Download Platelet inhibitory activity and pharmacokinetics of prasugrel

Platelets, June 2006; 17(4): 209–217
ORIGINAL ARTICLE
Platelet inhibitory activity and pharmacokinetics of prasugrel (CS-747)
a novel thienopyridine P2Y12 inhibitor: A single ascending dose study
in healthy humansy
FUMITOSHI ASAI1, JOSEPH A. JAKUBOWSKI2, HIDEO NAGANUMA1,
JOHN T. BRANDT2, NOBUKO MATSUSHIMA1, TAKASHI HIROTA1,
STEPHEN FREESTONE3, & KENNETH J. WINTERS2
1
Sankyo Co., Ltd., Tokyo, Japan, 2Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA,
and 3Inveresk Clinical Research Ltd., Edinburgh, Scotland, UK
(Received 13 October 2005; accepted 6 January 2006)
Abstract
We assessed the tolerability, pharmacodynamics as measured by inhibition of platelet aggregation (IPA), and
pharmacokinetics of prasugrel (CS-747, LY640315), a novel thienopyridine antiplatelet agent in healthy volunteers.
Twenty-four subjects were randomized into four groups of six in a double-blind, placebo-controlled trial. One subject in
each group received placebo and five subjects received prasugrel orally at single doses of 2.5, 10, 30, or 75 mg. The IPA,
assessed using 5 and 20 mM ADP, was periodically measured over a 7-day period by light transmission aggregometry.
Plasma concentrations for three major metabolites, R-95913, R-106583, and R-100932, were measured. There were no
serious adverse events and no clinically significant changes noted in any laboratory or clinical evaluations in any subject.
At 1 h after prasugrel 30 and 75 mg, platelet aggregation induced by 20 mM ADP was inhibited by 43.5 7.8 and
43.2 15.7%, respectively, and this inhibition was significantly greater than that following placebo (5.9 3.5%) (P < 0.05
for both doses). The degree of inhibition observed at 2 h was slightly higher with both prasugrel 30 and 75 mg (59.8 9.9
and 57.0 7.2%) and was maintained through the subsequent 22 h. At 24 h, maximal platelet aggregation induced by
20 mM ADP was reduced to 39% in all subjects receiving prasugrel 30 mg and to 38% in subjects receiving prasugrel
75 mg. Full recovery of platelet aggregation occurred between 48 h and 7 days suggesting irreversible inhibition by
prasugrel and/or its metabolites. With prasugrel 2.5 and 10 mg, there was no measurable effect on platelet aggregation
throughout the study (P > 0.05 for 2.5 and 10 mg prasugrel vs. placebo). With prasugrel 75 mg at 4 h postdose, there was a
significant increase in the mean bleeding time compared to placebo (682 vs. 161 s; P < 0.05). Prasugrel metabolites obeyed
linear pharmacokinetics and the three metabolites appeared in the plasma soon after administration, reaching maximum
levels at approximately 1 h. In conclusion, prasugrel 30 and 75 mg were well tolerated and achieved a consistently high level
of platelet inhibition with a fast onset of action.
Keywords: Prasugrel, CS-747, platelets, phase 1, thienopyridine
Introduction
It is widely recognized that platelet activation and
aggregation at sites of atherosclerotic plaque rupture
and subsequent thrombus formation underlie the
tissue ischemia and necrosis in what is collectively
known as acute coronary syndrome (ACS) [1, 2].
Further support of the central role that platelet
activation and aggregation play in occlusive arterial
disease is provided by the efficacy of platelet
inhibitory agents in ACS. Three distinct classes of
antiplatelet agents are in wide clinical use, namely
aspirin, glycoprotein IIb–IIIa (GPIIb–IIIa) antagonists, and the adenosine 50 -diphosphate (ADP)
receptor antagonists of which the most commonly
used is clopidogrel. Aspirin reduces the risk of a
serious vascular event in a wide range of atherosclerotic vascular disease [3]. Moreover, antiplatelet
drugs acting through other pathways such as the
final common pathway of GPIIb–IIIa or the platelet
Correspondence: Joseph A. Jakubowski, PhD, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA. Tel: 1 317 276 9036.
Fax: 1 317 433 1996. E-mail: [email protected]
yThis study was conducted at Inveresk Clinical Research, Ltd., Edinburgh, Scotland, UK.
ISSN 0953–7104 print/ISSN 1369–1635 online ß 2006 Taylor & Francis
DOI: 10.1080/09537100600565551
210
F. Asai et al.
ADP receptor have also provided improved clinical
outcomes in patients with non ST-elevation ACS
and those undergoing percutaneous coronary intervention (PCI) [4–7].
Ticlopidine and clopidogrel are thienopyridine
prodrugs which following oral administration are
metabolized to an active sulfhydryl form that binds
to and irreversibly antagonizes the P2Y12 class of
platelet ADP receptor [8]. Where approved, clopidogrel is the thienopyridine of choice due to its more
favorable safety profile compared to ticlopidine. The
effectiveness of clopidogrel reflects its ability to block
platelet activation and aggregation induced by platelet-derived ADP released at sites of plaque rupture.
However, several limitations of clopidogrel have
recently been discussed including inter-patient
variability in antiplatelet effects and a relatively slow
onset of action [9–12].
More recently a novel thienopyridine P2Y12 antagonist, prasugrel (CS-747, LY640315), has been
identified and profiled [13–16]. Preclinical studies
indicate that like clopidogrel, prasugrel is a prodrug
that requires metabolic activation to an active
metabolite [13]. In vivo and ex vivo studies demonstrate that following oral dosing of prasugrel there
is a rapid and potent inhibition of ADP-induced
platelet activation and aggregation [13–15]. These
early studies demonstrated that the dose required
to achieve a given degree of platelet inhibition or
inhibition of thrombus formation was approximately
one-tenth and one-hundredth that of the dose of
clopidogrel and ticlopidine, respectively. The current
report describes the first experience of prasugrel in
man in a study that examined the safety, tolerability,
pharmacokinetics, and pharmacodynamics, as
measured by inhibition of platelet aggregation
(IPA), of prasugrel in a single ascending dose study.
consisted of: medical history, complete physical
examination and vital signs, 12-lead electrocardiography (ECG) recording, hematology, coagulation,
clinical chemistry and urinalysis, urine screening for
drugs including drugs of abuse, fecal occult blood
examination, bleeding time, examination for petechiae, and Von Willebrand factor and arachidonic
acid-induced platelet aggregation. All subjects were
screened within 14 days prior to randomization.
Exclusion criteria included a history of important
bleeding disorders, a personal or family history of
coagulation or bleeding disorders, reasonable suspicion of vascular malformations, or abnormal coagulation values at screening. No medications other than
study drugs were permitted during the study except
those deemed necessary by the clinical investigator/
study director/supervising physician to treat adverse
events. Aspirin and nonsteroidal anti-inflammatory
drugs were excluded.
Treatment administered
Prasugrel was manufactured by Ube Industries Ltd.
(Tokyo, Japan) and plain tablets containing 2.5, 5, or
10 mg as free base were formulated by Sankyo Co.
Ltd. (Tokyo, Japan). Twenty-four male volunteers
were randomized into four groups. Each group
consisted of six subjects, of whom one subject
received placebo and five subjects received prasugrel
at doses of 2.5, 10, 30, or 75 mg. Prasugrel was
administered to each fasting subject by the oral route,
with 200 mL of water. Each volunteer remained in
the clinic for two nights, and was discharged 24 h
postdose. If any safety parameters did not meet
predefined criteria, subjects were obliged to return at
48 h postdose; otherwise, all the subjects returned for
an outpatient visit at day 7 and again at day 14
if required.
Methods
A randomized, double-blind, placebo-controlled,
single oral ascending dose study was undertaken in
healthy subjects. A primary objective was to determine the safety and tolerability of prasugrel, whereas
a secondary objective was to assess the pharmacodynamics and pharmacokinetics of prasugrel. The
study was conducted at Inveresk Clinical Research,
Ltd., Edinburgh, Scotland. The Inveresk Research
Ethics committee approved the protocol. Signed
informed consent was obtained from each subject
and the study was conducted in accordance with
the provisions of the Declaration of Helsinki.
Subjects
Subjects were male volunteers, aged 18–50 years with
no clinically important physical findings or abnormalities in laboratory results, including platelet function tests, at screening. The screening examination
Safety
Safety assessments performed at various timepoints
throughout the study included measurement of vital
signs, ECG, hematology, clinical chemistry, coagulation, urinalysis, fecal occult blood, fundoscopy, and
examination for petechiae. Adverse events were
recorded and monitored throughout the study.
Pharmacodynamic measurements
Prasugrel was assessed for its effects on human
platelet function by monitoring light transmission
platelet aggregation using a BioData PAP-4 aggregometer. Venous blood samples were collected into
one-tenth volume 3.8% citrate. Platelet-rich and
platelet-poor plasma were prepared using differential
centrifugation. No adjustments to the platelet count
were performed. Subjects were initially screened
to confirm normal platelet function (see following)
Single oral doses of prasugrel in healthy subjects
using ristocetin (1.2 mg/mL) and sodium arachidonate (0.75 mM). These screening procedures were
qualitative assessments to exclude Von Willebrand’s
disease and aspirin ingestion, respectively.
All platelet aggregation studies were completed
within 3 h of sample collection.
Platelet aggregation was determined at predose, 1,
2, 4, 8, and 24 h and day 7 postdose. Samples for
platelet aggregation were also drawn at 48 h in
the prasugrel 30 and 75 mg dose groups. The maximum percent aggregation response (MPA) to
ADP (5 and 20 mM), and collagen (2 mg/mL) was
recorded over a 4 min monitoring period. Inhibition
of aggregation (IPA) was
defined as follows:
[1–(MPAt MPA0)] 100%, where MPA0 ¼ MPA
at baseline and MPAt ¼ MPA at given timepoint (t).
Bleeding time using the Ivy–Nelson method [17]
was determined at screening, predose, 4 and 24 h
postdose and at the 7-day follow-up.
Pharmacokinetic measurements
The plasma concentration of three major inactive
prasugrel metabolites, R-95913, R-106583 and
R-100932 (Figure 1), were measured for evaluation
of absorption and elimination of the parent drug and
its metabolites. At the time the study was conducted,
211
a validated analytical method for the active metabolite of prasugrel (R-138727) [18] was not available.
Blood samples were collected during the course of
the study at the following times: predose (0), 0.5, 1,
1.5, 2, 4, 6, 8, 12, and 24 h postdose. Blood (10 mL)
was collected from each subject via a cannula or by
repeated venipuncture into lithium heparin tubes.
After centrifugation, plasma was divided into two
different tubes and stored at 20 C.
A validated LC–MS/MS method was developed
for simultaneous quantification of the three major
inactive metabolites in human plasma [19]. The
metabolites were analyzed following solid-phase
extraction. No endogenous component interfered
with the quantification. The lower limit of quantification for the three metabolites was 1.56 ng/mL in
human plasma.
Statistical analyses
Descriptive statistics generated using SAS (v 6.07)
were used to summarize demographics, laboratory
parameters, platelet aggregation, bleeding times, and
adverse events by dose group. Dunnett multiple
comparisons tests were used to evaluate changes
in bleeding times. A non-compartmental model
was used to generate pharmacokinetic parameter
O
O
N
O
N
O
S
F
CH3S
F
*R-100932
Prasugrel
O
O
N
O
S
N
HOOC
F
F
HS
R-138727 (active metabolite)
*R-95913
O
HOOC
CH3S
N
F
*R-106583
Figure 1. Pathways of prasugrel metabolism. R-138727 was not measured in this study but has been shown to be the pharmacologically
active metabolite [18]. Metabolites measured in study. Figure does not illustrate all metabolites of prasugrel that have been identified.
212
F. Asai et al.
Table I. Inhibition of platelet aggregation at each prasugrel dose with 5 or 20 mM ADP as agonist.
% Inhibition of platelet aggregation (mean SE)
Prasugrel dose (mg)
Timepoint
Placebo (n ¼ 4)
2.5 (n ¼ 5)
P-value
10 (n ¼ 5)
P-value
30 (n ¼ 5)
P-value
75 (n ¼ 5)
P-value
5 mM ADP
1h
2h
4h
8h
24 h
48 h
168 h (7 days)
3.8 2.4
28.3 15.4
8.1 5.4
2.2 2.2
14.5 5.5
0.0
2.4 2.4
14.2 5.9
11.5 7.5
5.4 3.8
21.6 9.0
25.0 10.9
N.S.?
N.S.
N.S.
N.S.
N.S.
16.2 8.7
18.0 8.2
18.0 7.6
17.5 7.3
29.0 6.2
N.S.
N.S.
N.S.
N.S.
N.S.
<0.01
<0.05
<0.001
<0.001
<0.001
N.S.
5.3 3.1
N.S.
58.5 11.5
69.4 4.0
71.6 3.8
58.8 2.8
76.0 1.3
61.2 5.0
11.1 5.9
<0.01
<0.05
<0.001
<0.001
<0.001
14.8 6.9
54.7 11.0
69.6 7.5
69.4 6.8
68.2 8.8
72.4 5.3
60.3 7.6
14.5 9.4
20 mM ADP
1h
2h
4h
8h
24 h
48 h
168 h (7 days)
5.9 3.5
6.9 6.9
1.2 1.2
0.0 0.0
6.4 3.9
0.0
1.0 1.0
11.8 5.0
4.0 3.4
2.1 2.1
10.3 5.1
15.4 6.5
N.S.
N.S.
N.S.
N.S.
N.S.
11.3 4.9
17.3 9.8
15.5 7.8
12.2 6.6
15.4 7.3
N.S.
N.S.
N.S.
N.S.
N.S.
43.5 7.8
59.8 9.9
58.5 6.6
54.8 6.9
60.7 5.7
43.9 8.4
13.0 6.2
<0.05
<0.001
<0.001
<0.001
<0.001
43.2 15.7
57.0 7.2
62.3 4.3
51.3 3.9
63.4 4.9
53.4 6.4
6.3 4.1
<0.05
<0.01
<0.001
<0.001
<0.001
??
??
??
12.8 6.6
??
N.S.
10.8 6.5
N.S.
???
N.S.
???
N.S.
???
N.S.
???
N.S.
SE, standard error.
P-values are for prasugrel dose group comparison to placebo using Dunnett test.
?
N.S., no significant difference was observed between prasugrel and placebo with P > 0.05.
??
No sample collection was required at this timepoint.
???
Statistical comparison cannot be performed due to insufficient number of placebo samples at this timepoint.
estimates for the three metabolites using WinNonLin
pharmacokinetic software (version 1.1, Scientific
Consulting Inc., Cary, NC). Summary statistics for
the parameter estimates of AUC(0–24h), the area
under the plasma drug concentration versus time
curve from time 0 to 24 h; Cmax, maximum concentration of metabolite in plasma measured in subject
after dosing; Tmax, the time at which Cmax was
apparent; and t1/2, plasma elimination half-life for
each dose group in the study are presented.
Results
Subjects
Twenty-four healthy male subjects were enrolled in
the study of prasugrel administered as single doses of
2.5, 10, 30, or 75 mg (five subjects at each dose and
one placebo subject per group). The mean age was
30.4 7.4 years, (range 19.0–48.0 years) and the
mean weight was 73.1 9.3 kg (range 59.9–93.2 kg).
Safety
Adverse events. There were 13 postdose adverse
events experienced by seven subjects in this study.
None of these events were considered serious. All of
the adverse events occurring during administration
of prasugrel were considered mild in nature. The
adverse events included gastrointestinal disturbances
(flatulence, nausea, and vomiting), autonomic disturbances (pallor, sweating increased, and vomiting)
and general disorders (rhinitis and superficial cut).
Central and peripheral nervous system disorders
included dizziness and headache. Dizziness was the
most common adverse event (n ¼ 1 at prasugrel
doses of 10, 30, and 75 mg), but occurred at the
same frequency in the subjects receiving placebo
(n ¼ 1). No adverse events were associated with the
2.5 mg dose of prasugrel. Only one event, a mild
headache in a subject in the 10-mg dose group, was
considered possibly related to administration of
study drug. There were no clinically significant
changes noted in clinical laboratory evaluations or
vital signs in any subject. All ECGs, fundoscopic
examinations, and examinations for petechiae were
normal.
Pharmacodynamics
Platelet aggregation. Mean IPA observed in each
dose group using 5 or 20 mM ADP as the agonist is
listed in Table I. Within 1 h of dosing (shortest study
interval) prasugrel, at the two higher doses of 30 and
75 mg, substantial inhibition of platelet aggregation
induced by 20 mM ADP was observed (Figure 2
and Table I). At 1 h, the IPA with prasugrel 30 mg was
43.5 7.8% and with prasugrel 75 mg was
43.2 15.7% compared to IPA with placebo of
5.9 3.5% (P < 0.05 for both doses). The degree of
inhibition observed at 2 h was slightly higher with both
prasugrel 30 and 75 mg (59.8 9.9 and 57.0 7.2%)
and was maintained through the subsequent 22 h.
While the IPA recovered slightly to 43.9 8.4 and
Single oral doses of prasugrel in healthy subjects
213
Maximal platelet aggregation (%)
100
80
60
40
20
0
BL 24 h BL 24 h
75 mg
30 mg
Figure 2. Inhibition of ADP-induced platelet aggregation after
single doses of prasugrel compared to placebo. Mean inhibition of
platelet aggregation (% IPA) at selected timepoints induced by
20 mM ADP is illustrated. Solid circles represent placebo; open
circles, 2.5 mg prasugrel; closed squares, 10 mg prasugrel; open
squares, 30 mg prasugrel; and solid triangles, 75 mg prasugrel.
A 48 h sample was collected only in the prasugrel 30 and 75 mg
groups. Values are mean standard error, n ¼ 4 for placebo group,
n ¼ 5 for all prasugrel dose groups.
53.4 6.4% for prasugrel 30 and 75 mg by 48 h, full
recovery occurred between 48 h and 7 days. At day 7,
platelet aggregation had returned to normal levels in
both the higher dose groups. At 1 h after dosing, the
lower doses of prasugrel, namely 2.5 and 10 mg, had
no measurable effect on platelet aggregation as
indicated by levels of inhibition indistinguishable
from placebo values (P > 0.05 for 2.5 and 10 mg
prasugrel versus placebo). The level of IPA observed
with 5 mM ADP was slightly greater for any given
prasugrel dose (Table I); however, the overall time
course of inhibition and subsequent recovery following cessation of drug were very similar to that found
with 20 mM ADP. The IPA observed with collagen
(2 mg/mL) as the agonist was not as pronounced as
with 20 mM ADP (maximum mean IPA observed with
prasugrel 75 mg was 30.6% with collagen 2 mg/mL at
24 h vs. 63.4% with 20 mM ADP at 24 h), which
suggests that prasugrel or a metabolite is an ADP
receptor antagonist resulting in effective inhibition of
ADP-induced platelet aggregation, but weaker inhibition of collagen-induced aggregation (data not
shown).
Figure 3 illustrates the consistency of the response,
as measured by maximal platelet aggregation,
obtained with prasugrel 30 and 75 mg using either
5 or 20 mM ADP. In all subjects, at 24 h postdose
with prasugrel 30 mg, the MPA was reduced to
39% (IPA 42%). With prasugrel 75 mg, the MPA
was reduced in all subjects to 38% (IPA 50%).
Bleeding time
The mean bleeding times at 4 h postdose of prasugrel
30 and 75 mg increased approximately 3- and 4-fold
5 µM ADP
BL 24 h
30 mg
BL 24 h
75 mg
20 µM ADP
Figure 3. Individual ADP-induced platelet aggregation responses
before and after single doses of prasugrel. Maximum platelet
aggregation (% MPA) at baseline (BL) and 24 h post prasugrel
dose (30 or 75 mg) in each subject. Platelet aggregation was
induced by 5 or 20 mM ADP and the maximum platelet aggregation level achieved during the 4-min observation period is
reported. The horizontal line is the mean MPA for each group.
compared to placebo, from 161 s (placebo) to
444 s (P > 0.05) and 682 s (P < 0.05), in the prasugrel 30 and 75 mg groups, respectively (Table II).
This change was directionally consistent with
the increase in IPA. The mean bleeding times
remained elevated at 24 h postdose for prasugrel
75 mg.
Pharmacokinetics
Pharmacokinetics were studied following single
doses of 2.5, 10, 30, and 75 mg. Plasma concentrations of three metabolites determined after administration of prasugrel in the fasting state at a dose of
75 mg are shown in Figure 4, and the pharmacokinetic parameters are listed in Table III. The
maximum plasma concentration (Cmax) and the
area under the plasma concentration vs. time curve
(AUC(0–24h)) of the metabolites increased proportionally to the dose administered, from 2.5 to 75 mg
(Figure 5A, B). The correlation coefficients
obtained by linear regression analysis for the dose–
AUC(0–24h) relationship for R-95913, R-106583,
and R-100932 were 0.90, 0.89, and 0.83,
respectively. For the dose–Cmax relationship, the
correlation coefficients for R-95913, R-106583, and
R-100932 were 0.57, 0.69, and 0.60, respectively.
The three metabolites appeared in the plasma
soon after administration and reached Cmax in
approximately 1 h, consistent with the appearance
of inhibition of platelet aggregation. The most
abundant metabolite was R-106583, which is an
S-methylated derivative of the active metabolite
(Figure 1).
214
F. Asai et al.
Table II. Bleeding times.
Time after prasugrel administration
4h
Prasugrel dose (mg)
Placebo (n ¼ 4)
2.5 (n ¼ 5)
10 (n ¼ 5)
30 (n ¼ 5)
75 (n ¼ 5)
24 h
Post-study
Mean bleeding
time (sec)
P-value
Mean bleeding
time (sec)
P-value
Mean bleeding
time (sec)
P-value
161 48
165 61
142 17
444 131
682 166
–
N.S.?
N.S.
N.S.
<0.05
120 5
151 17
221 37
272 71
584 203
–
N.S.
N.S.
N.S.
<0.05
172 40
121 8
155 8
168 27
157 8
–
N.S.
N.S.
N.S.
N.S.
Bleeding times are expressed as seconds, mean standard error.
*N.S., no significant difference was observed between prasugrel and placebo with P > 0.05.
Plasma concentration (ng/ml)
500
R-95913
R-106583
R-100932
400
300
200
100
0
0
4
8
12
Time (h)
16
20
24
Figure 4. Plasma concentration profile of metabolites after
administration of 75 mg prasugrel. Concentration of metabolites
over time is displayed. Solid triangles represent R-95913, solid
circles represent R-106532, and open circles represent R-100932.
Values are mean standard error, n ¼ 5 at each timepoint.
Discussion
This was the first clinical study of the novel
thienopyridine
antiplatelet
agent,
prasugrel
(CS-747, LY640315) in healthy volunteers. For the
safety endpoints studied, the results indicated that
prasugrel at the doses and intervals studied appeared
to be safe, well tolerated, and obeyed linear
pharmacokinetics. The pharmacokinetic and pharmacodynamic results of this study indicate rapid
gastrointestinal absorption of prasugrel, which led
to sustained and apparently irreversible inhibition
of ADP-induced platelet aggregation within 1 h of
administration at the doses of 30 and 75 mg of
prasugrel. The antiplatelet effects of prasugrel 2.5
and 10 mg could not be distinguished from placebo.
Increasing levels of IPA were also associated with
a progressive prolongation of the bleeding time.
Rapid onset of platelet inhibition was observed
at the higher doses of prasugrel 30 and 75 mg. At
these higher doses, inhibition of platelet aggregation
occurred within 1 h of dosing and continued through
48 h, supporting the irreversible nature of the antagonism of the P2Y12 receptor. These observations
and conclusions are consistent with ex vivo results in
preclinical animal studies and in vitro human platelet
studies [13]. The rapid onset of platelet inhibition
could be a potential advantage for prasugrel in the
setting of PCI. In addition, there was a marked
consistency of response achieved with prasugrel 30
and 75 mg. Although the sample size in this study
was small, it is noteworthy that at 24 h postdose with
20 mM ADP as agonist, maximal platelet aggregation
achieved with prasugrel 30 mg was reduced to 39%
(IPA 42%) in all subjects. With prasugrel 75 mg at
24 h postdose, maximal platelet aggregation was
reduced in all subjects to 38% (IPA 50%).
Reduced platelet inhibition by prasugrel with
collagen relative to ADP as the agonist is consistent
with the mode of action of prasugrel or its active
metabolite as a purine receptor antagonist that
primarily inhibits ADP-induced platelet aggregation.
The smaller effect on collagen-induced aggregation
reflects the partial role played by the ADP released
following platelet stimulation with collagen.
Three inactive metabolites of prasugrel were measured in this study, one the precursor to the active
metabolite (R-95913) and two downstream metabolites (R-106583 and R100932). The pharmacokinetics of all three metabolites were well described by
an integrated population pharmacokinetic model.
The maximum plasma concentration of the precursor to the active metabolite and the downstream
metabolites appeared approximately 1 h after administration of prasugrel, indicating rapid absorption
of the drug and consistent with the appearance of
inhibition of platelet aggregation. The most abundant metabolite was the S-methylated derivative of
the active metabolite, 106583. Although we did not
measure active metabolite in this study, a proportional relationship of the AUC of R-106583 to that of
the active metabolite has been observed in other
studies (data not shown). The pharmacokinetics of
the metabolites and relationship to platelet inhibition
Single oral doses of prasugrel in healthy subjects
215
Table III. Pharmacokinetic parameters estimated from single ascending dose study.
Prasugrel dose (mg)
2.5 (n ¼ 5)
10 n ¼ 5
30 (n ¼ 5)
75 (n ¼ 5)
R-95913
AUC (0–24 h) (ng h ML1)
Cmax (ng mL1)
Tmax (h)
t1/2 (h)
9.2 2.4
7.4 1.2
0.7 0.1
N.A.
53.2 10.6
30.0 6.9
0.8 0.1
5.6 0.9
157.9 22.5
90.8 12.9
0.6 0.1
6.4 1.3
350.8 36.0
117.0 27.5
1.0 0.2
8.8 1.2
R-106583
AUC (0–24 h)(ng h mL1)
Cmax (ng mL1)
Tmax (h)
t1/2 (h)
58.4 8.7
14.6 1.6
0.8 0.1
8.6.1.4
324.5 25.6
71.5 7.7
1.1 0.1
10.2 0.6
969.0 131.3
189.4 23.5
0.9 0.1
8.9 0.5
2686.1 368.4
391.5 91.6
1.5 0.2
11.0 1.7
R-100932
AUC (0–24 h)(ng h mL1)
Cmax (ng mL1)
Tmax (h)
t1/2 (h)
7.4 1.6
5.2 1.1
1.0 0.2
N.A.
62.4 9.7
28.9 3.9
0.9 0.1
3.5 0.7
204.1 17.7
77.8 7.6
0.7 0.1
5.8 1.0
585.1 94.5
163.0 45.3
1.1 0.2
9.1 1.4
N.A., t1/2 was not calculated due to lack of sufficient data points.
All data are expressed as mean standard error.
AUC(0–24h), the area under the plasma drug concentration vs. time curve from time 0 to 24 h; Cmax, maximum
concentration of drug in plasma measured in subject after dosing; Tmax, the time at which Cmax was apparent; t1/2, plasma
elimination half-life.
Figure 5. Dose response of Cmax and AUC(0–24h). The mean area under the plasma drug concentration versus time curve from time 0 to
24 h (AUC(0–24h), ng h mL) achieved with each dose of prasugrel administered is represented in panel A. Maximum mean concentration
(Cmax, ng mL1) of each metabolite in plasma achieved with each dose of prasugrel administered is represented in panel B. The linear
regression line for the dose–AUC(0–24h) and the dose–Cmax relationship for each metabolite is illustrated. The correlation coefficients
obtained by linear regression analysis for the dose–AUC(0–24h) relationship for R-95913, R-106583, and R-100932 were 0.90, 0.89, and
0.83, respectively. For the dose–Cmax relationship, the correlation coefficients for R-95913, R-106583, and R-100932 were 0.57, 0.69, and
0.60, respectively. Solid triangles represent R-95913, solid circles represent R-106583, and open circles represent R-100932. Values are
mean standard error, n ¼ 5 at each prasugrel dose.
observed in these studies are consistent with previously published preclinical data indicating that
prasugrel is a prodrug that is metabolized to an
active moiety that irreversibly inhibits the platelet
P2Y12 ADP receptor [13].
Although clopidogrel was not included in this
study, previously published studies of clopidogrel
using 5 or 20 mM ADP as the platelet agonist
demonstrated that the onset of IPA requires approximately 2–4 h for clopidogrel at a loading dose of
216
F. Asai et al.
300 mg [20, 21]. In addition, other clinical studies
with clopidogrel 300 mg report a pharmacodynamic
nonresponder rate (i.e. change in maximal percent
aggregation to 20 mM ADP <10%) of 25–30% [9, 11,
12, 22, 23]. Based on comparison to these clopidogrel studies, a higher level of IPA was achieved with
30 mg prasugrel, a dose 10-fold lower than the wellaccepted clopidogrel loading dose (300 mg). In this
study, with prasugrel 30 mg and 20 mM ADP as
agonist, a mean inhibition of aggregation of 60.7% at
24 h postdose was observed compared to a mean
inhibition of 20–40% in published studies for clopidogrel 300 mg loading dose [20, 21, 24] or a widely
variable IPA at 24 h of 30–60% for clopidogrel
600 mg loading dose [20, 24, 25]. The results from
this study are consistent with preclinical animal
studies indicating prasugrel was an irreversible
inhibitor of ADP-induced platelet aggregation with
a fast onset of action and a potency approximately
10–15 times that of clopidogrel [13].
Conclusions
In this single dose study, prasugrel was well tolerated, achieved a consistent high level of platelet
inhibition with a fast onset of action at doses of 30
and 75 mg, and obeyed linear pharmacokinetics at
doses of up to 75 mg. There were no serious adverse
events and no significant bleeding complications.
No abnormal drug effects were observed on safety
evaluations in any of the prasugrel dose groups. This
initial study supported selection of doses of prasugrel
for subsequent multiple dose safety studies of
prasugrel in healthy subjects.
Acknowledgments
The authors would like to acknowledge the assistance provided by Satoshi Fukuda of Sankyo Co.
Ltd., in conducting the statistical analyses and the
writing and administrative assistance of Barbara
Utterback of Eli Lilly and Company in the preparation of this manuscript.
Financial support and potential
Conflict of Interest
The study was supported by Sankyo Co. Ltd.,
Tokyo, Japan. Drs Asai, Naganuma, and Hirota
and Ms Matsushima are employees of Sankyo Co.
Ltd., Tokyo, Japan. Drs Jakubowski, Winters, and
Brandt are employees and stockholders of Eli Lilly
and Company. Sankyo Co. Ltd., and Eli Lilly and
Company are currently co-developing prasugrel for
potential clinical use. Dr Freestone is an employee
of Inveresk Clinical Research Ltd. (now known as
Charles River Laboratories).
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