In Vitro and In Vivo Activity of Peptidomimetic Compounds That Target the Periodontal Pathogen Porphyromonas gingivalis

The interaction of the periodontal pathogen Porphyromonas gingivalis with oral streptococci is important for initial colonization of the oral cavity by P. gingivalis and is mediated by a discrete motif of the streptococcal antigen I/II protein. A synthetic peptide encompassing this motif functions as a potent inhibitor of P. gingivalis adherence, but the use of peptides as topically applied therapeutic agents in the oral cavity has limitations arising from the relatively high cost of peptide synthesis and their susceptibility to degradation by proteases expressed by oral organisms. In this study, we demonstrate the in vitro and in vivo activity of five small-molecule mimetic compounds of the streptococcal peptide. Using a three-species biofilm model, all five compounds were shown to effectively inhibit the incorporation of P. gingivalis into in vitro biofilms and exhibited 50% inhibitory concentrations (IC(50)s) of 10 to 20 μM. Four of the five compounds also significantly reduced maxillary alveolar bone resorption induced by P. gingivalis infection in a mouse model of periodontitis. All of the compounds were nontoxic toward a human telomerase immortalized gingival keratinocyte cell line. Three compounds exhibited slight toxicity against the murine macrophage J774A.1 cell line at the highest concentration tested. Compound PCP-III-201 was nontoxic to both cell lines and the most potent inhibitor of P. gingivalis virulence and thus may represent a novel potential therapeutic agent that targets P. gingivalis by preventing its colonization of the oral cavity.