Sotrovimab retains activity against SARS-CoV-2 omicron variant BQ.1.1 in a non-human primate model

The SARS-CoV2 Omicron variants have acquired new Spike mutations leading to escape from the most of the currently available monoclonal antibody treatments reducing the options for patients suffering from severe Covid-19. Recently, both in vitro and in vivo data have suggested that Sotrovimab could retain partial activity against recent omicron sub-lineage such as BA.5 variants, including BQ.1.1. Here we report full efficacy of Sotrovimab against BQ.1.1 viral replication as measure by RT-qPCR in a non-human primate challengemodel.

The treatment was carried out without any adverse effects being recorded. Sotrovimab was measured in the serum of NHP at days 1, 4, 8 and 11 post-treatment, showing a similar exposure profile (Fig. 1A) as observed in humans during the COMET-ICE trial [11]. Lymphopenia was reported at 2 days post-challenge (d.p.c) in non-treated animals and in 2 out of 3 treated animals as expected in this model [10]. In this study, to empower statistical analysis, we included 4 historical controls challenged with the same batch of BQ.1.1 SARS-CoV2 virus stock at a similar dose to the 2 concomitant control NHPs. Efficacy was monitored by genomic viral RNA (gRNA) quantification using RT-qPCR (Fig. 1B). In untreated animals, gRNA was detected in tracheal fluids collected with swabs, with a median peak viral loads at 2-3 d.p.c of 6.11 log 10 copies/mL. Viral gRNA was also detected at 3 d.p.c in the broncho-alveolar lavages (BAL) with a median value of 5.55 log 10 copies/mL. At 10 d.p.c, virus was still detectable in BAL in 5 control NHPs out of 6. By contrast, the three treated animals had viral gRNA below the limit of detection both in trachea (Fig. 1B) and BAL (Fig. 1C). Comparisons of the area under the curve (D0-D14) for tracheal viral load kinetics as well as BAL viral load at day 3 reveal a significant difference (p = 0.0238) between controls and Sotrovimab treated animals.
Sotrovimab had previously been withdrawn from the therapeutic panel due to its initially proposed poor in vitro efficacy against Omicron variants, in particular BA.2 [12]. Here, we demonstrate that Sotrovimab inhibits viral replication of BQ.

Data availability statement
Data will be made available on request.

Additional information
No additional information is available for this paper.

Declaration of competing interest
The authors have declared that no conflict of interest exists.

Ethics and biosafety statement
Five female cynomolgus macaques (M. fascicularis), aged 14-15 years and originating from Mauritian AAALAC-certified breeding centres were included to this study. Four female cynomlogus macaques from Mauritian AAALAC-certified breeding centres, aged 14-15 years were also added as historical controls. All animals were housed in IDMIT facilities (CEA, Fontenay-aux-roses), under BSL-3 containment (Animal facility authorization #D92-032-02, Préfecture des Hauts de Seine, France) and in compliance with European Directive 2010/63/EU, the French regulations and the Standards for Human Care and Use of Laboratory Animals, of the Office for Laboratory Animal Welfare (OLAW, assurance number #A5826-01, US). The protocols were approved by the institutional ethical committee "Comité d'Ethique en Expérimentation Animale du Commissariat à l'Energie Atomique et aux Energies Alternatives" (CEtEA #44) under statement number A20-066 and A22-006. The study was authorized by the "Research, Innovation and Education Ministry" under registration number respectively APAFIS#29191-2021011811505374 v1 and APAFIS# 36939-2022042217237124 v1.

Antibody treatment
Sotrovimab (Xevudy 500 mg solution to dilute for perfusion) is a commercial antibody also named VIR-7831 and GSK4182136. Recommendations for humans consists in 500 mg by intravenous route, equivalent to 10 mg/kg for a patient of 50 kg. For NHPs, the treatment was administrated 96 h prior challenge by intravenous perfusion in 30 min. Sotrovimab was diluted at 1.434 mg/mL in NaCl 0.9% and injected at a dose of 10 mg/kg, which represents a volume between 34 and 50 mL.
Animals were monitored for heart rate, respiratory rate and oximetry every 10 min from treatment initiation until 30 min after the end of injection.

Quantification of Sotrovimab monoclonal antibody
Sotrovimab exposure was measured using the commercial enzyme-linked immunosorbent assay (ELISA) anti-SARS-CoV-2 Quantivac (IgG) kit (Euroimmun) which is directed against the S1 domain of the spike protein. Results were expressed in binding antibody units per mL (BAU/mL) following manufacturer instructions and converted to μg/mL using blank plasma from untreated/infected animals spiked with known quantities of Sotrovimab.

SARS-CoV-2 challenge
Treated and control animals were challenged with SARS-CoV-2 BQ.1.1 (hCoV-19/France/IDF-IPP50823/2022 -EPI_-ISL_15195982), provided by the National Reference Center for respiratory viruses at Institut Pasteur, via the combination of intranasal (1/10) and intratracheal (9/10) routes (day 0), using atropine (0.04 mg/kg) for pre-medication and ketamine (5 mg/kg) with medetomidine (0.05 mg/kg) for anesthesia. Tracheal fluids and blood samples were regularly collected following challenge. Broncho alveolar lavages (BAL) were performed at 3 and 10 days post challenge. NHPs were followed for behavior assessment and clinical score during the 7 days of the infection. Blood cell counts, hemoglobin and hematocrit were determined from EDTA blood using a DXH800 analyzer (Beckman Coulter).

Viral quantification
Viral genomic RNA (gRNA) was quantified in swabs and BAL samples by RT-qPCR with a plasmid standard concentration range . The protocols describing the procedure for the detection of SARS-CoV-2 is available on the WHO website (https://www.who.int/docs/ default-source/coronaviruse/real-time-rt-pcr-assays-for-the-detection-of-sars-cov-2-institut-pasteur-paris.pdf?sfvrsn=3662fcb6_2).