This study is to find out how different types of capsules or tablets containing EDP1815 move through the GI tract and release the drug after being swallowed. The capsules and tablets also contain a very small dose of a commonly used radioactive label called technetium-99m which is released in the GI tract to be seen on pictures taken by a scanner (gamma scintigraphy).

This is a Phase I single centre, crossover, gamma scintigraphy study to investigate the gastrointestinal transit and disintegration kinetics of capsule and tablet formulations of EDP1815 (which contains a specific pure strain of Prevotella histicola, a natural human commensal organism).

In Part 1, up to 12 healthy male volunteers will receive single doses of EDP1815 administered either as capsules or tablets in 4 treatment periods.

The data generated in Part 1 will be assessed prior to progressing to Part 2 to select formulations and doses to be studied. Part 2 will include gamma scintigraphy in up to 12 healthy volunteers receiving single doses of EDP1815 capsules over up to 4 treatment periods.

The data generated in Part 2 will be assessed prior to progressing to Part 3 to select formulations and doses to be studied. Part 3 will include gamma scintigraphy in up to 12 healthy volunteers receiving single doses of EDP1815 capsules or tablets over up to 4 treatment periods.

The data generated in Part 3 will be assessed prior to progressing to Part 4 to select formulations and doses to be studied. Part 4 will include gamma scintigraphy in up to 12 healthy volunteers receiving single doses of EDP1815 tablets over up to 4 treatment periods.

Each capsule or tablet will contain the radio-isotope technetium-99m complexed to DTPA; 99mTc-DTPA, does not enter the systemic circulation and is routinely used for investigations of this type. Imaging via gamma scintigraphy will be used to assess the gut transit time and disintegration location/rate of the capsules/tablets. The drug will be given fasted or fed.

Key Inclusion Criteria:

1. Male
2. Body weight ≥50 kg and BMI 18-30 kg/m²
3. Healthy

Key Exclusion Criteria:

1. History or presence of any medical condition or abnormal laboratory test findings at screening that could affect the study conduct/results, or make the participant unlikely to fully complete the study or potentially adversely affect their safety due to taking part.
2. History of non-self-limiting gastrointestinal disorders, or currently suffering from disease known to impact gastric emptying, e.g. migraine, Type 1 or Type 2 diabetes mellitus.
3. Any contraindication to gamma scintigraphy.
4. Any non-removable metal objects such as metal plates, screws in the chest or abdominal area.
5. Total radiation dosimetry value which contraindicates participation.
6. Use of prescribed medication within 14 days prior to first dose which could interfere with the study procedures or affect gastric emptying and/or gut transit.
7. Use of over-the-counter (OTC) medication, including vitamins, pro and prebiotics and natural or herbal remedies, within 48 hours prior to first dose.
8. History of alcohol or other substance abuse.
9. Current smoker or recently discontinued smoking (less than 3 months).
10. History of allergy to any component of the dosage form or any other allergy which contraindicates participation.
11. Vegetarian or vegan.
12. Participation in this or another clinical study with an investigational drug within the prior 12 weeks, or more than four other clinical studies in the prior 12 month period.
13. Participants unwilling to comply with contraception requirements from first dose until 90 days (use of condom/spermicide in addition to use of protocol-specified highly effective contraception by female partners who could become pregnant)