The present study demonstrated that treatment with edoxaban can achieve long-term thrombolysis as a single agent without compromising the hepatic reserves. We considered edoxaban, which is easy to administer and has a strong therapeutic effect, as a candidate primary agent for the treatment of PVT.
PVT is a major complication of cirrhosis and can be life threatening. However, there has been debate as to whether anticoagulation therapy should be administered, because approximately 40% of portal vein thrombi in patients with cirrhosis spontaneously dissolve17. Factors associated with spontaneous shrinkage of cirrhotic PVT include the absence of large collateral blood vessels (> 9 mm in diameter) and a low FIB-4 index 18. However, the recurrence rate is high, estimated at 30%19. Recently, anticoagulation therapy was shown to reduce the risk of cirrhosis-related complications and improve survival in patients with cirrhotic PVT20. Therefore, PVT should eventually be treated with therapeutic interventions.
Previously, anticoagulants, mainly heparin and warfarin, were used to treat PVT, and a certain degree of efficacy has been reported1. Heparin is an effective treatment that requires continuous injections, which are impractical for patients. Warfarin can be administered orally and can be discontinued quickly because antagonists are available. However, warfarin clearance is delayed in patients with cirrhosis because it depends on cytochrome P450-dependent pathways.
In addition, patients with a high PT-INR at baseline may be difficult to monitor21. It is also difficult to determine the optimal PT-INR value. AT III is the only drug approved for insurance in Japan for PVT, with an AT III activity below 70%, and its efficacy and safety are assured22. However, it is only a replacement therapy, and there is a high possibility of PVT recurrence due to a renewed decrease in AT III activity after treatment discontinuation. Continuous supplementation with AT III is not recommended because it is administered intravenously daily, requires hospitalization, and is expensive. In conclusion, AT III should only be used for initial treatment, and other maintenance therapies should be considered for relapse prevention.
Danaparoid sodium is a low-molecular-weight heparinoid (molecular weight: 5,500). An increasing number of reports have indicated that anticoagulation with danaparoid sodium is effective and safe for PVT in patients with cirrhosis10. It is characterized by a very high anti-Xa/thrombin activity ratio (22-fold; standard heparin is 1-fold) and a considerably long half-life in the blood (20 h; standard heparin is 0.5–1 h). Similar to standard and low-molecular-weight heparin, it exerts its anticoagulant activity in an AT III-dependent manner, primarily by blocking factor Xa. In Japan, it is only indicated for disseminated intravascular coagulation; however, in Europe, it is frequently used for heparin-induced thrombocytopenia and deep vein thrombosis, and good results have been reported. Danaparoid sodium must be administered intravenously, making it difficult to continue its use in outpatient settings. Furthermore, shipments of sodium danaparoid have recently been suspended, and there is no indication that the supply will resume. In addition, owing to its high recurrence rate, the question of how long PVT treatment should be continued is important. Currently, the American Association for the Study of Liver Diseases guidelines recommends anticoagulation for at least 3 months to allow recanalization and avoid worsening of intestinal infarction and portal hypertension23. Long-term maintenance treatment after the disappearance of PVT may be necessary to prevent recurrence. At the same time, close attention should be paid to serious complications, such as gastrointestinal bleeding.
Edoxaban is a direct-type Xa inhibitor with predictable pharmacokinetics13, 14. Edoxaban is rapidly absorbed, reaching a peak blood concentration in 1 to 2 hours. Approximately 50% of the absorbed dose is excreted by the kidneys15 and is not subject to hepatic metabolism16. Two recent studies24, 25 concluded that edoxaban (administered once daily after initial treatment with heparin) could be an alternative to warfarin in patients with venous thromboembolism. In these studies, the therapeutic effect of edoxaban was comparable with that of standard high-quality therapies. Edoxaban has also been reported to cause significantly less bleeding in a wide range of patients with venous thromboembolism, including those with severe pulmonary embolism, suggesting that it may also be useful in patients with Child-Pugh B and C cirrhosis. The increased pharmacodynamic efficacy of another DOAC, reversaloxaban, in cirrhotic patients with moderate liver damage classified as Child-Pugh B and C was another reason for selecting edoxaban26. Edoxaban has been reported to be effective as maintenance therapy after danaparoid sodium administration27. We conducted this study to determine whether edoxaban is useful as a single agent when danaparoid sodium is not readily available and concluded that edoxaban is useful as a single agent in the treatment of PVT. The edoxaban dose is set at 60 mg daily if the patient weighs more than 60 kg and at 30 mg daily if the patient weighs less than 60 kg, has impaired renal function, or is taking concomitant medications that require caution. However, because the frequency of gastrointestinal bleeding was significantly lower with a 30 mg edoxaban regimen than with warfarin, we uniformly started with 30 mg in this study28. In this study, the 30 mg edoxaban regimen was sufficiently effective for PVT, with no fatal adverse events. Edoxaban is a potent inhibitor of factor Xa without mediating AT III and can achieve a stable therapeutic effect in patients with chronic liver disease with decreased AT III levels16. In addition, since there is no need to monitor PT-INR, and the hassle of intravenous infusion is avoided, it is an ideal treatment for long-term maintenance, with a lower patient burden. An additional advantage of edoxaban is that it can be administered as an outpatient drug. Sarcopenia is a problem in patients with chronic liver diseases such as cirrhosis and hepatocellular carcinoma29, 30, and easy hospitalization may contribute to sarcopenia. Based on this study, we suggest starting edoxaban 30 mg monotherapy for PVT therapy, including acute onset, outpatients, patients with chronic PVT, patients with concomitant portal vein tumor plugs, and patients at a high risk of bleeding.
This study had certain limitations. First, this was a retrospective study with a limited number of participants. In addition, because the number of cases was small, there was variability in background factors. A large-scale study is needed to determine whether the therapeutic effect of edoxaban is truly significant. However, owing to its simplicity, edoxaban monotherapy may be an effective treatment option for PVT.
In conclusion, edoxaban monotherapy was effective for the treatment of PVT in patients with cirrhosis. Edoxaban monotherapy may improve the prognosis of patients with cirrhosis by achieving thromboprophylaxis without compromising reserves, is easily initiated in an outpatient setting, and may be an ideal first choice treatment for PVT.