A Study to Investigate Safety and Tolerability of NDX-3315 in Healthy Participants and Patients With Eosinophilic Esophagitis

Inclusion Criteria: Healthy Participants: • Participants who are healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and electrocardiogram (ECG) assessment. EoE Participants: Documented diagnosis of EoE (based on prior endoscopy with biopsies showing eosinophils ≥15 / HPF); AND History (by patient report) of recurrent dysphagia and/or other related EoE symptoms (with intake of solids off anti-inflammatory therapy) prior to screening; dysphagia is defined as trouble swallowing solid food, or having solid food stuck, by patient report. Exclusion Criteria: Medical Conditions: Participant with presence of any other disease of the GI tract, including cancer, autoimmune esophageal disease, GERD, Barrett's esophagus, eosinophilic gastritis, enteritis, colitis, or proctitis; inflammatory bowel disease; or celiac disease. Known motility disorder of esophagus; achalasia or suspicion thereof. Sleep apnea, if considered by the investigator a concern for the endoscopic procedure. History of recurrent aspiration pneumonia. History of bleeding disorders, liver cirrhosis or esophageal varices. A current malignancy or previous history of cancer in remission for less than 5 years prior to Screening (participants will not be excluded if they had localized carcinoma of the skin that was resected for cure). Participant with a Body Mass Index >40 m2/kg or inability to undergo a CT (or SPECT scan) due to weight limitations. Participant is pregnant or nursing. Prior/Concomitant Therapy: Participant who is on anticoagulation therapy that, in the investigator or Medical Monitor's opinion, cannot safely come off medication. Use of chronic aspirin, nonsteroidal agents, or anti-coagulants within 2 weeks prior to screening. Use of systemic corticosteroids within 3 months or swallowed topical corticosteroids within 6 weeks prior to Screening visit. Participant is being treated with systemic immunosuppression, carafate (sucralfate), or investigational agent of any kind within less than 3 months or 5 half-lives, whichever is longer, prior to Screening visit (this also includes investigational formulations of marketed products). Diagnostic Assessments: Evidence of clinically significant abnormality in the hematological and biochemical assessments at Screening Visit, specifically: International Normalized Ratio (INR) >1.4; platelet count <80,000/μL and creatinine level >2 mg/dL. ECG: QTcF ≥450 msec for males and QTcF ≥470 msec for females at the time of screening. Other Exclusion Criteria: Any condition that would not permit adequate biopsies of the esophagus (e.g., esophageal varices, significant stricture precluding passage of a 9 mm endoscope). Healthy Participants Only: A history or current diagnosis of allergic diseases (e.g., allergic rhinitis/sinusitis, asthma, atopic dermatitis, food allergies) or serum immunoglobulin E (IgE) level ≥100 kU/L.