Hit-to-lead development and in vivo potency analysis of an antivirulence agent targeting HilD, the central regulator of Salmonella pathogenicity

01/11/2023 to 30/04/2024

The worldwide rise of antibiotic-resistant bacteria represents a serious threat for human and animal health. Investigations of novel antibiotics are increasingly oriented towards nontraditional antimicrobials like antivirulence agents which are molecules blocking virulence mechanisms of bacteria without affecting their cell viability. Such a targeted approach is thought to limit or prevent the selection of resistant mutants in vivo and spare the non-pathogenic bacteria of the microbiota. We successfully identified a small molecule as a potential treatment against infections caused by non-typhoidal Salmonella (NTS), a major food-borne enteric pathogen characterized by an incidence of 150 million cases per year and a mortality of 120,000 driven mainly by invasive NTS infection (iNTS). The identified compound C26 specifically targets HilD, the central regulator of Salmonella invasion genes. Inhibition of HilD reduces both bacterial adhesion to and invasion into host cells. As HilD-deficient Salmonella are avirulent, HilD inhibition is a promising approach for prevention and treatment of non-typhoidal Salmonella infections. A first round of optimization by designing and testing 134 analogues resulted in compounds with an IC50 lower than 5 μM. In order to develop our HilD-inhibitors into a lead structure and provide an in vivo proof of efficacy, we propose to carry on our efforts with an extended structure-activity-relationship (SAR), a multi-variable optimization, pharmacological characterization, and test efficacy of the nominated lead compound in a mouse model of Salmonella gastrointestinal infection.