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Angiomax

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Angiomax

CLINICAL PHARMACOLOGY

Mechanism of Action

Angiomax directly inhibits thrombin by specifically binding both to the catalytic site and to the anion-binding exosite of circulating and clot-bound thrombin. Thrombin is a serine proteinase that plays a central role in the thrombotic process, acting to cleave fibrinogen into fibrin monomers and to activate Factor XIII to Factor XIIIa, allowing fibrin to develop a covalently cross-linked framework which stabilizes the thrombus; thrombin also activates Factors V and VIII, promoting further thrombin generation, and activates platelets, stimulating aggregation and granule release. The binding of Angiomax to thrombin is reversible as thrombin slowly cleaves the Angiomax-Arg 3-Pro 4 bond, resulting in recovery of thrombin active site functions.

In in vitro studies, Angiomax inhibited both soluble (free) and clot-bound thrombin, was not neutralized by products of the platelet release reaction, and prolonged the activated partial thromboplastin time (aPTT), thrombin time (TT), and prothrombin time (PT) of normal human plasma in a concentration-dependent manner. The clinical relevance of these findings is unknown.

Pharmacodynamics

In healthy volunteers and patients (with ≥ 70% vessel occlusion undergoing routine PTCA ), Angiomax exhibited dose-and concentration-dependent anticoagulant activity as evidenced by prolongation of the ACT, aPTT, PT, and TT. Intravenous administration of Angiomax produces an immediate anticoagulant effect. Coagulation times return to baseline approximately 1 hour following cessation of Angiomax administration.

In 291 patients with ≥ 70% vessel occlusion undergoing routine PTCA , a positive correlation was observed between the dose of Angiomax and the proportion of patients achieving ACT values of 300 sec or 350 sec. At an Angiomax dose of 1 mg/kg IV bolus plus 2.5 mg/kg/h IV infusion for 4 hours, followed by 0.2 mg/kg/h, all patients reached maximal ACT values > 300 sec.

Pharmacokinetics

Angiomax exhibits linear pharmacokinetics following IV administration to patients undergoing PTCA. In these patients, a mean steady state Angiomax concentration of 12.3 ± 1.7 mcg/mL is achieved following an IV bolus of 1 mg/kg and a 4-hour 2.5 mg/kg/h IV infusion. Angiomax does not bind to plasma proteins (other than thrombin) or to red blood cells. Angiomax is cleared from plasma by a combination of renal mechanisms and proteolytic cleavage, with a half-life in patients with normal renal function of 25 min.

The disposition of Angiomax was studied in PTCA patients with mild, moderate, and severe renal impairment. Drug elimination was related to glomerular filtration rate (GFR). Total body clearance was similar for patients with normal renal function and with mild renal impairment (60-89 mL/min). Clearance was reduced in patients with moderate and severe renal impairment and in dialysisdependent patients (See Table 6 for pharmacokinetic parameters).

Angiomax is hemodialyzable, with approximately 25% cleared by hemodialysis.

Table 6: PK Parameters in Patients with Renal Impairment*

Renal Function (GFR, mL/min) Clearance (mL/min/kg) Half-life (min)
Normal renal function ( ≥ 90 mL/min) 3.4 25
Mild renal impairment (60-89 mL/min) 3.4 22
Moderate renal impairment (30-59 mL/min) 2.7 34
Severe renal impairment (10-29 mL/min) 2.8 57
Dialysis-dependent patients (off dialysis) 1.0 3.5 hours
* The ACT should be monitored in renally-impaired patients

Clinical Studies

PCI/PTCA

Angiomax has been evaluated in five randomized, controlled interventional cardiology trials reporting 11,422 patients. Stents were deployed in 6062 of the patients in these trials – mainly in trials performed since 1995. Percutaneous transluminal coronary angioplasty, atherectomy or other procedures were performed in the remaining patients.

REPLACE-2 Trial

This was a randomized, double-blind, multicenter study reporting 6002 (intent-to-treat) patients undergoing PCI. Patients were randomized to treatment with Angiomax with the “provisional” use of platelet glycoprotein IIb/IIIa inhibitor (GPI) or heparin plus planned use of GPI. GPIs were added on a “provisional” basis to patients who were randomized to Angiomax in the following circumstances:

  • decreased TIMI flow (0 to 2) or slow reflow;
  • dissection with decreased flow;
  • new or suspected thrombus;
  • persistent residual stenosis;
  • distal embolization;
  • unplanned stent;
  • suboptimal stenting;
  • side branch closure;
  • abrupt closure; clinical instability; and
  • prolonged ischemia.

During the study, one or more of these circumstances occurred in 12.7% of patients in the Angiomax with provisional GPI arm. GPIs were administered to 7.2% of patients in the Angiomax with provisional GPI arm (62.2% of eligible patients).

Patients ranged in age from 25-95 years (median, 63); weight ranged from 35-199 kg (median 85.5); 74.4% were male and 25.6% were female. Indications for PCI included unstable angina (35% of patients), myocardial infarction within 7 days prior to intervention (8% of patients), stable angina (25%) and positive ischemic stress test (24%). Stents were deployed in 85% of patients. Ninety-nine percent of patients received aspirin and 86% received thienopyridines prior to study treatment.

Angiomax was administered as a 0.75 mg/kg bolus followed by a 1.75 mg/kg/h infusion for the duration of the procedure. The activated clotting time (ACT – measured by a Hemochron® device) was measured 5 min after the first bolus of study medication. If the ACT was < 225 seconds, an additional bolus of 0.3 mg/kg was given. At investigator discretion, the infusion could be continued following the procedure for up to 4 hours. The median infusion duration was 44 min. Heparin was administered as a 65 U/kg bolus. The activated clotting time (ACT – measured by a Hemochron® device) was measured 5 min after the first bolus of study medication. If the ACT was < 225 seconds, an additional bolus of 20 units/kg was given. GPIs (either abciximab or eptifibatide) were given according to manufacturers' instructions. Both randomized groups could be given “provisional” treatments during the PCI at investigator discretion, but under double-blind conditions. “Provisional” treatment with GPI was requested in 5.2% of patients randomized to heparin plus GPI (they were given placebo) and 7.2% patients randomized to Angiomax with provisional GPI (they were given abciximab or eptifibatide according to pre-randomization investigator choice and patient stratification).

The percent of patients reaching protocol-specified levels of anticoagulation was greater in the Angiomax with provisional GPI group than in the heparin plus GPI group. For patients randomized to Angiomax with provisional GPI, the median 5 min ACT was 358 sec (interquartile range 320-400 sec) and the ACT was < 225 sec in 3%. For patients randomized to heparin plus GPI, the median 5 min ACT was 317 sec (interquartile range 263-373 sec) and the ACT was < 225 sec in 12%. At the end of the procedure, median ACT values were 334 sec (Angiomax group) and 276 sec (heparin plus GPI group).

For the composite endpoint of death, MI, or urgent revascularization adjudicated under double-blind conditions, the frequency was higher (7.6%)(95% confidence interval 6.7%-8.6%) in the Angiomax with “provisional” GPI arm when compared to the heparin plus GPI arm (7.1%)(95% confidence interval 6.1%-8.0%). However, major hemorrhage was reported significantly less frequently in the Angiomax with provisional GPI arm (2.4%) compared to the heparin plus GPI arm (4.1%). Study outcomes are shown in Table 7

Table 7 : Incidences of Clinical Endpoints at 30 Days for REPLACE-2, a Randomized Double-blind Clinical Trial

Intent-to-treat Population ANGIOMAX with “Provisional” GPI
n=2994
HEPARIN + GPI
n=3008
Death, MI, or urgent revascularization 7.6% 7.1%
Death 0.2% 0.4%
MI 7.00% 6.20%
Urgent revascularization 1.20% 1.40%
Safety Endpoint
Major hemorrhage*† 2.40% 4.10%
*Defined as intracranial bleeding, retroperitoneal bleeding, a transfusion of ≥ 2 units of blood/blood products, a fall in Hgb > 4 g/dL, whether or not bleeding site is identified, spontaneous or non-spontaneous blood loss with a decrease in Hgb > 3 g/dL.
†p-value < 0.001 between groups.

At 12 months' follow-up, mortality was 1.9% among patients randomized to Angiomax with “provisional” GPIs and 2.5% among patients randomized to heparin plus GPI.

Bivalirudin Angioplasty Trial (BAT)

Angiomax was evaluated in patients with unstable angina undergoing PTCA in two randomized, double-blind, multicenter studies with identical protocols. Patients must have had unstable angina defined as: (1) a new onset of severe or accelerated angina or rest pain within the month prior to study entry or (2) angina or ischemic rest pain which developed between four hours and two weeks after an acute myocardial infarction (MI). Overall, 4312 patients with unstable angina, including 741 (17%) patients with post-MI angina, were treated in a 1:1 randomized fashion with Angiomax or heparin. Patients ranged in age from 29-90 (median 63) years, their weight was a median of 80 kg (39-120 kg), 68% were male, and 91% were Caucasian. Twenty-three percent of patients were treated with heparin within one hour prior to randomization. All patients were administered aspirin 300-325 mg prior to PTCA and daily thereafter. Patients randomized to Angiomax were started on an intravenous infusion of Angiomax (2.5 mg/kg/h). Within 5 min after starting the infusion, and prior to PTCA, a 1 mg/kg loading dose was administered as an intravenous bolus. The infusion was continued for 4 hours, then the infusion was changed under double-blinded conditions to Angiomax (0.2 mg/kg/h) for up to an additional 20 hours (patients received this infusion for an average of 14 hours). The ACT was checked at 5 min and at 45 min following commencement. If on either occasion the ACT was < 350 sec, an additional double-blinded bolus of placebo was administered. The Angiomax dose was not titrated to ACT. Median ACT values were: ACT in sec (5th percentile-95th percentile): 345 sec (240-595 sec) at 5 min and 346 sec (range 269-583 sec) at 45 min after initiation of dosing. Patients randomized to heparin were given a loading dose (175 IU/kg) as an intravenous bolus 5 min before the planned procedure, with immediate commencement of an infusion of heparin (15 IU/kg/h). The infusion was continued for 4 hours. After 4 hours of infusion, the heparin infusion was changed under double-blinded conditions to heparin (15 IU/kg/h) for up to 20 additional hours. The ACT was checked at 5 min and at 45 min following commencement. If on either occasion the ACT was < 350 sec, an additional double-blind bolus of heparin (60 IU/kg) was administered. Once the target ACT was achieved for heparin patients, no further ACT measurements were performed. All ACTs were determined with the Hemochron® device. The protocol allowed use of open-label heparin at the discretion of the investigator after discontinuation of blinded study medication, whether or not an endpoint event (procedural failure) had occurred. The use of open-label heparin was similar between Angiomax and heparin treatment groups (about 20% in both groups).

The studies were designed to demonstrate the safety and efficacy of Angiomax in patients undergoing PTCA as a treatment for unstable angina as compared with a control group of similar patients receiving heparin during and up to 24 hours after initiation of PTCA. The primary protocol endpoint was a composite endpoint called procedural failure, which included both clinical and angiographic elements measured during hospitalization. The clinical elements were: the occurrence of death, MI, or urgent revascularization, adjudicated under double-blind conditions. The angiographic elements were: impending or abrupt vessel closure. The protocol-specified safety endpoint was major hemorrhage.

The median duration of hospitalization was 4 days for both the Angiomax and the heparin treatment groups. The rates of procedural failure were similar in the Angiomax and heparin treatment groups. Study outcomes are shown in Table 8

Table 8 : Incidences of In-hospital Clinical Endpoints in BAT Trial Occurring within 7 DaysAll Patients

  ANGIOMAX
n=2161
HEPARIN
n=2151
Efficacy Endpoints
Procedural failure * 7.90% 9.30%
Death, MI, revascularization 6.20% 7.90%
  Death 0.20% 0.20%
  MI† 3.30% 4.20%
  Revascularization‡ 4.20% 5.60%
Safety Endpoint
Major hemorrhage§ 3.50% 9.30%

* The protocol-specified primary endpoint (a composite of death or MI or clinical deterioration of cardiac origin requiring revascularization or placement of an aortic balloon pump or angiographic evidence of abrupt vessel closure).
† Defined as: Q-wave MI; CK-MB elevation ≥ 2 x ULN, new ST-or T-wave abnormality, and chest pain ≥ 30 min; OR new LBBB with chest pain ≥ 30 min and/or elevated CK-MB enzymes; OR elevated CK-MB and new ST-or T-wave abnormality without chest pain; OR elevated CK-MB.
‡ Defined as: any revascularization procedure, including angioplasty, CABG, stenting, or placement of an intra-aortic balloon pump. § Defined as the occurrence of any of the following: intracranial bleeding, retroperitoneal bleeding, clinically overt bleeding with a decrease in Hgb ≥ 3 g/dL or leading to a transfusion of ≥ 2 units of blood.

AT-BAT Trial

This was a single-group open-label study which enrolled 51 patients with heparin-induced thrombocytopenia (HIT) or heparin induced thrombocytopenia and thrombosis syndrome (HITTS) undergoing PCI. Evidence for the diagnosis of HIT/HITTS was based on a clinical history of a decrease of platelets in patients after heparin administration [new diagnosis or history of clinically suspected or objectively documented HIT/HITTS defined as either: 1) HIT: positive heparin-induced platelet aggregation (HIPA) or other functional assay where the platelet count has decreased to < 100,000/mL (minimum 30% from prior to heparin), or has decreased to < 150,000/mL (minimum 40% from prior to heparin), or has decreased as above within hours of receiving heparin in a patient with a recent, previous exposure to heparin; 2) HITTS: thrombocytopenia as above plus arterial or venous thrombosis diagnosed by physician examination/laboratory and/or appropriate imaging studies]. Patients ranged in age from 48-89 years (median 70); weight ranged from 42-123 kg (median 76); 50% were male and 50% were female. Angiomax was administered as either 1 mg/kg bolus followed by 2.5 mg/kg/h (high dose in 28 patients) or 0.75 mg/kg bolus followed by a 1.75 mg/kg/h infusion (lower dose in 25 patients) for up to 4 hours. Ninety-eight percent of patients received aspirin, 86% received clopidogrel and 19% received GPIs.

The median ACT values at the time of device activation were 379 sec (high dose) and 317 sec (lower dose). Following the procedure, 48 of the 51 patients (94%) had TIMI grade 3 flow and stenosis < 50%. One patient died during a bradycardic episode 46 hours after successful PCI, another patient required surgical revascularization, and one patient experienced no flow requiring a temporary intraaortic balloon.

Two of the fifty-one patients with the diagnosis of HIT/HITTS developed thrombocytopenia after receiving Angiomax and GPIs.

Last reviewed on RxList: 6/3/2013
This monograph has been modified to include the generic and brand name in many instances.

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