Travelers' Diarrhea Clinical Trial
Official title:
Dose-Finding Study of WS6788A and LSN03-016011/A Enterotoxigenic E. Coli (ETEC) Challenge Strains That Express CS17
This will be a strain and dose-finding study in which LSN03-016011/A ETEC will be administered at a starting inoculum of 5x108 cfu to 5 subjects to establish a human disease model. If 80% attack rate (AR) is achieved without high output diarrhea, the same inoculum will be given to 10 more subjects for confirmation of AR. If 80% AR is not achieved, attack rate and severity of disease will be evaluated to determine if the dose should be increased. The same sequence may be conducted with WS6788A if applicable. If the LSN strain causes high output diarrhea the dose will be adjusted down and further dose characterization continued. An iterative process will be used to select the optimal strain and dose with each step reviewed and approved by the medical monitor.
This is a phase 1, open-label, strain and dose-finding study designed to establish a human
challenge model for CS17+ ETEC that causes > 80% attack rate without causing high output
diarrhea. Based on the strain histories, testing will commence using LSN03-016011/A. This
strain was isolated from a naïve adult U.S. citizen living in Turkey with a typical clinical
presentation for ETEC diarrheal disease and no bacterial co-pathogens isolated from the
stool. The host is representative of the study population for this study and for future
efficacy studies with anti-CS17+ ETEC vaccines. As shown in the figure below, 5x108 cfu of
ETEC strain (LSN03-016011/A) will initially be administered to 5 subjects. If an attack rate
of >80% (at least 4/5 subjects) occurs with no high output diarrhea, results will be
confirmed in an additional 10 subjects. Additionally, an inoculum at least ½ log lower
(1x108) (depending on the severity of illness documented) may be administered to 10 subjects
to characterize the dose-response relationship. If the 5x108 cfu inoculum does cause high
output diarrhea, then the inoculum will be reduced appropriatelyIf the 5x108 cfu of
LSN03-016011/A does not cause a > 80% attack rate, the next step will depend on the observed
attack rate and severity of illness. A low attack rate with mild disease would prompt a
change to the alternate strain (WS7688A) for testing, using the same pathway used with the
LSN strain . An attack rate < 80% with most diarrhea classified as at least moderate
diarrhea would prompt an upward adjustment of the LSN inoculum appropriate to the findings.
The decision to move up or down in inoculum or to change CS17 + strains will only occur with
the concurrence of the medical monitor. Following each step in the strain and dose finding
iterations, a report summarizing the results of that step, and detailing the planned next
step will be signed by the principal investigator and the medical monitor. The maximum dose
of either strain is 1 X 109. The anticipated maximum number of subjects planned for this
study is 25.
Subjects will be admitted to the inpatient facility on study day -1. On study day 0,
subjects will have their morning meal, fast for 90 minutes, and then be given 120mL of
sodium bicarbonate buffer to neutralize stomach acidity. Approximately one minute later they
will ingest the appropriate dose and strain (either LSN03-016011/A or WS6788A ) of CS17+
ETEC diluted in 30mL sodium bicarbonate buffer. Doses of the challenge inoculum will be
prepared by one of the study staff microbiologists. Treatment with antibiotics will start on
study day 5, or earlier if criteria for early antibiotic treatment are fulfilled. Subjects
will be discharged when they feel well and have 2 consecutive stool cultures negative for
CS17+ ETEC.
For each group of 5 study subjects, the study period will include the screening period, one
month for the inpatient and outpatient phases, and six-months for the final phone check. The
study period, accounting for the serial scheduling of multiple groups of 5, processing
immunology specimens, study analysis and report writing, is 1 ½ years.
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