Projects

• Synthesis of inhibitors of DC-SIGN receptor
• Preparation of nanoparticles with DC-SIGN-targeting ligands
• Synthesis of ligands for ASGPR receptor and their use in the treatment of hepatitis B
• Synthesis of ligands for G-quadruplex visualization
• Synthesis of agonists of muscarine receptor

Synthesis of inhibitors of DC-SIGN receptor

DC-SIGN is a C-type lectin receptor present on the surface of dendritic cells and macrophages. It binds to carbohydrate structures found on the surface of numerous pathogens: viruses (HIV, ebola, cytomegalovirus), bacteria (M. tuberculosis, S. pneumoniae), fungi (C. albicans), and parasites (Leishmana). The surface of these pathogens is typically rich in mannose and fucose which are natural DC-SIGN ligands. Upon binding, DC-SIGN can mediate the uptake of the pathogen into the dendritic cell and launch an immune response. Hence, DC-SIGN inhibitors could act as anti-infective agents.

 The primary carbohydrate binding site of DC-SIGN is rather shallow and hydrophobic and as such is not a good target for medicinal chemistry. Recent studies have shown that apart from the primary carbohydrate binding site, DC-SIGN harbours five secondary binding sites available to accommodate small drug-like molecules (Figure 1).

Figure 1. DC-SIGN receptor, primary carbohydrate binding site (yellow) and secondary binding sites I–V. Picture taken from Aretz, J. et al.: Angew. Chem. Int. Ed. 2017, 56, 7292–7296.

In this project, we synthesize substituted mannosides and fucosides which can interact with both, the primary and secondary binding site (Figure 2a). In parallel, we synthesize non-carbohydrate ligands which interact with the secondary binding sites and upon binding modulate the interaction of carbohydrates with the primary carbohydrate binding site (Figure 2b). To synthesize these compounds, we use an approach called fragment-based drug discovery.

Figure 2. Overview of the synthesized DC-SIGN ligands. a) DC-SIGN inhibitors based on D-mannose and l-fucose; b) non-carbohydrate inhibitors binding to the secondary binding sites.

Preparation of nanoparticles with DC-SIGN-targeting ligands

We use the synthesized DC-SIGN ligands to modify the surface of nanoparticles, in particular fluorescent nanodiamonds and liposomes (Figure 3). Fluorescent nanodiamonds can be used for the visualization of metastases in sentinel lymphatic nodes. Tumour-associated macrophages (TAMs) gather in the vicinity of metatases. Upon binding of the fluorescent nanodiamonds modified with DC-SIGN ligand to TAMs, the nanoparticles are internalized and their fluorescence properties enable the visualisation of the macrophages and thus indirectly of the metastases.

 Liposomes modified with DC-SIGN ligands can be used for targeted delivery of therapeutic compounds to dendritic cells.

Figure 3. Nanoparticles modified with DC-SIGN ligands. a) Fluorescent nanodiamonds for the visualization of metastases; b) liposomes for targeted delivery of therapeutic compounds into dendritic cells.

Synthesis of ligands for ASGPR receptor and their use in the treatment of hepatitis B

ASGPR is a C-type lectin receptor which specifically recognizes ligands with terminal galactose or N-acetylgalactosamine. It is found almost exclusively on hepatocytes and is already clinically used for ASGPR-targeted drug delivery to the liver. Our aim is to prepare lipid nanoparticles modified with selective ASGPR ligands (Figure 4) and use these nanoparticles to transport CRISPR/Cas9 system into the liver. Several studies have already confirmed the application of CRISPR/Cas9 as a feasible approach to eradicate the hepatitis B virus DNA and thus help treat hepatitis B.

Figure 4. Lipid nanoparticles modified with ASGPR ligands.

Synthesis of ligands for G-quadruplex visualization

In collaboration with ICMUB CNRS Dijon, France, we synthesize ligands for the visualization of G-quadruplexes. Our aim is to prepare twice-as-smart fluorescent probes that act both as a smart quadruplex ligand (i.e., that assembles only in the presence of its native G-quadruplex target) and a smart fluorescent probe (i.e., the fluorescence of which is turned on only upon interaction with its target). A similar compound, N-TASQ, allowed for the very first visualization of G-quadruplexes in living human cells and since then has been used in oncology and neurology.

Figure 5. Twice-as-smart probes for the visualization of G-quadruplex. Picture taken from Laguerre, A. et al.: J. Am. Chem. Soc. 2015, 137, 8521–8525.

Synthesis of agonists of muscarine receptor

In collaboration with the group of neurochemistry from the Institute of Physiology CAS, we have just started working on the synthesis of agonists of muscarine receptors based on tetrahydropyridine. These compounds are promising agents for the treatment of neuropathies.