Icosavax Preps IND Application for RSV Vaccine Following Positive Data

respiratory infection

Icosavax posted positive topline interim data from the Phase I/Ib trial of IVX-121, its virus-like particle (VLP) vaccine candidate that targets the respiratory syncytial virus in adults.

Results from Phase I of Icosavax's randomized, placebo-controlled study were based on observations of 90 healthy young adults ages 18 to 45 years old, while Phase Ib included 130 healthy older adults 60 to 75 years old. Participants were given either a placebo or a single dose of IVX-121 at one of three dosage levels (25, 75 and 250 µg), with or without an aluminum hydroxide adjuvant.

At 28 days after receiving the vaccine, researchers monitored for immunogenicity and safety by measuring neutralizing antibodies (nAbs) to RSV-A and RSV-B using the World Health Organization's international reference standard. Among the younger group, IVX-121 induced geometric mean titers (GMTs) in RSV-A nAbs of up to 7,687 IU/mL versus only 1,100 IU/mL in the placebo users. In the older group, the vaccine induced up to 7,561 IU/mL of GMTs in RSV-A nAbs compared to the placebo group's 1,692 IU/mL.

While the scientists found some local and systemic adverse events, these were mild or moderate, including headache, injection site tenderness and fatigue. There were no serious adverse events logged. Regarding immunogenicity, the vaccine candidate created a strong immune response in both age groups. The aluminum hydroxide adjuvant did not appear to add any benefit at any dose level.

"These data are particularly encouraging for the vulnerable older adult population with co-morbidities and increased risk for severe disease and hospitalization," Niranjan Kanesa-thasan, M.D., CMO of Icosavax said. The immunogenicity of IVX-121, even at very low microgram dosage levels, and its favorable tolerability to the highest dose level, makes it well suited to a combination vaccine approach." 

The purpose of the trial is to determine the right dose level that will be assessed in combination with Icosavax's hMPV VLP in another Phase I trial. The results will also be used to support a Phase Ib extension trial where eligible older adults from Phase Ib will be observed for up to 12 months to evaluate the durability of response.

Icosavax is also preparing to submit an Investigational New Drug application for IVX-A12 to the U.S. Food and Drug Administration. 

"As planned, Icosavax will now progress development of IVX-121 combined with a human metapneumovirus (hMPV) VLP, as our IVX-A12 bivalent vaccine candidate. We believe IVX-A12 could be unique in providing protection against these two leading causes of pneumonia, each of which currently lack an approved vaccine," Icosavax CEO Adam Simpson said in the same announcement.

Back to news