Abstract
Background Ronapreve demonstrated clinical application in post-exposure prophylaxis, mild/moderate disease and in the treatment of seronegative patients with severe COVID19 prior to the emergence of the Omicron variant in late 2021. Numerous reports have described loss of in vitro neutralisation activity of Ronapreve and other monoclonal antibodies for BA.1 Omicron and subsequent sub-lineages of the Omicron variant. With some exceptions, global policy makers have recommended against the use of existing monoclonal antibodies in COVID19. Gaps in knowledge regarding the mechanism of action of monoclonal antibodies are noted, and further preclinical study will help understand positioning of new monoclonal antibodies under development.
Objectives The purpose of this study was to investigate the impact of Ronapreve on compartmental viral replication as a paradigm for a monoclonal antibody combination. The study also sought to confirm absence of in vivo activity against BA.1 Omicron (B.1.1.529) relative to the Delta (B.1.617.2) variant.
Methods Virological efficacy of Ronapreve was assessed in K18-hACE2 mice inoculated with either the SARS-CoV-2 Delta or Omicron variants. Viral replication in tissues was quantified using qRT-PCR to measure sub-genomic viral RNA to the E gene (sgE) as a proxy. A histological examination in combination with staining for viral antigen served to determine viral spread and associated damage.
Results Ronapreve reduced sub-genomic viral RNA levels in lung and nasal turbinate, 4 and 6 days post infection, for the Delta variant but not the Omicron variant of SARS-CoV-2 at doses 2-fold higher than those shown to be active against previous variants of the virus. It also appeared to block brain infection which is seen with high frequency in K18-hACE2 mice after Delta variant infection. At day 6, the inflammatory response to lung infection with the Delta variant was altered to a mild multifocal granulomatous inflammation in which the virus appeared to be confined. A similar tendency was also observed in Omicron infected, Ronapreve-treated animals.
Conclusions The current study provides evidence of an altered tissue response to the SARS-CoV-2 after treatment with a monoclonal antibody combination that retains neutralization activity. These data also demonstrate that experimental designs that reflect the treatment use case are achievable in animal models for monoclonal antibodies deployed against susceptible variants. Extreme caution should be taken when interpreting prophylactic experimental designs when assessing plausibility of monoclonal antibodies for treatment use cases.
Competing Interest Statement
AO and SR are Directors of Tandem Nano Ltd and co-inventors of patents relating to drug delivery. AO has been co-investigator on funding received by the University of Liverpool from ViiV Healthcare and Gilead Sciences unrelated to COVID-19 in the past 3 years. AO has received personal fees from Gilead and Assembly Biosciences in the past 3 years unrelated to COVID-19. AO was a member of the Trial Management Group for the AGILE phase I/II platform trial until January 2023 and AGILE received funding from Ridgeback and GSK in the past 3 years for which AO was not a co-investigator. SR has received research funding from ViiV and AstraZeneca and consultancy from Gilead not related to the current paper. No other conflicts are declared by the authors.
Footnotes
Inclusion of histological and immunohistological analyses. Including, the effect of Ronapreve on pulmonary changes and viral spread to the brain after infection with the Delta and Omicron variants.
