This is a Phase 2b, multi-center, double-blind, randomized, placebo-controlled, parallel-group study of NKT versus placebo in otherwise healthy adults presenting with acute uncomplicated ILI due to influenza or other respiratory viruses in a community setting.

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) in the predose examinations or >4 hours after dosing of antipyretics if they were taken
   • 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. The time interval between the onset of symptoms and the predose examinations is ≤96 hours. The onset of symptoms is defined as either:

   • Time of the first increase in body temperature (an increase of at least 1º Celsius from normal body temperature)
   • Time when the subject experiences at least one general or respiratory symptom

4. Females of childbearing potential and males agree to use an appropriate method of contraception as detailed in the protocol

Exclusion Criteria:

1. Female subjects who are pregnant, 2 weeks post-partum, or breastfeeding

2. Severe ILI requiring inpatient treatment

3. Any of the following risk factors (according to the CDC's list of People at High Risk for Developing Serious Flu-Related Complications):

   • 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)
   • Extreme obesity (body mass index ≥40 kg/m^2)

4. Presence of any severe or uncontrolled medical or psychiatric illness

5. History of or current autoimmune disease

6. History of recurrent lower respiratory tract infection

7. Any concurrent infection requiring systemic antimicrobial and/or antiviral therapy

8. Female subjects who are pregnant or breastfeeding

9. Any clinically significant electrocardiogram test

10. Received baloxavir, oseltamivir, peramivir, zanamivir, rimantadine, or amantadine within 30 days prior to the pre-dose examinations

11. Received an investigational monoclonal antibody for a viral disease in the last year prior to the pre-dose examinations

12. Received ketotifen fumarate, cromolyn sodium, or nedocromil sodium by any route of administration within 30 days prior to the pre-dose examinations

13. Exposure to an investigational drug within 30 days prior to the pre-dose examinations

14. History of allergic reaction to ketotifen

15. Any prior exposure to norketotifen