Introduction: Apadenoson and Regadenoson protect animal and human lungs from ischemia-reperfusion or transplant injury. Our goal was to test their efficacy in attenuating hyper-inflammation and improving survival following SARS CoV-2 infection of K18-hACE2 mice and Syrian hamsters.

Method: 6-8 weeks old K18-hACE2 mice were divided into Control group receiving vehicle; Test group 1 receiving drug (Apadenoson or Regadenoson) 18hrs prior challenge with SARS-CoV-2; and Test Group 2 (Drug-delay) receiving drug with a 5hr delay post-infection (n=18/group). 1250 PFU Hong Kong/VM20001061/2020 virus was delivered intranasally. Drug was delivered subcutaneously using ALZET pumps. 6 weeks old hamsters were divided into Control group receiving Vehicle and Virus (n=4) and 2 test groups (n=5/group) receiving Apadenoson+Virus and Regadenoson+Virus. Hamsters were inoculated intratracheally with 750PFU SARS-CoV-2 WA1 strain prior treatment. Bronchoalveolar lavage fluid and serum were collected along with lungs. Plethysmography was done on days 0, 2, 4 and 7.

Results: Apadenoson administered post-infection was efficacious in decreasing weight loss (P=0.002), improving clinical score (P=0.001), and increasing survival rate in K18-hACE2 mice, i.e. 85% survival at Day 7 for Test group 2 (p<0.0002), 43% in Test group 1, and 12.5% for vehicle group. The levels of 13 cytokines/chemokines (IP-10, MIG, MCP-1, G-CSF, Eotaxin, MIP1β, VEGF, RANTES, INF-γ, IL-6, TNF-α, KC, LIF) in BALF were statistically different, with nine higher in vehicle-infected compared to uninfected controls (p<0.05). The levels of MIG, G-CSF, Eotaxin, MIP1β, VEGF, INF-γ, TNF-α, KC in Test group 2 were not significantly different from uninfected mice, except for IP-10 and MIG that were statistically higher. Notably, VEGF was lower in treated mice (p=0.011). Treated mice exhibited slower progression in weight loss without elevated cytokines and an increased chance of recovery. Increased Ang1-7 levels and decreased monocytes in BALF were also observed. Treated mice had undetectable viral titers, while all mice in Vehicle group had detectable titers. Treated mice also had lower viral burdens by IHC (p=0.0012). Viral burden on day 5 post-infection in treated mice negatively correlated with weight loss (P=0.0163). In Regadenoson studies, 42% of mice in Test group 1 survived infection compared to 6.25% in the vehicle or Test group 2. Viral titers in lungs of treated mice, and CD4+, CD8+T cells, eosinophils, and neutrophils in BALF were significantly decreased. In hamsters, significant improvement of pulmonary function parameters, Rpef and PenH, was seen with Apadenoson given post-infection. Apadenoson cleared the virus from BALF and maintained Ang1-7 levels. Both drugs decreased plasma IFN-γ levels.

Conclusion: Apadenoson attenuates inflammation, improves pulmonary function, decreases weight loss, and enhances survival rate following infection with SARS-CoV-2, supporting its use for treating COVID-19 patients.