We report the analysis of CPI-613, the first member of a large set of analogs of lipoic acid (lipoate) we have investigated as potential anticancer agents. CPI-613 strongly disrupts mitochondrial metabolism, with selectivity for tumor cells in culture. This mitochondrial disruption includes activation of the well-characterized, lipoate-responsive regulatory phosphorylation of the E1α pyruvate dehydrogenase (PDH) subunit. This phosphorylation inactivates flux of glycolysis-derived carbon through this enzyme complex and implicates the PDH regulatory kinases (PDKs) as a possible drug target. Supporting this hypothesis, RNAi knockdown of the PDK protein levels substantially attenuates CPI-613 cancer cell killing. In both cell culture and in vivo tumor environments, the observed strong mitochondrial metabolic disruption is expected to significantly compromise cell survival. Consistent with this prediction, CPI-613 disruption of tumor mitochondrial metabolism is followed by efficient commitment to cell death by multiple, apparently redundant pathways, including apoptosis, in all tested cancer cell lines. Further, CPI-613 shows strong antitumor activity in vivo against human non-small cell lung and pancreatic cancers in xenograft models with low side-effect toxicity.

BackgroundPancreatic cancer statistics are dismal, with a five-year survival of less than 10%, and over 50% of patients presenting with metastatic disease. Metabolic reprogramming is an emerging hallmark of pancreatic adenocarcinoma, including aerobic glycolysis, oxidative phosphorylation, glutaminolysis, lipogenesis and lipolysis, autophagic status, and anti-oxidative stress. CPI-613 is a novel anti-cancer agent that selectively targets the altered form of mitochondrial energy metabolism in tumor cells, causing changes in mitochondrial enzyme activities and redox status which lead to apoptosis, necrosis and autophagy of tumor cells.MethodsThis is a phase 1 study to determine the maximum-tolerated dose (MTD) of CPI-613 when used in combination with modified FOLFIRINOX (oxaliplatin at 65 mg/m2 and irinotecan at 140 mg/m2, and fluorouracil 400 mg/m2 bolus and 2400 mg/m2 over 46 h) in combination with CPI-613 in patients with newly diagnosed metastatic pancreatic adenocarcinoma with good bone marrow, liver and kidney function and good performance status (NCT01835041 – closed to recruitment). A two-stage dose-escalation scheme (single patient and traditional 3+3 design) was applied. In the single patient stage, one patient was accrued per dose level. The starting dose of CPI-613 was 500 mg/m2/day; the dose level was then escalated by doubling the previous dose if there was no toxicity greater than Grade 2 within 4 weeks attributed as probably or definitely related to CPI-613. The traditional 3+3 dose-escalation stage was triggered if toxicity attributed as probably or definitely related to CPI-613 was ≥ Grade 2. The dose level for CPI-613 for the first cohort in the traditional dose-escalation stage was the same as used in the last cohort of the single patient dose-escalation stage. Secondary objectives were safety, preliminary efficacy, and tissue collection for future analyses. Response rates, progression-free survival and overall survival data were assessed in the patients treated at the MTD.FindingsTwenty patients were enrolled April 22, 2013 – January 8, 2016. The MTD of CPI-613 was 500 mg/m2. The median number of treatment cycles administered at the MTD was 11 (interquartile range, 4–19). Two patients enrolled at a higher dose (1000 mg/m2) both experienced a DLT (dose limiting toxicity). There were 2 unexpected serious adverse events (SAEs), both for the first patient enrolled: 1) possible leaching due to infusion of CPI-613 via non-PVC tubing, and 2) the patient re- accessed her port at home after accidental de-access. Neither incident resulted in a negative clinical outcome. Expected SAEs were: thrombocytopenia, anemia and lymphopenia (all for Patient #2, with anemia and lymphopenia being a DLT); hyperglycemia (Patient #7); hypokalemia, hypoalbuminemia and sepsis (Patient #11); and neutropenia (Patient #20). There was no grade 5 toxicity. For the 18 patients treated at the MTD, the most common Grade 3–4 toxicities were hypokalemia (6/18, 33%), diarrhea (5/18, 28%) and abdominal pain (4/18, 22%). Sensorial neu...

BackgroundTargeting cancer cell metabolism is recognized as a promising arena for development of cancer chemotherapeutics. Moreover, redox metabolism is also systematically altered in tumor cells. Indeed, there is growing reason to believe that tumor-specific alteration of redox control of metabolism will be central to understanding and attacking malignancy. We report here that lipoate analog CPI-613 attacks a gate-keeping, lipoate-using metabolic enzyme, alpha-ketoglutarate dehydrogenase (KGDH), by a redox mechanism selectively in tumors cells.ResultsCPI-613 inhibited KGDH function strongly and rapidly, selectively in tumor cells. Moreover, CPI-613 induced a correspondingly rapid, powerful redox signal in tumor cell mitochondria. This signal was associated with redox modification of KGDH (including extensive enzyme glutathionylation and redox blockage of enzyme lipoate sulfhydryls), correlating with KGDH inactivation. The source of this tumor-specific mitochondrial redox modulatory signal was not electron transport complexes (I or III), but was largely or entirely the E3 (dihydrolipoamide dehydrogenase) component of dehydrogenases, including KGDH. Finally, we demonstrated that KGDH activity was redox regulated (in tumor cells), as expected if a tumor-specific redox process (auto)regulates KGDH.ConclusionsOur data demonstrate that lipoate analog CPI-613 attacks redox control of KGDH activity in tumor cells, perhaps by modulation of an existing lipoate-sensitive allosteric process normally governing tumor cell KGDH activity. Together with its previously reported, mechanistically distinct (non-redox) effects on the other major, lipoate-using mitochondrial metabolic enzyme, pyruvate dehydrogenase, CPI-613’s KGDH effects indicate that this agent simultaneously attacks multiple central, essential components of tumor cell metabolic regulation.

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Abstract. We report studies using an enhanced experimental system to investigate organization of nuclear pre-mRNA metabolism. It is based on the powerful genetic system and polytene nuclei of Drosophila. We observe (at steady state) movement of a specific premRNA between its gene and the nuclear surface. This movement is isotropic, at rates consistent with diffusion and is restricted to a small nuclear subcompartment defined by exclusion from chromosome axes and the nucleolus. Bulk polyadenylated nuclear pre-mRNA precisely localizes in this same subcompartment indieating that most or all pre-mRNAs use the same route of intranuclear movement.In addition to association with nascent transcripts, snRNPs are coconcentrated with pre-mRNA in this subcompartment. In contrast to constitutive splices, at least one regulated splice occurs slowly and may undergo execution remotely from the site of pre-mRNA synthesis. Details of our results suggest that retention of incompletely spliced pre-mRNA is a function of the nuclear surface.We propose a simple model-based on channeled diffusion-for organization of intranuclear transport and metabolism of pre-mRNAs in polytene nuclei. We argue that this model can be generalized to all metazoan nuclei. METAZOAN nuclei contain specific substructures implicated in pre-mRNA metabolism (see, for example, Fakan and Puvion, 1980; Lerner et al., 1981; McConnell et al., 1987;Lawrence et al., 1989;Spector, 1990;Fu and Maniatis, 1990;Carter et al., 1991; CarmoFonseca et al., 1991; Huang and Spector, 1991; Shermoen and O'Farrell, 1991;Wu et al., 1991;Xing and Lawrence, 1991;Li and Bingham, 1991;Kopczynski and Muskavitch, 1992). The capacity to extend these provocative observations is currently constrained by lack of a suitable genetic system for dissection of structure-function relationships and by inadequate convenience (EM) or resolution (light microscopy) among the various techniques for analysis of three dimensional organization in highly complex, compact nuclei.We report development of a new experimental system that both augments physical analytical techniques and permits application of a powerful genetic system. Our approach exploits resources uniquely available in Drosophila. First ,,o500) of an individual interphase chromatid are tightly synapsed in register to produce a giant, polytene chromosome (for review see Ashburner, 1989). In contrast to most diploid interphase chromosomes, individual polytene chromosome arms are readily identifiable as discrete structures in intact nuclei. Moreover, the simple arrangement of Drosophila chromosome arms is retained in these giant nuclei. Thus, polytene nuclei provide an "exploded" view of a simple nucleus. Under these conditions the relatively limited resolution of rapid, convenient light microscopic techniques is sufficient to allow clear visualization of relationships between extrachromosomal features and sites of pre-mRNA synthesis, Third, molecular genetic tools are available permitting construction of genes abundantly transcribed in polytene...