Recombinant factor Xa inhibitor antidote (PRT064445) mediates

16 Pages·2012·0.56 MB·English

Recombinant factor Xa inhibitor
antidote (PRT064445) mediates
reversal of anticoagulation
through reduction of free drug
concentration: A common
mechanism for direct factor Xa
inhibitors

A. Hutchaleelaha, G. Lu, FR. Deguzman,
MJ. Karbarz, M. Inagaki, S. Yau, PB.
Conley, U. Sinha, SJ. Hollenbach
Portola Pharmaceuticals, Inc,
South San Francisco, United States of America
Disclosures for Hutchaleelaha et al
All authors are employees of Portola Pharmaceuticals, Inc.
2
r-Antidote: a recombinant human fXa variant
lacking the membrane binding Gla-domain and
active site serine

Light Chain Heavy Chain
S419A S419A
Gla EGF1,2 Inactive EGF1,2
S S Catalytic Domain S S
fXai PRT064445

PRT064445 (r-Antidote)
• Unable to assemble into the prothrombinase complex and cleave
prothrombin
• Retained binding ability for all fXa inhibitors
3
r-Antidote has a high affinity for fXa inhibitors
100
Control
n) 2.5nM Rivaroxaban
mi 75
5.0nM Rivaroxaban
/
D
O 7.5nM Rivaroxaban
m
(
50
y
t
i
v
i
t
c
a
25
a
X
F
0
0 50 100 150 200 250 300
PRT064445 (nM)
Inhibitor r-Antidote fXa
Kd (nM) Ki (nM)
Rivaroxaban 1.53 0.40*
Apixaban 0.58 0.08*
Betrixaban 0.53 0.12
,
*Perzborn at al J Thromb Haemost 2005;3:514

4 Pinto et al J Med Chem 2007; 50:5339
r-Antidote completely reverses the activity of
rivaroxaban in vitro and ex vivo
In vitro in plasma Ex vivo in rat model
5.0 Infusion of Rivaroxaban Bolus + Infusion of PRT064445
125
Human plasma+rivaroxaban (230nM) (0.25 mg/kg/hr) (4 mg + 4 mg/hr)
Rat plasma +rivaroxaban (230nM) D 4.5
Vehicle+Vehicle (n=4)
S
100 + * Rivaroxaban+Vehicle (n=4)
)R 4.0 Rivaroxaban+PRT064445 (n=4)
)
% N
75 I *
( ( 3.5
a T
X P

f d 3.0
i- 50 o
t o
n
A lB
2.5
e
25 lo
h
W 2.0
0
1.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 3300 3355 60 9900
PRT064445 (M) Time (min)
*P-value  0.01 (PRT064445vs. Rivaroxaban Alone)
ISTH 2009
5
Free drug concentration of rivaroxaban was well
correlated with reversal of PD parameter

5.0 Infusion of Rivaroxaban Bolus + Infusion of PRT064445
(0.25 mg/kg/hr) (4 mg + 4 mg/hr)
D 4.5
Vehicle+Vehicle (n=4)
S
+ * Rivaroxaban+Vehicle (n=4)
R) 4.0 Rivaroxaban+PRT064445 (n=4)
N
*
(I 3.5
T
P
d 3.0
o
o
Bl
e 2.5
ol
h
W 2.0
1.5
0 3300 3355 60 9900
Time (min)
*P-value 0.01 (PRT064445vs. Rivaroxaban Alone)
1400 Rivaroxaban Alone: Total
an 1200 RRiivvaarrooxxaabbaann +A l(o4n+e4 :) Umngb PouRnTd0 64445: Total
ab Rivaroxaban + (4+4) mg PRT064445: Unbound Infusion of
oxL) 1000 PRT064445
rm
vag/ 800
Rin Infusion of
d c ( 600 Rivaroxaban
nn
uo
oC 400
nba
Um 200
and Plas 20
al 15
ot 10
T
5
0
0 10 20 30 40 50 60 70 80 90
Time (min)
6
Has free drug concentration been used as a
surrogate marker for pharmacodynamic activity?
• Reversal of digoxin toxicity by decreasing free digoxin
concentration with digoxin-specific Fab antibodies
7
Pharmacokinetic Aspects of Digoxin-Specific Fab
Therapy in the Management of Digitalis Toxicity
Michael R Ujhelyi1 and Sylvie Robert2
Clin Pharmacokinet 28(6):483-493 1995
Within minutes of Fab dosing,
there is a 10- to 30-fold increase
in total digoxin conc and free
digoxin conc decreases from 75-
90% to 0-5%
When free concentration
rebounds beyond 0.8 ug/mL,
signs and symptoms of digoxin
reintoxication return in some
patients
8
Apixaban
4.0 Infusion of Apixaban Bolus + Infusion of PRT064445
(0.5 mg/kg/hr) (6 mg + 6 mg/hr)
* Apixaban + Vehicle (n=5)
3.5 Vehicle + Vehicle (n=5)
D Apixaban + PRT064445 (n=5)
S
 *
NR) 3.0 *
T (I
P
d
o
o
Bl 2.5
e
ol
h
W
2.0
1.5
0 3300 3355 60 90
Time (min)
Apixaban Alone: Total
* p-Value < 0.01 Apixaban + PRT064445 vs Apixaban alone
Apixaban Alone: Unbound
Apixaban + (6+6) mg PRT064445 : Total
Apixaban + (6+6) mg PRT064445: Unbound
Infusion of PRT064445
n
a
b
aL) 1000 Infusion of
pixm Apixaban
Ag/
d (n
nc
un
oo
bC
Una 100
d m 10
ns
al aPla
t 1
o
T
0.1
0 10 20 30 40 50 60 70 80 90 100 110 120
Time (min)
9
Betrixaban
Betrixaban Alone: Total
Betrixaban Alone: Unbound
Betrixaban + (6+9) mg PRT064445: Total
Betrixaban+ (6+9) mg PRT064445: Unbound
10000
Infusion of PRT064445
n
a
b
xaL) 1000 Infusion of
rim Betrixaban
Betng/
nd c (
ouon 100
bC
na
Um
d s
na
al aPl 10
ot
T
1
0 10 20 30 40 50 60 70 80 90 100 110 120
10
Time (min)