Active — Not RecruitingPhase 1

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

United States100 participantsStarted 2025-11-08

Plain-language 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.

Who can participate

Age range18 Years – 49 Years

SexALL

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Inclusion criteria

✓. 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)

Exclusion criteria

What they're measuring

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

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

Trial details

NCT IDNCT07300085

SponsorCidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)

Sponsor typeINDUSTRY

Study typeINTERVENTIONAL

Primary completion2026-12

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