The objectives of the VBI Vaccines (VBIV) preclinical studies, which evaluated antibody binding titers and neutralizing antibody titers across a number of vaccine constructs, were to assess the impact of VBI’s proprietary enveloped virus-like particle (eVLP) platform technology vs. recombinant vaccine candidates, differences in the conformation of the spike protein, and a variety of adjuvants. The data demonstrated:
- Neutralizing Antibody (nAb) Activity: After a single dose, VBI’s eVLPs expressing a stabilized pre-fusion form of the COVID-19 spike protein elicited a nAb GMT that was 4x higher than the GMT of high-titer convalescent sera, which increased to 64x higher after a second dose
- Antibody Binding (Ab) Activity: The same eVLPs also induced, after one dose, an Ab binding GMT that was 10x higher than both the GMT of high-titer convalescent sera and the GMT induced with a stabilized pre-fusion recombinant spike protein
- Impact of Adjuvants: A variety of adjuvants tested further improved the induction of nAb titers approximately 5-fold, and promoted strong Th1-type antibody and T cell responses
- Additional Benefit of Trivalent Construct: The trivalent eVLP vaccine construct induced Ab binding titers across COVID-19, SARS, and MERS spike proteins in addition to broadening reactivity to a seasonal human coronavirus not expressed in the vaccine
As part of these studies, convalescent sera from 20 individuals who had contracted and recovered from COVID-19 were collected for comparison – this sera was further grouped according to those who mounted a high-titer, robust response to the infection and those with a low-titer, weaker response. The neutralizing activity in these studies were quanitifed using a plaque reduction neutralization test with the most stringent 90% inhibition threshold (PRNT90), which is considered the gold standard for measuring antibodies that can neutralize a virus.
In August, VBI also entered into an agreement with Therapure Biomanufacturing, an integrated Contract Development and Manufacturing Organization (CDMO), for development and manufacturing services in preparation for production of its coronavirus vaccine candidates. The collaboration with Therapure is expected to enable the initiation of clinical studies by the end of 2020. As part of the agreement, Therapure will manufacture bulk vaccine for use through Phase 2 clinical studies.
