NCT07110532

pH1N1 Blinded Challenge Study

A Double-Blinded, Randomized Influenza Virus Challenge Trial of Recombinant Influenza RG-A/Arkansas/08/2020 (pH1N1) in Healthy Adults to Assess Safety and Optimal Infectious Dose

• Status: Recruiting
• Phase: Phase 1
• Study type: Interventional
• Enrollment: 90 (estimated)
• Sponsor: National Institute of Allergy and Infectious Diseases (NIAID) · NIH
• Sex: All
• Age: 18 Years – 55 Years
• Healthy volunteers: Accepted

Summary

This protocol describes a clinical trial to develop and validate a Controlled Human Infection Model (CHIM) for influenza A/Arkansas/08/2020 (pH1N1). The study is designed to determine the optimal infectious dose of the pH1N1 challenge strain for use in future clinical trials evaluating influenza countermeasures. The study will enroll and challenge adult volunteers with the pH1N1 influenza virus challenge or sham inoculations. Given the adaptive design of this trial, the potential number of participants can vary. Depending on the pathway recommended by the PSRT and followed in the Trial Schema, the study population can range from around 30 to 99. The anticipated final sample size will be approximately 90 receiving pH1N1 challenge product plus and 6 persons receiving a sham inoculation. Participants will be pre-screened for health and for serological HAI antibody titers of \</1:40 against the challenge strain. Eligible participants will be enrolled sequentially into challenge cohorts and will be randomly assigned to receive a single dose of either sham inoculation or the interventional study product at a dose between 10\^6 to 10\^7 TCID50 (or 10\^5 TCID50 if needed). Dose titration will be conducted under an adaptive escalation schedule whereby dosing will start at 10\^6 TCID50 and escalate to the next dose if a pre-determined symptomatic influenza attack rate and clinical symptom score thresholds are not met and if the dose is determined to be safe with no pre-defined halting criteria being met. The primary objectives of this study are to determine the optimal infectious dose of a pH1N1 viral challenge to cause laboratory-confirmed clinical influenza and to assess the safety profile of pH1N1 viral challenge.

Detailed description

This protocol describes a clinical trial to develop and validate a Controlled Human Infection Model (CHIM) for influenza A/Arkansas/08/2020 (pH1N1). The study is designed to determine the optimal infectious dose of the pH1N1 challenge strain for use in future clinical trials evaluating influenza countermeasures. The study will enroll and challenge adult volunteers with the pH1N1 influenza virus challenge or sham inoculations. Given the adaptive design of this trial, the potential number of participants can vary. Depending on the pathway recommended by the PSRT and followed in the Trial Schema, the study population can range from around 30 to 99. The anticipated final sample size will be approximately 90 participants receiving pH1N1 challenge product and 6 persons receiving a sham inoculation. Participants will be pre-screened for health and for serological HAI antibody titers of \</=1:40 against the challenge strain. Eligible participants will be enrolled sequentially into challenge cohorts and will be randomly assigned to receive a single dose of either sham inoculation or the interventional study product at a dose between 10\^6 to 10\^7 TCID50 (or 10\^5 TCID50 if needed). Dose titration will be conducted under an adaptive escalation schedule whereby dosing will start at 10\^6 TCID50 and escalate to the next dose if a pre-determined symptomatic influenza attack rate and clinical symptom score thresholds are not met and if the dose is determined to be safe with no pre-defined halting criteria being met. The primary objectives of this study are to determine the optimal infectious dose of a pH1N1 viral challenge to cause laboratory-confirmed clinical influenza and to assess the safety profile of pH1N1 viral challenge. The secondary objectives are to describe clinical symptoms following pH1N1 viral challenge, to describe viral detection by qualitative reverse transcription polymerase chain reaction (RT-PCR) and to describe the host serum influenza hemagglutination inhibition and microneutralization antibody responses.

Conditions

• Influenza

Interventions

Type	Name	Description
BIOLOGICAL	A/Arkansas/08/2020 (pH1N1)	GMP-grade, cell-based influenza A (pH1N1) virus (Lot #24-005), derived via reverse genetics for use in controlled human infection studies.
OTHER	Sham/Diluent (1X SPG+Arg+Gel)	Sterile diluent containing 1X Sucrose Phosphate Glutamate (SPG), 1% arginine, and 1% hydrolyzed gelatin, used as a sham comparator in the human challenge trial.

Timeline

• Start date: 2025-09-10
• Primary completion: 2026-06-23
• Completion: 2026-08-18
• First posted: 2025-08-07
• Last updated: 2026-04-08

Locations

2 sites across 1 country: United States

Regulatory

• FDA-regulated drug study