Novavax Offers Top-Line Results from Phase 2 Trial of RSV Vaccine Candidate, Says Safety Will Be Evaluated Over Total Six Months

Novavax, Inc.

today announced that top-line data from the Phase II dose-ranging clinical trial of its respiratory syncytial virus (RSV) vaccine candidate in women of childbearing age accomplished the trial's protocol-specified objectives and supports progression to the next stage of advanced clinical testing. The trial represents an important step towards establishing the safety and immunogenicity of the vaccine candidate for use in a maternal immunization strategy. In such a strategy, the antibodies in vaccinated women can be expected to be naturally transferred to their infants in utero and thereby may confer passive protection at the earliest stage of life when these infants are extremely vulnerable to severe respiratory disease due to RSV. This randomized, blinded, placebo-controlled Phase II clinical trial evaluated the safety and immunogenicity of two-dose levels of Novavax' RSV F protein nanoparticle vaccine candidate with and without aluminum phosphate (alum) as an adjuvant. The study enrolled 330 women of childbearing age who received either one or two intramuscular injections of a single-dose of vaccine or placebo, at study day 0 and day 28. Doses of 60 and 90 µg were tested, either with or without alum as an adjuvant. Safety and immunogenicity data for this clinical trial have been evaluated through day 56. Safety will continue to be evaluated over a total period of six months and immunogenicity for four months for each participant. The clinical trial is being conducted in collaboration with PATH, an international nonprofit organization that transforms global health through innovation. PATH committed funding of approximately $2 million to support this trial with the aim of advancing the development of an RSV vaccine to protect infants through maternal immunization in low-resource countries. In this trial, the vaccine candidate was generally well-tolerated and the safety profile was similar to that observed previously in the Phase I clinical trial. The principal observation was transient mild to moderate injection site pain, predictably somewhat more frequent in the adjuvanted vaccine recipients. There were no clinically important differences in systemic adverse events between placebo and active vaccine recipients and no vaccine related SAEs. The most commonly reported systemic reactogenicity was comprised mainly of mild to moderate headache, fatigue and muscle ache, which are frequently noted after treatment by many vaccines. There were no differences in safety assessments across doses (60 and 90 µg) or worsening of reactogenicity with a second-dose. Laboratory testing did not reveal clinically significant changes in normal blood chemistries or hematology parameters. The primary objectives of the study measured the difference in anti-F IgG elicited by the use of alum adjuvant, one versus two immunizations, and across doses (60 and 90 µg). The use of alum enhanced both the single and two-dose regimen anti-F IgG responses, with the greatest responses observed using a two-dose regimen. Peak geometric mean titers of anti-F IgG in the two-dose alum groups ranged from 12,000-14,000 representing a 13 to 16-fold rise, compared to a 6 to 10-fold rise in the non-alum groups. Minimal increases were observed by increasing the doses (60 to 90 µg). Peak geometric mean RSV A neutralizing antibodies in the alum groups ranged from log[2] 9.5-10.5, representing a 3.1 to 3.8-fold rise. Palivizumab-like antibody titers rose 8 to 9-fold, with four-fold rises in ≥92% of vaccinees in the two-dose alum adjuvanted vaccine groups. Overall, the immune responses observed in this Phase II clinical trial were similar to, or exceeded immune responses seen in the Phase I clinical trial using the Novavax nanoparticle vaccine.