A Phase IIIB/IV Study to Compare the Efficacy of Vancomycin Therapy to Extended Duration of Fidaxomicin Therapy in the Clinical Cure of Clostridium Difficile Infection (CDI) in an Older Population

Sustained clinical cure is defined as an assessment of clinical response at test of cure (TOC; day 12 for vancomycin and day 27 or 12 for EPFX arm) and no recurrence of CDI from TOC until time of assessment. Clinical response is determined by the investigator based on the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) criteria at TOC. Treatment response is present when either stool frequency decreases or stool consistency improves and parameters of disease severity (clinical, laboratory, radiological) improves and no new signs of severe disease develops.

Sustained clinical cure is defined as an assessment of clinical response at test of cure (TOC; day 12 for vancomycin and day 27 or 12 for EPFX arm) and no recurrence of CDI from TOC until time of assessment. Clinical response is determined by the investigator based on the ESCMID criteria at TOC. Treatment response is present when either stool frequency decreases or stool consistency improves and parameters of disease severity (clinical, laboratory, radiological) improves and no new signs of severe disease develops.

Clinical response is determined by the investigator based on the ESCMID criteria (i.e., Treatment response is present when either stool frequency decreases or stool consistency improves and parameters of disease severity [clinical, laboratory, radiological] improves and no new signs of severe disease develops. Treatment response should be daily observed and evaluated after at least three days, assuming that the patient is not worsening on treatment) at TOC.

Clinical response is determined by the investigator based on the ESCMID criteria (i.e., Treatment response is present when either stool frequency decreases or stool consistency improves and parameters of disease severity [clinical, laboratory, radiological] improves and no new signs of severe disease develops. Treatment response should be daily observed and evaluated after at least three days, assuming that the participant is not worsening on treatment) at TOC.

For participants with a recurrence after TOC, whole genome sequencing of isolates is performed on paired samples from day 1 and the day of the confirmed recurrence. Relapse is defined as paired isolates from a single recurrent participant with ≤ 2 single nucleotide variations (SNVs).

Time to resolution of diarrhea is defined as the time elapsing (in hours rounded up from minutes > 30) from the start of treatment (time of first dose of study drug) to resolution of diarrhea (time of the last unformed bowel movement [UBM] the day prior to the first of 2 consecutive days of ≤ 3 UBMs, > 50% reduction in number of stools or > 75% reduction in volume of liquid stool) that are sustained through to TOC.

For participants with clinical response at TOC, recurrence of CDI is defined as re-establishment of diarrhea after TOC to an extent (judged by the frequency of passed UBMs) that is greater than the frequency recorded on day 10 for vancomycin arm or day 25 for EPFX arm (2 days prior to TOC), confirmed by a CDI test positive for Toxin A/B and requiring further CDI therapy.

Time to recurrence of CDI is defined as the time in days from clinical response until onset of recurrence of CDI for participants who respond at TOC.

Disease-free survival is defined as the time in days a participant does not have symptoms of diarrhea from day 10 up to day 90 for participants who respond at TOC.