Efficacy, Safety, and Pharmacokinetics of APT-1011 in Subjects With Eosinophilic Esophagitis (EoE)

FLUTE is a phase 2b randomized, double-blind, placebo-controlled dose-ranging clinical trial
of APT-1011 versus placebo in 100 adult subjects (≥18 years of age) diagnosed with EoE.
Efficacy (including histologic, endoscopic, and symptomatic response), safety, and PK of
APT-1011 will be examined. Participants will be given an electronic diary to record symptoms
and medication intake daily.

FLUTE will be conducted in several parts (Screening [4 weeks], followed by a 4-week Baseline
Symptom Assessment, and 2 treatment parts [Part 1: 14-week Induction and Part 2: 38-week
Maintenance]), with a follow-up visit to occur 2 weeks after the final dose of study drug.

In Part 1 of the study, 100 subjects will be randomized 1:1:1:1:1 to receive placebo or one
of 4 active doses of APT-1011. All subjects will receive one tablet 30 minutes after
breakfast and one tablet at bedtime (HS). The dosing groups include: 1.5 mg HS APT-1011, 1.5
mg twice daily (BID) (total daily dose of 3 mg) APT-1011, 3 mg HS APT-1011, and 3 mg BID
(total daily dose of 6 mg) APT-1011, and placebo BID.

In Part 2, all subjects classified as histologic responders at Week 12 will continue to be
treated according to the dosing group to which they were randomized, and non-responders will
receive single-blind 3 mg BID. All subjects who are histologic non-responders at Week 26 will
stop treatment at Week 28 and enter the 2-week follow-up and exit the study. Histologic
responders at Week 26 will continue on the same dose until end-of-study at Week 52.

Subjects will complete a follow-up visit 2 weeks after the final dose of study drug. All
subjects must have a final EGD within 3 weeks prior to completing the Follow-up Visit unless
the subject withdraws consent or has a contraindication to EGD.

Inclusion Criteria:

- Male or female between ≥18 and ≤75 years of age at the time of informed consent

- Signed informed consent

- Evidence of EoE defined by ≥15 peak eosinophils per HPF as measured from proximal and
distal biopsies

- Subject-reported history of ≥3 episodes of dysphagia in the 7 days prior to Screening

- 7-day Global EoE Symptom Score >3 at baseline and at screening

- Willing and able to adhere to study-related treatment regimens, procedures, and visit
schedule

Exclusion Criteria:

- Have known contraindication, hypersensitivity, or intolerance to corticosteroids;

- Have 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;

- Presence of oral or esophageal mucosal infection of any type;

- Have any mouth or dental condition that prevents normal eating;

- Have any condition affecting the esophageal mucosa or altering esophageal motility
other than EoE;

- Use of systemic corticosteroids within 60 days prior to Screening, use of
inhaled/swallowed corticosteroids within 30 days prior to Screening, or extended use
of high-potency dermal topical corticosteroids within 30 days prior to Screening;

- Initiation of an elimination diet or elemental diet within 30 days before Screening
(diet must remain stable after signing ICF);

- Morning serum cortisol level ≤5 μg/dL (138 nmol/L);

- Use of biologic immunomodulators in the 24 weeks prior to Screening;

- Use of calcineurin inhibitors or purine analogues, or potent cytochrome P450 (CYP) 3A4
inhibitors in the 12 weeks prior to Screening;

- Have a contraindication to or factors that substantially increase the risk of EGD or
esophageal biopsy or have narrowing of the esophagus that precludes EGD with a
standard 9 mm endoscope;

- Have a history of an esophageal stricture requiring dilatation within the previous 12
weeks prior to Screening;

- Have initiated, discontinued or changed dosage regimen of PPIs, H2 antagonists,
antacids or antihistamines for any condition such as GERD or allergic rhinitis within
4 weeks prior to qualifying endoscopy. These drugs must remain constant throughout the
study.

- A serum cortisol level <18 μg/dL (497 nmol/L) at 60 minutes with adrenocorticotropic
hormone (ACTH) stimulation test using 250 μg cosyntropin (i.e., a positive result on
the ACTH stimulation test).