Clinical trial Recruiting at 2 sites Phase 1 Interventional Ages 18 to 49

MK-1406 with Fluzone High-Dose vaccine in healthy adults

Official title: A Phase 1, Double-blind, Randomized Trial to Evaluate Safety and Immunogenicity of Fluzone® High-Dose Influenza Vaccine When Concomitantly Administered With CD388, a Novel Long-Acting Antiviral Conjugate for the Prevention of Influenza

Run by Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) · NCT07300085 · Data updated 2026-11-12

This early study tests whether MK-1406 can be safely given with Fluzone HD and whether it changes the vaccine’s immune response in healthy adults 18–49.

More Healthy Adult Participants trials

Quick facts

PhasePhase 1
Study typeInterventional
Ages18 Years to 49 Years
SexAll
Enrollment710 (estimated)
SponsorCidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)
Industry-sponsored
Locations2 sites (Glendale, California and 1 other locations)
StatusRecruiting
StartedNovember 8, 2025
Main results expectedDecember 31, 2026
Study endsDecember 31, 2026
Registry record updatedNovember 4, 2026
Trial IDNCT07300085 on ClinicalTrials.gov

Is this trial a fit for you?

Likely a good fit

Healthy adults aged 18–49 who have not had a recent flu vaccine or influenza infection and who meet study health criteria.

Probably not a fit

Those who do not respond to MK-1406 or who experience safety issues may not benefit.

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is a Phase 1, double-blind, randomized trial to see if MK-1406 affects the immune response to Fluzone High-Dose vaccine and to assess safety when given together in healthy participants. Participants are randomly assigned to receive MK-1406 or placebo with Fluzone HD, and both groups are monitored for immune responses and adverse events. The study will measure immunogenicity outcomes and safety/tolerability across a controlled, closely supervised setting. Eligible participants are adults 18–49 who are generally healthy and have not recently received a seasonal flu vaccine or had influenza. The trial is conducted at two sites in the United States and led by Cidara Therapeutics in collaboration with Merck & Co.

Why it matters

Potential benefit: If successful, the combination could inform strategies to improve flu vaccine protection.

How similar studies have gone: Previous similar approaches in early-stage trials have explored combining antivirals or adjuvants with vaccines, with mixed but informative results.

Who can join: the full rules

Show full inclusion / exclusion criteria
Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

* Be ≥18 to ≤49 years of age
* Be deemed healthy by the Investigator
* 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

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

* Had an active malignancy within 5 years prior to screening, except basal cell or squamous cell skin cancer. Any history of breast cancer or melanoma is exclusionary.
* Has previously been diagnosed with Guillain-Barre Syndrome following a previous influenza vaccination.

Where it's running

  • Parexel ( Site 0001)
    Glendale, California, United States
    Recruiting
  • Parexel ( Site 0002)
    Baltimore, Maryland, United States
    Recruiting

Study contacts

Similar studies

Other studies for the same condition or treatment. Recruiting studies are listed first.

How to take part

  1. Review the eligibility criteria above with your treating physician.
  2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
  3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.
Last reviewed 2026-11-14 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.