Enhancing Therapeutic Efficacy of FLT3 Inhibitors with Combination Therapy for Treatment of Acute Myeloid Leukemia.

FMS-like tyrosine kinase 3 (FLT3) mutations are genetic changes found in approximately thirty percent of patients with acute myeloid leukemia (AML). FLT3 mutations in AML represent a challenging clinical scenario characterized by a high rate of relapse, even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The advent of FLT3 tyrosine kinase inhibitors (TKIs), such as midostaurin and gilteritinib, has shown promise in achieving complete remission. However, a substantial proportion of patients still experience relapse following TKI treatment, necessitating innovative therapeutic strategies. This review critically addresses the current landscape of TKI treatments for FLT3+ AML, with a particular focus on gilteritinib. Gilteritinib, a highly selective FLT3 inhibitor, has demonstrated efficacy in targeting the mutant FLT3 receptor, thereby inhibiting aberrant signaling pathways that drive leukemic proliferation. However, monotherapy with TKIs may not be sufficient to eradicate AML blasts. Specifically, we provide evidence for integrating gilteritinib with mammalian targets of rapamycin (mTOR) inhibitors and interleukin-15 (IL-15) complexes. The combination of gilteritinib, mTOR inhibitors, and IL-15 complexes presents a compelling strategy to enhance the eradication of AML blasts and enhance NK cell killing, offering a potential for improved patient outcomes.

[Concentration of gilteritinib in the cerebrospinal fluid of a patient with relapsed FLT3-ITD positive acute myeloid leukemia with optic nerve involvement].

A 72-year-old woman with relapsed FLT3-ITD-positive acute myeloid leukemia was treated with gilteritinib and achieved complete remission with incomplete hematological recovery. However, two months later, she developed optic nerve infiltration and lost vision in her right eye while maintaining hematological remission on gilteritinib. Intrathecal injection of cytotoxic drugs reduced the number of blasts in the cerebrospinal fluid (CSF), but her vision did not recover. At the onset of optic nerve infiltration, at a dose of 80 mg/day gilteritinib, the plasma trough and CSF levels of gilteritinib were 151.9 ng/ml and 1.9 ng/ml, respectively, with a central nervous system (CNS) penetration rate of 1.3%. Hematologic progressive disease (PD) was detected after 40 days, and the patient died one month later. Target sequencing at the time of hematologic PD revealed the FLT3 F691L mutation, which is known to confer resistance to gilteritinib. In this patient, pharmacokinetic (low CNS penetration of gilteritinib) and pharmacodynamic (acquisition of a drug resistance mutation) mechanisms were thought to be responsible for the CNS relapse and hematologic PD, respectively. We believe this is a valuable case to report considering the scarcity of data on CNS penetration of FLT3 inhibitors and their effects on CNS disease in the literature.

Triplet therapy with gilteritinib, venetoclax, and azacitidine for relapsed/refractory FLT3mut acute myeloid leukemia.

The FMS-related tyrosine kinase 3 (FLT3) inhibitor gilteritinib is standard therapy for relapsed/refractory (R/R) FLT3-mutated (FLT3mut) acute myeloid leukemia (AML) but the overall survival (OS) is only approximately 20 % and few patients achieve deep and/ or durable response. We retrospectively analyzed 29 R/R FLT3mut AML patients treated on triplet regimens (gilteritinib+ venetoclaxï¼»VEN] +azacitidineï¼»AZA]). Nineteen patients (65.5 %) had received prior FLT3 inhibitor therapy. The modified composite complete remission (mCRc) rate was 62.1 % (n = 18; CR, 4/29,13.8 %; CRi, 6/29, 20.7 %; MLFS, 8/29, 27.6 %). Among 18 patients achieved mCRc, FLT3-PCR negativity was 94.4 % (n=17), and flow-cytometry negativity was 77.7 % (n=14). The mCRc rate was 70 % (n=7) in 10 patients without prior FLT3 TKI exposure and 57.8 % (n=11) in 19 patients with prior FLT3 TKI exposure (P=0.52). At the end of the first cycle, the median time to ANC > 0.5× 109/L was 38 days and platelet > 50× 109/L was 31 days among responders, but 60-day mortality was 0 %. The estimated 2-year OS was 60.9 % for all R/R FLT3mut patients. The 1-year OS was 80 % and 58.8 % in patients without and with prior FLT3 TKI exposure, respectively (P=0.79). The estimated 2-year OS was 62 % in 19 (65.5 %) patients who received allo-HSCT after triplet therapy and 37 % in 10 patients who did not receive allo-HSCT (P=0.03). In conclusion, triplet therapy with gilteritinib, VEN, and AZA is effective and safe and an excellent frontline option for R/R FLT3mut AML.

Gilteritinib Reduces FLT3 Expression in Acute Myeloid Leukemia Cells.

Acute myeloid leukemia (AML) is a genetically diverse and challenging malignancy, with mutations in the FLT3 gene being particularly common and deleterious. Gilteritinib, a potent FLT3 inhibitor, has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of relapsed/refractory AML with FLT3 mutations. Although gilteritinib was developed based on its inhibitory activity against FLT3 kinase, it is important to understand the precise mechanisms of its antileukemic activity in managing drug resistance and discovering biomarkers. This study was designed to elucidate the effect of gilteritinib on the FLT3 expression level. The results showed that gilteritinib induced a dose-dependent decrease in both FLT3 phosphorylation and expression. This reduction was particularly pronounced after 48 h of treatment. The decrease in FLT3 expression was found to be independent of changes in FLT3 mRNA transcription, suggesting post-transcriptional regulatory mechanisms. Further studies were performed in various AML cell lines and cells with both FLT3 wild-type and FLT3 mutant exhibited FLT3 reduction by gilteritinib treatment. In addition, other FLT3 inhibitors were evaluated for their ability to reduce FLT3 expression. Other FLT3 inhibitors, midostaurin, crenolanib, and quizartinib, also reduced FLT3 expression, consistent with the effect of gilteritinib. These findings hold great promise for optimizing gilteritinib treatment in AML patients. However, it is important to recognize that further research is warranted to gain a full understanding of these mechanisms and their clinical implications in the context of FLT3 reduction.

Gilteritinib overcomes primary resistance to venetoclax in a patient with FLT3 wild-type refractory/relapsed AML: Case report and exploration of possible mechanisms.

Venetoclax, a selective BCL-2 inhibitor, has shown superior efficacy in the treatment of AML. Nevertheless, some AML patients with AML1-ETO respond poorly to venetoclax treatment. In this report, a relapsed/refractory (R/R) venetoclax resistant AML1-ETO positive AML patient showed rapid tumor regression after combination therapy with gilteritinib and venetoclax. Additional laboratory findings indicated that the combined impact of the two drugs may be associated with the induction of the integrated stress response. This case presents a novel therapeutic approach for the treatment of FLT3 wild-type RR, AML1-ETO AML patients who have primary resistance to venetoclax.

Discovery of NFκB2-Coordinated Dual Regulation of Mitochondrial and Nuclear Genomes Leads to an Effective Therapy for Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) has a poor survival rate for both pediatric and adult patients due to its frequent relapse. To elucidate the bioenergetic principle underlying AML relapse, we investigated the transcriptional regulation of mitochondrial-nuclear dual genomes responsible for metabolic plasticity in treatment-resistant blasts. Both the gain and loss of function results demonstrated that NFκB2, a noncanonical transcription factor (TF) of the NFκB (nuclear factor kappa-light-chain-enhancer of activated B cells) family, can control the expression of TFAM (mitochondrial transcription factor A), which is known to be essential for metabolic biogenesis. Furthermore, genetic tracking and promoter assays revealed that NFκB2 is in the mitochondria and can bind the specific "TTGGGGGGTG" region of the regulatory D-loop domain to activate the light-strand promoter (LSP) and heavy-strand promoter 1 (HSP1), promoters of the mitochondrial genome. Based on our discovery of NFκB2's novel function of regulating mitochondrial-nuclear dual genomes, we explored a novel triplet therapy including inhibitors of NFκB2, tyrosine kinase, and mitochondrial ATP synthase that effectively eliminated primary AML blasts with mutations of the FMS-related receptor tyrosine kinase 3 (FLT3) and displayed minimum toxicity to control cells ex vivo. As such, effective treatments for AML must include strong inhibitory actions on the dual genomes mediating metabolic plasticity to improve leukemia prognosis.

[Efficacy and safety of gilteritinib-based combination therapy bridging allo-HSCT in relapsed or refractory acute myeloid leukemia patients with positive FLT3-ITD mutation].

Objective: This study aims to evaluate the safety and effectiveness of gilteritinib (Gilt) -based combination therapy bridging allo-HSCT for FLT3-ITD(+) R/R AML. Additionally, it aims to assess the impact of Gilt maintenance therapy on the prognosis of patients after allo-HSCT. Methods: The clinical data of 26 patients with FLT3-ITD(+) R/R AML treated at the First Affiliated Hospital of Soochow University from August 2019 to January 2023 were retrospectively analyzed. The analysis included an assessment of the composite complete remission rate (CRc), overall survival (OS) time, disease-free survival (DFS) time, and adverse events experienced by all enrolled patients. Results: A total of 26 patients with FLT3-ITD(+) R/R AML were enrolled, including 14 men and 12 women with a median age of 38 (18-65) years. A total of 18 cases were refractory, and eight cases were relapsed. The curative effect evaluation conducted between 14 and 21 days showed that the complete remission (CR) rate was 26.9% (7/26), the CR with hematology incomplete recovery was 57.7% (15/26), and the partial response (PR) rate was 7.7% (2/26). The CRc was 84.6% (22/26), and the minimal residual disease (MRD) negativity rate was 65.4%. The 12 month cumulative OS rate for all patients was 79.0%, and the 24 month cumulative OS rate was 72.0%. The median OS time was not determined. The median follow-up time was 16.0 months. Among the patients who responded to treatment, the 12 month cumulative DFS rate was 78.0%, and the 24 month cumulative DFS rate was 71.0%. The median DFS time was not determined. Patients who received allo-HSCT had a median OS time that was significantly longer than those who did not receive allo-HSCT (3.3 months, 95%CI 2.2-4.3 months, P=0.005). The median OS time of patients with or without Gilt maintenance therapy after allo-HSCT was not determined, but the OS time of patients with Gilt maintenance therapy after allo-HSCT treatment was longer than that of patients without Gilt maintenance therapy after allo-HSCT treatment (P=0.019). The FLT3-ITD mutation clearance rate in this study was 38.5%, and the median OS time of patients with FLT3-ITD mutation clearance was not determined but was significantly longer than the median OS of patients without FLT3-ITD mutation clearance (15.0 months; P=0.018). The most common grade 3 and above hematological adverse events of Gilt-based combination therapy included leukopenia (76.9%), neutropenia (76.9%), febrile neutropenia (61.5%), thrombocytopenia (69.2%), and anemia (57.7%). One patient developed differentiation syndrome during oral Gilt maintenance therapy after allo-HSCT treatment, but his condition improved after treatment. Conclusion: The Gilt-based combination therapy is highly effective in treating FLT3-ITD(+) R/R AML. It demonstrates a high CRc, MRD negativity rate, and rapid onset, leading to a significant improvement in patients' survival. Furthermore, the clearance rate of FLT3-ITD mutation is notably high. Additionally, implementing bridging allo-HSCT and Gilt maintenance therapy after allo-HSCT treatment has considerably enhances patients' survival. Closely monitoring and managing any adverse event that may occur during treatment are crucial.

The safety and efficacy of the re-administration of gilteritinib in a patient with FLT3-mutated R/R AML with CNS relapse: a case report.

FLT3-ITD is a type of poor prognostic factors in acute myeloid leukemia (AML) disease. Gilteritinib, the second-generation FLT3 tyrosine kinase inhibitor, improved the overall survival of patients with relapsed/refractory FLT3-mutated AML in the ADMIRAL phase III trial. However, few data are available on the efficacy and safety of gilteritinib-based therapy for FLT3-mutated AML with central nervous system (CNS) involvement. We performed gilteritinib to treat a patient with CNS relapsed AML after allogeneic hematopoietic stem cell transplantation. The positive antileukemic effect of gilteritinib may bring new hope for the treatment of FLT3-mutated AML with CNS relapse.

Metformin synergizes with gilteritinib in treating FLT3-mutated leukemia via targeting PLK1 signaling.

Fms-like tyrosine kinase 3 (FLT3) mutations, present in over 30% of acute myeloid leukemia (AML) cases and dominated by FLT3-internal tandem duplication (FLT3-ITD), are associated with poor outcomes in patients with AML. While tyrosine kinase inhibitors (TKIs; e.g., gilteritinib) are effective, they face challenges such as drug resistance, relapse, and high costs. Here, we report that metformin, a cheap, safe, and widely used anti-diabetic agent, exhibits a striking synergistic effect with gilteritinib in treating FLT3-ITD AML. Metformin significantly sensitizes FLT3-ITD AML cells (including TKI-resistant ones) to gilteritinib. Metformin plus gilteritinib (low dose) dramatically suppresses leukemia progression and prolongs survival in FLT3-ITD AML mouse models. Mechanistically, the combinational treatment cooperatively suppresses polo-like kinase 1 (PLK1) expression and phosphorylation of FLT3/STAT5/ERK/mTOR. Clinical analysis also shows improved survival rates in patients with FLT3-ITD AML taking metformin. Thus, the metformin/gilteritinib combination represents a promising and cost-effective treatment for patients with FLT3-mutated AML, particularly for those with low income/affordability.

Ningetinib, a novel FLT3 inhibitor, overcomes secondary drug resistance in acute myeloid leukemia.

BACKGROUND: FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is a common mutation type in acute myeloid leukemia (AML) and is usually associated with poor patient prognosis. With advancements in molecular diagnostics and the development of tyrosine kinase inhibitors (TKI), the overall survival (OS) of AML patients with FLT3-ITD mutations has been prolonged to some extent, but relapse and drug resistance are still substantial challenges. Ningetinib is a novel TKI against various kinases in relation to tumour pathogenesis and is undergoing clinical trials of lung cancer. In this study, we explored the antitumor activity of ningetinib against AML with FLT3 mutations both in vivo and in vitro. METHODS: Cell proliferation assays were performed in AML cell lines and Ba/F3 cells expressing various FLT3 mutations to validate the antileukemic activity of ningetinib in vitro. Immunoblot assays were used to verify the effect of ningetinib on the FLT3 protein and downstream pathways. Molecular docking and CETSA were used to validate the interaction of ningetinib with target proteins. The survival benefit of ningetinib in vivo was assessed in Ba/F3-FLT3-ITD-, MOLM13, Ba/F3-FLT3-ITD-F691L-, MOLM13-FLT3-ITD-F691L-induced leukemia mouse models. We also used patient-derived primary cells to determine the efficacy of ningetinib. RESULTS: Ningetinib inhibited cell proliferation, blocked the cell cycle, induced apoptosis and bound FLT3 to inhibit its downstream signaling pathways, including the STAT5, AKT and ERK pathways, in FLT3-ITD AML cell lines. In the mouse models with FLT3-ITD and FLT3-ITD-F691L mutation, ningetinib showed superior anti-leukemia activity to existing clinical drugs gilteritinib and quizartinib, significantly prolongating the survival of mice. In addition, ningetinib exhibited activity against patient-derived primary cells harboring FLT3-ITD mutations. CONCLUSION: Overall, our study confirmed the therapeutic role of ningetinib in AML with FLT3-ITD mutations, providing a potential new option for clinically resistant patients.

Gilteritinib with or without venetoclax for relapsed/refractory FLT3-mutated acute myeloid leukaemia.

Patients with FLT3-mutated acute myeloid leukaemia (AML) that relapse or are refractory (R/R) to intensive induction have poor outcomes. Gilteritinib has recently become standard-of-care for patients with R/R FLT3-mutated AML. We investigated whether adding venetoclax to gilteritinib (gilt-ven) improves outcomes as compared with gilteritinib monotherapy. We included patients treated with gilteritinib (n = 19) and gilt-ven (n = 17) for R/R AML after intensive chemotherapy. Gilteritinib and gilt-ven groups did not differ in terms of mCRc rates (53% and 65%, p = 0.51) and realization of allogeneic haematopoietic stem-cell transplantation (HSCT, 47% and 35%, p = 0.5). Overall survival (OS) was comparable between groups, although a trend towards better OS was seen with gilt-ven (12-month OS 58.8% [95% CI 39.5%-87.6%]) versus gilteritinib (42.1% [95% CI 24.9%-71.3%] for gilteritinib). Early salvage with gilt-ven versus any other gilteritinib-based approach was associated with the best outcome (p = 0.031). Combination therapy was associated with increased haematological toxicity. In summary, gilt-ven did not improve remissions or HSCT-realization rates in patients with R/R FLT3-mutated AML as compared with gilteritinib and was associated with increased haematological toxicity. Although OS did not differ, a trend towards better survival was suggested with gilt-ven and a survival benefit was shown for gilt-ven approach when sequenced early for salvage.

[Acute myeloid leukemia with central nervous system involvement successfully treated with gilteritinib].

A 69-year-old woman was referred to our hospital due to hyperleukocytosis. We diagnosed acute myeloid leukemia and started induction therapy with the CAG regimen (aclarubicin, cytarabine and filgrastim). However, the patient was refractory to the initial treatment and developed quadriplegia, and a cerebrospinal fluid (CSF) test showed elevated blasts. We then performed intrathecal chemotherapy, and the number of blasts in CSF gradually decreased. But only two cycles of intrathecal therapy were possible due to severe methotrexate-induced mucositis. The leukemia cells had fms-like kinase 3-internal tandem duplication (FLT3-ITD), so we started treatment with oral gilteritinib. The patient then achieved hematological complete remission. Her paralysis was also resolving, and the CSF was clear of blasts for more than 6 months. Some reports show that gilteritinib may penetrate the CNS, and this case also supports the effectiveness of gilteritinib on CNS leukemia.

Sweet syndrome induced by FLT3 inhibitors: case report and literature review.

BACKGROUND: Acute febrile neutrophilic dermatosis, also commonly referred to as Sweet syndrome, is often associated with tumors, infections, immune disorders and medications. FLT3 inhibitor-induced Sweet syndrome is a rare complication. METHODS AND RESULTS: We report a patient with relapsed and refractory acute monocytic leukemia harboring high-frequency FLT3-ITD and DNMT3a mutations. The FLT3 inhibitor gilteritinib was administered for reinduction therapy after failure of chemotherapy with a combination of venetoclax, decitabine, aclarubicin, cytarabine and granulocyte colony-stimulating factor. The leukemia patient achieved remission after 1 month of treatment. However, Sweet syndrome induced by gilteritinib, which was confirmed by skin biopsy, developed during induction therapy. Similar cases of Sweet syndrome following FLT3 inhibitor therapy for acute myeloid leukemia were reviewed. CONCLUSION: Attention should be given to this rare complication when FLT3 inhibitors are used for acute myeloid leukemia therapy, and appropriate treatments need to be administered in a timely manner.

[Fulminant Clostridioides difficile infection during treatment with FLT3 inhibitor for acute myeloid leukemia].

An 80-year-old man with FLT3-TKD mutation-positive acute myeloid leukemia (AML) relapsed during consolidation therapy with venetoclax/azacitidine and was started on gilteritinib as salvage therapy. On the day after treatment initiation, febrile neutropenia was observed, but the fever resolved promptly after initiation of antimicrobial therapy. On the fifth day after completion of antimicrobial therapy, the patient experienced fever and watery diarrhea over 10 times a day, and a diagnosis of Clostridioides difficile infection (CDI) was made based on stool examination. The patient was treated with intravenous metronidazole, but renal dysfunction, hypotension, and hypoxemia developed, and a CT scan showed pleural and intraperitoneal effusion, significant intestinal wall thickening, and intestinal dilatation. Fidaxomicin was started under general monitoring in the intensive care unit and response was achieved. The patient was discharged from the intensive care unit on the 18th day after the onset of CDI. We report this case not only due to the rarity of fulminant CDI during AML treatment, but also because it is a valuable example of effective treatment of fulminant CDI with fidaxomicin.

Expansion of targeted degradation by Gilteritinib-Warheaded PROTACs to ALK fusion proteins.

Proteolysis targeting chimeras (PROTACs) induce the ubiquitination and subsequent proteasomal degradation of targeted proteins. Numerous PROTACs have emerged as promising drug candidates for various disease-related proteins. This study investigates PROTACs targeted to degrade anaplastic lymphoma kinase (ALK) fusion proteins, which are implicated in diseases such as anaplastic large cell lymphoma and non-small cell lung cancer. We recently reported the development of a gilteritinib-warheaded PROTAC to target and degrade the Fms-like tyrosine kinase 3 (FLT3) protein. Gilteritinib is a tyrosine kinase inhibitor that targets FLT3, and recent studies have revealed that it also functions as an ALK inhibitor. We conducted a structure-activity relationship (SAR) study and expanded the range of target proteins for gilteritinib-warheaded PROTACs to include echinoderm microtubule-associated protein-like 4 (EML4)-ALK and nucleophosmin (NPM)-ALK, in addition to FLT3. Our SAR study utilized three types of ligands for E3 ligase- inhibitor of apoptosis protein (IAP), cereblon (CRBN), and von Hippel-Lindau (VHL)- in the PROTAC designs and we observed varied efficacy in the degradation of target proteins. The CRBN-based PROTAC effectively reduced the protein expression of FLT3, EML4-ALK, and NPM-ALK. The IAP-based PROTAC reduced expression of both FLT3 and EML4-ALK proteins but not that of NPM-ALK, while the VHL-based PROTAC was ineffective against all target proteins. Several ALK-targeted PROTACs have already been developed using CRBN or VHL as E3 ligase, but this is the first report of an IAP-based ALK degrader. The length of the linker structure utilized in PROTAC also had a significant effect on their efficacy and activity. PROTACs formed with shorter linkers demonstrated an enhanced degradation activity to target proteins compared with those formed with longer linkers. These findings provide valuable insight for the development of effective PROTACs to target and degrade ALK fusion proteins.

Potentiating Gilteritinib Efficacy Using Nanocomplexation with a Hyaluronic Acid-Epigallocatechin Gallate Conjugate.

Acute myeloid leukemia carrying FMS-like tyrosine kinase receptor-3 (FLT3) mutations is a fatal blood cancer with a poor prognosis. Although the FLT3 inhibitor gilteritinib has recently been approved, it still suffers from limited efficacy and relatively high nonresponse rates. In this study, we report the potentiation of gilteritinib efficacy using nanocomplexation with a hyaluronic acid-epigallocatechin gallate conjugate. The self-assembly, colloidal stability, and gilteritinib loading capacity of the nanocomplex were characterized by reversed-phase high-performance liquid chromatography and dynamic light scattering technique. Flow cytometric analysis revealed that the nanocomplex efficiently internalized into FLT3-mutated leukemic cells via specific interactions between the surface-exposed hyaluronic acid and CD44 receptor overexpressed on the cells. Moreover, this nanocomplex was found to induce an eradication of the leukemic cells in a synergistic manner by elevating the levels of reactive oxygen species and caspase-3/7 activities more effectively than free gilteritinib. This study may provide a useful strategy to design nanomedicines capable of augmenting the therapeutic efficacy of FLT3 inhibitors for effective leukemia therapy.

Gilteritinib in combination with venetoclax, low-dose cytarabine and actinomycin D for relapsed or refractory FLT3-mutated acute myeloid leukaemia.

We have conducted a retrospective, single-centre analysis of 20 patients with relapsed or refractory FLT3-mutated acute myeloid leukaemia (FLT3m AML) who received a salvage quadruplet regimen consisting of gilteritinib, venetoclax, low-dose cytarabine and actinomycin D (G-ACTIVE). G-ACTIVE resulted in a 95% (19/20) overall response rate and 75% (15/20) complete remission and complete remission with an incomplete platelet recovery (CR + CRp) rate. Out of 13 transplant-eligible patients, 11 (86%) proceeded to an allogeneic stem cell transplantation. The median overall survival and relapse-free survival after G-ACTIVE were 32 and 12.9 months respectively. The Day 60 mortality rate was 15%.

Treatment of relapsed or refractory FLT-3 acute myelogenous leukemia with a triplet regimen of hypomethylating agent, venetoclax, and gilteritinib.

Relapsed or refractory (R/R) acute myeloid leukemia (AML) with FMS-like tyrosine kinase 3 (FLT3) mutations remains a difficult and hard to treat entity. Gilteritinib is a potent oral FLT-3 inhibitor that improves overall survival in R/R AML, but studies are limited in combining gilteritinib with a hypomethylating agent and venetoclax treatment backbone (HMA-VEN-GILT). Here we report our experience with HMA-VEN-GILT for 22 R/R FLT3 AML patients. HMA-VEN-GILT yielded an ORR of 77.3% (17/22), CR 4.5% (1/22), CRi 13.6% (3/22), MLFS 59.1% (13/22). Median follow-up was 10.4 months with a relapse rate of 29.4% (5/17), median time to relapse of 69 days (range 35-298 days), 6-month overall survival of 84%, and median OS of 10.1 months. Additionally, 36.4% (8/22) of patients proceeded to hematopoietic stem cell transplant. In conclusion, HMA-VEN-GILT for the treatment of R/R FLT3 AML is feasible and can be used as a bridge to allogeneic transplantation.

Gilteritinib-based combination therapy in adult relapsed/refractory FLT3-mutated acute myeloid leukaemia.

Gilteritinib, a potent FMS-like tyrosine kinase 3 (FLT3) inhibitor, was approved for relapsed/refractory (R/R) FLT3-mutated acute myeloid leukaemia (AML) patients but still showed limited efficacy. Here, we retrospectively analysed the efficacy and safety of different gilteritinib-based combination therapies (gilteritinib plus hypomethylating agent and venetoclax, G + HMA + VEN; gilteritinib plus HMA, G + HMA; gilteritinib plus venetoclax, G + VEN) in 33 R/R FLT3-mutated AML patients. The composite complete response (CRc) and modified CRc (mCRc) rates were 66.7% (12/18) and 88.9% (16/18) in patients received G + HMA + VEN, which was higher compared with that in G + HMA (CRc: 18.2%, 2/11; mCRc: 45.5%, 5/11) or G + VEN (CRc: 50.0%, 2/4; mCRc: 50.0%, 2/4). The median overall survival (OS) for G + HMA + VEN, G + HMA and G + VEN treatment was not reached, 160.0 days and 231.0 days. The median duration of remission (DOR) for G + HMA + VEN, G + HMA and G + VEN treatment was not reached, 82.0 days and 77.0 days. Four patients in the G + HMA + VEN group received alloHSCT after remission exhibited prolonged median DOR. The most common grade 3/4 adverse events were cytopenia, febrile neutropenia and pulmonary infection; there were no differences among the three groups. In conclusion, our data demonstrated promising response of G + HMA + VEN combination therapy in R/R FLT3-mutated AML, and it may be considered an effective therapy bridge to transplantation.