2.1 General approach
All PBPK model development, PK and DDI simulations were performed using the population-based PBPK simulator Simcyp® version 20.1 (Certara UK Limited, Sheffield, UK). The observed clinical PK data were obtained from the literature with GetData Graph Digitizer v2.26 (http://getdata-graph-digitizer.com/). The overall workflow of the present analysis is shown in Fig. 1.
In general, the dronedarone PBPK model was developed first, with its simulated concentration-time profiles verified with clinical PK data. Second, dronedarone DDI-PBPK model as a perpetrator was established with in vitro profiles from literature, and verified with clinical PK data when CYP3A4 and p-gp substrates were co-administered with dronedarone, respectively. Third, the established model was used to predict potential DDI risks with dronedarone as a perpetrator. The information and characteristics of observed clinical data are summarized in Table 1.
Table 1
Characteristics of observed PK data used for model development and verification
Substrate
|
Inhibitor
|
Dosing regimen
|
Length of observation
|
Trial number
|
Reference
|
Dronedarone
|
/
|
Single dose of dronedarone 800 mg
|
48hour
|
NDA 022425
(ALI3180)
|
[13]
|
Simvastatin
|
Dronedarone
|
Repeated oral administration of simvastatin 40mg q24h alone or in combination with
repeated oral administrations of dronedarone 400 mg q12h
|
14days
|
NDA 022425
(INT4880)
|
[13]
|
Verapamil
|
Dronedarone
|
Repeated oral administration of verapamil 240mg q24h alone or in combination with repeated oral administrations of dronedarone 400 mg q12h
|
14days
|
NDA 022425
(INT4882)
|
[13]
|
Digoxin
|
/
|
Repeated oral administration of digoxin 0.25mg q24h alone
|
10days
|
/
|
[26]
|
|
Dronedarone
|
Repeated oral administration of digoxin 0.25mg q24h alone or in combination with repeated oral administrations of dronedarone 400 mg q12h
|
10days
|
NDA 022425
(INT5189)
|
[13]
|
Dabigatran
|
Dronedarone
|
Single dose of 150 mg dabigatran etexilate alone or in combination with a single dose of 400 mg dronedarone
|
48hour
|
NCT01306162
|
[8]
|
2.2 Dronedarone basic PBPK model development and verification
2.2.1 Dronedarone basic PBPK model development
The dronedarone PBPK model was developed based on in vitro, in vivo, and in silico data obtained from the public domain. A summary of model parameters used in the PBPK model and the referred literature are shown in Table 2.
Table 2
Summary input data for dronedarone as a substrate in Simcyp Simulator simulation
Parameters
|
Value
|
Source
|
Physiochemical parameters
|
|
|
Molecular Weight (g/mol)
|
557
|
drugbank
|
Log P
|
7.8
|
drugbank
|
Compound type
|
Monoprotic base
|
|
pKa
|
9.3
|
Djebli et al[12]
|
Hematocrit (%)
|
45
|
Simcyp library
|
B:P ratio
|
1
|
|
fup
|
0.003
|
Djebli et al[12]
|
Absorption parameters
|
|
|
ADAM model
|
|
|
fa; Ka (h− 1)
|
0.898; 0.816
|
Djebli et al[12]
|
Peff, (10− 4 cm/s)
|
1.98
|
Dissolution
|
time profile
Time (h): 0, 0.083, 0.167, 0.25, 0.33, 0.42,
0.5, 0.75, 1 and 1.5
Dissolution (%): 0, 6.6, 12.8, 28.5, 38.9, 47.7,
55.2, 75.9, 92.2 and 100
|
fuGut
|
1
|
Distribution parameters
|
|
|
mPBPK
|
|
|
Vss (l/kg)
|
10
|
Djebli et al [12]
|
Elimination parameters
|
|
|
Clearance type
|
Enzyme kinetics
|
|
In vitro metabolic system
|
Recombinant
|
|
rhCYP3A4
|
|
|
Vmax (pmol/min per pmol)
|
13.7
|
Djebli et al [12]
|
KM (mM)
|
4.2
|
fumic
|
0.003
|
Sensitivity analysis
|
rhCYP3A5
|
|
|
Vmax (pmol/min per pmol)
|
4.87
|
Djebli et al [12]
|
KM (mM)
|
3.1
|
fumic
|
0.003
|
Sensitivity analysis
|
Additional liver clearance
|
|
|
Clint(l/min per mg)
|
40
|
Djebli et al [12]
|
First, a model for oral administration of dronedarone was developed, with the physicochemical and ADME properties from drugbank (https://go.drugbank.com/) and Djebli et al [12]. The in vivo absorption of dronedarone was determined using the Advanced Dissolution Absorption and Transit (ADAM) models, with permeability and dissolution data acquired from Djebli et al. A minimal PBPK distribution model was applied, with the volume of distribution at steady state (Vss) acquired from literature [12]. Dronedarone was reported to be extensively metabolized via CYP3A4/5 [4]. Thus, the enzyme kinetics module was used to describe the in vivo clearance of dronedarone. The maximum velocity (Vmax) and Michaelis–Menten constant (Km) were acquired from the previously reported literature [12], and the fumic was obtained with sensitivity analysis.
2.2.2 Dronedarone basic PBPK model verification
The pharmacokinetics of dronedarone was simulated with the established PBPK model, with characteristics of study subjects and trial design followed the clinical trials. The simulated PK parameters and plasma concentration profiles were compared against the observed data [13]. The fold error of the main pharmacokinetic parameters (Cmax and AUC) was used to assess the predictive accuracy of the model, which referred to the ratio of the simulated to the observed values (Eq. 1). The model's fitness was evaluated with a fold error of less than 2 [14].
\(\text{F}\text{o}\text{l}\text{d}\hspace{0.33em}\text{e}\text{r}\text{r}\text{o}\text{r}=\frac{\text{p}\text{r}\text{e}\text{d}\text{i}\text{c}\text{t}\text{e}\text{d}\hspace{0.33em}\text{v}\text{a}\text{l}\text{u}\text{e}}{\text{o}\text{b}\text{s}\text{e}\text{r}\text{v}\text{e}\text{d}\hspace{0.33em}\text{v}\text{a}\text{l}\text{u}\text{e}}\hspace{0.33em}\left(\text{i}\text{f}\hspace{0.33em}\text{p}\text{r}\text{e}\text{d}\text{i}\text{c}\text{t}\text{e}\text{d}\hspace{0.33em}>\hspace{0.33em}\text{o}\text{b}\text{s}\text{e}\text{r}\text{v}\text{e}\text{d}\right)\) \(\text{o}\text{r}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\hspace{0.33em}\left(1\right)\) \(\text{F}\text{o}\text{l}\text{d}\hspace{0.33em}\text{e}\text{r}\text{r}\text{o}\text{r}=\frac{\text{o}\text{b}\text{s}\text{e}\text{r}\text{v}\text{e}\text{d}\hspace{0.33em}\text{v}\text{a}\text{l}\text{u}\text{e}}{\text{p}\text{r}\text{e}\text{d}\text{i}\text{c}\text{t}\text{e}\text{d}\hspace{0.33em}\text{v}\text{a}\text{l}\text{u}\text{e}}\hspace{0.33em}\left(\text{i}\text{f}\hspace{0.33em}\text{o}\text{b}\text{s}\text{e}\text{r}\text{v}\text{e}\text{d}\hspace{0.33em}>\hspace{0.33em}\text{p}\text{r}\text{e}\text{d}\text{i}\text{c}\text{t}\text{e}\text{d}\right)\)
2.3 Dronedarone DDI-PBPK Model development and verification
Previous studies have found that dronedarone exhibits low to moderate potential to inhibit metabolism of CYP3A, CYP2J2, as well as P-gp substrates [15]. The dronedarone DDI-PBPK model was established in a stepwise method. First, in order to establish dronedarone DDI-PBPK model as a perpetrator, in vitro inhibition data including reversible inhibition and mechanistic based inhibition (MBI) of 3A4 and 2J2, as well as inhibition of P-gp mediated efflux, were extracted from previous studies and incorporated into the basic PBPK model [12, 14, 16, 17]. Second, to calibrate the magnitude of CYP3A4 inhibition of dronedarone, the CYP3A4 inhibition parameters were adjusted so that the model generated simulations can fit the clinical data investigating the impact of repeated oral doses of dronedarone on the PK profile of simvastatin (INT4880) and verapamil (INT4882). Likewise, the magnitude of P-gp inhibition of dronedarone were calibrated with clinical data investigating the impact of repeated oral doses of dronedarone on the PK profile of digoxin (INT5189) and dabigatran (NCT01306162). In each step of the DDI-PBPK modeling, evaluation criteria were set with a fold error of AUC ratio and Cmax ratio less than 1.5. The AUC ratio and Cmax ratio were referred to as the mean AUC and Cmax in the presence of dronedarone versus the absence, respectively (Eq. 2 and Eq. 3).
\(AUC ratio=\frac{AUC with inducer or inhibitor }{AUC without inducer or inhibitor}\) Eq. 2
\({C}_{max} ratio=\frac{{C}_{max}with inducer or inhibitor}{{C}_{max}without inducer or inhibitor}\) Eq. 3
The Simcyp provided compound files of simvastatin (SV-simvastatin), dabigatran (SV-dabigatran) in were applied as substrates during dronedarone DDI-PBPK model development. The verapamil minimal PBPK model was based on Simcyp compound profile (SV-verapamil) and the study by Yamazaki et al [18]. The Simcyp provided digoxin (SV-digoxin) model was also adjusted based on a previous study to improve goodness of fit [19]. Additional model verification and calibrations were conducted for simvastatin, digoxin, and verapamil models in order to reproduce observed clinical PK data when these substrates were administered alone. Evaluation criteria of fitness of each model were the fold error less than 2 [14]. Details of PBPK modeling of simvastatin, digoxin, and verapamil are provided in supplementals.
2.4 Application of the PBPK model to predict the Drug-Drug Interaction with dronedarone as a perpetrator
The established dronedarone DDI-PBPK model was used to predict potential DDI risks with CYP3A4 and/or P-gp substrates. As an antiarrhythmic drug for atrial fibrillation treatment, dronedarone is often co-administered with anti-coagulants. Thus, effects of co-administered dronedarone on in vivo PK of apixaban, rivaroxaban were investigated based on the established model. Dosing regimen of dronedarone used in the prediction was 400mg twice daily [5]. Regimen of each substrate follows its therapeutic doses for AF management: apixaban 5mg every 12 hours, rivaroxaban 20mg every 24 hours, respectively [9]. Each substrate is co-administered with dronedarone for 14 days. Simulations of all DDI outcomes were performed using Simcyp healthy volunteers in a fasted state with 100 subjects (10 trials×10 subjects).
The apixaban and rivaroxaban PBPK models were based on the study by Otsuka et al. and were kindly provided by the authors [20]. In the study by Otsuka et al., the rivaroxaban model was validated with the DDI study results with ketoconazole, ritonavir, clarithromycin, erythromycin, verapamil, and rifampicin. The apixaban model was validated with the DDI study results with ketoconazole, diltiazem, cyclosporine, and rifampicin.
In the current study, the bioequivalence criteria for dosage adjustment were defined as the dosing regimen with which patients could achieve AUC24h or Cmax within 80.00–125.00% range of reference AUC24h or Cmax. The reference AUC24h or Cmax was defined as the AUC24h or Cmax of the anti-coagulant when it was administered alone under AF therapeutic dose. Additional simulations with alternative dosing regimens were conducted when bioequivalence was not achieved due to dronedarone co-administration.
2.5 Application of the PBPK model to predict the Drug-Drug-Disease Interaction with dronedarone as a perpetrator
To assess the impact of renal impairment on the DDI of dronedarone and apixaban/rivaroxaban, the DDIs were simulated in virtual population of renal impairment (RI). The Simcyp in-built moderate (glomerular filtration rates (eGFR) of 30–60 ml/min) and severe RI (eGFR < 30 ml/min) populations were used for simulations. The pathophysiological changes incorporated within the RI populations were reduced kidney weight, reduced hepatic CYP expression (e.g., 2C9, 2J2, 2D6, and 3A4), reduced serum albumin and hematocrit levels, altered blood flows [21, 22].
The bioequivalence criteria for dosage adjustment were the same as the abovementioned one. The reference AUC24h of the anti-coagulant was defined as the AUC24h of dronedarone when it was administered alone under its FDA approved renal-adjust dose for AF management. Additional simulations were conducted when bioequivalence was not achieved due to dronedarone co-administration.