A Study to Investigate Safety and Tolerability of NDX-3315 and NDX-3324 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 which is symptomatic or uncontrolled, 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 (with the exception of low-dose aspirin as long as the dose remains stable and not increased while on study), 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, known allergy to sedative used for endoscopy). * Healthy Participants Only: A history or current diagnosis of allergic diseases (Should be discussed with Medical Monitor and PI to decide whether exclusionary), autoimmune disease, chronic rhinosinusitis or serum immunoglobulin E (IgE) level ≥100 kU/L. On any medications including NSAIDS and any over the counter (OTC) medications unless it is birth control or acne medications with the exception of Accutane, or if deemed acceptable to use by Medical Monitor and PI.