Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3

PURPOSE

Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit.

METHODS

Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS.

RESULTS

Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575).

CONCLUSION

Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

Impact of inotuzumab ozogamicin on outcome in relapsed or refractory acute B-cell lymphoblastic leukemia patients prior to allogeneic hematopoietic stem cell transplantation and risk of sinusoidal obstruction syndrome/venous occlusive disease

We evaluated 58 patients with relapsed or refractory (r/r) acute B-lymphoblastic leukemia (B-ALL; median age 42.5 years; range, 16-69 years), treated with inotuzumab ozogamicin (INO) between 2016-2022 and who received an allogeneic hematopoietic stem cell transplantation (allo-HCT) consecutively. Forty-seven (81%) of the 58 patients were heavily pretreated receiving intensive chemotherapy +/- tyrosine kinase inhibitor, blinatumomab in 24 (41%) and allo-HCT at first-line in 11 (19%) patients. Complete remission rate prior to allo-HCT was 84%. Median follow-up was 30.5 months and median overall survival (OS) measured from start of INO was 11.2 months. One- and 2-year OS rates were 50% (95% confidence interval [CI]: 38.4-56.1) and 36.7% (95% CI: 25.5-52.9), respectively. Sinusoidal obstruction syndrome/venous occlusive disease (SOS/ VOD) after allo-HCT occurred in 17 (29%) patients. Of those, nine (53%) patients died due to SOS/VOD and multi-organ failure. Two had received >2 INO cycles (3 cycles, 5 cycles, N=1, each), all others ≤2 INO cycles prior to allo-HCT. Logistic regression analysis revealed conditioning with double alkylators (P=0.038) and allo-HCT during first-line therapy (P=0.050) as significant risk factors for SOS/VOD and in trend allo-HCT ≤60 days from last INO application (P=0.07), whereas number of INO cycles before allo-HCT and time between last INO application and allo-HCT were not significant. Relapse/progressive disease occurred in 20 (34%) patients. Of those, five (25%) patients are still alive, whereas 15 succumbed of their disease. Treatment with INO seems to be an effective approach with successful bridge-to-transplant. However, risk of SOS/VOD is high, necessitating continuous monitoring and recognition of SOS/VOD risk factors.

A phase 1 study of the irreversible FLT3 inhibitor FF-10101 in relapsed or refractory acute myeloid leukemia

FLT3 tyrosine kinase inhibitors (TKIs) have clinical efficacy for patients with FLT3-mutated AML (acute myeloid leukemia), but their impact is limited by resistance in the setting of monotherapy and by tolerability problems when used in combination therapies. FF-10101 is a novel compound that covalently binds to a cysteine residue near the active site of FLT3, irreversibly inhibiting receptor signaling. It is effective against most FLT3 activating mutations, and unlike other inhibitors is minimally vulnerable to resistance induced by FLT3 ligand (FL). We conducted a phase 1 dose escalation study of oral FF-10101 (NCT03194685) in patients with relapsed and/or refractory AML, the majority of whom harbored FLT3-activating mutations and/or had prior exposure to FLT3 inhibitors. Fifty-four participants enrolled in cohorts ranging from 10 to 225 mg per day and 50 to 100 mg twice daily (BID). The dose limiting toxicities (DLT) were diarrhea and QT prolongation. Among 40 response-evaluable participants, the composite complete response rate was 10%, and the overall response rate (including partial responses) was 12.5%, including patients who had progressed on gilteritinib. 56% of participants had prior exposure to FLT3 inhibitors. The recommended phase 2 dose (RP2D) was 75 mg BID. FF-10101 potentially represents a next-generation advance in the management of FLT3-mutated AML.

Sorafenib plus intensive chemotherapy in newly diagnosed FLT3-ITD AML: a randomized, placebo-controlled study by the ALLG

Sorafenib maintenance improves outcomes after hematopoietic cell transplant (HCT) for patients with FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) acute myeloid leukemia (AML). Although promising outcomes have been reported for sorafenib plus intensive chemotherapy, randomized data are limited. This placebo-controlled, phase 2 study (ACTRN12611001112954) randomized 102 patients (aged 18-65 years) 2:1 to sorafenib vs placebo (days 4-10) combined with intensive induction: idarubicin 12 mg/m2 on days 1 to 3 plus either cytarabine 1.5 g/m2 twice daily on days 1, 3, 5, and 7 (18-55 years) or 100 mg/m2 on days 1 to 7 (56-65 years), followed by consolidation and maintenance therapy for 12 months (post-HCT excluded) in newly diagnosed patients with FLT3-ITD AML. Four patients were excluded in a modified intention-to-treat final analysis (3 not commencing therapy and 1 was FLT3-ITD negative). Rates of complete remission (CR)/CR with incomplete hematologic recovery were high in both arms (sorafenib, 78%/9%; placebo, 70%/24%). With 49.1-months median follow-up, the primary end point of event-free survival (EFS) was not improved by sorafenib (2-year EFS 47.9% vs 45.4%; hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.51-1.51; P = .61). Two-year overall survival (OS) was 67% in the sorafenib arm and 58% in the placebo arm (HR, 0.76; 95% CI, 0.42-1.39). For patients who received HCT in first remission, the 2-year OS rates were 84% and 67% in the sorafenib and placebo arms, respectively (HR, 0.45; 95% CI, 0.18-1.12; P = .08). In exploratory analyses, FLT3-ITD measurable residual disease (MRD) negative status (<0.001%) after induction was associated with improved 2-year OS (83% vs 60%; HR, 0.4; 95% CI, 0.17-0.93; P = .028). In conclusion, routine use of pretransplant sorafenib plus chemotherapy in unselected patients with FLT3-ITD AML is not supported by this study.

Gilteritinib in Combination With Induction and Consolidation Chemotherapy and as Maintenance Therapy: A Phase IB Study in Patients With Newly Diagnosed AML

PURPOSE

Gilteritinib is a type 1 FLT3 inhibitor active as monotherapy for relapsed or refractory FLT3-mutated AML. We investigated the safety, tolerability, and efficacy of gilteritinib incorporated into intensive induction and consolidation chemotherapy, and as maintenance therapy for adult patients with newly diagnosed, non-favorable-risk AML.

METHODS

In this phase IB study (2215-CL-0103; ClinicalTrials.gov identifier: NCT02236013), 103 participants were screened and 80 were allocated to treatment. The study was divided into four parts: dose escalation, dose expansion, investigation of alternate anthracycline and gilteritinib schedule, and continuous gilteritinib during consolidation.

RESULTS

After dose escalation, 120 mg gilteritinib once daily was chosen for further study. There were 58 participants evaluable for response at this dose, 36 of whom harbored FLT3 mutations. For participants with FLT3-mutated AML, the composite complete response (CRc) rate was 89% (83% were conventional complete responses), all achieved after a single induction cycle. The median overall survival time was 46.1 months. Gilteritinib was well-tolerated in this context although the median time to count recovery during induction was approximately 40 days. Longer time-to-count recovery was associated with higher trough levels of gilteritinib, which, in turn, were associated with azole use. The recommended regimen is gilteritinib at a dose of 120 mg once daily from days 4 to 17 or 8 to 21 of a 7 + 3 induction with either idarubicin or daunorubicin and from day 1 continuously with high-dose cytarabine consolidation. Maintenance therapy with gilteritinib was well-tolerated.

CONCLUSION

These results demonstrated the safety and tolerability of gilteritinib incorporated into an induction and consolidation chemotherapy regimen, and as single-agent maintenance therapy for patients with newly diagnosed FLT3-mutant AML. The data herein provide an important framework for the design of randomized trials comparing gilteritinib with other FLT3 inhibitors.

Co-occurring mutations in ASXL1, SRSF2, and SETBP1 define a subset of myelodysplastic/ myeloproliferative neoplasm with neutrophilia

Identification of genomic signatures with consistent clinicopathological features in myelodysplastic/myeloproliferative neoplasm (MDS/MPN) is critical for improved diagnosis, elucidation of biology, inclusion in clinical trials, and development of therapies. We describe clinical and pathological features with co-existence of mutations in ASXL1 (missense or nonsense), SRSF2, and SKI homologous region of SETBP1, in 18 patients. Median age was 68 years with a male predominance (83%). Leukocytosis and neutrophilia were common at presentation. Marrow features included hypercellularity, granulocytic hyperplasia with megakaryocytic atypia, while the majority had myeloid hyperplasia and/or erythroid hypoplasia, myeloid dysplasia, and aberrant CD7 expression on blasts. Mutations in growth signaling pathways (RAS or JAK2) were noted at diagnosis or acquired during the disease course in 83% of patients. Two patients progressed upon acquisition of FLT3-TKD (acute myeloid leukemia) or KIT (aggressive systemic mastocytosis) mutations. The prognosis is poor with only two long-term survivors, thus far, who underwent blood or marrow transplantation. We propose that the presence of co-occurring ASXL1, SRSF2, and SETBP1 mutations can be diagnostic of a subtype of MDS/MPN with neutrophilia if clinical and morphological findings align. Our report underscores the association between genotype and phenotype within MDS/MPN and that genomic signatures should guide categorization of these entities.

Quizartinib plus chemotherapy in newly diagnosed patients with FLT3-internal-tandem-duplication-positive acute myeloid leukaemia (QuANTUM-First): a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Patients with acute myeloid leukaemia (AML) positive for internal tandem duplication (ITD) mutations of FLT3 have poor outcomes. Quizartinib, an oral, highly potent, selective, type 2 FLT3 inhibitor, plus chemotherapy showed antitumour activity with an acceptable safety profile in patients with FLT3-ITD-positive newly diagnosed AML. The aim of the study was to compare the effect of quizartinib versus placebo on overall survival in patients with FLT3-ITD-positive newly diagnosed AML aged 18-75 years.

METHODS

We conducted a randomised, double-blind, placebo-controlled, phase 3 trial comparing quizartinib and placebo in combination with chemotherapy in induction and consolidation, followed by quizartinib or placebo single-agent continuation, in patients with FLT3-ITD-positive newly diagnosed AML at 193 hospitals and clinics in 26 countries in Europe; North America; and Asia, Australia, and South America. Patients aged 18-75 years were eligible. Patients were randomly assigned (1:1) to the quizartinib group or the placebo group by an independent biostatistician through an interactive web and voice response system, stratified by region, age, and white blood cell count at diagnosis. Patients, investigators, funders, and contract research organisations were masked to treatments assigned. Induction therapy comprised a standard 7 + 3 induction regimen of cytarabine 100 mg/m2 per day (or 200 mg/m2 per day allowed if institutional or local standard) by continuous intravenous infusion from day 1 to day 7 and anthracycline (daunorubicin 60 mg/m2 per day or idarubicin 12 mg/m2 per day) by intravenous infusion on days 1, 2, and 3, then quizartinib 40 mg orally or placebo once per day, starting on day 8, for 14 days. Patients with complete remission or complete remission with incomplete neutrophil or platelet recovery received standard consolidation with high-dose cytarabine plus quizartinib (40 mg per day orally) or placebo, allogeneic haematopoietic cell transplantation (allo-HCT), or both as consolidation therapy, followed by continuation of single-agent quizartinib or placebo for up to 3 years. The primary outcome was overall survival, defined as time from randomisation until death from any cause and assessed in the intention-to-treat population. Safety was evaluated in all patients who received at least one dose of quizartinib or placebo. This study is registered with ClinicalTrials.gov (NCT02668653).

FINDINGS

Between Sept 27, 2016, and Aug 14, 2019, 3468 patients with AML were screened and 539 patients (294 [55%] male patients and 245 [45%] female patients) with FLT3-ITD-positive AML were included and randomly assigned to the quizartinib group (n=268) or placebo group (n=271). 148 (55%) of 268 patients in the quizartinib group and 168 (62%) of 271 patients in the placebo group discontinued the study, primarily because of death (133 [90%] of 148 in the quizartinib group vs 158 [94%] of 168 in the placebo group) or withdrawal of consent (13 [9%] of 148 in the quizartinib group vs 9 [5%] of 168 in the placebo group). Median age was 56 years (range 20-75, IQR 46·0-65·0). At a median follow-up of 39·2 months (IQR 31·9-45·8), median overall survival was 31·9 months (95% CI 21·0-not estimable) for quizartinib versus 15·1 months (13·2-26·2) for placebo (hazard ratio 0·78, 95% CI 0·62-0·98, p=0·032). Similar proportions of patients in the quizartinib and placebo groups had at least one adverse event (264 [100%] of 265 in the quizartinib group and 265 [99%] of 268 in the placebo group) and one grade 3 or higher adverse event (244 [92%] of 265 in the quizartinib group and 240 [90%] of 268 in the placebo group). The most common grade 3 or 4 adverse events were febrile neutropenia, hypokalaemia, and pneumonia in both groups and neutropenia in the quizartinib group.

INTERPRETATION

The addition of quizartinib to standard chemotherapy with or without allo-HCT, followed by continuation monotherapy for up to 3 years, resulted in improved overall survival in adults aged 18-75 years with FLT3-ITD-positive newly diagnosed AML. Based on the results from the QuANTUM-First trial, quizartinib provides a new, effective, and generally well tolerated treatment option for adult patients with FLT3-ITD-positive newly diagnosed AML.

FUNDING

Daiichi Sankyo.

Multi-center phase I trial of Ivosidenib as Maintenance Treatment following Allogeneic Hematopoietic Cell Transplantation for IDH1-Mutated Acute Myeloid Leukemia

PURPOSE

IDH1 (isocitrate dehydrogenase 1) mutations occur in 5-10% of patients with acute myeloid leukemia (AML). Ivosidenib is an IDH1 inhibitor, approved for use in patients with IDH1-mutated AML.

PATIENTS AND METHODS

We conducted a multi-center, phase I trial of maintenance ivosidenib following allogeneic hematopoietic cell transplantation (HCT) in patients with IDH1-mutated AML. Ivosidenib was initiated between days 30 and 90 following HCT and continued for up to twelve 28-day cycles. The first dose level was 500mg daily, with level reduction to 250mg daily, if needed, in a 3x3 de-escalation design. Ten additional patients would then receive the maximum tolerated (MTD) or recommended phase 2 dose (RP2D). The primary endpoint was establishing the MTD or RP2D of ivosidenib.

RESULTS

Eighteen patients were enrolled, of whom 16 initiated post-HCT ivosidenib. One dose limiting toxicity, grade(g) 3 QTc prolongation, was observed. The RP2D was established at 500mg daily. Attributable g≥3 adverse events were uncommon, with the most common being QTc prolongation in 2 patients. Eight patients discontinued maintenance, with only one due to adverse event. Six-month cumulative incidence (CI) of gII-IV aGVHD was 6.3%, and two-year CI of all cGVHD was 63%. Two-year CI of relapse and non-relapse mortality (NRM) were 19% and 0%, respectively. Two-year progression-free (PFS) was 81%, and two-year overall survival (OS) was 88%.

CONCLUSIONS

Ivosidenib is safe and well-tolerated as maintenance therapy following HCT. Cumulative incidence of relapse and NRM, as well as estimations of PFS and OS, were promising in this phase 1 study.

Outcomes in Patients with FLT3-Mutated Relapsed/ Refractory Acute Myelogenous Leukemia Who Underwent Transplantation in the Phase 3 ADMIRAL Trial of Gilteritinib versus Salvage Chemotherapy

The fms-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib improved the survival of patients with relapsed or refractory (R/R) FLT3-mutated acute myelogenous leukemia (AML) in the phase 3 ADMIRAL trial. In this study, we assessed survival and relapse rates of patients in the ADMIRAL trial who underwent hematopoietic stem cell transplantation (HSCT), as well as safety outcomes in patients who received post-transplantation gilteritinib maintenance therapy. ADMIRAL was a global phase 3 randomized controlled trial that enrolled adult patients with FLT3-mutated R/R AML. Patients with R/R AML who harbored FLT3 internal tandem duplication mutations in the juxtamembrane domain or D835/I836 point mutations in the tyrosine kinase domain were randomized (2:1) to gilteritinib (120 mg/day) or to preselected high- or low-intensity salvage chemotherapy (1 or 2 cycles). Patients in the gilteritinib arm who proceeded to HSCT could receive post-transplantation gilteritinib maintenance therapy if they were within 30 to 90 days post-transplantation and had achieved composite complete remission (CRc) with successful engraftment and no post-transplantation complications. Adverse events (AEs) during HSCT were recorded in the gilteritinib arm only. Survival outcomes and the cumulative incidence of relapse were assessed in patients who underwent HSCT during the trial. Treatment-emergent AEs were evaluated in patients who restarted gilteritinib as post-transplantation maintenance therapy. Patients in the gilteritinib arm underwent HSCT more frequently than those in the chemotherapy arm (26% [n = 64] versus 15% [n = 19]). For all transplantation recipients, 12- and 24-month overall survival (OS) rates were 68% and 47%, respectively. Despite a trend toward longer OS after pretransplantation CRc, post-transplantation survival was comparable in the 2 arms. Patients who resumed gilteritinib after HSCT had a low relapse rate after pretransplantation CRc (20%) or CR (0%). The most common AEs observed with post-transplantation gilteritinib therapy were increased alanine aminotransferase level (45%), pyrexia (43%), and diarrhea (40%); grade ≥3 AEs were related primarily to myelosuppression. The incidences of grade ≥III acute graft-versus-host disease and related mortality were low. Post-transplantation survival was similar across the 2 study arms in the ADMIRAL trial, but higher remission rates with gilteritinib facilitated receipt of HSCT. Gilteritinib as post-transplantation maintenance therapy had a stable safety and tolerability profile and was associated with low relapse rates. Taken together, these data support a preference for bridging therapy with gilteritinib over chemotherapy in transplantation-eligible patients.

Allogeneic Blood or Marrow Transplantation with High-Dose Post-Transplantation Cyclophosphamide for Acute Lymphoblastic Leukemia in Patients Age ≥55 Years

Patients age ≥55 years with acute lymphoblastic leukemia (ALL) fare poorly with conventional chemotherapy, with a 5-year overall survival (OS) of ∼20%. Tyrosine kinase inhibitors and novel B cell-targeted therapies can improve outcomes, but rates of relapse and death in remission remain high. Allogeneic blood or marrow transplantation (alloBMT) provides an alternative consolidation strategy, and post-transplantation cyclophosphamide (PTCy) facilitates HLA-mismatched transplantations with low rates of nonrelapse mortality (NRM) and graft-versus-host disease (GVHD). The transplantation database at Johns Hopkins was queried for patients age ≥55 years who underwent alloBMT for ALL using PTCy. The database included 77 such patients. Most received reduced-intensity conditioning (RIC) (88.3%), were in first complete remission (CR1) (85.7%), and had B-lineage disease (90.9%). For the entire cohort, 5-year relapse-free survival (RFS) and overall survival (OS) were 46% (95% confidence interval [CI], 34% to 57%) and 49% (95% CI, 37% to 60%), respectively. Grade III-IV acute GVHD occurred in only 3% of patients, and chronic GVHD occurred in 13%. In multivariable analysis, myeloablative conditioning led to worse RFS (hazard ratio [HR], 4.65; P = .001), whereas transplantation in CR1 (HR, .30; P = .004) and transplantation for Philadelphia chromosome-positive (Ph+) ALL versus T-ALL (HR, .29; P = .03) were associated with improved RFS. Of the 54 patients who underwent RIC alloBMT in CR1 for B-ALL, the 5-year RFS and OS were 62% (95% CI, 47% to 74%) and 65% (95% CI, 51% to 77%), respectively, with a 5-year relapse incidence of 16% (95% CI, 7% to 27%) and an NRM of 24% (95% CI, 13% to 36%). RIC alloBMT with PTCy in CR1 represents a promising consolidation strategy for B-ALL patients age ≥55 years.

An Update on FLT3 in Acute Myeloid Leukemia: Pathophysiology and Therapeutic Landscape

PURPOSE OF REVIEW

This review aims to summarize the pathophysiology, clinical presentation, and management of acute myeloid leukemia (AML) with FMS-like tyrosine kinase-3 (FLT3) mutations.

RECENT FINDINGS

The recent European Leukemia Net (ELN2022) recommendations re-classified AML with FLT3 internal tandem duplications (FLT3-ITD) as intermediate risk regardless of Nucleophosmin 1 (NPM1) co-mutation or the FLT3 allelic ratio. Allogeneic hematopoietic cell transplantation (alloHCT) is now recommended for all eligible patients with FLT3-ITD AML. This review outlines the role of FLT3 inhibitors in induction and consolidation, as well as for post-alloHCT maintenance. It outlines the unique challenges and advantages of assessing FLT3 measurable residual disease (MRD) and discusses the pre-clinical basis for the combination of FLT3 and menin inhibitors. And, for the older or unfit patient ineligible for upfront intensive chemotherapy, it discusses the recent clinical trials incorporating FLT3 inhibitors into azacytidine- and venetoclax-based regimens. Finally, it proposes a rational sequential approach for integrating FLT3 inhibitors into less intensive regimens, with a focus on improved tolerability in the older and unfit patient population. The management of AML with FLT3 mutation remains a challenge in clinical practice. This review provides an update on the pathophysiology and therapeutic landscape of FLT3 AML, as well as a clinical management framework for managing the older or unfit patient ineligible for intensive chemotherapy.

Venetoclax in combination with hypomethylating agent for the treatment of advanced myeloproliferative neoplasms and acute myeloid leukemia with extramedullary disease

The combination of venetoclax and hypomethylating agent (HMA/venetoclax) has emerged as a treatment option for patients with de novo acute myeloid leukemia (AML) who are unfit to receive intensive chemotherapy. In this single-center retrospective study, we evaluated clinical outcomes following treatment with HMA/venetoclax in 35 patients with advanced myeloproliferative neoplasms, myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes or AML with extramedullary disease. The composite complete remission (CR) rate (including confirmed/presumed complete cytogenetic response, acute leukemia response-complete, CR and CR with incomplete hematologic recovery) was 42.9% with median overall survival (OS) of 9.7 months. Complex karyotype was associated with inferior median OS (3.7 versus 12.2 months; p = 0.0002) and composite CR rate (22% versus 50.0%; p = 0.2444). Although SRSF2 mutations were associated with higher composite CR rate (80.0% versus 28.0%; p = 0.0082), this was not associated with longer median OS (10.9 versus 8.0 months; p = 0.2269). Future studies should include these patient subgroups.

The clinical impact of the molecular landscape of acute myeloid leukemia

Research into the underlying pathogenic mechanisms of acute myeloid leukemia (AML) has led to remarkable advances in our understanding of the disease. Mutations now allow us to explore the enormous diversity among cytogenetically defined subsets of AML, particularly the large subset of cytogenetically normal AML. Despite the progress in unraveling the tumor genome, only a small number of recurrent mutations have been incorporated into risk-stratification schemes and have been proven to be clinically relevant, targetable lesions. The current World Health Organization Classification of myeloid neoplasms and leukemia includes eight AML categories defined by recurrent genetic abnormalities as well as three categories defined by gene mutations. We here discuss the utility of molecular markers in AML in prognostication and treatment decision-making. New therapies based on targetable markers include IDH inhibitors (ivosidenib, enasidenib), venetoclax-based therapy, FLT3 inhibitors (midostaurin, gilteritinib, and quizartinib), gemtuzumab ozogamicin, magrolimab and menin inhibitors.

CCRL2 affects the sensitivity of myelodysplastic syndrome and secondary acute myeloid leukemia cells to azacitidine

Better understanding of the biology of resistance to DNA methyltransferase (DNMT) inhibitors (DNMTi) is required to identify therapies that can improve their efficacy for patients with highrisk myelodysplastic syndrome (MDS). CCRL2 is an atypical chemokine receptor that is upregulated in CD34+ cells from MDS patients and induces MDS and secondary AML (sAML) cell proliferation. In this study, we evaluated any role CCRL2 may have in the regulation of pathways associated with poor response or resistance to DNMTi. We found that CCRL2 KD in TF-1 cells downregulates DNA methylation and PRC2 activity pathways and increases DNA methyltransferases (DNMT) suppression by azacitidine in MDS/sAML vell lines (MDS92, MDS-L and TF-1). Consistently, CCRL2 deletion increased the sensitivity of these cells to azacitidine in vitro and the efficacy of azacitidine in an MDS-L xenograft model. Consistently, CCRL2 overexpression in MDS-L and TF-1 cells decreased their sensitivity to azacitidine. Finally, CCRL2 levels were higher in CD34+ cells from MDS and MDS/myeloproliferative neoplasm patients with poor response to DNMTi. In conclusion, we demonstrate that CCRL2 modulates epigenetic regulatory pathways, particularly DNMT levels, and affects MDS/sAML azacitidine sensitivity. These results support CCRL2 targeting as having MDS/sAML therapeutic potential.

Genomic landscape of myelodysplastic/myeloproliferative neoplasm can predict response to hypomethylating agent therapy

There are currently no known predictors of myelodysplastic syndrome (MDS)/myeloproliferative overlap neoplasm (MPN) patients' response to hypomethylating agents (HMA). Forty-three patients with MDS/MPN who were treated with HMA during chronic phase and had next-generation sequencing using the established 63-genes panel were identified. Complete and partial remission and marrow response were assessed based on the MDS/MPN International Working Group response criteria. On univariate analysis, younger age, higher number of mutations, and mutations in SETBP1, RUNX1, or EZH2 were associated with no response. Multivariable analysis for modeling response were conducted via least absolute shrinkage and selection operator logistic regression approach, and showed that mutations in SETBP1, RUNX1, or EZH2 predict lack of HMA response. While limited by sample size, our findings suggest that genomic landscape can potentially identify MDS/MPN patients with lower likelihood of response to HMA.

Abstract 5435: CCRL2 affects the sensitivity of MDS and secondary AML to azacitidine

INTRODUCTION: We recently found that the atypical chemokine receptor, CCRL2 promotes the growth of MDS and secondary AML (sAML) while CCRL2 knockdown inhibits their growth. The aim of the current study is to investigate if CCRL2 regulates pathways associated with the development of resistance to hypomethylating agents (HMA), commonly used drugs in MDS and occasionally sAML.

MATERIALS AND METHODS: We used lentivirus-mediated transduction of MDS92, MDS-L and TF-1 MDS/sAML cells to suppress CCRL2 expression. Two different shRNA constructs were used. We performed RNA sequencing and gene-set enrichment analysis of CCRL2 knocked down (KD) and wild-type (WT) TF-1 cells. We measured DNA methyl-transferases’ expression by western blot, CD11b and CD71 expression was measured in MDS and sAML cells to assess cell differentiation. Apoptosis was measured by Annexin V/PI staining, and clonogenicity by methylcellulose assays. CD34+ cells were sorted from bone marrow aspirates of MDS patients before the initiation of treatment with HMA by using magnetic beads and measurement of CCRL2 was performed by flow cytometry. Response to HMA in MDS patients was assessed by 6 months of treatment based on the International Working Group response criteria.

RESULTS: CCRL2 KD cells demonstrated suppression of pathways associated with PRC2 complex activity, histone modification, and DNA methylation. CCRL2 KD also lead to a more prominent degradation of DNMT1, DNMT3A and DNTM3B under azacitidine treatment. CCRL2 increased apoptosis in response to 0.5 and 1 μM azacitidine (P&lt;0.010) and MDS-L cells (P&lt;0.010 with both sh1 and sh2). Similarly, CCRL2 knockdown increased morphologic differentiation with both 0.5 and 1 μΜ azacitidine (P&lt;0.010) as well as increased the clonogenic inhibition caused by azacitidine (P&lt;0.05). In order to analyze the effect CCRL2 clinically, we analyzed CCRL2 expression in CD34+ cells from patients undergoing HMA treatment. Non-responders to HMA (progressive disease) express higher levels of CCRL2 compared to CD34+ cells from responders (complete remission, partial remission or stable disease) (P=0.020).

DISCUSSION: Our analysis suggests that CCRL2 regulates the expression of genes associated with induction of PRC2-mediated histone modification and DNA methylation in sAML cells. CCRL2 suppression also increased the sensitivity of MDS and sAML cells to azacitidine. In addition, increased CCRL2 expression in MDS cells is associated with worse response to HMA. These data suggest that targeting CCRL2 has therapeutic potential in MDS and sAML.

Citation Format: Theodoros Karantanos, Patric Teodorescu, Brandy Perkins, Marios Arvanitis, Ilias Christodolou, Christopher Esteb, W. Brian Dalton, Tania Jain, Amy E. DeZern, Lukasz P. Gondek, Mark J. Levis, Gabriel Ghiaur, Richard J. Jones. CCRL2 affects the sensitivity of MDS and secondary AML to azacitidine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5435.

Characteristics and outcome of patients with acute myeloid leukemia and trisomy 4

We retrospectively studied 125 patients with acute myeloid leukemia and trisomy 4 (median age at diagnosis, 58 years; range, 16-77 years) treated between 2000 and 2019 within a multicenter study. Trisomy 4 was the sole abnormality in 28 (22%) patients and additional abnormalities were present in 97 (78%) patients. Twenty-two (22%) and 15 (15%) of 101 tested patients harbored NPM1 and FLT3-ITD mutations. Two (3%) of 72 tested patients had double CEBPA mutations. Data on response to intensive anthracycline-based induction therapy were available for 119 patients. Complete remission was achieved in 67% (n=80) and the early death rate was 5% (n=6). Notably, patients with trisomy 4 as sole abnormality had a complete remission rate of 89%. Allogeneic hematopoietic cell transplantation was performed in 40 (34%) patients, of whom 19 were transplanted in first complete remission. The median follow-up of the intensively treated cohort was 5.76 years (95% confidence interval [95% CI]: 2.99-7.61 years). The 5-year overall survival and relapse-free survival rates were 30% (95% CI: 22-41%) and 27% (95% CI: 18-41%), respectively. An Andersen-Gill regression model on overall survival revealed that favorable-risk according to the European LeukemiaNet classification (hazard ratio [HR]=0.34; P=0.006) and trisomy 4 as sole abnormality (HR=0.41; P=0.01) were favorable factors, whereas age with a difference of 10 years (HR=1.15; P=0.11), female gender (HR=0.74; P=0.20) and allogeneic hematopoietic cell transplantation (HR=0.64; P=0.14) did not have an significant impact. In our cohort, patients with trisomy 4 as their sole abnormality had a high complete remission rate and favorable clinical outcome. Allogeneic hematopoietic cell transplantation did not seem to improve overall survival.

Follow-up of patients with R/R FLT3-mutation-positive AML treated with gilteritinib in the phase 3 ADMIRAL trial

The phase 3 ADMIRAL (NCT02421939; Study ID: 2215-CL-0301) trial showed superior overall survival in patients with relapsed/refractory FLT3-mutation-positive acute myeloid leukemia (AML) randomized 2:1 to receive the oral FMS-like tyrosine kinase 3 inhibitor gilteritinib vs those randomized to receive salvage chemotherapy (SC). Here we provide a follow-up of the ADMIRAL trial 2 years after the primary analysis to clarify the long-term treatment effects and safety of gilteritinib in these patients with AML. At the time of this analysis, the median survival follow-up was 37.1 months, with deaths in 203 of 247 and 97 of 124 patients in the gilteritinib and SC arms, respectively; 16 gilteritinib-treated patients remained on treatment. The median overall survival for the gilteritinib and SC arms was 9.3 and 5.6 months, respectively (hazard ratio, 0.665; 95% confidence interval [CI], 0.518, 0.853; two-sided P = .0013); 2-year estimated survival rates were 20.6% (95% CI, 15.8, 26.0) and 14.2% (95% CI, 8.3, 21.6). The gilteritinib-arm 2-year cumulative incidence of relapse after composite complete remission was 75.7%, with few relapses occurring after 18 months. Overall, 49 of 247 patients in the gilteritinib arm and 14 of 124 patients in the SC arm were alive for ≥2 years. Twenty-six gilteritinib-treated patients remained alive for ≥2 years without relapse; 18 of these patients underwent transplantation (hematopoietic stem cell transplantation [HSCT]) and 16 restarted gilteritinib as post-HSCT maintenance therapy. The most common adverse events of interest during years 1 and 2 of gilteritinib therapy were increased liver transaminase levels; adverse event incidence decreased in year 2. Thus, continued and post-HSCT gilteritinib maintenance treatment sustained remission with a stable safety profile. These findings confirm that prolonged gilteritinib therapy is safe and is associated with superior survival vs SC. This trial was registered at www.clinicaltrials.gov as #NCT02421939.

V-FAST master trial: Preliminary results of treatment with CPX-351 plus midostaurin in adults with newly diagnosed FLT3-mutated acute myeloid leukemia

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Background: CPX-351 (US: Vyxeos; Europe: Vyxeos liposomal), a dual-drug liposomal encapsulation of daunorubicin and cytarabine in a synergistic 1:5 molar ratio, is approved for newly diagnosed, therapy-related AML or AML with myelodysplasia-related changes in patients aged ≥1 year in the US and in adults in Europe. In a phase 3 study in older adults with newly diagnosed, high-risk/secondary AML, CPX-351 significantly improved overall survival and remission rates versus conventional 7+3, with a comparable safety profile. Preclinical data suggest CPX-351 may have synergistic activity with targeted agents, including the FLT3 inhibitor midostaurin (MID). Herein, we report preliminary results for the cohort of adults treated with CPX-351 + MID in the V-FAST (Vyxeos – First Phase Assessment with Targeted Agents) trial. Methods: V-FAST is an open-label, multicenter, multiarm, nonrandomized, phase 1b master trial (NCT04075747) to evaluate the safety and preliminary efficacy of CPX-351 combined with targeted agents (midostaurin, venetoclax, enasidenib). Eligible adults in the CPX-351 + MID cohort were aged 18 to 75 years, had newly diagnosed AML with a FLT3 internal tandem duplication (ITD) or tyrosine kinase domain (TKD) mutation, were fit for intensive chemotherapy, and had an ECOG performance status of 0 to 2. The dose-exploration phase (3+3 design) determined a recommended phase 2 dose of CPX-351 100 units/m2 (daunorubicin 44 mg/m2 + cytarabine 100 mg/m2) on Days 1, 3, and 5 + MID 50 mg BID on Days 8 to 21. There were no dose-limiting toxicities, and additional patients were enrolled in the expansion phase at this dose. Results: A total of 23 patients received CPX-351 + MID and had sufficient data to be included in the analysis (cutoff date: 1/20/2022). Patient baseline characteristics are shown in the Table. Treatment-emergent adverse events (TEAEs) in ≥40% of patients included febrile neutropenia (78%), nausea (65%), increased alanine aminotransferase (57%), leukopenia (57%), thrombocytopenia (57%), headache (43%), and hyponatremia (43%). All patients experienced a grade 3/4 TEAE, primarily hematologic events. Nonhematologic grade 3/4 TEAEs in ≥2 patients included pneumonia (17%), lung infection (13%), and hyperglycemia (9%). There were no grade 5 TEAEs and no deaths on or before Day 60. Complete remission was achieved by 18/22 (82%) evaluable patients after the first induction cycle. Conclusions: Preliminary results from the V-FAST trial suggest CPX-351 + MID is feasible, with a manageable safety profile and promising remission rates in adults with newly diagnosed AML who have a FLT3 mutation. Clinical trial information: NCT04075747. [Table: see text]

Clinical outcomes in patients with relapsed/refractory FLT3-mutated acute myeloid leukemia treated with gilteritinib who received prior midostaurin or sorafenib

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

The role of the atypical chemokine receptor CCRL2 in myelodysplastic syndrome and secondary acute myeloid leukemia

The identification of new pathways supporting the myelodysplastic syndrome (MDS) primitive cells growth is required to develop targeted therapies. Within myeloid malignancies, men have worse outcomes than women, suggesting male sex hormone-driven effects in malignant hematopoiesis. Androgen receptor promotes the expression of five granulocyte colony-stimulating factor receptor-regulated genes. Among them, CCRL2 encodes an atypical chemokine receptor regulating cytokine signaling in granulocytes, but its role in myeloid malignancies is unknown. Our study revealed that CCRL2 is up-regulated in primitive cells from patients with MDS and secondary acute myeloid leukemia (sAML). CCRL2 knockdown suppressed MDS92 and MDS-L cell growth and clonogenicity in vitro and in vivo and decreased JAK2/STAT3/STAT5 phosphorylation. CCRL2 coprecipitated with JAK2 and potentiated JAK2-STAT interaction. Erythroleukemia cells expressing JAK2V617F showed less effect of CCRL2 knockdown, whereas fedratinib potentiated the CCRL2 knockdown effect. Conclusively, our results implicate CCRL2 as an MDS/sAML cell growth mediator, partially through JAK2/STAT signaling.

Outcome of relapsed or refractory acute B-lymphoblastic leukemia patients and BCR-ABL positive blast cell crisis of B-lymphoid lineage with extramedullary disease receiving inotuzumab ozogamicin

Acute lymphoblastic leukemia (ALL) can relapse in the extramedullary compartment, with or without medullary involvement. Response to treatment may be unique. We evaluated response to inotuzumab ozogamicin (INO) in 31 relapsed/refractory (r/r) BALL patients with extramedullary disease (EMD). Median age was 31 (range, 19-81) years. All patients were heavily pretreated, including allogeneic hematopoietic stem cell transplantation (allo-HCT; n=18). Overall response rate after two INO cycles was 84% (complete remission (CR), 55%; partial remission (PR), 29%; resistant disease (PD), 13%; early death, 3%). Median follow-up was 29 months and median overall survival (OS) 12.8 months. One-year and 2-year OS rates were 53% (95%-CI, 37-76%) and 18% (95%-CI, 8-43%), respectively. Age had no impact on OS when assessed as a continuous variable or dichotomized at 60 years. Twelve patients proceeded to allo-HCT (CR, n=6; PR, n=3; PD, n=3). Prior to allo-HCT, eight patients received ≤2 and four patients 3-4 INO cycles. Sinusoidal obstruction syndrome was reported in three patients, including one after transplant. Allo-HCT evaluated as a time-dependent variable had no impact on OS. INO seems to be effective as debulking strategy in r/r-ALL with EMD. However, INO followed by allo-HCT seems not to be effective in maintaining long term disease control.

Phase II Trial of Pembrolizumab after High-Dose Cytarabine in Relapsed/Refractory Acute Myeloid Leukemia

Immune suppression, exhaustion, and senescence are frequently seen throughout disease progression in acute myeloid leukemia (AML). We conducted a phase II study of high-dose cytarabine followed by pembrolizumab 200 mg i.v. on day 14 to examine whether PD-1 inhibition improves clinical responses in relapsed/refractory (R/R) AML. Overall responders could receive pembrolizumab maintenance up to 2 years. Among 37 patients enrolled, the overall response rate, composite complete remission (CRc) rate (primary endpoint), and median overall survival (OS) were 46%, 38%, and 11.1 months, respectively. Patients with refractory/early relapse and those receiving treatment as first salvage had encouraging outcomes (median OS, 13.2 and 11.3 months, respectively). Grade ≥3 immune-related adverse events were rare (14%) and self-limiting. Patients who achieved CRc had a higher frequency of progenitor exhausted CD8⁺ T cells expressing TCF-1 in the bone marrow prior to treatment. A multifaceted correlative approach of genomic, transcriptomic, and immunophenotypic profiling offers insights on molecular correlates of response and resistance to pembrolizumab.

Significance

Immune-checkpoint blockade with pembrolizumab was tolerable and feasible after high-dose cytarabine in R/R AML, with encouraging clinical activity, particularly in refractory AML and those receiving treatment as first salvage regimen. Further study of pembrolizumab and other immune-checkpoint blockade strategies after cytotoxic chemotherapy is warranted in AML.See related commentary by Wei et al., p. 551. This article is highlighted in the In This Issue feature, p. 549.

A method for overcoming plasma protein inhibition of tyrosine kinase inhibitors

Plasma protein binding reduces potency of staurosporine-derived tyrosine kinase inhibitors against Flt3-mutant AML. “Decoy” drugs interfering with the binding, including mifepristone, can be harnessed to restore the antileukemia activity.

FMS-like tyrosine kinase 3 (FLT3) is the most frequently mutated gene in acute myeloid leukemia and a target for tyrosine kinase inhibitors (TKI). FLT3 TKIs have yielded limited improvements to clinical outcomes. One reason for this is TKI inhibition by endogenous factors. We characterized plasma protein binding of FLT3 TKI, specifically staurosporine derivatives (STS-TKI) by alpha-1-acid glycoprotein (AGP), simulating its effects upon drug efficacy. Human AGP inhibits the antiproliferative activity of STS-TKI in FLT3/ITD-dependent cells, with IC₅₀ shifts higher than clinically achievable. This is not seen with nonhuman plasma. Mifepristone cotreatment, with its higher AGP affinity, improves TKI activity despite AGP, yielding IC₅₀s predicted to be clinically effective. In a mouse model of AGP drug inhibition, mifepristone restores midostaurin activity. This suggests combinatorial methods for overcoming plasma protein inhibition of existing TKIs for leukemia as well as providing a platform for investigating the drug–protein interaction space for developing more potent small-molecule agents.

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

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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

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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

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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.

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.