ENA Respiratory begins Part B dosing in INNA-051 Phase IIa study

ENA Respiratory has dosed the first participants in Part B of its Phase IIa POSITS study (NCT07222670), evaluating its once-weekly dry powder nasal spray INNA-051 in young adults at elevated risk of respiratory viral illness. The Part B cohort will recruit up to 900 participants across five sites in the United States over the current North American respiratory virus season, with each participant dosed for up to three months.

Part A of the study, which enrolled 200 participants over four weeks of weekly dosing, was completed in May with no safety concerns identified. The transition to Part B represents a substantial scale-up in both participant numbers and dosing duration, and will generate data on the incidence, duration and severity of symptomatic infections caused by common respiratory viruses including rhinovirus, influenza, RSV and coronaviruses.

Study design and target populations

Recruitment is targeting individuals in crowded living or working environments: university housing residents, military personnel in barracks, childcare workers, and those living with or caring for school-age children. Sites include the Center for Vaccine Development and Global Health at the University of Maryland Baltimore, the Naval Medical Research Command Clinical Trials Center in Bethesda, Maryland, and three Accellacare sites in North Carolina.

INNA-051 is designed to prime innate antiviral host defences in the nasal mucosa, the primary entry point for common respiratory viruses. Because the mechanism targets the host rather than a specific pathogen, ENA positions the candidate as virus-agnostic, a distinction the company argues is relevant in settings where vaccine coverage is incomplete or where novel variants emerge faster than strain-matched vaccines can be deployed.

Ruth Tal-Singer, ENA Respiratory's Consultant Medicine Development Lead, said the start of Part B was "another important milestone" and that complications from respiratory viral infections "continue to place a huge burden on patients and healthcare systems globally."

Market context and competitive landscape

The innate immunity space for respiratory protection is less crowded than the direct-acting antiviral or mRNA vaccine markets, but it is attracting growing interest following the limitations exposed by SARS-CoV-2 and successive influenza seasons. A number of academic groups and early-stage companies are investigating toll-like receptor agonists, mucosal adjuvants and other host-directed approaches, though few have reached Phase II community studies of this scale in the general-risk population.

ENA's investor base includes the Gates Foundation, the Minderoo Foundation and Flu Lab, alongside venture capital from Brandon Capital, Stoic Venture Capital and Uniseed. The company has also secured funding from the US Government and two Australian government-backed programmes, a mixed public-private structure common to pandemic-preparedness-adjacent assets. A separate Phase I study in asthma patients is planned in Australia, which would extend the programme into a higher-risk chronic-disease population if current safety and efficacy signals hold.

Topline results from Part B are not expected until after the Northern Hemisphere respiratory season concludes, likely in early-to-mid 2027. Whether the study can demonstrate a measurable reduction in symptomatic infection burden in a community setting will be closely watched by both investors and the broader host-directed therapeutics field.