• Percentage of participants who successfully complete the dosage regimen with no more than mild symptoms related to EMP-123 dosing [ Time Frame: Throughout study ] [ Designated as safety issue: Yes ]
  

• Occurrence of adverse events [ Time Frame: Throughout study ] [ Designated as safety issue: Yes ]
  
• Rate of desensitization, as determined by peanut endpoint titration prick test in peanut allergic participants [ Time Frame: At pre- and post-treatment periods ] [ Designated as safety issue: No ]
  
• Change in basophil activation [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  
• Decreased Type 2 helper T cell peanut-induced T-lymphocyte phenotype and increased T-lymphocyte regulatory phenotype [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  
• Increase in peanut-specific immunoglobin (IgG4) and IgA [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  
• Decrease in peanut-specific IgE [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  

Peanut allergy is a common ailment in the United States. Research suggests that the prevalence of peanut allergy in the United States has doubled over the last 5 years. Currently, the only effective treatment for peanut allergy is a peanut-free diet and quick access to self-injectable epinephrine. This study will evaluate the safety of a rectally administered product, EMP-123, consisting of three recombinant modified peanut protein antigens encapsulated within dead E. coli. E. coli is a common bacterium found in everyone's colon. E. coli acts like a package to hold the modified peanut proteins. EMP-123 is designed to act as an allergy vaccine with an eventual goal to induce tolerance to the major peanut proteins responsible for peanut allergy.

This study will involve weekly dosing and for females, a pregnancy test will occur at 48 hours before the start of product administration and later during the study. The study will involve two steps. Step 1 will enroll 5 healthy participants who will receive four escalating doses of study product on a weekly basis. Participants will be monitored at the clinic for 2 hours after receiving each dose of study product. Each dosing visit will be followed with a phone interview to assess any adverse effects or symptoms. Participants in Step 1 will maintain a home diary and record any symptoms that occur between visits. After screening, Step 1 will consist of five study visits on Weeks 1, 2, 3, 4, and 8. Vital signs, adverse event monitoring, and review of the home diary will occur at all visits. Breathing tests will occur at most visits. Stool and urine collection will occur at Weeks 4 and 8.

The expected duration of Step 1 is 8 weeks.

If no safety concerns are identified at the conclusion of Step 1, 10 peanut-allergic participants will be enrolled into the second phase of the study, Step 2.

Step 2 is expected to last 20 weeks. Participants in Step 2 will receive weekly dose escalation of the study product for 10 weeks followed by administration every 2 weeks for 6 weeks. Participants will remain in the clinic for 2 hours after every dose is received. Follow-up will then continue for 4 weeks after the conclusion of treatment. Each dosing visit will be followed with a phone interview to assess any adverse effects or symptoms.

After screening, Step 2 will consist of 14 study visits. Vital signs, adverse event monitoring, and a review of the home diary will occur at all visits. Breathing tests will occur at most visits. A skin prick test and stool, blood, and urine collection will occur at select visits.