Pharmacological, Physiochemical, and Drug-Relevant Biological Properties of Short Chain Fatty Acid Hexosamine Analogues Used in Metabolic Glycoengineering

Discovery and optimization of 3-(indolin-5-yloxy)pyridin-2-amine derivatives as potent necroptosis inhibitors

Necroptosis is a form of regulated necrotic cell death and has been confirmed to play pivotal roles in the pathogenesis of multiple autoimmune diseases such as rheumatoid arthritis (RA) and psoriasis. The development of necroptosis inhibitors may offer a promising therapeutic strategy for the treatment of these autoimmune diseases. Herein, starting from the in-house hit compound 1, we systematically performed structural optimization to discover potent necroptosis inhibitors with good pharmacokinetic profiles. The resulting compound 33 was a potent necroptosis inhibitor for both human I2.1 cells (IC50 < 0.2 nM) and murine Hepa1-6 cells (IC50 < 5 nM). Further target identification revealed that compound 33 was an inhibitor of receptor interacting protein kinase 1 (RIPK1) with favorable selectivity. In addition, compound 33 also exhibited favorable pharmacokinetic profiles (T1/2 = 1.32 h, AUC = 1157 ng·h/mL) in Sprague-Dawley rats. Molecular docking and molecular dynamics simulations confirmed that compound 33 could bind to RIPK1 with high affinity. In silico ADMET analysis demonstrated that compound 33 possesses good drug-likeness profiles. Collectively, compound 33 is a promising candidate for antinecroptotic drug discovery.

Anticancer Properties of Hexosamine Analogs Designed to Attenuate Metabolic Flux through the Hexosamine Biosynthetic Pathway

Altered cellular metabolism is a hallmark of cancer pathogenesis and progression; for example, a near-universal feature of cancer is increased metabolic flux through the hexosamine biosynthetic pathway (HBP). This pathway produces uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), a potent oncometabolite that drives multiple facets of cancer progression. In this study, we synthesized and evaluated peracetylated hexosamine analogs designed to reduce flux through the HBP. By screening a panel of analogs in pancreatic cancer and glioblastoma multiform (GBM) cells, we identified Ac₄Glc2Bz─a benzyl-modified GlcNAc mimetic─as an antiproliferative cancer drug candidate that down-regulated oncogenic metabolites and reduced GBM cell motility at concentrations non-toxic to non-neoplastic cells. More specifically, the growth inhibitory effects of Ac₄Glc2Bz were linked to reduced levels of UDP-GlcNAc and concomitant decreases in protein O-GlcNAc modification in both pancreatic cancer and GBM cells. Targeted metabolomics analysis in GBM cells showed that Ac₄Glc2Bz disturbed glucose metabolism, amino acid pools, and nucleotide precursor biosynthesis, consistent with reduced proliferation and other anti-oncogenic properties of this analog. Furthermore, Ac₄Glc2Bz reduced the invasion, migration, and stemness of GBM cells. Importantly, normal metabolic functions mediated by UDP-GlcNAc were not disrupted in non-neoplastic cells, including maintenance of endogenous levels of O-GlcNAcylation with no global disruption of N-glycan production. Finally, a pilot in vivo study showed that a potential therapeutic window exists where animals tolerated 5- to 10-fold higher levels of Ac₄Glc2Bz than projected for in vivo efficacy. Together, these results establish GlcNAc analogs targeting the HBP through salvage mechanisms as a new therapeutic approach to safely normalize an important facet of aberrant glucose metabolism associated with cancer.

Glycoengineering human neural stem cells (hNSCs) for adhesion improvement using a novel thiol-modified N-acetylmannosamine (ManNAc) analog

This study sets the stage for the therapeutic use of Ac₅ManNTProp, an N-acetylmannosamine (ManNAc) analog that installs thiol-modified sialoglycans onto the surfaces of human neural stem cells (hNSC). First, we compared hNSC adhesion to the extracellular matrix (ECM) proteins laminin, fibronectin, and collagen and found preferential adhesion and concomitant changes to cell morphology and cell spreading for Ac₅ManNTProp-treated cells to laminin, compared to fibronectin where there was a modest response, and collagen where there was no observable increase. PCR array transcript analysis identified several classes of cell adhesion molecules that responded to combined Ac₅ManNTProp treatment and hNSC adhesion to laminin. Of these, we focused on integrin α6β1 expression, which was most strongly upregulated in analog-treated cells incubated on laminin. We also characterized downstream responses including vinculin display as well as the phosphorylation of focal adhesion kinase (FAK) and extracellular signal-related kinase (ERK). In these experiments, Ac₅ManNTProp more strongly induced all tested biological endpoints compared to Ac₅ManNTGc, showing that the single methylene unit that structurally separates the two analogs finely tunes biological responses. Together, the concerted modulation of multiple pro-regenerative activities through Ac₅ManNTProp treatment, in concert with crosstalk with ECM components, lays a foundation for using our metabolic glycoengineering approach to treat neurological disorders by favorably modulating endpoints that contribute to the viability of transplanted NSCs.

The effect of deoxyfluorination and O-acylation on the cytotoxicity of N-acetyl-D-gluco- and D-galactosamine hemiacetals

Fully acetylated deoxyfluorinated hexosamine analogues and non-fluorinated 3,4,6-tri-O-acylated N-acetyl-hexosamine hemiacetals have previously been shown to display moderate anti-proliferative activity. We prepared a set of deoxyfluorinated GlcNAc and GalNAc hemiacetals that comprised both features: O-acylation at the non-anomeric positions with an acetyl, propionyl and butanoyl group, and deoxyfluorination at selected positions. Determination of the in vitro cytotoxicity towards the MDA-MB-231 breast cancer and HEK-293 cell lines showed that deoxyfluorination enhanced cytotoxicity in most analogues. Increasing the ester alkyl chain length had a variable effect on the cytotoxicity of fluoro analogues, which contrasted with non-fluorinated hemiacetals where butanoyl derivatives had always higher cytotoxicity than acetates. Reaction with 2-phenylethanethiol indicated that the recently described S-glyco-modification is an unlikely cause of cytotoxicity.

Weak Microbial Metabolites: a Treasure Trove for Using Biomimicry to Discover and Optimize Drugs

For decades, traditional drug discovery has used natural product and synthetic chemistry approaches to generate libraries of compounds, with some ending as promising drug candidates. A complementary approach has been to adopt the concept of biomimicry of natural products and metabolites so as to improve multiple drug-like features of the parent molecule. In this effort, promiscuous and weak interactions between ligands and receptors are often ignored in a drug discovery process. In this Emerging Concepts article, we highlight microbial metabolite mimicry, whereby parent metabolites have weak interactions with their receptors that then have led to discrete examples of more potent and effective drug-like molecules. We show specific examples of parent-metabolite mimics with potent effects in vitro and in vivo. Furthermore, we show examples of emerging microbial ligand-receptor interactions and provide a context in which these ligands could be improved as potential drugs. A balanced conceptual advance is provided in which we also acknowledge potential pitfalls-hyperstimulation of finely balanced receptor-ligand interactions could also be detrimental. However, with balance, we provide examples of where this emerging concept needs to be tested. SIGNIFICANCE STATEMENT: Microbial metabolite mimicry is a novel way to expand on the chemical repertoire of future drugs. The emerging concept is now explained using specific examples of the discovery of therapeutic leads from microbial metabolites.

Exploiting metabolic glycoengineering to advance healthcare

Metabolic glycoengineering (MGE) is a technique for manipulating cellular metabolism to modulate glycosylation. MGE is used to increase the levels of natural glycans and, more importantly, to install non-natural monosaccharides into glycoconjugates. In this Review, we summarize the chemistry underlying MGE that has been developed over the past three decades and highlight several recent advances that have set the stage for clinical translation. In anticipation of near-term application to human healthcare, we describe emerging efforts to deploy MGE in diverse applications, ranging from the glycoengineering of biotherapeutic proteins and the diagnosis and treatment of complex diseases such as cancer to the development of new immunotherapies.

Next-generation unnatural monosaccharides reveal that ESRRB O-GlcNAcylation regulates pluripotency of mouse embryonic stem cells

Unnatural monosaccharides such as azidosugars that can be metabolically incorporated into cellular glycans are currently used as a major tool for glycan imaging and glycoproteomic profiling. As a common practice to enhance membrane permeability and cellular uptake, the unnatural sugars are per-O-acetylated, which, however, can induce a long-overlooked side reaction, non-enzymatic S-glycosylation. Herein, we develop 1,3-di-esterified N-azidoacetylgalactosamine (GalNAz) as next-generation chemical reporters for metabolic glycan labeling. Both 1,3-di-O-acetylated GalNAz (1,3-Ac₂GalNAz) and 1,3-di-O-propionylated GalNAz (1,3-Pr₂GalNAz) exhibit high efficiency for labeling protein O-GlcNAcylation with no artificial S-glycosylation. Applying 1,3-Pr₂GalNAz in mouse embryonic stem cells (mESCs), we identify ESRRB, a critical transcription factor for pluripotency, as an O-GlcNAcylated protein. We show that ESRRB O-GlcNAcylation is important for mESC self-renewal and pluripotency. Mechanistically, ESRRB is O-GlcNAcylated by O-GlcNAc transferase at serine 25, which stabilizes ESRRB, promotes its transcription activity and facilitates its interactions with two master pluripotency regulators, OCT4 and NANOG.

Per-O-acetylated unnatural monosaccharides are popular tools for glycan labeling in live cells but can undergo unwanted side reactions with cysteines. Here, the authors develop unnatural sugars in a partially esterified form that are inert towards cysteines, and use them to probe O-GlcNAcylation in mESCs.

Improving Immunotherapy Through Glycodesign

Immunotherapy is revolutionizing health care, with the majority of high impact "drugs" approved in the past decade falling into this category of therapy. Despite considerable success, glycosylation-a key design parameter that ensures safety, optimizes biological response, and influences the pharmacokinetic properties of an immunotherapeutic-has slowed the development of this class of drugs in the past and remains challenging at present. This article describes how optimizing glycosylation through a variety of glycoengineering strategies provides enticing opportunities to not only avoid past pitfalls, but also to substantially improve immunotherapies including antibodies and recombinant proteins, and cell-based therapies. We cover design principles important for early stage pre-clinical development and also discuss how various glycoengineering strategies can augment the biomanufacturing process to ensure the overall effectiveness of immunotherapeutics.

Integration of genetic and metabolic features related to sialic acid metabolism distinguishes human breast cell subtypes

In this report we use 'high-flux' tributanoyl-modified N-acetylmannosamine (ManNAc) analogs with natural N-acetyl as well as non-natural azido- and alkyne N-acyl groups (specifically, 1,3,4-O-Bu3ManNAc, 1,3,4-O-Bu3ManNAz, and 1,3,4-O-Bu3ManNAl respectively) to probe intracellular sialic acid metabolism in the near-normal MCF10A human breast cell line in comparison with earlier stage T-47D and more advanced stage MDA-MB-231 breast cancer lines. An integrated view of sialic acid metabolism was gained by measuring intracellular sialic acid production in tandem with transcriptional profiling of genes linked to sialic acid metabolism. The transcriptional profiling showed several differences between the three lines in the absence of ManNAc analog supplementation that helps explain the different sialoglycan profiles naturally associated with cancer. Only minor changes in mRNA transcript levels occurred upon exposure to the compounds confirming that metabolic flux alone can be a key determinant of sialoglycoconjugate display in breast cancer cells; this result complements the well-established role of genetic control (e.g., the transcription of STs) of sialylation abnormalities ubiquitously associated with cancer. A notable result was that the different cell lines produced significantly different levels of sialic acid upon exogenous ManNAc supplementation, indicating that feedback inhibition of UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE)-generally regarded as the 'gatekeeper' enzyme for titering flux into sialic acid biosynthesis-is not the only regulatory mechanism that limits production of this sugar. A notable aspect of our metabolic glycoengineering approach is its ability to discriminate cell subtype based on intracellular metabolism by illuminating otherwise hidden cell type-specific features. We believe that this strategy combined with multi-dimensional analysis of sialic acid metabolism will ultimately provide novel insights into breast cancer subtypes and provide a foundation for new methods of diagnosis.