ENA Respiratory has begun dosing participants in Part B of a Phase 2a study testing its once-weekly nasal spray INNA-051 against symptomatic respiratory viral infections.

Part B expands respiratory infection study

The POSITS study is evaluating the safety, tolerability and efficacy of INNA-051 in adults at increased risk of respiratory viral infections because of their living or working environments.

Part B will recruit up to 900 participants in the US during the North American respiratory virus season. Participants will receive weekly INNA-051 or placebo for three months across five clinical sites.

The study is targeting people living in severely crowded households, university housing residents, military personnel living in barracks, childcare centre workers and people living with or caring for children aged 10 or younger who attend school or day care.

The trial’s primary purpose is to assess whether INNA-051 can affect the incidence, duration and severity of symptomatic infections caused by common respiratory viruses.

The study includes participants aged 18 to 45 who are generally healthy but considered at increased risk of respiratory viral infection.

Nasal treatment targets antiviral defences

INNA-051 is a once-weekly dry powder nasal spray designed to activate innate antiviral defences in the nose.

The treatment is a TLR2/6 agonist intended to stimulate local host defence pathways before or during exposure to respiratory viruses. Viruses being monitored in the study include influenza, respiratory syncytial virus (RSV), rhinovirus and coronaviruses.

The approach differs from virus-specific vaccines and direct-acting antiviral medicines by targeting the body’s innate immune response rather than a particular virus.

ENA Respiratory completed Part A of the POSITS study in May, with 200 participants receiving four weeks of weekly dosing. The company reported that no safety concerns were identified and that a safety review committee supported progression to the larger Part B study.

Ruth Tal-Singer, consultant medicine development lead at ENA Respiratory, said: “The start of large Part B of our study is another important milestone in the development of INNA-051.”

She added: “By boosting the body’s natural host defence pathways, we believe INNA-051 could offer new hope to millions of vulnerable patients worldwide and we look forward to adding to the clinical evidence of its potential through this study.”

Study will assess symptomatic infections

The POSITS study will measure whether three months of weekly treatment affects the number of symptomatic respiratory infections experienced by participants.

Secondary assessments include the duration and severity of infections, as well as safety and tolerability.

The first stage of the trial was designed primarily around safety, while the larger Part B is intended to provide more information about whether INNA-051 has an effect on respiratory infections in a community setting.

The trial is being conducted at five US sites, including the Center for Vaccine Development and Global Health at the University of Maryland, Baltimore and the Naval Medical Research Command Clinical Trials Center in Bethesda, Maryland. Three additional sites are located in North Carolina.

The study is expected to continue through the 2026-27 respiratory virus season, with the overall trial currently listed as ongoing and an estimated completion date of March 2027.

No efficacy results from Part B are currently available. The study will therefore need to establish whether activating local innate immune defences can reduce symptomatic respiratory infections in people with increased exposure risk.