Development Of Small Molecule Inhibitors Research Articles

Combination therapy involving HSP90 inhibitors for combating cancer: an overview of clinical and preclinical progress.

The molecular chaperone heat shock protein 90 (HSP90) regulates multiple crucial signalling pathways in cancer by driving the maturation of key signalling components, thereby playing a crucial role in tumorigenesis and drug resistance in cancer. Inhibition of HSP90 results in metastable conformational collapse of its client proteins and their proteasomal degradation. Considerable efforts have been devoted to the development of small-molecule inhibitors targeting HSP90, and more than 20 inhibitors have been evaluated in clinical trials for cancer therapy. However, owing to disadvantages such as organ toxicity and drug resistance, only one HSP90 inhibitor has been approved for use in clinical settings. In recent years, HSP90 inhibitors used in combination with other anti-cancer therapies have shown remarkable potential in the treatment of cancer. HSP90 inhibitors work synergistically with various anti-cancer therapies, including chemotherapy, targeted therapy, radiation therapy and immunotherapy. HSP90 inhibitors can improve the pharmacological effects of the above-mentioned therapies and reduce treatment resistance. This review provides an overview of the use of combination therapy with HSP90 inhibitors and other anti-cancer therapies in clinical and preclinical studies reported in the past decade and summarises design strategies and prospects for these combination therapies. Altogether, this review provides a theoretical basis for further research and application of these combination therapies in the treatment of cancer.

Internal m 6 A and m 7 G RNA modifications in hematopoietic system and acute myeloid leukemia.

Epitranscriptomics focuses on RNA modifications-mediated post-transcriptional regulation of gene expression. The current decade has witnessed tremendous progress in understanding the landscapes and biological functions of RNA modifications as prompted by potent analytical approaches. The hematopoietic system provides a lifelong supply of blood cells, and gene expression is tightly modulated during the differentiation of hematopoietic stem cells (HSCs). Dysregulation of gene expression during hematopoiesis may lead to severe disorders, including acute myeloid leukemia (AML). Emerging evidence has indicated the involvement of mRNA modification system in normal hematopoiesis and AML pathogenesis, which led to the accelerating development of small-molecule inhibitors targeting N6-methyladenosine (m 6 A) modification machinery for treatment. Here, we summarize the latest findings and address the state-of-the-art knowledge on the role of m 6 A and N7-methylguanine (m 7 G) in both physiological and pathological conditions in the hematopoietic system. Furthermore, we discuss the therapeutic potential and limitations of cancer treatment targeting m 6 A.

Recent Advances on Small-Molecule Inhibitors of Lipocalin-like Proteins.

Lipid transfer proteins (LTPs) are crucial players in nonvesicular lipid trafficking. LTPs sharing a lipocalin lipid transfer domain (lipocalin-like proteins) have a wide range of biological functions, such as regulating immune responses and cell proliferation, differentiation, and death as well as participating in the pathogenesis of inflammatory, metabolic, and neurological disorders and cancer. Therefore, the development of small-molecule inhibitors targeting these LTPs is important and has potential clinical applications. Herein, we summarize the structure and function of lipocalin-like proteins, mainly including retinol-binding proteins, lipocalins, and fatty acid-binding proteins and discuss the recent advances on small-molecule inhibitors for these protein families and their applications in disease treatment. The findings of our Perspective can provide guidance for the development of inhibitors of these LTPs and highlight the challenges that might be faced during the procedures.

Abstract 4482: Development of small molecule inhibitors of lipocalin 2 for the treatment of aggressive cancers

Abstract Lipocalin-2 (LCN2), a secreted protein pivotal in iron homeostasis, immune responses, siderophore transport, and epithelial cell differentiation. LCN2 is highly abundant in aggressive forms of many cancers including breast, pancreatic, ovarian, and esophageal cancer. Elevated LCN2 levels in aggressive tumors correlate with heightened cancer cell motility, proliferation, angiogenesis, invasion, and metastasis. After the protein folds it makes a barrel structure which encloses a three-calyx pocket that can bind and transport molecules. A first generation of small molecule inhibitors (SMIs) targeting LCN2 demonstrated efficacy in attenuating the proliferative capacity of Inflammatory breast cancer (IBC) cells. IBC stands as a rare and highly aggressive variant, accounting for 1 to 5% of all BC cases, with 20-30% presenting as de novo metastatic disease. In the previous studies the concentration of LCN2 inhibitors to reduce cell proliferation in 50% was around 10 µM. In pursuit of better LCN2 SMIs, we conducted in-silico analysis using a library of 369,000 ligands. Through the High-Performance Computer Facility at UPR Río Piedras, we employed AutoDock Vina for virtual screening, targeting the LCN2-calyx with Lys134 as the central coordinate. Docking protocols, predicting binding affinities, identified 8,162 out of 327,638 ligands that have been docked already with values below -9.6 kcal/mol for further consideration. The next phase involves subjecting these potential inhibitors to the SwissADME tool for a comprehensive evaluation of absorption, distribution, metabolism, and excretion parameters, as well as pharmacokinetics, drug-likeness, and medicinal chemistry considerations. The parameters to be evaluated are the Lipinski rules, which states that an orally active drug may have a maximum of one violation and the pann-assay interference compounds (PAINS) alerts tool, a source of false positives for biologically active compounds. The top candidates, exhibit binding affinities within the range of -11.5 to -12.2. After SwissADME filtering, we will re-rank the ligand list, identifying 30 commercially available candidates for subsequent cell viability assays in SUM149 (TNBC) and SUM190 (HER2+) cell lines. This multifaceted approach integrates computational methodologies with rigorous experimental validation, paving the way for potential therapeutic interventions in IBC treatment. Citation Format: Marienid Flores-Colón, Cristal A. Peña-Vázquez, Eliud Hernández-O'Farril, Luis E. Vázquez-Quiñones, Pablo E. Vivas-Mejía. Development of small molecule inhibitors of lipocalin 2 for the treatment of aggressive cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4482.

Abstract 3239: Targeting the GAS41 YEATS domain in non-small cell lung cancer with novel small molecules

Abstract Background: Glioma amplified sequence 41 (GAS41) belongs to the Yaf9, ENL, AF9, Taf14, and Sas5 (YEATS) domain family of epigenetic reader proteins. This domain preferentially recognizes acetylated lysine residues on chromatin to facilitate gene expression by recruiting chromatin remodeling and transcription activating complexes. The YEATS4 gene encoding for GAS41 protein is frequently amplified in NSCLC patient samples relative to normal lung tissue, and GAS41 protein is overexpressed in NSCLC cells. In knockdown experiments using NSCLC xenograft mouse models, GAS41 has been shown to be essential for NSCLC tumor growth. In mutagenesis studies, the YEATS domain residues responsible for acetylation reader activity were found to be essential for NSCLC cellular proliferation and tumor progression. Thus, the YEATS domain of GAS41 represents an attractive target for the development of small-molecule inhibitors as potential therapeutics for NSCLC. Results: We developed the first-in-class small-molecule inhibitors for the GAS41 YEATS domain. Using an NMR-based fragment screen, we identified a hit with low millimolar binding affinity. Structure-based drug design followed by extensive medicinal chemistry optimization yielded the potent and selective inhibitor DLG-369 with sub-micromolar inhibition of the GAS41 YEATS domain interaction with acylated histones. Using the NanoBRET platform, we showed that DLG-369 selectively disrupts the association of GAS41 YEATS with chromatin in mammalian cells. Furthermore, DLG-369 inhibits proliferation of NSCLC cell lines without affecting normal lung fibroblasts. In transcriptomic experiments, DLG-369 treatment regulates expression of multiple genes in NSCLC cells, including upregulation of the critical tumor suppressor genes CDKN1A and CYR61 and downregulation of chemokine genes CXCL5 and CXCR4 associated with NSCLC progression. Conclusions: We developed DLG-369, a potent inhibitor of the GAS41 YEATS domain with activity in NSCLC cellular models. DLG-369 potently binds to the YEATS domain acetylation reader pocket and disrupts GAS41 recognition of acetylation in cells. DLG-369 potently reduces proliferation and drives differential expression of key genes associated with NSCLC. DLG-369 can serve as a chemical probe to further interrogate the biological role of the GAS41 YEATS domain in NSCLC and other cancers for potential therapeutic implications. Citation Format: Alyssa Winkler, Dymytrii Listunov, Brian Linhares, Joshua Ray, Sidney Weaver, Sergey Zolov, Venkat Keshamouni, Jolanta Grembecka, Tomaszc Cierpicki. Targeting the GAS41 YEATS domain in non-small cell lung cancer with novel small molecules [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3239.

PPII-AEAT: Prediction of protein-protein interaction inhibitors based on autoencoders with adversarial training

Protein-protein interactions (PPIs) have shown increasing potential as novel drug targets. The design and development of small molecule inhibitors targeting specific PPIs are crucial for the prevention and treatment of related diseases. Accordingly, effective computational methods are highly desired to meet the emerging need for the large-scale accurate prediction of PPI inhibitors. However, existing machine learning models rely heavily on the manual screening of features and lack generalizability. Here, we propose a new PPI inhibitor prediction method based on autoencoders with adversarial training (named PPII-AEAT) that can adaptively learn molecule representation to cope with different PPI targets. First, Extended-connectivity fingerprints and Mordred descriptors are employed to extract the primary features of small molecular compounds. Then, an autoencoder architecture is trained in three phases to learn high-level representations and predict inhibitory scores. We evaluate PPII-AEAT on nine PPI targets and two different tasks, including the PPI inhibitor identification task and inhibitory potency prediction task. The experimental results show that our proposed PPII-AEAT outperforms state-of-the-art methods.

Molecular modeling studies of Indoline Scaffold derivatives as PD‐1/PD‐L1 pathway inhibitors by QSAR, molecular docking and molecular dynamics simulation techniques

AbstractIn recent years, blocking the interaction of programmed cell death receptor‐1 (PD‐1) and programmed cell death ligand‐1 (PD‐L1) has been recognized as one of the promising cancer therapies. Due to the many limitations of monoclonal antibodies, the development of small molecule inhibitors targeting PD‐1/PD‐L1 is imminent. This study aims to systematically investigate the interaction mechanisms of novel PD‐1/PD‐L1 inhibitors containing indoline backbone structures using 3D/2D‐QSAR modeling, molecular docking, molecular dynamics (MD) simulation, and ADMET prediction. The performance and predictive ability of the constructed QSAR models were evaluated by internal and external validation techniques. Topomer CoMFA and HQSAR models showed good reliability and predictive capability. By searching for R‐groups in the Topomer search module and combining the existing molecules with high activity contribution values, 24 new compounds with theoretically high activity were obtained, which showed desirable docking scores, appropriate ADMET properties, and good stability. This work not only provides a reliable QSAR model as a valuable screening tool for the development of future drugs targeting PD‐1/PD‐L1, but also makes the newly designed inhibitors expected to be potential PD‐1/PD‐L1 inhibitors that can be used for further synthesis and characterization to obtain novel anti‐cancer drugs targeting PD‐1/PD‐L1.

Iso-ADP-Ribose Fluorescence Polarization Probe for the Screening of RNF146 WWE Domain Inhibitors.

Poly-ADP-ribosylation is an important protein post-translational modification with diverse biological consequences. After binding poly-ADP-ribose on axis inhibition protein 1 (AXIN1) through its WWE domain, RING finger protein 146 (RNF146) can ubiquitinate AXIN1 and promote its proteasomal degradation and thus the oncogenic WNT signaling. Therefore, inhibiting the RNF146 WWE domain is a potential antitumor strategy. However, due to a lack of suitable screening methods, no inhibitors for this domain have been reported. Here, we developed a fluorescence polarization (FP)-based competition assay for the screening of RNF146 WWE inhibitors. This assay relies on a fluorescently tagged iso-ADP-ribose tracer compound, TAMRA-isoADPr. We report the design and synthesis of this tracer compound and show that it is a high-affinity tracer for the RNF146 WWE domain. This provides a convenient assay and will facilitate the development of small-molecule inhibitors for the RNF146 WWE domain.

Protein tyrosine phosphatases as emerging targets for cancer immunotherapy.

Contemporary strategies in cancer immunotherapy, despite remarkable success, remain constrained by inherent limitations such as suboptimal patient responses, the emergence of drug resistance, and the manifestation of pronounced adverse effects. Consequently, the need for alternative strategies for immunotherapy becomes clear. Protein tyrosine phosphatases (PTPs) wield a pivotal regulatory influence over an array of essential cellular processes. Substantial research has underscored the potential in targeting PTPs to modulate the immune responses and/or regulate antigen presentation, thereby presenting a novel paradigm for cancer immunotherapy. In this review, we focus on recent advances in genetic and biological validation of several PTPs as emerging targets for immunotherapy. We also highlight recent development of small molecule inhibitors and degraders targeting these PTPs as novel cancer immunotherapeutic agents.

Abstract B092: CDK8 and CXCL2 remodel the tumor microenvironment to contribute to KRASG12D small molecule inhibition resistance in pancreatic ductal adenocarcinoma

Abstract Mutations in KRAS are a dominant driver of pancreatic ductal adenocarcinoma (PDAC), with over 50% of PDAC patients presenting with KRASG12D mutations. The recent development of small molecule inhibitors targeting KRASG12D has enabled effective targeting of mutant KRAS signaling and suppression of tumor growth; however, the contribution of the tumor microenvironment to the therapeutic efficacy of KRASG12D inhibition and mechanisms of resistance to KRASG12D suppression remain to be fully elucidated. Here, we employed spatial transcriptomics and proteomics to evaluate cancer cell intrinsic and extrinsic responses to KRASG12D inhibition with MRTX1133. MRTX1133 treatment was associated with increased antigen presenting cells (APCs), T cells, and putative tumor-restraining fibroblasts within proximity to cancer cells, suggesting that antigen presentation and remodeling of the local microenvironment facilitates an effective response to KRASG12D inhibition. In the context of relapsed MRTX1133 treated tumors, single cell RNA sequencing and validation identified CDK8 as an intrinsic mediator of resistance and CXCL2 as an extrinsic mediator of resistance. Together, these studies identify APCs and CDK8 as therapeutic targets for enabling long term responses to small molecule KRASG12D inhibition with MRTX1133. Citation Format: Kathleen M. McAndrews, Krishnan K. Mahadevan, Bingrui Li, Amari M. Sockwell, Sami J. Morse, Patience J. Kelly, Michelle L. Kirtley, Meagan R. Conner, Sarah I. Patel, Shreyasee V. Khumbar, Kent A. Arian, Yasaman Barekatain, Barbara A. Moreno Diaz, Hengyu Lyu, Hikaru Sugimoto, Lakshmi Kavitha Sthanam, Navid Sobhani, Francesca Paradiso, Vincent Bernard, Paola Guerrero, Haoqiang Ying, Anirban Maitra, Timothy P. Heffernan, Raghu Kalluri. CDK8 and CXCL2 remodel the tumor microenvironment to contribute to KRASG12D small molecule inhibition resistance in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B092.

Abstract A027: Development of small molecule inhibitors of the Ku-DNA interaction: Impacts on NHEJ, DDR signaling, optimizing genome editing technologies, and therapeutic intervention for the treatment of cancer

Abstract DNA-PK, the DNA-dependent protein kinase is a validated target for cancer therapeutics that drives the DNA damage response (DDR) and plays a critical role in the non-homologous end joining (NHEJ) DNA repair pathway. NHEJ is responsible for the repair of DNA double strand breaks (DSB), particularly those induced by ionizing radiation (IR). The generation of DNA DSBs drives clinical efficacy of radiation therapy and numerous DNA damaging chemotherapeutic drugs used to treat cancer. Modulating the DSB repair pathways is an effective mechanism to increase clinical efficacy of IR and certain chemotherapeutic regimens. We have taken the novel approach to inhibit target the DDR and NHEJ by developing small molecule inhibitors of the DSB sensor Ku, and its interaction with DNA. The Ku heterodimer serves as initiator of the NHEJ pathway following DSB induction and is the key DNA-binding component of the DNA-PK. We have created an extensive library of Ku DNA binding inhibitors (Ku-DBis) and demonstrate a direct interaction with the Ku heterodimer and potent inhibition of Ku-DNA binding and DNA-PK catalytic activity. In vitro analysis of a series of Ku truncation mutants defines the necessary domains for Ku-DBi activity. Ku-DBi’s show potent inhibition of in vitro and cellular NHEJ and, as a result, potentiate cellular sensitivity to DSB-inducing agents. Enhancement of sensitivity is a function of inhibiting DNA-PKcs autophosphorylation and dysregulation of signaling to the DDR. Recent chemical optimization has identified independent pharmacophores that drive off-target cytotoxicity, direct Ku inhibitory potency, and enhance cellular uptake activity. These data served as the basis for creation of a novel series of Ku-DBi’s towards interrogating NHEJ and DDR signaling in vivo, optimizing genome editing technologies, and therapeutic intervention for the treatment of cancer. Citation Format: John J. Turchi, Pamela L. Mendoza-Munoz, Pamela S. VanderVere-Carozza, Navnath S. Gavande, Joseph R. Dynlacht, Joy E. Garrett, Dineshsinha Chauhan, Katherine S. Pawelczak. Development of small molecule inhibitors of the Ku-DNA interaction: Impacts on NHEJ, DDR signaling, optimizing genome editing technologies, and therapeutic intervention for the treatment of cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr A027.

Molecular recognition of ITIM/ITSM domains with SHP2 and their allosteric effect.

Src homology 2-domain-containing tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase that is widely expressed in a variety of cells and regulates the immune response of T cells through the PD-1 pathway. However, the activation mechanism and allosteric effects of SHP2 remain unclear, hindering the development of small molecule inhibitors. For the first time, in this study, the complex structure formed by the intact PD-1 tail and SHP2 was modeled. The molecular recognition and conformational changes of inactive/active SHP2 versus ITIM/ITSM were compared based on prolonged MD simulations. The relative flexibility of the two SH2 domains during MD simulations contributes to the recruitment of ITIM/ITSM and supports the subsequent conformational change of SHP2. The binding free energy calculation shows that inactive SHP2 has a higher affinity for ITIM/ITSM than active SHP2, mainly because the former's N-SH2 refers to the α-state. In addition, a significant decrease in the contribution to the binding energy of certain residues (e.g., R32, S34, K35, T42, and K55) of conformationally transformed SHP2 contributes to the above result. These detailed changes during conformational transition will provide theoretical guidance for the molecular design of subsequent novel anticancer drugs.

The Burgeoning Significance of Liquid-Liquid Phase Separation in the Pathogenesis and Therapeutics of Cancers.

Liquid-liquid phase separation (LLPS) is a physiological phenomenon that parallels the mixing of oil and water, giving rise to compartments with diverse physical properties. Biomolecular condensates, arising from LLPS, serve as critical regulators of gene expression and control, with a particular significance in the context of malignant tumors. Recent investigations have unveiled the intimate connection between LLPS and cancer, a nexus that profoundly impacts various facets of cancer progression, including DNA repair, transcriptional regulation, oncogene expression, and the formation of critical membraneless organelles within the cancer microenvironment. This review provides a comprehensive account of the evolution of LLPS from the molecular to the pathological level. We explore the mechanisms by through which biomolecular condensates govern diverse cellular physiological processes, encompassing gene expression, transcriptional control, signal transduction, and responses to environmental stressors. Furthermore, we concentrate on potential therapeutic targets and the development of small-molecule inhibitors associated with LLPS in prevalent clinical malignancies. Understanding the role of LLPS and its interplay within the tumor milieu holds promise for enhancing cancer treatment strategies, particularly in overcoming drug resistance challenges. These insights offer innovative perspectives and support for advancing cancer therapy.

Targeting KRAS-Mutated Gastrointestinal Malignancies with Small-Molecule Inhibitors: A New Generation of Breakthrough Therapies.

Kirsten rat sarcoma virus (KRAS) is one of the most important and frequently mutated oncogenes in cancer and the mutational prevalence is especially high in many gastrointestinal malignancies, including colorectal cancer and pancreatic ductal adenocarcinoma. The KRAS protein is a small GTPase that functions as an "on/off" switch to activate downstream signaling, mainly through the mitogen-activated protein kinase pathway. KRAS was previously considered undruggable because of biochemical constraints; however, recent breakthroughs have enabled the development of small-molecule inhibitors of KRAS G12C. These drugs were initially approved in lung cancer and have now shown substantial clinical activity in KRAS G12C-mutated pancreatic ductal adenocarcinoma as well as colorectal cancer when combined with anti-EGFR monoclonal antibodies. Early data are encouraging for other gastrointestinal cancers as well and many other combination strategies are being investigated. Several new KRAS G12C inhibitors and novel inhibitors of other KRAS alterations have recently entered the clinic. These molecules employ a variety of innovative mechanisms and have generated intense interest. These novel drugs are especially important as KRAS G12C is rare in gastrointestinal malignancies compared with other KRAS alterations, representing potentially groundbreaking advances. Soon, the rapidly evolving landscape of novel KRAS inhibitors may substantially shift the therapeutic landscape for gastrointestinal cancers and offer meaningful survival improvements.

Loss of the methylarginine reader function of SND1 confers resistance to hepatocellular carcinoma.

Staphylococcal nuclease Tudor domain containing 1 (SND1) protein is an oncogene that 'reads' methylarginine marks through its Tudor domain. Specifically, it recognizes methylation marks deposited by protein arginine methyltransferase 5 (PRMT5), which is also known to promote tumorigenesis. Although SND1 can drive hepatocellular carcinoma (HCC), it is unclear whether the SND1 Tudor domain is needed to promote HCC. We sought to identify the biological role of the SND1 Tudor domain in normal and tumorigenic settings by developing two genetically engineered SND1 mouse models, an Snd1 knockout (Snd1 KO) and an Snd1 Tudor domain-mutated (Snd1 KI) mouse, whose mutant SND1 can no longer recognize PRMT5-catalyzed methylarginine marks. Quantitative PCR analysis of normal, KO, and KI liver samples revealed a role for the SND1 Tudor domain in regulating the expression of genes encoding major acute phase proteins, which could provide mechanistic insight into SND1 function in a tumor setting. Prior studies indicated that ectopic overexpression of SND1 in the mouse liver dramatically accelerates the development of diethylnitrosamine (DEN)-induced HCC. Thus, we tested the combined effects of DEN and SND1 loss or mutation on the development of HCC. We found that both Snd1 KO and Snd1 KI mice were partially protected against malignant tumor development following exposure to DEN. These results support the development of small molecule inhibitors that target the SND1 Tudor domain or the use of upstream PRMT5 inhibitors, as novel treatments for HCC.

A multiplexed time-resolved fluorescence resonance energy transfer ultrahigh-throughput screening assay for targeting the SMAD4-SMAD3-DNA complex.

The transforming growth factor-beta (TGFβ) signaling pathway plays crucial roles in the establishment of an immunosuppressive tumor microenvironment, making anti-TGFβ agents a significant area of interest in cancer immunotherapy. However, the clinical translation of current anti-TGFβ agents that target upstream cytokines and receptors remains challenging. Therefore, the development of small-molecule inhibitors specifically targeting SMAD4, the downstream master regulator of the TGFβ pathway, would offer an alternative approach with significant therapeutic potential for anti-TGF-β signaling. In this study, we present the development of a cell lysate-based multiplexed time-resolved fluorescence resonance energy transfer (TR-FRET) assay in an ultrahigh-throughput screening (uHTS) 1536-well plate format. This assay enables simultaneous monitoring of the protein‒protein interaction between SMAD4 and SMAD3, as well as the protein‒DNA interaction between SMADs and their consensus DNA-binding motif. The multiplexed TR-FRET assay exhibits high sensitivity, allowing the dynamic analysis of the SMAD4-SMAD3-DNA complex at single-amino acid resolution. Moreover, the multiplexed uHTS assay demonstrates robustness for screening small-molecule inhibitors. Through a pilot screening of an FDA-approved bioactive compound library, we identified gambogic acid and gambogenic acid as potential hit compounds. These proof-of-concept findings underscore the utility of our optimized multiplexed TR-FRET platform for large-scale screening to discover small-molecule inhibitors that target the SMAD4-SMAD3-DNA complex as novel anti-TGFβ signaling agents.

Leveraging the Fragment Molecular Orbital Method to Explore the PLK1 Kinase Binding Site and Polo-Box Domain for Potent Small-Molecule Drug Design.

Polo-like kinase 1 (PLK1) plays a pivotal role in cell division regulation and emerges as a promising therapeutic target for cancer treatment. Consequently, the development of small-molecule inhibitors targeting PLK1 has become a focal point in contemporary research. The adenosine triphosphate (ATP)-binding site and the polo-box domain in PLK1 present crucial interaction sites for these inhibitors, aiming to disrupt the protein's function. However, designing potent and selective small-molecule inhibitors can be challenging, requiring a deep understanding of protein-ligand interaction mechanisms at these binding sites. In this context, our study leverages the fragment molecular orbital (FMO) method to explore these site-specific interactions in depth. Using the FMO approach, we used the FMO method to elucidate the molecular mechanisms of small-molecule drugs binding to these sites to design PLK1 inhibitors that are both potent and selective. Our investigation further entailed a comparative analysis of various PLK1 inhibitors, each characterized by distinct structural attributes, helping us gain a better understanding of the relationship between molecular structure and biological activity. The FMO method was particularly effective in identifying key binding features and predicting binding modes for small-molecule ligands. Our research also highlighted specific "hot spot" residues that played a critical role in the selective and robust binding of PLK1. These findings provide valuable insights that can be used to design new and effective PLK1 inhibitors, which can have significant implications for developing anticancer therapeutics.

Quantitative Biochemical Analysis of Deadenylase Enzymes Using Fluorescence and Chemiluminescence-Based Assays.

Deadenylase enzymes play a key role in mRNA degradation and RNA processing. In this chapter, we describe two activity assays for the quantitative biochemical analysis of deadenylase enzymes, which can easily be adapted for other nuclease enzymes. The assays use distinct principles of detection, which are based on differential annealing of a probe complementary to the substrate RNA or detection of adenosine monophosphate (AMP). The assays are sensitive, flexible, and can be used in low-throughput tube-based formats and 96-well or 384-well plate formats. The assays rely on plate reader detection and can be carried out using manual pipetting or robotic liquid handling equipment. In addition to two activity assays, we describe differential scanning fluorimetry (thermal shift assay) as a complementary assay that allows the direct characterization of ligand binding to deadenylase enzymes. The assays can be useful for the characterization of deadenylase variants and are particularly suitable for the discovery and development of small-molecule inhibitors of deadenylase enzymes.

Development of small molecule inhibitors targeting RNA helicase DHX33 as anti-cancer agents

RNA helicase DHX33 has been identified to be a critical factor in promoting cancer development. Genetic deletion of DHX33 significantly blocks tumorigenesis. Importantly, its helicase activity was found to be pivotal for exerting cellular functions. Herein we used a helicase-based high throughput screening (HTS) to discover DHX33 inhibitors from Chembridge chemical library containing 15,000 small molecules. We identified a hit compound containing benzimidazole ring that demonstrated activity against DHX33 with certain selectivity. Further structural optimization led to the design and synthesis of a series of analog inhibitors. Considering the potential role of DHX33 in cancer development, the compounds were evaluated based on the cytotoxicity activity in U251-MG cancer cells in vitro. Among them, compound IVa (KY386) was identified to be a selective inhibitor for DHX33 helicase with potent anti-cancer activity and moderate metabolic stability. These results support the promising role of DHX33 inhibitors for development of novel anti-cancer drugs.

Serine/threonine kinase of Mpox virus: computational modeling and structural analysis

Kinases catalyze phosphoryl transfer from a nucleoside triphosphate (usually ATP) to an amino acid on a protein for activation purposes. Although kinases are well-appreciated drug targets in different viruses and cancers, these enzymes in poxviruses received limited attention from the research community. In poxvirus, the production of infectious particles in the infected cells depends on a serine/threonine protein kinase (STK) that activates proteins implicated in the assembly of new virions. This work aimed to elucidate the structure and dynamics of the major kinase STK from Mpox virus (Orthopoxvirus). A state-of-the-art computational approach was employed to decipher the structure and dynamics of the STK using AlphaFold2 and molecular dynamics (MD) simulations. Although the predicted structure showed an atypical kinase, the overall structural fold is conserved. Binding free energy calculations via Molecular Mechanics/Generalized Born and Surface Area (MM/GBSA) determined the hotspot residues contributing to binding of ATP. The structural analysis in this work provides insights into the structure and behavior of STK in Mpox virus and possibly its closest members of Poxviridae. These findings also set the basis for setting up a thorough experimental investigation to understand the enzymatic mechanism, peptide substrate binding, and the development of small-molecule inhibitors against this kinase. Communicated by Ramaswamy H. Sarma