Nafamostat is hydrolysed by human liver cytosolic long-chain acyl-CoA hydrolase

Predicting the systemic exposure and lung concentration of nafamostat using physiologically-based pharmacokinetic modeling

Nafamostat has been actively studied for its neuroprotective activity and effect on various indications, such as coronavirus disease 2019 (COVID-19). Nafamostat has low water solubility at a specific pH and is rapidly metabolized in the blood. Therefore, it is administered only intravenously, and its distribution is not well known. The main purposes of this study are to predict and evaluate the pharmacokinetic (PK) profiles of nafamostat in a virtual healthy population under various dosing regimens. The most important parameters were assessed using a physiologically based pharmacokinetic (PBPK) approach and global sensitivity analysis with the Sobol sensitivity analysis. A PBPK model was constructed using the SimCYP^® simulator. Data regarding the in vitro metabolism and clinical studies were extracted from the literature to assess the predicted results. The model was verified using the arithmetic mean maximum concentration (C_max), the area under the curve from 0 to the last time point (AUC_0-t), and AUC from 0 to infinity (AUC_0-∞) ratio (predicted/observed), which were included in the 2-fold range. The simulation results suggested that the 2 dosing regimens for the treatment of COVID-19 used in the case reports could maintain the proposed effective concentration for inhibiting severe acute respiratory syndrome coronavirus 2 entry into the plasma and lung tissue. Global sensitivity analysis indicated that hematocrit, plasma half-life, and microsomal protein levels significantly influenced the systematic exposure prediction of nafamostat. Therefore, the PBPK modeling approach is valuable in predicting the PK profile and designing an appropriate dosage regimen.

Use of nafamostat mesilate for anticoagulation during extracorporeal membrane oxygenation: A systematic review

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) represents an advanced option for supporting refractory respiratory and/or cardiac failure. Systemic anticoagulation with unfractionated heparin (UFH) is routinely used. However, patients with bleeding risk and/or heparin-related side effects may necessitate alternative strategies: among these, nafamostat mesilate (NM) has been reported.

METHODS

We conducted a systematic literature search (PubMed and EMBASE, updated 12/08/2021), including all studies reporting NM anticoagulation for ECMO. We focused on reasons for starting NM, its dose and the anticoagulation monitoring approach, the incidence of bleeding/thrombosis complications, the NM-related side effects, ECMO weaning, and mortality.

RESULTS

The search revealed 11 relevant findings, all with retrospective design. Of these, three large studies reported a control group receiving UFH, the other were case series (n = 3) or case reports (n = 5). The main reason reported for NM use was an ongoing or high risk of bleeding. The NM dose varied largely as did the anticoagulation monitoring approach. The average NM dose ranged from 0.46 to 0.67 mg/kg/h, but two groups of authors reported larger doses when monitoring anticoagulation with ACT. Conflicting findings were found on bleeding and thrombosis. The only NM-related side effect was hyperkalemia (n = 2 studies) with an incidence of 15%-18% in patients anticoagulated with NM. Weaning and survival varied across studies.

CONCLUSION

Anticoagulation with NM in ECMO has not been prospectively studied. While several centers have experience with this approach in high-risk patients, prospective studies are warranted to establish the optimal space of this approach in ECMO.

Incidence and risk factors for hyperkalaemia in patients treated for COVID-19 with nafamostat mesylate

What is known and objective

Nafamostat mesylate (NM) is used clinically in combination with antiviral drugs to treat coronavirus disease (COVID‐19). One of the adverse events of NM is hyperkalaemia due to inhibition of the amiloride‐sensitive sodium channels (ENaC). The incidence and risk factors for hyperkalaemia due to NM have been studied in patients with pancreatitis but not in COVID‐19. COVID‐19 can be associated with hypokalaemia or hyperkalaemia, and SARS‐CoV‐2 is thought to inhibit ENaC. Therefore, frequency and risk factors for hyperkalaemia due to NM may differ between COVID‐19 and pancreatitis. Hyperkalaemia may worsen the respiratory condition of patients. The objective of this study was to determine the incidence and risk factors for hyperkalaemia in COVID‐19 patients treated with favipiravir, dexamethasone and NM.

Methods

This retrospective study reviewed the records of hospitalized COVID‐19 patients treated with favipiravir and dexamethasone, with or without NM, between March 2020 and January 2021. Multivariable logistic regression analysis was performed to identify the risk factors for hyperkalaemia.

Results and Discussion

Of 45 patients who received favipiravir and dexamethasone with NM for the treatment of COVID‐19, 21 (47%) experienced hyperkalaemia. The duration of NM administration was a significant predictor of hyperkalaemia (odds ratio: 1.55, 95% confidence interval: 1.04–2.31, p = 0.031). The receiver‐operating characteristic curve analysis determined that the cut‐off value for predicting the number of days until the onset of hyperkalaemia was 6 days and the area under the curve was 0.707.

What is new and conclusion

This study revealed that the incidence of hyperkalaemia is high in patients treated for COVID‐19 with NM, and that the duration of NM administration is a key risk factor. When NM is administered for the treatment of COVID‐19, it should be discontinued within 6 days to minimize the risk of hyperkalaemia.

Co-Spray Dried Nafamostat Mesylate with Lecithin and Mannitol as Respirable Microparticles for Targeted Pulmonary Delivery: Pharmacokinetics and Lung Distribution in Rats

Coronavirus disease 2019 (COVID-19), caused by a new strain of coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is spreading rapidly worldwide. Nafamostat mesylate (NFM) suppresses transmembrane serine protease 2 and SARS-CoV-2 S protein-mediated fusion. In this study, pharmacokinetics and lung distribution of NFM, administered via intravenous and intratracheal routes, were determined using high performance liquid chromatography analysis of blood plasma, lung lumen using bronchoalveolar lavage fluid, and lung tissue. Intratracheal administration had higher drug delivery and longer residual time in the lung lumen and tissue, which are the main sites of action, than intravenous administration. We confirmed the effect of lecithin as a stabilizer through an ex vivo stability test. Lecithin acts as an inhibitor of carboxylesterase and delays NFM decomposition. We prepared inhalable microparticles with NFM, lecithin, and mannitol via the co-spray method. The formulation prepared using an NFM:lecithin:mannitol ratio of 1:1:100 had a small particle size and excellent aerodynamic performance. Spray dried microparticles containing NFM, lecithin, and mannitol (1:1:100) had the longest residual time in the lung tissue. In conclusion, NFM-inhalable microparticles were prepared and confirmed to be delivered into the respiratory tract, such as lung lumen and lung tissue, through in vitro and in vivo evaluations.

Identification of human cytochrome P450 isoforms and esterases involved in the metabolism of mirabegron, a potent and selective β3-adrenoceptor agonist

1. Human cytochrome P450 (CYP) enzymes and esterases involved in the metabolism of mirabegron, a potent and selective human β(3)-adrenoceptor agonist intended for the treatment of overactive bladder, were identified in in vitro studies. 2. Incubations of mirabegron with recombinant human CYP enzymes showed significant metabolism of mirabegron by CYP2D6 and CYP3A4 only. Correlation analyses showed a significant correlation between mirabegron metabolism and testosterone 6β-hydroxylation (CYP3A4/5 marker activity). In inhibition studies using antiserum against CYP3A4, a strong inhibition (at maximum 80% inhibition) of the metabolism of mirabegron was observed, whereas the inhibitory effects of monoclonal antibodies against CYP2D6 were small (at maximum 10% inhibition). These findings suggest that CYP3A4 is the primary CYP enzyme responsible for in vitro oxidative metabolism of mirabegron, with a minor role of CYP2D6. 3. Mirabegron hydrolysis was catalyzed in human blood, plasma and butyrylcholinesterase (BChE) solution, but not in human liver microsomes, intestinal microsomes, liver S9, intestinal S9 and recombinant acetylcholinesterase solution. K(m) values of mirabegron hydrolysis in human blood, plasma and BChE solution were all similar (13.4-15.2 μM). The inhibition profiles in human blood and plasma were also similar to those in BChE solution, suggesting that mirabegron hydrolysis is catalyzed by BChE.

A method for quantifying the unstable and highly polar drug nafamostat mesilate in human plasma with optimized solid-phase extraction and ESI-MS detection: more accurate evaluation for pharmacokinetic study

An advanced quantification method was developed with solid-phase extraction (SPE) and mass spectrometry (MS) determination for nafamostat, an unstable and highly polar drug, in human plasma. For unstable drugs with an ester group, the main analytical challenge is how to avoid the ester hydrolysis, and strong acid or alkaline conditions should be excluded during sample preparation. Considering that, we developed a relatively mild method with SPE for sample preparation without strong acid and alkaline treatment, which was optimized with different pHs and salt concentrations in phosphate-buffered saline treatment. The results indicated that pH 5 gave the most efficient extraction and 0.1 M salt concentration enhanced the extraction the most, with a minor effect on MS monitoring. The extraction method effectively avoided drug hydrolysis and achieved good drug enrichment over 82.2%. The linear range of quantification was 1.25-160 ng mL(-1). The stability of the drug in sample treatment was fully validated according to the sample processing procedure, including the stability in fresh blood, mobile phase, plasma and acidic methanol, and the results indicated that the drug remained stable during the whole sample preparation. Compared with a previous isotope-labeling method, more accurate and specific quantification of plasma concentration was achieved with liquid chromatography-electrospray ionization MS determination. With use of our method, nafamostat mesilate pharmacokinetics in 30 Chinese healthy volunteers was investigated with three doses via intravenous-drip infusion. The pharmacokinetic parameters were also estimated and compared with those of Japanese volunteers (slightly lower plasma concentration and longer terminal elimination half-life for Chinese volunteers). The difference in the pharmacokinetics may be ascribed to the quantification method, because previous isotope labeling may have overestimated the parent drug.