Pyruvate Dehydrogenase Inhibition Leads to Decreased Glycolysis, Increased Reliance on Gluconeogenesis and Alternative Sources of Acetyl-CoA in Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is an aggressive disease characterized by poor outcomes and therapy resistance. Devimistat is a novel agent that inhibits pyruvate dehydrogenase complex (PDH). A phase III clinical trial in AML patients combining devimistat and chemotherapy was terminated for futility, suggesting AML cells were able to circumvent the metabolic inhibition of devimistat. The means by which AML cells resist PDH inhibition is unknown. AML cell lines treated with devimistat or deleted for the essential PDH subunit, PDHA, showed a decrease in glycolysis and decreased glucose uptake due to a reduction of the glucose transporter GLUT1 and hexokinase II. Both devimistat-treated and PDHA knockout cells displayed increased sensitivity to 2-deoxyglucose, demonstrating reliance on residual glycolysis. The rate limiting gluconeogenic enzyme phosphoenolpyruvate carboxykinase 2 (PCK2) was significantly upregulated in devimistat-treated cells, and its inhibition increased sensitivity to devimistat. The gluconeogenic amino acids glutamine and asparagine protected AML cells from devimistat. Non-glycolytic sources of acetyl-CoA were also important with fatty acid oxidation, ATP citrate lyase (ACLY) and acyl-CoA synthetase short chain family member 2 (ACSS2) contributing to resistance. Finally, devimistat reduced fatty acid synthase (FASN) activity. Taken together, this suggests that AML cells compensate for PDH and glycolysis inhibition by gluconeogenesis for maintenance of essential glycolytic intermediates and fatty acid oxidation, ACLY and ACSS2 for non-glycolytic production of acetyl-CoA. Strategies to target these escape pathways should be explored in AML.

Phase II trial of cytarabine and mitoxantrone with devimistat in acute myeloid leukemia.

Devimistat is a TCA cycle inhibitor. A previously completed phase I study of devimistat in combination with cytarabine and mitoxantrone in patients with relapsed or refractory AML showed promising response rates. Here we report the results of a single arm phase II study (NCT02484391). The primary outcome of feasibility of maintenance devimistat following induction and consolidation with devimistat in combination with high dose cytarabine and mitoxantrone was not met, as maintenance devimistat was only administered in 2 of 21 responders. The secondary outcomes of response (CR + CRi) and median survival were 44% (21/48) and 5.9 months respectively. There were no unexpected toxicities observed. An unplanned, post-hoc analysis of the phase I and II datasets suggests a trend of a dose response in older but not younger patients. RNA sequencing data from patient samples reveals an age-related decline in mitochondrial gene sets. Devimistat impairs ATP synthesis and we find a correlation between mitochondrial membrane potential and sensitivity to chemotherapy. Devimistat also induces mitochondrial reactive oxygen species and turnover consistent with mitophagy. We find that pharmacological or genetic inhibition of mitochondrial fission or autophagy sensitizes cells to devimistat. These findings suggest that an age related decline in mitochondrial quality and autophagy may be associated with response to devimistat however this needs to be confirmed in larger cohorts with proper trial design.

The Novel Phospholipid Mimetic KPC34 Is Highly Active Against Acute Myeloid Leukemia with Activated Protein Kinase C.

Acute myeloid leukemia (AML) is an aggressive malignancy with poor outcomes. Nucleoside analogs are subject to resistance mechanisms including downregulation of equilibrative nucleoside transporter (ENT1) and deoxycytidine kinase (dCK). KPC34 is a novel phospholipid mimetic that when cleaved by phospholipase C (PLC) liberates gemcitabine monophosphate and a diacylglycerol mimetic that inhibits the classical isoforms of protein kinase C (PKC). KPC34 acts independently of ENT1 and dCK. KPC34 was active against all AML cell lines tested with IC50s in the nanomolar range. Enforced expression of PLC increased response to KPC34 in vivo. In an orthotopic, xenograft model, KPC34 treatment resulted in a significant increase in survival compared to control animals and those treated with high-dose cytarabine. In a PDX model with activated PKC, there was a significant survival benefit with KPC34, and at progression, there was attenuation of PKC activation in the resistant cells. In contrast, KPC34 was ineffective against a syngeneic, orthotopic AML model without activated PKC. However, when cells from that model were forced to express PKC, there were significantly increased sensitivity in vitro and survival benefit in vivo. These data suggest that KPC34 is active against AML and that the presence of activated PKC can be a predictive biomarker.

A Phase I Study of CPI-613 in Combination with High-Dose Cytarabine and Mitoxantrone for Relapsed or Refractory Acute Myeloid Leukemia.

Purpose: CPI-613, a lipoate analogue that inhibits pyruvate dehydrogenase (PDH) and α-ketogluterate dehydrogenase (KGDH), has activity in patients with myeloid malignancies. This study explored the role of mitochondrial metabolism in chemotherapy response and determined the MTD, efficacy, and safety of CPI-613 combined with high-dose cytarabine and mitoxantrone in patients with relapsed or refractory acute myeloid leukemia.Experimental Design: The role of mitochondrial response to chemotherapy was assessed in cell lines and animal models. A phase I study of CPI-613 plus cytarabine and mitoxantrone was conducted in patients with relapsed or refractory AML.Results: Exposure to chemotherapy induced mitochondrial oxygen consumption that depended on PDH. CPI-613 sensitized AML cells to chemotherapy indicating that mitochondrial metabolism is a source of resistance. Loss of p53 did not alter response to CPI-613. The phase I study enrolled 67 patients and 62 were evaluable for response. The overall response rate was 50% (26CR+5CRi/62). Median survival was 6.7 months. In patients over 60 years old, the CR/CRi rate was 47% (15/32) with a median survival of 6.9 months. The response rate for patients with poor-risk cytogenetics also was encouraging with 46% (11/24 patients) achieving a CR or CRi. RNA sequencing analysis of a subset of baseline bone marrow samples revealed a gene expression signature consistent with the presence of B cells in the pretreatment marrow of responders.Conclusions: The addition of CPI-613 to chemotherapy is a promising approach in older patients and those with poor-risk cytogenetics. Clin Cancer Res; 24(9); 2060-73. ©2018 AACR.

The novel phospholipid mimetic KPC34 is highly active against preclinical models of Philadelphia chromosome positive acute lymphoblastic leukemia.

Philadelphia chromosome positive B cell acute lymphoblastic leukemia (Ph+ ALL) is an aggressive cancer of the bone marrow. The addition of tyrosine kinase inhibitors (TKIs) has improved outcomes but many patients still suffer relapse and novel therapeutic agents are needed. KPC34 is an orally available, novel phospholipid conjugate of gemcitabine, rationally designed to overcome multiple mechanisms of resistance, inhibit the classical and novel isoforms of protein kinase C, is able to cross the blood brain barrier and is orally bioavailable. KPC34 had an IC50 in the nanomolar range against multiple ALL cell lines tested but was lowest for Ph+ lines. In mice bearing either naïve or resistant Ph+ ALL, KPC34 treatment resulted in significantly improved survival compared to cytarabine and gemcitabine. Treatment with KPC34 and doxorubicin was more effective than doxorubicin and cytarabine. Mice with recurrence of their ALL after initial treatment with cytarabine and doxorubicin saw dramatic improvements in hind limb paralysis after treatment with KPC34 demonstrating activity against established CNS disease. Consistent with this KPC34 was better than gemcitabine at reducing CNS leukemic burden. These promising pre-clinical results justify the continued development of KPC34 for the treatment of Ph+ALL.