Intramuscular Versus Intravenous SARS-CoV-2 Neutralizing Antibody Sotrovimab for Treatment of COVID-19 (COMET-TAIL): A Randomized Non-inferiority Clinical Trial (preprint)

Background: Convenient administration of coronavirus disease 2019 (COVID-19) treatment in community settings is desirable. Sotrovimab is a pan-sarbecovirus dual-action monoclonal antibody formulated for intravenous (IV) or intramuscular (IM) administration for early treatment of mild/moderate COVID-19. Methods: This phase 3, randomized, multicenter, open-label study tested non-inferiority of IM to IV administration using a 3.5% absolute non-inferiority margin. From June to August 2021, patients aged [≥]12 years with COVID-19, not hospitalized or receiving supplemental oxygen, and at high risk for progression were randomized 1:1:1 to a single 500-mg IV sotrovimab infusion or 500-mg or 250-mg IM sotrovimab injection. The primary composite endpoint was progression to all-cause hospitalization for >24 hours for acute management of illness or all-cause death through day 29. Results: Sotrovimab 500 mg IM was non-inferior to 500 mg IV: 10/376 (2.7%) participants in the sotrovimab 500-mg IM group versus 5/378 (1.3%) in the sotrovimab 500-mg IV group met the primary endpoint (absolute adjusted risk difference: 1.06% [95% confidence interval [CI]: -1.15%, 3.26%]). The CI upper limit was lower than the prespecified non-inferiority margin of 3.5%. 250-mg IM group enrollment was discontinued early because a greater proportion of hospitalizations was seen in that group versus the 500-mg groups. Serious adverse events occurred in <1% to 2% of participants across groups. Four participants experienced serious disease related events and died (500 mg IM: 2/393 [<1%]; 250 mg IM: 2/195 [1%]). Conclusions: Sotrovimab 500-mg IM injection was well tolerated and non-inferior to IV administration. IM administration could expand outpatient treatment access for COVID-19.

The dual function monoclonal antibodies VIR-7831 and VIR-7832 demonstrate potent in vitro and in vivo activity against SARS-CoV-2 (preprint)

VIR-7831 and VIR-7832 are dual action monoclonal antibodies (mAbs) targeting the spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). VIR-7831 and VIR-7832 were derived from a parent antibody (S309) isolated from memory B cells of a 2003 severe acute respiratory syndrome coronavirus (SARS-CoV) survivor. Both mAbs contain an LS mutation in the Fc region to prolong serum half-life and potentially enhance distribution to the respiratory mucosa. In addition, VIR-7832 encodes an Fc GAALIE mutation that has been shown previously to evoke CD8+ T-cells in the context of an in vivo viral respiratory infection. VIR-7831 and VIR-7832 potently neutralize live wild-type SARS-CoV-2 in vitro as well as pseudotyped viruses encoding spike protein from the B.1.1.7, B.1.351 and P.1 variants. In addition, they retain activity against monoclonal antibody resistance mutations that confer reduced susceptibility to currently authorized mAbs. The VIR-7831/VIR-7832 epitope does not overlap with mutational sites in the current variants of concern and continues to be highly conserved among circulating sequences consistent with the high barrier to resistance observed in vitro. Furthermore, both mAbs can recruit effector mechanisms in vitro that may contribute to clinical efficacy via elimination of infected host cells. In vitro studies with these mAbs demonstrated no enhancement of infection. In a Syrian Golden hamster proof-of concept concept wildtype SARS-CoV-2 infection model, animals treated with VIR-7831 had less weight loss, and significantly decreased total viral load and infectious virus levels in the lung compared to a control mAb. Taken together, these data indicate that VIR-7831 and VIR-7832 are promising new agents in the fight against COVID-19.

Remdesivir potently inhibits SARS-CoV-2 in human lung cells and chimeric SARS-CoV expressing the SARS-CoV-2 RNA polymerase in mice. (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 as the causative agent of the novel pandemic viral disease COVID-19. With no approved therapies, this pandemic illustrates the urgent need for safe, broad-spectrum antiviral countermeasures against SARS-CoV-2 and future emerging CoVs. We report that remdesivir (RDV), a monophosphoramidate prodrug of an adenosine analog, potently inhibits SARS-CoV-2 replication in human lung cells and primary human airway epithelial cultures (EC50 = 0.01 M). Weaker activity was observed in Vero E6 cells (EC50 = 1.65 M) due to their low capacity to metabolize RDV. To rapidly evaluate in vivo efficacy, we engineered a chimeric SARS-CoV encoding the viral target of RDV, the RNA-dependent RNA polymerase, of SARS-CoV-2. In mice infected with chimeric virus, therapeutic RDV administration diminished lung viral load and improved pulmonary function as compared to vehicle treated animals. These data provide evidence that RDV is potently active against SARS-CoV-2 in vitro and in vivo, supporting its further clinical testing for treatment of COVID-19.

The coronavirus proofreading exoribonuclease mediates extensive viral recombination (preprint)

Coronaviruses (CoVs) emerge as zoonoses and cause severe disease in humans, demonstrated by the SARS-CoV-2 (COVID-19) pandemic. RNA recombination is required during normal CoV replication for subgenomic mRNA (sgmRNA) synthesis and generates defective viral genomes (DVGs) of unknown function. However, the determinants and patterns of CoV recombination are unknown. Here, we show that divergent {beta}-CoVs SARS-CoV-2, MERS-CoV, and murine hepatitis virus (MHV) perform extensive RNA recombination in culture, generating similar patterns of recombination junctions and diverse populations of DVGs and sgmRNAs. We demonstrate that the CoV proofreading nonstructural protein (nsp14) 3-to-5 exoribonuclease (nsp14-ExoN) is required for normal CoV recombination and that its genetic inactivation causes significantly decreased frequency and altered patterns of recombination in both infected cells and released virions. Thus, nsp14-ExoN is a key determinant of both high fidelity CoV replication and recombination, and thereby represents a highly-conserved and vulnerable target for virus inhibition and attenuation.