Disulfide Engineered Lipase to Enhance the Catalytic Activity: A Structure-Based Approach on BTL2.

Enhancement, control, and tuning of hydrolytic activity and specificity of lipases are major goals for the industry. Thermoalkaliphilic lipases from the I.5 family, with their native advantages such as high thermostability and tolerance to alkaline pHs, are a target for biotechnological applications. Although several strategies have been applied to increase lipases activity, the enhancement through protein engineering without compromising other capabilities is still elusive. Lipases from the I.5 family suffer a unique and delicate double lid restructuration to transition from a closed and inactive state to their open and enzymatically active conformation. In order to increase the activity of the wild type Geobacillus thermocatenulatus lipase 2 (BTL2) we rationally designed, based on its tridimensional structure, a mutant (ccBTL2) capable of forming a disulfide bond to lock the open state. ccBTL2 was generated replacing A191 and F206 to cysteine residues while both wild type C64 and C295 were mutated to serine. A covalently immobilized ccBTL2 showed a 3.5-fold increment in esterase activity with 0.1% Triton X-100 (2336 IU mg-1) and up to 6.0-fold higher with 0.01% CTAB (778 IU mg-1), both in the presence of oxidizing sulfhydryl agents, when compared to BTL2. The remarkable and industrially desired features of BTL2 such as optimal alkaliphilic pH and high thermal stability were not affected. The designed disulfide bond also conferred reversibility to the enhancement, as the increment on activity observed for ccBTL2 was controlled by redox pretreatments. MD simulations suggested that the most stable conformation for ccBTL2 (with the disulfide bond formed) was, as we predicted, similar to the open and active conformation of this lipase.

Metformin Impedes Oxidation of LDL In Vitro.

Metformin is the most commonly prescribed glucose-lowering drug for the treatment of type 2 diabetes. The aim of this study was to investigate whether metformin is capable of impeding the oxidation of LDL, a crucial step in the development of endothelial dysfunction and atherosclerosis. LDL was oxidized by addition of CuCl2 in the presence of increasing concentrations of metformin. The extent of LDL oxidation was assessed by measuring lipid hydroperoxide and malondialdehyde concentrations, relative electrophoretic mobilities, and oxidation-specific immune epitopes. Cytotoxicity of oxLDL in the vascular endothelial cell line EA.hy926 was assessed using the alamarBlue viability test. Quantum chemical calculations were performed to determine free energies of reactions between metformin and radicals typical for lipid oxidation. Metformin concentration-dependently impeded the formation of lipid hydroperoxides, malondialdehyde, and oxidation-specific immune epitopes when oxidation of LDL was initiated by addition of Cu2+. The cytotoxicity of oxLDL was reduced when it was obtained under increasing concentrations of metformin. The quantum chemical calculations revealed that only the reaction of metformin with hydroxyl radicals is exergonic, whereas the reactions with hydroperoxyl radicals or superoxide radical anions are endergonic. Metformin, beside its glucose-lowering effect, might be a suitable agent to impede the development of atherosclerosis and associated CVD. This is due to its capability to impede LDL oxidation, most likely by scavenging hydroxyl radicals.

Omipalisib inspired macrocycles as dual PI3K/mTOR inhibitors.

Activation of the phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway occurs frequently in a wide range of human cancers and is a main driver of cell growth, proliferation, survival, and chemoresistance of cancer cells. Compounds targeting this pathway are under active development as anticancer therapeutics and some of them have reached advanced clinical trials or been approved by the FDA. Dual PI3K/mTOR inhibitors combine multiple therapeutic efficacies in a single molecule by inhibiting the pathway both upstream and downstream of AKT. Herein, we report our efforts on the exploration of novel small molecule macrocycles (MCXs) as dual PI3K/mTOR inhibitors. Macrocyclization is an attractive approach used in drug discovery, as the semi-rigid character of these structures could provide improved potency, selectivity and favorable pharmacokinetic properties. Importantly, this strategy allows access to new chemical space thus obtaining a better intellectual property position. A series of MCXs based on GSK-2126458, a known clinical PI3K/mTOR inhibitor is described. These molecules showed potent biochemical and cellular dual PI3K/mTOR inhibition, demonstrated strong antitumoral effects in human cancer cell lines, and displayed good drug-like properties. Among them, MCX 83 presented remarkable selectivity against a panel of 468 kinases, high in vitro metabolic stability, and favorable pharmacokinetic parameters without significant CYP450 and h-ERG binding inhibition. This profile qualified this compound as a suitable candidate for future in vivo PK-PD and efficacy studies in mouse cancer models.

Macrocyclization as a Source of Desired Polypharmacology. Discovery of Triple PI3K/mTOR/PIM Inhibitors.

The PI3K/AKT/mTOR and PIM kinase pathways contribute to the development of several hallmarks of cancer. Cotargeting of these pathways has exhibited promising synergistic therapeutic effects in liquid and solid tumor types. To identify molecules with combined activities, we cross-screened our collection of PI3K/(±mTOR) macrocycles (MCXs) and identified the MCX thieno[3,2-d]pyrimidine derivative 2 as a moderate dual PI3K/PIM-1 inhibitor. We report the medicinal chemistry exploration and biological characterization of a series of thieno[3,2-d]pyrimidine MCXs, which led to the discovery of IBL-302 (31), a potent, selective, and orally bioavailable triple PI3K/mTOR/PIM inhibitor. IBL-302, currently in late preclinical development (AUM302), has recently demonstrated efficacy in neuroblastoma and breast cancer xenografts. Additionally, during the course of our experiments, we observed that macrocyclization was essential to obtain the desired multitarget profile. As a matter of example, the open precursors 35-37 were inactive against PIM whereas MCX 28 displayed low nanomolar activity.

Pyrrolo[1,2-a]quinoxalines: Insulin Mimetics that Exhibit Potent and Selective Inhibition against Protein Tyrosine Phosphatase 1B.

PTP1B dephosphorylates insulin receptor and substrates to modulate glucose metabolism. This enzyme is a validated therapeutic target for type 2 diabetes, but no current drug candidates have completed clinical trials. Pyrrolo[1,2-a]quinoxalines substituted at positions C1-C4 and/or C7-C8 were found to be nontoxic to cells and good inhibitors in the low- to sub-micromolar range, with the 4-benzyl derivative being the most potent inhibitor (0.24 µm). Some analogues bearing chlorine atoms at C7 and/or C8 kept potency and showed good selectivity compared to TCPTP (selectivity index >40). The most potent inhibitors behaved as insulin mimetics by increasing glucose uptake. The 4-benzyl derivative inhibited insulin receptor substrate 1 and AKT phosphorylation. Molecular docking and molecular dynamics simulations supported a putative binding mode for these compounds to the allosteric α3/α6/α7 pocket, but inconsistent results in enzyme inhibition kinetics were obtained due to the high tendency of these inhibitors to form stable aggregates. Computational calculations supported the druggability of inhibitors.

Development of inhibitors of receptor protein tyrosine phosphatase ß/ζ (PTPRZ1) as candidates for CNS disorders.

A new series of blood-brain barrier permeable molecules designed to mimic the activity of Pleiotrophin in the CNS has been designed and synthesized. These compounds exert their action by interacting with the intracellular domain PD1 of the Protein Tyrosine-Phosphatase Receptor Z1 (PTPRZ1), and inhibiting its tyrosine phosphatase activity. The most potent compounds 10a and 12b (IC50 = 0,1 µM) significantly increase the phosphorylation of key tyrosine residues of PTPRZ1 substrates involved in neuronal survival and differentiation, and display protective effects against amphetamine-induced toxicity. Docking and molecular dynamics experiments have been used to analyze the binding mode and to explain the observed selectivity against PTP1B. An In vivo experiment has demonstrated that 10a can cross the BBB, thus promoting the possibility of moving forward these candidates for the development of drugs for the treatment of CNS disorders, such as drug addiction and neurodegenerative diseases.

Pharmacological inhibition of Receptor Protein Tyrosine Phosphatase ß/ζ (PTPRZ1) modulates behavioral responses to ethanol.

Pleiotrophin (PTN) and Midkine (MK) are neurotrophic factors that are upregulated in the prefrontal cortex after alcohol administration and have been shown to reduce ethanol drinking and reward. PTN and MK are the endogenous inhibitors of Receptor Protein Tyrosine Phosphatase (RPTP) ß/ζ (a.k.a. PTPRZ1, RPTPß, PTPζ), suggesting a potential role for this phosphatase in the regulation of alcohol effects. To determine if RPTPß/ζ regulates ethanol consumption, we treated mice with recently developed small-molecule inhibitors of RPTPß/ζ (MY10, MY33-3) before testing them for binge-like drinking using the drinking in the dark protocol. Mice treated with RPTPß/ζ inhibitors, particularly with MY10, drank less ethanol than controls. MY10 treatment blocked ethanol conditioned place preference, showed limited effects on ethanol-induced ataxia, and potentiated the sedative effects of ethanol. We also tested whether RPTPß/ζ is involved in ethanol signaling pathways. We found that ethanol treatment of neuroblastoma cells increased phosphorylation of anaplastic lymphoma kinase (ALK) and TrkA, known substrates of RPTPß/ζ. Treatment of neuroblastoma cells with MY10 or MY33-3 also increased levels of phosphorylated ALK and TrkA. However, concomitant treatment of neuroblastoma cells with ethanol and MY10 or MY33-3 prevented the increase in pTrkA and pALK. These results demonstrate for the first time that ethanol engages TrkA signaling and that RPTPß/ζ modulates signaling pathways activated by alcohol and behavioral responses to this drug. The data support the hypothesis that RPTPß/ζ might be a novel target of pharmacotherapy for reducing excessive alcohol consumption.