Old Sources for New Antimicrobial Drugs: Lessons and Opportunities
Abstract: The decline of the output of the R&D programs of the pharmaceutical companies may have begun to turn around when compared to earlier years of the 21st century. Although one of the responsible for this increase is the immunopharmacology-based treatments, small molecules still play an important role. An unmet medical need should prioritize drug resistance that has reached critical levels, posing a public health challenge with extensive health, economic, and societal implications. Medicinal chemistry approaches to find novel antimicrobial compounds, which show the desired pharmacological activity continue to rely on natural products, synthesis, and existing drugs as sources. In this communication, examples of antimicrobial small molecules obtained in our research group that arise from both natural and synthetic models will be given. Lessons and opportunities in starting from privileged structures, drug repurposing, active metabolites, synthetic intermediates, or natural products as potential sources of new drugs will be highlighted. To disclose their antimicrobial effects, in silico and HTS screening approaches were employed. An example of an integrative approach concerns the discovery of thioxanthones as a promising class of efflux pump inhibitors. The case studies presented herein are expected to contribute to a multidisciplinary vision in drug discovery, with the involvement of several sources. To us, small molecules will continue to provide a fruitful solution in drug discovery and development.