COVID-19 continues to be a devastating pandemic resulting in millions of deaths worldwide. Currently, multiple classes of drugs have been used to treat COVID-19, including antiviral agents, inflammation inhibitors, and convalescent plasma. However, no treatment is exceptionally effective and the availability and the cost of the agents are prohibitive.
In our study, we found Dabigatran, a protease inhibitor, dose-dependently inhibited OC43 cell entry and replication, and reduced CPE. In addition, dabigatran and Remdesivir synergistically inhibited coronavirus protein expression. These findings are important during the pandemic when effective treatment is urgently needed. Since dabigatran has been approved by FDA and its safety profile is known, it can be quickly engaged in clinical trials to save significant time avoiding going through lengthy preclinical and clinical safety testings.
Since Hoffmann et al. determined that camostat mesylate, a serine protease inhibitor, can partially block SARS-CoV cell entry mechanism 12 and significantly reduced mortality following SARS-CoV infection in animal studies 13, other serum protease inhibitors have been tried in battling this disease. Gabexate mesylate, another serine protease inhibitor, only had minimal inhibition of viral entry 16 while nafamostat mesylate, approved in Japan for acute pancreatitis and disseminated intravascular coagulation, effectively inhibits protein medication fusion in SARS-CoV-2 by targeting TMPRSS2 even at low doses (0.01 µM). 11,16 Nafamostat mesylate showed better efficacy in Calu- 3 cells with half-maximal inhibitory concentration (IC50) of 0.0022 µM, which is approximately 600-fold more potent than Remdesivir with an IC50 of 1.3 µM 17. In addition, Nafamostat has also a role in DIC treatment which is beneficial in SARS-CoV 2 patients, however, its short half-life and intravenous administration limits its use 16. In our study, we found dabigatran, another protease inhibitor, not only acts at the level of virus entry but also reduces the virus replication in the cell. It has been shown that initial lower viral inoculation resulting in fewer and shorter symptoms as well as a lower likelihood of viral shedding 18,19 while a greater viral load is related to more severe illness 20–22. Therefore, since dabigatran works at the very early stage of viral infection, it may reduce the intracellular viral load and prevent the disease and potentially decrease the severity of the disease. However, the exact mechanism of how dabigatran works on coronavirus cellular entry and replication needs further investigation. Trypsin-induced cleavage of the S protein has been reported in HCoV-229E for cell entry. 23 Additionally, studies have shown that trypsin is effective in inducing fusion of SARS-COV- infected VeroE6 cells and facilitating vial entry from the cell surface, a more efficient infection than entry through endosome24,25. In addition to trypsin and TMPRSS-2, furin, cathepsins, TMPRSS-4, or human airway trypsin-like protease have all been shown to leave coronavirus S proteins. Whether dabigatran has any effect on those proteases remains elusive and whether dabigatran affects viral protease also remains unknown.
In our study, we also showed the synergistic antiviral effect between the dabigatran and Remdesivir even at a very low drug dose. Due to the high demand for remdesivir and limited supply, medication rationalization has been utilized. In light of our findings, there is a possibility even a lower dose remdesivir can achieve effective antiviral effects when used in combination with widely available dabigatran. By doing this, even with the limited availability, remdesivir can be used in more patients to save more lives. Additionally, by using the combination of a lower dose of remdesivir and the dabigatran, the cost of the treatment will also decrease dramatically.
In addition, dabigatran, an FDA-approved anticoagulant can prevent thromboembolic events through direct anti-thrombin effects. COVID-19 is a hypercoagulable status with a significant risk of thromboembolic events. In a recent meta-analysis, the overall venous thrombotic event rate was 21%, with deep vein thrombosis rate of 20%, pulmonary embolism rate of 13%, while arterial thrombotic event rate was 2%. Thromboembolism significantly increased the odds of mortality by as high as 74% (OR, 1.74; 95%CI, 1.01–2.98; P = 0.04) 26. In another study, 71.4% of fatal cases but only 0.6% of the surviving patients had disseminated intravascular coagulation. 27 To mitigate the prothrombotic state associated with COVID-19, the International Society of Thrombosis and Hemostasis (ISTH) recommends “prophylactic dose low molecular weight heparin should be considered in all patients (including non-critically ill) who require hospital admission for COVID-19 infection” in the absence of contraindications 28 and several other consensus statements, guidelines and reviews have also made similar recommendations of thromboprophylaxis for COVID-19 patients, especially for hospitalized patients 29–31. Initially, at the start of the pandemic, several organizational guidelines suggested switching direct oral anticoagulants to unfractionated heparin low molecular weight heparin concerning possible drug-to-drug interactions, especially with antiviral agents remdesivir which inhibits CYP3A4. 31–34 However, unlike apixaban and rivaroxaban, which undergo CYP3A4 metabolism, dabigatran doesn't metabolize through the CYP450 system and therefore has few drug-drug and drug-food interactions.35 In addition, dabigatran has a very broad safety concentration, even with increased drug concentration with remdesivir, it is still likely to be a safe range. Another advantage of dabigatran is it has a specific antidote that rapidly reveres its bleeding-related complications.36 Therefore, dabigatran has been proposed as a first-line oral anticoagulation choice for COVID-19 patients with nonvalvular atrial fibrillation upon discharge.37
In conclusion. our study showed that protease inhibitor dabigatran can prevent coronaviral entry and replication and potentially can be used to treat COVID19. In addition, Dabigatran has shown synergistic inhibition on virus replication we used with the remdesivir together. This finding is significant since COVID-19 is a hyper-coagulable status with a significant risk of thrombosis event which can be simultaneously treated with the function of dabigatran, an FDA-approved anticoagulant due to its anti-thrombin effects. It is reasonable to consider a clinical trial to evaluate the effectiveness of dabigatran in treating COVID-19 patients utilizing both anti-viral and anti-thrombin effects. Additionally, the synergistic inhibitor effect of dabigatran and Remdesivir may decrease the dose needed for COVID-19 treatment, therefore, minimize the shortage of medication, provide treatment for more patients, and decrease cost.