Large-scale manufacturing and characterization of a Sars Cov-2 virus-like particle vaccine adsorbed onto alhydrogel and adjuvanted with K3 CpG oligodeoxynucleotide for use in phase 1/2 clinical trials

Abstract

Emergence of COVID-19 pandemic has been met by an exceptionally fast response from vaccine makers around the globe. Vaccines that elicit excellent immunological responses against SARS-CoV-2 are now widely utilized. Existing platforms include mRNA-lipid nanoparticle-based vaccines, adenovirus vectored vaccines, various inactivated virus vaccines and subunit vaccines. We have previously described a novel virus-like particle (VLP) platform expressing the hexaproline prefusion stabilized Spike protein along with the nucleocapsid, membrane and envelope structural proteins. In mice, ferrets and rats, VLPs adjuvanted with K3 CpG Oligodeoxynucleotide (ODN) and adsorbed onto 2% Aluminum Hydroxide (Alum), induced robust humoral and cellular immune response against Spike and Nucleocapsid proteins. Herein, we have expanded our work to manufacture the virus like particles in a GMP compliant facility intended for testing in phase I/II clinical trials. The technology transfer comprises i) VLP production from suspension adapted HEK293 cells, ii) purification with multimodal fast protein liquid chromatography (FPLC) and iii) concentration and diafiltration using tangential flow filtration (TFF). We have successfully scaled up our production from 50 mL of HEK293 cell culture to 5 L bioreactor, achieving yields reaching up to 40 mg VLPs per L of cell culture. Furthermore, several methods were developed to determine protein identity, purity, functionality, stability and immunopotency of VLP vaccine that was finally formulated with Alum + CpG ODN. Moreover, we investigated the immunogenicity of VLPs decorated either with Wuhan (Hu-1) or with Alpha (B.1.1.7) variant Spike against receptor binding domains (RBD) specific to other variants of concern (VoC). Although our vaccine platform, could further benefit from process optimization to improve VLP yield, this study presents the first pilot scale production and purification of variant specific hexaproline prefusion stabilized SARS-CoV-2 VLPs. VLP preparations complying with our quality control parameters were released for fill and finish and were used for subsequent Phase 1 (NCT04818281) and Phase 2 clinical trials (NCT04962893).