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ICAAC Presentation: Immunization of Pregnant Baboons With the RSV F Nanoparticle Vaccine Protects Infant Baboons Challenged With Respiratory Syncytial Virus in a Comparable Manner to Infants Prophylaxed With Palivizumab

  • Immunization of pregnant baboons generates anti-F IgG antibodies that are transferred from mothers to their infants
  • When challenged with RSV, infant baboons born to immunized mothers show equivalent protection to infant baboons receiving palivizumab (Synagis ®) therapy

GAITHERSBURG, Md., Sept. 8, 2014 (GLOBE NEWSWIRE) -- Novavax, Inc. (Nasdaq:NVAX), a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of recombinant nanoparticle vaccines and adjuvants, today announced pre-clinical data presented on Sunday, September 7, 2014, at 54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Washington, DC. These data demonstrate that immunization of pregnant baboons in the third trimester of pregnancy generates anti-F IgG antibodies that are transferred to the newborn infants. The study further demonstrated that infants born to immunized mothers were protected from RSV challenge at a level comparable to palivizumab (Synagis ®) therapy.

The ICAAC slide presentation 077: I-649, titled, "Immunization of Pregnant Baboons with the RSV F Nanoparticle Vaccine Protects Infant Baboons Challenged with Respiratory Syncytial Virus in a Comparable Manner to Infants Prophylaxed with Palivizumab" was presented by Dr. Robert Welliver of the University of Oklahoma, Health Sciences on Sunday, September 7.

Infant olive baboons develop RSV disease that mimics the clinical and pathological findings observed in human infants with RSV infection, making them an appropriate model for evaluation of maternal immunization with an RSV vaccine. Novavax, which is developing its RSV F-protein nanoparticle vaccine (RSV F nanoparticle vaccine) for maternal, pediatric and elderly immunizations to prevent RSV disease, collaborated with the University of Oklahoma on this study to evaluate the efficiency of maternal RSV F antibody transfer and the efficacy of its RSV vaccine in infants of vaccinated mother baboons compared to palivizumab recipients and untreated controls.

In this study, seronegative pregnant baboons (5 pairs) received either three intramuscular injections (IM) in the third trimester with a 60 μg/dose of the RSV vaccine and 1.2 mg of aluminum phosphate as an adjuvant at three week intervals, or saline. The paired infant baboons were challenged on day 30 intratracheally with 2-5x108pfu1 of respiratory syncytial virus (RSV). Similarly, 4 pairs of infant baboons were administered either 15mg/kg palivizumab or saline IM before the RSV challenge. Blood was collected on day 0 and bronchoalveolar lavage (BALs) was performed to assess lung viral load and leukocyte levels on day 0, 5, 7 and 10. Blinded observations of respiratory rates were made in pairs. Pulmonary function tests were performed in the infants of vaccinated and control mothers.

In recipients of the RSV F nanoparticle vaccine, antibody responses were measured in the mother on the day of birth (day 0 (zero)) and in the infant on day 30. Geometric mean anti-F IgG antibody titers were 115,535 Elisa Units (EU) and 32,774 EU, palivizumab competing antibodies (PCA) were 342 and 98 μg/ml and RSV A neutralizing antibodies (A MN) were 380 and 121, in the mothers and infants, respectively. Sera from infants administered palivizumab on day 29 had day 30 geometric mean anti-F IgG were 88,475 EU, PCA 196μg/ml and A MN 269. Palivizumab treated and infants of vaccinated mothers had significantly lower fold rise in respiratory rates compared to their matched, untreated pairs, (p=0.0008, and p=0.0028). Decreases in lung viral loads and BAL leukocytes were observed in treated infants. Reduced work of breathing and higher peak expiratory flow was observed in infants of vaccinated mothers.

"This study provides direct empirical evidence, in a relevant higher-primate model, to support the maternal immunization strategy for our RSV F nanoparticle vaccine," said Greg Glenn, M.D., Senior Vice President, Research and Development at Novavax. "While we were confident that we would see maternal transfer of anti-F antibodies, we now have evidence to show that our vaccine candidate can not only protect against RSV disease, but provide protection similar to palivizumab, and may provide superior anti-inflammatory benefits relative to palivizumab. This study adds to substantial evidence and validation supporting our RSV maternal immunization strategy as we move towards the initiation of our first study in pregnant women in the next few months."

About Novavax

Novavax, Inc. (Nasdaq:NVAX) is a clinical-stage biopharmaceutical company creating vaccines and vaccine adjuvants to address a broad range of infectious diseases worldwide. Using innovative proprietary recombinant nanoparticle vaccine technology, the company produces vaccine candidates to efficiently and effectively respond to both known and newly emergent diseases.

About RSV

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.

Forward-Looking Statements

Statements herein relating to the future of Novavax and the ongoing development of its vaccine and adjuvant products are forward-looking statements. Novavax cautions that these forward looking statements are subject to numerous risks and uncertainties, which could cause actual results to differ materially from those expressed or implied by such statements. These risks and uncertainties include those identified under the heading "Risk Factors" in the Novavax Annual Report on Form 10-K for the year ended December 31, 2013, and filed with the Securities and Exchange Commission (SEC). Investors are cautioned not to place considerable reliance on the forward-looking statements contained in this press release. You are encouraged to read company filings with the SEC, available at sec.gov, for a discussion of these and other risks and uncertainties. The forward-looking statements in this press release speak only as of the date of this document, and the company undertakes no obligation to update or revise any of the statements. The company's business is subject to substantial risks and uncertainties, including those referenced above. Investors, potential investors, and others should give careful consideration to these risks and uncertainties.

1 "Plaque Forming Units": PFU is a measurement of only those viral particles that will effectively produce a plaque and infect cells."

CONTACT: Barclay A. Phillips SVP, Chief Financial Officer and Treasurer Novavax, Inc. 240-268-2000

Source:Novavax, Inc.