Synthesis of a glucosylated α-S-galactosylceramide as potential immunostimulant

Rationally Designed Highly Potent NKT Cell Agonists with Different Cytokine Selectivity through Hydrogen-Bond Interaction

Synthetic α-galactosylceramide (αGalCer) and its analogues as powerful agonists for natural killer T (NKT) cell manipulation have received significant attention in immunotherapy and adjuvant development. However, identifying new potent NKT cell agonists, especially those with Th1 selectivity that promote anticancer effects, remains a challenging task. In this work, we introduced a sulfonamide group into the acyl chain of αGalCer to form additional hydrogen bonds to intensify the glycolipid/CD1d interaction. Two compounds GCS-11 and GCS-12 demonstrated remarkable potency while exhibiting different cytokine induction patterns. Compared to αGalCer, the Th1-biased GCS-11 exhibited a 6-fold increase in IFN-γ but not IL-4, while the Th1/2-balanced GCS-12 elicited 7- and 5-fold increase in IFN-γ and IL-4, respectively, in vivo. These findings place them among the most potent NKT cell agonists, with superior antitumor effects. Therefore, hydrogen-bond-involved derivatization could be a powerful strategy to develop potent and polarized NKT cell agonists for various immunotherapies.

Electrochemical nickel-catalyzed cross-coupling of glycosyl thiols with preactivated phenols and ketones

An efficient electrochemical nickel-catalyzed cross-coupling reaction has been reported here for the synthesis of S-glycosides from preactivated phenols and ketones under mild conditions. Various glycosyl thiols, including unprotected sugar, and a diverse range of aryl/alkenyl triflates, including some complex biorelevant phenols and ketones, were well tolerated in this method.

Reverse thiophosphorylase activity of a glycoside phosphorylase in the synthesis of an unnatural Manβ1,4GlcNAc library

β-Mannosides are ubiquitous in nature, with diverse roles in many biological processes. Notably, Manβ1,4GlcNAc a constituent of the core N-glycan in eukaryotes was recently identified as an immune activator, highlighting its potential for use in immunotherapy. Despite their biological significance, the synthesis of β-mannosidic linkages remains one of the major challenges in glycoscience. Here we present a chemoenzymatic strategy that affords a series of novel unnatural Manβ1,4GlcNAc analogues using the β-1,4-d-mannosyl-N-acetyl-d-glucosamine phosphorylase, BT1033. We show that the presence of fluorine in the GlcNAc acceptor facilitates the formation of longer β-mannan-like glycans. We also pioneer a "reverse thiophosphorylase" enzymatic activity, favouring the synthesis of longer glycans by catalysing the formation of a phosphorolysis-stable thioglycoside linkage, an approach that may be generally applicable to other phosphorylases.

New syntheses of thiosaccharides utilizing substitution reactions

Novel synthetic methods published since 2005 affording carbohydrates containing sulfur atom(s) are reviewed. The review is divided to subchapters based on the position of sulfur atom(s) in the sugar molecule. Only those methods that take advantage of substitution are discussed.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Synthesis of polyfluoroalkyl sp2-iminosugar glycolipids and evaluation of their immunomodulatory properties towards anti-tumor, anti-leishmanial and anti-inflammatory therapies

Immunomodulatory glycolipids, among which α-galactosylceramide (KRN7000) is an iconic example, have shown strong therapeutic potential in a variety of conditions ranging from cancer and infection to autoimmune or neurodegenerative diseases. A main difficulty for those channels is that they often provoke a cytokine storm comprising both pro- and anti-inflammatory mediators that antagonize each other and negatively affect the immune response. The synthesis of analogues with narrower cytokine secretion-inducing capabilities is hampered by the intrinsic difficulty at controlling the stereochemical outcome in glycosidation reactions, particularly if targeting the α-anomer, which seriously hampers drug optimization strategies. Here we show that replacing the monosaccharide glycone by a sp²-iminosugar glycomimetic moiety allows accessing N-linked sp²-iminosugar glycolipids (sp²-IGLs) with total α-stereocontrol in a single step with no need of protecting groups or glycosidation promotors. The lipid tail has been then readily tailored by incorporating polyfluoroalkyl segments of varied lengths in view of favouring binding to the lipid binding site of the master p38 mitogen activated protein kinase (p38 MAPK), thereby polarizing the immune response in a cell-context dependent manner. The compounds have been evaluated for their antiproliferative, anti-leishmanial and anti-inflammatory activities in different cell assays. The size of the fluorous segment was found to be critical for the biological activity, probably by regulating the aggregation and membrane-crossing properties, whereas the hydroxylation profile (gluco or galacto-like) was less relevant. Biochemical and computational data further support a mechanism of action implying binding to the allosteric lipid binding site of p38 MAPK and subsequent activation of the noncanonical autophosphorylation route. The ensemble of results provide a proof of concept of the potential of sp²-IGLs as immunoregulators.

Novel thioglycoside analogs of α-galactosylceramide stimulate cytotoxicity and preferential Th1 cytokine production by human invariant natural killer T cells

Invariant natural killer T (iNKT) cells recognize glycolipid antigens bound to CD1d molecules on antigen-presenting cells. Therapeutic activation of iNKT cells with the xenogeneic glycolipid α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in murine models, but clinical trials using α-GalCer-stimulated human iNKT cells have shown limited efficacy. We synthesized a series of thioglycoside analogs of α-GalCer with different substituents to the galactose residue and found that two of these compounds, XZ7 and XZ11, bound to CD1d-transfected HeLa cells and activated lines of expanded human iNKT cells. Both compounds stimulated cytolytic degranulation by iNKT cells and while XZ7 preferentially stimulated the production of the antitumor cytokine interferon-γ (IFN-γ), XZ11 preferentially stimulated interleukin-4 (IL-4) production. This biased T helper type 1 effector profile of XZ7 was also evident when iNKT were stimulated with dendritic cells presenting this glycolipid. Separate analysis of the responses of CD4+, CD8α+ and CD4-CD8- iNKT cells indicated that XZ7 preferentially activated CD8α+ iNKT cells, and to a lesser degree, CD4-CD8- iNKT cells. The partial agonist effect of glycolipid XZ7, inducing cytotoxicity and IFN-γ production but not IL-4 production, indicates that specific protumour activities of iNKT cells can be abolished, while preserving their antitumor activities, by introducing structural modifications to α-GalCer. Since XZ7 was much less potent than α-GalCer as an iNKT cell agonist, it is unlikely to be superior to α-GalCer as a therapeutic agent for cancer, but may serve as a parent compound for developing more potent structural analogs.