Late-stage study of Novavax's respiratory syncytial virus vaccine ResVax fails to hit main goal

Novavax announced Thursday that a Phase III study of ResVax, an aluminium adjuvanted respiratory syncytial virus (RSV) fusion protein recombinant nanoparticle vaccine, failed to meet its primary endpoint. The trial, dubbed Prepare, investigated the ability of ResVax to protect infants via maternal immunisation against RSV disease. Shares in the company fell nearly 70 percent on the news.

The study enrolled 4636 pregnant women, at least 3000 of whom received ResVax, and their infants. Top-line results showed that the efficacy of ResVax for preventing medically significant RSV lower respiratory tract infection (LRTI) through 90 days of life in per-protocol infants was 39 percent versus placebo, missing the trial's main goal. Meanwhile, Novavax noted that the vaccine did show efficacy against a secondary objective, preventing RSV LRTI hospitalisations by 44 percent. Additionally, results revealed that ResVax reduced the risk of RSV LRTI with severe hypoxaemia by 48 percent.

CEO Stanley Erck said "while this study did not meet the pre-specified success criterion for the primary clinical endpoint…the data indicate that ResVax protects infants from some of the most serious consequences of RSV, including RSV LRTI hospitalisations and RSV LRTI with severe hypoxaemia."

Further results showed that the vaccine cut the risks of all-cause LRTI hospitalisations by 25 percent and all-cause LRTI severe hypoxaemia by 39 percent in infants through the first 180 days of life. Novavax added that earlier use of ResVax was associated with improved outcomes, with efficacy rates against RSV LRTI hospitalisation and severe RSV hypoxaemia of 53 percent and 70 percent, respectively, among women vaccinated before week 33 of pregnancy, versus 26 percent and 44 percent, respectively, for those vaccinated at later times.

Erck indicated that the company plans to meet with regulators in the US and Europe "to review these data and to discuss the path forward for licensure." Novavax said that it intends to present additional data from the study at a future research conference.

In 2016, Novavax announced that a Phase III study of ResVax in older adults failed to meet the pre-specified primary or the secondary efficacy objectives, and did not demonstrate vaccine efficacy.

For related analysis, see ViewPoints: Novavax confident it can rescue ResVax.

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