early access program.

Gemtuzumab Ozogamicin Plus Midostaurin in Combination with Standard Intensive Induction Therapy in Newly Diagnosed AML: Results from a Phase-I Study

Gemtuzumab Ozogamicin Plus Midostaurin in Combination with Standard Intensive Induction Therapy in Newly Diagnosed AML: Results from a Phase-I Study

Myeloproliferative Hypereosinophilic Syndrome with Concomitant Ischemic Events

▪Background:Eosinophils are versatile reactionary cells that play a key role in the inflammatory response. Excessive proliferation and aggregation of eosinophils have been implicated in the pathogenesis of ischemic neurologic and cardiac events. We present a rare case of hypereosinophilic syndrome (HES) in a patient hospitalized for simultaneous acute cerebrovascular accident (CVA) and acute coronary syndrome.Case:A 53-year-old male with past medical history of hypertension and diabetes mellitus presented with new onset bifrontal headache, right arm numbness and apraxia, and concurrent typical angina. On physical examination, he had small non-tender raised nodules on the bilateral upper and lower limbs. MRI of the brain demonstrated multifocal infarcts in a watershed distribution. Biochemical investigation revealed rising troponins. Splenomegaly of 16.4 cm was found on CT imaging. He was admitted for management of acute CVA and non-ST segment elevation myocardial infarction (NSTEMI). Complete blood count (CBC) revealed leukocytosis (34.4 K/mcL) with an eosinophilia of 85% and an absolute eosinophil count (AEC) of 29.2 x 10 3 eosinophils/µL. Serum tryptase was 29.2 µg/L. The patient was started on a high dose steroid with subsequent resolution of his neurologic and cardiac symptoms. Due to high suspicion for HES, FISH panel and bone marrow biopsy were performed. A small focus of marrow on his biopsy showed abundant eosinophils and bland spindle cells (>15 mast cells in aggregate). FISH panel was positive for 4q12 rearrangement, consistent with a FIP1L1/PDGFRA fusion mutation. Skin biopsy of his lesions demonstrated superficial and deep inflammation with eosinophils. He was diagnosed with myeloproliferative HES with features of mastocytosis and started on imatinib.Discussion:The defining features of HES consist of eosinophilia greater than 1500/µL for greater than 6 months with evidence of eosinophil induced tissue infiltration and injury. The ability of eosinophils to induce pathologic outcomes is influenced by a variety of parameters, including the number of eosinophils present, their location, and the degree of activation. Published data suggests that neurologic and cardiac ischemic events occur in HES patients with a higher leukocyte count and AEC than what we present with in this case. Our patient meets the main lab criteria of HES and our case highlights that simultaneous clinical manifestations can occur in the absence of markedly elevated peripheral eosinophilia. As with most cases involving unexplained hypereosinophilia, a wide range of diagnostic testing was necessary. The presence of a PDGFRA fusion mutation established a clonal disorder, supporting the diagnosis of myeloproliferative HES variant. The presence of eosinophils and the lack of mast cells on skin biopsy further supports myeloproliferative HES variant rather than a true systemic mastocytosis. Despite recent advances in molecular and immunologic therapies, treatment for HES remains challenging due to the wide variety of etiological classifications necessitating targeted treatments. At the time of submission, KIT mutation analysis is pending. Identification of a KIT D816V mutation would support use of midostaurin or the recently approved avapritinib for treatment of overlap syndrome. DisclosuresNo relevant conflicts of interest to declare.

High Sensitivity Detection of FLT3-ITD Measurable Residual Disease By Deep Sequencing Prior to Hematopoietic Cell Transplant Is Highly Prognostic for Outcome in Acute Myeloid Leukemia

High Sensitivity Detection of FLT3-ITD Measurable Residual Disease By Deep Sequencing Prior to Hematopoietic Cell Transplant Is Highly Prognostic for Outcome in Acute Myeloid Leukemia

Factors Predicting Response and Resistance to Midostaurin in FLT3 Positive and FLT3 Negative AML in 483 Primary AML Patient Samples

Introduction: Midostaurin is an FDA approved, multi-target tyrosine kinase(TK) inhibitor shown to inhibit the FLT3 kinase and have therapeutic benefit in FLT3 mutated AML especially FLT3-ITD mutations (FITD+). However, midostaurin has also shown therapeutic response in select FLT3-ITD negative (FITD-) AML patients likely due to inhibitory effects on other TKs .We analyzed primary AML patient samples from our ‘Beat AML’ database to look at disease related factors, aside from FLT3 status, that may influence midostaurin drug sensitivity and affect patient outcomes.Methods: We collected peripheral blood and bone marrow samples from 483 newly diagnosed AML patients (348 FITD+, 135 FITD-), extracted mononuclear cells and plated them on a Midostaurin dose curve, without growth media or feeder cells. Metabolic viability was assessed after 72-hours and drug response was summarized with an area under curve (AUC) metric on a 0-100 scale. We annotated these samples for known chromosomal translocations and somatic mutations in leukemia-related genes and performed association-based analyses to identify genomic predictors of midostaurin drug sensitivity.Results: FLT3-ITD was predictably the strongest association with midostaurin-response, so further analysis was subsetted into FITD+ and FITD- samples (Figure A). For our analysis, we included FLT3-TKD mutant samples in the FITD- cohort as we found no significant difference between FLT3-TKD status and non-FLT3 mutated samples.Within FITD- samples, we found inv(16) Core Binding Factor AMLs demonstrated increased sensitivity to midostaurin (p < 0.05) . We investigated the frequency of c-Kit mutations in inv(16) AMLs, given Midostaurin's activity against c-Kit, but did not observe significant differences in drug response between any combination of inv(16) and c-Kit mutational status due to a relatively small sample size.(Fig B) Further, among all FITD- samples evaluated, we found mutations in KRAS and TP53 to be predictive of midostaurin resistance (p < 0.05, Fig B). This relationship was also observed through analysis of publically available cell line drug screens within the Genomics of Drug Sensitivity in Cancer (GDSC), where mutations in NRAS and TP53 suggested Midostaurin resistance.In FITD+ AML samples, we found the FLT3-ITD mutant allele fraction (MAF) to strongly correlate with the extent of Midostaurin sensitivity. FLT3-ITD MAF was significantly higher in Midostaurin-sensitive samples compared to resistant samples (p < 0.001)(Fig C). Additionally, we observed an increase in Midostaurin efficacy (p < 0.05) in FLT3-ITD positive(15;17) APL,a subset of APL with relapse rates 15-times higher than FLT3 WT APL (Breccia et. al. Haematologica 2013) (Figure C). Further, we found that neither NPM1 or FLT3-TKD status conferred additional sensitivity to Midostaurin. There was no significant difference in AUC between FLT3-ITD and NPM1 double-mutant samples and FLT3-ITD alone, and similarly no significant difference between FLT3-TKD and FLT3 WT samples.Discussion: With the approval and clinical use of Midostaurin in FLT3 positive AML patients it is important to find and validate factors influencing Midostaurin efficacy. Data from the RATIFY clinical trial has shown Midostaurin improved overall survival in patients with both high and low FLT3-ITD allelic ratios (Stone et. al. N Eng J Med 2017). We show that the ex vivo Midostaurin response is correlated with FLT3-ITD status and its MAF but not significantly with the FLT3-TKD mutation. Our data suggests that FITD+ APLs are responsive to this FLT3-inhibitor thus offering the potential of combination therapy and improved outcomes with current APL regimens.We also demonstrate that Midostaurin shows efficacy in FLT3-ITD negative patient samples, illustrating the multi-targeted nature of the inhibitor. Within these samples,inv 16 predicted Midostaurin sensitivity regardless of c-Kit mutational status. Additionally, mutations in TP53 and the Ras-pathway predict Midostaurin resistance (these mutations rarely co-occurred with FLT3-ITD in our cohort, thus limiting their impact in FLT3-ITD positive cases). Additional in vitro and clinical data is necessary to determine whether these findings should influence treatment decisions.Newer FLT3 inhibitors in clinical trials need to be characterized in a similar manner so as to efficiently target subsets of FLT3 mutated AML. [Display omitted] DisclosuresTyner:Takeda Pharmaceutical Company: Research Funding; Constellation Pharmaceuticals: Research Funding; Incyte Corporation: Research Funding; Janssen Pharmaceutica: Research Funding; Array Biopharma: Research Funding; Aptose Biosciences: Research Funding; Syros: Research Funding; AstraZeneca: Research Funding; Genentech: Research Funding; Agios Pharmaceuticals: Research Funding; Seattle Genetics: Research Funding; Gilead: Research Funding; Leap Oncology: Consultancy. Borate:Novartis, Jazz: Consultancy, Speakers Bureau.

Concomitant Use of Midostaurin with Strong CYP3A4 Inhibitors: An Analysis from the Ratify Trial

Introduction: Midostaurin is an oral multikinase inhibitor with activity in FMS-like tyrosine kinase 3 (FLT3 )-mutated acute myeloid leukemia (AML), including internal tandem duplications and tyrosine kinase domain mutations. The phase 3, double-blind, placebo-controlled, randomized RATIFY/CALGB (Alliance) 10603 trial investigated the effect of midostaurin in combination with standard chemotherapy and as single-agent maintenance therapy on outcomes in patients with newly diagnosed FLT3 -mutated AML. When added to standard chemotherapy, midostaurin improved both event-free survival (EFS) and overall survival (OS) (Stone et al, N Engl J Med. 2017 Jun 23. [Epub ahead of print]). Midostaurin is metabolized into 2 metabolites (CGP62221 and CGP52421) by cytochrome P450 3A4 (CYP3A4). We evaluated the effects of strong CYP3A4 inhibitors on midostaurin exposure, activity, and safety based on clinical data from the RATIFY trial.Methods: Patients received placebo or midostaurin 50 mg twice daily on days 8 to 21 of each 28-day induction or consolidation cycle, followed by 50 mg twice daily as a single agent on days 1 to 28 during the 12-cycle maintenance phase. Concomitant medication use was recorded for patients throughout all 3 treatment phases (induction, consolidation, and maintenance). Plasma levels of midostaurin and its metabolites were measured in a subset of 188 patients. Data on grade ≥3 adverse events (AEs) were collected at all sites; all grade 1/2 AE data were collected by sites outside the United States while only 13 prespecified grade 1/2 AEs were recorded at North American sites. The effect of CYP3A4 on efficacy was assessed using multiple endpoints including complete response, EFS, and OS.Results: Concomitant medication use was balanced between the midostaurin and placebo groups. Strong CYP3A4 inhibitors concurrently administered most frequently were the antifungal medications posaconazole and voriconazole. Strong CYP3A4 inhibitors were used in 60.8%, 45.6%, and 10.8% of patients during induction, consolidation, and maintenance, respectively.A 1.44-fold increase in midostaurin exposure (Cmin) was observed in patients receiving coadministration of strong CYP3A4 inhibitors compared with patients not receiving strong CYP3A4 inhibitors (number of patients: n=55 vs n=112, respectively). No relevant effect was observed with CGP62221 and CGP52421. Because the protocol did not include any recommendations for dose modifications when strong CYP3A4 inhibitors were administered, the median relative dose intensity of midostaurin was >94% of the intended dose in both treatment arms. There was no notable increase in midostaurin-related AEs in patients receiving strong CYP3A4 inhibitors. Exposure-safety analyses showed a slightly shorter time to occurrence of grade 3 or 4 clinically notable AEs with increasing exposure, with an overall acceptable safety profile for midostaurin. Exposure-response analyses indicated that a higher dose intensity was associated with a larger benefit to patients, namely through complete response, EFS and OS. This observation was generally not affected by demographic covariates or presence/absence of CYP3A4 perpetrators during the cycle where the PK sample was used for the analysis.Conclusions: Overall, co-administration of midostaurin with strong CYP3A4 inhibitors, without midostaurin dose adjustment, led to a balanced safety and efficacy profile. Because strong CYP3A4 inhibitors can increase the plasma concentration of midostaurin, caution is required when concomitantly prescribing these with midostaurin. Alternative medicinal products that do not strongly inhibit CYP3A4 activity should be considered. In situations in which satisfactory therapeutic alternatives do not exist, patients should be closely monitored for midostaurin-related toxicity.Support: U10CA180821, U10CA180882, U24CA196171; ClinicalTrials.gov identifier, NCT00651261. DisclosuresOuatas:Novartis: Employment. Duval:Novartis: Employment. Sinclair:Novartis: Employment. Berkowitz:Novartis: Employment.

Midostaurin Reduces Regulatory T Cell Population in Healthy and Acute Myeloid Leukemia Cells

Background: Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy characterized by the rapid growth of abnormally differentiated hematopoietic cells called blasts which accumulate in the blood to cause bone marrow failure. The only curative option available to patients with AML is intensive chemotherapy followed by allogeneic stem cell transplant (Allo-HSCT). FMS-Like Tyrosine Kinase III Internal Tandem Duplication (FLT3 -ITD), a common mutation in patients with AML, is associated with poor prognosis. Although Allo-HSCT has significantly improved the dismal outcome of patients with FLT3 -ITD positive AML, ~50% of patients relapse within two years after transplant. The recognition and elimination of leukemic clones by donor T cells or the graft vs leukemia (GvL) effect contributes significantly to the success of Allo-HSCT. FLT3 inhibitors have been extensively investigated in patients with FLT3 -ITD AML, and have demonstrated promising results in clinical trials. How FLT3 inhibitors affect T cells and whether adding these targeted therapies to Allo-HSCT will have a therapeutic benefits or drawbacks is unknown. Because T cells play a crucial role in the GvL effect, investigating therapeutic approaches to modulate the T cell populations, function, and repertoire to enhance the GvL effect is highly needed. Regulatory T cells (Treg), a subset of CD4+ T cells with suppressive functions to maintain self-tolerance, are present at a higher percentage in patients with AML, and are recognized to drive immunosurveillance evasion in leukemic cells.Here, we hypothesize that current FLT3 inhibitors affect T cell population and function either through their off-target effect on T cell signaling pathways or through induction of leukemic cell apoptosis and presentation of leukemic antigens. In this abstract we report the effect of four FLT3 inhibitors (sorafenib, midostaurin, tandutinib, and quizartenib) on T cell population.Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from freshly collected blood samples obtained from healthy donors (N=5). PBMC were stimulated with IL-2 (5ng/ml), IL-7 (10ng/ml), and treated with 1mM of one of the following FLT3 inhibitors (sorafenib, midostaurin, tandutinib, and quizartenib) for 72 hours. We analyzed T cell populations (CD4+, CD8+, and CD25+ cells) by flow cytometry. We also measured Treg marker FOXP3 mRNA expression by quantitative RT-PCR. Similarly, blood samples from patients with AML were examined (N=3). Cell viability were also assessed by alamar blue assay and by flow cytometry.Results: Healthy PBMCs treated with midostaurin had a significant decrease in CD4+CD25+ T cell population when compared with other treatment groups (N=3, 80% decrease, P=0.0006). sorafenib showed a modest decrease in CD4+CD25+ T cells (N=3, P=0.12). On the other hand, tandutinib and quizartenib did not affect CD4+CD25+ population. No effect was observed on total lymphocytes, CD3, CD8, CD4 T cell populations, when cells were treated with FLT3 inhibitors. In addition, we found that treatment with midostaurin resulted in significant decrease in relative FOXP3 mRNA expression when compared with other treatment groups (N=5, P=0.02). Viability assay confirmed that FLT3 inhibitors did not affect cell viability in healthy PBMC but they significantly decreased the viability of MV4-1 cells (a FLT3 -ITD positive AML cell line) (50-70% decrease P=0.0007). Although the percentages of T cells were very low in AML blood samples obtained at diagnosis, the observed trend was similar to that found in healthy PBMCs. CD4+CD25+ population was reduced compared to controls (N=2, 2-fold, P=0.10). Similarly, treatment of AML primary blasts with midostaurin also reduced FOXP3 mRNA expression (n=2, 50% decrease, P=0.0001)Conclusions: These results indicate that treatment with midostaurin causes a decrease in regulatory T cell population. Although the mechanism by which midostaurin reduces Tregs is not clear, our data indicates a possible off-target effects of this multi-kinase inhibitor on T cell signaling pathways. We are currently exploring the effect of midostaurin on Tregs function and repertoire. In light of the recent FDA approval of midostaurin use in patients with AML, these results highlight a novel therapeutic advantage of this drug that may be beneficial particularly in the setting of Allo-HSCT. DisclosuresNo relevant conflicts of interest to declare.

Experience with FLT3 Inhibitor Midostaurin in Newly Diagnosed Acute Myeloid Leukemia Patients

Introduction With the introduction of FLT3 inhibitors in recent years, the presence of FLT3 mutation in newly diagnosed acute myeloid leukemia (AML) patients has become more important. it was observed that the addition of Midostaurin to remission induction and consolidation chemotherapy, brought a 22% reduction in mortality risk in patients with FLT3 mutation. In the light of the above information, we aimed to share our experience regarding the use of Midostaurin in our newly diagnosed AML patients.&#x0D; Methods The data of 20 patients who were diagnosed with AML between April 2020 and November 2020 in the Hematology Department of Bursa City Hospital and who were eligible for standard remission induction therapy were evaluated retrospectively. Standard remission induction chemotherapy consisting of a combination of cytosine arabinoside (ARA-C) and an anthracycline was applied to patients. Consolidation treatment with high dose ARA-C was given to patients in remission; Midosaturin 100 mg was added to High-dose ARA-C between days 8 and 21 in patients with FLT3 mutation.&#x0D; Results: Twenty patients included in the study, 14 were men and 6 were women. There were six patients with the FLT3 mutation. Five patients with FLT3 mutation were male and one was female. The mean age of the patients is 53.8; the mean age of the patients with FLT 3 mutation was 49.8 years. Two patients with FLT 3 mutation died due to sepsis during remission induction treatment; In Four patients, complete response was obtained with remission induction therapy. Four patients had been given midostaurin with high dose ARA-C and referred for bone marrow transplantation. &#x0D; Conclusion The use of FLT3 inhibitors in combination with chemotherapeutic agents in the treatment of AML patients with FLT3 mutation is considered as a standard. However, it takes a certain amount of time for the FLT3 mutation to result. For this reason, Midostaurin treatment could be added not during remission induction but consolidation. Although our study included a limited number of patients it shows the importance of Midostaurin treatment in newly diagnosed AML patients with FLT3 mutation as real-world data.

Midostaurin in combination with chemotherapy is most effective in patients with acute myeloid leukemia presenting with high FLT3‐ITD allelic ratio who proceed to allogeneic stem cell transplantation while in first complete remission

Midostaurin, a multikinase and FLT3 inhibitor, is the first non-chemotherapy agent approved and widely adopted for the treatment of FLT3-ITD acute myeloid leukemia (AML). Yet, its role in improving survival of patients referred to allogeneic stem cell transplantation (allo-SCT) in first complete remission (CR1) needs to be defined. This multicenter study retrospectively evaluated the outcome of 119 FLT3-ITD AML patients [59 (49.6%) males and 60 females] intensively treated between 2015 and 2019 at five Israeli centers. In our cohort, allo-SCT in CR1 was widely implemented (47%) and patient stratification was based on the current allelic ratio (AR) cutoff of 0.5. Ninety-eight patients (82.3%) achieved CR1/CR with incomplete count recovery (CRi). Death during induction was reported in 7 (5.9%) patients. In multivariate analysis, midostaurin use and allo-SCT in CR1 were the most significant factors affecting overall survival (OS). Midostaurin incorporation in chemotherapy regimens significantly improved CR+CRi rates (P=.002), reduced relapse rates (P=.02), and was remarkably advantageous for high-AR patients (2-year OS 82%). In low-AR patients, the midostaurin effect was much less prominent. Our results demonstrate benefits of midostaurin incorporation in intensive chemotherapy regimens, particularly for high-AR AML patients to whom it should be offered along with allo-SCT in CR1.

Midostaurin in acute myeloid leukemia: current evidence and practical considerations in routine clinical use.

Mutation within the FMS-like tyrosine kinase 3 (FLT3) gene are one of the most frequent genetic alterations in acute myeloid leukemia. A high mutation fraction of FLT3-ITD molecules on the surface of leukemia cells is associated with short remissions and overall adverse outcomes in AML. In this article we summarize the clinical trial data of midostaurin - one of the FLT3 inhibitors. We review its use in various combinations both in relapsed/refractory acute myeloid leukemia as well as in the newly diagnosed patients and recollect the evidence of its use as maintenance therapy post allogenic stem cell transplantation. We enumerate the practical issues faced in the use of midostaurin like antifungal prophylaxis, dosage of concomitant chemotherapy agents as well as available data on sequencing of the FLT3 inhibitors. Lastly, we provide our perspective of the future directions for FLT3 inhibition especially midostaurin, the underlying resistance mechanisms and the need for standardization of the FLT3 tests.

Treatment practice and outcomes in FLT3-mutant acute myeloid leukemia in the pre-midostaurin era: a real-world experience from Australian tertiary hospitals

Recent regulatory approval of midostaurin, a FLT3 targeting small molecular inhibitor, will likely lead to increased use of midostaurin in combination with intensive chemotherapy for patients with FLT3-mutant AML. Translation of clinical trial results into everyday practice has its challenges. This study compared the relevance of the trial population and practices studied in the midostaurin registration study (RATIFY) with real-world practice in terms of patient factors, chemotherapy, mutation-specific frequencies and clinical outcomes among patients with FLT3-mutant AML in the pre-midostaurin era (2010–2015) in Australia. We observed substantial diversity of chemotherapy regimens used in the community and limitations of the generalizability of eligibility criteria used in RATIFY (such as age and hyperleukocytosis). This study provides real-world historical data that may be used for comparison with future trial cohorts incorporating FLT3 inhibitors into the management of FLT3-mutant AML and highlights the inherent difficulties in translating clinical trial data into routine practice.

Real-World Utilization of Midostaurin Among Patients with Systemic Mastocytosis (SM)

Introduction: Systemic Mastocytosis (SM) is a rare neoplasm of myeloid origin characterized by an accumulation of abnormal mast cells in the bone marrow, liver, spleen, and skin and has a molecular signature of the KITD816V mutation, detectable in &gt;90% of patients. Clinical findings include cytopenias, liver-function abnormalities, hypoalbuminemia, weight loss, ascites, and osteolytic bone lesions due to infiltration of various organs by the malignant mast cells. The indolent and smoldering subtypes of SM can have a long natural history but aggressive systemic mastocytosis (aSM), SM with associated hematological neoplasm (SMHN), and mast cell leukemia (MCL) subtypes are associated with poor prognosis at a median survival of 3.5 years, 2 years and 6 months respectively. In April 2017, the FDA approved midostaurin, a multitargeted kinase inhibitor for the treatment of adults with aSM, SMHN and MCL at a dose of 100mg twice daily based on achievement of response rate endpoint noted in an open label trial of midostaurin (Gotlib et al, NEJM 2016). Pre-midostaurin, the treatment options for aSM, SMHN and MCL were imatinib, cladribine, interferon or allogeneic stem cell transplant (ASCT). The objective of this retrospective study was to assess the uptake and utilization of midostaurin in patients with aSM, SMHN and MCL. Methods: Patients with at least 1 claim for midostaurin (index date) between April 1, 2017 and October 31, 2018 and who had at least 1 claim with a diagnosis of SM (ICD 10 code C96.2x or C94.3x) in the 6-month pre-index period were identified from Symphony Health's Integrated Dataverse (IDV), a large US claims database containing linked longitudinal prescription, medical, and hospital claims. The IDV contains claims for 280 million active unique patients representing over 73% of specialty prescriptions, 58% of medical claims, and 30% of hospital claims volume in the US. Patients included in the study cohort had a 6-month pre-index period with no claims with a diagnosis of SM, were at least 18 years old at initiation of midostaurin, and no evidence of participation in a clinical trial. Patient characteristics and treatment patterns were summarized using descriptive statistics. Median and 95% confidence interval (CI) for duration of midostaurin were calculated using Kaplan-Meier estimates. Results: Of the 38 patients with SM treated with midostaurin, 33 had a diagnosis of aSM and 5 had a diagnosis of MCL. The majority were female (61%) with a median age of 63 years (range 27-79) at diagnosis; 42% of these patients were 65 years or older (Table). The majority (66%) of patients had commercial insurance, and patients resided in all 4 US regions (34% South, 34% West, 18% Midwest, 11% Northeast). Nearly two-thirds (63%) of midostaurin use was in the first line setting, 32% was given in second line, and 5% was given in third line. Among the 14 patients with therapy prior to midostaurin, cladribine was most common (n=4, 29%), followed by hydroxyurea, interferon alfa-2b, brentuximab vedotin, and others (each n=2, 14%). Over two-thirds (68%) had an average daily dose of 200mg on the first fill, 5% treated at 100mg daily, and 26% with average daily doses &lt;100mg. Two thirds (22 of 33) patients with aSM and 4 of 5 with MCL were prescribed the 200mg/day recommended dose. With a median follow-up of 13.4 months from midostaurin initiation, the median duration of midostaurin 2.4 months (95% CI 1.1-4.6). Conclusions: In this retrospective claims based study, there is evidence of early uptake of midostaurin use in SM. Midostaurin was used in the first line setting in the majority of patients. The median duration of midostaurin treatment was short at 2.4 months especially when compared to a median treatment duration of 11.5 months in the pivotal trial. It is noteworthy that almost a third of patients were started on a lower than recommended dose which may compromise efficacy. The relatively short follow up may be another reason for the observed duration of response. Potential barriers to the appropriate use of midostaurin in SM such as lack of awareness, access, cost or delay in diagnosis due to its rarity will need further exploration. While the current claims-based dataset does not provide us the information, early, accurate diagnosis of SM is essential to timely utilization of midostaurin in the real-world setting. Further research and education may be needed to optimize the use of novel therapeutics in such orphan diseases. Disclosures Gajra: Cardinal Health: Employment. Klink:Cardinal Health: Employment. Chopra:Cardinal Health: Employment. Feinberg:Cardinal Health: Employment.

Real-World Utilization of Midostaurin Among Patients with Acute Myeloid Leukemia (AML)

Introduction: Acute Myeloid Leukemia (AML) is a biologically heterogeneous disease with poor outcomes despite aggressive induction chemotherapy (IC). Cytogenetics and mutational profile are used to inform subgroups of patients who are at high risk of relapse. Mutations in the fms-related tyrosine kinase 3 gene (FLT3) are detected in 30% of adults with newly diagnosed AML. The predominant (75%) FLT3 mutation, is an internal tandem duplication mutation (FLT3-ITD), which confers poor prognosis due to a high relapse rate. The addition of the multitargeted kinase inhibitor midostaurin to standard IC significantly prolonged overall survival (hazard ratio for death 0.77, p=0.016) among patients with AML and a FLT3 mutation. Midostaurin was approved by the United States Food and Drug Administration (FDA) in April 2017 for the treatment of adult patients with newly diagnosed FLT3+ AML, as detected by an FDA-approved test, in combination with standard cytarabine and daunorubicin IC and cytarabine consolidation. The recommended dose of midostaurin in AML is 50 mg twice daily with food on days 8 to 21 of each cycle of induction and consolidation chemotherapy followed by 50 mg with food as a single agent for up to 12 months. The objective of this study was to evaluate the utilization of midostaurin in AML in the real-world setting in the first year after its US approval and marketing. Methods: Patients with at least 1 claim for midostaurin (index date) between April 1, 2017 and October 31, 2018 and who had at least 1 claim with a diagnosis of AML in the 6-month pre-index period were identified from Symphony Health's Integrated Dataverse (IDV), a large US claims database containing linked longitudinal prescription, medical, and hospital claims. The IDV contains claims for 280 million active unique patients representing over 73% of specialty prescriptions, 58% of medical claims, and 30% of hospital claims volume in the US. Patients included in the study cohort had a 6-month pre-index period with no claims with a diagnosis of AML, were at least 18 years old at initiation of midostaurin, and no evidence of participation in a clinical trial. Patient characteristics and treatment patterns were summarized using descriptive statistics. Median and 95% confidence interval (CI) for duration of midostaurin were calculated using Kaplan-Meier estimates. Results: There were 708 patients with AML treated with midostaurin who met all study selection criteria. Median age at midostaurin initiation was 60 years (range 20-80), and 49% of patients were male. The majority (61%) had commercial insurance, and patients resided in all 4 US regions (43% West, 22% South, 18% Northeast, 16% Midwest). Midostaurin was given as first line therapy in 583 (82%) patients, as second line in 95 (13%) patients, and as third line or later in 30 (4%) patients (see Table). Among the 95 patients who received midostaurin as second line therapy, hydroxyurea monotherapy (n=24, 25%) and sorafenib monotherapy (n=23, 24%) were most common first line therapies. With a median follow-up of 5.9 months from initiation of midostaurin, the median duration of midostaurin treatment was 2.3 months (95% CI 1.9-2.6). Over half (51%) had an average daily dose of 100mg on their first fill, 25% had 50mg, 9% had 67mg, 5% had 25mg, and 10% had other doses. Conclusions: In this retrospective claims-based study, there is evidence of early uptake of midostaurin use in AML. However, majority of patients receive midostaurin as a single agent contrary to the approved schedule of initiating midostaurin concurrently with IC and with consolidation cytarabine. The median duration of midostaurin treatment was short at 2.3 months given that the recommendation is to continue it for 12 months after IC. Almost half the patients are started at a dose that is lower than the recommended dose, which may impact efficacy. Potential limitations of this dataset include a relatively short period of follow-up, retrospective design and low uptake post-marketing as some patients may have completed IC or missing data from midostaurin administered in the hospital. Barriers to the appropriate use of midostaurin in AML, if any, will need further exploration. Universal and timely testing for the FLT3 mutation is the essential first step to allow for including midostaurin as a part of IC for the appropriate utilization of this agent in FLT3 + AML. Disclosures Gajra: Cardinal Health: Employment. Klink:Cardinal Health: Employment. Kish:Cardinal Health: Employment. Chopra:Cardinal Health: Employment. Feinberg:Cardinal Health: Employment.