C2-Symmetrical Terphenyl Derivatives as Small Molecule Inhibitors of Programmed Cell Death 1/Programmed Death Ligand 1 Protein-Protein Interaction.

The PD-1/PD-L1 complex is an immune checkpoint responsible for regulating the natural immune response, but also allows tumors to escape immune surveillance. Inhibition of the PD-1/PD-L1 axis positively contributes to the efficacy of cancer treatment. The only available therapeutics targeting PD-1/PD-L1 are monoclonal antibody-based drugs, which have several limitations. Therefore, small molecule compounds are emerging as an attractive alternative that can potentially overcome the drawbacks of mAb-based therapy. In this article, we present a novel class of small molecule compounds based on the terphenyl scaffold that bind to PD-L1. The general architecture of the presented structures is characterized by axial symmetry and consists of three elements: an m-terphenyl core, an additional aromatic ring, and a solubilizing agent. Using molecular docking, we designed a series of final compounds, which were subsequently synthesized and tested in HTRF assay and NMR binding assay to evaluate their activity. In addition, we performed an in-depth analysis of the mutual arrangement of the phenyl rings of the terphenyl core within the binding pocket of PD-L1 and found several correlations between the plane angle values and the affinity of the compounds towards the protein.

1,5-Disubstituted tetrazoles as PD-1/PD-L1 antagonists.

The progress in cancer survival and treatment has witnessed a remarkable transformation through the innovative approach of targeting the inhibitory immune checkpoint protein PD-1/PD-L1 complex by mAbs, e.g. pembrolizumab (Keytruda). While generating 17.2 billion U.S. dollars in revenue in 2021, the true significance of these developments lies in their ability to enhance cancer patient outcomes. Despite the proven efficacy of mAbs in inhibiting the PD-1/PD-L1 signaling pathways, they face significant challenges, including limited response rates, high production costs, missing oral bioavailability, and extended half-lives that can lead to immune-related adverse effects. A promising alternative approach involves the use of small molecules acting as PD-1/PD-L1 antagonists to stimulate PD-L1 dimerization. However, the precise mechanisms of action of these molecules remain partially understood, posing challenges to their development. In this context, our research focuses on the creation of a novel scaffold based on the Ugi tetrazole four-component reaction (UT-4CR) to develop low-molecular-weight inhibitors of PD-L1. Employing structure-based methods, we synthesized a library of small compounds using biphenyl vinyl isocyanide, leading to the discovery of a structure-activity relationship among 1,5-disubstituted tetrazole-based inhibitors. Supported by a cocrystal structure with PD-L1, these inhibitors underwent biophysical testing, including HTRF and protein NMR experiments, resulting in the identification of potent candidates with sub-micromolar PD-L1 affinities. This finding opens opportunities to the further development of a new class of PD-L1 antagonists, holding promise for improved cancer immunotherapy strategies.

Identification and characterization of a small molecule that activates thiosulfate sulfurtransferase and stimulates mitochondrial respiration.

The enzyme Thiosulfate sulfurtransferase (TST, EC 2.8.1.1), is a positive genetic predictor of diabetes type 2 and obesity. As increased TST activity protects against the development of diabetic symptoms in mice, an activating compound for TST may provide therapeutic benefits in diabetes and obesity. We identified a small molecule activator of human TST through screening of an inhouse small molecule library. Kinetic studies in vitro suggest that two distinct isomers of the compound are required for full activation as well as an allosteric mode of activation. Additionally, we studied the effect of TST protein and the activator on TST activity through mitochondrial respiration. Molecular docking and molecular dynamics (MD) approaches supports an allosteric site for the binding of the activator, which is supported by the lack of activation in the Escherichia coli. mercaptopyruvate sulfurtransferase. Finally, we show that increasing TST activity in isolated mitochondria increases mitochondrial oxygen consumption.

Multicomponent Macrocyclic IL-17a Modifier.

IL-17a is a major inflammation target, with several approved antibodies in clinical use. Small-molecule IL-17a antagonists are an emerging hot topic, with the recent advancement of three compounds into clinical trials. Here, we describe the design, discovery, synthesis, and screening of macrocyclic compounds that bind to IL-17a. We found that all currently described IL-17a modifiers belong to the same pharmacophore model, likely resulting in a similar receptor binding mode on IL-17a. A pipeline of pharmacophore analysis, virtual screening, resynthesis, and protein biophysics resulted in a potent IL-17a macrocyclic modifier.