ABSTRACT
Stimulator of interferon genes (STING) is a dimeric transmembrane adapter protein that plays a key role in the human innate immune response to infection and has been therapeutically exploited for its antitumor activity. The activation of STING requires its high-order oligomerization, which could be induced by binding of the endogenous ligand, cGAMP, to the cytosolic ligand-binding domain. Here we report the discovery through functional screens of a class of compounds, named NVS-STGs, that activate human STING. Our cryo-EM structures show that NVS-STG2 induces the high-order oligomerization of human STING by binding to a pocket between the transmembrane domains of the neighboring STING dimers, effectively acting as a molecular glue. Our functional assays showed that NVS-STG2 could elicit potent STING-mediated immune responses in cells and antitumor activities in animal models.
Subject(s)
Adaptor Proteins, Signal Transducing , Membrane Proteins , Animals , Humans , Adaptor Proteins, Signal Transducing/metabolism , Biological Assay , Cytosol , Immunity, Innate , Ligands , Membrane Proteins/metabolismABSTRACT
Histone deacetylase (HDAC) inhibitors have shown promise in treating various forms of cancer. However, many HDAC inhibitors from diverse structural classes have been associated with QT prolongation in humans. Inhibition of the human ether a-go-go related gene (hERG) channel has been associated with QT prolongation and fatal arrhythmias. To determine if the observed cardiac effects of HDAC inhibitors in humans is due to hERG blockade, a highly potent HDAC inhibitor devoid of hERG activity was required. Starting with dacinostat (LAQ824), a highly potent HDAC inhibitor, we explored the SAR to determine the pharmacophores required for HDAC and hERG inhibition. We disclose here the results of these efforts where a high degree of pharmacophore homology between these two targets was discovered. This similarity prevented traditional strategies for mitigating hERG binding/modulation from being successful and novel approaches for reducing hERG inhibition were required. Using a hERG homology model, two compounds, 11r and 25i, were discovered to be highly efficacious with weak affinity for the hERG and other ion channels.
Subject(s)
Acrylamides/toxicity , Antineoplastic Agents/toxicity , Ether-A-Go-Go Potassium Channels/antagonists & inhibitors , Histone Deacetylase Inhibitors/toxicity , Hydroxamic Acids/toxicity , Acrylamides/chemical synthesis , Acrylamides/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Drug Screening Assays, Antitumor , ERG1 Potassium Channel , HCT116 Cells , Half-Life , Histone Deacetylase Inhibitors/chemical synthesis , Histone Deacetylase Inhibitors/pharmacology , Humans , Hydroxamic Acids/chemical synthesis , Hydroxamic Acids/pharmacology , In Vitro Techniques , Mice , Mice, Nude , Microsomes, Liver/metabolism , Models, Molecular , Neoplasm Transplantation , Patch-Clamp Techniques , Radioligand Assay , Rats , Rats, Sprague-Dawley , Stereoisomerism , Structure-Activity Relationship , Tissue Distribution , Transplantation, HeterologousABSTRACT
Identification and structure-guided optimization of a series of 4-(pyrazol-4-yl)-pyrimidines as selective CDK4/6 inhibitors is reported herein. Several potency and selectivity determinants were established based on the X-ray crystallographic analysis of representative compounds bound to monomeric CDK6. Significant selectivity for CDK4/6 over CDK1 and CDK2 was demonstrated with several compounds in both enzymatic and cellular assays.
Subject(s)
Cyclin-Dependent Kinase 4/antagonists & inhibitors , Cyclin-Dependent Kinase 6/antagonists & inhibitors , Models, Molecular , Pyrazoles/chemical synthesis , Pyrimidines/chemical synthesis , Cell Line, Tumor , Crystallography, X-Ray , Cyclin-Dependent Kinase 4/chemistry , Cyclin-Dependent Kinase 6/chemistry , High-Throughput Screening Assays , Humans , Kinetics , Pyrazoles/chemistry , Pyrazoles/pharmacology , Pyrimidines/chemistry , Pyrimidines/pharmacology , Structure-Activity RelationshipABSTRACT
Inspired by natural product HDAC inhibitors, we prepared a series of conformationally restrained HDAC inhibitors based on the hydroxamic acid dacinostat (LAQ824, 7). Several scaffolds with improved biochemical and cellular potency, as well as attenuated hERG inhibition, were identified, suggesting that the introduction of molecular rigidity is a viable strategy to enhance HDAC binding and mitigate hERG liability. Further SAR studies around a 3-piperidin-3-ylindole moiety resulted in the discovery of compound 30, for which a unique conformation was speculated to contribute to overcoming increased lipophilicity and attenuating hERG binding. Separation of racemate 30 afforded 32, the R enantiomer, which demonstrated improved potency in both enzyme and cellular assays compared to dacinostat.
