Bavarian Nordic A/S announced positive results for MVA-BN RSV, a universal vaccine candidate designed to induce protective immune responses against both RSV subtypes (A & B). The vaccine was shown to be both well tolerated and immunogenic at both dose levels investigated. The study confirmed the hypothesis that MVA-BN RSV is the first vaccine candidate designed to induce a broad and robust immune response against five distinct RSV proteins following a single shot or booster vaccination, using Bavarian’s proprietary viral platform MVA-BN (Modified Vaccinia Ankara – Bavarian Nordic).
The randomized, placebo-controlled study enrolled 421 subjects aged 55 and older, at 12 centers across the United States. These subjects were enrolled into four active arms of the study, which examined the effects of both a high (5×108) and low (1×108) dose, administered as either one or two vaccinations (day 0, 28) and compared to a placebo arm.
A single vaccination induced the highest booster responses in both antibodies and T cells against RSV compared to a prime-boost regime. Compared to the subjects receiving placebo, a significant boost (2-4 fold) in antibodies was observed 2 weeks post the single booster vaccination. This included neutralizing and total antibodies (IgG) against RSV, as well as IgA antibodies, which are associated with mucosal responses and are thought to play an important role in protection against RSV. Significant T cell responses (5-10 fold) to all five RSV proteins were observed in the majority of subjects 1 week post the single booster vaccination.
At the 3 month time point post vaccination the immune responses induced by the two active doses investigated demonstrated significant boosts over placebo. Immune responses were seen to be similar across all active doses, potentially confirming the results seen with the 1×108 dose tested in a Phase 1 which also demonstrated durable antibody responses 6 months post vaccination.
Blood samples from the 6 month time point post vaccination are currently being tested in this Phase 2 study. Subjects that received a single vaccination with either dose will be given an additional booster later this year and followed for another RSV season, to help establish the immune responses 12 months post vaccination and the effect of another booster vaccination.
“Like influenza, RSV is associated with thousands of deaths in older adults annually in the U.S.,” Steven J. Lawrence, MD, MSc, Associate Professor of Medicine, Division of Infectious Diseases, Washington University School of Medicine, and National Coordinating Investigator of the study remarked. “However unlike influenza, there are currently no licensed vaccines to protect against RSV. RSV vaccines have been elusive because of unique interactions the virus has with the human immune system making older vaccine technologies unsuccessful. A safe and effective vaccine to prevent complications of RSV could have a substantial impact on keeping older adults healthy.”
“These Phase 2 data have confirmed that our universal RSV vaccine performed as we intended and induced a broad immune response against multiple targets of RSV, more than any other previous RSV vaccine candidate tested to date. Another important differentiating factor is that our vaccine is built upon our MVA platform and as such has also induced a robust T-cell response against five RSV proteins and a mucosal immune response, which is another parameter that has been largely ignored in previous attempts to develop a prophylactic RSV vaccine.” said Paul Chaplin, President and CEO of Bavarian Nordic.
Filed Under: Drug Discovery