Jihyeon Yoon

Free-standing two-dimensional (2D) peptoid nanosheets are promising for many aqueous applications, yet how the ionic environment governs their structure and thermal stability remains poorly understood. Here we design an ultrathin (∼2 nm) crystalline peptoid nanosheet with an extremely small ionizable (ethylammonium) polar domain as a structurally well-defined, highly charged model system, whose molecular packing is directly resolved by cryogenic electron microscopy. Solution-state differential scanning calorimetry reveals that salt-induced stabilization is dominated by entropy rather than enthalpy. Our Molecular Dynamics (MD) simulations attribute this to the release of surface-condensed counterions upon melting, which is set by both the surface’s counterion-condensing capacity and the bulk ion concentration, with our computed release entropies tracking the measured melting entropies. With sodium halide salts, the melting temperatures follow a Hofmeister-like ordering (F– > Cl– > Br–), reflecting F– ’s higher propensity for contact ion pairing with the N-terminal ammonium groups, as demonstrated by our MD simulations. Bulky organic cations such as tetrabutylammonium add enthalpic stabilization, which we ascribed to the direct dispersion contacts with hydrophobic surface groups between their alkyl chains of tetrabutylammonium and hydrophobic surface-exposed side chains, whereas Na+ does not. By resolving how ion identity partitions stabilization between entropic and enthalpic interfacial pathways, this work establishes electrolyte composition as a key design parameter for tuning free-standing, highly charged 2D soft materials.

Background: Aryl hydrocarbon receptor (AhR) is a transcription factor that is involved in the regulation of immunity. AhR inhibits T cell activation in tumors, which induces immune suppression in the blood and solid tumors. We identified effective small-molecule AhR antagonists for cancer immunotherapy. Methods: A new series of pyrazolopyrimidine derivatives was synthesized and evaluated for AhR antagonistic activity. Results: Compound 7k exhibited significant antagonistic activity against AhR in a transgenic zebrafish model. In addition, 7k exhibited good AhR antagonist activity, with a half-maximal inhibitory concentration (IC₅₀) of 13.72 nM. Compound 7k showed a good pharmacokinetic profile with an oral bioavailability of 71.0% and a reasonable half-life of 3.77 h. Compound 7k selectively exerted anti-proliferative effects on colorectal cancer cells without affecting normal cells, concurrently suppressing the expression of AhR-related genes and the PD-1/PD-L1 signaling pathway. Compound 7k exhibited potent antitumor activity in syngeneic colorectal cancer models. Importantly, the combination of anti-PD1 and compound 7k enhanced antitumor immunity by augmenting cytotoxic T lymphocyte (CTL)-mediated activity. Conclusions: Collectively, a new pyrazolopyrimidine derivative, 7k, shows promise as a potential therapeutic agent for treating colorectal cancer.

Fragment-based drug discovery (FBDD) is a powerful approach to the development of pharmaceuticals and probe molecules and there is broad interest in the development of new platforms for their discovery. Here, we introduce a workflow in which low molecular weight organic molecules displayed on the surface of TentaGel beads are exposed to a multimeric, fluorescently labeled target protein. Using tetrameric or dimeric protein targets, we show that beads that display even weak ligands (KDs in the high μM to low mM range) stably capture the protein due to avidity effects, thus allowing a simple “pull-down” protocol to be employed for fragment discovery. We also demonstrate that the platform is capable of supporting a “fragment growth” screen, which is a typical strategy to advance a fragment to a higher-affinity lead molecule. This platform is inexpensive and requires no specialized infrastructure.

Liver fibrosis is characterized by an excessive accumulation of extracellular matrix components, leading to the distortion of liver architecture and function. Recent studies have shown that antagonizing 5-hydroxytryptamine receptor 2B (5HT_2B) stimulates the apoptosis of activated hepatic stellate cells and inhibits their proliferation while concurrently regressing hepatocyte proliferation. In this study, we present compound 19c, which demonstrates promising efficacy both in vitro and in vivo. 19c showed robust in vitro activity with an IC₅₀ value of 1.09 nM and limited blood-brain barrier penetration. Furthermore, 19c did not significantly inhibit hERG and cytochrome P450 enzymes. 19c markedly reduced fibrotic deposition, with a decrease in fibrosis stage and area in the CCl₄-induced liver fibrosis mouse model. Additionally, treatment with 19c led to downregulation of key fibrosis-related genes, including α-SMA, Timp1, Col1a1, and Col3a1. Taken together, these results suggest that 19c has the potential to be a novel antifibrotic agent.

Colorectal cancer is a prevalent and prominent contributor to global cancer-related fatalities with challenges in drug resistance and metastasis. Recent research highlights the potential relationship between serotonin and cancer. 5-Hydroxytryptamine receptor 2A (HTR2A) mRNA expression in colorectal cancer cells was found to be notably elevated compared to that in normal colon cells. We therefore attempted to synthesize and evaluate HTR2A antagonists to find peripherally acting anticancer agents. Among them, 15f showed good in vitro activity (IC₅₀: 42.79 nM). 15f revealed good liver microsomal stability, without significant CYP inhibition and limited blood-brain barrier penetration. 15f also exerted selective cytotoxic effects against various colorectal cancer cells but not normal cells. 15f induced sub-G1 cell cycle arrest and apoptosis in colorectal cancer cells via the activation of p53/p21/caspase 3 signaling. In vivo treatment with 15f led to a marked delay in tumor growth in a colorectal cancer model in a dose-dependent manner.

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is currently the leading cause of chronic liver disease worldwide. Metabolic Dysfunction-Associated Steatohepatitis (MASH), an advanced form of MASLD, can progress to liver fibrosis, cirrhosis, and hepatocellular carcinoma. Based on recent findings by our team that liver 5HT_2A knockout male mice suppressed steatosis and reduced fibrosis-related gene expression, we developed a peripheral 5HT_2A antagonist, compound 11c for MASH. It shows good in vitro activity, stability, and in vivo pharmacokinetics (PK) in rats and dogs. Compound 11c also shows good in vivo efficacy in a diet-induced obesity (DIO) male mice model and in a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) male mice model, effectively improving histologic features of MASH and fibrosis. According to the tissue distribution study using [¹⁴C]-labeled 11c, the compound was determined to be a peripheral 5HT_2A antagonist. Collectively, first-in-class compound 11c shows promise as a therapeutic agent for the treatment of MASLD and MASH.

Serotonin (5-hydroxytryptophan) is a hormone that regulates emotions in the central nervous system. However, serotonin in the peripheral system is associated with obesity and fatty liver disease. Because serotonin cannot cross the blood-brain barrier (BBB), we focused on identifying new tryptophan hydroxylase type I (TPH1) inhibitors that act only in peripheral tissues for treating obesity and fatty liver disease without affecting the central nervous system. Structural optimization inspired by para-chlorophenylalanine (pCPA) resulted in the identification of a series of oxyphenylalanine and heterocyclic phenylalanine derivatives as TPH1 inhibitors. Among these compounds, compound 18i with an IC₅₀ value of 37 nM was the most active in vitro. Additionally, compound 18i showed good liver microsomal stability and did not significantly inhibit CYP and Herg. Furthermore, this TPH1 inhibitor was able to actively interact with the peripheral system without penetrating the BBB. Compound 18i and its prodrug reduced body weight gain in mammals and decreased in vivo fat accumulation.