This is a Phase 2a study to evaluate the efficacy and safety of Norketotifen (NKT) in subjects with allergic rhinitis.

This is a single-center, double-blind, randomized, placebo-controlled, 3-way crossover study evaluating the efficacy and safety of NKT in adult subjects with allergen-induced allergic rhinitis in an allergen challenge chamber.

Inclusion Criteria:

• Ability and willingness to provide informed consent and comply with the protocol procedures
• Males and females, age 18 to 45 years, inclusive
• Other than seasonal allergic rhinitis, participant is healthy as determined by pre-study medical history, physical examination and vital signs. Any chronic conditions that may interfere with the study outcomes or the subject's safety will be considered clinically significant and a reason for exclusion.
• History of seasonal allergic rhinitis to mountain cedar pollen for at least the past 2 consecutive seasons
• Positive mountain cedar pollen skin prick test at Screening or within 12 months prior to Screening (wheal diameter ≥5 mm larger than the negative control)
• For females, negative serum pregnancy test. Females of childbearing potential and males must agree to use required contraception as outlined in the protocol

Exclusion Criteria:

• Female subjects who are pregnant or lactating
• Any history of epilepsy, diabetes mellitus, blood pressure abnormalities or cardiac arrhythmias
• Presence of any uncontrolled medical or psychiatric illness
• Treatment for controlled concurrent medical conditions has not been stable in terms of either doses or medications for at least 30 days prior to the baseline visit or is anticipated to change during the study
• Current use of or expected use of any of the prohibited medications within the indicated withholding timeframes as outlined in the protocol
• History of any illness that, in the opinion of the study investigator, might confound the results of the study or poses an additional risk to the subject by their participation in the study
• Any history of malignancy within the past 5 years, with the exception of non-melanoma skin cancer
• History of pulmonary disease and/or active asthma requiring daily drug therapy. Mild, intermittent asthma is permitted (managed with short acting beta-agonist less than 3 times per week). Isolated exercise-induced bronchospasm is also permitted
• Any infection or inflammatory condition within the 2 weeks prior to screening
• Positive human immunodeficiency virus (HIV), hepatitis B (HBV), or hepatitis C (HCV) antibody screen
• Any clinically significant abnormal laboratory or ECG test. Presence of thrombocytopenia at screening is exclusionary
• Evidence of illicit drug use or positive urine Class A drug, alcohol, or cotinine screen
• Regular use of tobacco or nicotine containing products, including vaping, within 1 year prior to Screening
• Received any investigational drug within 30 days prior to Screening
• Any prior exposure to norketotifen
• History of allergic reaction to ketotifen
• In the opinion of the investigator, subject would be unlikely to comply with required study visits, self-assessments, and interventions