A Trial to Evaluate the Effect of CD388 on the Immunogenicity of Fluzone® HD Vaccine

NCT07300085 | Active Not Recruiting Phase 1 FDA Drug

• 1 other identifier: CD388.SQ.1.08
• Study Type: interventional
• Target: 100
• Locations: 1 country
• Sites: 2

Brief Summary

The goal of this clinical study is to investigate how safe and effective it is to receive both the Fluzone® High-Dose (HD) influenza vaccine and CD388, a long-acting antiviral medicine, at the same time. Some participants will receive the vaccine and CD388, while others will receive the vaccine and a placebo. The study aims to determine whether taking CD388 together with the flu vaccine affects the body's ability to build protection-called an immune response-against the flu, as compared to getting the vaccine with a placebo. The hypothesis is that giving both at the same time does not weaken the immune response to the vaccine. The study will measure the amount of antibodies (proteins produced by the immune system to fight flu viruses) generated by participants in both groups to check that CD388 does not interfere with how well the vaccine works. Participants will also be closely watched for any side effects or reactions to check that CD388 is safe to take alongside the vaccine. Expanded access to the study treatments (flu vaccine and CD388) will not be provided to participants after the study ends.

Conditions

Healthy Participants

Keywords

Influenza; Antiviral Agents

Outcome Measures

Primary Outcomes (1)

• Immune Responses in Participants Receiving Concomitant Fluzone HD and CD388 Compared to Participants Who Receive Fluzone HD and Placebo

  Evaluation of immune responses at 2- and 4-weeks post intervention measured by hemagglutinin inhibition (HAI) titers (geometric mean titers \[GMTs\] and seroconversion rates) against the influenza strains contained in the vaccine among participants receiving concomitant Fluzone HD influenza vaccine and CD388 compared to participants who receive Fluzone HD and placebo for CD388.

  On Day 1 (pre-intervention baseline), Day 15 (±1 day), and Day 29/End of Trial (EOT) (±2 days)

Secondary Outcomes (1)

• Incidence and Severity of Treatment-Emergent Adverse Events (TEAEs) in Participants Receiving Concomitant Fluzone HD and CD388 Compared to Participants Who Receive Fluzone HD and Placebo

  From Day 1 through Day 29/EOT after concomitant intervention administration

Study Arms (2)

Fluzone HD plus CD388

EXPERIMENTAL

Participants will be randomized to receive open-label Fluzone HD influenza vaccine by intramuscular (IM) injection plus CD388 450 milligrams (mg) by subcutaneous (SQ) injection. Participants will be randomized at a 1:1 ratio between the 2 arms.

Biological: Fluzone HD influenza vaccine; Combination Product: CD388 Injection

Fluzone HD plus Placebo

PLACEBO COMPARATOR

Participants will be randomized to receive open-label Fluzone HD influenza vaccine by IM injection plus placebo by SQ injection. Participants will be randomized at a 1:1 ratio between the 2 arms.

Biological: Fluzone HD influenza vaccine; Combination Product: Placebo

Interventions

Fluzone HD influenza vaccine BIOLOGICAL

Fluzone HD injectable suspension, 2025-2026 Formula

Fluzone HD plus CD388; Fluzone HD plus Placebo

CD388 Injection COMBINATION_PRODUCT

CD388 liquid for injection

Fluzone HD plus CD388

Placebo COMBINATION_PRODUCT

Placebo to match

Fluzone HD plus Placebo

Eligibility Criteria

• Age: 18 Years - 49 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Be ≥ 18 to ≤ 49 years of age at the time of signing the informed consent.
• Be able to understand and comply with the trial procedures, understand the risks involved in the trial, and provide written informed consent before the first trial-specific procedure.
• Be deemed healthy by the Investigator, as determined via medical history and clinical examination before enrolling in the trial.
• Be able to complete all screening period evaluations and attend the required follow-up visits at the site.
• Have not received any seasonal influenza vaccine and have not had a diagnosed or suspected influenza infection within 12 months prior to Day 1 of the trial, based on participant self-report.
• Have a body mass index (BMI; calculated as weight in kilograms \[kg\] divided by height in meters \[m\] squared)) between 18 and 32 kg/m\^2, inclusive, and body weight not less than 50 kg at screening.
• Have resting vital signs at screening within the following ranges:
• Systolic blood pressure ≥100 millimeters of mercury (mmHg)
• Diastolic blood pressure ≥50 mmHg
• Heart rate (HR) ≤100 beats per minute Note: If vital signs are outside of the above ranges, the Investigator may obtain up to two additional readings within the screening period.
• Have a 12-lead electrocardiogram (ECG) consistent with normal cardiac conduction and function at screening, including: HR between 45 and 100 bpm (inclusive); QT interval corrected using Fridericia's formula (QTcF) ≤ 450 milliseconds (ms) for males and ≤ 470 ms for females; QRS interval \<120 ms; PR interval \<220 ms; and morphology consistent with healthy cardiac conduction.
• Be a nonsmoker within the previous 6 months before screening, and does not use tobacco-containing, or nicotine-containing products, including, but not limited to, cigarettes, pipes, cigars, chewing tobacco, e-cigarettes, nicotine patch, or nicotine gum.
• Be willing to abstain from alcohol, recreational drugs, and tobacco-containing and nicotine-containing products throughout their participation in the trial.
• Have clinical chemistry, hematology, and complete urinalysis results at screening within the reference range for the testing laboratory unless the out-of-range results are deemed not clinically significant by the Investigator.
• Be seronegative for hepatitis B surface antigen (HbsAg), hepatitis C virus antibody (HCV Ab), and human immunodeficiency virus (HIV) antibody at screening.

You may not qualify if:

• Has a condition that the Investigator believes would interfere with the participant's ability to provide written informed consent, comply with trial instructions, or which might confound the interpretation of the trial results or put the participant at undue risk.
• Have a current or past history of a clinically significant cardiovascular, cerebrovascular, respiratory, gastrointestinal, hematologic, renal, hepatic, immunologic, metabolic, urologic, neurologic, dermatologic, psychiatric, or other major disease, as determined by the Investigator.
• Have a history of any drug abuse within 1 year prior to screening or has used any hard drugs (such as cocaine, phencyclidine \[PCP\], natural and synthetic opiates, and amphetamine derivatives) within 1 year prior to screening. Individuals that have taken an opioid or amphetamine medication within the previous year prior to screening that was prescribed by a healthcare provider will not be excluded unless they are currently taking the medication at the time of screening.
• Have a history of regular alcohol consumption exceeding 14 drinks/week (1 drink equals 5 ounces \[150 milliliters {mL}\] of wine or 12 ounces \[360 mL\] of beer or 1.5 ounces \[45 mL\] of hard liquor) within 6 months of screening or alcohol abuse within 1 year prior to screening.
• Are taking or have received any of the following:
• Immune Serum Globulin (6 weeks): Has received any immune serum globulin or blood-derived products within 6 weeks prior to Day 1.
• Immunosuppressive/Immunomodulatory Therapy (6 weeks): Any systemic corticosteroid therapy (oral or parenteral, equivalent to ≥10 mg/day prednisone for more than 14 consecutive days) or any other immunosuppressive or immunomodulatory agent within 6 weeks prior to Day 1. NOTE: Topical, inhaled, or intranasal corticosteroids at low- to moderate-dose regimens are permitted if not intended for immune suppression and at stable doses for ≥30 days before Day 1.
• Have a contraindication to Fluzone HD or CD388 or any of the excipients and/or history of a clinically significant allergic or anaphylactic reaction to any medication or following influenza vaccination.
• Has previously been diagnosed with Guillain-Barre Syndrome following a previous influenza vaccination.
• Have previously participated in a clinical trial in which CD388 was a trial intervention.
• Has participated in other trials involving administration of an investigational drug or device within 30 days or 5 half-lives, whichever is longer, before screening for the current trial and during participation in the current trial.
• Has a positive rapid antigen test result for either Coronavirus disease 2019 (COVID-19)/severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or for influenza at Pre-Dose Day 1.
• Has donated ≥450 mL of blood (1 unit) within 2 months before entering the trial or planning to donate blood during the trial or within 36 weeks after the final visit.
• Have a known or suspected allergy or history of anaphylaxis to zanamivir (following administration of inhaled or intravenous formulations), monoclonal antibodies (including Fc domains), or any of the components of CD388.
• Had major surgery (e.g., cardiac, pulmonary, neurologic, or abdominal operations) within 4 weeks prior to screening, or will not have fully recovered from such prior surgery; or has major surgery planned during the time the participant is expected to participate in this trial.

Sponsors & Collaborators

• Cidara Therapeutics Inc.: lead

Study Sites (2)

California Clinical Trials Medical Group (CCTMG) managed by Parexel

Glendale, California, 91206, United States

Location

Parexel International - EPCU Baltimore

Baltimore, Maryland, 21225, United States

Location

MeSH Terms

Conditions

Influenza, Human

Condition Hierarchy (Ancestors)

Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases

Study Officials

• Nicole Davarpanah, MD, JD

  Cidara Therapeutics Inc.

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: December 10, 2025
• First Posted: December 23, 2025
• Study Start: November 8, 2025
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026
• Last Updated: March 24, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

US (2)