The endangered future of Syngem, a novel bacterium-like particle based, needle-free, RSV vaccine

Ascough S, Vlachantoni I, Kalyan M, Haijema BJ, Wallin- Weber S, Dijkstra-Tiekstra M, Ahmed MS, Roosmalen M van, Grimaldi R, Zhang Q, Leenhouts K, Openshaw PJ and Chiu C.

Despite numerous years of research we are still lacking a safe and effective RSV vaccine. This process is hindered by numerous problems: the lack of a correlate of protection being one of them.That this has major consequences for vaccine development, is illustrated by the study performed by Stephanie Ascough, Peter Openshaw and colleagues. In their paper they describe the results of a randomized controlled, phase 1 trial of a novel needle-free RSV vaccine: SynGEM. The vaccine is based on a stable pre-fusion F antigen of the virus, and uses a bacterium-like-particle (BLP) as an immune-enhancing carrier. The study confirms that the vaccine is safe and that it is capable of inducing a mild (about 2 to 3-fold), but prolonged, increase in RSV-specific antibodies. However, the study didn’t reach the endpoint threshold and for now, SynGEM is withheld from proceeding to next phase trials.
This study illustrates, that the lack of a correlate of protection brings an uncertainty to the table, which could lead to the premature termination of a potentially effective RSV vaccine. The use of a human challenge model (HCM) in RSV vaccine development would offer the possibility to circumvent this insecurity. Furthermore it might accelerate RSV-vaccine development.
Written by Sjanna Besteman

Paper of the month | March 2019