Efficacy and Safety of Norketotifen in Uncomplicated Influenza-like Illness

Inclusion Criteria: 1. Able to understand the study and comply with all study procedures, and willing to provide written informed consent prior to the pre-dose examinations 2. Symptoms of ILI including all of the following: * Fever ≥38º Celsius (oral) * At least one of the following general systemic symptoms associated with ILI are present with a severity of moderate or greater: headache, feverishness or chills, muscle or joint pain, fatigue * At least one of the following respiratory symptoms associated with ILI are present with a severity of moderate or greater: cough, sore throat, nasal congestion 3. Total symptom severity score (sum of the scores of all 7 individual symptoms) of ≥11 in the predose examinations 4. The time interval between the onset of symptoms and the predose examinations is ≤48 hours. 5. Females of childbearing potential and males agree to use an appropriate method of contraception as detailed in the protocol Exclusion Criteria: 1. Known or suspected infection with Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV2) or Coronavirus Disease 2019 (COVID-19) illness 2. Female subjects who are pregnant, 2 weeks post-partum, or breastfeeding 3. Severe ILI requiring inpatient treatment 4. Any of the following risk factors (according to the CDC's list of People at High Risk for Developing Serious Flu-Related Complications): * Extreme obesity (body mass index ≥40 kg/m\^2) * Residents of nursing homes or other long-term care facilities * American Indians and Alaska natives * Asthma * Chronic lung disease (such as chronic obstructive pulmonary disease or cystic fibrosis) * Neurological and neurodevelopmental conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy \[seizure disorders\], stroke, intellectual disability, moderate to severe developmental delay, muscular dystrophy, or spinal cord injury) * Heart disease (such as congenital heart disease, congestive heart failure, or coronary artery disease) * Blood disorders (such as sickle cell disease) * Endocrine disorders (such as diabetes mellitus) * Kidney disorders * Liver disorders * Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders) * Compromised immune system due to disease or medication (such as subjects with human immunodeficiency virus or cancer, or those on chronic steroids) 5. Presence of any severe or uncontrolled medical or psychiatric illness 6. History of or current autoimmune disease 7. History of recurrent lower respiratory tract infection 8. Any concurrent infection requiring systemic antimicrobial and/or antiviral therapy 9. Any clinically significant electrocardiogram (ECG) test 10. Received baloxavir, oseltamivir, peramivir, zanamivir, rimantadine, or amantadine within 30 days prior to the predose examinations 11. Received an investigational monoclonal antibody for a viral disease in the last year prior to the predose examinations 12. Received ketotifen fumarate, cromolyn sodium, or nedocromil sodium by any route of administration within 30 days prior to the predose examinations 13. Exposure to an investigational drug within 30 days prior to the predose examinations 14. History of allergic reaction to ketotifen 15. Any prior exposure to norketotifen