Biotech shows positive results from extension study into universal RSV vaccine

Biotechnology company, Bavarian Nordic, has revealed positive data from the extension study of its Phase II study investigating its universal respiratory syncytial virus (RSV) vaccine, MVA-BN RSV, in older adults.

Last year (2017), the company reported the results from its Phase II study, investigating various schedules and doses of its vaccine in 421 patients aged 55 and older. These results demonstrated that the vaccine induced robust antibody and T cell responses against RSV with only a single booster vaccination and these responses remained elevated for a RSV season (6 months post vaccination).

The extension study involved the re-enrolment of 88 patients one year later, after they had received a single vaccination with either a low or high dose of the vaccine in the Phase II study and were further boosted with the same vaccine dose; mimicking an annual booster regime.It has been shown in this extension study that in at least 60% of the subjects the broad antibody responses against RSV were durable and remained elevated compared to baseline, one year after receiving a single booster vaccination.

Similarly, the T cell responses against RSV also remained elevated one-year post vaccination in half of the subjects re-enrolled, depending on which of the RSV protein encoded in the vaccine was evaluated (ranging from 27% to 72% of the subjects).

Additionally, following another annual booster with the vaccine, the researchers found there was a rapid and significant increase in serum antibody responses, including neutralizing antibodies against both RSV subtypes (A & B) and total IgG and IgA antibodies against RSV. This effect was most notable in subjects with the weakest immunity at the baseline (week 56) prior to the second vaccination.

When compared to pre-vaccination levels from a year before, the boost effect was in the range of a 1.5 to 3-fold increase depending on the antibody parameter, however the increases were in the range of 1.3 to 2-fold when compared to the week 56 levels (baseline for the annual boost), as the antibody responses remained elevated one year post the first vaccination. These were also supported by a significant boost in the mucosal IgA responses measured from nasal swabs. The T cell responses against all five RSV encoded proteins were also significantly boosted following the annual vaccination. Again, this effect was most prevalent in subjects with the weakest immunity prior to the second vaccination.

“We are exceptionally happy to share these data, which show the ability of our vaccine to provide broad RSV specific immunity over multiple seasons,” explained Paul Chaplin, president and CEO of Bavarian Nordic. “This establishes our hypothesis that MVA-BN RSV is an annual booster vaccine, and is the only RSV candidate vaccine in development that has been able to demonstrate the induction of a broad immune response targeting not only antibodies, but T cells and mucosal immunity. Showing that the administration of a live virus vaccine over multiple seasons is both safe and immunogenic is a significant piece of data, which we know both KOLs and potential partners will be excited to see.”

These positive clinical results will be key in discussing the design of the Phase III study with the FDA at a meeting planned later on this year.