A Study to Compare Safety and Efficacy of OPT-80(Fidaxomicin) With Vancomycin in Subjects With Clostridium Difficile-associated Diarrhea (CDAD)

This is a multicenter, double-blind, randomized, parallel group study. The subjects who meet all of the inclusion criteria and none of the exclusion criteria will be randomized, and will orally receive either OPT-80 twice daily or vancomycin powder four times daily for 10 days. A follow-up investigation will be performed 28 (±3) days after the completion of study drug administration.

Inclusion criteria

• Inpatients who have symptoms of CDAD as defined by;

• (1)Diarrhea: with ≥4 unformed bowel movements (or ≥200 mL unformed stool for subjects having rectal collection devices) and
• (2)Presence of either toxin A and/or B of C. difficile in the stool
• Subjects who have not received antibacterials (vancomycin, metronidazole, et.al.) aiming at CDAD treatment before the study

Exclusion criteria

• Life-threatening or fulminant CDAD
• Ileus paralytic or toxic megacolon
• Likelihood of death before the completion of study from any cause
• Concurrent use of oral vancomycin, metronidazole, et.al. aiming at the treatment of CDAD
• The anticipated need to continue other antibacterials for a period exceeding seven days from providing the informed consent
• Subjects who in the opinion of the investigator require other drugs to control diarrhea
• Need of change in dosage regimen of opiates during the study period
• Need of change in dosage regimen of probiotic products during the study period
• History/complications of ulcerative colitis or Crohn's disease
• Multiple occurrences of CDAD within the past three months
• Hypersensitivity to vancomycin
• Previous exposure to OPT-80 (fidaxomicin)
• Female patients who are pregnant, breastfeeding or possibly pregnant, or wishing to become pregnant during the course of study
• Participation in other clinical research studies or Post Marketing Clinical Trials utilizing an investigational agent within one month prior to providing the informed consent or within five half-lives of the investigational agent, whichever is longer