title: Superior anti-tumor activity of the MDM2 antagonist idasanutlin and the Bcl-2 inhibitor venetoclax in p53 wild-type acute myeloid leukemia models.
abstract: Venetoclax, a small molecule BH3 mimetic which inhibits the anti-apoptotic protein Bcl-2, and idasanutlin, a selective MDM2 antagonist, have both shown activity as single-agent treatments in pre-clinical and clinical studies in acute myeloid leukemia (AML). In this study, we deliver the rationale and molecular basis for the combination of idasanutlin and venetoclax for treatment of p53 wild-type AML.
  
  
  
  The effect of idasanutlin and venetoclax combination on cell viability, apoptosis, and cell cycle progression was investigated in vitro using established AML cell lines. In vivo efficacy was demonstrated in subcutaneous and orthotopic xenograft models generated in female nude or non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Mode-of-action analyses were performed by means of cell cycle kinetic studies, RNA sequencing as well as western blotting experiments.
  
  
  
  Combination treatment with venetoclax and idasanutlin results in synergistic anti-tumor activity compared with the respective single-agent treatments in vitro, in p53 wild-type AML cell lines, and leads to strongly superior efficacy in vivo, in subcutaneous and orthotopic AML models. The inhibitory effects of idasanutlin were cell-cycle dependent, with cells arresting in G1 in consecutive cycles and the induction of apoptosis only evident after cells had gone through at least two cell cycles. Combination treatment with venetoclax removed this dependency, resulting in an acceleration of cell death kinetics. As expected, gene expression studies using RNA sequencing showed significant alterations to pathways associated with p53 signaling and cell cycle arrest (CCND1 pathway) in response to idasanutlin treatment. Only few gene expression changes were observed for venetoclax treatment and combination treatment, indicating that their effects are mediated mainly at the post-transcriptional level. Protein expression studies demonstrated that inhibition of the anti-apoptotic protein Mcl-1 contributed to the activity of venetoclax and idasanutlin, with earlier inhibition of Mcl-1 in response to combination treatment contributing to the superior combined activity. The role of Mcl-1 was confirmed by small hairpin RNA gene knockdown studies.
  
  
  
  Our findings provide functional and molecular insight on the superior anti-tumor activity of combined idasanutlin and venetoclax treatment in AML and support its further exploration in clinical studies.
authors.affiliation: Roche Pharma Research & Early Development, Roche Innovation Center Munich, Roche Diagnostics GmbH, Nonnenwald 2, 82377, Penzberg, Germany. christian.lehmann.cl1@roche.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Lehmann
authors.affiliation: Roche Pharma Research & Early Development, Roche Innovation Center Munich, Roche Diagnostics GmbH, Nonnenwald 2, 82377, Penzberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Friess
authors.affiliation: Roche Pharma Research & Early Development, Roche Innovation Center Basel, F-Hoffmann-La Roche Ltd, Basel, Switzerland.
authors.forename: Fabian
authors.initials: F
authors.lastname: Birzele
authors.affiliation: Roche Pharma Research & Early Development, Roche Innovation Center Basel, F-Hoffmann-La Roche Ltd, Basel, Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kiialainen
authors.affiliation: Roche Pharma Research & Early Development, Roche Innovation Center Munich, Roche Diagnostics GmbH, Nonnenwald 2, 82377, Penzberg, Germany.|Present address: Medigene Immunotherapies GmbH, Planegg, Martinsried, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Dangl
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000627:therapeutic use*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D005260:Female; D020869:Gene Expression Profiling; D064593:Heterografts; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors*; D011759:Pyrrolidines / Q000494:pharmacology / Q000627:therapeutic use*; D017423:Sequence Analysis, RNA; D013449:Sulfonamides / Q000627:therapeutic use*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D062366:para-Aminobenzoates / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: C000595707:BCL2 protein, human; D019086:Bridged Bicyclo Compounds, Heterocyclic; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D011759:Pyrrolidines; C586849:RG7388; D013449:Sulfonamides; D016159:Tumor Suppressor Protein p53; D062366:para-Aminobenzoates; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; C579720:venetoclax
keywords: AML; Apoptosis; BCL-2; Cell cycle kinetics; Idasanutlin; MCL-1; MDM2; Synergism; Venetoclax; p53