NCT07300085

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

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

• Status: Active Not Recruiting
• Phase: Phase 1
• Study type: Interventional
• Enrollment: 100 (estimated)
• Sponsor: Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) · Industry
• Sex: All
• Age: 18 Years – 49 Years
• Healthy volunteers: Accepted

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.

Detailed description

This is a Phase 1, double-blind, randomized trial to evaluate the immunogenicity of Fluzone® HD influenza vaccine when concomitantly administered with either CD388 or placebo, in healthy participants. This study will also evaluate the safety and tolerability of CD388 when administered with Fluzone HD compared to Fluzone HD with placebo. The pharmacokinetics (PK) of CD388 in plasma when administered concomitantly with Fluzone HD vaccine will also be evaluated.

Conditions

• Healthy Participants

Interventions

Type	Name	Description
BIOLOGICAL	Fluzone HD influenza vaccine	Fluzone HD injectable suspension, 2025-2026 Formula
COMBINATION_PRODUCT	CD388 Injection	CD388 liquid for injection
COMBINATION_PRODUCT	Placebo	Placebo to match

Timeline

• Start date: 2025-11-08
• Primary completion: 2026-12-01
• Completion: 2026-12-01
• First posted: 2025-12-23
• Last updated: 2026-03-24

Locations

2 sites across 1 country: United States

Regulatory

• FDA-regulated drug study