Clinical Study to Assess the Efficacy of IMM-124E (Travelan®) in a Controlled Human Infection Model

Inclusion Criteria:

1. Male or female between 18 and 50 years of age, inclusive at time of screening visit.

2. General good health, without significant medical illness, abnormal vital signs orphysical examination findings, or clinical laboratory abnormalities, as determinedby the principal investigator (PI) in consultation with the Medical Monitor andSponsor.

3. Demonstrate comprehension of the protocol procedures, requirements, and CHIM thiswill be evaluated by completing a multiple choice comprehension assessment (passinggrade > 70%) during screening and in the consenting process.

4. Willing to participate, as evidenced by signing the informed consent document.

5. Available for all planned follow-up visits.

6. Negative serum pregnancy test at screening and negative serum and/or urine pregnancytest on the day of admittance to the inpatient unit for all female participants. Allfemales must agree to use an efficacious hormonal or barrier method of birth controlduring the study. Efficacious methods of birth control include hormonal birthcontrol methods (oral contraceptive pills, patches, vaginal rings, long-actingreversible contraception, surgical sterilization, condoms with spermicide, orabstinence from intercourse with a male partner. Female participants unable to bearchildren must have this documented (e.g., tubal ligation or hysterectomy).

7. A negative Covid-19 PCR test is required on the day of admission to the unit tocomply with Pharmaron's Covid-19 policy (subjects reporting to admission for Cohort 1 who test positive for COVID-19 may rescreen for Cohort 2)

8. Acceptable hematology and blood chemistry levels as assessed by the PI. i.e., Serumcreatinine <1.3 mg/dL. AST, GGT, amylase, lipase, alkaline phosphatase not to exceed 1.5x upper limit of normal (ULN)

9. Vital signs will be assessed in the supine position and must be within the followingranges:

• Oral body temperature between 35-37oC inclusive

• Systolic blood pressure between 90-140 mmHg inclusive

• Diastolic blood pressure between 55-90 mmHg inclusive

• Pulse rate between 45-90 bpm inclusive

Exclusion Criteria:

1. Presence of a significant medical condition (e.g., psychiatric conditions such assignificant anxiety, depression, or somatization disorder; gastrointestinal disease,such as peptic ulcer, symptoms or evidence of active gastritis/dyspepsia,gastroesophageal reflux disease, inflammatory bowel disease, or irritable bowelsyndrome (as suggested by medical history or medical diagnosis); history of majorgastrointestinal surgery; or laboratory abnormalities that in the opinion of theinvestigator preclude participation in the study. Significant medical conditionsinclude HIV, active Hepatitis B or C infection, ongoing immunosuppression for anyreason, autoimmune disease, any underlying cardiac, pulmonary, endocrine, or renalconditions, any gastrointestinal illness (chronic reflux, inflammatory boweldisease, ulcer), any diabetes mellitus, and other such illnesses that can put avolunteer at increased risk. Exclusionary laboratory abnormalities include anyabnormality that is grade 2 or above, or any two grade 1 laboratory abnormalities.

2. Immunosuppressive illness or evidence of IgA deficiency (serum IgA levels outsidethe normal range). This includes any disease that requires immunosuppressivemedication such corticosteroids, monoclonal antibodies that target key aspects ofthe immune system (e.g. rituximab or TNF-blockers, or any autoimmune disease).

3. Positive serology results for HIV, HBsAg, or HCV antibodies, and confirmatory testsif appropriate.

4. Positive urine drug screen (positive for the presence of amphetamines, barbiturates,opiates, phencyclidine, cocaine, benzodiazepines, methadone, and propoxyphene atscreening and at the discretion of the study physician, with the exception of stablepersons with a diagnosis of ADHD that is well-controlled with a prescribedamphetamine.

5. History of alcohol abuse in the past 3 months or drug abuse in the past year

6. Significant abnormalities in screening laboratory hematology, serum chemistry orelectrocardiogram, as determined by the PI or PI in consultation with the MedicalMonitor and Sponsor. Significant ECG abnormalities include the following:

7. PR > 220 msec

8. QRS complex > 120 msec

9. QTcF > 450 msec (male) or >460 msec (female)

10. Serum bilirubin exceeds upper limit of normal

11. Use of any medication known to affect immune function (e.g., corticosteroids andothers) within 30 days preceding receipt of the investigational products or plannedto be used during the active study period. Any regular systemic corticosteroid willbe exclusionary, while topical, intranasal, and inhaled steroids will be permitted.

12. Nursing or lactating on the day of admittance to the inpatient unit.

13. Inability to tolerate 150 ml of sodium bicarbonate buffer.

14. Recent vaccination (including licensed vaccines) or receipt of an investigationalproduct (within 30 days before challenge through 30 days following the challengedose).

15. History of diarrhea (> 3 unformed or liquid stools over a 24-hour period) in the 2weeks prior to the planned inpatient phase.

16. Fewer than 3 stools per week or more than 3 stools per day as the usual frequency,or loose or liquid stools other than on an occasional basis.

17. Regular use of laxatives or any agent that increases gastric pH (regular defined asat least weekly).

18. Use of proton pump inhibitors, H2 blockers, or antacids within 48 hours of dosing.

19. A fever (≥38.0°C) in the 2 weeks prior to time of challenge.

20. Use of antibiotics during the 30 days before bacterial dosing or receipt of morethan 3 courses of antibiotics over the two months prior to dosing.

21. Blood or plasma donation of one pint or more within 30 days preceding the receipt ofthe investigational products.

22. Lactose intolerance or allergy to milk or milk products.

23. Employment as a health care worker, food handler, childcare worker, or caregiversfor elderly or immunocompromised individuals.

24. Allergy to fluoroquinolones, trimethoprim-sulfamethoxazole, doxycycline, orampicillin/penicillin (excluded if allergic to two of four).

25. History of microbiologically confirmed ETEC infection in the last 3 years.

26. Occupation involving handling of ETEC currently, or in the past 3 years.

27. Symptoms consistent with travelers' diarrhea defined as >3 unformed or liquid stoolsover a 24 hour period concurrent with travel to countries where ETEC infection isendemic (most of the developing world) within 3 years prior to dosing, OR plannedtravel to endemic countries during the length of the study. ETEC endemic countriesinclude all countries in Asia (except for Japan and South Korea) the Middle East,Africa, Mexico, Central and South America.

28. Vaccination for or ingestion of ETEC, cholera, Shigella, or E. coli heat-labiletoxin within 5 years prior to dosing.

29. Any prior experimental infection with ETEC strain H10407, or prior experimentalinfection with other ETEC strains or other bacterial enteric pathogens (Salmonella,Shigella, and Campylobacter) within the past 5 years.