FLT3 inhibitors reshape acute myeloid leukemia care as trials push beyond current standards

Acute myeloid leukemia moves fast. The disease is defined by the rapid, unchecked clonal proliferation of myeloid precursor cells, and it remains the most common acute leukemia in adults. It is also molecularly diverse, which means that two patients with the same diagnosis can carry very different genetic drivers and very different outlooks. Among the best-described of those drivers are mutations in the FMS-like tyrosine kinase 3 gene, known simply as FLT3. A new open-access review published in Blood Research on 8 September 2026 by Ly V. Do, Jessica J. Jorgensen and Kieran D. Sahasrabudhe pulls together what current standards of care achieve for these patients and where the next wave of trials is heading.

The numbers explain why FLT3 attracts so much attention. Mutations affecting the FLT3 protein appear in roughly 30 percent of newly diagnosed AML cases. FLT3 is a class III receptor tyrosine kinase deeply involved in the signaling pathways that regulate hematopoiesis, the production of blood cells. When its ligand binds the extracellular domain, the receptor dimerizes, autophosphorylates and triggers downstream cascades that govern apoptosis, proliferation and differentiation of hematopoietic cells. FLT3 is overexpressed in the myeloid blasts of most AML cases, and activating mutations make the receptor fire without its ligand, driving ligand-independent proliferation.

Two mutation types dominate. Internal tandem duplications in the juxtamembrane region, called FLT3-ITD, occur in about 20 to 25 percent of AML cases, while point mutations, deletions and insertions in the tyrosine kinase domain, called FLT3-TKD, account for roughly 5 to 6 percent. The prognostic relevance of FLT3-TKD mutations, by contrast, remains unclear, with no consistent impact demonstrated. Under both the European LeukemiaNet 2022 system for patients receiving intensive frontline chemotherapy and the ELN 2024 system for those on less intensive venetoclax-based therapy, FLT3-ITD cases sit in the intermediate-risk category. Guidelines from the ELN and the 2025 National Comprehensive Cancer Network consensus recommend testing FLT3 status at initial diagnosis and at relapse, and although next-generation sequencing is increasingly used, polymerase chain reaction with fragment analysis remains the gold standard, because sequencing can miss large FLT3-ITD mutations at low variant allele frequencies below 5 percent.

Therapeutically, the field has split the work between inhibitor generations and types. Type 1 inhibitors, including midostaurin, gilteritinib and crenolanib, are active against both ITD and TKD mutations. Type 2 inhibitors, including sorafenib and quizartinib, act only against ITD. First-generation drugs such as midostaurin and sorafenib are less specific for FLT3 and carry more off-target effects; second-generation agents such as quizartinib, crenolanib and gilteritinib are more potent and selective. The landmark shift came from the phase III RATIFY trial, which enrolled 717 patients aged 18 to 59 with newly diagnosed FLT3-mutated AML and added midostaurin or placebo to standard 7-plus-3 induction with cytarabine and daunorubicin, followed by consolidation and optional maintenance. Median overall survival reached 74.7 months with midostaurin versus 25.6 months with placebo at a median follow-up of 59 months, a 22 percent lower risk of death (hazard ratio 0.78; 95 percent confidence interval 0.63 to 0.96; p = 0.009). That result won FDA approval for midostaurin with induction and consolidation chemotherapy.

A 10-year follow-up published in 2024 showed the midostaurin benefit persisted, with 10-year overall survival of 43.7 percent versus 38.6 percent for placebo (p = 0.0485), though the survival gap narrowed slightly with patient aging. Allogeneic stem cell transplantation in first remission carried a clear survival advantage, 56 percent versus 35.8 percent at 10 years (p = 0.001). Among more than 400 patients transplanted in first remission, midostaurin randomization produced a marginal benefit, 61.5 percent versus 49 percent (p = 0.064), which was not statistically significant. Midostaurin maintenance reduced relapse risk in ELN-favorable and intermediate-risk patients but not in adverse-risk patients, showed no overall survival benefit, and was not approved for maintenance by the FDA.

Quizartinib, a second-generation inhibitor restricted to FLT3-ITD disease, extended the intensive-chemotherapy story to older adults. The phase III QuANTUM-First trial, run across 193 institutions in 26 countries, enrolled 539 patients aged 18 to 75 with newly diagnosed FLT3-ITD AML and added quizartinib or placebo to induction and consolidation, with maintenance for up to three years afterward. Median overall survival was 31.9 months versus 15.1 months at a median follow-up of 39.2 months (hazard ratio 0.78; p = 0.032), securing FDA approval. Because the trial included patients up to age 75, quizartinib holds an on-label indication above age 60 that midostaurin lacks. Relapse risk fell in both age strata, though relapse-free and event-free survival benefits were less pronounced in older patients. Maintenance quizartinib helped patients who did not undergo transplantation but not those who did, shaping the current approval for up to three years of maintenance in non-transplant patients. The review stresses that RATIFY and QuANTUM-First differ in mutation scope, age range, allelic ratio thresholds, anthracycline choices and supportive care era, so cross-trial efficacy comparison is not valid. No head-to-head trial of quizartinib versus midostaurin exists, and limited preclinical and retrospective hints of greater quizartinib potency remain hypothesis-generating only.

For patients ineligible for intensive chemotherapy, the backbone is venetoclax plus azacitidine, approved in 2020 after the phase III Viale-A trial showed superior overall survival over azacitidine alone. In the FLT3-mutated subgroup, the combination produced a composite complete remission rate of 72.4 percent versus 36.4 percent (p = 0.02). A pooled analysis with an earlier phase Ib study found a 67 percent remission rate versus 36 percent, median overall survival of 12.5 months versus 8.6 months, and subtype differences: FLT3-ITD patients reached 63 percent remission with 9.9-month median survival, while FLT3-TKD patients reached 77 percent with 19.2 months. Those ITD numbers underline an unmet need, since FLT3-dependent subclones often expand and limit treatment success in this population. In relapsed or refractory disease, gilteritinib is the standard of care. The phase III ADMIRAL trial showed median overall survival of 9.3 months versus 5.6 months with salvage chemotherapy (two-sided p < 0.001), a benefit maintained when censored at transplantation (hazard ratio 0.58; 95 percent confidence interval 0.43 to 0.76), and confirmed in two-year follow-up. Quizartinib also works in relapsed FLT3-ITD disease in some countries, with the QuANTUM-R trial showing 6.2 versus 4.7 months median survival (hazard ratio 0.76; p = 0.02), but treatment-related deaths were higher, 33 percent versus 17 percent.

After transplantation, the evidence is more mixed. In the phase III MORPHO trial, post-transplant gilteritinib improved relapse-free survival in FLT3-ITD patients (hazard ratio 0.679; 95 percent confidence interval 0.459 to 1.005; p = 0.0518), but the difference missed statistical significance. A subgroup with detectable measurable residual disease did benefit significantly, and gilteritinib is often used for those patients. Sorafenib, despite toxicity, reduced relapse or death in the SORMAIN trial (hazard ratio 0.39; p = 0.013), with 24-month relapse-free survival of 85.0 percent versus 53.3 percent, and a Chinese trial cut one-year cumulative relapse incidence from 24.5 percent to 7 percent (hazard ratio 0.25; p = 0.0010). Yet in SORMAIN, 76.8 percent of sorafenib patients developed grade 3 or higher graft-versus-host disease and 22 percent discontinued for toxicity. Safety across the class includes myelosuppression, gastrointestinal effects, and QTc prolongation, which reached 14 percent with quizartinib in QuANTUM-First, including 3 percent grade 3 or higher and 0.8 percent ventricular fibrillation in the context of hypokalemia, prompting a boxed warning and required electrocardiogram and electrolyte monitoring. Gilteritinib caused QTc prolongation in 4.9 percent of ADMIRAL patients, and case reports of differentiation syndrome add another prescribing consideration.

Ongoing investigation is dense. A randomized phase II trial of gilteritinib versus midostaurin with 7-plus-3 therapy produced higher remission rates, 85.6 percent versus 72.4 percent (p = 0.042), but did not meet its primary endpoint of MRD-negative remission after induction. The phase III HOVON 156 AML trial is testing the same question in newly diagnosed AML and MDS-EB2. Crenolanib with frontline chemotherapy showed an 86 percent overall response rate, 77 percent complete remission rate and 44.7-month median event-free survival, prompting a randomized comparison against midostaurin. In unfit patients, the phase III Lacewing trial of gilteritinib plus azacitidine versus azacitidine alone failed, with median overall survival of 9.82 versus 8.87 months (p = 0.753), closing early for futility. Triplet regimens look more promising: gilteritinib with azacitidine and venetoclax produced a 96 percent remission rate, 23.4-month median relapse-free survival and 29.7-month median survival; venetoclax with decitabine and quizartinib reached 95 percent remission and 71 percent one-year survival; and a regimen of venetoclax, decitabine and any FLT3 inhibitor in patients over 60 achieved 92 percent remission and 80 percent two-year survival. The NCI Myelomatch initiative is now randomizing triplets against standard venetoclax-azacitidine. Resistance work points to Bcl-2 upregulation through NF-κB signaling in FLT3-ITD/D835 cells, rationalizing venetoclax combinations, and menin inhibitors such as revumenib and ziftomenib are entering combinations with gilteritinib and quizartinib after preclinical synergy. Even FLT3-wild-type disease is in play, since the Quiwi trial found quizartinib improved survival in that population, likely through off-target effects, spawning the global phase III QUANTUM-WT study. The review’s conclusion is blunt: midostaurin and quizartinib have improved intensive-chemotherapy outcomes, gilteritinib owns the relapsed setting, but better frontline options for unfit patients, better relapsed outcomes and resistance remain the field’s central unsolved problems.

Subject of Research: FLT3-mutated acute myeloid leukemia treatment standards and ongoing clinical investigation

Article Title: FLT3-mutated AML: standards of care and ongoing investigation

Article References: Do, L. V., Jorgensen, J. J., & Sahasrabudhe, K. D. (2026). FLT3-mutated AML: standards of care and ongoing investigation. Blood Research, 61(1), Article 50. https://doi.org/10.1007/s44313-026-00171-0

Image Credits: AI Generated

DOI: 10.1007/s44313-026-00171-0

Keywords: acute myeloid leukemia, FLT3 mutations, midostaurin, quizartinib, gilteritinib, venetoclax, azacitidine, allogeneic stem cell transplant, menin inhibitors, relapsed refractory AML, clinical trials, targeted therapy