Novavax, Inc. today announced follow-up data from its dose-ranging Phase 1 clinical trial of its respiratory syncytial virus (RSV) F-protein vaccine in 220 elderly adults (60 years of age and older, with a mean age of 68) that was initiated in October 2012.
In the placebo-controlled trial, subjects received a single injection of either 60µg or 90µg of the RSV F-protein vaccine candidate, with or without aluminum phosphate as an adjuvant.
Positive top-line interim safety and immunogenicity data released by Novavax in July 2013 described antibody responses 28 and 56 days post-immunization. Overall immune responses were greater in groups receiving the 90μg dose compared to the groups dosed with 60µg. Also, robust anti-F IgG responses and palivizumab competing antibody (PCA) responses were observed in all vaccine recipients. Notably, by day 56, subjects receiving the 90μg dose without adjuvant achieved PCA responses at a geometric mean of 142μg/ml, which approximate the peak levels seen in pharmacokinetics trials of palivizumab in infants receiving repeat palivizumab injections (~150µg/ml) and exceeded trough levels seen (~70µg/ml) in those same studies, indicating that the vaccine induced antibody levels that are likely to be protective.
In the one-year follow up data released by Novavax today, the company reported that the group receiving the 90μg dose without adjuvant, anti-F levels and PCA were significantly elevated over baseline at day 118, with a geometric mean of 130μg/ml, and at day 180, with a geometric mean of 114μg/ml. For the same group, at day 180, anti RSV A neutralizing antibodies were log2 8.8 and RSV B neutralizing antibodies were log2 9.0, both considered protective levels in seroepidemiology studies.
"Typically, RSV season lasts four to five months, so it was important to see follow-up data which support that our vaccine could be protective across a full RSV season, similar to seasonal influenza vaccination. Our data suggest that, since protective levels are diminished at day 365, annual boosts of our vaccine may be warranted," said Dr. Gregory Glenn, Senior Vice President of Research and Development at Novavax. "The monoclonal antibody palivizumab has been shown to protect infants against severe RSV disease but has only a 21-day half-life and is therefore given in multiple injections to sustain protective levels. A single dose of our RSV F vaccine candidate appears to sustain immunity in the elderly at levels that exceed what was protective in infants, and does so over a long-enough period of time to cover an entire RSV season."
Stan Erck, President and CEO of Novavax, stated, "We were pleased to see that a 90μg dose of our RSV F vaccine candidate was immunogenic and sustained levels that appear to be protective over an entire RSV season. These results encourage us to accelerate our development plans to include an annual seasonal RSV vaccine for the elderly where there is a burden of disease and incidence rate similar to that of an influenza virus, and clearly support initiation of a Phase 2 clinical trial as early as later this year or early-2015.
RSV is a major respiratory pathogen in infants, children, and adults. RSV infections in adults represent re-infections and are generally mild to moderate in severity, except in persons with high-risk conditions including the elderly and adults with underlying chronic cardiac or pulmonary disease. It is estimated that between 11-17,000 adults die of RSV infection annually in the U.S., with and up to 180,000 admitted to hospital with respiratory symptoms. Currently, there is no approved RSV prophylactic vaccine available. Palivizumab is a monoclonal antibody, licensed and sold by Medimmune as Synagis®, that targets the RSV F protein and is used for prophylaxis against RSV disease in high risk infants.
Novavax, Inc. (Nasdaq:NVAX) is a clinical-stage biopharmaceutical company creating novel vaccines and vaccine adjuvants to address a broad range of infectious diseases worldwide. Using innovative proprietary recombinant protein nanoparticle vaccine technology, the company produces vaccine candidates to efficiently and effectively respond to both known and newly emergent diseases. Additional information about Novavax is available on the company's website, novavax.com.