Design, synthesis and biological evaluation of 4-(indolin-1-yl)-6-substituted-pyrido[3,2-d]pyrimidine derivatives as Mnk1/2 inhibitors.

The Mnk-eIF4E axis plays a crucial role in tumor development, and inhibiting Mnk kinases is a promising approach for cancer therapy. Starting with fragment WS23, a series of 4-(indolin-1-yl)-6-substituted-pyrido[3,2-d]pyrimidine derivatives were designed and synthesized. Among these derivatives, compound 15b showed the highest potency with IC50 values of 0.8 and 1.5 nM against Mnk1 and Mnk2, respectively. Additionally, it demonstrated good selectivity among 30 selected kinases. 15b significantly suppressed MOLM-13 and K562 cell lines growth and caused cell cycle arrest. Furthermore, the Western blot assay revealed that 15b effectively downregulated the downstream proteins p-eIF4E, Mcl-1, and c-myc. Additionally, 15b exhibited remarkable stability in rat plasma and rat and human microsomes. In vivo anti-tumor activity study suggested that treatment with 15b suppressed tumor growth in LL/2 syngeneic models. These findings highlight the potential of 15b as a novel and potent Mnks inhibitor, which deserves further investigation.

Targeting Myeloid Leukemia-1 in Cancer Therapy: Advances and Directions.

As a tripartite cell death switch, B-cell lymphoma protein 2 (Bcl-2) family members precisely regulate the endogenous apoptosis pathway in response to various cell signal stresses through protein-protein interactions. Myeloid leukemia-1 (Mcl-1), a key anti-apoptotic Bcl-2 family member, is positioned downstream in the endogenous apoptotic pathway and plays a central role in regulating mitochondrial function. Mcl-1 is highly expressed in a variety of hematological malignancies and solid tumors, contributing to tumorigenesis, poor prognosis, and chemoresistance, making it an attractive target for cancer treatment. This Perspective aims to discuss the mechanism by which Mcl-1 regulates apoptosis and non-apoptotic functions in cancer cells and to outline the discovery and optimization process of potent Mcl-1 modulators. In addition, we summarize the structural characteristics of potent inhibitors that bind to Mcl-1 through multiple co-crystal structures and analyze the cardiotoxicity caused by current Mcl-1 inhibitors, providing prospects for rational targeting of Mcl-1.

Induction of ferroptosis: A new strategy for the control of bacterial infections.

The continued rise of drug-resistant bacterial infections heightens a threat of a pandemic of antimicrobial resistance to the global health. The urgency of infection control against antimicrobial-resistant bacteria is evident. Ferroptosis, a newly defined form of iron-dependent cell death characterized by lipid peroxidation, has garnered substantial interest since this programmed cell death was associated with pathophysiological processes of many diseases. Exploring whether ferroptosis could be utilized in infectious diseases holds significant importance for discovering novel antimicrobial approaches. Recent years have witnessed significant progress with respect to elucidating the mechanisms that govern ferroptosis induction and its roles in bacterial pathogenesis and host-pathogen interactions. In this review, we discuss the mechanisms of targeting ferroptosis and/or iron homeostasis for the control of antimicrobial-resistant bacterial infections. These implications may inform and enable effective therapeutic strategies against pathogen infection and provide novel insights into the potential applications of ferroptosis to address the global bacterial resistance crisis.

Co-augmentation of a transport gene mfsT1 in Mycolicibacterium neoaurum with genome engineering to enhance ergothioneine production.

Ergothioneine (EGT) is a rare thiohistidine derivative with exceptional antioxidant properties. The blood level of EGT is considered highly reliable predictors for cardiovascular diseases and mortality, yet animals lack the ability to synthesize this compound. Free plasmids have been previously used to overexpress genes involved in the EGT biosynthetic pathway of Mycolicibacterium neoaurum. Here, we tentatively introduced a putative transporter gene mfsT1 into high-copy plasmids and sharply increased the ratio of extracellular EGT concentration from 18.7% to 44.9%. Subsequently, an additional copy of egtABCDE, hisG, and mfsT1 was inserted into the genome with a site-specific genomic integration tool of M. neoaurum, leading a 2.7 times increase in EGT production. Co-enhancing the S-adenosyl-L-methionine regeneration pathway, or alternatively, the integration of three copies of egtABCDE, hisG and mfsT1 into the genome further increased the total EGT yield by 16.1% (64.6 mg/L) and 21.7% (67.7 mg/L), respectively. After 168-h cultivation, the highest titer reached 85.9 mg/L in the latter strain with three inserted copies. This study provided a solid foundation for genome engineering to increase the production of EGT in M. neoaurum.

8-Hydroxyquinoline derivatives suppress GLI1-mediated transcription through multiple mechanisms.

Aberrant activation of the Hedgehog (Hh) signaling pathway has been observed in various human malignancies. Glioma-associated oncogene transcription factor 1 (GLI1) is the ultimate effector of the canonical Hh pathway and has also been identified as a common regulator of several tumorigenic pathways prevalent in Hh-independent cancers. The anti-cancer potential of GLI1 antagonism with small molecule inhibitors has demonstrated initial promise; however, the continued development of GLI1 inhibitors is still needed. We previously identified a scaffold containing an 8-hydroxyquinoline as a promising lead GLI1 inhibitor (compound 1). To further develop this scaffold, we performed a systematic structure-activity relationship study to map the structural requirements of GLI1 inhibition by this chemotype. A series of biophysical and cellular experiments identified compound 39 as an enhanced GLI1 inhibitor with improved activity. In addition, our studies on this scaffold suggest a potential role for SRC family kinases in regulating oncogenic GLI1 transcriptional activity.

CSF1R inhibitors are emerging immunotherapeutic drugs for cancer treatment.

Colony-Stimulating Factor-1 Receptor (CSF1R) is a receptor tyrosine kinase that controls the differentiation and maintenance of most tissue-resident macrophages and bone-resorbing osteoclasts. Mutations of CSF1R have been implicated in neurodegeneration, skeletal anomalies, and cancers. Activation of CSF1R by endogenous cytokine ligation to the ectodomain triggers the autophosphorylation of the intracellular tyrosine kinase domain, and thereafter, activation of several downstream pro-survival kinase cascades, including PI3K, ERK1/2, and JNK. The immunological role of CSF1R in regulating tumor-associate macrophages (TAMs) have been well-documented. TAMs harboring activated CSF1R release tumorigenic cytokines, which further deconditioning tumor microenvironment to a protumoral phenotype. Pharmacological inhibition of CSF1R has emerged as a promising antitumor strategy, with PLX3397 (pexidartinib) been approved by the FDA for the treatment of tenosynovial giant cell tumor in 2019. Research around developing novel small-molecule CSF1R inhibitors, as well as expanding their potential indications, have drawn numerous attentions thenceforward. Herein, we've comprehensively reviewed the latest progression of CSF1R inhibitors under clinical and preclinical studies. Key findings of CSF1R targeted therapies either as monotherapy or combinatorial therapy have also been discussed.

Small molecules targeting γ-secretase and their potential biological applications.

The γ-secretase is a large transmembrane protein complex composed of four distinct units. It has aroused numerous attention over the past two decades as its intriguing role in mediating intramembrane proteolysis. γ-Secretase controls the cleavage of a broad ranged substrates, part of which have implicated in the pathogenesis of Alzheimer's disease, inflammation, and tumorigenesis. The disclosure of the atomic structure of the γ-secretase complex through cryo-EM in recent years has facilitated the understanding of its physiological roles, as well as enabled rational design of novel γ-secretase targeting molecules. This review highlights the recent progress of γ-secretase inhibitors and modulators under either clinical or preclinical stages, as well as their potential uses against various biological indications.

Affinity-based protein profiling identifies vitamin D3 as a heat shock protein 70 antagonist that regulates hedgehog transduction in murine basal cell carcinoma.

Vitamin D3 (VD3) is a seco-steroid that inhibits the Hedgehog (Hh) signaling pathway. Initial studies suggested its anti-Hh activity results from direct inhibition of Smoothened, a seven-transmembrane cell surface receptor that is a key regulator of the Hh signaling cascade. More recently, a role for the Vitamin D Receptor in mediating inhibition of Hh-signaling by seco-steroid has been suggested. Herein, an affinity-based protein profiling study was carried out to better understand the cellular proteins that govern VD3-mediated anti-Hh activity. We synthesized a novel biotinylated VD3 analogue (8) for use as a chemical probe to explore cellular binding targets of the seco-steroidal scaffold. Through a series of pull-down experiments and follow up mass spectrum analyses, heat shock protein 70 (Hsp70) was identified as a primary binding protein of VD3. Hsp70 was validated as a binding target of VD3 through a series of biochemical and cellular assays. VD3 bound with micromolar affinity to Hsp70. In addition, both selective knockdown of Hsp70 expression and pharmacological inhibition of its activity with known Hsp70 inhibitors suppressed Hh-signaling transduction in murine basal cell carcinoma cells, suggesting that Hsp70 regulates proper Hh-signaling. Additional cellular assays suggest that VD3 and its seco-steroidal metabolites inhibit Hh-signaling through different mechanisms.

Structure-based virtual screening identifies an 8-hydroxyquinoline as a small molecule GLI1 inhibitor.

The glioma-associated family of transcription factors (GLI) have emerged as a promising therapeutic target for a variety of human cancers. In particular, GLI1 plays a central role as a transcriptional regulator for multiple oncogenic signaling pathways, including the hedgehog (Hh) signaling pathway. We undertook a computational screening approach to identify small molecules that directly bind GLI1 for potential development as inhibitors of GLI-mediated transcription. Through these studies, we identified compound 1, which is an 8-hydroxyquinoline, as a high-affinity binder of GLI1. Compound 1 inhibits GLI1-mediated transcriptional activity in several Hh-dependent cellular models, including a primary model of murine medulloblastoma. We also performed a series of computational analyses to define more clearly the mechanism(s) through which 1 inhibits GLI1 function after binding. Our results strongly suggest that binding of 1 to GLI1 does not prevent GLI1/DNA binding nor disrupt the GLI1/DNA complex, but rather, it induces specific conformational changes in the overall complex that prevent proper GLI function. These results highlight the potential of this compound for further development as an anti-cancer agent that targets GLI1.

Medulloblastoma drugs in development: Current leads, trials and drawbacks.

Medulloblastoma (MB) is the most common malignant brain tumor in children. Current treatment for MB includes surgical resection, radiotherapy and chemotherapy. Despite significant progress in its management, a portion of children relapse and tumor recurrence carries a poor prognosis. Based on their molecular and clinical characteristics, MB patients are clinically classified into four groups: Wnt, Hh, Group 3, and Group 4. With our increased understanding of relevant molecular pathways disrupted in MB, the development of targeted therapies for MB has also increased. Targeted drugs have shown unique privileges over traditional cytotoxic therapies in balancing efficacy and toxicity, with many of them approved and widely used clinically. The aim of this review is to present the recent progress on targeted chemotherapies for the treatment of all classes of MB.

Inhibition of hedgehog signaling by stereochemically defined des-triazole itraconazole analogues.

Dysregulation of the hedgehog (Hh) signaling pathway is associated with cancer occurrence and development in various malignancies. Previous structure-activity relationships (SAR) studies have provided potent Itraconazole (ITZ) analogues as Hh pathway antagonists. To further expand on our SAR for the ITZ scaffold, we synthesized and evaluated a series of compounds focused on replacing the triazole. Our results demonstrate that the triazole region is amenable to modification to a variety of different moieties; with a single methyl group representing the most favorable substituent. In addition, nonpolar substituents were more active than polar substituents. These SAR results provide valuable insight into the continued exploration of ITZ analogues as Hh pathway antagonists.

Truncated Itraconazole Analogues Exhibiting Potent Anti-Hedgehog Activity and Improved Drug-like Properties.

We conducted a structure-activity relationship study to explore simplified analogues of the itraconazole (ITZ) scaffold for their ability to inhibit the hedgehog (Hh) signaling pathway. These analogues were based on exploring the effects of chemical modifications to the linker and triazolone/side chain region of ITZ. Analogue 11 was identified as the most potent compound in our first generation, with an IC50 value of 81 nM in a murine Hh-dependent basal cell carcinoma. Metabolic identification studies led us to identify truncated piperazine (26) as the major metabolite in human liver microsomes (HLMs) and an improved Hh pathway inhibitor (IC50 = 22 nM). This work verifies that continued truncation of the ITZ scaffold is a practical method to maintain potent anti-Hh activity while also reducing the molecular weight for the ITZ scaffold and achieving improved pharmacokinetic properties.

Structure-Activity Relationship Studies of Vitamin†D3 Analogues Containing an Ether or Thioether Linker as Hedgehog Pathway Inhibitors.

The Hedgehog (Hh) signaling pathway is critical for embryonic patterning and postembryonic tissue regeneration. Constitutive pathway activation has also been linked to human malignancies such as basal cell carcinoma (BCC) and medulloblastoma; therefore, multiple small-molecule scaffolds that inhibit Hh signaling are in development. Previously, Grundmann's alcohol, also known as the "northern region" of vitamin D3 (VD3), has been identified as a moderate Hh pathway inhibitor. In this study, isomers of Grundmann's alcohol with different orientations of the C4 hydroxy group and C3α proton were investigated to determine the optimal configuration for this hexahydroindane scaffold with respect to Hh inhibition. A series of analogues containing Grundmann's alcohol linked to a substituted phenyl or benzyl ring through an ether or thioether linker were synthesized and evaluated for their anti-Hh activity. Of these, analogue 17 ((1R,3aR,4R,7aR)-1-[(R)-1,5-dimethylhexyl]-4-(4-aminophenoxy)-7a-methyloctahydro-1H-indene) demonstrated potent anti-Hh activity in Hh-dependent BCC cells and did not activate canonical vitamin D receptor signaling, demonstrating its selective nature for the Hh signaling pathway.

Synthesis, biological evaluation and molecular modeling studies of psammaplin A and its analogs as potent histone deacetylases inhibitors and cytotoxic agents.

In this study, a concise synthetic method of psammaplin A was achieved from 3-bromo-4-hydroxybenzaldahyde and hydantoin through a four-step synthesis via Knoevenagel condensation, hydrolysis, oximation and amidation in 37% overall yield. A collection of novel psammaplin A analogs focused on the variations of substituents at the benzene ring and modifications at the oxime moiety were synthesized. Among all the synthesized compounds, 5d and 5e showed better HDAC inhibition than psammaplin A and comparable cytotoxicity against four cancer cell lines (PC-3, MCF-7, A549 and HL-60). Molecular docking and dynamics simulation revealed that (i) hydrogen atom of the oxime group interacts with Asp99 of HDAC1 through a water bridged hydrogen bond and (ii) a hydroxyl group is optimal attached on the para-position of benzene, interacting with Glu203 at the entrance to the active site tunnel.

Synthesis and biological evaluation of quinoline derivatives as potential anti-prostate cancer agents and Pim-1 kinase inhibitors.

In this work, a series of quinoline derivatives were designed and synthesized as antitumor agents. Most quinolines showed potent anti-proliferative activity against human prostatic cancer PC-3 cell line. Among which, 9d, 9f and 9g were the most effective compounds with GI50 values of 2.60, 2.81 and 1.29 µM, respectively. Structure-activity relationship analysis indicated that the secondary amine linked quinoline and pyridine ring played an important role in the anti-proliferative effects. Mechanistic studies revealed that 9g was a potential Pim-1 kinase inhibitor with abilities of cell cycle arrest and apoptosis induction. Considering of the increased activity of Pim-1 in prostate cancer, such compounds have potential to be developed as anti-prostate cancer agents.

Identification of N-(6-mercaptohexyl)-3-(4-pyridyl)-1H-pyrazole-5-carboxamide and its disulfide prodrug as potent histone deacetylase inhibitors with in vitro and in vivo anti-tumor efficacy.

In this study, a collection of N-(6-mercaptohexyl)-3-substituted-1H-pyrazole-5-carboxamide HDAC inhibitors was developed. Among them, 15k was identified as the most potent inhibitor against total HDACs with IC50 of 0.008 µM. Further isoenzyme assays revealed that 15k and its analogs have a preference for HDAC1-3 (class I) and HDAC6 (class IIb) isoforms. The enzyme-based potencies of 15k were 2- to 11-fold higher than those of Vorinostat. The disulfide prodrug 18 was found to be potent cytotoxic agent against a panel of seven tumor cells, causing hyper-acetylation of histone and non-histone proteins in cellular level. In addition, 18 demonstrated a notable in vivo anti-tumor activity in HCT-116 xenografted model. This study provides further possibility of developing novel thiol-based HDAC inhibitors for the treatment of cancer.

Design and synthesis of substituted pyrido[3,2-d]-1,2,3-triazines as potential Pim-1 inhibitors.

A novel series of substituted pyrido[3,2-d]-1,2,3-triazines were designed and synthesized as Pim-1 inhibitors through scaffold hopping. Most of the derivatives showed potent in vitro Pim-1 inhibitory activities and anti-proliferative effects toward prostate cancer cells. Among them, 6b, 6h and 6m showed the best Pim-1 inhibitory activity with IC50 values of 0.69, 0.60 and 0.80 µM, respectively. Furthermore, compounds 6b, 6i, 6j and 6m showed strong inhibitory activity to human prostate cancer LNcap and PC-3 cell lines with IC50 values at low micromolar level. Structure-activity relationship analysis revealed that appropriate substitutions at C-6 positions contributed to the kinase inhibition and antiproliferative effects. Moreover, western blot assay suggested that 6j could decrease the levels of p-BAD and p-4E-BP1 in a dose-dependent manner in PC-3 cells. Docking studies showed that 3-N of the scaffold formed a hydrogen bond with Lys67, aromatic 4-aniline formed a key π-π stack with Phe49. Taken together, this study might provide the first sight for developing the pyrido[3,2-d]-1,2,3-triazine scaffold as novel Pim-1 inhibitors.

Novel thiol-based histone deacetylase inhibitors bearing 3-phenyl-1H-pyrazole-5-carboxamide scaffold as surface recognition motif: Design, synthesis and SAR study.

A series of novel thiol-based histone deacetylase (HDAC) inhibitors bearing 3-phenyl-1H-pyrazole-5-carboxamide scaffold as surface recognition motif was designed, synthesized, and evaluated for their HDAC inhibition activity. Among them, 15j (IC50=0.08µM) was identified as a better inhibitor than Vorinostat (IC50=0.25µM) against total HDACs. In addition, Structure-activity relationships (SAR) analyses indicated that (i) compounds with different substituents on pyrazole N-1 position exhibited superior activities than those on pyrazole N-2 position, (ii) variation of functional groups on N-1'-alkyl chain terminus followed the trends of carboxyl group>hydroxyl group≫alkyl group, and (iii) methylation on pyrazole C-4 position diminished the HDAC inhibition activity. The SAR will guide us to further refine compounds bearing 3-phenyl-1H-pyrazole-5-carboxamide scaffold to achieve better HDAC inhibitors.

[Synthesis and antitumor activity of S-hexyl(heptyl) substituted ethanethioate derivatives].

To simplify the macrocyclic fragment and to modify the zinc binding group of the natural product apicidin, two series of S-hexyl (heptyl) ethanethioate derivatives were designed and synthesized. Twenty-six compounds were synthesized and confirmed with 1H NMR, IR, MS and HR-MS spectrum, which were not reported. Take vorinostat as control, their antiporliferative activities against cancer cell lines, MCF-7 and HL-60, were tested with MTT assay or trypan blue staining method. Generally in both series it was found that, the chiral carbon atom at 7 position is not necessary, compounds II-1, II-3, II-6 and II-13 showed good activity on HL-60 cells in vitro, with the IC50 values less than 10 micromol x L(-1). II-7 and II-8 showed stronger activity against MCF-7 than Vorinostat, with the IC50 of 3.19 and 6.29 micromol x L(-1), respectively.