ALBERT

Description: Tumor cells rewire metabolic pathways to meet the high metabolic demands of proliferation, frequently developing auxotrophy to specific amino acid(s) (AAs) required to satisfy protein biosynthesis. Thus specific metabolic inhibitors or AA-depleting enzymes have been developed and tested as cancer therapeutics. For example, depletion of asparagine by bacterial L-asparaginase (ASNase) has proven efficacious against hematologic malignancies, especially leukemia and lymphoma, by starving tumors lacking asparagine synthetase (ASNS). We and others have reported that the glutaminase (GLS) activity of ASNase is required for anticancer activity against ASNS-positive leukemia cell types in vitro.1 In vivo, we have found that durable response to ASNase in pre-clinical models of leukemia also requires glutaminase activity, even against ASNS-negative leukemia models; a glutaminase-deficient mutant of ASNase yielded subsequent leukemia recurrence. We speculate that the underlying anti-leukemia mechanism mediated by ASNase glutaminase activity involves a deeper depletion of asparagine within the tumor microenvironment, since ASNS in nearby cells (adipocytes, mesenchymal stromal cells, etc.) can use glutamine as a precursor for asparagine synthesis. Nevertheless, since L-glutamine depletion is thought to cause the significant side effects of ASNase, enzyme variants with reduced glutaminase coactivity are being developed and tested. Another viable therapeutic strategy involving glutamine starvation via GLS inhibitor has shown significant pre-clinical activity in acute myeloid leukemia (AML) and multiple myeloma (MM) models; this approach is synergistic with hypomethylating agents and BCL2 inhibitors in AML, and with proteasome inhibitors in MM. Recent findings highlight the switch to glutamine metabolism as a metabolic dependency of tyrosine kinase-driven AML, and targeting GLS in conjunction with tyrosine kinase inhibition has been proposed.2 Targeting arginine metabolism has been shown to be another viable therapeutic strategy. Arginine (ARG) depletion using pegylated arginine deaminase (ADI-PEG 20) or pegylated arginase (PEG-ARGase), the 2 critical enzymes of the ARG metabolism/urea cycle, reduced leukemia tumor burden in AML models characterized by low arginosuccinate synthetase (ASS) and high uptake of ARG. However, recently reported Phase I/II clinical trials of recombinant PEG-arginase and of ADI-PEG 20 showed minimal efficacy in relapsed/refractory AML and in solid tumors despite efficient depletion of arginine and low ASS1 expression in tumors, indicating that depletion of arginine alone is insufficient for clinical activity. As a final example of AA metabolic pathways targeted in the treatment of hematologic malignancies, exogenous L-cysteine is required for the synthesis of glutathione for antioxidant cellular defense. In pre-clinical studies, multiple malignancy subtypes were sensitive to cysteine and cystine degradation by an engineered human cyst(e)inase enzyme, including AML, acute lymphocytic leukemia, poor-risk chronic lymphocytic leukemia (CLL), and MM.3 In all therapeutic strategies targeting AA metabolism, the tumor microenvironment may contribute to resistance. For example, bone marrow stromal cells efficiently import cystine, convert it to cysteine, and transport it to CLL cells, facilitating leukemia chemoresistance. Mesenchymal stromal cells and bone marrow adipocytes secrete asparagine and glutamine, respectively, and protect leukemia cells from ASNase cytotoxicity. Recent insights into the immune tumor microenvironment highlight interplay between tumor, AAs, and immune cell functions. Some AAs, such as arginine and glutamine, are essential nutrients for immune cell proliferation and metabolism; excessive tumor consumption of glutamine, or secretion of arginase by myeloid-derived suppressor cells or AML blasts, may deprive immune cells, impair T cell proliferation, and induce immunosuppressive phenotypes. GLS inhibitors that block glutamine consumption and arginase inhibitors that increase plasma arginine, increase availability of their respective target nutrients for immune cells and are, therefore, being explored in ongoing clinical trials as monotherapies and in combination with anti-PD1 blockade. Chan WK, Lorenzi PL, Anishkin A, et al. The glutaminase activity of L-asparaginase is not required for anticancer activity against ASNS-negative cells. Blood. 2014;123:3596-3606. Gallipoli P, Giotopoulos G, Tzelepis K, et al. Glutaminolysis is a metabolic dependency in FLT3(ITD) acute myeloid leukemia unmasked by FLT3 tyrosine kinase inhibition. Blood. 2018;131:1639-1653. Zhang W, Trachootham D, Liu J, et al. Stromal control of cystine metabolism promotes cancer cell survival in chronic lymphocytic leukaemia. Nat Cell Biol. 2012;14:276-286. Disclosures Konopleva: Stemline Therapeutics: Research Funding. Lorenzi:Erytech Pharma: Consultancy; NIH: Patents & Royalties.

Description: The authors review the latest knowledge of amino acid metabolism in hematologic malignancies and the clinical relevance and potential of amino acid therapeutic targeting.

Description: l-asparaginase (ASNase) is a metabolism-targeted anti-neoplastic agent used to treat acute lymphoblastic leukemia (ALL). ASNase’s anticancer activity results from the enzymatic depletion of asparagine (Asn) and glutamine (Gln), which are converted to aspartic acid (Asp) and glutamic acid (Glu), respectively, in the blood. Unfortunately, accurate assessment of the in vivo pharmacodynamics (PD) of ASNase is challenging because of the following reasons: (i) ASNase is resilient to deactivation; (ii) ASNase catalytic efficiency is very high; and (iii) the PD markers Asn and Gln are depleted ex vivo in blood samples containing ASNase. To address those issues and facilitate longitudinal studies in individual mice for ASNase PD studies, we present here a new LC-MS/MS bioanalytical method that incorporates rapid quenching of ASNase for measurement of Asn, Asp, Gln, and Glu in just 10 µL of whole blood, with limits of detection (s:n ≥ 10:1) estimated to be 2.3, 3.5, 0.8, and 0.5 µM, respectively. We tested the suitability of the method in a 5-day, longitudinal PD study in mice and found the method to be simple to perform with sufficient accuracy and precision for whole blood measurements. Overall, the method increases the density of data that can be acquired from a single animal and will facilitate optimization of novel ASNase treatment regimens and/or the development of new ASNase variants with desired kinetic properties.

Description: L-Asparaginase (L-ASP) is a key component of acute lymphoblastic leukemia therapy. Its mechanism of action, however, is still poorly understood, in part because of its dual asparaginase and glutaminase activities. In the present study, we tested the hypothesis that L-ASP glutaminase activity is required for anticancer activity. We first used molecular dynamics simulations of the clinically used E. coli L-ASP enzyme to guide engineering of mutants that lack glutaminase activity. Dynamic mapping of enzyme-substrate contacts identified the backbone amine of residue Q59 as having frequent contact with glutamine but not asparagine substrate. That difference identified Q59 as a promising mutagenesis target for modifying substrate selectivity. Saturation mutagenesis and screening of the resulting Q59 mutants identified Q59L as retaining asparaginase activity yet exhibiting undetectable glutaminase activity. Using Q59L to test the glutaminase-anticancer hypothesis, we observed no anticancer activity by Q59L against cell lines that do express asparagine synthetase (ASNS), including six leukemia lines—CCRF-CEM, SR, MOLT-4, K562, NALM-6, and REH—and two ovarian cancer lines—OVCAR-8 and SK-OV-3. Wild-type (WT) L-ASP, on the other hand, effected a dose-response in all of those cell lines, suggesting that glutaminase activity is required to kill cancer cells that express ASNS.  Unexpectedly, Q59L exhibited potent anticancer activity against cell lines that do not express detectable ASNS, including the leukemia cell lines Sup-B15 and RS4;11 and ASNS siRNA-treated OVCAR-8 cells. We conclude that the glutaminase activity of L-ASP is not necessary for anticancer activity against cell types that do not express ASNS. Since Q59L is expected to exhibit reduced toxicity relative to wild-type L-ASP because of its reduced glutaminase activity, these findings provide rationale for clinical assessment of Q59L L-ASP for the treatment of ASNS-deficient cancers. Disclosures: Lorenzi: ERYtech Pharma: Consultancy, Membership on an entity’s Board of Directors or advisory committees, US 7985548, US 7985548 Patents & Royalties. Off Label Use: L-asparaginase is an enzyme-drug approved for treatment of acute lymphoblastic leukemia.

Description: Glutamine (Gln) is required for growth and proliferation of several tumor types including AML. Glutaminase (GLS) is a mitochondrial enzyme that catalyzes conversion of Gln to glutamate (Glu), which provides carbons for the TCA cycle and regulates redox homeostasis through production of glutathione and NADH. CB-839 is a highly selective, reversible, allosteric inhibitor of GLS. In this study we studied metabolic and cellular consequences of GLS inhibition in AML cells cultured in normoxic or hypoxic conditions. First, we performed metabolomic analysis of HL-60 cells co-cultured with bone marrow (BM)-derived mesenchymal stem cells (MSCs). Consistent with the known mechanism of GLS inhibition, CB-839 caused a rapid and extensive decrease in intracellular Glu in both HL60 and MSC and a corresponding increase in intracellular Gln in both cell types. Unexpectedly, CB-839-treated cells exhibited a rapid increase in intracellular and extracellular concentrations of multiple amino acids (Phe, kynurenine, Trp, Leu, Ile, Met, Tyr, Val, Thr, Ala, Gln, Asn, and His), possibly reflecting inhibition of global protein synthesis. CB-839 suppressed cysteine consumption from the extracellular compartment and caused rapid increase in intracellular taurine in HL-60 cells, suggesting altered redox homeostasis (Fig. 1A). CB-839 inhibited cellular growth of HL-60 and MV4;11 AML cells cultured alone or co-cultured with MSC, under conditions mimicking the BM microenvironment (Fig. 1B). Stable isotope-resolved metabolomics (SIRM) analysis with 13C5, 15N2-Gln in HL-60 cells indicated that treatment with CB-839 severely hindered Gln anaplerosis to similar extent under normoxic or hypoxic conditions. Moreover, Gln is predominantly used to carry out oxidative metabolism. The enriched fraction of aspartate in treated cells dropped dramatically (to approximately 20% or less of the pool), suggesting that leukemia cells require Krebs cycle-derived oxaloacetate transamination for the generation of aspartate (Fig. 1C). Limiting Gln supply using CB-839 caused reduction in the concentration of alpha-ketoglutarate (α-KG) and the oncometabolite 2-hydroxyglutarate (2-HG), known to play a role in the pathogenesis of AML. We have previously shown that the leukemic BM microenvironment is highly hypoxic (Benito PLoS One 2011), andhypoxia has been reported to induce production of the L-enantiomer of 2-HG (L-2HG) (Intlekofer Cell Metabolism 2015). In AML cells, hypoxia selectively induced the production of L-2HG measured by LC-MS/MS in HL-60 (6.2 fold) and OCI-AML3 cells (2.9 fold) with wt-IDH. This increase in L-2HG was potently inhibited by CB-839, implicating Gln as a source for L-2HG production by AML cells under hypoxia. HL-60 and OCI-AML3 AML cells produced very limited amounts of the D-enantiomer of 2HG (D-2HG), and neither hypoxia nor CB-839 significantly affected D-2HG levels. We recently reported that CB-839 increased hydroxymethylation (hmc) levels using a HELP-GT assay (Velez ASH 2015), and the implications of those observations are the subject of ongoing studies. Prompted by the observation of increased hmc in response to CB-839 treatment, we next examined the efficacy of CB-839 in combination with the DNMT3A inhibitor 5-azacitidine (5-AZA). Treatment with 1µM CB-839 and escalating doses of 5-AZA caused additive or synergistic inhibition of cellular growth after 5 days of culture, both under normoxia and hypoxia, in AML cell lines (OCI-AML3, HL-60, MV4;11) and in primary AML cells (n=3) (Fig. 1D). To test the efficacy of both compounds in vivo, we injected NSG-S mice with genetically engineered MV4;11/Luc cells. Bioluminescent imaging (BLI) demonstrated significantly reduced leukemia burden in treated groups compared to controls, more prominently in the CB-839 plus 5-AZA co-treated mice. CB-839 and 5-AZA co-treatment resulted in significant extension of survival compared with 5-AZA single agent, p

Description: Cytotoxic T lymphocyte (CTL)-based cancer immunotherapies have shown great promise for inducing clinical regressions by targeting tumor-associated antigens (TAA). To expand the TAA landscape of pancreatic ductal adenocarcinoma (PDAC), we performed tandem mass spectrometry analysis of HLA class I-bound peptides from 35 PDAC patient tumors. This identified a shared HLA-A*0101 restricted peptide derived from co-transcriptional activator Vestigial-like 1 (VGLL1) as a putative TAA demonstrating overexpression in multiple tumor types and low or absent expression in essential normal tissues. Here we show that VGLL1-specific CTLs expanded from the blood of a PDAC patient could recognize and kill in an antigen-specific manner a majority of HLA-A*0101 allogeneic tumor cell lines derived not only from PDAC, but also bladder, ovarian, gastric, lung, and basal-like breast cancers. Gene expression profiling reveals VGLL1 as a member of a unique group of cancer-placenta antigens (CPA) that may constitute immunotherapeutic targets for patients with multiple cancer types.

Description: Motivation The concept of synergy between two agents, over a century old, is important to the fields of biology, chemistry, pharmacology and medicine. A key step in drug combination analysis is the selection of an additivity model to identify combination effects including synergy, additivity and antagonism. Existing methods for identifying and interpreting those combination effects have limitations. Results We present here a computational framework, termed response envelope analysis (REA), that makes use of 3D response surfaces formed by generalized Loewe Additivity and Bliss Independence models of interaction to evaluate drug combination effects. Because the two models imply two extreme limits of drug interaction (mutually exclusive and mutually non-exclusive), a response envelope defined by them provides a quantitatively stringent additivity model for identifying combination effects without knowing the inhibition mechanism. As a demonstration, we apply REA to representative published data from large screens of anticancer and antibiotic combinations. We show that REA is more accurate than existing methods and provides more consistent results in the context of cross-experiment evaluation. Availability and implementation The open-source software package associated with REA is available at: https://github.com/4dsoftware/rea. Supplementary information Supplementary data are available at Bioinformatics online.

Description: L-asparaginase (L-ASP) is an enzyme-drug that has been used for decades to treat acute lymphoblastic leukemia (ALL). The red blood cell (RBC)-encapsulated L-ASP product GRASPA (eryaspase) was introduced recently with the goal of reducing L-ASP side effects without compromising efficacy. We previously showed in a Phase 2/3 trial that none of the patients treated with GRASPA had evidence of allergic reactions during induction compared to 46% of patients treated with non-encapsulated L-ASP (Baruchel et al., ASH, 2015). Similarly, evidence of pancreatic or hepatic toxicities were substantially lower with GRASPA compared to native L-ASP. Hence, GRASPA exhibits a clear benefit over L-ASP in terms of toxicity profile. The next critical question is whether GRASPA can maintain asparagine depletion. Since plasma asparagine must be transported into the RBC to be degraded by GRASPA, the RBC membrane could limit the efficacy of GRASPA. Therefore, we sought to characterize the transport and degradation of amino acids between the plasma and RBC cytoplasm in the presence of L-ASP or GRASPA. To that end, we used a bioanalytical method for the simultaneous analysis of the metabolites asparagine, aspartic acid, glutamine, and glutamic acid. Notably, the method completely quenches L-ASP and GRASPA and uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) to achieve high sensitivity, accuracy, and precision. The method also involves correction for ex vivo (post-sampling) depletion of target amino acids, which occurs, for example, during centrifugation of whole blood to separate RBCs and plasma. Specifically, we added two stable isotope-labeled amino acids, 13C4-asparagine and 13C5-glutamine, to the sample at the point of collection. After centrifugation, samples were quenched by addition of 10% formic acid. Concentrations of all 12C- amino acids and their 13C- counterparts were then determined by LC-MS/MS. The difference between the nominal concentrations of the 13C amino acid substrates and their L-ASP-generated products were used to correct for the actual concentrations of the 12C amino acids. In that manner, measuring ex vivo conversion of 13C4-asparagine to 13C4-aspartate and conversion of 13C5-glutamine to 13C5-glutamate provided correction factors to calculate the original concentrations of the endogenous metabolites (unlabeled asparagine and glutamine) present in the sample at the time of collection. In whole blood test tube reactions containing L-ASP or GRASPA at matched overall asparaginase activities, the glutaminase activity of GRASPA was 10-fold lower than that of L-ASP, with initial rates of approximately 0.8 µM/min and 8.0 µM/min, respectively. Therefore, GRASPA exhibits significantly decreased glutaminase activity relative to L-ASP, resulting in an approximately 10-fold increase in selectivity for asparagine over glutamine, which may explain the observed decrease in frequency of adverse events in clinical trials with GRASPA compared to L-ASP. Notably, in the presence of GRASPA, asparagine was rapidly and extensively converted to aspartic acid inside the RBC of GRASPA, whereas no aspartic acid accumulated in the RBC following treatment of whole blood with L-ASP. In conclusion, the RBC membrane of GRASPA imbues L-ASP with improved target selectivity, which may explain the better toxicity profile of GRASPA. Altered target selectivity has been added to a growing list of beneficial properties of the RBC membrane, including improved half-life and decreased immunogenicity. Disclosures Lorenzi: Erytech Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: NIH-held patent related to L-asparaginase. Weinstein:NIH: Patents & Royalties: patent related to L-asparaginase. Swart:Erytech Pharma: Employment, Membership on an entity's Board of Directors or advisory committees. El-Hariry:Erytech Pharma: Employment.