July 28, 2016
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Activase

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Activase

CLINICAL PHARMACOLOGY

Mechanism Of Action

Alteplase is a serine protease responsible for fibrin-enhanced conversion of plasminogen to plasmin. It produces limited conversion of plasminogen in the absence of fibrin.

When introduced into the systemic circulation at pharmacologic concentration, alteplase binds tofibrin in a thrombus and converts the entrapped plasminogen to plasmin. This initiates local fibrinolysis with limited systemic proteolysis.

Pharmacodynamics

Following administration of 100 mg Activase, there is a decrease (16%-36%) in circulating fibrinogen. In a controlled trial, 8 of 73 patients (11%) receiving Activase (1.25 mg/kg body weight over 3 hours) experienced a decrease in fibrinogen to below 100 mg/dL.

Pharmacokinetics

Alteplase in acute myocardial infarction (AMI) patients is rapidly cleared from the plasma with an initial half-life of less than 5 minutes. There is no difference in the dominant initial plasma half-life between the 3-hour and accelerated regimens for AMI. The plasma clearance of alteplase is 380-570 mL/min, primarily mediated by the liver. The initial volume of distribution approximates plasma volume.

Clinical Studies

Acute Ischemic Stroke (AIS)

Two placebo-controlled, double-blind trials (Studies 1 and 2) were conducted in patients with AIS. Both studies enrolled patients with measurable neurological deficit who could complete screening and begin study treatment within 3 hours from symptom onset. A cranial computerized tomography (CT) scan was performed prior to treatment to rule out the presence of intracranial hemorrhage. Blood pressure was actively controlled (185/110 mm Hg or lower) for 24 hours.

Patients were randomized (1:1) to receive either 0.9 mg/kg Activase (maximum of 90 mg) or placebo. Activase was administered as a 10% initial IV bolus over 1 minute followed by continuous IV infusion of the remainder over 60 minutes. Study treatment was initiated prior to the availability of coagulation study results in patients without recent use of oral anticoagulants and/or heparin and was discontinued if the pretreatment prothrombin time (PT) was greater than 15 seconds or the activated partial thromboplastin time (aPTT) was elevated. Patients with prior aspirin use were included. Administration of anticoagulants and antiplatelet agents was prohibited for the first 24 hours following symptom onset.

Study 1 (n=291) evaluated neurological improvement at 24 hours after stroke onset. The primary endpoint, the proportion of patients with a 4 point or greater improvement in the National Institutes of Health Stroke Scale (NIHSS) score or complete recovery (NIHSS score of 0), was not significantly different between treatment groups. A prespecified secondary analysis suggested improved 3-month outcome associated with Activase treatment using the following stroke assessment scales: Barthel Index, Modified Rankin Scale, Glasgow Outcome Scale, and the NIHSS.

Study 2 (n=333) assessed clinical outcome at 3 months. A favorable outcome was defined as minimal or no disability using four stroke assessment scales: Barthel Index (score of 95 or greater), Modified Rankin Scale (score of 1 or less), Glasgow Outcome Scale (score of 1), and NIHSS (score of 1 or less). The results comparing Activase- and placebo-treated patients for the four outcome scales together (Generalized Estimating Equations) and individually are presented in Table 7. In this study, depending upon the scale, the favorable outcome of minimal or no disability occurred in at least 11 per 100 more patients treated with Activase than those receiving placebo. Study results demonstrated consistent functional and neurological improvement within all four stroke scales as indicated by median scores. These results were consistent with the 3-month outcome treatment effects observed in Study 1.

Table 7: Study 2 Three-Month Efficacy Outcomes

Analysis Frequency of Favorable Outcomea
Placebo
(n=165)
Activase
(n=168)
Absolute Difference (95% CI) Odds Ratiob (95% Cl) p-Valuec
Generalized Estimating Equations (Multivariate) - - - 1.71
(1.15, 2.56)
0.02
Barthel Index 37.6% 50.0% 12.4%
(3.0, 21.9)
1.66
(1.07, 2.57)
0.02
Modified Rankin Scale 26.1% 38.7% 12.6%
(3.7, 21.6)
1.79
(1.12, 2.85)
0.02
Glasgow Outcome Scale 31.5% 44.0% 12.5%
(3.3, 21.8)
1.71
(1.09, 2.68)
0.02
NIHSS 20.0% 31.0% 11.0%
(2.6, 19.3)
1.79
(1.06, 2.96)
0.02
a Favorable Outcome is defined as recovery with minimal or no disability.
b Value greater than 1 indicates odds of recovery in favor of Activase treatment.
c p-Value for Odds Ratio is from Generalized Estimating Equations with logit link.

In a prespecified subgroup analysis of patients receiving aspirin prior to onset of stroke symptoms, the favorable outcome for Activase-treated patients was preserved.

Acute Myocardial Infarction (AMI)

Two Activase dose regimens have been studied in patients experiencing acute myocardial infarction [see DOSAGE AND ADMINISTRATION]. The comparative efficacy of these two regimens has not been evaluated.

Accelerated Infusion In AMI Patients

Accelerated infusion of Activase was studied in an international, multi-center trial that randomized 41,021 patients with AMI to four thrombolytic regimens (Study 3). Entry criteria included onset of chest pain within 6 hours of treatment and ST-segment elevation of ECG. The four treatment regimens included accelerated infusion of Activase (≤100 mg over 90 minutes) plus intravenous (IV) heparin (n = 10,396); Streptokinase (1.5 million units over 60 minutes) plus IV heparin (SK [IV], n =10,410); Streptokinase plus subcutaneous (SQ) heparin (SK [SQ] n= 9841). A fourth regimen combined Activase and Streptokinase (n =10,374). All patients received 160 mg chewable aspirin administered as soon as possible, followed by 160-325 mg daily. Bolus IV heparin 5000 U was initiated as soon as possible, followed by a 1000 U/hour continuous IV infusion for at least 48 hours; subsequent heparin therapy was at the physician's discretion. Heparin SQ 12,500 U was administered 4 hours after initiation of SK therapy, followed by 12,500 U twice daily for 7 days or until discharge, whichever came first. Many of the patients randomized to receive SQ heparin received some IV heparin, usually in response to recurrent chest pain and/or the need for a medical procedure. Some received IV heparin on arrival to the emergency room prior to enrollment and randomization.

Key results from Study 3 are shown in Table 8. The incidence of 30-day mortality for Activase accelerated infusion was 1.0% lower than for either Streptokinase plus heparin regimen. The incidence of combined 30-day mortality or nonfatal stroke for the Activase accelerated infusion was 1.0% lower than for SK (IV) and 0.8% lower than for SK (SQ).

Table 8: Efficacy and Safety Results for Study 3

Event Accelerated Activase SK (IV) p-Valuea SK (SQ) p-Valuea
30-Day Mortality 6.3% 7.3% 0.003 7.3% 0.007
30-Day Mortality or Nonfatal Stroke 7.2% 8.2% 0.006 8.0% 0.036
24-Hour Mortality 2.4% 2.9% 0.009 2.8% 0.029
Any Stroke 1.6% 1.4% 0.32 1.2% 0.03
Intracerebral Hemorrhage 0.7% 0.6% 0.22 0.5% 0.02
a Two-tailed p-value is for comparison of Accelerated Activase to the respective SK control arm.

Subgroup analysis of patients by age, infarct location, time from symptom onset to thrombolytic treatment, and treatment in the U.S. or elsewhere showed consistently lower 30-day mortality on Activase.

For patients who were over 75 years of age, a predefined subgroup consisting of 12% of patients enrolled, the incidence of stroke was 4.0% for the Activase accelerated infusion group, 2.8% for SK (IV), and 3.2% for SK (SQ); the incidence of combined 30-day mortality or nonfatal stroke was 20.6% for accelerated infusion of Activase, 21.5% for SK (IV), and 22.0% for SK (SQ).

3-Hour Infusion In AMI Patients

In a double-blind, randomized trial (n = 138) comparing 3-hour infusion of Activase to placebo (Study 4), patients infused with Activase within 4 hours of onset of symptoms experienced improved left ventricular function at Day 10 compared to the placebo group, when ejection fraction was measured by gated blood pool scan (53.2% vs. 46.4%, p =0.018). Relative to baseline (Day 1) values, the net changes in ejection fraction were + 3.6% and -4.7% for the treated and placebo groups, respectively (p=0.0001). The treated group had a reduced incidence of clinical heart failure (14%) compared to the placebo group (33%) (p = 0.009).

In a double-blind, randomized trial (n =5013) comparing 3-hour infusion of Activase to placebo (Study 5), patients infused with Activase within 5 hours of AMI symptom onset experienced improved 30-day survival compared to the placebo arm. At 1 month, the overall mortality rates were 7.2% for the Activase group and 9.8% for the placebo group (p = 0.001). At 6 months, the overall mortality rate for Activase-treated patients was 10.4% compared to the placebo arm (13.1%, p= 0.008).

Acute Massive Pulmonary Embolism (PE)

Study 6 was a comparative randomized trial (n =45) in which 59% of patients (n =22) treated with Activase (100 mg over 2 hours) experienced moderate or marked lysis of pulmonary emboli when assessed by pulmonary angiography 2 hours after treatment initiation. Activase-treated patients also experienced a significant reduction in pulmonary embolism-induced pulmonary hypertension within 2 hours of treatment (p=0.003). Pulmonary perfusion at 24 hours, as assessed by radionuclide scan, was significantly improved (p= 0.002).

Last reviewed on RxList: 7/12/2016
This monograph has been modified to include the generic and brand name in many instances.

Additional Activase Information

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