Combination of Venetoclax and Midostaurin Efficiently Suppressed Relapsed t(8;21)Acute Myeloid Leukemia With Mutant KIT After Failure of Venetoclax Plus Azacitidine Treatment

Abstract

Acute myeloid leukemia (AML) with t(8;21) is categorized as favorable-risk AML, but KIT mutations show a significantly poor prognostic impact in such patients. Persistent vulnerability to relapse is a major challenge in the treatment of this subtype of patients. Venetoclax is a BCL-2 selective inhibitor. The venetoclax+HMA strategy is also a notable salvage regimen that achieves good clinical outcomes in the treatment of relapsed or refractory (R/R) AML. However, in our clinical practice, we found that disease progressed rapidly even after venetoclax+azacitidine (AZA) therapy in two relapsed t(8;21) AML patients with KIT mutations. We report for the first time the therapeutic potential of venetoclax+midostaurin as a new combination therapy for relapsed t(8;21) AMLs with KIT mutations showing resistance to venetoclax+AZA therapy. Our ex vivo study also showed that midostaurin alone could inhibit proliferation and induce apoptosis of Kasumi-1 cells (e.g. Midostaurin induced G2 phase cell arrest, down-regulated p-KIT and BCL-2, while Bax protein levels were up-regulated) and observed a synergistic anti effect when the two drugs were combined. Our study shows that the venetoclax+midostaurin regimen may be a promising treatment option for R/R t(8;21) AML with KIT mutations.

Keywords: KIT mutation; azacitidine; midostaurin; relapsed acute myeloid leukemia; t(8;21); targeted therapy; venetoclax.

Figure 1

The treatment process of case 1 (A) and case 2 (B) and the hematological toxicity of VEN+MIDO therapy (C). CR, complete remission; PR, partial remission; NR, non-remission; Neg, negative; Pos, positive; IA, cytarabine 100 mg/m² continuous infusion d1-7, idarubicin 12 mg/m² d1-3; HiDAC, cytarabine 2 g/m² over 3 h every 12 h on d1-3; CLAG, cladribine 5 mg/m² d1-5, cytarabine 2 mg/m² d1-5, granulocyte-colony stimulating factor 5 μg/kg d0-5; VEN+AZA, venetoclax once daily (100 mg d1, 200 mg d2, 400 mg d3-28) and azacitidine 75 mg/m² d1-7; VEN+MIDO, venetoclax once daily (100 mg d1-21) concurrent with voriconazole, midostaurin twice daily (50 mg d1-21); allo-HSCT, allogeneic haematopoietic stem cell transplantation; MLFS, morphologic leukemia-free state; NE, neutrophils count (×10⁹/L); HB, hemoglobin (g/L); PLT, platelet count (×10⁹/L). ^aMRD, minimal residual disease detected by multiparameter flow cytometry. ^bAML1-ETO, the presence of the AML1-ETO fusion gene calculated with standard materials, normalized with respect to the number of ABL1 transcripts and expressed as copy numbers per 1×10⁴ copies of abl.

Figure 2

Venetoclax (VEN) synergizes with midostaurin (PKC412) to inhibit proliferation and induce apoptosis in Kasumi-1 cells. (A) The curve represents the dose-dependent effects of VEN and PKC412 on cell proliferation at 72 h. (B, C) Fa-CI plot and combination index (CI) values were calculated with CompuSyn software. CI < 1 indicates synergy, CI = 1 is additive, and CI > 1 indicates antagonism. The results showed that VEN combined with PKC412 had the most notable synergistic effect. (D) PKC412 induced apoptosis in Kasumi-1 cells and cooperatively induced apoptosis with VEN. Apoptosis was determined by Annexin-V/DAPI staining after Kasumi-1 cells were treated with PKC412 alone and in combination with VEN at the indicated concentrations for 72 h. (E) Kasumi-1 cells was treated with PKC412 and/or VEN at indicated concentration (500nM) for 72 h, and cell cycle analysis was performed by flow cytometry. (F) Kasumi-1 cells were exposed to PKC412 and/or VEN at 1μM for 72 h (BCL-2 and Bax) and 500nM for 8 h (KIT and p-KIT), then subjected to Western blotting. GAPDH was measured as a loading control.