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.
Quick facts
| Phase | Phase 1 |
|---|---|
| Study type | Interventional |
| Ages | 18 Years to 49 Years |
| Sex | All |
| Enrollment | 710 (estimated) |
| Sponsor | Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) Industry-sponsored |
| Locations | 2 sites (Glendale, California and 1 other locations) |
| Status | Recruiting |
| Started | November 8, 2025 |
| Main results expected | December 31, 2026 |
| Study ends | December 31, 2026 |
| Registry record updated | November 4, 2026 |
| Trial ID | NCT07300085 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
- Study coordinator: Toll Free Number
- Email: Trialsites@msd.com
- Phone: 1-888-577-8839
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.