AMEDIPLASE - Fusion Protein Technologies for Biopharmaceuticals: Applications and Challenges - page 490

33.3.2 Pharmacodynamics: In Vivo Studies

33.3.2.4 In Vivo Thrombolytic Activity of Amediplase in
Dogs The purpose of this investigation was to evaluate the
in vivo thrombolytic action of amediplase in comparison to
rt-PA in a model of coronary thrombosis in the dog. Throm-
bosis was produced through an anodal current applied to the
intima of the circumflex coronary artery. Thrombolysis
occurred in seven out of nine animals administered rt-PA
at 25mg total dose (1mg/kg as a bolus, the balance over 1 h)
and in all five animals given amediplase as a single intra-
venous bolus of 0.6 mg/kg. Mean time to thrombolysis after
amediplase was 19.6 min compared to 36.3 min after rt-PA
and coronary blood flow upon thrombolysis was greater
and more protracted after amediplase than after rt-PA
(Table 33.1). Both drugs decreased plasma fibrinogen. In
conclusion, one amediplase dose injected quickly produced
more rapid thrombolysis than the double dose of rt-PA
infused over a longer period [18].

33.3.2.1 Thrombolytic Activity in Rabbits The throm-
bolytic activity of amediplase as compared to recombinant
t-PA (rt-PA) was assessed by the well-known method of the
lysis of standard-sized preformed 125 I-fibrinogen labeled
thrombi produced in the external jugular veins of rabbits.
For both drugs, the doses were 0.4, 0.8, and 1.2 mg/kg
infused over 3 h, with saline as control.
Thrombolysis, measured as the percent reduction in throm-
bus weight, was 11% for saline, 38%, 66%, 89% for the three
doses of amediplase, respectively; and 32%, 49%, 68%for the
three doses of rt-PA. The thrombolytic activity of amediplase
was significantly higher than that of rt-PAat 0.8 and 1.2mg/kg
(p

0.01). At the highest dose (1.2mg/kg), both amediplase
and rt-PA produced a significant reduction of fibrinogen, a -2
antiplasmin, and plasminogen [14].

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33.3.2.2 Thrombolytic and Haemorrhagic Effects in
Rabbits The aim of this study was to evaluate the effects
of bolus doses of rt-PA and amediplase on (1) lysis of
radioactive thrombi (fibrinolysis); (2) accretion of new fibrin
on preexisting thrombi during fibrinolysis (thrombus
growth); (3) thrombolysis, the resultant of the two previous
processes; and (4) blood loss. A jugular vein thrombosis
model and an ear-bleeding model were adopted in rabbits.
The doses of the two test drugs were 0.2, 0.4, and 0.8mg/kg;
saline was used as control. Fibrinolysis produced by saline
was 11%, that produced by the three doses of amediplase
was 39%, 57%, 83%, respectively and that produced by rt-
PAwas 35%, 54%, 78%, respectively. Amediplase was more
effective than rt-PA at all doses in preventing the accretion of
new fibrin on the thrombi and in producing thrombolysis.
The two lower doses of amediplase and rt-PA did not
produce systemic proteolysis and bleeding. The highest
dose of amediplase produced a more intense systemic
proteolysis and bleeding than the highest dose of rt-PA [15].

33.3.3 Pharmacokinetics

33.3.3.1 Pharmacokinetics of Amediplase in Monkeys
Monkeys were chosen for kinetic studies because they are
considered closer to humans than other mammals for hae-
mostasis. Six cynomolgus monkeys were used. Amediplase
was administered as a bolus at the dose of 0.5mg/kg. Results
show that kinetics of amediplase in monkeys are signifi-
cantly slower than those of t-PA: the amediplase- a and
amediplase- b half-lives were 6 and 47 min, respectively,
as opposed to the reported values of < 2.5 and 12-20min for

t-PA [19].

33.3.3.2 Pharmacokinetics of Amediplase in Rats
Amediplase was administered as i.v. bolus of 0.3, 1, 3, or
6mg/kg to male and female rats. The plasma concentration
of amediplase decreased biphasically (Figure 33.4). Very
high, dose-related, area under curves (AUCs) were meas-
ured. In the rat, the t 1/2 a was between 4 and 8 min and the
t 1/2 b between 36 and 91 min, thus longer than literature
values of alteplase. The volume of distribution values, V c
(31-49 mL/kg), V ss (38-93 mL/kg), and V area (342-
439ml/kg), strongly suggest that amediplase is mainly
distributed in the central compartment (blood). The systemic
clearance was in the range 2.18-7.67 mL/min/kg, suggesting
a moderate hepatic metabolism [20].

33.3.2.3 Fibrinolytic Activity of Amediplase in
Rats The fibrinolytic activity of amediplase has been
studied in a model of arterial thrombosis induced by
FeCl3 in rat carotid artery. Amediplase was administered
as a single bolus administration via the jugular vein at
dosages of 1, 3, or 6mg/kg. A dose-dependent fibrinolytic
effect was observed. At the highest dose, there were 87.5%
of animals fully reperfused, and this was achieved between
60 to 85min following the bolus administration and lasted
up to 105min [16]. In this experimental model, thrombolytic
activity and time to carotid patency were similar for ame-
diplase (6mg/kg) or tenececteplase (6mg/kg) both admin-
istered as a bolus [17]. When bigger thrombus was obtained
by increasing the time of occlusion, percentage of animals
achieving complete reperfusion was slightly higher with
amediplase than with tenecteplase [17].

TABLE 33.1 Thrombolytic Activity of Amediplase in Dogs

n Amediplase n rt-PA

Time to achieve
reperfusion (min)

5 19.6 4.3 7 36.3 6.3

Time to achieve
reocclusion (min)

4 124.3 18.6 7 64.4 20.2

18 See Reference [18].