Dual mTORC1/2 Inhibition Synergistically Enhances AML Cell Death in Combination with the BCL2 Antagonist Venetoclax.

PURPOSE: Acute myelogenous leukemia (AML) is an aggressive disease with a poor outcome. We investigated mechanisms by which the anti-AML activity of ABT-199 (venetoclax) could be potentiated by dual mTORC1/TORC2 inhibition. EXPERIMENTAL DESIGN: Venetoclax/INK128 synergism was assessed in various AML cell lines and primary patient AML samples in vitro. AML cells overexpressing MCL-1, constitutively active AKT, BAK, and/or BAX knockout, and acquired venetoclax resistance were investigated to define mechanisms underlying interactions. The antileukemic efficacy of this regimen was also examined in xenograft and patient-derived xenograft (PDX) models. RESULTS: Combination treatment with venetoclax and INK128 (but not the mTORC1 inhibitor rapamycin) dramatically enhanced cell death in AML cell lines. Synergism was associated with p-AKT and p-4EBP1 downregulation and dependent upon MCL-1 downregulation and BAK/BAX upregulation as MCL-1 overexpression and BAX/BAK knockout abrogated cell death. Constitutive AKT activation opposed synergism between venetoclax and PI3K or AKT inhibitors, but not INK128. Combination treatment also synergistically induced cell death in venetoclax-resistant AML cells. Similar events occurred in primary patient-derived leukemia samples but not normal CD34+ cells. Finally, venetoclax and INK128 co-treatment displayed increased antileukemia effects in in vivo xenograft and PDX models. CONCLUSIONS: The venetoclax/INK128 regimen exerts significant antileukemic activity in various preclinical models through mechanisms involving MCL-1 downregulation and BAK/BAX activation, and offers potential advantages over PI3K or AKT inhibitors in cells with constitutive AKT activation. This regimen is active against primary and venetoclax-resistant AML cells, and in in vivo AML models. Further investigation of this strategy appears warranted.

Mechanisms underlying synergism between circularized tumor necrosis factor-related apoptosis inducing ligand and bortezomib in bortezomib-sensitive or -resistant myeloma cells.

Mechanisms underlying interactions between a novel, clinically relevant circularized tumor necrosis factor-related apoptosis inducing ligand (TRAIL) agonist, circularly permuted TRAIL (CPT) have been examined in multiple myeloma (MM) cells sensitive or resistant to bortezomib (BTZ). Various MM cell lines for example, U266, including those resistant to bortezomib-resistant U266 cells were exposed to low nanomolar concentrations of bortezomib ± CPT and apoptosis monitored. Circularly permuted TRAIL and bortezomib synergistically induced apoptosis in both BTZ-naïve and -resistant cells. The regimen up-regulated DR4 receptor internalization in MM cells, known to modulate both NF-κB and extrinsic apoptotic pathways. CPT/BTZ disrupted the non-canonical NF-κB pathway, reflected by tumor necrosis factor (TNF) receptor associated factors 3 (TRAF3) up-regulation, NF-κB inducing kinase down-regulation, diminished p52 and p50 processing, and B-cell lymphoma-extra large (BCL-XL) down-regulation, but failed to inactivate the canonical NF-κB pathway, reflected by unchanged or increased expression of phospho-p65. The regimen also sharply increased extrinsic apoptotic pathway activation. Cells exhibiting TRAF3 knock-down, dominant-negative Fas-associated protein with death domain, knock-down of caspase-8, BCL-2/BCL-XL, or exposure to a caspase-9 inhibitor displayed markedly reduced CPT/BTZ sensitivity. Concordant results were observed in bortezomib-resistant cells. The regimen was also active in the presence of stromal cells and was relatively sparing toward normal CD34+ hematopoietic cells. Finally, ex vivo results revealed synergism in primary MM primary cells, including those BTZ, and the CPT/BTZ regimen significantly decreased tumor growth in a patient-derived MM xenograft model. These results indicate that the CPT/BTZ regimen acts via the non-canonical NF-κB as well as intrinsic/extrinsic apoptotic pathways to induce cell death in MM cells, and may represent an effective strategy in the setting of bortezomib resistance.

Clinical experience of CAR T cells for multiple myeloma.

Important advances in the treatment landscape of multiple myeloma (MM) had been seen over the past two decades leading to improved overall survival but despite the progress multiple myeloma is still considered incurable and the prognosis of the pentarefractory patients have been poor. The development of immunotherapy and in particular adoptive cell therapy with chimeric antigen receptor (CAR) T cells have dramatically improved the outcomes of heavily pretreated relapsed/refractory MM patients. The bulk of CAR T-cell constructs currently in clinical development target the B-cell maturation antigen (BCMA) and to date only idecabtagene vicleucel (ide-cel) is approved by the Food and Drug Administration (FDA) for commercial use in adult patients with relapsed or refractory MM based on the promising clinical responses and positive safety record shown in the pivotal KarMMa study. This review focus on the development of CAR T-cell therapy for multiple myeloma as well as a brief review of the mechanisms of resistance, toxicity and new approaches under development.

Enhancing venetoclax activity in hematological malignancies.

INTRODUCTION: Targeting anti-apoptotic pathways involving the BCL2 family proteins represents a novel treatment strategy in hematologic malignancies. Venetoclax, a selective BCL2 inhibitor, represents the first approved agent of this class, and is currently used in CLL and AML. However, monotherapy is rarely sufficient for sustained responses due to the development of drug resistance and loss of dependence upon the targeted protein. Numerous pre-clinical studies have shown that combining venetoclax with other agents may represent a more effective therapeutic strategy by circumventing resistance mechanisms. In this review, we summarize pre-clinical data providing a foundation for rational combination strategies involving venetoclax. AREAS COVERED: Novel combination strategies in hematologic malignancies involving venetoclax, primarily at the pre-clinical level, will be reviewed. We emphasize novel agents that interrupt complementary or compensatory pro-survival pathways, and particularly mechanistic insights underlying synergism. PubMed, Cochrane, EMBASE, and Google scholar were searched from 2000. EXPERT OPINION: Although venetoclax has proven to be an effective therapeutic in hematologic malignancies, monotherapy may be insufficient for maximal effectiveness due to the development of resistance and/or loss of BCL2 addiction. Further pre-clinical and clinical development of combination therapies may be necessary for optimal outcomes in patients with diverse blood cancers.

Blood Transfusion Management and Transfusion-Related Outcomes in Daratumumab-Treated Patients With Relapsed or Refractory Multiple Myeloma.

INTRODUCTION: Daratumumab, a human CD38 monoclonal antibody approved for multiple myeloma (MM) treatment, binds red blood cells (RBCs), resulting in panagglutination in compatibility tests. Published mitigation methods avoid additional testing, ensuring timely release of blood products. Blood transfusion management and transfusion-related outcomes of daratumumab-treated patients in the SIRIUS study are reported, with emphasis on 2 clinical sites. PATIENTS AND METHODS: Patients had MM treated with ≥ 3 prior lines of therapy, including a proteasome inhibitor and an immunomodulatory drug, or were refractory to a proteasome inhibitor and an immunomodulatory drug. RBC typing and alloantibody screening were performed in gel cards. Antibody identification using RBC panels was performed on patients with positive antibody screens. Hematology panels and serum chemistry were analyzed ≤ 2 days before each daratumumab infusion and the first daratumumab dose within each treatment cycle, respectively. Pre- and posttransfusion hemoglobin values were analyzed retrospectively. RESULTS: At clinical cutoff, patients received 236 transfusions; 47 (37.9%) of 124 patients received 147 packed RBC transfusions, and 17 (13.7%) received 89 platelet transfusions. No hemolysis was reported, and 1 platelet transfusion reaction was observed. At Mount Sinai, no transfusion adverse events were observed, no new unexpected RBC alloantibodies were identified, and transfusions increased hemoglobin values (median, 1.2 g/dL). At Levine Cancer Institute, 6 of 7 patients responded to transfusions, with a median hemoglobin change of 1.7 g/dL. CONCLUSION: In SIRIUS, no RBC transfusion reactions, including hemolysis, were observed. Observations from Mount Sinai and Levine Cancer Institute confirm that transfusions may be administered safely to daratumumab-treated patients.