The search for pyruvate kinase-R activators; from a HTS screening hit via an impurity to the discovery of a lead series.

Pyruvate kinase (PK) is an essential component of cellular metabolism, converting ADP and phosphoenolpyruvate (PEP) to pyruvate in the final step of glycolysis. Of the four unique isoforms of pyruvate kinase, R (PKR) is expressed exclusively in red blood cells and is a tetrameric enzyme that depends on fructose-1,6-bisphosphate (FBP) for activation. PKR deficiency leads to hemolysis of red blood cells resulting in anemia. Activation of PKR in both sickle cell disease and beta-thalassemia patients could lead to improved red blood cell fitness and survival. The discovery of a novel series of substituted urea PKR activators, via the serendipitous identification and diligent characterization of a minor impurity in an High Throughput Screening (HTS) hit will be discussed.

Synthesis and Characterization of Andrographolide Derivatives as Regulators of ßAPP Processing in Human Cells.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder, one of the main characteristics of which is the abnormal accumulation of amyloid peptide (Aß) in the brain. Whereas ß-secretase supports Aß formation along the amyloidogenic processing of the ß-amyloid precursor protein (ßAPP), α-secretase counterbalances this pathway by both preventing Aß production and triggering the release of the neuroprotective sAPPα metabolite. Therefore, stimulating α-secretase and/or inhibiting ß-secretase can be considered a promising anti-AD therapeutic track. In this context, we tested andrographolide, a labdane diterpene derived from the plant Andrographis paniculata, as well as 24 synthesized derivatives, for their ability to induce sAPPα production in cultured SH-SY5Y human neuroblastoma cells. Following several rounds of screening, we identified three hits that were subjected to full characterization. Interestingly, andrographolide (8,17-olefinic) and its close derivative 14α-(5',7'-dichloro-8'-quinolyloxy)-3,19-acetonylidene (compound 9) behave as moderate α-secretase activators, while 14α-(2'-methyl-5',7'-dichloro-8'-quinolyloxy)-8,9-olefinic compounds 31 (3,19-acetonylidene) and 37 (3,19-diol), whose two structures are quite similar although distant from that of andrographolide and 9, stand as ß-secretase inhibitors. Importantly, these results were confirmed in human HEK293 cells and these compounds do not trigger toxicity in either cell line. Altogether, these findings may represent an encouraging starting point for the future development of andrographolide-based compounds aimed at both activating α-secretase and inhibiting ß-secretase that could prove useful in our quest for the therapeutic treatment of AD.

Design, synthesis, and biological evaluation of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinones as a new series of AMPKɑ1ß1γ1 activators.

Adenosine monophosphate-activated protein kinase (AMPK) plays a key role in maintaining whole-body homeostasis and has been regarded as a therapeutic target for the treatment of diabetic nephropathy (DN). Herein, a series of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinone derivatives is reported as AMPKɑ1ß1γ1 activators. The in vitro biological assay demonstrated that compounds 12k (EC50 [AMPKα1γ1ß1] = 180 nM) and 13q (EC50 [AMPKα1γ1ß1] = 2 nM) displayed significant enzyme activation. Mechanism studies indicated that both compounds reduced the levels of reactive oxygen species in a rat kidney fibroblast cell line (NRK-49F) stimulated by transforming growth factor-ß and induced early apoptosis of NRK-49F cells at 10 µM. Molecular docking studies suggested that 13q exhibited critical hydrogen-bond interactions with the critical amino acid residues Lys29, Lys31, Asn111, and Asp88 at the binding site of the AMPK protein. These results enrich the structure pool of AMPK activators and provide novel lead compounds for the subsequent development of compounds with a promising therapeutic potential against DN.

Discovery of Potent Small-Molecule SIRT6 Activators: Structure-Activity Relationship and Anti-Pancreatic Ductal Adenocarcinoma Activity.

SIRT6 activation is thought to be a promising target for the treatment of many diseases, particularly cancer. Herein, we report the discovery of a series of new small-molecule SIRT6 activators. Structure-activity relationship analyses led to the identification of the most potent compound, 2-(1-benzofuran-2-yl)-N-(diphenylmethyl) quinoline-4-carboxamide (12q), which showed an EC1.5 value of 0.58 ± 0.12 µM and an EC50 value of 5.35 ± 0.69 µM against SIRT6-dependent peptide deacetylation in FLUOR DE LYS assay. It exhibited weak or no activity against other HDAC family members as well as 415 kinases, indicating good selectivity for SIRT6. 12q significantly inhibited the proliferation and migration of pancreatic ductal adenocarcinoma (PDAC) cells in vitro. It also markedly suppressed the tumor growth in a PDAC tumor xenograft model. This compound showed attractive pharmacokinetic properties. Overall, 12q could be a good lead compound for the treatment of PDAC, and it is worthy of further study.

Activating Effect of 3-Benzylidene Oxindoles on AMPK: From Computer Simulation to High-Content Screening.

AMP-activated protein kinase (AMPK) is currently the subject of intensive study and active discussions. AMPK performs its functions both at the cellular level, providing the switch between energy-consuming and energy-producing processes, and at the whole body level, particularly, regulating certain aspects of higher nervous activity and behavior. Control of such a 'main switch' compensates dysfunctions and associated diseases. In the present paper, we studied the binding of 3-benzylidene oxindoles to the kinase domain of the AMPK α-subunit, which is thought to prevent its interaction with the autoinhibitory domain and thus result in the AMPK activation. For this purpose, we developed the cellular test system based on the AMPKAR plasmid, which implements the FRET effect, synthesized a number of 3-benzylidene oxindole compounds and simulated their binding to various sites of the kinase domain. The most probable binding site for the studied compounds was established by the correlation of calculated and experimental data. The obtained results allow to analyze various classes of AMPK activators using virtual and high-content screening.

Design, synthesis and biological evaluation of mogrol derivatives as a novel class of AMPKα2ß1γ1 activators.

Adenosine monophosphate-activated protein kinase (AMPK) has been considered as a promising drug target for its regulation in both glucose and lipid metabolism. Mogrol was originally identified from high throughput screening as a small molecule activator of AMPK subtype α2ß1γ1. In order to enhance its potency on AMPK and summarize the structure-activity relationships, a series of mogrol derivatives were designed, synthesized and evaluated in pharmacological AMPK activation assays. The results showed that the amine derivatives at the 24-position can improve the potency. Among them, compounds 3 and 4 exhibited the best potency (EC50: 0.15 and 0.14 µM) which was 20 times more potent than mogrol (EC50: 3.0 µM).

Identification and Total Synthesis of Two Previously Unreported Odd-Chain Bis-Methylene-Interrupted Fatty Acids with a Terminal Olefin that Activate Protein Phosphatase, Mg2+/Mn2+-Dependent 1A (PPM1A) in Ovaries of the Limpet Cellana toreuma.

Diverse non-methylene-interrupted (NMI) fatty acids (FAs) with odd-chain lengths have been recognized in triacylglycerols and polar lipids from the ovaries of the limpet Cellana toreuma, however their biological properties remain unclear. In this study, two previously unreported odd-chain NMI FAs, (12Z)-12,16-heptadecadienoic (1) and (14Z)-14,18-nonadecadienoic (2) acids, from the ovary lipids of C. toreuma were identified by a combination of equivalent chain length (ECL) values of their methyl esters and capillary gas chromatography-mass spectrometry (GC-MS) of their 3-pyridylcarbinol derivatives. On the basis of the experimental results, both 1 and 2 were synthesized to prove their structural assignments and to test their biological activity. The ECL values and electron impact-mass (EI-MS) spectra of naturally occurring 1 and 2 were in agreement with those of the synthesized 1 and 2. In an in vitro assay, both 1 and 2 activated protein phosphatase, Mg2+/Mn2+-dependent 1A (PPM1A) up to 100 µM in a dose-dependent manner.

Small-Molecule Activators of Glucose-6-phosphate Dehydrogenase (G6PD) Bridging the Dimer Interface.

We recently identified AG1, a small-molecule activator that functions by promoting oligomerization of glucose-6-phosphate dehydrogenase (G6PD) to the catalytically competent forms. Biochemical experiments indicate that the activation of G6PD by the original hit molecule (AG1) is noncovalent and that one C2 -symmetric region of the G6PD homodimer is important for ligand function. Consequently, the disulfide in AG1 is not required for activation of G6PD, and a number of analogues were prepared without this reactive moiety. Our study supports a mechanism of action whereby AG1 bridges the dimer interface at the structural nicotinamide adenine dinucleotide phosphate (NADP+ ) binding sites of two interacting G6PD monomers. Small molecules that promote G6PD oligomerization have the potential to provide a first-in-class treatment for G6PD deficiency. This general strategy could be applied to other enzyme deficiencies in which control of oligomerization can enhance enzymatic activity and/or stability.

Synthesis of novel 7-azaindole derivatives containing pyridin-3-ylmethyl dithiocarbamate moiety as potent PKM2 activators and PKM2 nucleus translocation inhibitors.

Multiple lines of evidence have indicated that pyruvate kinase M2 (PKM2) is upregulated in most cancer cells and it is increasingly recognized as a potential therapeutic target in oncology. In a continuation of our discovery of lead compound 5 and SAR study, the 7-azaindole moiety in compound 5 was systematically optimized. The results showed that compound 6f, which has a difluoroethyl substitution on the 7-azaindole ring, exhibited high PKM2 activation potency and anti-proliferation activities on A375 cell lines. In a xenograft mouse model, oral administration of compound 6f led to significant tumor regression without obvious toxicity. Further mechanistic studies revealed that 6f could influence the translocation of PKM2 into nucleus, as well as induction of apoptosis and autophagy of A375 cells. More importantly, compound 6f significantly inhibited migration of A375 cells in a concentration-dependent manner. Collectively, 6f may serve as a lead compound in the development of potent PKM2 activators for cancer therapy.

Suppressive activities of KC1-3 on HMGB1-mediated septic responses.

In the present study, several decursin analogues (KC1-3) were synthesized and evaluated in terms of their anti-septic activities on high mobility group box 1 (HMGB1)-mediated septic responses and survival rate in a mouse model of sepsis. KC1 and KC3, but not KC2, significantly reduced HMGB1 release in lipopolysaccharide (LPS)-activated human umbilical vein endothelial cells (HUVECs) and attenuated the cecal ligation and puncture (CLP)-induced release of HMGB1. Additionally, in vitro analyses revealed that KC1 and KC3 both alleviated HMGB1-mediated vascular disruptions and inhibited hyperpermeability in mice, and in vivo analyses revealed that KC1 and KC3 reduced sepsis-related mortality and tissue injury. Taken together, the present results suggest that KC1 and KC3 both reduced HMGB1 release and septic mortality and, thus, may be useful for the treatment of sepsis.

α-Carbonic anhydrases are strongly activated by spinaceamine derivatives.

A series of 4-substituted-spinaceamine (4,5,6,7-tetrahydro-imidazolo[4,5-c]pyridine) were prepared from histamine and aromatic aldehydes Schiff bases, and investigated as activators of four human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic hCA I, II and VII, and the membrane-associated hCA IV. All isoforms were effectively activated by the new derivatives, and the nature of the moiety in position 4 of the bicyclic system was the factor influencing activation properties against all isoforms. For hCA I, these compounds showed KAs in the range of 2.52-21.5 µM, the most effective activator being 4-(2-hydroxyphenyl)-spinaceamine. For hCA II the activation constants ranged between 0.60 and 17.2 µM, with 4-(2,3,5,6-tetrafluorophenyl)- spinaceamine the best activator. Affinity for hCA IV was in the range of 0.52-63.8 µM, and the same compound as for hCA II was the most effective activator. The most sensitive isoform for activation was the brain-associated hCA VII, for which KAs in the range of 82 nM-4.26 µM were observed. Effective hCA VII activators were the (2-bromophenyl)-, 2,3,5,6-tetrafluorophenyl- and furyl-substituted spineaceamines (KAs of 82-95 nM). As CA activators may have pharmacologic applications in various fields, this work provides interesting derivatives for further studies.

Side-chain cleaved phytoecdysteroid metabolites as activators of protein kinase B.

Phytoecdysteroids exert their non-hormonal anabolic and adaptogenic effects in mammals, including humans, through a partially revealed mechanism of action involving the activation of protein kinase B (Akt). We have recently found that poststerone, a side-chain cleaved in vivo metabolite of 20-hydroxyecdysone, exerts potent anabolic activity in rats. Here we report the semi-synthetic preparation of a series of side-chain cleaved ecdysteroids and their activity on the Akt phosphorylation in murine skeletal muscle cells. Twelve C-21 ecdysteroids including 8 new compounds were obtained through the oxidative side-chain cleavage of various phytoecdysteroids, or through the base-catalyzed autoxidation of poststerone. The complete 1H and 13C NMR spectroscopic assignments of the new compounds are presented. Among the tested compounds, 9 could activate Akt stronger than poststerone revealing that side-chain cleaved derivatives of phytoecdysteroids other than 20-hydroxyecdysone are valuable bioactive metabolites. Thus, our results suggest that the expectable in vivo formation of such compounds should contribute to the bioactivity of herbal preparations containing ecdysteroid mixtures.

Synthesis and evaluation of esterified Hsp70 agonists in cellular models of protein aggregation and folding.

Over-expression of the Hsp70 molecular chaperone prevents protein aggregation and ameliorates neurodegenerative disease phenotypes in model systems. We identified an Hsp70 activator, MAL1-271, that reduces α-synuclein aggregation in a Parkinson's Disease model. We now report that MAL1-271 directly increases the ATPase activity of a eukaryotic Hsp70. Next, twelve MAL1-271 derivatives were synthesized and examined in a refined α-synuclein aggregation model as well as in an assay that monitors maturation of a disease-causing Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) mutant, which is also linked to Hsp70 function. Compared to the control, MAL1-271 significantly increased the number of cells lacking α-synuclein inclusions and increased the steady-state levels of the CFTR mutant. We also found that a nitrile-containing MAL1-271 analog exhibited similar effects in both assays. None of the derivatives exhibited cellular toxicity at concentrations up to 100 µm, nor were cellular stress response pathways induced. These data serve as a gateway for the continued development of a new class of Hsp70 agonists with efficacy in these and potentially other disease models.

Design, synthesis and evaluation of new classes of nonquaternary reactivators for acetylcholinesterase inhibited by organophosphates.

A new series of nonquaternary conjugates for reactivation of both nerve agents and pesticides inhibited hAChE were described in this paper. It was found that substituted salicylaldehydes conjugated to aminobenzamide through piperidine would produce efficient reactivators for sarin, VX and tabun inhibited hAChE, such as L6M1R3, L6M1R5 to L6M1R7, L4M1R3 and L4M1R5 to L4M1R7. The in vitro reactivation experiment for pesticides inhibited hAChE of these new synthesized oximes were conducted for the first time. Despite they were less efficient than obidoxime, some of them were highlighted as equal or more efficient reactivators in comparison to 2-PAM. It was found that introduction of peripheral site ligands could increase oximes' binding affinity for inhibited hAChE in most cases, which resulted in greater reactivation ability.

The synthesis of N-benzoylindoles as inhibitors of rat erythrocyte glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase.

Glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) play an important function in various biochemical processes as they generate reducing power of the cell. Thus, metabolic reprogramming of reduced nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis is reported to be a vital step in cancer progression as well as in combinational therapeutic approaches. In this study, N-benzoylindoles 9a--9d, which form the main framework of many natural indole derivatives such as indomethacin and N-benzoylindoylbarbituric acid, were synthesized through three easy and effective steps as an in vitro inhibitor effect of G6PD and 6PGD. The N-benzoylindoles inhibited the enzymatic activity with IC50 in the range of 3.391505 µM for G6PD and 2.19-990 µM for 6PGD.

N'-[(E)-Arylidene]-2-(2,3-dihydro-3-oxo-4H-1,4-benzoxazin-4-yl)-acetohydrazides: Synthesis and Evaluation of Caspase Activation Activity and Cytotoxicity.

In our search for novel small cytotoxic molecules potentially activating procaspase-3, we have designed and synthesized a series of novel N'-[(E)-arylidene]-2-(2,3-dihydro-3-oxo-4H-1,4-benzoxazin-4-yl)acetohydrazides (5, 6). Biological evaluation revealed that seven compounds, including 5h, 5j, 5k, 5l, 5n, 6a, and 6b, exhibited moderate to strong cytotoxicity against three human cancer cell lines (SW620, colon cancer; PC-3, prostate cancer; NCI-H23, lung cancer). Among these compounds, two most cytotoxic compounds (5h and 5j) displayed from 3- up to 10-fold higher potency than PAC-1 and 5-FU in three cancer cell lines tested. Three compounds 5j, 5k, and 5n were also found to display better caspases activation activity in comparison to PAC-1. Especially, compound 5k activated the level of caspases activity by 200% higher than that of PAC-1. From this study, three compounds 5j, 5k, and 5n could be considered as potential leads for further design and development of caspase activators and anticancer agents.

Design, Synthesis, Biological Activity, and Structural Analysis of Lactam-Constrained PTPRJ Agonist Peptides.

PTPRJ is a receptor-like protein tyrosine phosphatase mainly known for its antiproliferative and tumor-suppressive functions. PTPRJ dephosphorylates several growth factors and their receptors, negatively regulating cell proliferation and migration. We recently identified a disulfide-bridged nonapeptide, named PTPRJ-19 (H-[Cys-His-His-Asn-Leu-Thr-His-Ala-Cys]-OH), which activates PTPRJ, thereby causing cell growth inhibition and apoptosis of both cancer and endothelial cells. With the aim of replacing the disulfide bridge by a chemically more stable moiety, we have synthesized and tested a series of lactam analogues of PTPRJ-19. This replacement led to analogues with higher activity and greater stability than the parent peptide.

The Discovery of ( S)-1-(6-(3-((4-(1-(Cyclopropanecarbonyl)piperidin-4-yl)-2-methylphenyl)amino)-2,3-dihydro-1 H-inden-4-yl)pyridin-2-yl)-5-methyl-1 H-pyrazole-4-carboxylic Acid, a Soluble Guanylate Cyclase Activator Specifically Designed for Topical Ocular Delivery as a Therapy for Glaucoma.

Soluble guanylate cyclase (sGC), the endogenous receptor for nitric oxide (NO), has been implicated in several diseases associated with oxidative stress. In a pathological oxidative environment, the heme group of sGC can be oxidized becoming unresponsive to NO leading to a loss in the ability to catalyze the production of cGMP. Recently a dysfunctional sGC/NO/cGMP pathway has been implicated in contributing to elevated intraocular pressure associated with glaucoma. Herein we describe the discovery of molecules specifically designed for topical ocular administration, which can activate oxidized sGC restoring the ability to catalyze the production of cGMP. These efforts culminated in the identification of compound (+)-23, which robustly lowers intraocular pressure in a cynomolgus model of elevated intraocular pressure over 24 h after a single topical ocular drop and has been selected for clinical evaluation.

Optimization of Metabolic and Renal Clearance in a Series of Indole Acid Direct Activators of 5'-Adenosine Monophosphate-Activated Protein Kinase (AMPK).

Optimization of the pharmacokinetic (PK) properties of a series of activators of adenosine monophosphate-activated protein kinase (AMPK) is described. Derivatives of the previously described 5-aryl-indole-3-carboxylic acid clinical candidate (1) were examined with the goal of reducing glucuronidation rate and minimizing renal excretion. Compounds 10 (PF-06679142) and 14 (PF-06685249) exhibited robust activation of AMPK in rat kidneys as well as desirable oral absorption, low plasma clearance, and negligible renal clearance in preclinical species. A correlation of in vivo renal clearance in rats with in vitro uptake by human and rat renal organic anion transporters (human OAT/rat Oat) was identified. Variation of polar functional groups was critical to mitigate active renal clearance mediated by the Oat3 transporter. Modification of either the 6-chloroindole core to a 4,6-difluoroindole or the 5-phenyl substituent to a substituted 5-(3-pyridyl) group provided improved metabolic stability while minimizing propensity for active transport by OAT3.

Novel SIRT1 activator MHY2233 improves glucose tolerance and reduces hepatic lipid accumulation in db/db mice.

The NAD+-dependent deacetylase SIRT1, which is associated with the improvement of metabolic syndromes, such as type 2 diabetes, is a well-known longevity-related gene. Several in vitro and in vivo studies have shown the known protective effects of SIRT1 activators, such as resveratrol and SRT1720, on diabetes- or obesity-induced fatty liver and insulin resistance. Here, we newly synthesized 18 benzoxazole hydrochloride derivatives based on the structure of resveratrol and SRT1720. We performed an in vitro SIRT1 activity assay to identify the strongest SIRT1 activator. The assay confirmed MHY2233 to be the strongest SIRT1 activator (1.5-fold more potent than resveratrol), and docking simulation showed that the binding affinity of MHY2233 was higher than that of resveratrol and SRT1720. To investigate its beneficial effects, db/db mice were orally administered MHY2233 for 1 month, and various metabolic parameters were assessed in the serum and liver tissues. MHY2233 markedly ameliorated insulin signaling without affecting body weight in db/db mice. In particular, the mRNA expression of lipogenic genes, such as acetyl CoA carboxylase, fatty acid synthase, and sterol regulatory element-binding protein, which increased in db/db mice, decreased following oral treatment with MHY2233. In conclusion, the novel SIRT1 activator MHY2233 reduced lipid accumulation and improved insulin resistance. This finding may contribute toward therapeutic approaches for fatty liver disease and glucose tolerance.