A Trial to Evaluate the Effect of CD388/MK1406 on the Immunogenicity of Fluzone® HD Vaccine (CD388.SQ.1.08/MK-1406-007)

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

Status and phase: Active, not recruiting; Phase 1

Conditions: Healthy Participants

Treatments: Combination Product: Placebo; Combination Product: MK-1406 Injection; Biological: Fluzone® High-Dose (HD) influenza vaccine

Study type: Interventional

Funder types: Industry

Identifiers

NCT07300085

CD388.SQ.1.08

MK-1406-007 (Other Identifier)

Details and patient eligibility

About

Approximately one billion cases of seasonal influenza occur annually. Of these, 3 to 5 million illnesses are severe and responsible for up to 650,000 deaths per year (WHO 2025). Yearly administration of an influenza vaccine for the prevention of influenza is currently recommended. However, the real-world vaccine effectiveness varied from 10% to 60% in the general population across the years of 2004 to 2024, with effectiveness in most years below 50% (CDC 2025) and decreasing to as low as 5% in immunocompromised individuals (Hughes 2021). Researchers are looking for other ways to prevent severe illness from the influenza virus.

The goals of this study are to learn if:

• MK-1406 (formerly CD388) is safe to take with Fluzone®
• MK-1406 affects the immune response to Fluzone®

Full description

This is a Phase 1, double-blind, randomized trial to evaluate the immunogenicity of Fluzone® HD influenza vaccine when concomitantly administered with either MK-1406 or placebo, in healthy participants. This study will also evaluate the safety and tolerability of MK-1406 when administered with Fluzone® High-Dose (HD) compared to Fluzone® HD with placebo.

Enrollment: 710 estimated patients

Sex: All

Ages: 18 to 49 years old

Volunteers: Accepts Healthy Volunteers

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.

Trial design

Primary purpose: Prevention

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Quadruple Blind

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710 participants in 2 patient groups, including a placebo group

Fluzone® High-Dose (HD) plus MK-1406

Experimental group

Description:

Participants will receive open-label Fluzone® HD influenza vaccine by intramuscular (IM) injection plus MK-1406 by subcutaneous (SC) injection on Day 1.

Treatment:

Biological: Fluzone® High-Dose (HD) influenza vaccine

Combination Product: MK-1406 Injection

Fluzone® HD plus Placebo

Placebo Comparator group

Description:

Participants will receive open-label Fluzone® HD influenza vaccine by IM injection plus placebo by SC injection on Day 1.

Treatment:

Biological: Fluzone® High-Dose (HD) influenza vaccine

Combination Product: Placebo