Combination of Liposomal Mitoxantrone, Venetoclax, Homoharringtonine, and Olverembatinib (HQP1351) (MVHO) in Pediatric Patients with Refractory or Relapsed Acute Myeloid Leukemia (AML): Case Series

Introduction: AML accounts for up to 25% of all pediatric acute leukemias. Although overall survival (OS) in pediatric AML has increased to 70% in recent years because of enhanced risk stratified intensive chemotherapy and hematopoietic stem cell transplantation. Unfortunately, more than 30% of patients experience relapse. Further increase intensity of chemotherapy was proven unfeasible for the toxicity and treatment related mortality. Hence, specific targeted therapy has been being explored to treat pediatric AML in recent decade. Because of the heterogeneity of AML and multiple pathways involved in leukemogenesis, single agent targeting one pathway was effective in limited cases. In this study, we designed a regimen to block multiple pathways with combination of Liposomal Mitoxantrone, Venetoclax, Homoharringtonine, and Olverembatinib (MVHO) to investigate its efficacy and safety in treatment of refractory or relapsed AML.

Methods: We enrolled patients with relapsed or newly diagnosed AML with poor prognosis with adverse molecular abnormalities, such as NUP98 rearrangements, FUS::ERG, CBFA2T3::GLIS2, and del7/7q, who did not achieve complete remission (CR) after first-line chemotherapy. Patients were administered the MVHO regimen, which included 1 dose of liposome mitoxantrone 8mg/m²; venetoclax, 300 to 350mg/m² once daily, from day1 to day 7, (dose escalation for up to 3days from 50mg/m² if high tumor burden occur); homoharringtonine 2mg/m² once daily, from day1 to day 7; and Olverembatinib (HQP1351) 20-30mg/m² every other day, for 4 doses from day 1 to day 7. Prophylactic oral levofloxacin and posaconazole were administered from day 8 through whole myelosuppression period of every cycles. One cycle (28-35 days, depending on hematopoietic recovery) response, total response, cumulative incidence of relapse (CIR), event-free survival (EFS), hematologic toxicity, and infection during this study were evaluated.

Results: A total of 18 patients were enrolled (9 boys and 9 girls), with a median (range) age of 7.3 (4 months-13 years) years, and underwent a total of 27 cycles of MVHO therapy. Half of the patients underwent 1 cycle and the other half, 2 cycles. Per French-American-British (FAB) classification criteria: patients had myelodysplastic syndrome (n = 2); mixed-phenotype acute leukemia (n = 2); and AML subtypes M7 (n = 4), M2 (n = 4), M5 (n = 4), M4 (n = 1), and M0 (n = 1). The median (range) follow-up time was 131 (26-256) days. After cycle one, the objective response rate (ORR, CR plus CR with incomplete hematological recovery [Cri] and partial response [PR]) was 94.4% (17/18), and the remission rate (CR + Cri) was 72.2% (13/18). The total ORR and remission rate before transplantation were 83.3% (15/18) and 66.7% (12/18), respectively. 8 patients among them reached minimum residual disease (MRD) negative remission. For 6 patients with relapsed AML, the ORR and one cycle remission rate was 100% and 66.7%, respectively. A total of 3 patients discontinued because of no response or disease progression, and 12 patients underwent hematopoietic stem cell transplantation (HSCT), after which 1 patient experienced relapse. Remaining 2 patients are being underwent further MVHO cycles. The CIR was 6.7% (1/15). The 8-month mean (± SD) EFS was 60.1% (±19%) and the OS, 100%. Among 26 cycles of MVHO treatment, there were no associated fatal infections or bleeding events. There were 21 episodes of breakthrough infection occurred in 26 cycles of MVHO. There was 1 case of septic shock, and the incidence of ≥grade 3 infection was 80.7%, which included pneumonia, bloodstream infection. Common grade 4 treatment-related adverse events were neutropenia, which was experienced by 100% of patients, and grade 4 thrombocytopenia, which was experienced by 46.1%. Most notably, platelets were stably normal in nearly 20% (5/26) MVHO cycles.

Conclusions: MVHO therapy was effective and reasonably well tolerated in pediatric patients with refractory or relapsed AML, suggesting that it may comprise a suitable first-line treatment option for pediatric AML patients.