The ex-vivo potency of Edoxaban in patients with cirrhosis

The liver is the site of synthesis for many proteins involved in hemostasis.
Consequently, patients with end-stage liver disease (i.e., cirrhosis) acquire
multiple and complex alterations in their hemostatic system. Recent insights in
consequences of the hemostatic changes in patients with cirrhosis have
indicated a balanced, but unstable hemostatic system in these patients with a
risk for both bleeding and thrombosis. Prevention and treatment of thrombotic
events are a particular challenge due to a frequently prolonged baseline
international normalized ratio (INR) and substantially decreased levels of
antithrombin, impeding correct dosing and monitoring of respectively vitamin K
antagonists (VKA) and heparins. There is very limited clinical experience with
the new-generation direct oral anticoagulants (DOAC) in patients with
cirrhosis, as these patients were excluded from all clinical trials with these
new agents. However, DOACs have potential advantages over other anticoagulants,
such as the oral route of administration, the lack of requirement of laboratory
monitoring, and the wider therapeutic window, which has resulted in increasing
interest from the hepatology community.

Currently four DOACs are registered in Europe for the use of prevention or for
the treatment of venous thrombo-embolism and the prevention of cerebrovascular
events in patients with non-valvular atrial fibrillation. Edoxaban was found to
be non-inferior to warfarin in the prevention of CVE in atrial fibrillation and
symptomatic thrombo-embolism. Besides, Edoxaban shows a more favourable risk
profile with 2.75% incidence of major bleedings versus 3.43% when compared to
Warfarin.

None of the DOACs is officially registered for the cirrhotic population.
Nevertheless, a growing number of patients with cirrhosis are treated with
these new drugs, despite no clinical information on safety and efficacy.
Intagliata et al presented a retrospective cohort in which 20 cirrhotic
patients were succesfully treated with factor Xa inhibitors. The number of
reported bleeding events was similar between patients treated with DOACs and
patients treated with traditional anticoagulants. A number of case reports and
a report from the Vascular Liver Disease Group (a European consortium on
vascular liver diseases) underline the findings of Intagliata.
Cautious use of some factor Xa inhibitors within mild to moderate cirrhosis is
recommended by the manufacturers. The route of clearance of Edoxaban is mainly
renal (50%). The remainder of the drug is cleared through hepato/biliary
excretion and a minor part (<4%) through CYP450 metabolisation. Therefore, the
main concern regards potentially higher plasma concentration of the
anticoagulant due to drug accumulation which will increase bleeding risk. In a
small group of patients with Child Pugh A and B cirrhosis a single gift of
Edoxaban 15 mg was administered. The pharmokinetics and pharmacodynamics of
Edoxaban were compared to a cohort of healthy matched controls. The overall
exposure of Edoxaban was similar between the patients with Child Pugh B disease
and their matched healthy controls.

In addition to concerns on drug accumulation, in vitro studies performed by our
laboratory showed profoundly altered anticoagulant effects of both the
traditional anticoagulants and DOACs in patients with cirrhosis. In general,
pharmacokinetic studies report plasma levels of anticoagulant drugs, or assays
indirectly measuring plasma levels of drug (such as anti-Xa assays) in
combination with routine diagnostic tests of coagulation such as the
prothrombin time (PT) or activated partial thromboplastin time (APTT). None of
these tests, however, truly assesses the extent of the anticoagulant effect.
Routine diagnostic tests of coagulation universally fail to test the hemostatic
capacity of a blood sample, as these tests are only senisitive for plasma
levels of procoagulant proteins. This is a particular concern in patients with
liver diseases who have complex alterations in both pro- and anticoagulant
pathways. The results of routine diagnostic tests of hemostasis, therefore have
long been misinterpreted. We and others have used the thrombin generation test,
a research tool developed in the Netherlands, which is now distributed by a
large hemostasis diagnostics firm, to better assess the hemostatic status of
patients with cirrhosis. The thrombin generation test has many advantages over
tests such as the PT and APTT, but the main reason for us to use this test is
that it gives an accurate representation of the balance between pro- and
anticoagulant factors. A disadvantage of the thrombin generation test is that
it is cumbersome and therefore not yet ready for clinical use. In addition, the
between laboratory variation in the test is high, although the within
laboratory variation is excellent, also in our own experience.
Thrombin generation tests have been used to estimate the efficacy of reversal
strategies for DOACs. Specifically, it has been shown that the ex vivo
anticoagulant effect of Rivaroxaban and Dabigatran as measured by thrombin
generation tests is reversed by prothrombin complex concentrates or recombinant
factor VIIa.

We and others have shown that thrombin generation in patients with cirrhosis is
equal or even better than that in healthy individuals, which contrasts sharply
with the results from PT and APTT tests which are prolonged in patients.
Results of the thrombin generation test have been instrumental in changing
concepts of management of hemostatic disorders in patients with liver disease,
and have led to the realisation that many patients with cirrhosis require
anticoagulant therapy despite the fact that the PT/APTT suggest that these
patients are *auto-anticoagulated*.

The increasing use of anticoagulant drugs in patients with liver disease has
led to yet unsolved clinical questions on the optimal use of these drugs in
these patients. Although patients with cirrhosis appear to have intact thrombin
generating capacity, their hemostatic system is tremendously altered, which may
have consequences for the functionality of pro- and anticoagulant drugs.
Indeed, using thrombin generation tests it was demonstrated that low molecular
weight heparin is more potent in plasma from patients with cirrhosis compared
to healthy individuals. Subsequently, we performed a systematic in vitro study
assessing potential potency changes of all clinically used anticoagulants in
patients with cirrhosis. We showed that some anticoagulants, when added to
plasma in vitro, had an increased and some had a decreased anticoagulant effect
in plasma from patients with cirrhosis as compared to control plasma,
Specifically, the Xa inhibiting DOACs were shown to be less potent in patients
with cirrhosis whereas IIa directed DOACs showed an increased potency.
Would these potency differences be clinically relevant, dose-adjustments for
patients with cirrhosis may be required. However, before embarking on clinical
studies testing (dose-adjusted) clinical effects of DOACs in patients with
cirrhosis, it is vital to assess whether the potency differences we have
observed in vitro, are also present when drugs are actually administered to the
patient. Importantly, our previous in vitro studies did not account for altered
clearance and metabolisation of the drugs in patients with cirrhosis.

In this study we therefore want to provide the clinical information on the
ex-vivo potency of Edoxaban by comparing thrombin generation tests before and
after drug administration of cirrhotic patients to matched healthy controls.
The potency of Edoxaban will be estimated by calculating the percentual
decrease in thrombin generation following drug administration.

Primary Objective: To assess the ex-vivo anticoagulant potency of Edoxaban in
patients with Child Pugh A/B cirrhosis, by means of percentual changes in
ex-vivo thrombin generation from baseline compared to steady state. These
results will be compared with similar measurements in healthy matched controls.

Secondary Objective: The secondary objective of this trial is to determine the
safety of the anticoagulant drug Edoxaban in patients with cirrhosis.

This study has a case controlled interventional design in which patients with
cirrhosis will be on a daily regimen of 60 mg of Edoxaban during one week.
Several samples will be taken to generate knowledge on the pharmacodynamics of
Edoxaban and to assess the safety and the potency of the drug.
We will include sixteen patients with mild to moderate cirrhosis (Child Pugh A
or B) and their results will be compared to sixteen matched healthy controls.
Blood samples will be taken before and 2 hours after the first ingestion at day
3 days and day 7 also 2 hours after ingestion.
Patients with cirrhosis will take the study medication when they are in the
hospital as in-patients for a screening program to determine eligibility for
liver transplantation.

Since HIV-positivity is an exclusion criterium each subject will be tested
prior to enrolment.

Overview of planned interventions (this will be performed when the subjects are
admitted for their screening programme for liver transplantation):

1. Oral administration of Edoxaban 60 mg once a day for 7 days.
2. Daily Assesment of vital parameters
3. Thorough physical examination prior to the first gift of Edoxaban and at day
3 and day 7.
4. Blood samples (18 ml, with sodium citrate as anticoagulant) will be taken at
set time points:
a. 30 minutes before the first gift of Edoxaban
b. 120 minutes after the first gift
c. 120 minutes after the third gift
d. 120 minutes after the seventh gift

It is possible that study patients are planned to be admitted for screening for
liver transplantation. In this case the study can take place during their
admittance. In other cases patients will enter the study as outpatient
participants. Study controls will then partially take place in the UMCG and at
the participants home. Overview of the location and duration of the controls
for outpatient participants:

* Control 1 at the UMCG; 2.5 hrs
Two blood withdrawals (before and after the first gift of edoxaban)
Physical examination
First gift of edoxaban

* Control 2 at the participants* home on day 3; +/- 20 min
Physical examination
Assessment of vital parameters
One blood withdrawal

* Control 3 at the participants* home on day 7; +/- 20 min
Physical examination
Assessment of vital parameters
One blood withdrawal

When possible we will combine the first control together with an outpatient
clinic appointment.

Due to the delicate balance of the haemostasis within patients with cirrhosis a
thrombotic event occurs more frequently compared to the general population.
Currently there is sufficient experience with VKA*s and LMWH as anticoagulant
treatment for thrombosis in cirrhosis. Unfortunately VKA*s need to be monitored
and LMWH have an inconvenient route of administration. DOAC can be taken orally
once a day without the necessity for routine monitoring of the desired dosage.
In the general population DOAC have shown to have a similar and in some cases
even a more safe risk profile than VKA*s. The first in vitro studies in
cirrhotics did not show a difference in the pharmacodynamics between healthy
subjects and subjects with cirrhosis. Next to this the clearance is mainly
renal so a higher steady state or drug concentration is not to be expected.
Therefore we firmly believe that the possible risk of the treatment outweighs
the benefit of investigating the potential of DOAC in patients with cirrhosis.
Our study population might benefit themselves from these study results in the
future.