In vivo virological efficacy of monoclonal antibodies and direct antiviral agents against the SARS-CoV-2 BA.1 and BA.2 Omicron sublineages

ABSTRACT

BackgroundOmicron variant questioned the efficacy of the approved therapies for the early COVID-19. I In vitro data show retained neutralizing activity against BA.1 and BA.2 for remdesivir (RDV), molnupiravir (MLN), and nirmatrelvir/ritonavir (NRM/r), while poor efficacy for Sotrovimab (STR) against BA.2. No data about the risk of clinical failure and in vivo antiviral activity are available. Material and methodsSingle-center observational comparison study enrolling all consecutive patients with a confirmed SARS-CoV-2 Omicron (BA.1 or BA.2) diagnosis and who met eligibility criteria for treatment with RDV, MLN, NRM/r, or STR. Treatment allocation was subject to drug availability, time from symptoms onset, and comorbidities. Patients were followed through day 30. Nasopharyngeal swab (NPS) VL was measured on day 1 (D1) and D7 and was expressed by log2 cycle threshold (CT) scale. Comparisons between groups were made by Chi-square and Wilcoxon paired-test. Primary endpoint was D1-D7 VL variation. Potential decrease in VL and average treatment effect (ATE) were calculated from fitting marginal linear regression models weighted for calendar month of infusion, duration of symptoms, and immunodeficiency. Secondary endpoints were the proportion of D7 undetectable VL in NPS and clinical outcomes compared by treatment groups using a Chi-square test. ResultsA total of 521 pts received treatments (STR 202, MLN 117, NRM/r 84, and RDV 118) female 250 (48%), median age 66 yrs (IQR 55-76), 90% vaccinated; 15% with negative baseline serology. At D1, median time from symptoms onset was 3 days (2,4). 378 (73%) pts were infected with BA.1 and 143 (27%) with BA.2. D1 mean viral load was 4.12 log2 (4.16 for BA.1 and 4.01 for BA.2). The adjusted analysis showed that NRM/r significantly reduced VL compared to all the other drugs in pts infected with BA.1 while no evidence for a difference vs. MLP was seen in those infected with BA.2. MLN had comparable activity to STR against BA.1 and to NRM/r against BA.2. There was no significant difference between STR and RDV for BA.2. At D7, 35/521 (6.7%) pts had undetectable VL. Of these, 31 were infected with BA.1 [9 (9%) MLN, 7 (14%) NRM/r, 7 (8%) RDV, and 8 (5%) STR)], and only 4 with BA.2, all treated with NRM/r. After 30 days of follow-up, 9/568 pts experienced COVID-19-related clinical failure [7/226 STR (5 BA.1) and 2/87 NRM /r (2 BA.1)]. ConclusionsIn this analysis of in vivo early VL reductions, NRM/r appears to be the drug showing the greatest antiviral activity regardless of the VoC, together with MLN, although the latter limited to people with BA.2. In the Omicron era, due to the high prevalence of vaccinated people and the lower probability of hospital admission, VL decrease can be a valuable surrogate of drug activity.