Manufacturing a chimpanzee adenovirus-vectored SARS-CoV-2 vaccine to meet global needs

Abstract

Manufacturing has been the key factor limiting rollout of vaccination during the COVID-19 pandemic, requiring rapid development and large-scale implementation of novel manufacturing technologies. ChAdOx1 nCoV-19 (AZD1222, Vaxzevria) is an efficacious vaccine against SARS-CoV-2, based upon an adenovirus vector. We describe the development of a process for the production of this vaccine and others based upon the same platform, including novel features to facilitate very large-scale production. We discuss the process economics and the "distributed manufacturing" approach we have taken to provide the vaccine at globally-relevant scale and with international security of supply. Together, these approaches have enabled the largest viral vector manufacturing campaign to date, providing a substantial proportion of global COVID-19 vaccine supply at low cost.

Keywords: adenovirus; distributed manufacturing; vaccine.

Figure 1

Development and scale‐up of fed‐batch process. (a) Small‐scale USP productivity of ChAdOx1 luciferase, ChAdOx1 LassaGP, and ChAdOx2 GFP with BalanCD medium/feed (infected at 4 × 10⁶ cells/ml, MOI = 10) as compared with our previously established conditions in CD293 medium (infected at 1 × 10⁶ cells/ml, MOI = 3) (Fedosyuk et al., 2019). ChAdOx1‐luciferase infections were performed in a 3 L bioreactor. The other two viruses were produced in 30 ml volume in shake flasks. Results shown are the median and range of qPCR results from technical duplicate samples from a single reactor for ChAdOx1‐luciferase, and from triplicate flasks for the other viruses. (b) Cell‐specific productivity of ChAdOx1 nCoV‐19 in shake flasks at 30 ml working volume at MOI = 3 (red) and MOI = 10 (black). For each condition, the peak volumetric productivity from the timecourse data shown in Figures S1b,c was converted to a cell‐specific productivity by division by the cell density at infection. (c) and (d) Examples of 50 and 200 L batches with high MOI fed‐batch upstream process. (c) Cell growth (solid lines) and viability (dashed lines). (d) Drug substance (DS) quality following purification. MOI, multiplicity of infection; qPCR, quantitative polymerase chain reaction; USP, upstream process

Figure 2

Development of a low MOI upstream process. (a) compares, in schematic form, the original high MOI USP with the low MOI process developed for scale up. Red text indicates key changes in the low MOI process. (b)–(d) Results with the low MOI upstream process at 3 L (blue) and 1000 L (red) scale, as compared with the MOI = 10 process at 3 L (black). (b) Cell counts (solid lines, filled symbols) and viability (dashed lines, open symbols). (c) Glucose (solid lines, filled symbols) and lactate (dashed lines, open symbols). (d) Productivity. Where present, error bars indicate median and range of duplicate cultures at 3 L scale. Other data was obtained in singlicate. (e) Similar genome‐containing virus particle: infectious unit ratios from successive runs of the high and low MOI processes at a variety of scales. qPCR and infectivity assays were performed on crude viral harvest samples collected 6 days after infection of the culture. MOI, multiplicity of infection; qPCR, quantitative polymerase chain reaction; USP, upstream process

Figure 3

Simplified downstream process, with direct loading of clarified lysate on AEX. (a) Schematics of previous and revised DSPs. The dashed box indicates potential execution of depth filter clarification and AEX as a single unit operation. (b) Loading of clarified lysate on 3 ml Sartobind Q anion exchange membrane, followed by elution with a gradient of increasing salt concentration. The peaks labeled 1 and 2 (at 24 and 37 mS/cm) were analyzed by Coomassie‐stained SDS‐PAGE (c), with comparison with virus purified by caesium chloride gradient ultracentrifugation (CsCl) and molecular weight marker (MW, with 80 kDa indicated). Peak 1 contains impurities (notably free hexon protein) while Peak 2 contains predominantly virus. (d) AEX chromatogram obtained using clarified lysate from low MOI upstream process, run at 1000 L scale. Absorbance at 280 nm is shown in blue, conductivity in red. Results are shown from one of two cycles run on a 5000 ml Sartobind Q capsule, each loaded to approximately 1.5 × 10¹³ VP per ml of membrane. Numerals indicate stages: 1 = loading, 2 = wash, 3 = elution, 4 = 1 M NaCl strip and 1 M sodium hydroxide sanitization. (e) Product recovery and quality from the 1000 L scale process shown in (b), after AEX and after final formulation by TFF and 0.2 μm filtration. AEX, anion exchange; DSP, downstream process; MOI, multiplicity of infection; SDS‐PAGE, sodium dodecyl sulfate–polyacrylamide gel electrophoresis; TFF, tangential flow filtration

Figure 4

Rapid implementation of a low cost distributed manufacturing strategy. (a) tabulates modeled costs of bulk DS production using the initial process at 200 L scale (with high MOI and including the additional TFF step), and using the optimized process at 2000L scale (with low MOI and direct AEX). This excludes fill/finish and some analytical costs. For further details, please see Supporting Information. (b) A timeline of key manufacturing‐related activities, highlighting activities performed in parallel and relationship to the timing of key regulatory and clinical events. (c) illustrates global distributed manufacturing strategy, with interplay between centrally co‐ordinated activities, common origins of certain key materials, and multiple parallel regional drug substance and drug product supply chains. ChAdOx1 nCoV‐19 drug substance is currently being manufactured in the countries shown in red. Vial photograph: Arne Müseler/arne‐mueseler.com/CC‐BY‐SA‐3.0/https://creativecommons.org/licenses/by-sa/3.0/de/deed.de. Map created using mapchart.com, under CC‐BY‐SA‐4.0 licence. AEX, anion exchange; DS, drug substance; MOI, multiplicity of infection; TFF, tangential flow filtration