Remdesivir Resistance Analyses from the Pinetree Study in Outpatients with Covid-19

ABSTRACT

Background: Remdesivir (RDV) is a broad-spectrum nucleotide analog antiviral approved for the treatment of COVID-19 in patients who are hospitalized or non-hospitalized and at risk of progressing to severe disease. Here we present SARS-CoV-2 resistance analyses from the Phase 3 PINETREE trial. Method(s) PINETREE was a double-blind, placebo-controlled trial of nonhospitalized participants (N=562) with COVID-19 and >=1 risk factor for disease progression, randomized to receive RDV or placebo once-daily for 3 days. The whole genome of SARS-CoV-2 was sequenced from nasopharyngeal swabs collected at days 1 (baseline), 2, 3, 7, and 14 using next-generation sequencing. Emergent amino acid substitutions in SARS-CoV-2 from participants treated with RDV were tested in a replicon system to determine if they alter sensitivity to RDV. Result(s) Resistance analysis criteria included all participants in the RDV group and 50% in the placebo group with viral load above the lower limit of detection for the viral load assay. Of 281 participants who met these criteria, baseline and postbaseline sequencing data were available for 115/130 (88.5%) participants in the RDV group and 129/151 (85.4%) participants in the placebo group (Table 1). Among these, emergent substitutions in Nsp12 were observed in 8/115 (7.0%) in the RDV group and 7/129 (5.4%) in the placebo group. A total of 7 emergent amino acid substitutions in Nsp12 were observed in the RDV group, but not in the placebo group. Among these, only one substitution from one participant (A376V;first detected at day 14), showed reduced in vitro susceptibility to RDV, with a half-maximal effective concentration (EC50) fold-change of 12.6 compared with a wildtype reference. The participant achieved clinical recovery by day 14. None of the other substitutions impacted RDV susceptibility (EC50 fold-change <=1.4). Emergent substitutions in Nsp8, Nsp10, Nsp13, or Nsp14 were detected in 10/115 (8.7%) of participants in the RDV group and 10/129 (7.8%) in the placebo group, with substitutions in the RDV group showing similar susceptibility to RDV as the wildtype reference (EC50 fold-change <=2.3). Conclusion(s) Overall, emergent substitutions in the SARS-CoV-2 replication complex including Nsp12 were observed with similar frequency in the RDV and placebo groups, with only one participant developing a substitution associated with reduced in vitro RDV susceptibility, indicating a high barrier to the development of RDV resistance in COVID-19 patients.