Ridinilazole (SMT19969) is a compound that was developed as a treatment for Clostridium difficile infection, which is a spore-forming bacterial infection and the leading cause of infectious healthcare-associated diarrhea. Ridinilazole has a highly targeted spectrum of activity and can spare the normal gut microbiota. A phase I clinical trial demonstrated that oral ridinilazole is well tolerated. A phase II study showed the potential of ridinilazole in treatment of initial Clostridium difficile infection and showed that this drug can reduce recurrence of the disease. In 2019, recruitment for phase III trials was still ongoing.