Design, synthesis and biological evaluation of novel hybrids targeting mTOR and HDACs for potential treatment of hepatocellular carcinoma

Near-Infrared Light-Driven Nanoparticles for Cancer Photoimmunotherapy by Synergizing Immune Cell Death and Epigenetic Regulation

Histone deacetylases (HDACs) are a class of epigenetic enzymes that are closely related to tumorigenesis and suppress the expression of tumor suppressor genes. Whereas the HDACs inhibitors can release DNA into the cytoplasm and trigger innate immunity. However, the high density of chromatin limits DNA damage and release. In this study, suitable nanosized CycNHOH NPs (150 nm) and CypNHOH NPs (85 nm) efficiently accumulate at the tumor site due to the enhanced permeability and retention (EPR) effect. In addition, robust single-linear oxygen generation and good photothermal conversion efficiency under NIR laser irradiation accelerated the DNA damage process. By effectively initiating immune cell death, CypNHOH NPs activated both innate and adaptive immunity by maturing dendritic cells, infiltrating tumors with natural killer cells, and activating cytotoxic T lymphocytes, which offer a fresh perspective for the development of photo-immunotherapy.

PP121, a dual inhibitor of tyrosine and phosphoinositide kinases, relieves airway hyperresponsiveness, mucus hypersecretion and inflammation in a murine asthma model

BACKGROUND

Tyrosine kinase and phosphoinositide kinase pathways play important roles in asthma formation. As a dual tyrosine and phosphoinositide kinase inhibitor, PP121 has shown anticancer efficacy in multiple tumors. However, the study of PP121 in pulmonary diseases is still limited. Herein, we investigated the therapeutic activities of PP121 in asthma treatment.

METHODS

Tension measurements and patch clamp recordings were made to investigate the anticontractile characteristics of PP121 in vitro. Then, an asthma mouse model was established to further explore the therapeutic characteristics of PP121 via measurement of respiratory system resistance, histological analysis and western blotting.

RESULTS

We discovered that PP121 could relax precontracted mouse tracheal rings (mTRs) by blocking certain ion channels, including L-type voltage-dependent Ca2+ channels (L-VDCCs), nonselective cation channels (NSCCs), transient receptor potential channels (TRPCs), Na+/Ca2+ exchangers (NCXs) and K+ channels, and accelerating calcium mobilization. Furthermore, PP121 relieved asthmatic pathological features, including airway hyperresponsiveness, systematic inflammation and mucus secretion, via downregulation of inflammatory factors, mucins and the mitogen-activated protein kinase (MAPK)/Akt signaling pathway in asthmatic mice.

CONCLUSION

In summary, PP121 exerts dual anti-contractile and anti-inflammatory effects in asthma treatment, which suggests that PP121 might be a promising therapeutic compound and shed new light on asthma therapy.

Virtual screening of novel mTOR inhibitors for the potential treatment of human colorectal cancer

The abnormal activation of the mTOR pathway is closely related to the occurrence and progression of cancer, especially colorectal cancer. In this study, a rational virtual screening strategy has been established and MT-5, a novel mTOR inhibitor with a quinoline scaffold, was obtained from the ChemDiv database. MT-5 showed potent kinase inhibitory activity (IC50: 8.90 μM) and antiproliferative effects against various cancer cell lines, especially HCT-116 cells (IC50: 4.61 μM), and this was 2.2-fold more potent than that of the cisplatin control (IC50: 9.99 μM). Western blot, cell migration, cycle arrest, and apoptosis assays were performed with HCT-116 cells to investigate the potential anticancer mechanism of MT-5. Metabolic stability results in vitro indicated that MT-5 exhibited good stability profiles in artificial gastrointestinal fluids, rat plasma, and liver microsomes. In addition, the key contribution of the residues around the binding pocket of MT-5 in binding to the mTOR protein was also investigated from a computational perspective.

Discovery of novel, potent, and orally bioavailable HDACs inhibitors with LSD1 inhibitory activity for the treatment of solid tumors

Histone deacetylases (HDACs) and lysine-specific demethylase 1 (LSD1) are attractive targets for epigenetic cancer therapy. There is an intimate interplay between the two enzymes. HDACs inhibitors have shown synergistic anticancer effects in combination with LSD1 inhibitors in several types of cancer. Herein, we describe the discovery of compound 5e, a highly potent HDACs inhibitor (HDAC1/2/6/8; IC₅₀ = 2.07/4.71/2.40/107 nM) with anti-LSD1 potency (IC₅₀ = 1.34 μM). Compound 5e exhibited marked antiproliferative activity in several cancer cell lines. 5e effectively induced mitochondrial apoptosis with G2/M phase arrest, inhibiting cell migration and invasion in MGC-803 and HCT-116 cancer cells. It also showed good liver microsomal stability and acceptable pharmacokinetic parameters in SD rats. More importantly, orally administered compound 5e demonstrated higher in vivo antitumor efficacy than SAHA in the MGC-803 (TGI = 71.5%) and HCT-116 (TGI = 57.6%) xenograft tumor models accompanied by good tolerability. This study provides a novel lead compound with dual inhibitory activity against HDACs and LSD1 to further develop epigenetic drugs for solid tumor therapy. Further optimization is needed to improve the LSD1 activity to achieve dual inhibitors with balanced potency on LSD1 and HDACs.

Turning down PI3K/AKT/mTOR signalling pathway by natural products: an in silico multi-target approach

The PI3K/AKT/mTOR pathway is a significant target for cancer drug discovery. Many efforts have focused on discovering new inhibitors against key kinase proteins involved in this pathway for cancer treatment. PI3K/mTOR dual inhibitors, such as PKI-179, have been reported to be more effective than agents that act only on a single protein target. The present computational study aimed to discover triple target inhibitors against PI3K, AKT, and mTOR proteins. Accordingly, the PI3K protein bound with the ligand was used as input for e-pharmacophore modelling to generate the pharmacophore hypothesis and then screened for a library of 270,540 natural products from the Zinc database resulting in 57,220 compounds that matched the hypothesis. These compounds were then docked into the active site of PI3K, resulting in 292 compounds with better docking scores than the co-crystallized ligand. These compounds were re-docked into AKT and mTOR proteins. Besides, MM-GBSA binding free energy calculations, MD simulations, and ADMET prediction were carried out, leading to 5 potential triple-target inhibitors namely, ZINC000014644152, ZINC000014760695, ZINC000014644839, ZINC000095099451, and ZINC000005998557. In conclusion, these inhibitors may be possible leads for inhibiting PI3K/AKT/mTOR pathway, and they may be further evaluated in vitro and clinically as anticancer agents.

Targeting the PI3K/AKT/mTOR Signaling Pathway in the Treatment of Human Diseases: Current Status, Trends, and Solutions

The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is one of the most important intracellular pathways involved in cell proliferation, growth, differentiation, and survival. Therefore, this route is a prospective biological target for treating various human diseases, such as tumors, neurodegenerative diseases, pulmonary fibrosis, and diabetes. An increasing number of clinical studies emphasize the necessity of developing novel molecules targeting the PI3K/AKT/mTOR pathway. This review focuses on recent advances in ATP-competitive inhibitors, allosteric inhibitors, covalent inhibitors, and proteolysis-targeting chimeras against the PI3K/AKT/mTOR pathway, and highlights possible solutions for overcoming the toxicities and acquired drug resistance of currently available drugs. We also provide recommendations for the future design and development of promising drugs targeting this pathway.

Ligand- and structure-based identification of novel CDK9 inhibitors for the potential treatment of leukemia

Cyclin-dependent kinase 9 (CDK9) plays a vital role in controlling cell transcription and has been an attractive target for cancer treatment. Herein, ten predictive models derived from 1330 unique molecules against CDK9 were constructed based on molecular fingerprints and graphs using two conventional machine learning and four deep learning methods. The evaluation results showed that FP-GNN deep learning architecture performed best for CDK9 inhibitors prediction with the highest BA and F1 values of 0.681 and 0.912 for testing set. We then performed virtual screening to identify new CDK9 inhibitors by incorporating the optimal established predictive model and molecular docking. Five compounds were identified to show broad anticancer activity against various cancer cell lines through bioassays. For example, C9 exhibited antiproliferative activities against HeLa, MOLM-13 and MDA-MB-231 with IC₅₀ values of 2.53, 3.92 and 11.65 μM. Kinase inhibition assay results demonstrated that these compounds displayed submicromolar (214 ∼ 504 nM) inhibitory activities against CDK9. Further cellular mechanism evaluation revealed that C9 suppressed the activity of CDK9 and interfered with the expression of Mcl-1 and cleaved PARP in MOLM-13 cells, resulting in the induction of cellular apoptosis. In addition, C9 displayed a good stability in rat liver microsomes, artificial gastrointestinal fluid and plasm. An online platform (called DEEPCDK9Pred) was developed based on the FP-GNN models to predict or design new CDK9 inhibitors. Collectively, our findings demonstrated that FP-GNN algorithm can achieve accurate prediction of CDK9 inhibitors and the subsequent discovery of C9 as a new potential CDK9 inhibitor deserves further structural modification for the treatment of leukemia.

Discovery of Novel Src Homology-2 Domain-Containing Phosphatase 2 and Histone Deacetylase Dual Inhibitors with Potent Antitumor Efficacy and Enhanced Antitumor Immunity

Both Src homology-2 domain-containing phosphatase 2 (SHP2) and histone deacetylase (HDAC) are important oncoproteins and potential immunomodulators. In this study, we first observed a synergistic antiproliferation effect of an allosteric SHP2 inhibitor (SHP099) and HDAC inhibitor (SAHA) in MV4-11 cells. Inspired by this result, a series of SHP2/HDAC dual inhibitors were designed based on the pharmacophore fusion strategy. Among these inhibitors, the most potent compound 8t showed excellent inhibitory activities against SHP2 (IC₅₀ = 20.4 nM) and HDAC1 (IC₅₀ = 25.3 nM). In particular, compound 8t exhibited improved antitumor activities compared with those of SHP099 and SAHA in vitro and in vivo. Our study also indicated that treatment with 8t could trigger efficient antitumor immunity by activating T cells, enhancing the antigen presentation function and promoting cytokine secretion. To our knowledge, we report the first small molecular SHP2/HDAC dual inhibitor and demonstrate a new strategy for cancer immunotherapy.

Overview of Research into mTOR Inhibitors

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that belongs to the phosphoinositide 3-kinase (PI3K)-related kinase (PIKK) family. The kinase exists in the forms of two complexes, mTORC1 and mTORC2, and it participates in cell growth, proliferation, metabolism, and survival. The kinase activity is closely related to the occurrence and development of multiple human diseases. Inhibitors of mTOR block critical pathways to produce antiviral, anti-inflammatory, antiproliferative and other effects, and they have been applied to research in cancer, inflammation, central nervous system diseases and viral infections. Existing mTOR inhibitors are commonly divided into mTOR allosteric inhibitors, ATP-competitive inhibitors and dual binding site inhibitors, according to their sites of action. In addition, there exist several dual-target mTOR inhibitors that target PI3K, histone deacetylases (HDAC) or ataxia telangiectasia mutated and Rad-3 related (ATR) kinases. This review focuses on the structure of mTOR protein and related signaling pathways as well as the structure and characteristics of various mTOR inhibitors. Non-rapalog allosteric inhibitors will open new directions for the development of new therapeutics specifically targeting mTORC1. The applications of ATP-competitive inhibitors in central nervous system diseases, viral infections and inflammation have laid the foundation for expanding the indications of mTOR inhibitors. Both dual-binding site inhibitors and dual-target inhibitors are beneficial in overcoming mTOR inhibitor resistance.

An Overview of the Biological Evaluation of Selected Nitrogen-Containing Heterocycle Medicinal Chemistry Compounds

Heterocyclic compounds are a class of compounds of natural origin with favorable properties and hence have major pharmaceutical significance. They have an exceptional adroitness favoring their use as diverse smart biomimetics, in addition to possessing an active pharmacophore in a complex structure. This has made them an indispensable motif in the drug discovery field. Heterocyclic compounds are usually classified according to the ring size, type, and the number of heteroatoms present in the ring. Among different heterocyclic ring systems, nitrogen heterocyclic compounds are more abundant in nature. They also have considerable pharmacological significance. This review highlights recent pioneering studies in the biological assessment of nitrogen-containing compounds, namely: triazoles, tetrazoles, imidazole/benzimidazoles, pyrimidines, and quinolines. It explores publications between April 2020 and February 2022 and will benefit researchers in medicinal chemistry and pharmacology. The present work is organized based on the size of the heterocyclic ring.

Synthesis and bioevaluation of diaryl urea derivatives as potential antitumor agents for the treatment of human colorectal cancer

The development of inhibitors targeting the PI3K-Akt-mTOR signaling pathway has been greatly hindered by the on-target AEs, such as hyperglycemia and hepatotoxicities. In this study, a series of diaryl urea derivatives has been designed and synthesized based on clinical candidate gedatolisib (6aa), and most of the newly synthesized derivatives showed kinase inhibitory and antiproliferative activities within nanomolar and submicromolar level, respectively. The terminal l-prolineamide substituted derivative 6 ab showed 8.6-fold more potent PI3Kα inhibitory activity (0.7 nM) and 4.6-fold more potent antiproliferative effect against HCT116 cell lines (0.11 μM) compared with control 6aa. The potential antitumor mechanism and efficacy of 6 ab in HCT116 xenograft models have also been evaluated, and found 6 ab showed comparable in vivo antitumor activity with 6aa. The safety investigations revealed that compound 6 ab exhibited more safer profiles in the selectivity of liver cells (selectivity index: >6.6 vs 1.85) and blood glucose regulation than 6aa. In addition, the in vitro stability assays also indicated our developed compound 6 ab possessed good metabolic stabilities.