Thrombolytic Therapy: Current Clinical Practice

Major Bleeding During Thrombolytic Therapy for Acute Lower Limb Ischaemia: Value of Laboratory Tests for Clinical Decision Making, 17 Years of Experience

OBJECTIVE

Regular measurement of fibrinogen as dose guidance in catheter directed thrombolysis (CDT) for acute limb ischaemia (ALI) has recently been dropped from European guidelines based on inconsistent literature. This study aimed to determine whether low fibrinogen levels and high activated partial thromboplastin time (APTT) are associated with an increased major bleeding risk during CDT.

METHODS

All consecutive patients treated with CDT for ALI in two Dutch hospitals between January 2004 and April 2021 were analysed retrospectively. Patients were treated with two dosing regimens (low dose: 50 000 IU/hour; high dose: 100 000 IU/hour) of urokinase and, after 2018, with a single low dose regimen of alteplase (rtPA) due to urokinase manufacturing problems. The incidence of major bleeding and associated APTT and fibrinogen levels were reviewed from patient charts.

RESULTS

Of the 443 included cases, 277 underwent CDT with urokinase and 166 with rtPA. The incidence of major bleeding in the whole cohort was 7%. Patients with a fibrinogen levels < 1.0 g/L developed more major bleeding than those in whom the fibrinogen level did not drop below 1.0 g/L (15% vs. 6%; p = .041). Systemic heparinisation during CDT or high (> 80 seconds) APTT were not significantly associated with major bleeding. Angiographic success (47% vs. 72%; p = .003) and 30 day amputation free survival (53% vs. 82%; p < .001) were lower for cases with major bleeding. Older age (odds ratio [OR] 1.06, 95% confidence interval [CI] 1.02 - 1.11), cardiac history (OR 3.35, 95% CI 1.39 - 8.06), high dose regimens (≥ 75 000 IU/hour urokinase; OR 2.67, 95% CI 1.18 - 6.04), and fibrinogen values < 1.0 g/L (OR 5.59, 95% CI 1.98 - 15.77) were independent predictors for major bleeding during CDT.

CONCLUSION

High dose thrombolytic regimens and fibrinogen levels of ≤ 1.0 g/L are associated with more major bleeding during thrombolytic therapy. Major bleeding significantly worsened the clinical outcome. A prospective comparative study is needed to assess the benefit of monitoring fibrinogen levels.

A prospective, randomized, placebo-controlled, double-blind trial about safety and efficacy of combined treatment with alteplase (rt-PA) and Cerebrolysin in acute ischaemic hemispheric stroke

BACKGROUND

The neurotrophic drug Cerebrolysin accelerated recovery and prevented acute neuronal damage in preclinical models of ischaemia. Previous clinical trials support therapeutic effects in stroke patients. The study investigated whether the combination with alteplase and Cerebrolysin is safe and can further reduce disability after acute ischaemic stroke.

METHODS

This placebo-controlled, double-blind trial involved 119 patients with acute ischaemic hemispheric stroke, randomly assigned to a combined treatment with alteplase plus Cerebrolysin or placebo (administered 1 h after thrombolytic treatment) starting within three-hours after onset of symptoms. A daily i.v. infusion of 30 ml Cerebrolysin or placebo was given for 10 consecutive days. Primary outcome was the modified Rankin Scale at day 90. A sequential design with interim analyses was applied.

RESULTS

The third interim analysis did not show a benefit in the modified Rankin Scale for Cerebrolysin on day 90 compared to placebo and the study was stopped. The National Institutes of Health Stroke Scale responder analysis (secondary outcome measure) showed significantly more patients with an improvement of 6 or more points (or a total score of 0 or 1) after two-, five-, 10, and 30 days in the Cerebrolysin group. Similar trends were observed for the modified Rankin Scale responder analysis without achieving statistical significance. There was no difference between treatment groups regarding adverse events.

CONCLUSIONS

The combination of Cerebrolysin with recombinant tissue-Plasminogen Activator is safe for treatment of acute ischaemic stroke but did not improve outcome at day 90. During the treatment period with Cerebrolysin (10 days), significantly more patients had a favourable response in neurological outcome measures (National Institutes of Health Stroke Scale) as compared to the placebo group.

Soluble expression of active recombinant human tissue plasminogen activator derivative (K2S) in Escherichia coli

CONTEXT

The kringle 2 plus serine protease domains (K2S) of human tissue plasminogen activator (tPA) is an efficacious thrombolytic drug, which has been used to treat heart attacks and strokes by breaking up the clots that cause them. It has nine disulfide bridges, which are needed for proper folding and be the bottleneck in improving the production in the Escherichia coli system. So far, few reports have described the production of soluble active K2S from E. coli.

OBJECTIVE

To achieve high-level expression of active K2S in the E. coli system.

MATERIALS AND METHODS

The DNA fragment coding for K2S was fused with the E. coli disulfide isomerase DsbC. The constructed fusion protein was expressed in E. coli, and then purified with the Ni(2+)-chelating affinity chromatography. K2S was released by cleavage with Factor Xa protease, and the thrombolytic activity was determined using the fibrin plate assay.

RESULTS

The fusion protein DsbC-K2S was found in the culture supernatant of recombinant E. coli as a soluble form of ~40%. The result of fibrinolysis fibrin plate assay showed that the purified recombinant K2S exhibited significant fibrinolysis activity in vitro.

DISCUSSION AND CONCLUSION

These works provided a novel approach for the production of active K2S in E. coli without the requirements of in vitro refolding process, and might establish a significant foundation for the following production of K2S.

Monitoring of Functional Plasminogen in the Blood of Patients on Fibrinolytics

There are no reliable data on functional plasminogen in the blood of patients receiving fibrinolytic treatment. Here, artifactual in vitro changes of functional plasminogen were prevented by arginine stabilization blood samples of myocardial infarction patients: 12 received 36.4 mg reteplase in bolus, and 1 patient received 100 mg tissue plasminogen activator in continuous infusion. Arginine (1.5 M, 1.3 mL, pH 8.7) was used to stabilize 2.6 mL ethylenediaminetetraacetic acid-blood. The arginine-stabilized plasma was analyzed with a functional oxidative assay for plasminogen. Functional plasminogen decreased within 2 minutes of reteplase treatment by about 40% and by about 80% after 60 minutes. Lowest plasminogen concentrations were found in plasmas with highest plasmin activities. Chloramine oxidation of purified Glu-plasminogen increased its activation by urokinase up to 3-fold. Arginine stabilization allows reliable determinations of functional plasminogen in the blood of patients receiving fibrinolytics, enabling the rapid diagnosis of prothrombotic plasminogen consumption. The present findings support the profibrinolytic action of chloramines.

Neuroprotection of Cerebrolysin in tissue culture models of brain ischemia: post lesion application indicates a wide therapeutic window

All attempts to reduce neuronal damage after acute brain ischemia by the use of neuroprotective compounds have failed to prove efficacy in clinical trials so far. One of the main reasons might be the relatively narrow time window for intervention. In this study 2 different tissue culture models of ischemia, excitotoxic lesion by the use of glutamate and oxygen-glucose deprivation (OGD), were used to investigate the effects of delayed application of Cerebrolysin (Cere) on neuronal survival. This drug consists of low molecular weight peptides with neuroprotective and neurotrophic properties similar to naturally occurring growth factors. After both types of lesion, acute as well as delayed treatment with Cere resulted in a dose dependent and significant rescue of neurons. In the model of excitotoxic cell death significant drug effects were found even when the treatment started with a delay of 96 hours after addition of glutamate. In the OGD model pronounced effects were found after 48 hours delay of treatment, and even after 72 hours a small but significant rescue of neurons was detected. The neuroprotective effects of a single addition of Cerebrolysin to the culture medium resulted in significant protection until end of the experiments which was up to 2 weeks after the initial lesion. A shift of the efficacious dosages from low to high concentrations indicates that most likely active compounds are used up, indicating that multiple dosing might even increase the effect size. In conclusion the results indicate that Cere displays a relatively wide therapeutic time window which might be explained by a combination of acute neuroprotective properties and neurotrophic efficacy.