# Anti-Biofilm Agents to Overcome _Pseudomonas aeruginosa Antibiotic Resistance_
## 3 Anti-Biofilm Agents to Tackle _P. aeruginosa_
### Analogs of Native Autoinducers
#### 3.1.3. Lectin Inhibitors  
The soluble lectins LecA and LecB are present on the outer membrane of the bacteria to enable adherence to host tissues, a critical step in the infection initiation process. They also ensure the intercellular adhesion inside the biofilms and strengthen their building. Therefore, lectins have triggered the interest of medicinal chemists as new therapeutic targets against _P. aeruginosa_ infections. These ABAs inhibit LecA and LecB fixation to D-galactose or L-fucose monosaccharides. By analogy, the structure of the inactivating ligands is based on the same patterns [37]. One major drawback for the conception of the first monovalent lectin inhibitors is the weakness of the lectin/ligand bond. On the contrary, it has been revealed that the binding of multivalent carbohydrate derivatives to lectins induces a cluster effect that strongly inactivates the protein. [PERSON] et al. designed a series of synthetic multivalent fucose-based ligands with a high affinity for LecB [83]. These glycodendrimers were assembled on a peptide backbone using solid-phase synthesis methods, which allowed amino acid modulations to reach greater specificity or refine their physicochemical properties. Of the two peptide dendrimers' developed libraries, nine compounds inhibited LecB in an enzyme-linked lectin assay (ELLA) (IC\({}_{50}\) = 0.11 to 0.75 \(\upmu\)M) with a 100-fold activity increase compared to L-fucose (IC\({}_{50}\) = 11 \(\upmu\)M). Remarkably, the compound **FD2 (ABA-35)** was able to completely inhibit biofilm formation at 50 \(\upmu\)M (Figure 12). At this concentration,  
Figure 11: Key interactions with the target, anti-QS and anti-biofilm activities of **M64** and **D88** as biaromatic PqsR inhibitors [79; 80; 81]. **FD2** also induced a complete elimination of mature biofilms established on an abiotic surface, including those of three cystic fibrosis-derived clinical strains. This makes it a very interesting agent for the treatment of _P. aeruginosa_ biofilm-related infections. A model of the **FD2**-LecB complex showed that the molecule was in fact too small to be multivalent and to interact with two binding sites. However, the compound forms H-bonds and hydrophobic interactions with residues outside the binding sites, which explains its strong affinity for LecB. [PERSON] et al. applied the same strategy to the design of multivalent ligands targeting the galactose-specific lectin LecA [84]. The peptide dendrimer portion of **FD2** was thus attached to a carboxyphenyl \(\beta\)-galactosidase moiety to obtain the derivative **GalAG2** (**ABA-36**), which shows an 875-fold increase in binding to LecA compared to D-galactose. **GalAG2** inhibits 60% of biofilm formation at 20 uM. Interestingly, its monovalent analogs were revealed to be inactive, demonstrating that multivalency was crucial to anti-biofilm efficacy. [PERSON] et al. also developed the tetravalent anti-biofilm compound **ABA-37** to target LecA [85]. In this molecule, a flexible PEG spacer allows the cross-linking between two central phenyl groups. **ABA-37** inhibits 46% of biofilm formation at 28 uM. At the same concentration, the molecule also successfully induces a 50% dispersion of a preformed biofilm. Thus, this kind of structure is likely to be interesting for the development of new anti-biofilm agents. Still, optimization is required to improve their binding affinity to lectins. However, these large multivalent dendrimers possess a high molecular weight. In order to avoid undesirable cross-links inside the biofilm and to enhance their chances to reach a drug-like molecule, [PERSON] et al. decided to focus on monovalent low molecular weight inhibitors of LecB and developed aryl-sulfonamide glycolimetics [86]. The best anti-biofilm results were obtained with the two compounds **ABA-38** and **ABA-39**, which inhibited 80-90% of biofilm formation at 100 uM. Moreover, both molecules showed a good affinity towards LecB, with IC\({}_{50}\) of 0.34 and 0.44 uM for **ABA-38** and **ABA-39**, respectively.