# Anti-Biofilm Agents to Overcome _Pseudomonas aeruginosa Antibiotic Resistance_
## 3 Anti-Biofilm Agents to Tackle _P. aeruginosa_
### Analogs of Native Autoinducers
designed other halogenated furanone derivatives, leading to the discovery of **ABA-25**, which inhibits 31% of biofilm formation at 74 \(\upmu\)M [71]. This hit compound displays low eukaryotic cytotoxicity and interesting ADME properties. It is noteworthy that several other furanone analogs have been described as QSIs. Although lacking significant anti-biofilm activity, they possess very promising anti-virulence properties resulting from their good affinity towards LasR. Finally, the quinoline and flavonoid natural scaffolds have also triggered interest due to their antimicrobial properties, which led to many derivatives potentially able to interfere with AHL-associated communication systems. However, high concentrations of these compounds were necessary to successfully inhibit QS. Yet, [PERSON] et al. described the screening of a flavonoid library that enabled the discovery of LasR inhibitor **ABA-26** via a reporter gene assay [72]. This product reduces biofilm formation by 45% at 50 \(\upmu\)M, with very low cytotoxicity towards various human cell lines. A molecular docking study of **ABA-26** revealed hydrophobic interactions between the flavonoid core and the residues Leu125 and Gly123 as well as H-bonds between its carbonyl group and Asp43 and Ser44 (NH). Furthermore, the study highlighted the importance of the phosphoramidate function as it could induce a conformational change of Tyr47 next to the LasR autoinduction site, thus destabilizing the activated transcription factor and inducing the dissociation of LasR from DNA. Indeed, **ABA-26** does not seem to compete with the native ligand in the autoinduction domain, which could be in favor of an allosteric inhibitory mechanism. Although quinoline derivatives are known for their anti-virulence activity as AQ autoinducer analogs, the compounds developed by [PERSON] et al. showed a specificity towards RhIR [73]. The fluorine-substituted phenyl group of **ABA-27** and the alkyl chain of its substituent in position 8 of the quinoline proved to be essential for anti-biofilm activity. In particular, the latter is known for the establishment of van der Waals interactions in the hydrophobic pockets of the BHL receptor. **ABA-27** inhibited 25% of biofilm formation at 10 \(\upmu\)M and reduced 25% of rhamn production. Other QSIs were discovered via the study of relevant antimicrobial scaffolds or by exploring the anti-virulence potential of antimicrobial drugs. Several polyaromatic QSIs targeting LasR were therefore discovered. First, [PERSON] et al. studied the anti-virulence activity of the beta-lactamase inhibitor **SM-23 (ABA-28)** (Figure 10) [74]. This boric acid derivative was able to inhibit odDHL and BHL secretion by 77 and 31%, respectively, as well as some virulence factors such as pyoverdine, elastase and pyocyanin. **SM-23** decreased 50% of both biofilm formation and maturation at a concentration as low as 1.6 \(\upmu\)M. Interestingly, **SM-23** also successfully reduced the establishment of biofilm onto endotracheal tubes in an in vitro model mimicking clinical settings. Nonetheless, this LasR inhibitor was not described further since this study was conducted in 2020. Some  
Figure 9: Key interactions with the target, anti-QS and anti-biofilm activities of QSIs inspired from natural compounds targeting LasR or RhIR [66; 67; 68; 69; 70; 71; 72; 73]. QSIs have been brought out by rational design based on the literature data. For instance, [PERSON] et al. reported in 2022 novel troponyl-sulfone derivatives inspired by (i) natural troponoid antimicrobial products such as thuyaplicin associated with (ii) the sulfone of the beta-lactamase inhibitor sulfabactam [75]. Therefore, the compound **ABA-29** exhibited potent anti-LasR and anti-LasI properties (almost 100% inhibition at 20 uM), which are correlated with interesting anti-biofilm activity (54% inhibition of biofilm formation at 40 uM). No eukaryotic cytotoxicity was detected. A treatment with **ABA-29** on an epithelial kidney cell line infected with _P.