Mixed-phenotype acute leukemia (MPAL) is a rare hematological malignancy that accounts for approximately 2%–5% of all leukemia cases [1]. It is associated with poor prognosis, and there are currently no standardized treatment guidelines for it. Recent evidence supports the use of acute lymphoblastic leukemia (ALL)-like induction therapy, followed by allogeneic stem cell transplantation during the first remission in most adults [2–4].
The presence of the Philadelphia chromosome (Ph) is generally considered a poor prognostic factor for MPAL. However, recent studies have shown that in the tyrosine kinase inhibitor (TKI) era, the prognosis in cases of Ph-positive (Ph +) MPAL is better than that in cases of Ph-negative MPAL [5], achieving outcomes comparable to those of typical Ph + B-ALL in terms of complete remission (CR) and 5-year survival rates [6].
Venetoclax is a novel BCL-2 inhibitor that is widely used to treat hematological malignancies. Preclinical and clinical studies have shown the efficacy of combining TKIs with venetoclax and corticosteroids in the management of Ph + ALL [7, 8]. Furthermore, the successful use of TKIs plus venetoclax in the management of Ph + MPAL has also been reported [9, 10].
Olverembatinib, a third-generation TKI, has shown promising efficacy and safety in patients with de novo Ph + ALL. Notably, the combination of olverembatinib, venetoclax, and dexamethasone resulted in a complete molecular remission (CMR) rate of 70% after a single treatment cycle [11]. Here, we report five cases of de novo Ph + MPAL treated with the venetoclax, olverembatinib, and prednisone (VOP) regimen.
Between 2022 and 2025, three patients aged ≥ 60 years and two younger patients with B/myeloid MPAL and BCR::ABL1 rearrangement who declined intensive chemotherapy were treated with the VOP regimen (venetoclax 100 mg on day 1, 200 mg on day 2, and 400 mg on days 3–28; olverembatinib 40 mg once every other day; and prednisone 1 mg/kg once daily on days 1–21) (Fig. 1). For patients receiving CYP3A inhibitors (e.g., voriconazole) concomitantly, dose adjustments were performed as follows: Venetoclax was reduced to 10 mg on day 1, 20 mg on day 2, 50 mg on day 3, and 100 mg on days 4–28, while olverembatinib was reduced to 20 mg every other day.
Treatment response was assessed at the completion of the first cycle (days 28–42), according to the 2022 European LeukemiaNet criteria [12]. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) was recommended upon achieving CR. If allo-HSCT could not be performed, the patients received consolidation therapy comprising 6–8 cycles of the VOP regimen (venetoclax 400 mg on days 1–28 or days 1–14; olverembatinib 40 mg every other day; and prednisone 1 mg/kg once daily on days 1–14).
DNA sequencing was performed using a targeted gene panel (Supplementary Table 1), and whole-transcriptome RNA sequencing was used to detect gene fusions. Measurable residual disease (MRD) was evaluated using multiparameter flow cytometry (MFC-MRD) with a minimum sensitivity of 0.01%. Molecular monitoring of BCR::ABL1 was conducted using quantitative real-time polymerase chain reaction.
CMR was defined as undetectable BCR::ABL1 transcripts with ≥ 100,000 ABL control copies detected. Major molecular remission (MMR) was defined as a ≥ 3-log reduction in BCR::ABL1 transcript levels from baseline, without meeting the criteria for CMR. Adverse events (AEs) were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0.Fig.
1Clinical outcomes. A Details of the induction course. B Details of the consolidation course.
C Clinical outcomes of the five patients with de novo Ph + MPAL treated using the VOP regimen. Ph + , Philadelphia Chromosome–positive; MPAL, mixed-phenotype acute leukemia; VOP, venetoclax, olverembatinib, and prednisone. * Venetoclax was administered to patients #3, #4, and #5 for 14 days
The cohort included four men and one woman, with a median age of 61 years (range: 21–69 years). The median white blood cell count, hemoglobin concentration, and platelet count were 48.9 × 109/L (range: 5.83–264.1 × 109/L), 71 g/L (range: 46–120 g/L), and 103 × 109/L (range: 18–184 × 109/L), respectively. RUNX1 mutations were detected in three patients.
The other identified mutated genes were ZNF382, JAK3, ASXL1, and BCORL1. Additionally, IKZF1 deletion was detected in one patient (Table 1). Three patients harbored the BCR::ABL1 P210 transcript, whereas the remaining two harbored the P190 transcript.
No other gene fusions were detected. Table 1Characteristics and outcomes of individual patients with Ph + MPAL treated with VOP regimenPatient NoGender/Age (year)WBC(×109 /L)/HB(g/L)/PLT(×109Type of BCR::ABL1 fusionCytogeneticsGene mutationMorphologic responseFlow-MRDBest Molecular response (cycles of VOP)Follow-up#1F/6422.2/71/129P21046,XX,t(9;22)(q34;q11)[10]RUNX1CRNegativeCMR(1 cycle)Died of pneumonia during CR#2M/69264.14/46/18P21046,XY,t(9;22)(q34;q11)[9]/47,idem, + 22[1]BCORL1/RUNX1CRNegativeMMR (2 cycles)Died of pneumonia during CR#3M/215.83/80/103P19046,XY,−5,t(9;22), + r [5]/47,idem, + der(22)t(9;22)[1]/46,XY,−7*2,t(9;22)(q34;q11), + 2mar[1]/45,XY,−1,−5,t(9;22)(q34;q11),−15, + 2mar[1]/46,XY[4]ZNF382/JAK3/RUNX1/IZKF1delCRNegativeMMR (2 cycles)In continuous CMR after HSCT#4M/61152.73/61/68P21045,XY,−7,t(9;22)(q34;q11)[6]/45,sl,add(2)(p13),del(11)(q23)[2]/45,sl,add(2)(q25),del(11)(q23)[1]/47,XY,del(3)(p13), + mar[1]/46,XY[5]ASXL1CRNegativeMMR (2 cycles)In continuous CMR after HSCT#5M/5448.9/120/184P19045,XY,−7,t(9;22)(q34;q11)[2]/46,idem, + r[4]/46,XY[4]/CRNegativeCMR(1 cycle)In continuous CMR after HSCTAbbreviation CR Complete remission, CMR Complete molecular remission, MMR Major molecular remission, HSCT Hematopoietic stem cell transplantation
All five patients achieved CR following the initial induction therapy and tested negative for MFC-MRD. Patients #1 and #5 achieved CMR after induction therapy, whereas the remaining three patients achieved MMR after two cycles. Unfortunately, patient #1 died because of severe pneumonia during the third cycle of VOP treatment, 4 months after treatment initiation, despite being in remission.
Patient #2 died owing to pneumonia after six cycles of VOP treatment, 12 months after treatment initiation, also while in remission. At the last follow-up in May 2026, the median follow-up period for the entire cohort was 15.5 months. Patients #3, #4, and #5 remained in CMR after allo-HSCT.
No tumor lysis syndrome or early death occurred during induction therapy. The common AEs are summarized in Supplementary Table 2. Cytopenia was the most frequently observed symptom.
All five patients experienced grade 3–4 neutropenia and grade 4 anemia during continuous treatment; however, none developed febrile neutropenia. The times to neutrophil recovery (≥ 0.5 × 10⁹/L) were 7, 2, 8, and 7 days for patients #1, #3, #4, and #5, respectively. The corresponding platelet recovery times were 12, 5, 8, and 6 days, respectively.
After hematological recovery, these patients were discharged and continued treatment at home. Patient #2 had preexisting pneumonia before induction and was treated with voriconazole, necessitating a dose adjustment for venetoclax. Consequently, the neutrophil and platelet recovery in this patient was prolonged to 34 and 31 days, respectively.
Regarding non-hematological toxicities, patient #1 developed grade 3 hypofibrinogenemia, pleural effusion, and heart failure during treatment. Patient #5 also experienced grade 3 hypofibrinogenemia, supporting close monitoring of coagulation parameters throughout induction therapy.
During consolidation therapy, patient #1 developed grade 4 neutropenia and thrombocytopenia during the third cycle and subsequently died of pneumonia. Pathogen testing revealed Pneumocystis jirovecii, Cryptococcus neoformans, cytomegalovirus (CMV), influenza A virus, and Stenotrophomonas maltophilia. Patient #2 remained in CR after six cycles, but developed grade 4 neutropenia, grade 3 thrombocytopenia, and invasive pulmonary aspergillosis caused by Aspergillus fumigatus.
Both fatal outcomes were attributed to respiratory failure due to severe pulmonary infection. In response to these life-threatening infectious complications, the venetoclax treatment duration was shortened to 14 days in subsequent consolidation cycles for patients #3, #4, and #5. After this adjustment, none of the three patients experienced grade 4 neutropenia or severe infections.
In previous studies, patients with Ph + MPAL were treated with TKIs plus intensive chemotherapy. The reported first-line CR rates ranged from 81.3% to 100%, and median survival was not reached [6, 13]. In our small cohort, the chemotherapy-free VOP regimen resulted in 100% CR.
This work provides preliminary information on treatment duration and consolidation strategies. A 28-day venetoclax induction cycle was feasible, with no early deaths or severe infections during the induction period. Hematopoietic recovery was also relatively rapid in four of the five patients.
However, two patients died from pulmonary infections associated with grade 4 neutropenia during consolidation. These complications may have been related to the continuous 28-day venetoclax dosing. Therefore, we shortened the venetoclax treatment period to 14 days during consolidation in the remaining three patients, none of whom developed grade 4 neutropenia or severe infections.
In AML regimens, venetoclax is commonly administered for 28 days during the initial cycle, with subsequent duration adjustments based on cytopenia [14]. Our findings suggest that individualized shortening of venetoclax treatment during consolidation may reduce the risk of myelosuppression-related infections. Two registry studies from the Center for International Blood and Marrow Transplant Research and European Society for Blood and Marrow Transplantation have shown that allo-HSCT improves outcomes in patients with MPAL [15, 16].
Therefore, we recommend allo-HSCT after attainment of CMR or completion of three VOP cycles. This study has some limitations, including its retrospective design, very small sample size, and short follow-up period. Although this regimen has shown promising efficacy, the risks of severe infection and treatment-related mortality require careful evaluation in larger cohorts.
A prospective trial is ongoing to further evaluate the efficacy and safety of the VOP regimen in patients with Ph + MPAL.
In conclusion, our study provides useful preliminary evidence supporting the potential uses of a chemotherapy-free VOP regimen in older or medically unfit patients with Ph + MPAL and those who decline intensive chemotherapy.
Supplementary Information
Supplementary Material 1