Mitoxantrone liposome-based MEA regimen for treatment mixed lineage leukemia-rearranged acute myeloid leukemia: a case series

Introduction

Background

Acute leukemia (AL) with mixed lineage leukemia (MLL) rearrangement is a frequently occurring cytogenetic abnormality, representing 5–10% of AL cases (1). Furthermore, acute myeloid leukemia (AML) harboring MLL rearrangement presents clinical features that include a high degree of malignancy, challenges in achieving remission, a significant risk of relapse, and an unfavorable prognosis. Prognosis varies by MLL fusion partner; KMT2A::MLLT3 cases have relatively better outcomes (2). Hence, it is imperative to promptly achieve remission, followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) for most of this population. However, there is no standardized initial induction regimen for this population, and with anthracycline-containing drugs mostly recommended, the therapeutic outcomes are not entirely satisfactory.

Rationale and knowledge gap

Mitoxantrone liposome (L-MIT) is a liposome-encapsulated anthracycline drug that enhances drug concentration in tumors and reduces cardiac side effects by altering mitoxantrone’s pharmacokinetics and tissue distribution (3,4). At present, there is no report on the treatment of AML with MLL rearrangement using L-MIT combined with etoposide and cytarabine (MEA).

Objective

We retrospectively analyzed a single-center case series of 4 patients with AML with MLL rearrangement treated with the MEA regimen based on L-MIT. We present this article in accordance with the AME Case Series reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-25-19/rc).

Case presentation

Methods

All patients received MEA (L-MIT, 20 mg/m², day 1; etoposide, 100 mg, days 1–5; cytarabine, 100 mg/m², days 1–5) regimen. The L-MIT dose (20 mg/m² on day 1) was selected based on prior studies to ensure efficacy and safety (5,6). In this study, intermediate to high-dose cytarabine was administered after achieving complete remission (CR). If the patient was in partial remission (PR), the original regimen would be continued for re-induction. All procedures performed in this study were approved by the ethics committee of the Affiliated Hospital of Hebei University (No. HDFYLL-KY-2023-152) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patients for publication of this case series and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Case 1

On September 12, 2023, a 59-year-old man presented with fatigue for more than half a month and aggravation with fever for 5 days was admitted to our hospital. The patient had a 5-year history of hypertension and cerebral infarction, both well-controlled with medication. On admission, a physical examination revealed an anemic appearance and petechiae. A blood routine examination showed white blood cell (WBC) 163×10⁹/L, hemoglobin 57 g/L, platelet count (PLT) 17×10⁹/L, and 10% immature cells. Bone marrow (BM) morphology indicated extremely active proliferation, with 41% immature monocytes, raising suspicion of AML(Figure 1A). BM flow cytometry (FCM) (Figure S1) showed immature cells (10.02% of nucleated cells) expressing CD34, CD117, CD13, CD33, HLA-DR, and partial CD2; abnormal monocytes (19.03%) expressed CD13⁺, CD33⁺, CD4⁺, CD11b⁺, partial CD14⁺, CD36⁺, and CD64⁺. Karyotype analysis revealed 46,XY,t(11;19)(q23;p13), with MLL-ELL fusion gene positive and KIT D816V mutation (44.8%). Diagnosis: AML with t(11;19) and KIT mutation. On September 16, 2023, the patient received an MEA regimen. The intravenous infusion proceeded smoothly with mild gastrointestinal reactions. Blood routine examination showed WBC of 0.30×10⁹/L, hemoglobin of 59 g/L, and PLT of 7×10⁹/L, which reached the lowest point. There was no fever, cardiac, liver, or kidney toxicity during periods of myelosuppression. On October 16, 2023, the blood routine returned to normal. BM showed active proliferation with 1% primitive granulocytes and 1% immature monocytes (Figure 1B), achieving CR. FCM (Figure S2) detected no abnormal myeloid precursor cells (<0.01%), and the MLL-ELL fusion gene dropped to 2.952%. Accordingly, the regimen was changed to cytarabine (4 g, q12h, days 1–3) as the first consolidation therapy (October 20, 2023). On November 24, 2023, the blood count was essentially normal, with MRD-negative and MLL-ELL at 0.035%. Subsequently, the patient received the same dose of cytarabine again on November 26, 2023. Re-evaluation on December 26, 2023, showed normal blood count, with MRD-negative and MLL-ELL at 0.000%. Finally, the patient received allo-HSCT in January 2024. Three months post-transplant, the patient remains in CR with a survival of over 11 months.

Figure 1 Histological examination of the patient’s BM. It shows BM morphology before and after treatment, stained with Wright-Giemsa stain at ×1,000 magnification. (A) Case 1 before treatment; (B) Case 1 after treatment; (C) Case 2 before treatment; (D) Case 2 after treatment; (E) Case 3 before treatment; (F) Case 3 after treatment; (G) Case 4 before treatment; (H) Case 4 after treatment. BM, bone marrow.

Case 2

A 36-year-old female was admitted to the hospital on September 6, 2023, with fatigue for two months. A blood routine examination showed WBC 103.20×10⁹/L, hemoglobin 52 g/L, and PLT 19×10⁹/L. BM morphology (Figure 1C) revealed extremely active proliferation with 10% primitive granulocytes, 19% immature monocytes, and weakly positive peroxidase (POX). FCM (Figure S3) identified 3.21% abnormal myeloid precursor cells (CD13⁺, CD33⁺, CD117⁺) and 48.68% abnormal monocytes (AML-M5b phenotype). Molecular Biology showed a positive MLL-ELL fusion gene with FLT3-ITD (low frequency) and WT1 T382D mutations. Therefore, the patient was diagnosed with AML accompanied by t(11;19), FLT3-ITD, and WT1 mutations. On September 12, 2023, the patient received the MEA therapy. Throughout the periods of myelosuppression, the blood count reached its minimum, with WBC levels at 0.41×10⁹/L, hemoglobin measuring 60 g/L, and PLT at 3×10⁹/L, complicated by febrile infection (pulmonary and skin Staphylococcus aureus), resolved with anti-infectives. BM showed CR (Figure 1D), FCM MRD <0.01% (Figure S4), MLL-ELL 1.678%. Consequently, the patient received the cytarabine (3.5 g, q12h, days 1–3) as the consolidation therapy on October 15, 2023. Following re-evaluation, the patient’s blood counts normalized and subsequently received allo-HSCT. More than five months after the transplant, the patient is currently in robust health, with a sustained CR post-transplant and a survival of over 11 months.

Case 3

On October 25, 2023, a 66-year-old female patient was hospitalized due to fatigue and poor appetite. Blood routine examination showed WBC at 88.69×10⁹/L, hemoglobin at 59 g/L, and PLT at 24×10⁹/L. BM morphology (Figure 1E) indicated a markedly active degree of proliferation, with immature monocytes accounting for 77%. FCM analysis (Figure S5) revealed that approximately 84.3% of the nucleated cells were abnormal, indicating an AML-M5 immunophenotype characterized by partial CD34⁺, partial CD117⁺, HLA-DR⁺, CD33⁺, limited CD13⁺, partial CD11b⁺, CD15⁺, CD4⁺, partial CD36⁺, CD64⁺, limited CD14⁺, partial CD56⁺, CD85K⁺, and dim CD85J⁺. Chromosome analyses revealed a 46,XY,t(6;11)(q27;q23)[20]. Fusion gene detection revealed a positive MLL-AF6 fusion, and next-generation sequencing (NGS) showed FLT3-ITD at 0.37% (low). Finally, the patient was diagnosed with AML featuring MLL-AF6 positivity and a low-frequency FLT3-ITD mutation. On November 2, 2023, the patient received the MEA regimen. During myelosuppression, the WBC was 0.42×10⁹/L, hemoglobin was 59 g/L, and PLT was 7×10⁹/L, with infectious fevers (pulmonary and facial), resolved with treatment. On November 31, 2023, blood counts recovered; BM showed CR (Figure 1F) while FCM and MRD analysis were not performed for economic reasons. On December 12, 2023, the patient received cytarabine (1.5 g, q12h, days 1–3), and achieved CR after one cycle. Allo-HSCT was not performed due to advanced age and financial limitations. Currently, consolidation treatment is ongoing. At the time of data analysis, the patient still maintains CR, with a survival period of over 10 months.

Case 4

A 45-year-old man was hospitalized on 11 November 2023 with 10 days of fatigue and palpitations. The patient had a 20-year history of viral hepatitis B (HBV), requiring oral antiviral medication. The blood routine examination revealed WBC at 165.84×10⁹/L, hemoglobin at 80 g/L, and PLT at 66×10⁹/L. Besides, HBV-DNA was negative. The BM analysis (Figure 1G) showed marked cellular activity, with 66% of primitive cells. BM FCM (Figure S6) observed abnormal cells with 86.40% nuclear cell presence, exhibiting strong CD33 expression and positivity for CD17, CD15, CD123, CD64, CD4, CD38, and partial expression of HLA-DR, CD11b, and CD13, which were consistent with AML phenotype. Chromosomes showed 46,XY,der(9)t(9;11)(p22;q23)t(8;9)(q12;q34),der(11)t(9;11)[20]. Additionally, the MLL-AF9 fusion gene was confirmed. NGS analysis showed the following mutations: FLT3-TKD p.D835 at 21.3%, p.F594I at 1.8%, and TP53 p.R175H at 9.8%. The patient was ultimately diagnosed with AML featuring MLL-AF9 positivity, FLT3-TKD and TP53 mutation, and concomitant HBV infection. On November 15, 2023, the patient received induction chemotherapy with the MEA regimen. During the treatment, the patient experienced intermittent fever and received aggressive anti-infection therapy. One week after discontinuing therapy, BM examination revealed significantly reduced cell proliferation, with only 2% primitive granulocytes, indicating post-treatment myelosuppression. On December 8, 2023, the blood routine showed a WBC of 2.75×10⁹/L, hemoglobin of 109 g/L, and PLT of 147×10⁹/L. Meanwhile, the BM revealed 8% primitive monocytes, and the patient achieved a PR. Subsequently, the treatment was changed to MEA plus chidamide (L-MIT, 40 mg, day 1; etoposide, 100 mg, days 1–5; cytarabine, 100 mg, q12h, days 1–5; chidamide, 20 mg, 2/week) regimen. On January 21, 2024, the blood counts returned to normal, and the BM (Figure 1H) revealed increased cell activity with 4% primitive monocytes. Finally, the patient achieved a CR. The patient was treated with sequential allo-HSCT. Now three months after transplantation, the patient is generally in good condition, for CR, survival period of 9 months so far.

Discussion

In the present study, we present findings from four cases of AML harboring MLL rearrangement treated with the L-MIT-based MEA regimen. After one treatment cycle, three patients achieved CR, and one patient achieved PR, resulting in an overall response rate of 100%.

The MLL gene, also known as the KMT2A gene, is situated on chromosome 11q23, and chromosomal translocations at this site result in MLL rearrangements, leading to the loss of regulatory control over downstream target genes (7,8). Multiple studies have shown that adults with MLL-rearranged AML were most often observed in acute monocytic leukemia (M5), with high WBC counts at disease onset and a poor prognosis. The patient’s initial WBC count, whether a CR was achieved within one cycle, and whether an allo-HSCT was performed were independent prognostic factors influencing patient survival (2,8,9). Currently, there is no standardized effective induction regimen for patients with MLL rearrangements, but the majority of existing regimens incorporate anthracyclines. Recently, a study had shown that the MEA (mitoxantrone, etoposide, and cytarabine) regimen was notably more effective for patients with 11q23/MLL rearranged AML, making it considered the preferred treatment choice for this population (10).

Nevertheless, conventional mitoxantrone was often associated with BM and cardiac toxicity, restricting its usage. In contrast, L-MIT represented an improved drug formulation that selectively accumulated in tumor tissues and provided sustained drug release, thereby exerting anti-tumor activity. Meanwhile, it reduced damage to normal tissues and decreased the cardiac toxicity of anthracycline drugs. L-MIT’s liposomal delivery reduced gastrointestinal toxicity, with only mild nausea reported (11). Furthermore, preclinical and clinical studies had demonstrated a lower incidence of cardiovascular events and myelosuppression with L-MIT than with mitoxantrone. L-MIT’s tumor targeting via enhanced permeability and retention (EPR) effects in tumors enhances intracellular drug concentration, circumventing transporter-mediated resistance (4,12). In the present study, all four patients received the modified MEA (L-MIT, etoposide, cytarabine) regimen by replacing mitoxantrone with L-MIT. Encouragingly, compared to the conventional mitoxantrone-based MEA regimen (10), our patients experienced an enhanced remission rate with the L-MIT-based MEA regimen. The cell morphology of four patients showed a monocyte phenotype, with WBC counts >100×10⁹/L in three cases. After one treatment course, three patients achieved negative results in BM flow cytometry minimal residual disease (MRD) and exhibited varying degrees of MLL gene reduction. Another patient only achieved PR, possibly attributed to the complex karyotype with concurrent TP53 and FLT3-TKD mutations in this case. MLL-AF6 fusion and FLT3-ITD mutation, associated with chemoresistance, may have contributed to the lower response in Case 3. Moreover, there were fewer adverse events, with low organ toxicity (12), particularly cardiotoxicity, and myelosuppression was well tolerated, lasting 14–21 days in all cases.

When compared with daunorubicin (DNR), L-MIT’s liposomal formulation reduces cardiotoxicity (0% vs. 15% with DNR) (3) and enhances tumor targeting via EPR effects. Venetoclax shows lower response rates (67%) in MLL-rearranged AML due to HOX/MEIS1 activation (13). Menin inhibitors, which disrupt Menin-KMT2A interactions and target HOX/MEIS1 in MLL-rearranged AML, represent a promising future direction with ongoing clinical trials (14). The high response rate (3 CR, 1 PR) in our study aligns with the mechanism of L-MIT, and surpasses historical data [35–40% CR with “3+7”(1), 67% with venetoclax (13)], suggesting that L-MIT’s targeted delivery likely enhances efficacy.

Conclusions

These findings not only highlight the potential effectiveness of the L-MIT-based MEA regimen in patients with MLL-rearranged AML but also offer hope for improved outcomes in this population. The next steps include expanding the sample size and conducting randomized controlled trials (RCTs). Further investigation and validation of these results may pave the way for more tailored and successful treatments in the future.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the AME Case Series reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-25-19/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-25-19/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-25-19/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were approved by the ethics committee of Affiliated Hospital of Hebei University (No. HDFYLL-KY-2023-152) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patients for publication of this case series and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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