Phase I data showing stimulation of cellular immunity suggest MVA-BN RSV could provide a protective advantage over F protein approaches.
By Michael Haydock, Lead Analyst
22 July 2016
I am the Lead Analyst of the immunology and inflammation and infectious diseases and vaccines teams at Datamonitor Healt...
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In a first-in-human Phase I study, Bavarian Nordic’s viral vector respiratory syncytial virus (RSV) vaccine (MVA-BN RSV), was shown to elicit both humoral and cellular responses in seropositive patients, potentially providing a protective advantage over Novavax’s fusion (F) protein-based nanoparticle vaccine which is further ahead in clinical development. The MVA-BN RSV vaccine is based on a recombinant modified vaccinia virus Ankara (MVA) vector which expresses the surface RSV F and attachment (G) glycoproteins, as well as the conserved internal nucleocapsid and matrix proteins. Bavarian Nordic hopes that the inclusion of conserved intracellular proteins will be a key differentiator from Novavax’s RSV F vaccine because they are known targets of cluster of differentiation 8+ (CD8+) T-cells, which may play an important role in protection from severe infection.
In the Phase I RSV-MVA-001 study, which compared the safety and immunogenicity of a two-dose schedule of MVA-BN RSV against placebo, 100% (18/18) and 94% (17/18) of adults aged 50–65 years displayed boosted T-cell responses against whole RSV and G protein respectively, with high interferon-gamma and low interleukin-4 measurements suggestive of a T-helper type 1-biased response. These cellular responses were in addition to boosted serum immunoglobulin G responses, which have already been shown to provide protection in an earlier Phase II proof-of-efficacy study of Novavax’s RSV F vaccine. While the protective efficacy of cellular responses against RSV infection is still controversial and yet to be proven in Phase II studies, a recent human challenge model has shown that the higher abundance of CD8+ T cells in the lungs is associated with reduced symptoms and viral load. Vaccines which elicit strong cellular immunity against multiple viral proteins could therefore possess superior efficacy against severe infection (if not all virologically confirmed RSV infection) compared to F protein vaccines, but Phase II proof-of-concept efficacy data will be required to confirm this hypothesis.
Datamonitor Healthcare’s respiratory syncytial virus vaccines: pipeline evaluates the clinical and commercial attractiveness of early-phase and late-phase candidates, providing an assessment of future product positioning and competitiveness in the marketplace.
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