Systematic Optimization of Potent and Orally Bioavailable Purine Scaffold as a Dual Inhibitor of Toll-Like Receptors 7 and 9

Exploring the Structural Attributes of Yoda1 for the Development of New-Generation Piezo1 Agonist Yaddle1 as a Vaccine Adjuvant Targeting Optimal T Cell Activation

Piezo1, a mechano-activated ion channel, has wide-ranging physiological and therapeutic implications, with the ongoing development of specific agonists unveiling cellular responses to mechanical stimuli. In our study, we systematically analyzed the chemical subunits in Piezo1 protein agonist Yoda1 to comprehend the structure-activity relationship and push forward next-generation agonist development. Preliminary screening assays for Piezo1 agonism were performed using the Piezo1-mCherry-transfected HEK293A cell line, keeping Yoda1 as a positive control. We introduce a novel Piezo1 agonist Yaddle1 (34, 0.40 μM), featuring a trifluoromethyl group, with further exploration through in vitro studies and density functional theory calculations, emphasizing its tetrel interactions, to act as an ambidextrous wedge between the domains of Piezo1. In contrast to the poor solubility of the established agonist Yoda1, our results showed that the kinetic solubility of Yaddle1 (26.72 ± 1.8 μM at pH 7.4) is 10-fold better than that of Yoda1 (1.22 ± 0.11 μM at pH 7.4). Yaddle1 (34) induces Ca2+ influx in human CD4+ T cell, suggesting its potential as a vaccine adjuvant for enhanced T cell activation.

Hit-to-lead optimization of 2-aminoquinazolines as anti-microbial agents against Leishmania donovani

Visceral leishmaniasis is a potentially fatal disease caused by infection by the intracellular protist pathogens Leishmania donovani or Leishmania infantum. Present therapies are ineffective because of high costs, variable efficacy against different species, the requirement for hospitalization, toxicity and drug resistance. Detailed analysis of previously published hit molecules suggested a crucial role of 'guanidine' linkage for their efficacy against L. donovani. Here we report the design of 2-aminoquinazoline heterocycle as a basic pharmacophore-bearing guanidine linkage. The introduction of various groups and functionality at different positions of the quinazoline scaffold results in enhanced antiparasitic potency with modest host cell cytotoxicity using a physiologically relevant THP-1 transformed macrophage infection model. In terms of the ADME profile, the C7 position of quinazoline was identified as a guiding tool for designing better molecules. The good ADME profile of the compounds suggests that they merit further consideration as lead compounds for treating visceral leishmaniasis.

Small-molecule agents for treating skin diseases

Skin diseases are a class of common and frequently occurring diseases that significantly impact daily lives. Currently, the limited effective therapeutic drugs are far from meeting the clinical needs; most drugs typically only provide symptomatic relief rather than a cure. Developing small-molecule drugs with improved efficacy holds paramount importance for treating skin diseases. This review aimed to systematically introduce the pathogenesis of common skin diseases in daily life, list related drugs applied in the clinic, and summarize the clinical research status of candidate drugs and the latest research progress of candidate compounds in the drug discovery stage. Also, it statistically analyzed the number of publications and global attention trends for the involved skin diseases. This review might provide practical information for researchers engaged in dermatological drugs and further increase research attention to this disease area.

Copper Catalyzed Three-Component Ullmann C-S Coupling in PEG for the Synthesis of 6-Aryl/alkylthio-purines

To tackle the environmental unfriendly issue in existing synthesis strategies for 6-substitued thiopurine derivatives, such as poor step economy, frequent use of malodorous organic sulfur starting materials, toxic organic solvents, and equivalent dosage of base, we have developed a CuI-catalyzed base-free three-component Ullmann C-S coupling synthetic strategy, featured using inorganic salt Na2S as the sulfur source and nontoxic PEG-600 as the solvent. The newly developed strategy is particularly effective for the synthesis of 6-arylthiopurines. The high catalytic efficiency in PEG-600 can be rationalized by the high soluble ability of CuI catalyst, likely due to the presence of multiple oxygen coordination sites in PEG.

Discovery and Development of Quinazolinones and Quinazolinediones for Ameliorating Nonalcoholic Fatty Liver Disease (NAFLD) by Modulating COP1-ATGL Axis

E3 ubiquitin ligase, Constitutive Photomorphogenic 1 (COP1) regulates turnover of Adipose Triglyceride Lipase (ATGL), the rate-limiting lipolytic enzyme. Genetic perturbation in the COP1-ATGL axis disrupts lipid homeostasis, leading to liver steatosis. Using drug development strategies, we herein report quinazolinone and quinazolinedione based modulators for COP1-ATGL axis. Systematic SAR studies and subsequent optimization were performed by incorporating relevant functional groups at the N1, N3, C5, and C6 positions of both scaffolds. Compounds' efficacy was evaluated by multiple biological assays and ADME profiling. The lead compound 86 could increase ATGL protein expression, reduce ATGL ubiquitination and COP1 autoubiquitination, and diminish lipid accumulation in hepatocytes in the nanomolar range. Oral administration of 86 abrogated triglyceride accumulation and resolved fibrosis in preclinical Nonalcoholic Fatty Liver Disease (NAFLD) model. The study thus establishes quinazolinedione as a viable chemotype to therapeutically modulate the activity of COP1 and ATGL in relevant clinical contexts.

Small molecule modulators of immune pattern recognition receptors

Pattern recognition receptors (PRRs) represent a re-emerging class of therapeutic targets for vaccine adjuvants, inflammatory diseases and cancer. In this review article, we summarize exciting developments in discovery and characterization of small molecule PRR modulators, focusing on Toll-like receptors (TLRs), NOD-like receptors (NLRs) and the cGAS-STING pathway. We also highlight PRRs that are currently lacking small molecule modulators and opportunities for chemical biology and therapeutic discovery.

Development of selective class I protein arginine methyltransferase inhibitors through fragment-based drug design approach

Protein arginine methyltransferases (PRMTs) catalyze the methylation of the terminal nitrogen atoms of the guanidino group of arginine of protein substrates. The aberrant expression of these methyltransferases is linked to various diseases, making them promising therapeutic targets. Currently, PRMT inhibitors are at different stages of clinical development, which validated their significance as drug targets. Structural Genomics Consortium (SGC) has reported several small fragment inhibitors as Class I PRMT inhibitors, which can be the starting point for rational drug development. Herein, we report the successful application of a fragment-based approach toward the discovery of selective Class I PRMT inhibitors. Structure-based ligand optimization was performed by strategic incorporation of fragment hits on the drug-like quinazoline core and subsequent fragment growth in the desired orientation towards identified hydrophobic shelf. A clear SAR was established, and the lead compounds 55 and 56 displayed potent inhibition of Class I PRMTs with IC50 values of 92 nM and 37 nM against PRMT4. We report the systematic development of potent Class I PRMT inhibitors with good potency and about 100-fold selectivity when tested against a panel of 31 human DNA, RNA, and protein lysine and arginine methyltransferases. These improved small molecules will provide new options for the development of novel potent and selective PRMT4 inhibitors.

Catalyzing the Future of Medicinal Chemistry Research in India

The present publication provides a comprehensive look at more than a decade (2010 to midyear of 2023) of medicinal chemistry research in India, focusing on contributions to medicinal chemistry and drug discovery from both Indian academia and industries. The work provides an overview of cutting-edge medicinal chemistry research along with the organic-transformation-based chemical research scenarios in India in the past decade. It also distinguishes areas of research as well as contributions from different federal research institutes, state universities, central universities, and private universities by their geographical locations around India. The paper takes broader stock of the situation by comparing the articles published in the two internationally acclaimed journals in the field, viz. Journal of Medicinal Chemistry and Organic Letters, which highlights the current research trends as well as the thrust needed at the grass-roots level to boost medicinal chemistry and drug discovery research in India. Finally, we believe that this discussion may create a pathway for policymakers and funding agencies to focus their efforts to motivate lesser inclined institutions as well as provide incentives to the institutions primarily involved in medicinal chemistry research, as they already have built capacity for such research.

Mitigating hERG Liability of Toll-Like Receptor 9 and 7 Antagonists through Structure-Based Design

hERG is considered to be a primary anti-target in the drug development process, as the K+ channel encoded by hERG plays an important role in cardiac re-polarization. It is desirable to address the hERG safety liability during early-stage development to avoid the expenses of validating leads that will eventually fail at a later stage. We have previously reported the development of highly potent quinazoline-based TLR7 and TLR9 antagonists for possible application against autoimmune disease. Initial experimental hERG assessment showed that most of the lead TLR7 and TLR9 antagonists suffer from hERG liability rendering them ineffective for further development. The present study herein describes a coordinated strategy to integrate the understanding from structure-based protein-ligand interaction to develop non- hERG binders with IC50 >30 μM with retention of TLR7/9 antagonism through a single point change in the scaffold. This structure-guided strategy can serve as a prototype for abolishing hERG liability during lead optimization.

Recent Advances on Small-Molecule Antagonists Targeting TLR7

Toll-like receptor 7 (TLR7) is a class of pattern recognition receptors (PRRs) recognizing the pathogen-associated elements and damage and as such is a major player in the innate immune system. TLR7 triggers the release of pro-inflammatory cytokines or type-I interferons (IFN), which is essential for immunoregulation. Increasing reports also highlight that the abnormal activation of endosomal TLR7 is implicated in various immune-related diseases, carcinogenesis as well as the proliferation of human immunodeficiency virus (HIV). Hence, the design and development of potent and selective TLR7 antagonists based on small molecules or oligonucleotides may offer new tools for the prevention and management of such diseases. In this review, we offer an updated overview of the main structural features and therapeutic potential of small-molecule antagonists of TLR7. Various heterocyclic scaffolds targeting TLR7 binding sites are presented: pyrazoloquinoxaline, quinazoline, purine, imidazopyridine, pyridone, benzanilide, pyrazolopyrimidine/pyridine, benzoxazole, indazole, indole, and quinoline. Additionally, their structure-activity relationships (SAR) studies associated with biological activities and protein binding modes are introduced.

Development, Optimization, and In Vivo Validation of New Imidazopyridine Chemotypes as Dual TLR7/TLR9 Antagonists through Activity-Directed Sequential Incorporation of Relevant Structural Subunits

Undesirable activation of endosomal toll-like receptors TLR7 and TLR9 present in specific immune cells in response to host-derived ligands is implicated in several autoimmune diseases and other contexts of autoreactive inflammation, making them important therapeutic targets. We report a drug development strategy identifying a new chemotype for incorporating relevant structural subunits into the basic imidazopyridine core deemed necessary for potent TLR7 and TLR9 dual antagonism. We established minimal pharmacophoric features in the core followed by hit-to-lead optimization, guided by in vitro and in vivo biological assays and ADME. A ligand-receptor binding hypothesis was proposed, and selectivity studies against TLR8 were performed. Oral absorption and efficacy of lead candidate 42 were established through favorable in vitro pharmacokinetics and in vivo pharmacodynamic studies, with IC₅₀ values of 0.04 and 0.47 μM against TLR9 and TLR7, respectively. The study establishes imidazopyridine as a viable chemotype to therapeutically target TLR9 and TLR7 in relevant clinical contexts.

Integration of Ligand-Based and Structure-Based Methods for the Design of Small-Molecule TLR7 Antagonists

Toll-like receptor 7 (TLR7) is activated in response to the binding of single-stranded RNA. Its over-activation has been implicated in several autoimmune disorders, and thus, it is an established therapeutic target in such circumstances. TLR7 small-molecule antagonists are not yet available for therapeutic use. We conducted a ligand-based drug design of new TLR7 antagonists through a concerted effort encompassing 2D-QSAR, 3D-QSAR, and pharmacophore modelling of 54 reported TLR7 antagonists. The developed 2D-QSAR model depicted an excellent correlation coefficient (R²_training: 0.86 and R²_test: 0.78) between the experimental and estimated activities. The ligand-based drug design approach utilizing the 3D-QSAR model (R²_training: 0.95 and R²_test: 0.84) demonstrated a significant contribution of electrostatic potential and steric fields towards the TLR7 antagonism. This consolidated approach, along with a pharmacophore model with high correlation (R_training: 0.94 and R_test: 0.92), was used to design quinazoline-core-based hTLR7 antagonists. Subsequently, the newly designed molecules were subjected to molecular docking onto the previously proposed binding model and a molecular dynamics study for a better understanding of their binding pattern. The toxicity profiles and drug-likeness characteristics of the designed compounds were evaluated with in silico ADMET predictions. This ligand-based study contributes towards a better understanding of lead optimization and the future development of potent TLR7 antagonists.

Application and prospect of targeting innate immune sensors in the treatment of autoimmune diseases

Dysregulation of auto-reactive T cells and autoantibody-producing B cells and excessive inflammation are responsible for the occurrence and development of autoimmune diseases. The suppression of autoreactive T cell activation and autoantibody production, as well as inhibition of inflammatory cytokine production have been utilized to ameliorate autoimmune disease symptoms. However, the existing treatment strategies are not sufficient to cure autoimmune diseases since patients can quickly suffer a relapse following the end of treatments. Pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), Nod-like receptors (NLRs), RIG-I like receptors (RLRs), C-type lectin receptors (CLRs) and various nucleic acid sensors, are expressed in both innate and adaptive immune cells and are involved in the development of autoimmune diseases. Here, we have summarized advances of PRRs signaling pathways, association between PRRs and autoimmune diseases, application of inhibitors targeting PRRs and the corresponding signaling molecules relevant to strategies targeting autoimmune diseases. This review emphasizes the roles of different PRRs in activating both innate and adaptive immunity, which can coordinate to trigger autoimmune responses. The review may also prompt the formulation of novel ideas for developing therapeutic strategies against autoimmune diseases by targeting PRRs-related signals.