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The Effectiveness of CD388 to Prevent Flu in an Influenza Challenge Model in Healthy Adults

A Proof-of-concept, Randomized, Double-blind, Placebo-controlled, Phase 2a Study to Assess the Prophylactic Antiviral Activity Against Influenza, Safety, Tolerability, and Pharmacokinetics of CD388 Via a Human Viral Challenge Model

Status
Completed
Phases
Phase 2
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT05523089
Enrollment
59
Registered
2022-08-31
Start date
2022-09-09
Completion date
2023-07-17
Last updated
2024-09-19

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Influenza

Brief summary

The purpose of this study is to evaluate the preventative antiviral activity of CD388, as compared to saline placebo, when administered as a single dose to healthy adult participants in a human viral challenge model of influenza.

Detailed description

This is a single-center, randomized, double-blind, placebo-controlled, proof-of-concept study in healthy adult male and female participants 18 to 55 years of age, inclusive. The primary goal of this Phase 2a study is to assess the prophylactic antiviral activity against influenza, safety, tolerability, and pharmacokinetics (PK) of CD388 via a human viral challenge (HVC) model, and to explore the impact of dose levels on efficacy. Each participant will receive a single administration of CD388 or placebo; multiple dose levels of CD388 may be evaluated.

Interventions

DRUGSaline placebo

Sterile normal saline for injection

COMBINATION_PRODUCTCD388

CD388 liquid for injection

Sponsors

Janssen Pharmaceuticals
CollaboratorINDUSTRY
Cidara Therapeutics Inc.
Lead SponsorINDUSTRY

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
QUADRUPLE (Subject, Caregiver, Investigator, Outcomes Assessor)

Eligibility

Sex/Gender
ALL
Age
18 Years to 55 Years
Healthy volunteers
Yes

Inclusion criteria

1. Written informed consent signed and dated by the participant and the PI/investigator obtained before any assessment is performed. 2. Adult male or female aged between 18 and 55 years old, inclusive, on the day prior to signing the consent form. 3. A total body weight ≥50 kilograms (kg) and body mass index (BMI) ≥18 kg/meter squared (m\^2) and ≤35kg/m\^2. 4. In good health with no history, or current evidence, of clinically significant medical conditions, and no clinically significant test abnormalities that will interfere with participant safety, as defined by medical history, physical examination (including vital signs), electrocardiogram (ECG), and routine laboratory tests as determined by the Principal Investigator (PI)/investigator. 5. Participants will have a documented medical history either prior to entering the study or following medical history review with the study physician at screening. 6. The following criteria are applicable to female participants participating in the study. 1. Females of childbearing potential must have a negative pregnancy test prior to enrolment. 2. Females of non-childbearing potential: 1. Postmenopausal females defined as amenorrhea for ≥12 months with no alternative medical cause. A high follicle-stimulating hormone (FSH) level, within appropriate postmenopausal range, may be used to confirm postmenopausal state in the absence of combined hormonal contraception or hormone replacement therapy. If there is \<12 months of amenorrhea 2 FSH samples are required at least 4 to 6 weeks apart. 2. Documented status as being surgically sterile (e.g., tubal ligation, hysterectomy, bilateral salpingectomy, and bilateral oophorectomy). 7. The following criteria apply to female and male participants: 1. Female participants of childbearing potential must use 1 form of highly effective contraception. Hormonal methods must be in place from at least 2 weeks prior to the first study visit. The contraception use must continue until 5 effective half-lives (205 days) after the last dose of investigational medicinal product (IMP). Highly effective contraception is as described below: 1. Established use of hormonal methods of contraception described below (for a minimum of 30 days prior to the first study visit). When hormonal methods of contraception are used, male partners are required to use a condom with a spermicide: * a) combined (estrogen- and progestogen containing) hormonal contraception associated with inhibition of ovulation: * (i) oral * (ii) intravaginal * (iii) transdermal * b) progestogen-only hormonal contraception associated with inhibition of ovulation: * (i) oral * (ii) injectable * (iii) implantable 2. Intrauterine device. 3. Intrauterine hormone-releasing system. 4. Bilateral tubal ligation. 5. Male sterilization (with the appropriate post vasectomy documentation of the absence of sperm in the ejaculate) where the vasectomized male is the sole partner for that woman. 6. True abstinence - sexual abstinence is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical study and the preferred and usual lifestyle of the participant. 2. Male participants must agree to the contraceptive requirements below at entry to quarantine and continuing until 5 effective half-lives (205 days) after the last dose of IMP. 1. Use a condom with a spermicide to prevent pregnancy in a female partner or to prevent exposure of any partner (male or female) to the IMP. 2. Male sterilization with the appropriate post vasectomy documentation of the absence of sperm in the ejaculate (please note that the use of condom with spermicide will still be required to prevent partner exposure). This applies only to males participating in the study. 3. In addition, for female partners of childbearing potential, that partner must use another form of contraception such as one of the highly effective methods mentioned above for female participants. 4. True abstinence - sexual abstinence is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical study and the preferred and usual lifestyle of the participant. 3. In addition to the contraceptive requirements above, male participants must agree not to donate sperm following discharge from quarantine until 5 effective half-lives (205 days) after the last dose of IMP. 8. Sero-suitable for the challenge virus. A participant must be sero-suitable to take part in the study, i.e., he/she must have no or low pre-existing serum levels of antibodies specific to the challenge agent. Serology testing will be carried out by a hemagglutination inhibitory assay to determine serum antibody titers. As an example, a participant is considered sero-suitable if their serology (hemagglutination inhibition \[HAI\]) titer result is ≤10.

Exclusion criteria

1. History of, or currently active, symptoms or signs suggestive of upper respiratory tract (URT) or lower respiratory tract (LRT) infection within 4 weeks prior to the first study visit. 2. Any history or evidence of any clinically significant or currently active cardiovascular, respiratory, dermatological, gastrointestinal, endocrinological, hematological, hepatic, immunological (including immunosuppression), metabolic, urological, renal, neurological, or psychiatric disease and/or other major disease that, in the opinion of the PI/investigator may interfere with a participant completing the study and necessary investigations. The following conditions apply: 1. Participants with a history of resolved depression and/or anxiety 1 or more years ago can be included if the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder Questionnaire (GAD-7) is less than or equal to 4 on admission. Participants with a history of stress-related illness, which is not ongoing or requiring current therapy, with good evidence of preceding stressors may be included at the PI's discretion. As required, participants will be assessed prior to enrolment with a PHQ-9 and GAD-7 questionnaire. 2. Rhinitis (including hay fever) which is clinically active or history of moderate to severe rhinitis, or history of seasonal allergic rhinitis likely to be active at the time of inclusion into the study and/or requiring regular nasal corticosteroids on an at least weekly basis, within 30 days of admission to quarantine will be excluded. Participants with a history of currently inactive rhinitis (within the last 30 days) or mild rhinitis may be included at the PI's discretion. 3. Atopic dermatitis/eczema which is clinically severe and/or requiring moderate to large amounts of daily dermal corticosteroids will be excluded. Participants with mild to moderate atopic dermatitis/eczema, taking small amounts of regular dermal corticosteroids may be included at the PI's discretion. 4. Any concurrent serious illness, including history of malignancy, that may interfere with a participant completing the study. Basal cell carcinoma within 5 years of initial diagnosis or with evidence of recurrence is also an exclusion. 5. Participants reporting physician-diagnosed migraine can be included provided there are no associated neurological symptoms such as hemiplegia or visual loss. Cluster headache/migraine or prophylactic treatment for migraine is an exclusion. 6. Participants with physician diagnosed mild irritable bowel syndrome not requiring regular treatment can be included at the discretion of the PI. 7. Participants with a history of asthma where their last symptoms/treatment were in adolescence and over 6 years ago may be included at the discretion of the PI. Any participants with symptoms or treatment in adulthood would be excluded. 3. Any participants who have smoked ≥10 pack years at any time (10 pack years is equivalent to 1 pack of 20 cigarettes a day for 10 years). 4. Females who: 1. Are breastfeeding, or 2. Have been pregnant within 6 months prior to the study, or 3. Have a positive pregnancy test at any point during screening or prior to dosing with IMP. 5. Lifetime history of anaphylaxis and/or a history of severe allergic reaction or significant intolerance to any food or drug in the last 12 months, as assessed by the PI. 6. Venous access deemed inadequate for the phlebotomy and cannulation demands of the study. 7. . . 1. Any significant abnormality altering the anatomy of the nose in a substantial way or nasopharynx that may interfere with the aims of the study and, in particular, any of the nasal assessments or viral challenge (historical nasal polyps can be included, but large nasal polyps causing current and significant symptoms and/or requiring regular treatments in the last month will be excluded). 2. Any clinically significant history of epistaxis (large nosebleeds) within the last 3 months of the first study visit and/or history of being hospitalized due to epistaxis on any previous occasion. 3. Any nasal or sinus surgery within 3 months of the first study visit. 8. . . 1. Evidence of vaccinations within the 4 weeks prior to the planned date of dosing with IMP. 2. Intention to receive any vaccination(s) before the last day of follow-up (with the exception of vaccinations recommended for Coronavirus Disease 2019 \[COVID-19\] as defined by Medicines and Healthcare products Regulatory Agency (MHRA)/government vaccination guidelines). 3. No travel restrictions apply after the Day 28 \[±3 days\] follow-up visit; however, we expect participants to be available to attend the clinic at the Day 60, Day 120, and Day 180 follow-up visits. 4. Receipt of influenza vaccine in the last 6 months prior to the planned date of viral challenge. 9. Receipt of blood or blood products, or loss (including blood donations) of 550 milliliters (mL) or more of blood during the 3 months prior to the planned dosing with IMP or planned during the 3 months after the final visit. 10. . . 1. Receipt of any investigational drug within 3 months prior to the planned date of dosing with IMP. 2. Receipt of 3 or more investigational drugs within the previous 12 months prior to the planned date of dosing with IMP. 3. Prior inoculation with a virus from the same virus-family as the challenge virus. 4. Prior participation in another human viral challenge (HVC) study with a respiratory virus in the preceding 3 months, taken from the date of viral challenge in the previous study to the date of expected viral challenge in this study. 11. Use or anticipated use during the conduct of the study of concomitant medications (prescription and/or non-prescription), including vitamins or herbal and dietary supplements within the specified windows, unless in the opinion of the study physician/PI, the medication will not interfere with the study procedures or compromise participant safety. Specifically, the following are excluded: 1. Herbal supplements within 7 days prior to the planned date of dosing with IMP. 2. Chronically used medications, vitamins, or dietary supplements within 21 days prior to the planned date of dosing with IMP. 3. Over-the-counter medications (e.g., paracetamol or ibuprofen) where the dose taken over the preceding 7 days prior to the planned date dosing with IMP has exceeded the maximum permissible 24-hour dose (e.g., ≥4 grams paracetamol over the preceding week). 4. Systemic antiviral administration within 4 weeks of the planned date of dosing with IMP. 12. . . 1. Confirmed positive test for drugs of misuse and cotinine on first study visit. One repeat test is allowed at PI discretion. 2. Recent history or presence of alcohol addiction, or excessive use of alcohol (weekly intake in excess of 28 units alcohol; 1 unit being a half glass of beer, a small glass of wine, or a measure of spirits), or excessive consumption of xanthine-containing substances (e.g., daily intake in excess of 5 cups of caffeinated drinks, e.g., coffee, tea, cola). 13. A forced expiratory volume in 1 second (FEV1) \<80 percent. 14. Positive human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV) test (HIV positive - via 3 confirmatory tests - Vidas, Genenius, and Determine; HBV confirmed via hepatitis B surface antigen \[HbsAG\], hepatitis B surface antibody \[anti-HBs\], and hepatitis B core antibody \[anti-HBc\] \[immunoglobulin G/immunoglobulin M\]; and HCV confirmed via hepatitis C viral load). 15. Presence of fever, defined as participant presenting with a temperature reading of ≥37.9 degrees Celsius (°C) on Day -7/-6 and/or pre-dose on Day -5. 16. Those employed or immediate relatives of those employed at hVIVO Services Limited (hVIVO) or the sponsor. 17. Any other finding that, in the opinion of the PI/investigator, deems the participant unsuitable for the study.

Design outcomes

Primary

MeasureTime frameDescription
Mean Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral ChallengeDay 1 (evening [pm]); Days 2, 3, 4, 5, 6, and 7 (morning [am] and pm); Day 8 (am)Evaluation of the prophylactic effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on nasal samples starting 1 day post viral challenge.
Median Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral ChallengeDay 1 (evening [pm]); Days 2, 3, 4, 5, 6, and 7 (morning [am] and pm); Day 8 (am)Evaluation of the prophylactic effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on nasal samples starting 1 day post viral challenge.

Secondary

MeasureTime frameDescription
Time to Confirmed Negative Test by qRT-PCR After Influenza Viral ChallengeFrom Day 1 (pm) until the first confirmed undetectable assessment after peak measurement, assessed up to Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to confirmed negative test for influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.
Mean Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by viral culture on nasal samples starting 1 day post viral challenge.
Median Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by viral culture on nasal samples starting 1 day post viral challenge.
Mean Peak Viral Load by Viral Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantitative viral culture measurements in nasal samples starting 1 day post viral challenge.
Median Peak Viral Load by Viral Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantitative viral culture measurements in nasal samples starting 1 day post viral challenge.
Time to Confirmed Negative Test by Viral Culture After Influenza Viral ChallengeFrom Day 1 (pm) until the first confirmed undetectable assessment after peak measurement, assessed up to Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to confirmed negative test for influenza as determined by quantifiable viral culture measurements in nasal samples starting 1 day post viral challenge.
Mean Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral ChallengeThree (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on TSS-AUC as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.
Median Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral ChallengeThree (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on TSS-AUC as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.
Mean Peak Total Clinical Symptoms Score (TSS) After Influenza Viral ChallengeThree (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) TSS score as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.
Median Peak Total Clinical Symptoms Score (TSS) After Influenza Viral ChallengeThree (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) TSS score as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.
Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeFrom Day 1 up to Day 8Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) daily symptom score (i.e., individual maximum daily sum of symptom score) as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment as the sum of the scores given to the 13 symptoms, giving possible TSS values from 0 to 39.
Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeFrom Day 1 up to Day 8Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) daily symptom score (i.e., individual maximum daily sum of symptom score) as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment as the sum of the scores given to the 13 symptoms, giving possible TSS values from 0 to 39.
Time to Symptom Resolution After Influenza Viral ChallengeStarting Day 1, from the time of peak daily symptom score until the time of returning to baseline score, up to Day 8Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to symptom resolution (i.e., first time with Total Symptom Score \[TSS\] equal to the TSS at baseline after which no further increase above the baseline TSS was observed) as measured by graded daily symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. An individual TSS is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.
Number of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed influenza infection, defined as 2 quantifiable (≥ lower limit of quantification \[LLOQ\]) qRT-PCR measurements (reported on 2 or more independent nasal samples over 2 days), starting 1 day post viral challenge.
Mean Peak Viral Load by qRT-PCR After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.
Number of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the number of participants with at least 1 positive quantitative (≥LLOQ) cell culture measurement in nasal samples starting 1 day post viral challenge.
Percentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with at least 1 positive quantitative (≥LLOQ) cell culture measurement in nasal samples starting 1 day post viral challenge.
Number of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge• For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Percentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge• For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Number of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral Challenge• For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For symptom scoring measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed moderately severe symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * One or more symptoms of grade ≥2 at a single time point (i.e., on any individual symptom card), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Percentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral Challenge• For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For symptom scoring measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed moderately severe symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * One or more symptoms of grade ≥2 at a single time point (i.e., on any individual symptom card), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Number of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge• For viral culture measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the number of participants with culture laboratory-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * Lab-confirmed culturable influenza infection (1 quantifiable \[≥LLOQ\] cell culture measurement in nasal samples), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Percentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge• For viral culture measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with culture laboratory-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * Lab-confirmed culturable influenza infection (1 quantifiable \[≥LLOQ\] cell culture measurement in nasal samples), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.
Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of ParticipantsFrom Day -5 (dosing) up to Day 0 (viral challenge)Evaluation of the occurrence of solicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of inoculation with the influenza challenge virus, based on the number of participants reporting any solicited AE. Solicited AEs are those predefined events relating to reactogenicity (pain, tenderness, erythema/redness, induration/swelling) for which participants were specifically questioned and which were noted by participants in a participant diary.
Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of EventsFrom Day -5 (dosing) up to Day 0 (viral challenge)Evaluation of the occurrence of solicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of inoculation with the influenza challenge virus, based on the number of events reported. Solicited AEs are those predefined events relating to reactogenicity (pain, tenderness, erythema/redness, induration/swelling) for which participants were specifically questioned and which were noted by participants in a participant diary.
Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsFrom Day -5 (dosing) up to Day 28 (±3 days)Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 28 follow-up visit, based on the number of participants for whom any AE is observed. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 1 (from Day -5 dosing to just before challenge virus inoculation on Day 0) * Period 2 (from Day 0 challenge virus inoculation to actual discharge from the quarantine unit \[as scheduled on Day 8 or later at PI's decision\]) * Period 3 (from actual discharge from the quarantine unit to Day 28 (±3 days)
Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsFrom Day -5 (dosing) up to Day 28 (±3 days)Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 28 follow-up visit, based on the number of events reported. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 1 (from Day -5 dosing to just before challenge virus inoculation on Day 0) * Period 2 (from Day 0 challenge virus inoculation to actual discharge from the quarantine unit \[as scheduled on Day 8 or later at PI's decision\]) * Period 3 (from actual discharge from the quarantine unit to Day 28 (±3 days)
Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsFrom Day -5 (dosing) up to Day 180 (±14 days)Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 180 final follow-up visit, based on the number of participants for whom any AE was observed. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 3 (from actual discharge from the quarantine unit to Day 28 \[±3 days\]) * Period 4 (from Day 28\[±3 days\] to the final follow-up visit \[Day 180 ±14 days\]) * Across All Periods (from Day -5 dosing to the final follow-up visit \[Day 180 ±14 days\])
Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsFrom Day -5 (dosing) up to Day 180 (±14 days)Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 180 final follow-up visit, based on the number of events reported. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 3 (from actual discharge from the quarantine unit to Day 28 \[±3 days\]) * Period 4 (from Day 28\[±3 days\] to the final follow-up visit \[Day 180 ±14 days\]) * Across All Periods (from Day -5 dosing to the final follow-up visit \[Day 180 ±14 days\])
Percentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed influenza infection, defined as 2 quantifiable (≥ lower limit of quantification \[LLOQ\]) qRT-PCR measurements (reported on 2 or more independent nasal samples over 2 days), starting 1 day post viral challenge.
Median Peak Viral Load by qRT-PCR After Influenza Viral ChallengeDay 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.

Countries

United Kingdom

Participant flow

Recruitment details

Up to 168 participants in up to 2 cohorts were planned for enrollment in the study. Due to low participant eligibility, the randomization schedule was changed in Cohort 1 after the first quarantine group to only randomize participants to the 150 mg CD388 and placebo arms. With only 2 participants in the 50 mg CD388 arm, safety and demographic data only have been reported. Based on data from the planned interim analysis of Cohort 1, a decision was made to not proceed with Cohort 2.

Participants by arm

ArmCount
Placebo
Up to 30 participants randomized to receive a single dose of saline placebo, administered by subcutaneous (SQ) injection, prior to being inoculated with the influenza challenge virus Saline placebo: Sterile normal saline for injection
29
50 mg CD388
Up to 30 participants randomized to receive a single dose of 50 milligrams (mg) CD388, administered by SQ injection, prior to being inoculated with the influenza challenge virus CD388: CD388 liquid for injection
2
150 mg CD388
Up to 30 participants randomized to receive a single dose of 150 mg CD388, administered by SQ injection, prior to being inoculated with the influenza challenge virus CD388: CD388 liquid for injection
28
Total59

Withdrawals & dropouts

PeriodReasonFG000FG001FG002
Overall StudyLost to Follow-up100
Overall StudyWithdrawal by Subject100

Baseline characteristics

CharacteristicPlacebo50 mg CD388150 mg CD388Total
Age, Continuous31.00 years27.50 years32.00 years31.00 years
Body Mass Index (BMI)25.63 kilograms/meter^2 (kg/m^2)
STANDARD_DEVIATION 3.49
25.15 kilograms/meter^2 (kg/m^2)
STANDARD_DEVIATION 2.47
26.09 kilograms/meter^2 (kg/m^2)
STANDARD_DEVIATION 4.45
25.83 kilograms/meter^2 (kg/m^2)
STANDARD_DEVIATION 3.91
Ethnicity (NIH/OMB)
Hispanic or Latino
0 Participants0 Participants0 Participants0 Participants
Ethnicity (NIH/OMB)
Not Hispanic or Latino
29 Participants2 Participants28 Participants59 Participants
Ethnicity (NIH/OMB)
Unknown or Not Reported
0 Participants0 Participants0 Participants0 Participants
Height1.72 meters (m)1.70 meters (m)
STANDARD_DEVIATION 0.11
1.77 meters (m)1.74 meters (m)
Race (NIH/OMB)
American Indian or Alaska Native
0 Participants0 Participants0 Participants0 Participants
Race (NIH/OMB)
Asian
2 Participants1 Participants2 Participants5 Participants
Race (NIH/OMB)
Black or African American
1 Participants0 Participants3 Participants4 Participants
Race (NIH/OMB)
More than one race
0 Participants0 Participants0 Participants0 Participants
Race (NIH/OMB)
Native Hawaiian or Other Pacific Islander
0 Participants0 Participants0 Participants0 Participants
Race (NIH/OMB)
Unknown or Not Reported
2 Participants0 Participants0 Participants2 Participants
Race (NIH/OMB)
White
24 Participants1 Participants23 Participants48 Participants
Region of Enrollment
United Kingdom
29 participants2 participants28 participants59 participants
Sex: Female, Male
Female
9 Participants0 Participants13 Participants22 Participants
Sex: Female, Male
Male
20 Participants2 Participants15 Participants37 Participants
Weight76.29 kilograms (kg)
STANDARD_DEVIATION 13.26
72.40 kilograms (kg)
STANDARD_DEVIATION 2.55
79.68 kilograms (kg)
STANDARD_DEVIATION 19.02
75.20 kg

Adverse events

Event typeEG000
affected / at risk
EG001
affected / at risk
EG002
affected / at risk
EG003
affected / at risk
deaths
Total, all-cause mortality
0 / 290 / 20 / 280 / 59
other
Total, other adverse events
19 / 291 / 221 / 2841 / 59
serious
Total, serious adverse events
0 / 290 / 20 / 280 / 59

Outcome results

Primary

Mean Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge

Evaluation of the prophylactic effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (evening [pm]); Days 2, 3, 4, 5, 6, and 7 (morning [am] and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge16.09 log[10] copies/milliliter (mL)*hourStandard Deviation 11.86
150 mg CD388Mean Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge10.70 log[10] copies/milliliter (mL)*hourStandard Deviation 8.01
p-value: 0.03995% CI: [-5.7, 0]Wilcoxon (Mann-Whitney)
Primary

Median Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge

Evaluation of the prophylactic effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (evening [pm]); Days 2, 3, 4, 5, 6, and 7 (morning [am] and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge8.52 log[10] copies/mL*hour
150 mg CD388Median Area Under the Viral Load-Time Curve (VL-AUC) After Influenza Viral Challenge6.40 log[10] copies/mL*hour
Secondary

Mean Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on TSS-AUC as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.

Time frame: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge7.66 TSS points*dayStandard Deviation 14.13
150 mg CD388Mean Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge2.22 TSS points*dayStandard Deviation 4.86
p-value: 0.287795% CI: [-11.2, 0.3]Wilcoxon (Mann-Whitney)
Secondary

Mean Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by viral culture on nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge5.82 log[10] copies/mL*hourStandard Deviation 3.7
150 mg CD388Mean Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge3.95 log[10] copies/mL*hourStandard Deviation 1.57
p-value: 0.158795% CI: [-2.4, 0]Wilcoxon (Mann-Whitney)
Secondary

Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) daily symptom score (i.e., individual maximum daily sum of symptom score) as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment as the sum of the scores given to the 13 symptoms, giving possible TSS values from 0 to 39.

Time frame: From Day 1 up to Day 8

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (MEAN)Dispersion
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 51.07 total symptom scoreStandard Deviation 2.12
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 10.64 total symptom scoreStandard Deviation 1.5
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 60.79 total symptom scoreStandard Deviation 1.91
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 32.79 total symptom scoreStandard Deviation 5.1
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 70.43 total symptom scoreStandard Deviation 1.53
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 42.11 total symptom scoreStandard Deviation 3.83
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 8 Discharge0.15 total symptom scoreStandard Deviation 0.6
PlaceboMean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 22.29 total symptom scoreStandard Deviation 4.6
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 8 Discharge0.11 total symptom scoreStandard Deviation 0.42
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 10.46 total symptom scoreStandard Deviation 0.84
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 20.75 total symptom scoreStandard Deviation 2.12
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 40.82 total symptom scoreStandard Deviation 1.85
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 50.36 total symptom scoreStandard Deviation 0.87
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 60.39 total symptom scoreStandard Deviation 0.69
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 70.07 total symptom scoreStandard Deviation 0.26
150 mg CD388Mean Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 31.25 total symptom scoreStandard Deviation 3.15
Secondary

Mean Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) TSS score as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.

Time frame: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge3.54 total symptom scoreStandard Deviation 5.34
150 mg CD388Mean Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge1.79 total symptom scoreStandard Deviation 3.12
p-value: 0.251795% CI: [-4.1, 0.6]Wilcoxon (Mann-Whitney)
Secondary

Mean Peak Viral Load by qRT-PCR After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Peak Viral Load by qRT-PCR After Influenza Viral Challenge4.28 log[10] copies/mLStandard Deviation 2.94
150 mg CD388Mean Peak Viral Load by qRT-PCR After Influenza Viral Challenge2.84 log[10] copies/mLStandard Deviation 2.4
p-value: 0.018595% CI: [-2.9, 0]Wilcoxon (Mann-Whitney)
Secondary

Mean Peak Viral Load by Viral Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantitative viral culture measurements in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEAN)Dispersion
PlaceboMean Peak Viral Load by Viral Culture After Influenza Viral Challenge2.13 log[10] copies/mLStandard Deviation 2.1
150 mg CD388Mean Peak Viral Load by Viral Culture After Influenza Viral Challenge1.07 log[10] copies/mLStandard Deviation 1.18
p-value: 0.023695% CI: [-2, -0.1]Wilcoxon (Mann-Whitney)
Secondary

Median Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on TSS-AUC as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.

Time frame: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge0.45 TSS points*day
150 mg CD388Median Area Under the Total Clinical Symptoms Score-Time Curve (TSS-AUC) After Influenza Viral Challenge0.86 TSS points*day
Secondary

Median Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on VL-AUC of influenza challenge virus as determined by viral culture on nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge3.29 log[10] copies/mL*hour
150 mg CD388Median Area Under the Viral Load-Time Curve (VL-AUC) by Viral Culture After Influenza Viral Challenge3.29 log[10] copies/mL*hour
Secondary

Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) daily symptom score (i.e., individual maximum daily sum of symptom score) as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment as the sum of the scores given to the 13 symptoms, giving possible TSS values from 0 to 39.

Time frame: From Day 1 up to Day 8

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (MEDIAN)
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 10.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 20.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 30.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 40.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 50.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 60.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 70.00 total symptom score
PlaceboMedian Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 8 Discharge0.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 8 Discharge0.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 10.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 50.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 20.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 70.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 30.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 60.00 total symptom score
150 mg CD388Median Individual Peak Daily Total Clinical Symptoms Score After Influenza Viral ChallengeQuarantine Day 40.00 total symptom score
Secondary

Median Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) TSS score as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. At each assessment, the participant provides scores from 0 to 3 for a list of 13 symptoms (runny nose, stuffy nose, sneezing, sore throat, earache, malaise/tiredness, headache, muscle and/or joint ache, chilliness/feverishness, cough, chest tightness, shortness of breath, and wheeze). Grade 0: no symptoms; grade 1: just noticeable; grade 2: clearly bothersome from time to time but does not interfere with normal daily activities; grade 3: quite bothersome most or all the time and stops participation in activities. An individual Total Symptom Score (TSS) is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.

Time frame: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge1.00 total symptom score
150 mg CD388Median Peak Total Clinical Symptoms Score (TSS) After Influenza Viral Challenge1.00 total symptom score
Secondary

Median Peak Viral Load by qRT-PCR After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Peak Viral Load by qRT-PCR After Influenza Viral Challenge3.79 log[10] copies/mL
150 mg CD388Median Peak Viral Load by qRT-PCR After Influenza Viral Challenge0.97 log[10] copies/mL
Secondary

Median Peak Viral Load by Viral Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the peak (i.e., maximum) viral load of influenza as determined by quantitative viral culture measurements in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureValue (MEDIAN)
PlaceboMedian Peak Viral Load by Viral Culture After Influenza Viral Challenge0.50 log[10] copies/mL
150 mg CD388Median Peak Viral Load by Viral Culture After Influenza Viral Challenge0.50 log[10] copies/mL
Secondary

Number of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the number of participants with at least 1 positive quantitative (≥LLOQ) cell culture measurement in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboNumber of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeNo Positive Quantitative (≥LLOQ) Cell Culture17 Participants
PlaceboNumber of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeAt Least 1 Positive Quantitative (≥LLOQ) Cell Culture11 Participants
150 mg CD388Number of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeNo Positive Quantitative (≥LLOQ) Cell Culture22 Participants
150 mg CD388Number of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeAt Least 1 Positive Quantitative (≥LLOQ) Cell Culture6 Participants
p-value: 0.1224Fisher Exact
Secondary

Number of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the number of participants with culture laboratory-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * Lab-confirmed culturable influenza infection (1 quantifiable \[≥LLOQ\] cell culture measurement in nasal samples), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For viral culture measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboNumber of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo Culture Lab-confirmed Symptomatic Influenza Infection20 Participants
PlaceboNumber of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeCulture Lab-confirmed Symptomatic Influenza Infection8 Participants
150 mg CD388Number of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo Culture Lab-confirmed Symptomatic Influenza Infection24 Participants
150 mg CD388Number of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeCulture Lab-confirmed Symptomatic Influenza Infection4 Participants
p-value: 0.1645Fisher Exact
Secondary

Number of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed influenza infection, defined as 2 quantifiable (≥ lower limit of quantification \[LLOQ\]) qRT-PCR measurements (reported on 2 or more independent nasal samples over 2 days), starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboNumber of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Influenza Infection14 Participants
PlaceboNumber of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Influenza Infection14 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Influenza Infection22 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Influenza Infection6 Participants
p-value: 0.0248Fisher Exact
Secondary

Number of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed moderately severe symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * One or more symptoms of grade ≥2 at a single time point (i.e., on any individual symptom card), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For symptom scoring measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboNumber of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection21 Participants
PlaceboNumber of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection7 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection25 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection3 Participants
p-value: 0.1477Fisher Exact
Secondary

Number of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the number of participants with qRT-PCR-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboNumber of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Symptomatic Influenza Infection19 Participants
PlaceboNumber of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Symptomatic Influenza Infection9 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Symptomatic Influenza Infection24 Participants
150 mg CD388Number of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Symptomatic Influenza Infection4 Participants
p-value: 0.1023Fisher Exact
Secondary

Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Events

Evaluation of the occurrence of solicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of inoculation with the influenza challenge virus, based on the number of events reported. Solicited AEs are those predefined events relating to reactogenicity (pain, tenderness, erythema/redness, induration/swelling) for which participants were specifically questioned and which were noted by participants in a participant diary.

Time frame: From Day -5 (dosing) up to Day 0 (viral challenge)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureValue (NUMBER)
PlaceboOccurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Events0 events
150 mg CD388Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Events0 events
150 mg CD388Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Events1 events
Secondary

Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Participants

Evaluation of the occurrence of solicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of inoculation with the influenza challenge virus, based on the number of participants reporting any solicited AE. Solicited AEs are those predefined events relating to reactogenicity (pain, tenderness, erythema/redness, induration/swelling) for which participants were specifically questioned and which were noted by participants in a participant diary.

Time frame: From Day -5 (dosing) up to Day 0 (viral challenge)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureValue (COUNT_OF_PARTICIPANTS)
PlaceboOccurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Participants0 Participants
150 mg CD388Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Participants0 Participants
150 mg CD388Occurrence of Solicited Adverse Events (AEs) From Subcutaneous (SQ) Dosing up to Viral Challenge - Number of Participants1 Participants
Secondary

Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of Events

Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 28 follow-up visit, based on the number of events reported. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 1 (from Day -5 dosing to just before challenge virus inoculation on Day 0) * Period 2 (from Day 0 challenge virus inoculation to actual discharge from the quarantine unit \[as scheduled on Day 8 or later at PI's decision\]) * Period 3 (from actual discharge from the quarantine unit to Day 28 (±3 days)

Time frame: From Day -5 (dosing) up to Day 28 (±3 days)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureGroupValue (NUMBER)
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 23 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 11 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 2 and 312 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 1 and 24 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 39 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 11 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 21 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 2 and 33 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 32 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 1 and 22 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 311 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 2 and 313 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 10 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriods 1 and 22 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of EventsPeriod 22 events
Secondary

Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of Participants

Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 28 follow-up visit, based on the number of participants for whom any AE is observed. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 1 (from Day -5 dosing to just before challenge virus inoculation on Day 0) * Period 2 (from Day 0 challenge virus inoculation to actual discharge from the quarantine unit \[as scheduled on Day 8 or later at PI's decision\]) * Period 3 (from actual discharge from the quarantine unit to Day 28 (±3 days)

Time frame: From Day -5 (dosing) up to Day 28 (±3 days)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 2 and 310 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 23 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 11 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 1 and 24 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 38 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 21 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 11 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 1 and 21 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 2 and 31 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 31 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 39 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 2 and 311 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 10 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriod 22 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to Day 28 Follow-up Visit - Number of ParticipantsPeriods 1 and 22 Participants
Secondary

Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of Events

Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 180 final follow-up visit, based on the number of events reported. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 3 (from actual discharge from the quarantine unit to Day 28 \[±3 days\]) * Period 4 (from Day 28\[±3 days\] to the final follow-up visit \[Day 180 ±14 days\]) * Across All Periods (from Day -5 dosing to the final follow-up visit \[Day 180 ±14 days\])

Time frame: From Day -5 (dosing) up to Day 180 (±14 days)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureGroupValue (NUMBER)
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 39 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriods 3 and 421 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 412 events
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsAcross All Periods25 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsAcross All Periods4 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 32 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 40 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriods 3 and 42 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsAcross All Periods34 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriods 3 and 432 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 421 events
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of EventsPeriod 311 events
Secondary

Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of Participants

Evaluation of the occurrence of unsolicited AEs in participants dosed with CD388, when compared with placebo, from the time of SQ dosing up to the time of the Day 180 final follow-up visit, based on the number of participants for whom any AE was observed. Unsolicited AEs are any AEs observed by the participant or Principal Investigator (PI)/investigator which are not prelisted on a symptom diary card. Results are categorized by period: * Period 3 (from actual discharge from the quarantine unit to Day 28 \[±3 days\]) * Period 4 (from Day 28\[±3 days\] to the final follow-up visit \[Day 180 ±14 days\]) * Across All Periods (from Day -5 dosing to the final follow-up visit \[Day 180 ±14 days\])

Time frame: From Day -5 (dosing) up to Day 180 (±14 days)

Population: The Safety Population included all participants who received at least 1 dose of study intervention. Participants were analyzed according to the study intervention they received.

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 38 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriods 3 and 416 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 49 Participants
PlaceboOccurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsAcross All Periods19 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsAcross All Periods1 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 31 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 40 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriods 3 and 41 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsAcross All Periods21 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriods 3 and 419 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 414 Participants
150 mg CD388Occurrence of Unsolicited AEs From SQ Dosing up to the Final Follow-up Visit - Number of ParticipantsPeriod 39 Participants
Secondary

Percentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with at least 1 positive quantitative (≥LLOQ) cell culture measurement in nasal samples starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (NUMBER)
PlaceboPercentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeAt Least 1 Positive Quantitative (≥LLOQ) Cell Culture39.3 percentage of participants
PlaceboPercentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeNo Positive Quantitative (≥LLOQ) Cell Culture60.7 percentage of participants
150 mg CD388Percentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeAt Least 1 Positive Quantitative (≥LLOQ) Cell Culture21.4 percentage of participants
150 mg CD388Percentage of Participants With at Least One Positive Quantitative (≥LLOQ) Cell Culture After Influenza Viral ChallengeNo Positive Quantitative (≥LLOQ) Cell Culture78.6 percentage of participants
Secondary

Percentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with culture laboratory-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * Lab-confirmed culturable influenza infection (1 quantifiable \[≥LLOQ\] cell culture measurement in nasal samples), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For viral culture measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (NUMBER)
PlaceboPercentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo Culture Lab-confirmed Symptomatic Influenza Infection71.4 percentage of participants
PlaceboPercentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeCulture Lab-confirmed Symptomatic Influenza Infection28.6 percentage of participants
150 mg CD388Percentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo Culture Lab-confirmed Symptomatic Influenza Infection85.7 percentage of participants
150 mg CD388Percentage of Participants With Culture Lab-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeCulture Lab-confirmed Symptomatic Influenza Infection14.3 percentage of participants
Secondary

Percentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed influenza infection, defined as 2 quantifiable (≥ lower limit of quantification \[LLOQ\]) qRT-PCR measurements (reported on 2 or more independent nasal samples over 2 days), starting 1 day post viral challenge.

Time frame: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (NUMBER)
PlaceboPercentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Influenza Infection50.0 percentage of participants
PlaceboPercentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Influenza Infection50.0 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Influenza Infection78.6 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Influenza Infection21.4 percentage of participants
Secondary

Percentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed moderately severe symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * One or more symptoms of grade ≥2 at a single time point (i.e., on any individual symptom card), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For symptom scoring measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (NUMBER)
PlaceboPercentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection75.0 percentage of participants
PlaceboPercentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection25.0 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection89.3 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Moderately Severe Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Moderately Severe Symptomatic Influenza Infection10.7 percentage of participants
Secondary

Percentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the percentage of participants with qRT-PCR-confirmed symptomatic influenza infection starting 1 day post viral challenge, defined as: * RT-PCR-confirmed influenza infection (2 quantifiable \[≥LLOQ\] qRT-PCR measurements \[reported on 2 or more independent nasal samples over 2 days\]), AND * TSS score ≥2 at any single time point (i.e., any individual symptom diary card for which the sum of symptom scores is ≥2; e.g., at a minimum, ≥1 symptom of grade ≥2, or ≥2 symptoms of grade ≥1), as measured by graded symptom scoring system (participant completed symptom diary card) collected 3 times daily.

Time frame: • For qRT-PCR measurements: Day 1 (pm); Days 2, 3, 4, 5, 6, and 7 (am and pm); Day 8 (am) • For TSS measurements: Three (3) times per day, at the same time each day (±1 hour), on Days 1, 2, 3, 4, 5, 6, and 7; and on Day 8 (am only)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint.

ArmMeasureGroupValue (NUMBER)
PlaceboPercentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Symptomatic Influenza Infection32.1 percentage of participants
PlaceboPercentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Symptomatic Influenza Infection67.9 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeNo qRT-PCR-confirmed Symptomatic Influenza Infection85.7 percentage of participants
150 mg CD388Percentage of Participants With qRT-PCR-Confirmed Symptomatic Influenza Infection After Influenza Viral ChallengeqRT-PCR-confirmed Symptomatic Influenza Infection14.3 percentage of participants
Secondary

Time to Confirmed Negative Test by qRT-PCR After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to confirmed negative test for influenza as determined by quantifiable qRT-PCR measurements in nasal samples starting 1 day post viral challenge.

Time frame: From Day 1 (pm) until the first confirmed undetectable assessment after peak measurement, assessed up to Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint. NOTE: Participants without a detectable qRT-PCR value were excluded from the analysis.

ArmMeasureGroupValue (NUMBER)
PlaceboTime to Confirmed Negative Test by qRT-PCR After Influenza Viral Challenge25th Percentile61.9 hours
PlaceboTime to Confirmed Negative Test by qRT-PCR After Influenza Viral ChallengeMedian134.1 hours
PlaceboTime to Confirmed Negative Test by qRT-PCR After Influenza Viral Challenge75th Percentile158.3 hours
150 mg CD388Time to Confirmed Negative Test by qRT-PCR After Influenza Viral Challenge25th Percentile66.7 hours
150 mg CD388Time to Confirmed Negative Test by qRT-PCR After Influenza Viral ChallengeMedian79.4 hours
150 mg CD388Time to Confirmed Negative Test by qRT-PCR After Influenza Viral Challenge75th Percentile131.7 hours
p-value: 0.0613Gehan-Wilcoxon
Secondary

Time to Confirmed Negative Test by Viral Culture After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to confirmed negative test for influenza as determined by quantifiable viral culture measurements in nasal samples starting 1 day post viral challenge.

Time frame: From Day 1 (pm) until the first confirmed undetectable assessment after peak measurement, assessed up to Day 8 (am)

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint. NOTE: Participants without a detectable viral culture value were excluded from the analysis.

ArmMeasureGroupValue (NUMBER)
PlaceboTime to Confirmed Negative Test by Viral Culture After Influenza Viral ChallengeMedian85.9 hours
PlaceboTime to Confirmed Negative Test by Viral Culture After Influenza Viral Challenge25th Percentile71.4 hours
PlaceboTime to Confirmed Negative Test by Viral Culture After Influenza Viral Challenge75th Percentile110.1 hours
150 mg CD388Time to Confirmed Negative Test by Viral Culture After Influenza Viral Challenge25th Percentile62.3 hours
150 mg CD388Time to Confirmed Negative Test by Viral Culture After Influenza Viral ChallengeMedian78.7 hours
150 mg CD388Time to Confirmed Negative Test by Viral Culture After Influenza Viral Challenge75th Percentile86.0 hours
p-value: 0.1282Gehan-Wilcoxon
Secondary

Time to Symptom Resolution After Influenza Viral Challenge

Evaluation of the effect of CD388, when compared to placebo, on the time (in hours, as estimated using the Kaplan-Meier method) to symptom resolution (i.e., first time with Total Symptom Score \[TSS\] equal to the TSS at baseline after which no further increase above the baseline TSS was observed) as measured by graded daily symptom scoring system (participant completed symptom diary card) collected 3 times daily starting 1 day post viral challenge. An individual TSS is derived at each assessment of the diary card as the sum of the scores given to the 13 symptoms on that symptom score card, resulting in possible TSS values from 0 to 39.

Time frame: Starting Day 1, from the time of peak daily symptom score until the time of returning to baseline score, up to Day 8

Population: The Per-Protocol Population included all randomized participants who received at least 1 dose of study intervention and were challenged with the study virus, and who have a valid result for at least 80% of the planned qRT-PCR nasal samples from Day 1 (pm) up to Day 8 (am) (i.e., at least 11 out of 14), and who present no major deviations likely to impact the evaluation of the primary efficacy endpoint. NOTE: Participants who only had a baseline TSS were excluded from the analysis.

ArmMeasureGroupValue (NUMBER)
PlaceboTime to Symptom Resolution After Influenza Viral Challenge75th Percentile78.7 hours
PlaceboTime to Symptom Resolution After Influenza Viral Challenge25th Percentile8.4 hours
PlaceboTime to Symptom Resolution After Influenza Viral ChallengeMedian41.5 hours
150 mg CD388Time to Symptom Resolution After Influenza Viral Challenge25th Percentile23.3 hours
150 mg CD388Time to Symptom Resolution After Influenza Viral ChallengeMedian74.8 hours
150 mg CD388Time to Symptom Resolution After Influenza Viral Challenge75th Percentile133.5 hours
p-value: 0.9024Gehan-Wilcoxon

Source: ClinicalTrials.gov · Data processed: Feb 7, 2026