24-Week Induction Study of APT-1011 in Adult Subjects With Eosinophilic Esophagitis (EoE) (FLUTE 3)

This is a 24-week randomized, double-blind, placebo-controlled induction study of APT-1011 in adults (≥18 years old) with eosinophilic esophagitis (EoE) followed by a single-arm, open-label extension. This study will evaluate the efficacy and safety of APT-1011 3 mg administered HS (hora somni, at bedtime) for the induction of response to treatment (symptomatic and histologic) over 24 weeks. The open-label extension will continue to evaluate long-term safety in subjects who consent to continue on open-label treatment with APT-1011.

Inclusion Criteria:Adult male or female ≥18 years of age at the time of informed consentEach subject must read, understand, and provide consent on the ICF for this study and be willing and able to adhere to study-related treatment regimens, procedures, and visit scheduleDiagnosis or presumptive diagnosis of EoE that is confirmed during the Screening period by histology that demonstrates ≥15 peak eos/HPF. In order to ensure that a diagnosis can be made, at least 6 biopsies should be taken in total from both proximal and distal esophageal mucosal areas (at least 3 each). Mid-esophageal biopsies are not required (optional). HPF will be defined as a standard area of 235 square microns in a microscope with 40x lens (0.3 mm^2) and 22 mm ocular.Esophagogastroduodenoscopies and biopsies are to be obtained during the Screening periodBiopsies will be read by a central pathologistEsophagogastroduodenoscopies and biopsies performed outside the study will not be accepted to meet eligibility criteriaOptional biopsies may be taken and processed locally for local use, only where specified in the local ICF. If serious pathology is unexpectedly encountered biopsies of such lesions must be processed locallyHave a subject-reported history of ≥6 episodes to a maximum of 30 episodes of dysphagia in a 14-consecutive-day period within 18 days prior to baselineCompletion of the evening eDiary on at least 11 out of the 14-consecutive-day observation period during the 4-week run-in period (Baseline Symptom Assessment).The minimum requirement of 11 days need not be consecutive.Exclusion Criteria:Have known contraindication, hypersensitivity, or intolerance to corticosteroidsHave a contraindication to, or factors that substantially increase the risk of, EGD procedure or esophageal biopsy or have narrowing of the esophagus that precludes EGD with a standard (8-10 mm) endoscopeHave history of an esophageal stricture requiring dilatation within the 12 weeks prior to ScreeningHave any physical, mental, or social condition or history of illness or laboratory abnormality that in the Investigator's judgment might interfere with study procedures or the ability of the subject to adhere to and complete the study or increase the safety risk to the subject such as uncontrolled diabetes or hypertensionHistory of recurrent or current oral or esophageal mucosal infection due to inhaled or nasal corticosteroidsHave any mouth or dental condition that prevents normal eating (excluding braces)Have any condition affecting the esophageal mucosa or altering esophageal motility other than EoE, including erosive esophagitis (grade B or higher as per the Los Angeles Classification of Gastroesophageal Reflux Disease; hiatus hernia longer than 3 cm, Barrett's esophagus, and achalasia)Use of systemic (oral or parenteral) corticosteroids within 30 days before Screening, use of swallowed corticosteroids within 30 days before ScreeningInitiation of either inhaled or nasal corticosteroids or high-potency dermal topical corticosteroids within 30 days before ScreeningUse of calcineurin inhibitors or purine analogues (azathioprine, 6-mercaptopurine) in the 12 weeks before ScreeningUse of potent cytochrome P450 (CYP) 3A4 inhibitors (e.g., ritonavir and ketoconazole) in the 4 weeks before ScreeningInitiation of an elimination diet or elemental diet within 30 days before Screening (diet must remain stable after signing ICF)Abnormal ACTH stimulation defined as a serum cortisol level <16 μg/dL (440 nmol/L) at 60 minutes with ACTH stimulation test using 250 μg cosyntropinUse of biologic immunomodulators, including dupilumab for EoE, with dose last administered within 6 months before Screening (allergy desensitization injection or oral therapies allowed as long as the course of therapy is not altered during the study period)Subjects who have initiated, discontinued, or changed dosage regimen of histamine H2 receptor antagonists, antacids or antihistamines, leukotriene inhibitors, or sodium cromolyn within 4 weeks before qualifying endoscopy during Screening. If already receiving these drugs, the dosage must remain constant throughout the studySubjects who have initiated PPIs within 8 weeks before qualifying endoscopy. If already receiving PPIs, the dosage regimen must remain constant throughout the studyHave gastrointestinal bleeding or documented active peptic ulcer within 4 weeks prior to Screening or entering a new study periodHave chronic infection such as prior or active tuberculosis, active chicken pox or measles, or absence of prior measles, mumps, and rubella vaccine. Subjects with tuberculosis exposure or who live in, or travel to, high endemic areas should be assessed locally for tuberculosis before consideration for the studyImmunosuppression or immunodeficiency disorderCurrent malignancy or malignancy within 3 years of Screening, with the exception of skin cancers other than melanoma. Subjects in remission for at least 3 years post-treatment may be enrolled.Have a history or presence of Crohn's disease, celiac disease, or other inflammatory disease of the gastrointestinal tract, including non-EoE eosinophilic gastrointestinal disorders (EGIDs)Have current drug abuse in the opinion of the InvestigatorHave current alcohol abuse in the opinion of the InvestigatorFemale subjects who are pregnant, breastfeeding, or planning to become pregnant during the studySexually active females of childbearing potential who do not agree to follow highly effective contraceptive methods through the End of Study visitHave received an investigational product as part of a clinical trial within 30 days (or 5 half-lives, whichever is longest) of Screening. Subjects who are currently participating in observational studies or enrolled in patient registries are allowed in this studyHave participated in a prior study with investigational product APT-1011