Identification of a cell-active non-peptide sirtuin inhibitor containing N-thioacetyl lysine

To identify cell-active sirtuin inhibitors containing N-thioacetyl lysine, we synthesized compound 1, which was designed based on the structure of the reported N-ethoxycarbonylacetyl lysine-based sirtuin inhibitor NCS-12k. Compound 1 selectively inhibited SIRT1 in enzyme assays. Compound 1 also caused a dose-dependent increase in p53 acetylation in human colon cancer HCT116 cells, indicating the inhibition of SIRT1 in these cells.     

Evaluation of benzoic acid derivatives as sirtuin inhibitors

Employing a genetically modified yeast strain as a screening tool, 4-dimethylaminobenzoic acid (5) was isolated from the marine sediment-derived Streptomyces sp. CP27-53 as a weak yeast sirtuin (Sir2p) inhibitor. Using this compound as a scaffold, a series of disubstituted benzene derivatives were evaluated to elucidate the structure activity relationships for Sir2p inhibition. The results suggested that 4-alkyl or 4-alkylaminobenzoic acid is the key structure motif for Sir2p inhibitory activity. The most potent Sir2p inhibitor, 4-tert-butylbenzoic acid (20), among the tested compounds in this study turned out to be a weak but selective SIRT1 inhibitor. The calculated binding free energies between the selected compounds and the catalytic domain of SIRT1 were well correlated to their measured SIRT1 inhibitory activities.     

The mimics of Nε-acyl-lysine derived from cysteine as sirtuin inhibitors

Sirtuin inhibitors as physiological research tools and therapeutic potentials have caught many attentions in last decades. The mimics of acyl lysine have been approved to be a very efficient strategy for development of mechanism-based sirtuin inhibitors. In current study, a novel scaffold of l-S-(3-carboxamidopropyl) cysteine (l-CAPC) has been exploited for design and synthesis of sirtuin inhibitors. As a result, the mimics of N^ε-acyl-lysine derived from cysteine including small molecules (5a–m) and peptides (9a–m) have been synthesized. Among these, the peptides 9g and 9h were found to be the most inhibitory potency and selectivity against SIRT2.     

Bivalent SIRT1 inhibitors

In the current study, bivalent compounds 1–17 constructed by covalently linking the ?-amino group of lysine in a tripeptidic scaffold to a functionality via a linker were prepared and examined for their inhibitory potencies against SIRT1, a prototypical member of the β-nicotinamide adenine dinucleotide (β-NAD⁺)-dependent sirtuin family of protein N^ε-acyl-lysine deacylases. A few of them were found to be stronger SIRT1 inhibitors than the N^?-acetyl-lysine-containing monovalent counterparts 18 and 19. As exemplified with compounds 6 and 18, a bivalent SIRT1 inhibitor could exhibit a greater degree of inhibitory selectivity among SIRT1/2/3 than the corresponding monovalent counterpart. This study has laid a foundation for the future development of superior bivalent inhibitors against the (patho)physiologically and therapeutically important sirtuin family of deacylase enzymes.     

Structure activity study of S-trityl-cysteamine dimethylaminopyridine derivatives as SIRT2 inhibitors: Improvement of SIRT2 binding and inhibition

Sirtuin proteins are a highly conserved class of nicotinamide adenine dinucleotide (NAD⁺)-dependent lysine deacylases. The pleiotropic human isoform 2 of Sirtuins (SIRT2) has been engaged in the pathogenesis of cancer in a plethora of reports around the globe. Thus, SIRT2 modulation is deemed as a promising approach for pharmaceutical intervention. Previously, we reported S-Trityl-l-Cysteine (STLC)-ornamented dimethylaminopyridine chemical entity named STC4 with a significant SIRT2 inhibitory capacity; this was separate from the conventional application of STLC scaffold as a kinesin-5 inhibitor. An interactive molecular docking study of SIRT2 and STC4 showed interaction between Asn168 of SIRT2 and the methyl ester of STC4, that appears to hinder STC4 to reach the selective pocket of the protein unlike strong SIRT2 inhibitor SirReal2. To improve its activity, herein, we utilized S-trityl cysteamine pharmacophore lacking the methyl ester. Nine compounds were synthesized and assayed affording three biopertinent SIRT2 inhibitors, and two of them, STCY1 and STCY6 showed higher inhibitory activity than STC4. These compounds have pronounced anti-proliferative activities against different cancer cell lines. A molecular docking study was executed to shed light on the supposed binding mode of the lead compound, STCY1, into the selective pocket of SIRT2 by interaction of the nitrogen of pyridine ring of the compound and Ala135 of the protein. The outcome of the study exposes that the active compounds are effective intermediates to construct more potent biological agents.     

Design,synthesis, in-vitro evaluation and molecular docking studies of novel indole derivatives as inhibitors of SIRT1 and SIRT2

Sirtuins (SIRTs), class III HDAC (Histone deacetylase) family proteins, are associated with cancer, diabetes, and other age-related disorders. SIRT1 and SIRT2 are established therapeutic drug targets by regulating its function either by activators or inhibitors. Compounds containing indole moiety are potential lead molecules inhibiting SIRT1 and SIRT2 activity. In the current study, we have successfully synthesized 22 indole derivatives in association with an additional triazole moiety that provide better anchoring of the ligands in the binding cavity of SIRT1 and SIRT2. In-vitro binding and deacetylation assays were carried out to characterize their inhibitory effects against SIRT1 and SIRT2. We found four derivatives, 6l, 6m, 6n, and 6o to be specific for SIRT1 inhibition; three derivatives, 6a, 6d and 6k, specific for SIRT2 inhibition; and two derivatives, 6s and 6t, which inhibit both SIRT1 and SIRT2. In-silico validation for the selected compounds was carried out to study the nature of binding of the ligands with the neighboring residues in the binding site of SIRT1. These derivatives open up newer avenues to explore specific inhibitors of SIRT1 and SIRT2 with therapeutic implications for human diseases.     

A bicyclic pentapeptide-based highly potent and selective pan-SIRT1/2/3 inhibitor harboring Nε-thioacetyl-lysine

Past few years have seen an active pursuit of the inhibitors for the deacylation catalyzed by the seven human sirtuins (i.e. SIRT1-7) as valuable chemical biological/pharmacological probes of this enzymatic deacylation and lead compounds for developing novel therapeutics for human diseases. In the current study, we prepared eight monocyclic and one bicyclic analogs of a linear pentapeptide-based potent (sub-μM IC₅₀’s) pan-SIRT1/2/3 inhibitor Zheng laboratory discovered recently that harbors the catalytic mechanism-based SIRT1/2/3 inhibitory warhead N^ε-thioacetyl-lysine at its central position. We found that the bicyclic analog exhibited largely comparable SIRT1/2/3 inhibitory potencies to those of the parent linear pentapeptide, however, the former is proteolytically much more stable than the latter. Moreover, the bicyclic analog displayed very weak inhibition against SIRT5/6/7, was cell permeable, and exhibited an anti-proliferative effect on the human SK-MEL-2 melanoma cells. This bicyclic analog could be a lead for the future development of more potent and still selective pan-SIRT1/2/3 inhibitors whose use in studies on human sirtuin biology, pharmacology, and medicinal chemistry could complement with the use of the potent inhibitors selective for a single human sirtuin.     

Discovery of a novel olefin derivative as a highly potent and selective acetyl-CoA carboxylase 2 inhibitor with in vivo efficacy

Novel acetyl-CoA carboxylase 2 (ACC2) selective inhibitors were identified by the conversion of the alkyne unit of A-908292 to the olefin linker. Modification of the center and left part of the lead compound 1b improved the ACC2 inhibitory activity and CYP450 inhibition profile, and afforded a highly selective ACC2 inhibitor 2e which showed in vivo efficacy in C57BL/6 mice.     

Synthesis of some novel hydrazone and 2-pyrazoline derivatives: Monoamine oxidase inhibitory activities and docking studies

A novel series of 2-pyrazoline and hydrazone derivatives were synthesized and investigated for their human monoamine oxidase (hMAO) inhibitory activity. All compounds inhibited the hMAO isoforms (MAO-A or MAO-B) competitively and reversibly. With the exception of 5i, which was a selective MAO-B inhibitor, all derivatives inhibited hMAO-A potently and selectively. According to the experimental K_i values, compounds 6e and 6h exhibited the highest inhibitory activity towards the hMAO-A, whereas compound 5j, which carries a bromine atom at R⁴ of the A ring of the pyrazoline, appeared to be the most selective MAO-A inhibitor. Tested compounds were docked computationally into the active site of the hMAO-A and hMAO-B isozymes. The computationally obtained results were in good agreement with the corresponding experimental values.     

Discovery of novel CDK inhibitors via scaffold hopping from CAN508

Cyclin-dependent kinases (CDKs) are promising drug targets for various human diseases, especially for cancers. Scaffold hopping strategy was applied on CAN508, a known selective CDK9 inhibitor, and a series of pyrazolo[3,4-b]pyridine compounds were synthesized and evaluated in vitro as CDK2 and CDK9 inhibitors. Most compounds exhibited moderate to potent inhibitory activities against both CDK2/cyclin A and CDK9/cyclin T1 systems. Among them, compound 2e showed IC₅₀ values of 0.36?μM for CDK2 and 1.8?μM for CDK9, respectively. Notably, the scaffold alteration seems to cause a shift in the selectivity profile of the inhibitors. In contrast to CAN508, compound 2k demonstrated remarkable selectivity toward CDK2 (265-fold over CDK9). Docking studies on compound 2k provided hints for further design of more potent and selective CDK2/CDK9 inhibitors.     

Discovery of novel thienoquinoline-2-carboxamide chalcone derivatives as antiproliferative EGFR tyrosine kinase inhibitors

Novel thienoquinoline carboxamide-chalcone derivatives were prepared via the cyclization of acylated chalcones and 2-mercaptoquinoline-3-carbaldehyde in DMF with K₂CO₃. Thienoquinolines 9a–f, h exhibited promising antiproliferative effect against all the tested cell lines and gave a significant activity as EGFR inhibitors, with IC₅₀ values ranging from 0.5 and 3.2?µM, and compounds 9e and 9f being the most active of the series. They also showed better activity than Erlotinib against melanoma cancer cell line A375. Moreover, compound 9f influenced pre G1 apoptosis and cell cycle arrest at G2/M phase. The binding mode of the best EGFR inhibitor 9e in the EGFR active site revealed that the thienoquinoline ring occupied the ATP-binding site while the chalcone moiety is located in the allosteric site and is responsible for the enhanced activity of these compounds.     

Synthesis,biological evaluation,and molecular docking study of sulfonate derivatives as nucleotide pyrophosphatase/phosphodiesterase (NPP) inhibitors

A new series of sulfonate derivatives 1a–zk were synthesized and evaluated as inhibitors of nucleotide pyrophosphatases. Most of the compounds exhibited good to moderate inhibition towards NPP1, NPP2, and NPP3 isozymes. Compound 1m was a potent and selective inhibitor of NPP1 with an IC₅₀ value of 0.387 ± 0.007 µM. However, the most potent inhibitor of NPP3 was found as 1x with an IC₅₀ value of 0.214 ± 0.012 µM. In addition, compound 1e was the most active inhibitor of NPP2 with an IC₅₀ value of 0.659 ± 0.007 µM. Docking studies of the most potent compounds were carried out, and the computational results supported the in vitro results.     

Discovery of core-structurally novel PTP1B inhibitors with specific selectivity containing oxindole-fused spirotetrahydrofurochroman by one-pot reaction

Protein tyrosine phosphatase 1B (PTP1B) has been proposed to be an ideal target for treatment of type II diabetes and obesity. However, no druggable PTP1B inhibitor has been established and there is still an urgent demand for the development of structurally novel PTPIB inhibitor. Herein, we reported core-structurally novel PTP1B inhibitors with low micromole-ranged inhibitory activity by one-pot reaction from simple starting materials. Further studies demonstrated some of these active compounds had a specific selectivity over other PTPs. The structure and activity relationship was also described. The best active and selective compound 5e inhibited PTP1B activity with an IC₅₀ of 4.53 μM. Molecular docking analysis further demonstrated that compound 5e bound to the active pocket of PTP1B. The results might provide some insights for further development of new drugs for type II diabetes and obesity.     

Design,synthesis and anti-inflammatory evaluation of novel pyrrolo[2,3-d]pyrimidin derivatives as potent JAK inhibitors

Aiming to develop potent JAK inhibitors, two series of 4-(1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidine derivatives (8a–8p and 11a–11i) were designed and synthesized by coalescing various N-acylpiperidine motifs with baricitinib. The pharmacological results based on enzymatic and cellular assays identified the optimized compound 11e, which exerted over 90% inhibition rates against JAK1 and JAK2, and displayed the most compelling anti-inflammatory efficacy superior to baricitinib by inhibiting NO generation from LPS-induced RAW264.7 macrophages. Importantly, low cytotoxity of 11e was revealed by the IC₅₀ value of 88.2 μM against normal RAW264.7 cells. The binding mode of 11e with JAK1 and JAK2 identified the essential structural bases in accord with SARs analysis. Furthermore, cellular morphology observation and western blot analysis disclosed the ability of 11e to relieve cells inflammatory damage by significantly down-regulating LPS-induced high expression of JAK1, JAK2, as well as pro cytokine IL-1β. Together, 11e was verified as a promising lead for JAK inhibitors for the treatment of inflammatory diseases.     

Syntesis of thio- and seleno-acetamides bearing benzenesulfonamide as potent inhibitors of human carbonic anhydrase II and XII

A novel series of thio- and seleno-acetamides bearing benzenesulfonamide were synthetized and tested as human carbonic anhydrase inhibitors. These compounds were tested for the inhibition of four human (h) isoforms, hCA I, II, IX, and XII, involved in pathologies such as glaucoma (CA II and XII) or cancer (CA IX/XII). Several derivatives showed potent inhibition activity in low nanomolar range such as 3a, 4a, 7a and 8a. Furthermore, based on the tail approach we explain the interesting and selective inhibition profile of compound such as 5a and 9a, which were more selective for hCA I, 9b which was selective for hCA II, 3f selective for hCA IX and finally, 3e and 4b selective for hCA XII, over the other three isoforms. They are interesting leads for the development of more effective and isoform-selective inhibitors.     

Design,synthesis and biological activity evaluation of novel 4-((1-cyclopropyl-3-(tetrahydro-2H-pyran-4-yl)-1H-pyrazol-4-yl) oxy) pyridine-2-yl) amino derivatives as potent transforming growth factor-β (TGF-β) type I receptor inhibitors

TGF-β type I receptor (also known as activin-like kinase 5 or ALK5) plays a critical role in the progression of fibrotic diseases and tumor invasiveness and metastasis, as well. The development of small inhibitors targeting ALK5 has been validated as a potential therapeutic strategy for fibrotic diseases and cancer. Here, we developed various 4-((1-cyclopropyl-3-(tetrahydro-2H-pyran-4-yl)-1H-pyrazol-4-yl) oxy) pyridine-2-yl) amino derivatives as ALK5 inhibitors. The optimization led to identification of potent and selective ALK5 inhibitors 12r. The compound 12r exhibited strong inhibitory activity both in vitro and in vivo, and pharmacokinetics study showed an oral bioavailability of 57.6%. Thus, compound 12r may provide as new therapeutic option as ALK5 TGF-βR1 inhibitor.     

Synthesis and biological evaluation of 7-methoxy-1-(3,4,5-trimethoxyphenyl)-4,5-dihydro-2H-benzo[e]indazoles as new colchicine site inhibitors

The colchicine site inhibitors (CSIs) displayed both antimitotic and vascular disrupting activities, therefore are promising potential antitumor agents. In this study, a series 1-phenyl-4,5-dihydro-2H-benzo[e]indazoles were found as new CSIs of which the bioactive configuration was locked. Among them, compounds C1 and C2 displayed the best activity, with tubulin polymerization IC₅₀ of 3.4 and 1.5 μM, and growth IC50 of low nanomolar concentrations against human colon cancer cell lines. In addition, compound C1 showed excellent broad-spectrum antitumor activity in the NCI-60 Human Tumor Cell Lines Screen, encouraging further study of this antitumor compound.     

Discovery of a novel series of hDHODH inhibitors with anti-pulmonary fibrotic activities

Human dihydroorotate dehydrogenase (hDHODH) is a flavin-dependent enzyme essential to pyrimidine de novo biosynthesis, which serves as an attractive therapeutic target for the treatment of autoimmune disorders. A novel series of hDHODH inhibitors was developed based on a lead which was obtained by a medicinal chemistry exploration. Most compounds showed moderate to significant potency against hDHODH, compounds 5d, 5e, and 6a effectively inhibited the activities of hDHODH with IC₅₀ values from 0.9 to 2.8 μM. Further studies showed that compound 5e also effectively suppressed proliferation of the activated PBMCs (IC₅₀ = 20.35 μM). Surprisingly, compound 5e also showed anti-pulmonary fibrotic activity similar to that of pirfenidone in vitro assay. Therefore, compound 5e might have potential to be developed as a novel hDHODH inhibitors for autoimmune diseases therapy.