Novavax (NVAX) Phase 3 Prepare Trial of ResVax for Prevention of RSV Disease in Infants Doesn't Meet Primary Endpoint

February 28, 2019 7:01 AM EST

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Novavax, Inc. (Nasdaq: NVAX) today announced results from Prepare™, a global Phase 3 clinical trial using ResVax, an aluminum adjuvanted respiratory syncytial virus (RSV) fusion (F) protein recombinant nanoparticle vaccine. ResVax is being developed to protect infants via maternal immunization against RSV disease. In the Prepare trial, efficacy of ResVax against the primary and two secondary endpoints in per-protocol infants with RSV lower respiratory tract infection (LRTI) through 90 days of life was:

  • 39% against medically significant RSV LRTI (97.5%CI, -1% to 64%)
  • 44% against RSV LRTI hospitalizations (95%CI, 20% to 62%)
  • 48% against RSV LRTI with severe hypoxemia (95%CI, -8% to 75%)

Pre-specified exploratory analyses of these same vaccine efficacy endpoints, which include additional data ascertained from hospitalization records, were:

  • 41% against medically significant RSV LRTI (95%CI, 16% to 58%)
  • 42% against RSV LRTI hospitalizations (95%CI, 17% to 59%)
  • 60% against RSV LRTI with severe hypoxemia (95%CI, 32% to 76%)

“Pneumonia stubbornly remains the leading killer of children under the age of five worldwide. The new maternal vaccine from Novavax shows promise in the fight against RSV, the most common cause of viral pneumonia in young children,” said Dr. Keith Klugman, Director of the Bill & Melinda Gates Foundation’s Pneumonia Program. “We are very encouraged that the Novavax maternal RSV vaccine reduced severe RSV hypoxemia by 60% in the first months of life and believe this vaccine has great potential for reducing RSV-associated deaths in young babies.” The Prepare trial was supported by a grant of up to $89.1 million from the Bill & Melinda Gates Foundation.

“Importantly, while this study did not meet the pre-specified success criterion for the primary clinical endpoint of this trial, the data indicate that ResVax protects infants from some of the most serious consequences of RSV, including RSV LRTI hospitalizations and RSV LRTI with severe hypoxemia,” said Stanley C. Erck, President and Chief Executive Officer of Novavax, Inc. “The potential to prevent these most serious outcomes during infants’ most vulnerable months of life could have a profound impact upon the global burden of RSV disease. Our next steps include meeting with U.S. and European regulators to review these data and to discuss the path forward for licensure. We wish to acknowledge and thank the investigators, the Novavax team and the many mothers and their families around the world that participated in this historic trial, bringing the world one step closer to an RSV vaccine.”

Other observations from the Prepare trial:

  • Reduction in all-cause LRTI hospitalizations (25%) and all-cause LRTI severe hypoxemia (39%) in infants observed through the first 180 days of life
  • Mothers vaccinated from 28 up to < 33 weeks of pregnancy, showed vaccine efficacy rates against RSV LRTI hospitalization of 53% and severe RSV hypoxemia of 70% through the first 90 days of their infants’ lives, compared with 26% and 44% for mothers vaccinated ≥ 33 weeks of pregnancy
  • Over 90% of RSV LRTI hospitalizations and RSV LRTI severe hypoxemia in the placebo group occurred in the first 90 days of life
  • 99% of vaccinated mothers had measurable antibody responses to the vaccine, with ≥100% transplacental transfer for all antibody types measured
  • ResVax appears safe in mothers and their infants through 180 days post-delivery

Novavax intends to present additional results from the Prepare trial at an upcoming medical meeting.

Webcast Conference Call

Novavax will host a webcast/conference call today at 8:00 a.m. EST. The webcast can be accessed via a link on the home page of the Novavax website ( or through the “Investor Info”/“Events” tab on the Novavax website. Listeners who wish to ask questions or don’t have internet access can dial-in to the conference call at (877) 212-6076 (domestic) or (707) 287-9331 (international) and use passcode 7679808.

A replay of the webcast will be available on the Novavax website until May 28, 2019 and a replay of the conference call only will be available starting at 11:00 a.m. ET on February 28, 2019 until 11:00 a.m. ET on March 7, 2019. To access the conference call replay, dial (855) 859-2056 (domestic) or (404) 537-3406 (international) and use passcode 7679808.

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