RESUMEN
During the COVID-19 pandemic, long development timelines typically associated with vaccines were challenged. The urgent need for a vaccine provided a strong driver to reevaluate existing vaccine development approaches. Innovative approaches to regulatory approval were realized, including the use of platform-based technology. In collaboration with the International AIDS Vaccine Initiative, Inc. (IAVI), Merck & Co., Inc., Rahway, NJ, USA rapidly advanced an investigational SARS-CoV-2 vaccine based on the recombinant vesicular stomatitis virus (rVSV) platform used for the Ebola vaccine ERVEBO (rVSV∆G-ZEBOV-GP). An rVSV∆G-SARS-CoV-2 vaccine candidate was generated using the SARS-CoV-2 spike protein to replace the VSV G protein. The purification process development for this vaccine candidate was detailed in this paper. Areas were highlighted where the ERVEBO platform process was successfully adopted and where additional measures were needed for the SARS-CoV-2 vaccine candidate. These included: (i) endonuclease addition directly into the bioreactor prior to harvest, (ii) inclusion of a core-shell chromatography step for improved purification, and (iii) incorporation of a terminal, sterile filtration step to eliminate the need for aseptic, closed processing. High infectious virus titers were achieved in Phase 3 clinical drug substance (>108 PFU mL-1 ), and process consistency was demonstrated across four large scale batches that were completed in 6 months from clone selection.
Asunto(s)
COVID-19 , Vacunas contra el Virus del Ébola , Ebolavirus , Fiebre Hemorrágica Ebola , Glicoproteína de la Espiga del Coronavirus , Estomatitis Vesicular , Vacunas Virales , Animales , Humanos , Vacunas contra el Virus del Ébola/genética , Fiebre Hemorrágica Ebola/prevención & control , Vacunas contra la COVID-19 , SARS-CoV-2/genética , Pandemias , COVID-19/prevención & control , Vesiculovirus , Virus de la Estomatitis Vesicular Indiana , Vacunas Sintéticas , Anticuerpos AntiviralesRESUMEN
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the viral agent that is responsible for the coronavirus disease-2019 (COVID-19) pandemic. One of the live virus vaccine candidates Merck and Co., Inc. was developing to help combat the pandemic was V590. V590 was a live-attenuated, replication-competent, recombinant vesicular stomatitis virus (rVSV) in which the envelope VSV glycoprotein (G protein) gene was replaced with the gene for the SARS-CoV-2 spike protein (S protein), the protein responsible for viral binding and fusion to the cell membrane. To assist with product and process development, a quantitative Simple Western (SW) assay was successfully developed and phase-appropriately qualified to quantitate the concentration of S protein expressed in V590 samples. A strong correlation was established between potency and S-protein concentration, which suggested that the S-protein SW assay could be used as a proxy for virus productivity optimization with faster data turnaround time (3 h vs 3 days). In addition, unlike potency, the SW assay was able to provide a qualitative profile assessment of the forms of S protein (S protein, S1 subunit, and S multimer) to ensure appropriate levels of S protein were maintained throughout process and product development. Finally, V590 stressed stability studies suggested that time and temperature contributed to the instability of S protein demonstrated by cleavage into its subunits, S1 and S2, and aggregation into S multimer. Both of which could potentially have a deleterious effect on the vaccine immunogenicity.