<i>Clostridium difficile</i> Drug Pipeline: Challenges in Discovery and Development of New Agents

In the past decade <i>Clostridium difficile</i> has become a bacterial pathogen of global significance. Epidemic strains have spread throughout hospitals, while community acquired infections and other sources ensure a constant inoculation of spores into hospitals. In response to the increasing medical burden, a new <i>C. difficile</i> antibiotic, fidaxomicin, was approved in 2011 for the treatment of <i>C. difficile</i>-associated diarrhea. Rudimentary fecal transplants are also being trialed as effective treatments. Despite these advances, therapies that are more effective against <i>C. difficile</i> spores and less damaging to the resident gastrointestinal microbiome and that reduce recurrent disease are still desperately needed. However, bringing a new treatment for <i>C. difficile</i> infection to market involves particular challenges. This review covers the current drug discovery pipeline, including both small molecule and biologic therapies, and highlights the challenges associated with in vitro and in vivo models of <i>C. difficile</i> infection for drug screening and lead optimization