Small molecules as modulators of the proteostasis machinery: Implication in cardiovascular diseases.

With the escalating prevalence of cardiovascular diseases, the substantial socioeconomic burden on healthcare systems is intensifying. Accumulating empirical evidence underscores the pivotal role of the proteostasis network in regulating cardiac homeostasis and function. Disruptions in proteostasis may contribute to the loss of protein function or the acquisition of toxic functions, which are intricately linked to the development of cardiovascular ailments such as atrial fibrillation, heart failure, atherosclerosis, and cardiac aging. It is widely acknowledged that the proteostasis network encompasses molecular chaperones, autophagy, and the ubiquitin proteasome system (UPS). Consequently, the proteostasis network emerges as an appealing target for therapeutic interventions in cardiovascular diseases. Numerous small molecules, acting as modulators of the proteostasis machinery, have exhibited therapeutic efficacy in managing cardiovascular diseases. This review centers on elucidating the role of the proteostasis network in various cardiovascular diseases and explores the potential of small molecules as therapeutic agents.

Discovery of novel hypoxia-activated, nitroimidazole constructed multi-target kinase inhibitors on the basis of AZD9291 for the treatment of human lung cancer.

A group of 4-(1-methyl-1H-indol-3-yl)pyrimidin-2-amine derivatives containing a hypoxia-activated nitroimidazole group were designed as EGFR inhibitors. Among this series, A14 was identified as the optimal compound, exhibiting potent anti-proliferative activities against H1975 and HCC827 cells. Under hypoxic condition, the anti-proliferative activities of A14 improved by 4-6-fold (IC50 < 10 nM), indicating its hypoxia-selectivity. A14's high potency may be attributed to its inhibition against multiple kinases, including EGFR, JAK2, ROS1, FLT3, FLT4 and PDGFRα, which was confirmed by binding assays on a panel of 30 kinases. Furthermore, A14 exhibited good bio-reductive property and could bind with nucleophilic amino acids after being activated under hypoxic conditions. With its anti-proliferative activities and selectivity for hypoxia and oncogenic kinases, A14 shows promise as a multi-target kinase inhibitor for cancer therapy.

Design, synthesis and biological evaluation of the tumor hypoxia-activated PROTACs bearing caged CRBN E3 ligase ligands.

Tumor hypoxia-activated proteolysis targeting chimeras (ha-PROTACs) 9 and 10 were designed and synthesized by incorporating the hypoxia-activated leaving group (1-methyl-2-nitro-1H-imidazol-5-yl)methyl or 4­nitrobenzyl into the structure of the cereblon (CRBN) E3 ligand of an epidermal growth factor receptor 19 deletions (EGFRDel19-based PROTAC 8. The in vitro protein degradation assay demonstrated that 9 and 10 could effectively and selectively degrade EGFRDel19 in tumor hypoxia. Meanwhile, these two compounds showed higher potency in inhibiting cell viability and migration, as well as in promoting cells apoptosis in tumor hypoxia. Moreover, nitroreductase reductive activation assay indicated that prodrugs 9 and 10 could successfully release the active compound 8. This study confirmed the feasibility to develop ha-PROTACs to enhance the selectivity of PROTACs by caging CRBN E3 ligase ligand.

Chemoproteomics reveals arctigenin as a phagophore-closure blocker via targeting ESCRT-I subunit VPS28.

Arctigenin is the active ingredient of the traditional medicines Arctium lappa and Fructus Arctii and has been extensively investigated for its diverse pharmacological functions, including its novel anti-austerity activity. Although several mechanisms have been proposed, the direct target of arctigenin to induce anti-austerity activity remains unclear. In this study, we designed and synthesized photo-crosslinkable arctigenin probes and utilized them in the chemoproteomic profiling of potential target proteins directly in living cells. Vacuolar protein sorting-associated protein 28 (VPS28), a key subunit of the ESCRT-I complex implicated in phagophore closure, was successfully identified. Unexpectedly, we found that arctigenin degraded VPS28 via the ubiquitin-proteasome pathway. We also demonstrated that arctigenin induces a prominent phagophore closure-blockade phenotype in PANC-1 cells. To the best of our knowledge, this is the first report of a small molecule acting as a phagophore-closure blocker and a VPS28 degrader. The arctigenin-modulating phagophore closure provides a new druggable target for cancers that rely heavily on autophagy activation and may also be used for other diseases associated with the ESCRT system.

Design, synthesis and biological evaluation of novel tumor hypoxia-activated EGFR tyrosine kinase inhibitors.

Hypoxia is widespread in solid tumors, such as NSCLC, and has become a very attractive target. On the basis of AZD9291 scaffold, novel hypoxia-targeted EGFR inhibitors without the acrylamide warhead but containing hypoxic reductive activation groups were described. Among them, compound JT21 exhibited impressive inhibitory activity (IC50 = 23 nM) against EGFRL858R/T790M and displayed about 21-fold inhibitory activity decrease against EGFRwt. Under hypoxia, JT21 exhibited more significant proliferation inhibitory activities against H1975 cells (IC50 = 7.39 ± 2.20 nM) and HCC827 cells (IC50 = 5.88 ± 0.85 nM) than that of AZD9291, which was about 5 times more effective than normoxia activities. Meanwhile, the weak inhibition effects on A549 and BEAS-2B cells suggested JT21 might be a selective inhibitor for EGFR mutations with low toxicity. Furthermore, JT21 could induce apoptosis of H1975 cells under hypoxia and showed good bio-reductive property.

Design, Synthesis, and Biological Evaluation of 2-Anilino-4-Triazolpyrimidine Derivatives as CDK4/HDACs Inhibitors.

Purpose: To enhance the cytotoxicities of our obtained CDK4 inhibitors and get CDK4/HDACs inhibitors with potent enzymatic inhibitory and anti-proliferative activities. Methods: A series of novel CDK4/HDACs inhibitors were designed and synthesized by incorporating the HDAC pharmacophores (hydroxylamine or o-diaminoaniline) into the basic structure of our newly obtained 2-anilino-4-triazolpyrimidine based CDK4 inhibitors. The enzymatic inhibitory (HDAC1, CDK2, CDK4, and CDK6) activities and cytotoxicities of these compounds were evaluated. Moreover, HDAC isoforms inhibitory activity, cell cycle arrest assay, cell apoptosis analysis, cell migration, and cell colony formation assay were performed for the representative compound 11k. Results: Most of these compounds showed excellent HDAC1 inhibitory activities (IC50s: 0.68~244.5 nM) and anti-proliferative activities against cancer cell lines. Some compounds displayed potent CDK4 inhibitory activities and a certain selectivity towards CDK2 and CDK6. Compound 11k exhibited potent enzymatic (CDK4: IC50=23.59 nM; HDAC1: IC50=61.11 nM; HDAC2: IC50=80.62 nM; HDAC6: IC50=45.33 nM) and anti-proliferative activities against H460, MDA-MB-468, HCT116, and HepG2 cell lines with IC50 values 1.20, 1.34, 2.07, and 2.66 µM, respectively. Further mechanistic studies revealed that compound 11k could arrest the cell cycle in G0/G1 phase and induce apoptosis in HCT116 and MDA-MB-468 cells. In addition, compound 11k significantly inhibited the migration and cell colony formation of H460 and HCT116 cells. Conclusion: This study suggested that the incorporation of the HDAC pharmacophore into CDK4 inhibitor scaffold to design CDK/HDAC inhibitors might be a tractable strategy to enhance the antitumor potency of compounds.

Development of hypoxia-activated PROTAC exerting a more potent effect in tumor hypoxia than in normoxia.

Hypoxia is a hallmark of many solid tumors, and it causes the overexpression of a variety of proteins including the epidermal growth factor receptor (EGFR). Many antitumor prodrugs have been designed to target hypoxia. Here we report the identification of a kind of hypoxia-activated proteolysis targeting chimera (ha-PROTAC) by introducing the hypoxia-activated leaving group (1-methyl-2-nitro-1H-imidazol-5-yl)methyl or 4-nitrobenzyl into the structure of an EGFRDel19-based PROTAC. Among the obtained molecules, ha-PROTAC 13 exhibits a more potent degradation activity for EGFRDel19 in hypoxia than in normoxia in HCC4006 cells. This is the first example of identifying a PROTAC to selectively act on tumors utilizing the characteristic of tumor hypoxia and provides a new approach for PROTAC development.

Pharmacokinetics, Urinary Excretion, and Pharmaco-Metabolomic Study of Tebipenem Pivoxil Granules After Single Escalating Oral Dose in Healthy Chinese Volunteers.

Tebipenem pivoxil (TBPM-PI), an oral carbapenem antibiotic, has shown special advantages in pediatric infections and was in urgent need in China. Although pharmacokinetics, urinary excretion, and metabolite information of its active form tebipenem (TBPM) has been reported, ethnic differences may exist among the Chinese and Japanese population. By now, no systematic pharmacokinetics, urinary excretion, metabolites, or safety information has been revealed to the Chinese population. The purpose of the present work was to investigate abovementioned information of TBPM-PI granules after oral single ascending doses of 100, 200, and 400 mg in Chinese volunteers. Based on the pharmacokinetic study, the urine pharmaco-metabolomic analysis was conducted to reveal metabolomic interruptions and metabolite information. The study design was a single-center, open-label, randomized, single-dose pharmacokinetic study of 36 healthy volunteers (with half of them being male and the other half female). Time to maximum concentration (T max) was reached at 0.50, 0.50, or 0.67 h for 100, 200, or 400 mg, respectively. The linear pharmacokinetic characteristic of maximum plasma concentration (C max) was detected over 100-200 mg. The area under the concentration time curve (AUC) was proportional to the dose in the range of 100-400 mg. The maximum urinary excretion rate was detected at 0-1 or 1-2 h for dose of 100 or 200-400 mg. Cumulative amount of TBPM excreted in urine by 24 h accounted up to 90, 95, and 80% of dose administered for three groups, respectively. The pharmaco-metabolomic analysis revealed urine metabolic trajectory of deviation at 0-1 or 1-2 h and gradually regressing back to the pre-dose group at the following time periods. Urine metabolites from M1 to M4 were identified, indicating ethnic difference in metabolites among the Chinese or Japanese population. The current work proved safety and tolerance of single-dose administration of oral TBPM-PI in Chinese healthy volunteers over doses of 100-400 mg. All these results provide pharmacokinetics, urine excretion, urine metabolomics, urine metabolites, and safety information in healthy Chinese volunteers after oral single ascending doses of TBPM-PI, benefitting further development and clinical utilities.

Design, synthesis, and biological study of 4-[(2-nitroimidazole-1H-alkyloxyl)aniline]-quinazolines as EGFR inhibitors exerting cytotoxicities both under normoxia and hypoxia.

PURPOSE: In order to get novel EGFR inhibitors exerting more potency in tumor hypoxia than in normoxia. METHODS: A series of 4-[(2-nitroimidazole-1H-alkyloxyl)aniline]-quinazolines were designed and synthesized, and their in vitro cytotoxicity and EGFR inhibitory activity were evaluated. Molecule docking study was performed for the representative compound. RESULTS: The structure-activity relationship (SAR) studies revealed that compounds bearing both meta-chloride and para-(2-nitroimidazole-1H-alkyloxy) groups on the aniline displayed potent inhibitory activities both in enzymatic and cellular levels. The most promising compound 16i potently inhibited EGFR with an IC50 value of 0.12 µM. Meanwhile, it manifested more potent cytotoxicity than the positive control lapatinib under tumor normoxia and hypoxia conditions (IC50 values of 1.59 and 1.09 µM against A549 cells, 2.46 and 1.35 µM against HT-29 cells, respectively). The proposed binding model of 16i in complex with EGFR was displayed by the docking results. CONCLUSION: This study provides insights for developing hypoxia-activated kinase inhibitors.

An overview of recent progress in siderophore-antibiotic conjugates.

Multi-drug resistant infections caused by Gram-negative bacteria have become one of the most important reasons for the failure of clinical anti-infective treatment. Siderophore-antibiotic conjugates, which were designed based on a "Trojan horse" strategy wherein features enabled active uptake to bypass the Gram-negative cell wall, have been expected to be a weapon for anti-infective treatment in the clinic. Herein, we review antibiotic drug design strategies based on mimics of nature siderophores reported in recent years, we also focus our attention on the relationship between the type of linker and the corresponding antibacterial activity.

CDK11p110 plays a critical role in the tumorigenicity of esophageal squamous cell carcinoma cells and is a potential drug target.

Esophageal squamous cell carcinoma (ESCC) is a serious malignancy with limited options for targeted therapy. The exploration of novel targeted therapies for combating ESCC is urgently needed. Cyclin-dependent kinases (CDKs) play important roles in the progression of cancers; however, the function of CDK11p110 (cyclin-dependent kinase 11p110) in ESCC is still unknown. Here, we investigated the effects and molecular mechanisms of CDK11p110 in the proliferation and growth of ESCC by examining the expression of CDK11p110 in ESCC tissues and by detecting phenotypic changes in ESCC cells after CDK11p110 knockdown or overexpression in vitro and in vivo. According to the tissue microarray analysis, compared with its expression level in normal tissues, the expression level of CDK11p110 was significantly elevated in ESCC tissues; this result was in concordance with the data in TCGA (The Cancer Genome Atlas) datasets. In addition, RNAi-mediated CDK11p110 silencing exerted a substantial inhibitory effect on the proliferation, clonogenicity and migration ability of ESCC cells. Further study indicated that CDK11p110 knockdown arrested ESCC cells in the G2/M phase of the cell cycle and induced cell apoptosis. Moreover, stable shRNA-mediated CDK11p110 knockdown inhibited tumor growth in an ESCC xenograft model, and overexpression of CDK11p110 enhanced tumor growth. In addition, the Ki67 proliferation index was closely associated with the elevation or depletion of CDK11p110 in vivo. In summary, this study provides evidence that CDK11p110 play a critical role in the tumorigenicity of ESCC cells, which suggests that CDK11p110 may be a promising therapeutic target in ESCC. Abbreviations: CDKs: cyclin-dependent kinases; CDK11: Cyclin-dependent kinase 11; CDK11p110: Cyclin-dependent kinase 11p110, the larger isomer of cyclin-dependent kinase 11; ESCC: esophageal squamous cell carcinoma; FACS: fluorescence-activated cell sorting; FDA: the Food and Drug Administration; TCGA: The Cancer Genome Atlas; TMA: tissue microarray.

Recent development of CDK inhibitors: An overview of CDK/inhibitor co-crystal structures.

The cyclin-dependent protein kinases (CDKs) are protein-serine/threonine kinases that display crucial effects in regulation of cell cycle and transcription. While the excessive expression of CDKs is intimate related to the development of diseases including cancers, which provides opportunities for disease treatment. A large number of small molecules are explored targeting CDKs. CDK/inhibitor co-crystal structures play an important role during the exploration of inhibitors. So far nine kinds of CDK/inhibitor co-crystals have been determined, they account for the highest proportion among the Protein Data Bank (PDB) deposited crystal structures. Herein, we review main co-crystals of CDKs in complex with corresponding inhibitors reported in recent years, focusing our attention on the binding models and the pharmacological activities of inhibitors.

Recent Development of Oridonin Derivatives with Diverse Pharmacological Activities.

Oridonin is one of the major components isolated from Isodon rubescens, a traditional Chinese medicine, and it has been confirmed to exhibit many kinds of biological activities including anticancer, anti-inflammation, antibacterial and so on. However, the poor pharmaceutical property limits the clinical applications of oridonin. So many strategies have been explored in the purpose of improving the potencies of oridonin, and structure modification is one thus way. This review outlines the landscape of the recent development of oridonin derivatives with diverse pharmacological activities, mainly focusing on the biological properties, structure-activity relationships, and mechanism of actions.

An overview of the binding models of FGFR tyrosine kinases in complex with small molecule inhibitors.

The fibroblast growth factor receptor (FGFR) family receptor tyrosine kinase (RTK) includes four structurally related members, termed as FGFR1, FGFR2, FGFR3, and FGFR4. Given its intimate role in the progression of several solid tumors, excessive FGFR signaling provides an opportunity for anticancer therapy. Along with extensive pharmacological studies validating the therapeutic potential of targeting the FGFRs for cancer treatment, co-crystal structures of FGFRs/inhibitors are continuously coming up to study the mechanism of actions and explore new inhibitors. Herein, we review the reported co-crystals of FGFRs in complex with the corresponding inhibitors, main focusing our attention on the binding models and the pharmacological activities of the inhibitors.

Development of the Third Generation EGFR Tyrosine Kinase Inhibitors for Anticancer Therapy.

Epidermal growth factor receptor (EGFR) is one of the most important targets in anticancer therapy. Till date, a large number of first and second generation EGFR tyrosine kinase inhibitors (TKIs) have been marketed or advanced into clinical studies. However, the occurrence of TKI-resistant mutations has led to the loss of efficacy of these inhibitors. In the purpose of overcoming resistant mutations and reducing side effects, lots of third generation EGFR inhibitors are explored with promising potencies against EGFR mutations while sparing wild-type EGFR. This review outlines the current landscape of the development of third generation EGFR inhibitors, mainly focusing on the biological properties, clinical status and structure-activity relationships.

Design, synthesis and biological evaluation of 6-(nitroimidazole-1H-alkyloxyl)-4-anilinoquinazolines as efficient EGFR inhibitors exerting cytotoxic effects both under normoxia and hypoxia.

A series of novel 6-(nitroimidazole-1H-alkyloxyl)-4-anilinoquinazoline derivatives (15a-15r) were designed, synthesized and evaluated as efficient EGFR inhibitors through introduction of hypoxia activated nitroimidazole moiety into the quinazoline scaffold of EGFR inhibitors. The majority of these newly synthesized compounds exhibited comparable EGFR inhibitory activities to gefitinib and moderate to excellent anti-proliferative activities against HT-29 cells under normoxia and hypoxia. The most promising compound 15c displayed the IC50 value of 0.47 nM against EGFR kinase and excellent cytotoxic effect against HT-29 cells under normoxia and hypoxia with the IC50 values of 2.21 µM and 1.62 µM, respectively. The mimic reductive activation study revealed that compound 15c exerted reductive activation properties under hypoxia, which were consistent with the in vitro metabolic study, wherein 15c was easily reductive activated under hypoxia and much more stable under normoxia. All these results suggested that 15c was a potential cancer therapeutic agent both under normoxia and hypoxia and was worth of further development.

Identification of novel 4-anilinoquinazoline derivatives as potent EGFR inhibitors both under normoxia and hypoxia.

A novel series of 4-anilinoquinazoline derivatives (19a-19t) were designed and synthesized through incorporation of the 2-nitroimidazole moiety into the 4-anilinoquinazoline scaffold of EGFR inhibitors. The most promising compound 19h displayed potent EGFR inhibitory activity with the IC50 value of 0.47 nM. It also strongly suppressed the proliferation of A549 and HT-29 cells with sub-micromolar IC50 values both under normoxia and hypoxia, which were several folds more potent than gefitinib and erlotinib. Further reductive mimic investigation revealed that 19h could be reductive activated under hypoxia and was fully consistent with the results of cell apoptotic assay and in vitro metabolism evaluation. Our results suggest that the incorporation of hypoxia-activated moiety into EGFR inhibitor scaffold might be a tractable strategy to overcome the tumor hypoxia.

Development of EGFR family small molecule inhibitors for anticancer intervention: an overview of approved drugs and clinical candidates.

The epidermal growth factor receptor (EGFR) family includes four structurally related receptor tyrosine kinases, termed as HER1 (EGFR, erbB1), HER2 (erbB2), HER3 (erbB3), and HER4 (erbB4). Given its intimate role in the development of several solid tumors, excessive HER signaling provides a unique opportunity for anticancer intervention. Along with extensive pharmacological studies validating the therapeutic potential of targeting the EGFR family for cancer therapy, kinase inhibitors of this family are continuously coming up and entering clinical studies. Herein, we review the EGFR family small molecule kinase inhibitors which have been approved or progressed into clinical studies, mainly focusing on their mechanisms of action, structure-activity relationships, binding modes, synthetic routes, and clinical status.

N-Benzyl-6-de-oxy-3,6-imino-methyl-ene-1,2,3,5-O-tetra-acetyl-α-d-1(S)-epiallo-furan-ose.

The mol-ecule of the title compound, C(22)H(27)NO(9), an azasugar derivative, consists of one benzene ring and two fused rings, which have the cis arrangement at the ring junctions, and gives a V-shaped geometry. The inter-planar angle between the five- and six-membered rings is 65.69 (11)°. The crystal structure is stablized by weak inter-molecular C-H⋯O hydrogen bonds.

1,2;5,6-Di-O-isopropyl-idene-3-C-nitro-methyl-α-d-allofuran-ose.

The mol-ecule of the title compound, C(13)H(21)NO(8), consists of two methyl-enedi-oxy rings and one tetra-hydro-furan ring. In the crystal, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into helical chains running along the 6(1) screw axis. Weak inter-molecular C-H⋯O hydrogen bonds help to stabilize the crystal packing. Voids of 245 Å(3) per unit cell occur.