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. 2023 Sep 20:234:115523.
doi: 10.1016/j.jpba.2023.115523. Epub 2023 Jun 11.

Development and qualification of cell-based relative potency assay for a human respiratory syncytial virus (RSV) mRNA vaccine

Hualin Helen Li  1 , Jenny Xu  2 , Li He  3 , Lynne Ireland Denny  2 , Richard R Rustandi  2 , Geethanjali Dornadula  2 , Brock Fiorito  2 , Zhi-Qiang Zhang  2
Affiliations

Development and qualification of cell-based relative potency assay for a human respiratory syncytial virus (RSV) mRNA vaccine

Hualin Helen Li et al. J Pharm Biomed Anal. .

Abstract

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections worldwide. A safe and effective RSV vaccine has been an elusive goal but recent advances in vaccine technology have improved the likelihood that a vaccine for the prevention of RSV could be licensed in near future. We have developed an RSV vaccine V171 consisting of four lipids and messenger ribonucleic acid (mRNA) encoding an engineered form of the RSV F protein stabilized in its prefusion conformation. The lipids form lipid nanoparticles (LNP) with mRNA encapsulated during process, which protects the mRNA from degradation and enables the mRNA to be delivered into mammalian cells. Once inside the cells, the mRNA then can be translated into RSV F protein and elicit both humoral and cellular immune responses. Preclinical results and Phase I clinical trial results indicate that this mRNA vaccine targeting RSV F protein is a promising RSV vaccine approach and should be further evaluated in clinical trials. We have developed a cell-based relative potency assay to support the Phase II development of this vaccine. Test articles and a reference standard are tested with serial dilutions in a 96-well plate pre-seeded with Hep G2 cells. Cells were incubated for 16-18 h after transfection and then permeabilized and stained with a human monoclonal antibody specific to RSV F protein, followed by a fluorophore-conjugated secondary antibody. The plate is then analyzed for percentage of transfected cells and relative potency of the test article is calculated by comparing its EC50 to that of a reference standard. This assay takes advantage of the fact that due to the inherent variability in biological test systems an absolute measure of potency is more variable than a measure of activity relative to a standard. Targeting testing relative potency range 25-250 %, our assay showed an R2 close to 1 for linearity, relative bias of 1.05-5.41 %, and intermediate precision of 11.0 %. The assay has been used for testing of process development samples, formulation development samples, as well as drug product intermediate (DPI) and drug product (DP) in support of Phase II development of our RSV mRNA vaccine.

Keywords: Potency assay; Respiratory syncytial virus; Vaccine; mRNA.

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Conflict of interest statement

Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jenny Xu, Zhi-Qiang Zhang has patent #Patent_US20220404338A1 licensed to Merck Sharp & Dohme LLC, Rahway, NJ (US). Conflict of interest HHL, JX, HL, LID, RRR, GD, and BF are current employees at Merck & Co. Inc. ZZ was an employee at Merck & Co. Inc. when the work described in the manuscript was conducted.