Prevention of Recurrent C. Difficile Infection Study With AZD5148 Monoclonal Antibody

Approximately 230 participants will be enrolled and randomized 1:1 to receive a single dose of either AZD5148 or placebo (normal saline). Route of administration (intramuscular or intravenous push) will be according to the Investigator's choice. Stratification will be based on geographical region.

Study details include:

• Up to 2 site visits for confirmation of eligibility and dose administration, including stool sample collection;
• Up to 7 planned visits;
• Contacts initiated by site staff -weekly, later monthly follow up;
• Electronic diary completion.

Participants will receive a single dose A of AZD5148 administered via either intramuscular injection or intravenous push.

Drug: AZD5148

Participants will receive a single dose of placebo via intramuscular or intravenous push.

Other: Placebo

Participants will receive a single dose A of AZD5148 administered via either intramuscular injection or intravenous push.

Participants will receive a single dose of placebo (0.9% (w/v) sodium chloride for injection) administered via either intramuscular injection or intravenous push.

Plazo: Day 1 through day 91

Recurrence of C difficile infection (rCDI) occurring after initial clinical cure (ICC) of the qualifying C difficile infection (CDI). CDI is defined as a history of diarrhea (\>=3 unformed stools, ie, type 6 or 7 stool on Bristol Stool Scale in \<=24 hours for 2 consecutive calendar days) accompanied by a positive stool test for C difficile toxin.

Plazo: Day 91

Sustained clinical cure is defined as achieving ICC of the qualifying CDI and not having an rCDI event through Day 91. ICC is defined as clinical cure for the qualifying CDI episode with a duration of a minimum of 10 days and a maximum of 28 days of antibacterial drug therapy for CDI.

Plazo: Day 1 through Day 91

Duration of the first occurrence of confirmed rCDI is calculated from the first day of diarrhea meeting the clinical symptom criteria until the date of clinical cure. Clinical cure is defined as \<=2 unformed stools (ie, type 6 or 7 stool on Bristol Stool Scale) in 24 hours for 2 consecutive calendar days after the end of antibacterial drug treatment for the CDI episode.

Plazo: Day 1 through Day 91

Severe rCDI is defined as an rCDI event characterized by either: peripheral blood leukocytosis with leukocyte count \>15,000 cells/uL or serum creatinine level \>1.5 mg/dL.

Plazo: Day 1 through Day 91

Fulminant rCDI is defined as a severe rCDI event with hypotension or shock, toxic megacolon, or ileus.

Plazo: Day 1 through Day 91

As reported by patient reported outcome (PRO) instrument for first occurrence of rCDI.

Plazo: Day 1 through Day 91

As reported by patient reported outcome (PRO) instrument for first occurrence of rCDI.

Plazo: Day 1 through Day 91

Hospitalization due to rCDI is defined as a confirmed rCDI event and a hospitalization related to the rCDI event.

Plazo: Day 1 though Day 91

The sum of all hospitalization durations related to the first recurrent CDI that leads to hospitalization.

Plazo: Day 1 through Day 91

rCDI related mortality is defined as a death related to rCDI as assessed by the Investigator.

Plazo: 1 hour post-IMP administration

Adverse events with a start time within 1 hour post-IMP administration

Plazo: 24 hours post-IMP administration

Injection or infusion-related reactions with a start date and time within 24 hours of IMP administration.

Plazo: Day 1 through Day 8

Local reactions at the injection or infusion site with a start date through Day 8 post-IMP administration.

Plazo: ICF date through Day 361

SAEs are adverse events that fulfill any of the SAE criteria and are recorded with a start date from the date of informed consent form signature until the end of the study follow-up (Day 361)

Plazo: Day 1 through Day 361

MAAEs are adverse events leading to medically attended visits that were not routine visits, such as ER visit, or an otherwise unscheduled visit to or from medical personnel (medical doctor) for any reason.

Plazo: Day 1 through Day 361

AESIs as defined by Clinical Study Protocol.

Plazo: Day 1 through Day 361

Related AEs are adverse events assessed as related to IMP by the Investigator.

Plazo: Day 1 through Day 91

AEs are defined as any unfavourable medical occurrence in a participant administered the IMP, regardless of the causal relationship to IMP.

Plazo: Day 1 through Day 361

PK will be characterized through AZD5148 serum concentrations over time in participants who receive AZD5148.

Plazo: Day 1 through Day 361

Immunogenicity is evaluated through AZD5148 anti-drug antibody responses over time in serum from participants who receive AZD5148.

A Phase IIb, Randomized, Double-blind, Placebo-controlled Study to Evaluate the Efficacy and Safety of AZD5148 for Prevention of Recurrence of Clostridioides Difficile Infection in Individuals 18 Years of Age and Above