CLINICAL PHARMACOLOGY
Mechanism of Action
Eptifibatide reversibly
inhibits platelet aggregation by preventing the binding of fibrinogen, von
Willebrand factor, and other adhesive ligands to GP IIb/IIIa. When administered
intravenously, eptifibatide inhibits ex vivo platelet aggregation in a dose-
and concentration-dependent manner. Platelet aggregation inhibition is
reversible following cessation of the eptifibatide infusion; this is thought to
result from dissociation of eptifibatide from the platelet.
Pharmacodynamics
Infusion of eptifibatide into
baboons caused a dose-dependent inhibition of ex vivo platelet aggregation,
with complete inhibition of aggregation achieved at infusion rates greater than
5 mcg/kg/min. In a baboon model that is refractory to aspirin and heparin,
doses of eptifibatide that inhibit aggregation prevented acute thrombosis with
only a modest prolongation (2- to 3-fold) of the bleeding time. Platelet
aggregation in dogs was also inhibited by infusions of eptifibatide, with
complete inhibition at 2 mcg/kg/min. This infusion dose completely inhibited
canine coronary thrombosis induced by coronary artery injury (Folts model).
Human pharmacodynamic data were
obtained in healthy subjects and in patients presenting with UA or NSTEMI
and/or undergoing percutaneous coronary intervention. Studies in healthy
subjects enrolled only males; patient studies enrolled approximately one-third
women. In these studies, INTEGRILIN inhibited ex vivo platelet aggregation
induced by adenosine diphosphate (ADP) and other agonists in a dose- and
concentration-dependent manner. The effect of INTEGRILIN was observed
immediately after administration of a 180-mcg/kg intravenous bolus. Table 4
shows the effects of dosing regimens of INTEGRILIN used in the IMPACT II and
PURSUIT studies on ex vivo platelet aggregation induced by 20 μM ADP in PPACK-anticoagulated
platelet-rich plasma and on bleeding time. The effects of the dosing regimen
used in ESPRIT on platelet aggregation have not been studied.
Table 4: Platelet Inhibition
and Bleeding Time
|
PURSUIT 180/2* |
Inhibition of platelet aggregation 15 min after bolus |
84% |
Inhibition of platelet aggregation at steady state |
> 90% |
Bleeding-time prolongation at steady state |
< 5x |
Inhibition of platelet aggregation 4h after infusion discontinuation |
< 50% |
Bleeding-time prolongation 6h after infusion discontinuation |
1.4x |
* 180-mcg/kg bolus followed by
a continuous infusion of 2 mcg/kg/min. |
The INTEGRILIN dosing regimen
used in the ESPRIT study included two 180-mcg/kg bolus doses given 10 minutes
apart combined with a continuous 2-mcg/kg/min infusion.
When administered alone,
INTEGRILIN has no measurable effect on PT or aPTT.
There were no important
differences between men and women or between age groups in the pharmacodynamic
properties of eptifibatide. Differences among ethnic groups have not been
assessed.
Pharmacokinetics
The pharmacokinetics of
eptifibatide are linear and dose-proportional for bolus doses ranging from 90
to 250 mcg/kg and infusion rates from 0.5 to 3 mcg/kg/min. Plasma elimination
half-life is approximately 2.5 hours. Administration of a single 180-mcg/kg
bolus combined with an infusion produces an early peak level, followed by a
small decline prior to attaining steady state (within 4-6 hours). This decline
can be prevented by administering a second 180-mcg/kg bolus 10 minutes after
the first. The extent of eptifibatide binding to human plasma protein is about
25%. Clearance in patients with coronary artery disease is about 55 mL/kg/h. In
healthy subjects, renal clearance accounts for approximately 50% of total body
clearance, with the majority of the drug excreted in the urine as eptifibatide,
deaminated eptifibatide, and other, more polar metabolites. No major
metabolites have been detected in human plasma.
Special Populations
Geriatric
Patients in clinical studies
were older (range: 20-94 years) than those in the clinical pharmacology
studies. Elderly patients with coronary artery disease demonstrated higher
plasma levels and lower total body clearance of eptifibatide when given the
same dose as younger patients. Limited data are available on lighter weight
( < 50 kg) patients over 75 years of age.
Renal Impairment
In patients with moderate to
severe renal insufficiency (CrCl < 50 mL/min using the Cockcroft-Gault
equation), the clearance of eptifibatide is reduced by approximately 50% and
steady-state plasma levels approximately doubled [see Use in Specific
Populations and DOSAGE AND ADMINISTRATION].
Hepatic Impairment
No studies have been conducted
in patients with hepatic impairment.
Gender
Males and females have not demonstrated
any clinically significant differences in the pharmacokinetics of eptifibatide.
Clinical Studies
INTEGRILIN was studied in 3 placebo-controlled,
randomized studies. PURSUIT evaluated patients with acute coronary syndromes:
UA or NSTEMI. Two other studies, ESPRIT and IMPACT II, evaluated patients about
to undergo a PCI. Patients underwent primarily balloon angioplasty in IMPACT II
and intracoronary stent placement, with or without angioplasty, in ESPRIT.
Non-ST-Segment Elevation Acute Coronary Syndrome
Non-ST-segment elevation acute coronary syndrome is
defined as prolonged ( ≥ 10 minutes) symptoms of cardiac ischemia within
the previous 24 hours associated with either ST-segment changes (elevations
between 0.6 mm and 1 mm or depression > 0.5 mm), T-wave inversion ( > 1 mm),
or positive CK-MB. This definition includes “unstable angina” and
“NSTEMI” but excludes MI that is associated with Q waves or greater
degrees of ST-segment elevation.
PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable
Angina: Receptor Suppression Using INTEGRILIN Therapy)
PURSUIT was a 726-center, 27-country, double-blind,
randomized, placebo-controlled study in 10,948 patients presenting with UA or
NSTEMI. Patients could be enrolled only if they had experienced cardiac
ischemia at rest ( ≥ 10 minutes) within the previous 24 hours and had
either ST-segment changes (elevations between 0.6 mm and 1 mm or depression
> 0.5 mm), T-wave inversion ( > 1 mm), or increased CK-MB. Important
exclusion criteria included a history of bleeding diathesis, evidence of
abnormal bleeding within the previous 30 days, uncontrolled hypertension, major
surgery within the previous 6 weeks, stroke within the previous 30 days, any
history of hemorrhagic stroke, serum creatinine > 2 mg/dL, dependency on
renal dialysis, or platelet count < 100,000/mm³.
Patients were randomized to placebo, to INTEGRILIN
180-mcg/kg bolus followed by a 2-mcg/kg/min infusion (180/2), or to INTEGRILIN
180-mcg/kg bolus followed by a 1.3-mcg/kg/min infusion (180/1.3). The infusion
was continued for 72 hours, until hospital discharge, or until the time of
CABG, whichever occurred first, except that if PCI was performed, the
INTEGRILIN infusion was continued for 24 hours after the procedure, allowing
for a duration of infusion up to 96 hours.
The lower-infusion-rate arm was stopped after the first
interim analysis when the 2 active-treatment arms appeared to have the same
incidence of bleeding.
Patient age ranged from 20 to 94 (mean 63) years, and 65%
were male. The patients were 89% Caucasian, 6% Hispanic, and 5% Black,
recruited in the United States and Canada (40%), Western Europe (39%), Eastern
Europe (16%), and Latin America (5%).
This was a “real world” study; each patient was
managed according to the usual standards of the investigational site;
frequencies of angiography, PCI, and CABG therefore differed widely from site
to site and from country to country. Of the patients in PURSUIT, 13% were
managed with PCI during drug infusion, of whom 50% received intracoronary
stents; 87% were managed medically (without PCI during drug infusion).
The majority of patients received aspirin (75-325 mg once
daily). Heparin was administered intravenously or subcutaneously, at the
physician's discretion, most commonly as an intravenous bolus of 5000 units
followed by a continuous infusion of 1000 units/h. For patients weighing less
than 70 kg, the recommended heparin bolus dose was 60 units/kg followed by a
continuous infusion of 12 units/kg/h. A target aPTT of 50 to 70 seconds was
recommended. A total of 1250 patients underwent PCI within 72 hours after
randomization, in which case they received intravenous heparin to maintain an
ACT of 300 to 350 seconds.
The primary endpoint of the study was the occurrence of
death from any cause or new MI (evaluated by a blinded Clinical Endpoints
Committee) within 30 days of randomization.
Compared to placebo, INTEGRILIN administered as a
180-mcg/kg bolus followed by a 2mcg/kg/min infusion significantly (p=0.042)
reduced the incidence of endpoint events (see Table 6). The reduction in the
incidence of endpoint events in patients receiving INTEGRILIN was evident early
during treatment, and this reduction was maintained through at least 30 days
(see Figure 1). Table 5 also shows the incidence of the components of the
primary endpoint, death (whether or not preceded by an MI) and new MI in
surviving patients at 30 days.
Table 5: Clinical Events in the PURSUIT Study
Death or MI |
Placebo
(n=4739)
n (%) |
INTEGRILIN (180 mcg/kg bolus then 2 mcg/kg/min infusion)
(n=4722)
n (%) |
p-value |
3 days |
359 (7.6%) |
279 (5.9%) |
0.001 |
7 days |
552 (11.6%) |
477 (10.1%) |
0.016 |
30 days |
|
|
|
Death or MI (primary endpoint) |
745 (15.7%) |
672 (14.2%) |
0.042 |
Death |
177 (3.7%) |
165 (3.5%) |
|
Nonfatal MI |
568 (12%) |
507 (10.7%) |
|
Figure 1: Kaplan-Meier Plot
of Time to Death or Myocardial Infarction Within 30 Days of Randomization in
the PURSUIT Study
Treatment with INTEGRILIN prior
to determination of patient management strategy reduced clinical events
regardless of whether patients ultimately underwent diagnostic catheterization,
revascularization (i.e., PCI or CABG surgery) or continued to receive medical
management alone. Table 6 shows the incidence of death or MI within 72 hours.
Table 6: Clinical Events
(Death or MI) in the PURSUIT Study Within 72 Hours of Randomization
|
Placebo |
INTEGRILIN (180 mcg/kg bolus then 2 mcg/kg/min infusion) |
Overall patient population |
n=4739 |
n=4722 |
- At 72 hours |
7.6% |
5.9% |
Patients undergoing early PCI |
n=631 |
n=619 |
- Pre-procedure (nonfatal MI only) |
5.5% |
1.8% |
- At 72 hours |
14.4% |
9% |
Patients not undergoing early PCI |
n=4108 |
n=4103 |
- At 72 hours |
6.5% |
5.4% |
All of the effect of INTEGRILIN
was established within 72 hours (during the period of drug infusion),
regardless of management strategy. Moreover, for patients undergoing early PCI,
a reduction in events was evident prior to the procedure.
An analysis of the results by
sex suggests that women who would not routinely be expected to undergo PCI
receive less benefit from INTEGRILIN (95% confidence limits for relative risk
of 0.94 - 1.28) than do men (0.72 - 0.9). This difference may be a true
treatment difference, the effect of other differences in these subgroups, or a
statistical anomaly. No differential outcomes were seen between male and female
patients undergoing PCI (see results for ESPRIT).
Follow-up data were available
through 165 days for 10,611 patients enrolled in the PURSUIT trial (96.9% of
the initial enrollment). This follow-up included 4566 patients who received
INTEGRILIN at the 180/2 dose. As reported by the investigators, the occurrence
of death from any cause or new MI for patients followed for at least 165 days
was reduced from 13.6% with placebo to 12.1% with INTEGRILIN 180/2.
Percutaneous Coronary
Intervention (PCI)
IMPACT II (INTEGRILIN to
Minimize Platelet Aggregation and Prevent Coronary Thrombosis II)
IMPACT II was a multicenter,
double-blind, randomized, placebo-controlled study conducted in the United
States in 4010 patients undergoing PCI. Major exclusion criteria included a
history of bleeding diathesis, major surgery within 6 weeks of treatment,
gastrointestinal bleeding within 30 days, any stroke or structural CNS
abnormality, uncontrolled hypertension, PT > 1.2 times control, hematocrit
< 30%, platelet count < 100,000/mm³, and pregnancy.
Patient age ranged from 24 to
89 (mean 60) years, and 75% were male. The patients were 92% Caucasian, 5%
Black, and 3% Hispanic. Forty-one percent of the patients underwent PCI for
ongoing ACS. Patients were randomly assigned to 1 of 3 treatment regimens, each
incorporating a bolus dose initiated immediately prior to PCI followed by a
continuous infusion lasting 20 to 24 hours:
135-mcg/kg bolus followed by a
continuous infusion of 0.5 mcg/kg/min of INTEGRILIN (135/0.5);
135-mcg/kg bolus followed by a
continuous infusion of 0.75 mcg/kg/min of INTEGRILIN (135/0.75); or
a matching placebo bolus
followed by a matching placebo continuous infusion.
Each patient received aspirin
and an intravenous heparin bolus of 100 units/kg, with additional bolus
infusions of up to 2000 additional units of heparin every 15 minutes to
maintain an ACT of 300 to 350 seconds.
The primary endpoint was the
composite of death, MI, or urgent revascularization, analyzed at 30 days after
randomization in all patients who received at least 1 dose of study drug.
As shown in Table 7, each
INTEGRILIN regimen reduced the rate of death, MI, or urgent intervention,
although at 30 days, this finding was statistically significant only in the
lower-dose INTEGRILIN group. As in the PURSUIT study, the effects of INTEGRILIN
were seen early and persisted throughout the 30-day period.
Table 7: Clinical Events in
the IMPACT II Study
|
Placebo n (%) |
INTEGRILIN (135 mcg/kg bolus then 0.5 mcg/kg/min infusion) n (%) |
INTEGRILIN (135 mcg/kg bolus then 0.75 mcg/kg/min infusion) n (%) |
Patients |
1285 |
1 300 |
1286 |
Abrupt Closure |
65 (5.1 %) |
36 (2.8%) |
43 (3.3%) |
p-value versus placebo |
|
0.003 |
0.03 |
Death, MI, or Urgent Intervention |
24 hours |
123 (9.6%) |
86 (6.6%) |
89 (6.9%) |
p-value versus placebo |
|
0.006 |
0.014 |
48 hours |
131 (10.2%) |
99 (7.6%) |
102 (7.9%) |
p-value versus placebo |
|
0.021 |
0.045 |
30 days (primary endpoint) |
149 (11.6%) |
118 (9.1%) |
128 (10%) |
p-value versus placebo |
|
0.035 |
0.179 |
Death or MI |
30 days |
110 (8.6%) |
89 (6.8%) |
95 (7.4%) |
p-value versus placebo |
|
0.102 |
0.272 |
6 months |
151 (11.9%)* |
136 (10.6%)* |
130 (10.3%)* |
p-value versus placebo |
|
0.297 |
0.182 |
* Kaplan-Meier estimate of
event rate. |
ESPRIT (Enhanced Suppression of
the Platelet IIb/IIIa Receptor with INTEGRILIN Therapy)
The ESPRIT study was a
multicenter, double-blind, randomized, placebo-controlled study conducted in
the United States and Canada that enrolled 2064 patients undergoing elective or
urgent PCI with intended intracoronary stent placement. Exclusion criteria
included MI within the previous 24 hours, ongoing chest pain, administration of
any oral antiplatelet or oral anticoagulant other than aspirin within 30 days
of PCI (although loading doses of thienopyridine on the day of PCI were
encouraged), planned PCI of a saphenous vein graft or subsequent “staged” PCI,
prior stent placement in the target lesion, PCI within the previous 90 days, a
history of bleeding diathesis, major surgery within 6 weeks of treatment,
gastrointestinal bleeding within 30 days, any stroke or structural CNS
abnormality, uncontrolled hypertension, PT > 1.2 times control, hematocrit
< 30%, platelet count < 100,000/mm³, and pregnancy.
Patient age ranged from 24 to
93 (mean 62) years, and 73% of patients were male. The study enrolled 90%
Caucasian, 5% African American, 2% Hispanic, and 1% Asian patients. Patients
received a wide variety of stents. Patients were randomized either to placebo
or INTEGRILIN administered as an intravenous bolus of 180 mcg/kg followed
immediately by a continuous infusion of 2 mcg/kg/min, and a second bolus of 180
mcg/kg administered 10 minutes later (180/2/180). INTEGRILIN infusion was
continued for 18 to 24 hours after PCI or until hospital discharge, whichever
came first. Each patient received at least 1 dose of aspirin (162-325 mg) and
60 units/kg of heparin as a bolus (not to exceed 6000 units) if not already
receiving a heparin infusion. Additional boluses of heparin (10-40 units/kg)
could be administered in order to reach a target ACT between 200 and 300
seconds.
The primary endpoint of the
ESPRIT study was the composite of death, MI, urgent target vessel
revascularization (UTVR), and “bailout” to open-label INTEGRILIN due to a
thrombotic complication of PCI (TBO) (e.g., visible thrombus, “no reflow,” or
abrupt closure) at 48 hours. MI, UTVR, and TBO were evaluated by a blinded
Clinical Events Committee.
As shown in Table 8, the
incidence of the primary endpoint and selected secondary endpoints was
significantly reduced in patients who received INTEGRILIN. A treatment benefit
in patients who received INTEGRILIN was seen by 48 hours and at the end of the
30-day observation period.
Table 8: Clinical Events in
the ESPRIT Study
|
Placebo
(n=1024) |
INTEGRILIN*
(n=1040) |
Relative Risk (95% CI) |
p-value |
Death, MI, UTVR, or Thrombotic “Bailout” |
48 hours (primary endpoint) |
108 (10.5%) |
69 (6.6%) |
0.629 (0.471, 0.84) |
0.0015 |
30 days |
120 (11.7%) |
78 (7.5%) |
0.64 (0.488, 0.84) |
0.0011 |
Death, MI, or UTVR |
48 hours |
95 (9.3%) |
62 (6%) |
0.643 (0.472, 0.875) |
0.0045 |
30 days (key secondary endpoint) |
107 (10.4%) |
71 (6.8%) |
0.653 (0.49, 0.871) |
0.0034 |
Death or MI |
48 hours |
94 (9.2%) |
57 (5.5%) |
0.597 (0.435, 0.82) |
0.0013 |
30 days |
104 (10.2%) |
66 (6.3%) |
0.625 (0.465, 0.84) |
0.0016 |
*INTEGRILIN was administered as 180 mcg/kg boluses at times 0 and 10
minutes and an infusion at 2 mcg/kg/min. |
The need for thrombotic
“bailout” was significantly reduced with INTEGRILIN at 48 hours (2.1% for
placebo, 1% for INTEGRILIN; p=0.029). Consistent with previous studies of GP
IIb/IIIa inhibitors, most of the benefit achieved acutely with INTEGRILIN was
in the reduction of MI. INTEGRILIN reduced the occurrence of MI at 48 hours
from 9% for placebo to 5.4% (p=0.0015) and maintained that effect with
significance at 30 days.
There was no treatment
difference with respect to sex in ESPRIT. INTEGRILIN reduced the incidence of
the primary endpoint in both men (95% confidence limits for relative risk:
0.54, 1.07) and women (0.24, 0.72) at 48 hours.
Follow-up (12-month) mortality
data were available for 2024 patients (1017 on INTEGRILIN) enrolled in the
ESPRIT trial (98.1% of the initial enrollment). Twelve-month clinical event
data were available for 1964 patients (988 on INTEGRILIN), representing 95.2%
of the initial enrollment. As shown in Table 9, the treatment effect of INTEGRILIN
seen at 48 hours and 30 days appeared preserved at 6 months and 1 year. Most of
the benefit was in reduction of MI.
Table 9: Clinical Events at
6 Months and 1 Year in the ESPRIT Study
|
Placebo
(n=1024) |
INTEGRILIN
(n=1040) |
Hazard Ratio (95% CI) |
Death, MI, or Target Vessel Revascularization |
6 months |
187 (18.5%) |
146 (14.3%) |
0.744 (0.599, 0.924) |
1 year |
222 (22.1%) |
178 (17.5%) |
0.762 (0.626, 0.929) |
Death, MI |
6 months |
117 (11.5%) |
77 (7.4%) |
0.631 (0.473, 0.841) |
1 year |
126 (12.4%) |
83 (8%) |
0.63 (0.478, 0.832) |
Percentages are Kaplan-Meier
event rates.