Nafamostat Mesylate(FUT-175)

Delayed administration of nafamostat mesylate inhibits thrombin-mediated blood-spinal cord barrier breakdown during acute spinal cord injury in rats

Background: Nafamostat mesylate (nafamostat, NM) is an FDA-approved serine protease inhibitor that exerts anti-neuroinflammation and neuroprotective effects following rat spinal cord injury (SCI). However, clinical translation of nafamostat has been limited by an unclear administration time window and mechanism of action. Methods: Time to first dose of nafamostat administration was tested on rats after contusive SCI. The optimal time window of nafamostat was screened by evaluating hindlimb locomotion and electrophysiology. As nafamostat is a serine protease inhibitor known to target thrombin, we used argatroban (Arg), a thrombin-specific inhibitor, as a positive control in the time window experiments. Western blot and immunofluorescence of thrombin expression level and its enzymatic activity were assayed at different time points, as well its receptor, the protease activated receptor 1 (PAR1) and downstream protein matrix metalloproteinase-9 (MMP9). Blood-spinal cord barrier (BSCB) permeability leakage indicator Evans Blue and fibrinogen were analyzed along these time points. The infiltration of peripheral inflammatory cell was observed by immunofluorescence. Results: The optimal administration time window of nafamostat was 2-12 h post-injury. Argatroban, the thrombin-specific inhibitor, had a similar pattern. Thrombin expression peaked at 12 h and returned to normal level at 7 days post-SCI. PAR1, the thrombin receptor, and MMP9 were significantly upregulated after SCI. The most significant increase of thrombin expression was detected in vascular endothelial cells (ECs). Nafamostat and argatroban significantly downregulated thrombin and MMP9 expression as well as thrombin activity in the spinal cord. Nafamostat inhibited thrombin enrichment in endothelial cells. Nafamostat administration at 2-12 h after SCI inhibited the leakage of Evans Blue in the epicenter and upregulated tight junction proteins (TJPs) expression. Nafamostat administration 8 h post-SCI effectively inhibited the infiltration of peripheral macrophages and neutrophils to the injury site. Conclusions: Our study provides preclinical information of nafamostat about the administration time window of 2-12 h post-injury in contusive SCI. We revealed that nafamostat functions through inhibiting the thrombin-mediated BSCB breakdown and subsequent peripheral immune cells infiltration.

The TMPRSS2 Inhibitor Nafamostat Reduces SARS-CoV-2 Pulmonary Infection in Mouse Models of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has caused significant morbidity and mortality on a global scale. The etiologic agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), initiates host cell entry when its spike protein (S) binds to its receptor, angiotensin-converting enzyme 2 (ACE2). In airway epithelia, the spike protein is cleaved by the cell surface protease TMPRSS2, facilitating membrane fusion and entry at the cell surface. This dependence on TMPRSS2 and related proteases suggests that protease inhibitors might limit SARS-CoV-2 infection in the respiratory tract. Here, we tested two serine protease inhibitors, camostat mesylate and nafamostat mesylate, for their ability to inhibit entry of SARS-CoV-2 and that of a second pathogenic coronavirus, Middle East respiratory syndrome coronavirus (MERS-CoV). Both camostat and nafamostat reduced infection in primary human airway epithelia and in the Calu-3 2B4 cell line, with nafamostat exhibiting greater potency. We then assessed whether nafamostat was protective against SARS-CoV-2 in vivo using two mouse models. In mice sensitized to SARS-CoV-2 infection by transduction with human ACE2, intranasal nafamostat treatment prior to or shortly after SARS-CoV-2 infection significantly reduced weight loss and lung tissue titers. Similarly, prophylactic intranasal treatment with nafamostat reduced weight loss, viral burden, and mortality in K18-hACE2 transgenic mice. These findings establish nafamostat as a candidate for the prevention or treatment of SARS-CoV-2 infection and disease pathogenesis. IMPORTANCE The causative agent of COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), requires host cell surface proteases for membrane fusion and entry into airway epithelia. We tested the hypothesis that inhibitors of these proteases, the serine protease inhibitors camostat and nafamostat, block infection by SARS-CoV-2. We found that both camostat and nafamostat reduce infection in human airway epithelia, with nafamostat showing greater potency. We then asked whether nafamostat protects mice against SARS-CoV-2 infection and subsequent COVID-19 lung disease. We performed infections in mice made susceptible to SARS-CoV-2 infection by introducing the human version of ACE2, the SARS-CoV-2 receptor, into their airway epithelia. We observed that pretreating these mice with nafamostat prior to SARS-CoV-2 infection resulted in better outcomes, in the form of less virus-induced weight loss, viral replication, and mortality than that observed in the untreated control mice. These results provide preclinical evidence for the efficacy of nafamostat in treating and/or preventing COVID-19.

Nafamostat Mesylate Monotherapy in Patients with Moderate COVID-19: a Single-Center, Retrospective Study

Coronavirus disease (COVID-19) has spread dramatically worldwide. Nafamostat mesylate inhibits intracellular entry of the novel severe acute respiratory syndrome coronavirus 2 and is believed to have therapeutic potential for treating patients with COVID-19. In this study, patients with moderate COVID-19 who were admitted to our hospital were retrospectively analyzed. Thirty-one patients received monotherapy with nafamostat mesylate, and 33 patients were treated conservatively. Nafamostat mesylate was administered with continuous intravenous infusion for an average of 4.5 days. Compared with the conservative treatment, nafamostat mesylate did not improve outcomes or laboratory data 5 days after admission. In addition, no significant differences in laboratory data 5 days after admission and outcomes in high-risk patients were observed. The incidence of hyperkalemia was significantly higher in the nafamostat mesylate group; however, none of the patients required additional treatment. In conclusion, monotherapy with nafamostat mesylate did not improve clinical outcomes in patients with moderate COVID-19. This study did not examine the therapeutic potential of combining nafamostat mesylate with other antiviral agents, and further investigation is required. Because of the high incidence of hyperkalemia, regular laboratory monitoring is required during the use of nafamostat mesylate.

Nafamostat Mesylate for Treatment of COVID-19 in Hospitalised Patients: A Structured, Narrative Review

The search for clinically effective antivirals against the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is ongoing. Repurposing of drugs licensed for non-coronavirus disease 2019 (COVID-19) indications has been extensively investigated in laboratory models and in clinical studies with mixed results. Nafamostat mesylate (nafamostat) is a drug licensed in Japan and Korea for indications including acute pancreatitis and disseminated intravascular coagulation. It is available only for continuous intravenous infusion. In vitro human lung cell line studies with nafamostat demonstrate high antiviral potency against SARS-CoV-2 (half maximal inhibitory concentration [IC50] of 0.0022 ?M [compared to remdesivir 1.3 ?M]), ostensibly via inhibition of the cellular enzyme transmembrane protease serine 2 (TMPRSS2) preventing viral entry into human cells. In addition, the established antithrombotic activity is hypothesised to be advantageous given thrombosis-associated sequelae of COVID-19. Clinical reports to date are limited, but indicate a potential benefit of nafamostat in patients with moderate to severe COVID-19. In this review, we will explore the pre-clinical, pharmacokinetic and clinical outcome data presently available for nafamostat as a treatment for COVID-19. The recruitment to ongoing clinical trials is a priority to provide more robust data on the safety and efficacy of nafamostat as a treatment for COVID-19.

Nafamostat mesylate attenuates the pathophysiologic sequelae of neurovascular ischemia

Nafamostat mesylate, an apparent soi-disant panacea of sorts, is widely used to anticoagulate patients undergoing hemodialysis or cardiopulmonary bypass, mitigate the inflammatory response in patients diagnosed with acute pancreatitis, and reverse the coagulopathy of patients experiencing the commonly preterminal disseminated intravascular coagulation in the Far East. The serine protease inhibitor nafamostat mesylate exhibits significant neuroprotective effects in the setting of neurovascular ischemia. Nafamostat mesylate generates neuroprotective effects by attenuating the enzymatic activity of serine proteases, neuroinflammatory signaling cascades, and the endoplasmic reticulum stress responses, downregulating excitotoxic transient receptor membrane channel subfamily 7 cationic currents, modulating the activity of intracellular signal transduction pathways, and supporting neuronal survival (brain-derived neurotrophic factor/TrkB/ERK1/2/CREB, nuclear factor kappa B. The effects collectively reduce neuronal necrosis and apoptosis and prevent ischemia mediated disruption of blood-brain barrier microarchitecture. Investigational clinical applications of these compounds may mitigate ischemic reperfusion injury in patients undergoing cardiac, hepatic, renal, or intestinal transplant, preventing allograft rejection, and treating solid organ malignancies. Neuroprotective effects mediated by nafamostat mesylate support the wise conduct of randomized prospective controlled trials in Western countries to evaluate the clinical utility of this compound.