Phase 1 study of the histone deacetylase inhibitor entinostat plus clofarabine for poor-risk Philadelphia chromosome-negative (newly diagnosed older adults or adults with relapsed refractory disease) acute lymphoblastic leukemia or biphenotypic leukemia

PURPOSE

Despite advances in immunotherapies, the prognosis for adults with Philadelphia chromosome-negative, newly diagnosed (ND) or relapsed/refractory (R/R) acute lymphoblastic leukemia/acute biphenotypic leukemia (ALL/ABL) remains poor. The benzamide derivative entinostat inhibits histone deacetylase and induces histone hyperacetylation. The purine nucleoside analogue clofarabine is FDA-approved for R/R ALL in children 1-21 years of age. Low doses of clofarabine have been reported to induce DNA hypomethylation. We conducted a phase 1 study of low dose clofarabine with escalating doses of entinostat in adults with ND or R/R ALL/ABL.

EXPERIMENTAL DESIGN

Adults ≥60 years with ND ALL/ABL or ≥21 years with R/R ALL/ABL received repeated cycles every 3 weeks of entinostat (4 mg, 6 mg or 8 mg orally days 1 and 8) and clofarabine (10 mg/m²/day IV for 5 days, days 3-7) (Arm A). Adults aged 40-59 years with ND ALL/ABL or age ≥21 years in first relapse received entinostat and clofarabine prior to traditional chemotherapy on day 11 (Arm B). Changes in DNA damage, global protein lysine acetylation, myeloid-derived suppressor cells and monocytes were measured in PBMCs before and during therapy.

RESULTS

Twenty-eight patients were treated at three entinostat dose levels with the maximum administered dose being entinostat 8 mg. The regimen was well tolerated with infectious and metabolic derangements more common in the older population versus the younger cohort. There was no severe hyperglycemia and no peripheral neuropathy in this small study. There were 2 deaths (1 sepsis, 1 intracranial bleed). Overall response rate was 32 %; it was 50 % for ND ALL/ABL. Entinostat increased global protein acetylation and inhibited immunosuppressive monocyte subpopulations, while clofarabine induced DNA damage in all cell subsets examined.

CONCLUSION

Entinostat plus clofarabine appears to be tolerable and active in older adults with ND ALL/ABL, but less active in R/R patients. Further evaluation of this regimen in ND ALL/ABL appears warranted.

Characteristics and outcome of patients with core-binding factor acute myeloid leukemia and FLT3-ITD: results from an international collaborative study

The aim of this study was to evaluate the prognostic impact of FLT3-ITD in core-binding factor acute myeloid leukemia (CBFAML) in an international, multicenter survey of 97 patients of whom 52% had t(8;21)(q22;q22) and 48% had inv(16)(p13q22)/t(16;16)(p13;q22). The median age of the patients was 53 years (range, 19-81). Complete remission after anthracycline-based induction (n=86) and non-intensive therapy (n=11) was achieved in 97% and 36% of the patients, respectively. The median follow-up was 4.43 years (95% confidence interval [95% CI]: 3.35-7.39 years). The median survival after intensive and non-intensive treatment was not reached and 0.96 years, respectively. Among intensively treated patients, inv(16) with trisomy 22 (n=11) was associated with a favorable 4-year relapse-free survival rate of 80% (95% CI: 59-100%) as compared to 38% (95% CI: 27-54%; P=0.02) in all other patients with CBFAML/ FLT3-ITD (n=75). Overall, 24 patients underwent allogeneic hematopoietic cell transplantation (HCT), 12 in first complete remission and 12 after relapse. Allogeneic HCT in first complete remission was not beneficial (P=0.60); however, allogeneic HCT seemed to improve median survival in relapsed patients compared to that of patients treated with chemotherapy (not reached vs. 0.6 years, respectively; P=0.002). Excluding patients with inv(16) with trisomy 22, our data indicate that compathe outcome of CBF-AML patients with FLT3-ITD may be inferior to that of patients without FLT3-ITD (based on previously published data), suggesting that prognostically CBF-AML patients with FLT3-ITD should not be classified as favorable-risk. FLT3-inhibitors may improve the outcome of these patients.

Updates on targeted therapies for acute myeloid leukaemia

In the past few years research in the underlying pathogenic mechanisms of acute myeloid leukaemia (AML) has led to remarkable advances in our understanding of the disease. Cytogenetic and molecular aberrations are the most important factors in determining response to chemotherapy as well as long-term outcome, but beyond prognostication are potential therapeutic targets. Our increased understanding of the pathogenesis of AML facilitated by next-generation sequencing has spurred the development of new compounds in the treatment of AML, particularly the creation of small molecules that target the disease on a molecular level. Many of the hopeful predictions outlined in our AML review of 2018 are now therapeutic realities: gemtuzumab ozogamicin, venetoclax, FLT3 inhibitors (midostaurin, gilteritinib), IDH inhibitors (ivosidenib, enasidenib), CPX-351, glasdegib, oral decitabine, and oral azacitidine. Others may soon be (quizartinib, APR246 magrolimab, menin inhibitors). The wealth of positive data allows reconsideration of what might soon be new standards of care in younger and older patients with AML. In this review we give an overview of recently approved therapies in AML and address present and future research directions.

Arsenic trioxide dose capping to decrease toxicity in the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) combination therapy yields high complete remission and disease-free survival rates in acute promyelocytic leukemia (APL). ATO is dosed on actual body weight and high ATO doses in overweight patients may contribute to increased toxicity. We performed a retrospective, two-center study comparing toxicities in patients who received the Lo-Coco et al ATRA/ATO regimen with capped ATO, ≤10 mg/dose, and non-capped ATO, >10 mg/dose. A total of 44 patients were included; 15 received doses ≤10 mg and 29 received >10 mg. During induction, there was no difference in the incidence of grade ≥3 hepatotoxicity, grade ≥3 QTc prolongation, neurotoxicity, and cardiac toxicity between groups. In consolidation, patients receiving >10 mg/dose experienced a greater incidence of neurotoxicity (66.7% vs 22.2%; p = 0.046). Capping doses saved $24634.37/patient and reduced waste of partially-used vials. At a median follow-up of 27 months, no disease relapses occurred in either group. This represents an opportunity to improve the safety profile of this highly effective regimen.

Differentiation syndrome with lower-intensity treatments for acute myeloid leukemia

Differentiation Syndrome (DS) has been identified in a subset of patients undergoing treatment with novel classes of differentiating therapies for acute myeloid leukemia (AML) such as IDH and FLT3 inhibitors. While DS is a well-known treatment-related complication in acute promyelocytic leukemia (APL), efforts are still ongoing to standardize diagnostic and treatment parameters for DS in AML. Though the rates of incidence vary, many of the signs and symptoms of DS are common between APL and AML. So, DS can lead to fatal complications in AML, but prompt management is usually effective and rarely necessitates interruption or discontinuation of AML therapy.

Follow-up of patients with FLT3-mutated R/R AML in the phase 3 ADMIRAL trial

7013

Background: The phase 3 ADMIRAL trial demonstrated the superiority of gilteritinib to salvage chemotherapy (SC) in patients (pts) with FLT3-mutated ( FLT3mut+) R/R AML. Aim/Objective: A follow-up of ADMIRAL assessed long-term survivors, transplant (HSCT) outcomes. and gilteritinib safety beyond 1 year. Methods: A data cut was performed on September 20, 2020—2 years after the primary analysis. Patients who were alive without relapse, pts who underwent HSCT, and adverse events of interest (AEIs) in Years 1 (≤12 months) and 2 ( > 12 months) of gilteritinib therapy were evaluated. Results: As of September 20, 2020, 17% (n = 63/371) of pts in the intention-to-treat (ITT) population were alive (gilteritinib, n = 49; SC, n = 14); 16 pts assigned to gilteritinib remained on treatment. After a median follow-up of 37.1 months, 26 of the 49 pts in the gilteritinib arm who were alive were also without relapse; 18 of these 26 pts underwent HSCT, with 16 receiving post-HSCT gilteritinib maintenance therapy. Nineteen of the 26 pts in the gilteritinib arm without relapse continued gilteritinib beyond 1 year and remained in CR. Of the 371 ITT pts, 83 (22%) underwent HSCT during the study (gilteritinib, n = 64; SC, n = 19). Pre-HSCT CRc rates were similar across arms (gilteritinib: n = 40/64; 63%; SC: n = 11/19; 58%); 10 of 11 pts preselected for low-intensity SC achieved pre-HSCT CRc (gilteritinib, n = 9; SC, n = 1). Forty of 64 (63%) transplanted pts in the gilteritinib arm received post-HSCT gilteritinib maintenance after achieving pre-HSCT CRc; the 24-month relapse rate in pts who resumed gilteritinib after pre-HSCT CRc was 19%. Post-HSCT treatment with chemotherapy or other tyrosine kinase inhibitors was administered in 26 pts who received gilteritinib before transplantation. Cumulative 24-month relapse rates in gilteritinib-treated pts who achieved pre-HSCT CR and CRc were 20% and 45%, respectively. Median post-HSCT overall survival (landmarked to HSCT date), was similar across arms (gilteritinib, 16.1 months; SC, 15.3 months; HR = 1.076; 95% CI: 0.536, 2.160). Overall, 10.2% (n = 25/246) had ≥24 months of gilteritinib exposure. Most common AEIs during Years 1 and 2 of gilteritinib therapy were elevated ALT/AST levels. Incidences of all AEIs declined in Year 2. Cardiac AEIs in Year 2 were nonfatal cardiorespiratory arrest (n = 1) and ventricular tachycardia (n = 1). One case of differentiation syndrome and cutaneous squamous cell carcinoma occurred in Years 1 and 2, respectively. Conclusions: A high proportion of gilteritinib-treated R/R FLT3mut+ AML pts who were alive without relapse had received HSCT followed by gilteritinib maintenance. Among all transplanted pts in ADMIRAL, pre-HSCT remission rates and post-HSCT survival were similar across arms. Post-HSCT gilteritinib maintenance may relate to the low post-HSCT relapse rate in the gilteritinib arm. The safety profile of gilteritinib is stable at 2 years with no new or significant safety signals. Clinical trial information: NCT02421939.

Phase 1 first-in-human study of irreversible FLT3 inhibitor FF-10101-01 in relapsed or refractory acute myeloid leukemia

7008

Background: FF-10101-01 is a selective and irreversible FMS-like tyrosine kinase 3 (FLT3) inhibitor with potent in vitro activity against FLT3-mutated AML. FF-10101-01 is highly active against FLT3 internal tandem duplication (ITD) mutations associated with high relapse and low survival/remission rates, as well as resistance-conferring D835 and F691 tyrosine kinase domain (TKD) and non-canonical FLT3 activating mutations. Here we report on a Phase 1 dose escalation trial examining the safety, efficacy, pharmacokinetics, and pharmacodynamics of FF-10101-01 in patients (pts) with relapsed/refractory primary or secondary AML. Methods: To determine the recommended Phase 2 dose, pts with or without a FLT3 mutation received FF-10101-01 orally once (QD) or twice (BID) daily until unacceptable toxicity was observed or pts had no further clinical benefit (1 cycle = 28 days). Composite complete remission (CRc) and partial remission (PR) rates were assessed. Inhibition of FLT3 phosphorylation was evaluated using a plasma inhibitory activity assay and was correlated with associated FF-10101-01 exposure. Results: Fifty-two pts [median age 61 (range, 21-84); 52% female; FLT3: ITD [22 (42%)], TKD [5 (10%)], ITD+TKD [1 (2%)], Wt [24 (46%)] received continuous dosing of FF-10101-01 at 10 - 225 mg QD or 50 - 100 mg BID. Median number of prior therapies was 3 (range, 0-6) and the majority [23/28 (82%)] of pts with known FLT3 mutations had received prior FLT3 inhibitors. The median duration on study was 5.7 (range, 0.1-36) weeks. FF-10101-01 was generally well-tolerated up to total daily doses of 150 mg. The most common treatment related adverse events included nausea [n = 18 (35%)] diarrhea [14 (27%), 2 Grade (Gr) 3/4], elevations in creatine kinase [CK; 14 (27%), 4 Gr 3/4], vomiting [10 (19%)] and increased AST [10 (19%), 2 Gr 3]. Grade 3/4 differentiation syndrome (n = 4, 8%) was observed at 75 - 150 mg/day. Dose-limiting cardiac toxicity (heart failure with reduced ejection fraction; Gr 3 increased troponin/CK) was observed at total daily doses ≥200 mg. The CRc rate was 13% (4/30 pts evaluable for response): 1 CR at 75 mg BID (FLT3-ITD); 1 CRp at 100 mg BID (Wt-FLT3); and 2 CRi’s at 50 mg BID, one that previously progressed on gilteritinib. The median time to overall response was ̃13.3 weeks. Four pts achieved a PR (≥50% decrease in BM blasts to 5 - 25% abnormal cells) at total daily doses of 50 - 150 mg; 2 had ITD mutations, and all had received prior FLT3 kinase inhibitors. At ≥75 mg BID, trough plasma concentrations were > 90 ng/ml and associated with > 90% p-FLT3 inhibition maintained over the dosing interval. Conclusions: The FF-10101-01 FLT3 inhibitor has shown activity in pts with refractory/relapsed AML, including those with activating FLT3-ITD mutations resistant to gilteritinib and other FLT3 kinase inhibitors. Doses of 50-75 mg BID were well tolerated and resulted in sustained FLT3 inhibition. Clinical trial information: NCT03194685.

Preliminary results of V-FAST, a phase 1b master trial to investigate CPX-351 combined with targeted agents in newly diagnosed AML

7026

Background: CPX-351 (US: Vyxeos; EU: Vyxeos Liposomal), a dual-drug liposomal encapsulation of daunorubicin and cytarabine in a synergistic 1:5 molar drug ratio, is approved by the US FDA and EMA for adults with newly diagnosed t-AML or AML with myelodysplasia-related changes. Preclinical data suggest CPX-351 may exert synergistic activity when combined with agents such as the BCL-2 inhibitor venetoclax (VEN) or FLT3 inhibitor midostaurin (MIDO). Methods: V-FAST (Vyxeos – First Phase Assessment With Targeted Agents) is an open-label, multicenter, phase 1b master trial (NCT04075747) to evaluate safety and establish the recommended phase 2 dose (RP2D) of CPX-351 combined with targeted agents in patients (pts) aged 18-75 y with untreated AML who are fit for intensive chemotherapy. The study includes a dose-exploration phase (3+3 design) and subsequent expansion phase. Pts received CPX-351 (dose level 1 for first induction [DL1]: 100 units/m2 on Days 1, 3, and 5) plus VEN (Arm A; DL1: 400 mg on Days 1-14), MIDO (Arm B; DL1: 50 mg BID on Days 8-21), or the IDH2 inhibitor enasidenib ([ENA] Arm C; DL1: 100 mg on Days 8-28) based on mutation testing. Results: Among 21 pts with available data enrolled by 11/06/20 (24 pts enrolled total; data cut-off: 01/19/21), the median age was 54 y (range: 35, 69). In Arm A (n = 17), 11 (65%) pts had de novo AML, 5 (29%) had an antecedent hematologic disorder (2 [12%] had myelofibrosis), and 2 (12%) had t-AML; 12 (71%) had adverse-risk AML; and 6 (35%) had mutated TP53. In Arms B (n = 3) and C (n = 1), all pts had intermediate-risk de novo AML. DL1 was the RP2D in Arms A and B; the RP2D in Arm C is still under investigation. In Arm A, 1/6 pts in the dose-exploration phase had 2 dose-limiting toxicities (DLTs) of grade 4 neutropenia and thrombocytopenia that extended beyond 49 days; no DLTs have occurred for Arms B and C. The combinations exhibited manageable safety profiles (Table). Of pts with available response data, complete remission (CR) or CR with incomplete platelet or neutrophil recovery was achieved by 6/14 (43%) pts in Arm A, including 4 (29%) with CR. All pts in Arms B and C achieved CR. Conclusions: These preliminary results suggest CPX-351 can be combined with VEN and MIDO with manageable toxicities in newly diagnosed AML pts, with DL1 determined to be the RP2D. The study is ongoing and actively enrolling pts; updated results will be presented at the meeting. Clinical trial information: NCT04075747. [Table: see text]

Deep learning for diagnosis of acute promyelocytic leukemia via recognition of genomically imprinted morphologic features

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML), classified by a translocation between chromosomes 15 and 17 [t(15;17)], that is considered a true oncologic emergency though appropriate therapy is considered curative. Therapy is often initiated on clinical suspicion, informed by both clinical presentation as well as direct visualization of the peripheral smear. We hypothesized that genomic imprinting of morphologic features learned by deep learning pattern recognition would have greater discriminatory power and consistency compared to humans, thereby facilitating identification of t(15;17) positive APL. By applying both cell-level and patient-level classification linked to t(15;17) PML/RARA ground-truth, we demonstrate that deep learning is capable of distinguishing APL in both discovery and prospective independent cohort of patients. Furthermore, we extract learned information from the trained network to identify previously undescribed morphological features of APL. The deep learning method we describe herein potentially allows a rapid, explainable, and accurate physician-aid for diagnosing APL at the time of presentation in any resource-poor or -rich medical setting given the universally available peripheral smear.

Single-cell DNA sequencing reveals complex mechanisms of resistance to quizartinib

Single-cell sequencing exposes previously unmeasurable complexity of tumor heterogeneity and clonal evolution on quizartinib. Single-cell sequencing reveals on- and off-target mechanisms of resistance to quizartinib, which can preexist therapy.

Characteristics and outcome of patients with acute myeloid leukaemia and t(8;16)(p11;p13): results from an International Collaborative Study

In acute myeloid leukaemia (AML) t(8;16)(p11;p13)/MYST3-CREBBP is a very rare abnormality. Previous small series suggested poor outcome. We report on 59 patients with t(8;16) within an international, collaborative study. Median age was 52 (range: 16-75) years. AML was de novo in 58%, therapy-related (t-AML) in 37% and secondary after myelodysplastic syndrome (s-AML) in 5%. Cytogenetics revealed a complex karyotype in 43%. Besides MYST3-CREBBP, whole-genome sequencing on a subset of 10 patients revealed recurrent mutations in ASXL1, BRD3, FLT3, MLH1, POLG, TP53, SAMD4B (n = 3, each), EYS, KRTAP9-1 SPTBN5 (n = 4, each), RUNX1 and TET2 (n = 2, each). Complete remission after intensive chemotherapy was achieved in 84%. Median follow-up was 5·48 years; five-year survival rate was 17%. Patients with s-/t-AML (P = 0·01) and those with complex karyotype (P = 0·04) had an inferior prognosis. Allogeneic haematopoietic cell transplantation (allo-HCT) was performed in 21 (36%) patients, including 15 in first complete remission (CR1). Allo-HCT in CR1 significantly improved survival (P = 0·04); multivariable analysis revealed that allo-HCT in CR1 was effective in de novo AML but not in patients with s-AML/t-AML and less in patients exhibiting a complex karyotype. In summary, outcomes of patients with t(8;16) are dismal with chemotherapy, and may be substantially improved with allo-HCT performed in CR1.

Increased body mass index is a risk factor for acute promyelocytic leukemia

Introduction

Obesity has become increasingly prevalent worldwide and is a risk factor for many malignancies. We studied the correlation between body mass index (BMI) and the incidence of acute promyelocytic leukemia (APL), non‐APL acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and control hospitalized patients without leukemia in the same community.

Methods

Multicenter, retrospective analysis of 71 196 patients: APL (n = 200), AML (n = 437), ALL (n = 103), nonleukemia hospitalized (n = 70 456) admitted to University of Maryland and Johns Hopkins Cancer Centers, and University of Maryland Medical Center.

Results

Patients with APL had a significantly higher unadjusted mean and median BMI (32.5 and 30.3 kg/m²) than those with AML (28.3 and 27.1 kg/m²), ALL (29.3 and 27.7 kg/m²), and others (29.3 and 27.7 kg/m²) (P < .001). Log‐transformed BMI multivariable models demonstrated that APL patients had a significantly higher adjusted mean BMI by 3.7 kg/m² (P < .001) or approximately 10% (P < .01) compared to the other groups, when controlled for sex, race, and age.

Conclusions

This study confirms that when controlled for sex, age, and race there is an independent association of higher BMI among patients with APL compared to patients with ALL, AML, and hospitalized individuals without leukemia in the same community.

The impact of FLT3 mutation clearance and treatment response after gilteritinib therapy on overall survival in patients with FLT3 mutation-positive relapsed/refractory acute myeloid leukemia

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.

The Changing Landscape of Treatment in Acute Myeloid Leukemia

The treatment of acute myeloid leukemia is evolving, with increased understanding of molecular pathogenesis allowing better risk stratification and development of new therapies. Tests to identify and drugs to target specific molecular abnormalities are improving remission rates and prolonging survival in patients with high-risk disease. Allogeneic hematopoietic stem cell transplantation remains an important curative therapy, with advances in donor availability and approaches to reduce transplant-related mortality making it applicable in many more patients. Considerations in identifying appropriate patients for targeted therapy and transplantation are presented.

Clinical Outcomes in Patients with FLT3-ITD-Mutated Relapsed/Refractory Acute Myelogenous Leukemia Undergoing Hematopoietic Stem Cell Transplantation after Quizartinib or Salvage Chemotherapy in the QuANTUM-R Trial

Despite the substantial clinical activity of fms-related tyrosine kinase 3 (FLT3) inhibitors in relapsed or refractory (R/R) FLT3-ITD‒positive acute myelogenous leukemia (AML), durable remissions and prolonged survival in this population require allogeneic hematopoietic stem cell transplantation (allo-HSCT). Quizartinib, a once-daily oral, highly potent, and selective FLT3 inhibitor, significantly prolonged overall survival (OS) and improved clinical benefit compared with salvage chemotherapy (median OS, 6.2 months versus 4.7 months; hazard ratio [HR], .76; 95% confidence interval [CI], .58 to .98; P = .018; composite complete remission [CRc] rate, 48% versus 27%; median duration of CRc, 2.8 months versus 1.2 months; mortality rate, .8% versus 14% by day 30, 7% versus 24% by day 60) in patients with R/R FLT3-ITD AML in the phase 3 QuANTUM-R trial. In this post hoc analysis, we described the characteristics of and clinical outcomes in patients who underwent on-study HSCT in QuANTUM-R at the investigator's discretion and institutional practices. Of 367 randomized patients, 78 (32%) in the quizartinib arm and 14 (11%) in the salvage chemotherapy arm underwent on-study allo-HSCT without any intervening therapy for AML after quizartinib or study-specified salvage chemotherapy. Pooled data of patients from both treatment arms showed a longer median overall survival (OS) in transplant recipients versus those treated without allo-HSCT (12.2 months versus 4.4 months; HR, .315; 95% CI, .233 to .427). Pooled data also showed a longer median OS in patients with a last recorded response of CRc before allo-HSCT versus patients without a CRc (20.1 months versus 8.8 months; HR, .506; 95% CI, .296 to .864). By treatment arm, the median OS was 25.1 months with quizartinib and 20.1 months with salvage chemotherapy in patients with a last recorded response of CRc before allo-HSCT. Forty-eight patients in the quizartinib arm continued quizartinib treatment after allo-HSCT. In the 31 patients with a last recorded response of CRc before allo-HSCT who continued quizartinib after allo-HSCT, the median OS was 27.1 months. Continuation of quizartinib after allo-HSCT was tolerable, and no new safety signals were identified. These results suggest that post-transplantation survival following salvage chemotherapy and quizartinib treatment are similar. However, quizartinib response occurs more frequently than with salvage chemotherapy, potentially allowing more patients to undergo transplantation and achieve durable clinical benefit. In addition, post-transplant quizartinib was found to be tolerable and may be associated with prolonged survival in some patients, highlighting its potential value in the management of patients with FLT3-ITD R/R AML.

Abstract 784: Effect of co-mutations and FLT3-ITD variant allele frequency (VAF) on response to quizartinib or salvage chemotherapy (SC) in relapsed/refractory (R/R) acute myeloid leukemia (AML)

Introduction: We evaluated the impact of baseline (BL) co-mutations and FLT3-ITD VAF on overall survival (OS) and response (composite complete remission [CRc]) to quizartinib and SC in the phase III QuANTUM-R trial.

Methods: We analyzed 37 recurrently mutated genes in AML in BL samples from 304 patients (pts) (83% of ITT population) with R/R FLT3-ITD-positive AML using next-generation sequencing and a customized Archer® Core Myeloid panel. Positive mutation status was defined as ≥1 mutation detected in the gene region using a VAF cutoff of 2.7%. FLT3-ITD VAF was measured by the Navigate BioPharma FLT3 Mutation Assay (polymerase chain reaction-based, VAF cutoff of 3%). Low and high FLT3-ITD VAF were defined as ≤25% and &gt;25%, respectively.

Results: In addition to FLT3-ITD, the prevalence of key BL co-mutations were 59.9% for DNMT3Amut and 55.3% for NPM1mut. Pts with DNMT3Amut treated with quizartinib had significantly longer OS vs SC (6.3 and 5.4 mos, respectively; hazard ratio [HR], 0.652), p&lt;.05). Pts with NPM1mut treated with quizartinib had a higher CRc rate than with SC, but similar OS (5.1 vs 4.7 mos, respectively; HR, 0.954, p=.82). Pts with NPM1wt/DNMT3Amut treated with quizartinib had the highest CRc rate and longest median OS (9.0 and 4.5 mos, respectively; HR, 0.239, p=.003). OS benefit with quizartinib relative to SC was more pronounced among pts with high FLT3-ITD VAF than low FLT3-ITD VAF. The OS benefit with quizartinib in pts with NPM1wt/DNMT3Amut was maintained in both low and high FLT3-ITD VAF groups. Similarly, for other DNMT3A/NPM1 co-permutations, OS in both low and high FLT3-ITD VAF groups was consistent with OS in the co-mutation group.

Conclusions: Key co-mutations identified here potentially affect treatment response and OS with quizartinib vs SC. Our results suggest that molecular subsets of R/R AML pts may particularly derive clinical benefit from quizartinib.

TableCRc, %Median OS, monthsQuizartinibSCQuizartinibSCHR95% CIITT Population (N = 367)a48276.24.70.760.58-0.98Single Gene Analyses (n = 304)bDNMT3Amut (n = 182)52376.35.40.6520.44-0.97DNMT3Awt (n = 122)40246.04.60.8490.53-1.37NPM1mut (n = 168)48395.14.70.9540.63-1.44NPM1wt (n = 136)47218.55.10.4850.31-0.76TET2mut (n = 98)34326.22.90.6640.38-1.16TET2wt (n = 206)54306.35.40.7280.51-1.05CEBPAmut (n = 46)44428.58.71.9220.80-4.62CEBPAwt (n = 258)48296.24.50.6130.45-0.84IDH1/2mut (n = 49)32275.53.70.4270.20-0.92IDH1/2wt (n = 255)51316.55.10.750.54-1.04Double Gene Analyses (n = 304)NPM1wt/DNMT3Amut (n = 44)61279.04.50.2390.09-0.61NPM1mut/DNMT3Amut (n = 138)50405.45.40.8370.52-1.34FLT3-ITD VAF AnalysesFLT3-ITD high VAF50195.53.90.6890.51-0.93FLT3-ITD low VAF43467.96.10.8570.53-1.40FLT3-ITD VAF Analyses in Selected MutationsDNMT3Amut high VAF53215.82.70.6260.40-0.98DNMT3Amut low VAF526910.26.40.7370.36-1.51NPM1wt/DNMT3Amut high VAF6409.01.50.01790.002-0.16NPM1wt/DNMT3Amut low VAF555011.36.20.3720.11-1.23aN = 367; quizartinib, n = 245; SC, n = 122bBaseline bone marrow samples were available and viable from 304 of 367 pts in the ITT population

Citation Format: Alexander E. Perl, Jorge E. Cortes, Siddhartha Ganguly, Samer K. Khaled, Alwin Krämer, Giovanni Martinelli, Nigel H. Russell, Ken C. Chang, Kazunobu Kato, Yuhu Yan, Li-An Xu, Sergey Korkhov, Tobias Günnel, Hiroyuki Sumi, Arnaud Lesegretain, Flora Berisha, Derek Mires, Aziz Benzohra, Takeshi Isoyama, Cedric Dos Santos, Mark J. Levis. Effect of co-mutations and FLT3-ITD variant allele frequency (VAF) on response to quizartinib or salvage chemotherapy (SC) in relapsed/refractory (R/R) acute myeloid leukemia (AML) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 784.

Quizartinib, a selective FLT3 inhibitor, maintains antileukemic activity in preclinical models of RAS-mediated midostaurin-resistant acute myeloid leukemia cells

FLT3 internal tandem duplication (ITD) mutations are associated with poor prognosis in patients with acute myeloid leukemia (AML). In this preclinical study, we characterized the binding affinity and selectivity of quizartinib, a small-molecule inhibitor of FLT3, and AC886, the active metabolite of quizartinib, compared with those of other FLT3 inhibitors. Selectivity profiling against >400 kinases showed that quizartinib and AC886 were highly selective against FLT3. Quizartinib and AC886 inhibited FLT3 signaling pathways in FLT3-ITD–mutated AML cells, leading to potent growth inhibition with IC₅₀ values of <1 nM. When quizartinib was administered to mice bearing FLT3-ITD mutated tumors, AC886 was rapidly detected and tumor regression was observed at doses of ≥1 mg/kg without severe body weight loss. In addition, quizartinib inhibited the viability of midostaurin-resistant MOLM-14 cells and exerted potent antitumor activity in mouse xenograft models without severe body weight loss, while midostaurin and gilteritinib did not show significant antitumor effects. This is the first detailed characterization of quizartinib and AC886 in comparison with other FLT3 inhibitors under the same experimental conditions. Preclinical antileukemic activity in midostaurin-resistant FLT3-ITD–mutated AML cells suggests the potential value of quizartinib following midostaurin failure in patients with FLT3-ITD mutated AML.

Outcome of older (≥70 years) APL patients frontline treated with or without arsenic trioxide-an International Collaborative Study

Data on outcome in older (≥70 years) patients with acute promyelocytic leukemia after treatment with arsenic trioxide (ATO) compared with standard chemotherapy (CTX) is scarce. We evaluated 433 patients (median age, 73.4 years) treated either with ATO+ all-trans retinoic acid (ATO/ATRA; n = 26), CTX/ATRA + ATO during consolidation (CTX/ATRA/ATO; n = 148), or with CTX/ATRA (n = 259). Median follow-up for overall survival (OS) was 4.8 years. Complete remissions (CR) were achieved in 92% with ATO/ATRA and 82% with CTX/ATRA; induction death rates were 8% and 18%, respectively. For analysis of postremission outcomes we combined the ATO/ATRA and CTX/ATRA/ATO groups (ATO/ATRA ± CTX). Cumulative incidence of relapse (CIR) was significantly lower after ATO/ATRA ± CTX compared with CTX/ATRA (P < 0.001). The same held true when restricting the analysis according to the treatment period after the year 2000. OS of patients in CR1 was not different between ATO/ATRA ± CTX compared with CTX/ATRA (P = 0.20). High (>10 × 10⁹/l) white blood cell (WBC) counts at diagnosis were associated with higher CIR (P < 0.001) compared with lower WBC in the CTX/ATRA group, but not in the ATO/ATRA ± CTX group (P = 0.48). ATO, when added to ATRA or CTX/ATRA is feasible and effective in elderly patients for remission induction and consolidation, particularly in patients with high WBC at diagnosis.

Allogeneic hematopoietic cell transplantation improves outcome of adults with t(6;9) acute myeloid leukemia: results from an international collaborative study

Acute myeloid leukemia (AML) with t(6;9)(p22;q34) is a distinct entity accounting for 1-2% of AML cases. A substantial proportion of these patients have a concomitant FLT3-ITD. While outcomes are dismal with intensive chemotherapy, limited evidence suggests allogeneic hematopoietic cell transplantation (allo-HCT) may improve survival if performed early during first complete remission. We report on a cohort of 178 patients with t(6;9)(p22;q34) within an international, multicenter collaboration. Median age was 46 years (range: 16-76), AML was de novo in 88%, FLT3-ITD was present in 62%, and additional cytogenetic abnormalities in 21%. Complete remission was achieved in 81% (n=144), including 14 patients who received high-dose cytarabine after initial induction failure. With a median follow up of 5.43 years, estimated overall survival at five years was 38% (95%CI: 31-47%). Allo-HCT was performed in 117 (66%) patients, including 89 in first complete remission. Allo-HCT in first complete remission was associated with higher 5-year relapse-free and overall survival as compared to consolidation chemotherapy: 45% (95%CI: 35-59%) and 53% (95%CI: 42-66%) versus 7% (95%CI: 3-19%) and 23% (95%CI: 13-38%), respectively. For patients undergoing allo-HCT, there was no difference in overall survival rates at five years according to whether it was performed in first [53% (95%CI: 42-66%)], or second [58% (95%CI: 31-100%); n=10] complete remission or with active disease/relapse [54% (95%CI: 34-84%); n=18] (P=0.67). Neither FLT3-ITD nor additional chromosomal abnormalities impacted survival. In conclusion, outcomes of t(6;9)(p22;q34) AML are poor with chemotherapy, and can be substantially improved with allo-HCT.

A Phase II Study of Midostaurin and 5-Azacitidine for Untreated Elderly and Unfit Patients With FLT3 Wild-type Acute Myelogenous Leukemia

BACKGROUND

Midostaurin, a multikinase inhibitor, is approved for treatment of FLT3-mutant acute myeloid leukemia (AML). A phase I study established that midostaurin 75 mg orally twice daily for 14 days with standard dose azacitidine was safe and tolerable in elderly patients with AML. Herein, we report the phase II expansion cohort of previously untreated elderly or unfit patients with AML.

PATIENTS AND METHODS

Primary objectives were to further describe the toxicity profile and determine the response rate in untreated patients with AML. Patients received midostaurin 75 mg orally twice daily on days 8 to 21 in combination with intravenous azacitidine at 75 mg/m² on days 1 to 7. Plasma inhibitory activity assay for FLT3 was performed pretreatment and on day 8 and day 15 of each cycle.

RESULTS

Twenty-six patients (median age, 74 years; range, 59-85 years) with FLT3 wild-type AML were accrued. Patients received a median of 2 cycles of therapy (range, 1-10 cycles). Seven (29%) of 24 evaluable patients achieved a clinical response (4 complete response; 1 complete response with incomplete count recovery; and 2 partial response). The median overall survival was 244 days (95% confidence interval, 203-467 days). Hematologic, infectious, and gastrointestinal toxicities were comparable to similar studies. Peripheral blood FLT3 wild-type phosphorylation declined to 8% to 55% of pretreatment by day 15 of cycle 1 (7 patients) and declined with subsequent cycles (< 10% baseline) in 2 patients who were analyzed after cycle 3.

CONCLUSION

Multiple cycles of azacitidine and midostaurin were not well-tolerated, but persistent inhibition of FLT3 wild-type phosphorylation suggest intermittent dosing of midostaurin should be considered in future low-intensity regimens for FLT3-mutant AML.

Gilteritinib or Chemotherapy for Relapsed or Refractory FLT3-Mutated AML

BACKGROUND

Patients with relapsed or refractory acute myeloid leukemia (AML) with mutations in the FMS-like tyrosine kinase 3 gene (FLT3) infrequently have a response to salvage chemotherapy. Gilteritinib is an oral, potent, selective FLT3 inhibitor with single-agent activity in relapsed or refractory FLT3-mutated AML.

METHODS

In a phase 3 trial, we randomly assigned adults with relapsed or refractory FLT3-mutated AML in a 2:1 ratio to receive either gilteritinib (at a dose of 120 mg per day) or salvage chemotherapy. The two primary end points were overall survival and the percentage of patients who had complete remission with full or partial hematologic recovery. Secondary end points included event-free survival (freedom from treatment failure [i.e., relapse or lack of remission] or death) and the percentage of patients who had complete remission.

RESULTS

Of 371 eligible patients, 247 were randomly assigned to the gilteritinib group and 124 to the salvage chemotherapy group. The median overall survival in the gilteritinib group was significantly longer than that in the chemotherapy group (9.3 months vs. 5.6 months; hazard ratio for death, 0.64; 95% confidence interval [CI], 0.49 to 0.83; P<0.001). The median event-free survival was 2.8 months in the gilteritinib group and 0.7 months in the chemotherapy group (hazard ratio for treatment failure or death, 0.79; 95% CI, 0.58 to 1.09). The percentage of patients who had complete remission with full or partial hematologic recovery was 34.0% in the gilteritinib group and 15.3% in the chemotherapy group (risk difference, 18.6 percentage points; 95% CI, 9.8 to 27.4); the percentages with complete remission were 21.1% and 10.5%, respectively (risk difference, 10.6 percentage points; 95% CI, 2.8 to 18.4). In an analysis that was adjusted for therapy duration, adverse events of grade 3 or higher and serious adverse events occurred less frequently in the gilteritinib group than in the chemotherapy group; the most common adverse events of grade 3 or higher in the gilteritinib group were febrile neutropenia (45.9%), anemia (40.7%), and thrombocytopenia (22.8%).

CONCLUSIONS

Gilteritinib resulted in significantly longer survival and higher percentages of patients with remission than salvage chemotherapy among patients with relapsed or refractory FLT3-mutated AML. (Funded by Astellas Pharma; ADMIRAL ClinicalTrials.gov number, NCT02421939.).

Abstract 1318: Preclinical characterization of quizartinib and AC886, a metabolite of quizartinib, in AML models, and anti-leukemic activity of quizartinib on midostaurin-resistant AML cells

FLT3 mutations have been found in about 30% of acute myeloid leukemia (AML) cases, and the most common form of FLT3 mutation is internal tandem duplication (ITD) in the juxtamembrane domain, which occurs in approximately 25% of adult AML patients and 10-15% of pediatric patients. FLT3-ITD is a driver mutation in AML and the FLT3-ITD presence is associated with poor prognosis in AML patients. Quizartinib is a second-generation small-molecule inhibitor of FLT3, and a phase 3, QuANTUM-R trial showed significantly prolonged overall survival in patients with FLT3-ITD-mutated relapsed/refractory AML. In this preclinical study, we characterized quizartinib and AC886, a metabolite of quizartinib, compared with other FLT3 inhibitors including midostaurin, gilteritinib, crenolanib and sorafenib, and then evaluated the anti-tumor effect of quizartinib on midostaurin-resistant AML cells. Selectivity profiling of the FLT3 inhibitors against over 400 kinases and over 80 non-kinases showed that quizartinib and AC886 were highly selective against FLT3. Quizartinib and AC886 clearly inhibited FLT3 signaling pathways such as STAT5, RAS/MAPK and PI3K/AKT cascades in FLT3-ITD-mutated AML cells, leading to potent growth inhibition of the AML cells with the IC50 values of &lt;1 nM. When quizartinib was orally administered once a day to mice bearing MV4-11 cells harboring FLT3-ITD mutation, AC886 was rapidly detected and the tumor regression was observed at doses of 1 mg/kg and over without severe body weight loss, while midostaurin and gilteritinib also showed the tumor regression at 30 mg/kg and 10 mg/kg, respectively. In addition, we evaluated the effect of quizartinib on midostaurin-resistant FLT3-ITD-mutated AML MOLM-14 cells, which were established after long term treatment of midostaurin, and acquired KRAS (G12A) or NRAS (G12C) mutation. Quizartinib inhibited the viability of the midostaurin-resistant MOLM-14 cells with the IC50 values of &lt;10 nM, and exerted potent anti-tumor activity in the xenograft models without severe body weight loss. On the other hand, midostaurin and gilteritinib did not show significant anti-tumor effect in the models. This is the first report on the detailed characterization of quizartinib and its metabolite AC886 in comparison with other FLT3 inhibitors. Preclinical anti-leukemic activity in midostaurin-resistant FLT3-ITD-mutated AML cells suggests the potential value of quizartinib for midostaurin failure in AML patients with FLT3-ITD mutations. Further clinical investigation is warranted to find the optimum treatment sequence with FLT3 inhibitors for the AML patients.

Citation Format: Tomoya Aikawa, Noriko Togashi, Koichi Iwanaga, Hiroyuki Okada, Yumi Nishiya, Shinichi Inoue, Mark J. Levis, Takeshi Isoyama. Preclinical characterization of quizartinib and AC886, a metabolite of quizartinib, in AML models, and anti-leukemic activity of quizartinib on midostaurin-resistant AML cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1318.

Abstract CT184: Gilteritinib significantly prolongs overall survival in patients with FLT3-mutated (FLT3mut+) relapsed/refractory (R/R) acute myeloid leukemia (AML): Results from the Phase III ADMIRAL trial

Introduction: Gilteritinib is a potent/selective oral inhibitor of FMS-like tyrosine kinase 3 (FLT3). Based upon interim analysis response rates from the ADMIRAL Phase III study of gilteritinib vs salvage chemotherapy (SC) in patients (pts) with R/R FLT3mut+ AML (NCT02421939), gilteritinib became the first FLT3 inhibitor approved as single agent therapy in this population. Here we present the final results of this pivotal trial.

Methods: Adults with confirmed FLT3mut+ AML (FLT3-ITD and/or FLT3-TKD D835 or I836 mutations) refractory to induction chemotherapy or in untreated first relapse were randomized (2:1) to receive continuous 28-day cycles of 120 mg/day gilteritinib or pre-randomization selected SC: low-dose cytarabine (LoDAC), azacitidine (AZA), mitoxantrone/etoposide/cytarabine (MEC), or fludarabine/cytarabine/granulocyte colony-stimulating factor/idarubicin (FLAG-IDA). Prior FLT3 inhibitor use, other than midostaurin or sorafenib, was excluded. Overall survival (OS) and the combined rate of complete remission/complete remission with partial hematologic recovery (CR/CRh) were co-primary endpoints. Secondary endpoints were event-free survival (EFS) and CR rate; safety/tolerability was also examined.

Results: A total of 371 pts were randomized: 247 to gilteritinib and 124 to SC (MEC, 25.7%; FLAG-IDA, 36.7%; LoDAC, 14.7%; AZA, 22.9%). Median age was 62 years (range, 19-85). Baseline FLT3 mutations were: FLT3-ITD, 88.4%; FLT3-TKD, 8.4%; both FLT3-ITD and FLT3-TKD, 1.9%; unconfirmed, 1.3%. Overall, 39.4% of pts had refractory AML and 60.6% had relapsed AML. Patients randomized to gilteritinib had significantly longer OS (9.3 months) than SC (5.6 months; hazard ratio [HR] for death = 0.637; P=0.0007); 1-year survival rates were 37.1% and 16.7%, respectively. The CR/CRh rates for gilteritinib and SC were 34.0% and 15.3%, respectively (P=0.0001); CR rates were 21.1% and 10.5% (2-sided P=0.0106). Median EFS was 2.8 months and 0.7 months in the gilteritinib and SC arms, respectively (HR 0.793, P=0.0830). Common adverse events (AEs) in all randomized pts were febrile neutropenia (43.7%), anemia (43.4%), and pyrexia (38.6%). Common grade ≥3 AEs related to gilteritinib were anemia (19.5%), febrile neutropenia (15.4%), thrombocytopenia (12.2%), and decreased platelet count (12.2%). Adjusted for exposure duration, serious treatment-emergent AEs per patient year were less common with gilteritinib (7.1%) than SC (9.2%).

Conclusions: In patients with R/R FLT3mut+ AML, the potent, selective FLT3 inhibitor gilteritinib resulted in significantly longer OS and higher response rates compared with chemotherapy and had a favorable safety profile. These results change the treatment paradigm for salvage therapy of R/R FLT3mut+ AML and establish gilteritinib as the new standard of care.

Citation Format: Alexander E. Perl, Giovanni Martinelli, Jorge E. Cortes, Andreas Neubauer, Ellin Berman, Stefania Paolini, Pau Montesinos, Maria R. Baer, Richard A. Larson, Celalettin Ustun, Francesco Fabbiano, Antonio Di Stasi, Robert Stuart, Rebecca Olin, Margaret Kasner, Fabio Ciceri, Wen-Chien Chou, Nikolai Podoltsev, Christian Recher, Hisayuki Yokoyama, Naoko Hosono, Sung-Soo Yoon, Je-Hwan Lee, Timothy Pardee, Amir T. Fathi, Chaofeng Liu, Xuan Liu, Erkut Bahceci, Mark J. Levis. Gilteritinib significantly prolongs overall survival in patients with FLT3-mutated (FLT3mut+) relapsed/refractory (R/R) acute myeloid leukemia (AML): Results from the Phase III ADMIRAL trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT184.