Predictors of symptomatic intracranial haemorrhage in off-label thrombolysis: an analysis of the Safe Implementation of Treatments in Stroke registry.

BACKGROUND AND PURPOSE: Intravenous thrombolysis (IVT) is the only approved pharmacological treatment for acute ischemic stroke. Off-label IVT for ischemic stroke is common. We aimed to analyse its safety in a large database. METHODS: This was a retrospective analysis of the safe implementation of treatments in stroke (SITS) thrombolysis registry with regard to 11 off-label criteria according to the European licence for alteplase. Symptomatic intracranial haemorrhage (SICH) according to SITS was defined as primary safety endpoint and SICH according to the European Cooperative Acute Stroke Study (ECASS II) definition and the National Institute of Neurological Disorders and Stroke definition as secondary safety endpoints. Multivariable logistic regression analyses after replacing missing values using multiple imputations were performed. RESULTS: Patients from 793 centres in 44 countries were included, mainly (95%) in Europe. A total of 56 258 patients who were treated with intravenous alteplase were included. Median age was 71 (IQR 61-78) years and median National Institutes of Health Stroke Scale score was 12 (IQR 7-17). A total of 16 740 (30%) patients received off-label IVT and 1037 (1.8%) patients suffered from SICH according to the SITS definition (SICH SITS). Median percentage of missing values per variable was 0.4%. The only two off-label criteria constituting independent positive and negative predictors for SICH SITS were high blood pressure (odds ratio, 1.39; 95% confidence interval, 1.08-1.80; P = 0.012) and minor stroke (odds ratio, 0.51; 95% confidence interval, 0.33-0.78; P = 0.002). Very severe stroke, previous stroke and diabetes, age and high glucose levels were additional independent predictors of SICH according to the ECASS II and National Institute of Neurological Disorders and Stroke definitions. CONCLUSIONS: Thrombolysis appears to be safe with regard to SICH for most of the off-label criteria, especially for minor stroke, but is risky in patients with high blood pressure. Individual risk-benefit evaluation should be performed.

Safety of protocol violations in acute stroke tPA administration.

BACKGROUND: Intravenous (IV) tissue plasminogen activator remains the only approved therapy for acute ischemic stroke (AIS) in the United States; however, less than 10% of patients receive treatment. This is partially because of the large number of contraindications, narrow treatment window, and physician reluctance to deviate from these criteria. METHODS: We retrospectively analyzed consecutive patients who received IV thrombolysis at our stroke center for National Institute of Neurological Disorders and Stroke (NINDS) protocol violations and rates of symptomatic intracerebral hemorrhage (sICH). Other outcome variables included systemic hemorrhage, modified Rankin Scale at discharge, and discharge disposition. RESULTS: A total of 212 patients were identified in our stroke registry between 2009 and 2011 and included in the analysis. Protocol violations occurred in 76 patients (36%). The most common violations were thrombolysis beyond 3 hours (26%), aggressive blood pressure management (15%), elevated prothrombin time (PT) or partial thromboplastin time (PTT) (6.6%), minor or resolving deficits (4.2%), unclear time of onset (3.9%), and stroke within 3 months (3%). There were no significant differences in any of the safety outcomes or discharge disposition between patients with or without protocol violations. Controlling for age, National Institutes of Health Stroke Scale on admission, and glucose on admission, there was no significant increase in sICH (odds ratio: 3.8; 95% confidence interval: .37-38.72) in the patients who had protocol violations. CONCLUSIONS: Despite more than one third of patients receiving thrombolysis with protocol violations, overall rates of hemorrhage remained low and did not differ from those who did not have violations. Our data support the need to expand access to thrombolysis in AIS patients.

Thrombolysis treatment for acute stroke: issues of efficacy and utilization in women.

BACKGROUND: Some studies report that women with ischemic stroke are more likely to benefit from intravenous tissue thrombolysis (IV tPA) treatment, but are less likely to receive the treatment compared with men. We review the literature on sex differences in utilization and efficacy of IV tPA and suggest directions for future studies. METHODS: We identified studies that reported on sex differences in either the utilization or efficacy of IV tPA treatment for acute ischemic stroke. RESULTS: Data from observational studies of IV tPA use show evidence of under-utilization in women, although wide variability between studies suggests that differences are specific to local conditions and populations. Prior analyses of randomized trial data show strong evidence that women but not men receive statistically and clinically significant benefit from IV tPA treatment. Observational studies of the effectiveness of IV tPA treatment in men and women have limited validity because of the absence of comparable control groups. CONCLUSION: There is good evidence that there are clinically important sex differences in both the efficacy and utilization of IV tPA, with women gaining more benefit from treatment than men. The current paradox between greater efficacy but lower utilization of IV tPA in women requires greater attention from the stroke community. Larger placebo-controlled thrombolysis trials, specifically powered to look at sex differences in treatment efficacy, and more studies designed to understand the underlying reasons for the lower utilization of IV tPA in women are required.

Endovascular reperfusion therapy in acute ischaemic stroke.

OBJECTIVES: Endovascular reperfusion therapy in acute ischaemic stroke comprises a number of pharmacological and mechanical procedures. Mechanical embolectomy offers the promise of efficacious treatment for patients in whom pharmacological thrombolysis is contraindicated or might be ineffective. The purpose of this review is to outline endovascular reperfusion therapy in acute ischaemic stroke with focus on mechanical embolectomy. MATERIALS & METHODS: Data on endovascular reperfusion therapy were acquired through searches in MEDLINE 1990-2006 by cross referencing relevant key words. RESULTS: Mechanical embolectomy works well on large-volume proximal occlusions for which there was previously no effective treatment. Early safety trials are promising, efficacy in terms of recanalisation is substantial, and both safety and efficacy is expected to improve with further advances in technology. CONCLUSIONS: Intravenous thrombolysis with tPA revolutionised acute stroke treatment a decade ago. Endovascular reperfusion therapy now offers the promise of a second revolution, expanding the number of patients eligible and the time window open for specific stroke treatment.

Monitoring of glycoprotein products in cell culture lysates using lectin affinity chromatography and capillary HPLC coupled to electrospray linear ion trap-Fourier transform mass spectrometry (LTQ/FTMS).

In this paper, we describe the combination of lectin chromatography with capillary LC coupled to a linear ion trap-Fourier transform mass spectrometer (LTQ/FTMS) to enrich and characterize overexpressed glycoproteins from a cell culture lysate. A well-characterized glycoprotein, recombinant tissue plasminogen activator (rt-PA), was used as a standard, and we demonstrated that the three N-linked glycopeptides (including glycan structures) present in a tryptic digest of the rt-PA standard could be characterized in the new hybrid MS platform. A feature of this approach is that a significant amount of information can be obtained about the carbohydrate structures by direct analysis of the tryptic digest without the need for additional time-consuming sample preparation protocols. A combination of lectins was then studied for improved recovery of captured glycopeptides and was related to the selectivity of different lectins for specific glycosylation motifs. This approach was then extended to the lysate of a cell line routinely used in biotechnology manufacture (Chinese hamster ovary, CHO). This study showed that the combinations of lectins could enrich glycoproteins significantly from a CHO cell lysate. We also demonstrated that with this level of enrichment and with the new hybrid mass spectrometer, we could study the structures of N-linked glycopeptides of rt-PA present in a crude CHO cell lysate, at a ratio of 1:200 (rtPA:total cell lysate protein, w/w) by accurate mass measurement in the FTMS and tandem MSn in the linear ion trap. The generic and high throughput nature of the lectin approach combined with the ability to directly analyze the glycan structures in the tryptic digest suggest that this platform has the potential to routinely monitor glycoprotein products at early stage manufacturing in the biotech industry.

A collaborative study to establish the 3rd International Standard for tissue plasminogen activator.

An international collaborative study was organised to replace the 2nd International Standard (IS) for tissue plasminogen activator (tPA). The 2nd IS for tPA (86/670) was used to calibrate the replacement Standard, which was selected from two candidate materials included in the collaborative study. Participants were provided with five sets of four samples (A, B, C, D) and asked to use sample A (2nd IS, 86/670, 850 IU/ml) to determine the activity of B (86/624, approximately 850 IU/ml), C and D (coded duplicates of the same material, 98/714 approximately 11,000 IU/ml). A total of 14 laboratories returned results from Europe, USA, Japan and Australia, providing data from 60 independent assays. Four laboratories used a reference method based on a published monograph from the European Pharmacopoeia for Alteplase for Injection, 1998, and the remaining 10 used their own method. Fibrin was used as promoter of tPA activity by 12 out of the 14 laboratories, the remaining two used kits where fibrinogen fragments were the promoter. Data from this collaborative study and the previous study to establish the 2nd IS for tPA show that tPA from melanoma cells and recombinant tPA from CHO cells are both suitable materials as International Standards. It was agreed that sample C, D, recombinant tPA, 98/714, be established as the 3rd International Standard for tPA with a potency of 10,000 IU per ampoule, calculated as the mean value from laboratories using fibrin as a promoter of tPA activity. The standard was established by WHO in November 2000.

Alteplase and tenecteplase: applications in the peripheral circulation.

Alteplase (t-PA), a recombinant analogue of human tissue plasminogen activator, became the first genetically engineered thrombolytic approved by the Food and Drug Administration in 1987 for acute myocardial infarction (AMI). In addition to AMI, alteplase is currently approved for the treatment of acute ischemic stroke and pulmonary embolism, and we anticipate approval for catheter clearance in late 2001 in a 2-mg vial configuration. With the withdrawal of human neonatal kidney cell-derived urokinase, alteplase has become an alternative agent in peripheral vascular applications. Because few interventionalists had prior experience with the handling and dosage of alteplase, the Advisory Panel to the Society of Cardiovascular and Interventional Radiology established practice guidelines for use in noncoronary applications. Emerging clinical experience with contemporary dosing regimens shows a safety and efficacy profile similar to urokinase but with significantly reduced drug costs. Tenecteplase (TNK) is a genetically modified version of alteplase. TNK is the only plasminogen activator available that has shown a significantly enhanced safety profile versus alteplase in AMI. Approved for a 5-second, single-bolus injection in AMI, TNK possesses a longer half-life, increased resistance to plasminogen activator inhibitor, and improved fibrin specificity compared with alteplase. Because of its enhanced safety profile, TNK may be a desirable agent for peripheral vascular applications. Initial clinical studies with TNK in acute arterial and venous disease are ongoing. This article outlines the Advisory Panel guidelines for using alteplase and highlights features of tenecteplase.

Combination of a direct thrombin inhibitor and a platelet glycoprotein IIb/IIIa blocking peptide facilitates and maintains reperfusion of platelet-rich thrombus with alteplase.

We sought to determine the efficacy of the combination of argatroban, a direct thrombin inhibitor, and G4120, a platelet glycoprotein (GP) IIb/IIIa blocker, to enhance thrombolysis with alteplase. Platelet-rich thrombus in the rabbit arterial thrombosis model is relatively resistant to alteplase despite the addition of aspirin and heparin. The adjunctive use of either direct thrombin inhibitors or GP IIb/IIIa inhibitors in thrombolysis has been investigated with encouraging, but limited, success. The usefulness of combining both agents as adjunctive therapy to thrombolysis has not been fully explored. Following platelet-rich thrombus formation in the rabbit, argatroban (3 mg/kg), G4120 (0.5 mg/kg), G4120 plus heparin (200 U/kg), or G4120 plus argatroban were intravenously infused over 60 minutes. Alteplase was given as intravenous boluses (0.45 mg/kg) at 15-minute intervals up to 4 doses or until reperfusion. Blood flow and bleeding time were monitored for 2 hours. The combination of G4120 plus argatroban resulted in a persistent patency in 5 of 7 animals compared with 0 of 6 for argatroban alone (p=0.02), 1 of 6 for G4120 alone (p=0.08), and 2 of 6 for G4120 plus heparin (p=0.2). Although during the infusion the bleeding times were longer in the groups that received G4120 (26+/-7.7 minutes vs. 14+/-10 minutes, p<0.05), by the end of the experiment there were no statistically significant differences. Similarly, during the infusion the activated partial thromboplastin times (aPTT) was higher in groups that received heparin or argatroban (99+/-51 seconds vs. 32+/-7.6 seconds, p<0.001), but by the end of the experiment the aPTTs had returned to close to baseline in all groups except the G4120 plus heparin group. These results suggest that lysis of platelet-rich thrombus with alteplase requires the addition of both potent platelet and thrombin inhibitors. Specifically designed agents, G4120 and argatroban, are effective without additional increased risk for bleeding.

A sensitive ELISA for human tissue-type plasminogen activator applicable to the study of acute release from cultured human endothelial cells.

The development of a highly sensitive, enzyme-linked immunosorbent assay (ELISA) for tissue-type plasminogen activator (tPA) is described. The use of a biotin-avidin system resulted in a detection limit of 10 pg of tPA per ml, which is 50 to 150 times more sensitive than commercially-available ELISAs. Free tPA and tPA complexed to PA inhibitor type-1 were detected with equal efficiency. The ELISA proved suitable for measuring tPA antigen in conditioned media and in cell extracts. The intra-assay coefficient of variation varied in six different experiments from 1.9% to 3.4% in the range 0 to 250 pg of tPA antigen per ml. The inter-assay coefficient of variation was 7% (n = 6). The ELISA was used to study the acute release of tPA from human umbilical vein endothelial cells in vitro. Upon addition of thrombin (1 NIH U/ml) to endothelial cells, tPA was rapidly released into the medium, the highest release occurring during the first minute. Concomitantly, the tPA concentration in the cell extracts decreased. Evidence is presented that tPA is released from an intracellular source.

Utilizing cardiovascular data bases to guide the balance of cost and quality.

Cardiovascular administrators are being asked to focus on quality, cost-efficient operations of their service lines, to market that service, to secure business through managed-care contracting and to increase direct referral volume.

Peptide mapping for detecting variants in protein products.

The genetic stability of biotechnology production systems is of importance in evaluating the safety and efficacy of protein products. The analysis methods currently available for assessing the genetic stability of such systems are limited by the complexity of the eukaryotic genome and by their inability to predict the effects of post-transcriptional and post-translational events, such as glycosylation or host cell protein level changes, on the protein produced. Therefore, it is important to focus attention on the protein product itself in evaluating product consistency rather than on nucleotide sequence analysis for genetic stability of the production systems involved. Peptide mapping has arisen as the best method for the analysis of proteins as a surrogate measure of genetic stability. This method uses known chemical reactions or enzymes to cleave the protein at specific sites, resulting in discrete peptides whose structure and composition can be readily compared to that of the theoretical protein coded for by the DNA sequence of its gene. Peptide mapping, which is capable of detecting single amino acid changes in a molecule, can also be used for determining glycosylation sites. Peptide mapping requires sophisticated chromatographic techniques and equipment, and is limited to molecules of m.w. of c. 100,000. The method also requires careful validation to limit the potential for misinterpretation of artifactual peaks. Despite its limitations, no better method currently exists to evaluate product consistency and, thereby, the genetic stability of recombinant products.

A collaborative study to establish a U.S. reference for tissue plasminogen activator (t-PA).

In 1987 the Second International Standard for tissue plasminogen activator (t-PA) was established by the World Health Organization following an international collaborative study. At that time, the Center for Biologics Evaluation and Research (CBER) decided to establish a national reference t-PA to be used in lot release potency testing of Alteplase, a licensed t-PA biological or of other t-PAs in development. A candidate recombinant t-PA (rt-PA) preparation was donated by Genentech, Inc. (South San Francisco, California) for this purpose and a collaborative study was launched to calibrate this material against the 2nd I.S. Four laboratories (including the Center for Biologics Evaluation and Research (CBER) and three manufacturers) participated in the study to establish the potency of the rt-PA preparation using a clot lysis assay. The results indicate that the potency of the U.S. reference for t-PA is 2900 international units (IU) per vial.

The potency of tissue-type plasminogen activator (TPA) determined with chromogen and clot-lysis assays.

An assessment was made of two methods for determining the potency of tissue-type plasminogen activator (TPA). A chromogenic microtitre plate assay was established which contained TPA, plasminogen, a synthetic plasmin substrate (H-D-valyl-L-leucyl-L-lysyl-p-nitroaniline dihydrochloride, S2251) and any one of the following stimulators: native fibrinogen, enzymatic and chemical digests of fibrinogen, poly-D-lysine (PDL) and chemical derivatives of the latter. The chromogen assay was compared with an automated clot-lysis (turbidimetric) assay for sensitivity, reproducibility and validity for potency determination. Reference preparations of TPA were titrated in both assays: in the chromogen assay the dose-response curves were non-parallel, whereas parallelism was observed in the clot-lysis assay. Thus, the chromogen assay was restricted in its applicability and disqualified from any routine regulatory use. The potency of individual lots of recombinant (r)TPA could only be estimated in International Units (IU) of TPA activity with the automated clot-lysis assay and the potency values obtained (IU/vial) were in remarkably close agreement with the manufacturers' values.

A collaborative study to establish the 2nd international standard for tissue plasminogen activator (t-PA).

An international collaborative study involving ten laboratories located in eight different countries was undertaken in order to replace the current International Standard (I.S.) for tissue plasminogen activator (t-PA). Two lyophilised candidate preparations of high purity were assessed in comparison with the current I.S. for t-PA using only a clot lysis assay. One preparation (coded 86/670) was purified from a cultured melanoma cell supernatant and was about 98% single chain t-PA while the other preparation (coded 86/624) was derived from Chinese hamster ovary (CHO) cells following DNA recombinant procedures and was 75% single chain t-PA. Both candidate preparations of t-PA compared in quite a satisfactory manner with the current I.S. from the viewpoint of the biometrics of parallel line bioassays and both preparations were quite stable for long periods at low temperatures and stable from up to 1 month at temperatures of 20 degrees and 38 degrees C. Both fulfil the criteria to serve as a satisfactory 2nd International Standard for t-PA. The Fibrinolysis Subcommittee of the International Committee for Thrombosis and Haemostasis recommended the melanoma source t-PA (86/670) as the next I.S. in order to maintain continuity with the 1st I.S. which was also a melanoma-type preparation. The data from the ten laboratories indicated that each ampoule of the new proposed standard contains 850 international units of t-PA activity by the clot lysis assay. It is planned to present the results of this study to the Expert Committee on Biological Standardization of the World Health Organization at its next meeting and to request that the preparation to t-PA, coded 86/670, be established as the 2nd International Standard for t-PA.