ABSTRACT
Background: Implementation of vaccination programmes has had a transformational impact on control of the SARS-CoV-2 pandemic, but the need for effective antiviral drugs remains. Molnupiravir (MPV) targets viral RNA polymerase inhibiting replication via lethal mutagenesis and nirmatrelvir (NTV) is a protease inhibitor boosted with ritonavir when given clinically. This study aimed to assess the virological efficacy of NTV and MPV individually and in combination against the SARS-CoV-2 BA.1 Omicron variant in a K18-hACE2 mouse model. Method(s): K18-hACE2 mice were inoculated intranasally with 103 PFU of SARSCoV-2 BA.1 Omicron (B.1.1.529). After 24 hours, mice were orally dosed q12H, as outlined in Figure 1. At 2, 3, and 4-days post infection mice were sacrificed, and lung samples harvested. Animals were weighed and monitored daily throughout. Subsequently, viral replication in the lung was quantified using qRT-PCR to measure total (N-gene) and sub-genomic (E-gene) viral RNA. Data were normalized to 18S for quantitation. Viral exposures expressed as Areas Under viral load Curves (AUCs) were calculated by the trapezoidal method using mean values at each timepoint. Separate studies in Syrian golden hamsters using individual drugs were also conducted, and total serum IgG was measured by ELISA at 4-days post infection. Result(s): Mice gained weight in all groups post-treatment, with no significant difference between groups. A reduction in lung viral exposure was evident in all treatment groups compared to the vehicle control dosed mice (Figure 1). Coadministration of NTV with MPV displayed a trend towards lower lung viral exposure compared to the vehicle control with ~40-and ~45-fold reduction in AUC for N-and SgE-gene assays, respectively. Dosed individually, NTV and MPV reduced viral exposure 5.7-and 7.7-fold for the N-gene assay, respectively. Differences in total serum IgG concentrations were evident between vehicle and NTV-(34-fold reduction, P=0.018), and MPV-(4.2-fold reduction, P=0.053) treated hamsters. Conclusion(s): These data show virological efficacy of NTV and MPV against the SARS-CoV-2 BA.1 Omicron variant. The combination of NTV and MPV demonstrated a lower viral RNA exposure in the lung than either drug alone, albeit not statistically significant. Initial data indicate potential immune alterations in NTV and MPV dosed hamsters. Studies to clarify the utility of NTV/ MPV combinations and further characterize the impact of antiviral therapy on IgG are warranted.
ABSTRACT
Background: Chemoprophylaxis is a critical tool for many infectious diseases, and in COVID-19 may have particular benefit for vulnerable patients that do not maximally benefit from vaccination. Nafamostat inhibits TMPRSS2, which catalyses a critical cell entry pathway for SARS-CoV-2. This study sought to assess efficacy of intranasal nafamostat against airborne transmission of SARSCoV-2 in Syrian Golden hamsters. Method(s): Male hamsters were intranasally administered water or 5 mg/kg nafamostat in water twice daily for 5 days (sentinels). One day after treatment initiation, sentinels were co-housed with an untreated hamster that was intranasally inoculated with 1 x 104 PFU of Wuhan SARS-CoV-2 (donor). Sentinels were separated from the donor by a perforated divider, allowing airflow between zones but not contact. Hamsters were weighed and throat-swabbed throughout. At day 4, all animals were culled, and lung and nasal turbinates were harvested. N-RNA was quantified relative to 18S-RNA by qPCR. A 2-way ANOVA with Bonferroni correction was applied to compare weight changes in the nafamostat group to those in controls. An unpaired t-test was used to compare viral RNA in lung and nasal turbinate between groups. Result(s): SARS-CoV-2 viral RNA was significantly lower in the nasal turbinates of nafamostat-treated hamsters compared to water-treated controls (P = 0.012;Figure 1). Within the lung, SARS-CoV-2 RNA was undetectable in the nafamostat-treated hamsters, but was detectable in the water-treated controls. Viral RNA was undetectable in the swabs of the nafamostat-treated hamsters at all timepoints, but was quantifiable in the water-treated control group from day 3. Body weight of the nafamostat-treated hamsters was significantly lower (P = < 0.001) than in the water-treated animals throughout. SARS-CoV-2 viral RNA was detectable in the donor hamsters lung, nasal turbinate and swab samples confirming validity of the experiment. Conclusion(s): This study demonstrated a protective effect of intranasal nafamostat against airborne SARS-CoV-2 transmission in Syrian golden hamsters. A phase IIa study of intravenously administered nafamostat yielded no evidence of clinical efficacy in hospitalised patients, but further investigation of intranasally administered nafamostat in a prophylactic setting may be warranted.