A faster-acting and more potent form of tissue plasminogen activator

Tenecteplase versus alteplase for the treatment of acute ischemic stroke: a meta-analysis of randomized controlled trials

OBJECTIVES

Tenecteplase, a modified variant of alteplase with greater fibrin specificity and longer plasma half-life, may have better efficacy and safety than alteplase in patients with acute ischemic stroke (AIS). We aimed to compare the benefits and risks of tenecteplase versus alteplase in the treatment of AIS.

METHODS

Electronic databases were searched up to 10 February 2023 for randomized controlled trials evaluating the effect of tenecteplase versus alteplase in the treatment of AIS. The primary outcome was functional outcome at 90 days, and secondary outcomes including the symptomatic intracranial haemorrhage (SICH), and major neurological improvement. Subgroup analysis was performed based on the different dosage of tenecteplase.

RESULTS

Ten studies with a total of 5123 patients were analysed in this meta-analysis. Overall, no significant difference between tenecteplase and alteplase was observed for functional outcome at 90 days (excellent: OR 1.08, 95%CI 0.93-1.26, I2 = 26%; good: OR 1.04, 95%CI 0.83-1.30, I2 = 56%; poor: OR 0.95, 95%CI 0.75-1.21, I2 = 31%), SICH (OR 1.12, 95%CI 0.79-1.59, I2 = 0%), and early major neurological improvement (OR 1.26, 95%CI 0.80-1.96, I2 = 65%). The subgroup analysis suggested that the 0.25 mg/kg dose of tenecteplase had potentially greater efficacy and lower symptomatic intracerebral haemorrhage risk compared with 0.25 mg/kg dose tenecteplase.

CONCLUSIONS

Among AIS patients, there was no significant difference on clinical outcomes between tenecteplase and alteplase. Subgroup analysis demonstrated that 0.25 mg/kg doses of tenecteplase were more beneficial than 0.4 mg/kg doses of tenecteplase. Further studies are required to identify the optimal dosage of tenecteplase.

Comprehensive Review of Tenecteplase for Thrombolysis in Acute Ischemic Stroke

Although intravenous thrombolysis with alteplase remains the primary treatment for acute ischemic stroke, tenecteplase has shown potential advantages over alteplase. Animal studies have demonstrated the favorable pharmacokinetics and pharmacodynamics of tenecteplase. Moreover, it is easier to administer. Clinical trials have demonstrated that tenecteplase is not inferior to alteplase and may even be superior in cases of acute ischemic stroke with large vessel occlusion. Current evidence supports the time and cost benefits of tenecteplase, suggesting that it could potentially replace alteplase as the main option for thrombolytic therapy, especially in patients with large vessel occlusion.

Tenecteplase versus alteplase for acute ischemic stroke: a systematic review and meta-analysis of randomized and non-randomized studies

OBJECTIVE

Alteplase is the current standard of care for acute ischemic stroke. Tenecteplase is a newer fibrinolytic agent with preferable administration and lower costs; however, its comparative effectiveness to alteplase remains uncertain. We set out to perform a systematic review and meta-analysis to establish the benefits and harms of tenecteplase versus alteplase for acute ischemic stroke.

METHODS

We searched PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov from inception to April 2023 for randomized and non-randomized studies that compared tenecteplase versus alteplase for acute ischemic stroke. Paired reviewers independently assessed risk of bias and extracted data. We performed both conventional meta-analyses and Bayesian network meta-analyses (NMA) with random-effects models and used the GRADE approach to evaluate the certainty of evidence. Our primary efficacy outcome was excellent functional outcome at 3 months, defined as a score of 0-1 on the modified Rankin Scale. Our primary safety outcomes were symptomatic intracranial hemorrhage and all-cause mortality.

RESULTS

Thirty-six studies were eligible for review, including 12 randomized (n = 5533) and 24 non-randomized studies (n = 44,956). Moderate certainty evidence showed that there was no difference between tenecteplase and alteplase in increasing the proportion of patients achieving excellent functional outcome at 3 months (odds ratio [OR], 1.10; 95% CI 0.98-1.23; risk difference [RD] 2.4%, 95% CI - 0.5 to 5.2), while moderate certainty evidence from NMA suggested that 0.25 mg/kg tenecteplase significantly improved excellent functional outcome at 3 months (OR, 1.16; 95% credible interval 1.02-1.32). Moderate certainty evidence showed that, compared to alteplase, tenecteplase may make little to no difference in the prevalence of symptomatic intracranial hemorrhage (OR, 1.12; 95% CI 0.79-1.59; RD 0.3%, 95% CI - 0.5 to 1.4), and probably reduces all-cause mortality (adjusted odds ratio [aOR], 0.44; 95% CI 0.30-0.64; RD - 4.6%; 95% CI - 5.8 to - 2.9).

CONCLUSIONS

Moderate certainty evidence suggested that there was little to no difference between tenecteplase and alteplase in increasing the proportion of patients achieving excellent functional outcome at 3 months and the risk of symptomatic intracranial hemorrhage, while compared to alteplase, tenecteplase probably reduce all-cause mortality. Administration of 0.25 mg/kg tenecteplase after acute ischemic stroke is suggestive of increasing the proportion of patients that achieve excellent functional outcome at 3 months.

Real-world data of tenecteplase vs. alteplase in the treatment of acute ischemic stroke: a single-center analysis

Background

This retrospective observational cohort study aimed to evaluate whether tenecteplase's use for acute ischemic stroke (AIS) has time management advantages and clinical benefits.

Methods

144 AIS patients treated with alteplase and 120 with tenecteplase were included. We compared baseline clinical characteristics, key reperfusion therapy time indices [onset-to-treatment time (OTT), door-to-needle time (DNT), and door-to-puncture time (DPT)] and clinical outcomes (24-h post-thrombolysis NIHSS improvement, and intracranial hemorrhage incidence) between the groups using univariate analysis. We assessed hospital stay durations and used binary logistic regression to examine tenecteplase's association with DNT and DPT target times, NIHSS improvement, and intracranial hemorrhage.

Results

Baseline characteristics showed no significant differences except hyperlipidemia and atrial fibrillation. OTT (133 vs. 163.72, p = 0.001), DNT (36.5 vs. 50, p < 0.001) and DPT (117 vs. 193, p = 0.002) were significantly faster in the tenecteplase group. The rates of DNT ≤ 45 min (65.83% vs. 40.44%, p < 0.001) and DPT ≤ 120 min (59.09% vs. 13.79%, p = 0.001) were significantly higher in the tenecteplase group. Tenecteplase was an independent predictor of achieving target DNT (OR 2.951, 95% CI 1.732-5.030; p < 0.001) and DPT (OR 7.867, 95% CI 1.290-47.991; p = 0.025). Clinically, the proportion NIHSS improvement 24 h post-thrombolysis was higher in the tenecteplase group (64.17% vs. 50%, p = 0.024). No significant differences were observed in symptomatic intracranial hemorrhage (sICH) or any intracranial hemorrhage (ICH). Patients receiving tenecteplase had shorter hospital stays (6 vs. 8 days, p < 0.001). Tenecteplase was an independent predictor of NIHSS improvement at 24 h (OR 1.715, 95% CI 1.011-2.908; p = 0.045). There was no significant association between thrombolytic choice and sICH or any ICH.

Conclusion

Tenecteplase significantly reduced DNT and DPT. It was associated with early neurological function improvement (at 24 h), without compromising safety compared to alteplase. The findings support tenecteplase's application in AIS.

Multicenter exploration of tenecteplase transition factors: A quantitative analysis

BACKGROUND

Tenecteplase (TNK) is gaining recognition as a novel therapy for acute ischemic stroke (AIS). Despite TNK offering a longer half-life, time and cost saving benefits and comparable treatment and safety profiles to Alteplase (ALT), the adoption of TNK as a treatment for AIS presents challenges for hospital systems.

OBJECTIVE

Identify barriers and facilitators of TNK implementation at acute care hospitals in Texas.

METHODS

This prospective survey used open-ended questions and Likert statements generated from content experts and informed by qualitative research. Stroke clinicians and nurses working at 40 different hospitals in Texas were surveyed using a virtual platform.

RESULTS

The 40 hospitals had a median of 34 (IQR 24.5-49) emergency department beds and 42.5 (IQR 23.5-64.5) inpatient stroke beds with 506.5 (IQR 350-797.5) annual stroke admissions. Fifty percent of the hospitals were Comprehensive Stroke Centers, and 18 (45 %) were solely using ALT for treatment of eligible AIS patients. Primary facilitators to TNK transition were team buy-in and a willingness of stroke physicians, nurses, and pharmacists to adopt TNK. Leading barriers were lack of clinical evidence supporting TNK safety profile inadequate evidence supporting TNK use and a lack of American Heart Association guidelines support for TNK administration in all AIS cases.

CONCLUSION

Understanding common barriers and facilitators to TNK adoption can assist acute care hospitals deciding to implement TNK as a treatment for AIS. These findings will be used to design a TNK adoption Toolkit, utilizing implementation science techniques, to address identified obstacles and to leverage facilitators.

Diverse origins of fibrinolytic enzymes: A comprehensive review

Fibrinolytic enzymes cleave fibrin which plays a crucial role in thrombus formation which otherwise leads to cardiovascular diseases. While different fibrinolytic enzymes have been purified, only a few have been utilized as clinical and therapeutic agents; hence, the search continues for a fibrinolytic enzyme with high specificity, fewer side effects, and one that can be mass-produced at a lower cost with a higher yield. In this context, this review discusses the physiological mechanism of thrombus formation and fibrinolysis, and current thrombolytic drugs in use. Additionally, an overview of the optimization, production, and purification of fibrinolytic enzymes and the role of Artificial Intelligence (AI) in optimization and the patents granted is provided. This review classifies microbial as well as non-microbial fibrinolytic enzymes isolated from food sources, including fermented foods and non-food sources, highlighting their advantages and disadvantages. Despite holding immense potential for the discovery of novel fibrinolytic enzymes, only a few fermented food sources limited to Asian countries have been studied, necessitating the research on fibrinolytic enzymes from fermented foods of other regions. This review will aid researchers in selecting optimal sources for screening fibrinolytic enzymes and is the first one to provide insights and draw a link between the implication of source selection and in vivo application.

Efficacy and safety outcomes of Tenecteplase versus Alteplase for thrombolysis of acute ischemic stroke: A meta-analysis of 9 randomized controlled trials

BACKGROUND

In recent years, Tenecteplase (TNK), a genetically modified variant of alteplase, has been verified as a potential substitute for alteplase in the reperfusion therapy of acute ischemic stroke (AIS). Given the emergence of new randomized controlled trials (RCTs) of this subject, a meta-analysis was conducted to evaluate the present comparative evidence regarding the efficacy and safety outcomes of TNK and alteplase in thrombolysis for AIS.

METHODS

Following predefined inclusion criteria, we searched the databases of PubMed, Web of Science, and Cochrane Library. RCTs satisfying our inclusion criteria were selected for meta-analysis. Outcome indicators were categorized into efficacy outcomes (early vessel recanalization, excellent recovery, good recovery and early neurological improvement) and safety outcomes (poor recovery, symptomatic intracerebral hemorrhage, parenchymal hemorrhage type 2(PH2) post thrombolysis, and mortality). We extracted data on efficacy outcomes and safety outcomes for patients with AIS in the TNK group at a dose of 0.25 mg/kg and the alteplase group at a dose of 0.9 mg/kg, and expressed the relative risks between the 2 groups as odds ratios (ORs) and 95% confidence intervals (CIs) using the Mantel-Haenszel method. For further insight, we performed a network meta-analysis using a Bayesian framework to compare different doses of TNK (0.1, 0.25, 0.32, and 0.4 mg/kg) with alteplase (0.9 mg/kg).

RESULTS

A total of 2994 patients in 9 RCTs comparing efficacy and safety outcomes in patients with AIS treated with TNK and alteplase were included. In a pairwise analysis of TNK 0.25 mg/kg and alteplase 0.9 mg/kg, regarding efficacy outcomes, the aggregated results show that TNK 0.25 mg/kg statistically significant increased early vessel recanalization (N = 368, TNK vs. alteplase, OR: 2.07,95%CI: [1.19,3.59], I2 = 0%) and excellent recovery (N = 3548, TNK vs. alteplase, OR: 1.15,95%CI: [1.01,1.32], I2 = 0%). There was no significant difference in good recovery (N = 3486, TNK vs. alteplase, OR: 1.38,95%CI: [0.89,2.15], I2 = 84%) or early neurological improvement (N = 1686, TNK vs. alteplase, OR: 1.06,95%CI: [0.87,1.28], I2 = 24%) between the TNK 0.25 mg/kg group and the alteplase 0.9 mg/kg group. In the safety outcomes, pooled results showed no significant difference in poor recovery (N = 3548, TNK vs. alteplase, OR: 0.94,95%CI: [0.81,1.10], I2 = 0%) and symptomatic intracerebral hemorrhage (N = 3567, TNK vs. alteplase, OR: 1.06,95%CI: [0.70,1.60], I2 = 0%) and PH2(N = 3103, TNK vs. alteplase, OR: 1.26,95%CI:[0.39,4.07], I2 = 56%)and mortality (N = 3447, TNK vs. alteplase, OR: 0.99,95%CI: [0.80,1.23], I2 = 33%) between the TNK group and the alteplase group. In a network meta-analysis, competing treatments were not significantly different from one another (TNK 0.1 mg/kg, TNK 0.25 mg/kg, TNK 0.32 mg/kg, TNK 0.4 mg/kg, alteplase 0.9 mg/kg) in either efficacy outcomes or safety outcomes.

CONCLUSION

In this analysis of 9 RCTs in patients with AIS, TNK 0.25 mg/kg was comparable to alteplase 0.9 mg/kg from the perspective of efficacy outcomes and safety outcomes after thrombolysis within 4.5 h of AIS occurrence.

Comparing Low- or Standard-Dose Alteplase in Endovascular Thrombectomy: Insights From a Nationwide Registry

BACKGROUND

Timely intravenous thrombolysis and endovascular thrombectomy are the standard reperfusion treatments for large vessel occlusion stroke. Currently, it is unknown whether a low-dose thrombolytic agent (0.6 mg/kg alteplase) can offer similar efficacy to the standard dose (0.9 mg/kg alteplase).

METHODS

We enrolled consecutive patients in the multicenter Taiwan Registry of Endovascular Thrombectomy for Acute Ischemic Stroke who had received combined thrombolysis (within 4.5 hours of onset) and thrombectomy treatment from January 2019 to April 2023. The choice of low- or standard-dose alteplase was based on the physician's discretion. The outcomes included successful reperfusion (modified Thrombolysis in Cerebral Infarction score, 2b-3), symptomatic intracerebral hemorrhage, 90-day modified Rankin Scale score, and 90-day mortality. The outcomes between the 2 groups were compared using multivariable logistic regression and inverse probability of treatment weighting-adjusted analysis.

RESULTS

Among the 2242 patients in the Taiwan Registry of Endovascular Thrombectomy for Acute Ischemic Stroke, 734 (33%) received intravenous alteplase. Patients in the low-dose group (n=360) were older, had more women, more atrial fibrillation, and longer onset-to-needle time compared with the standard-dose group (n=374). In comparison to low-dose alteplase, standard-dose alteplase was associated with a lower rate of successful reperfusion (81% versus 87%; adjusted odds ratio, 0.63 [95% CI, 0.40-0.98]), a numerically higher incidence of symptomatic intracerebral hemorrhage (6.7% versus 3.9%; adjusted odds ratio, 1.81 [95% CI, 0.88-3.69]), but better 90-day modified Rankin Scale score (functional independence [modified Rankin Scale score, 0-2], 47% versus 31%; adjusted odds ratio, 1.91 [95% CI, 1.28-2.86]), and a numerically lower mortality rate (9% versus 15%; adjusted odds ratio, 0.73 [95% CI, 0.43-1.25]) after adjusting for covariates. Similar results were observed in the inverse probability of treatment weighting-adjusted models. The results were consistent across predefined subgroups and age strata.

CONCLUSIONS

Despite the lower rate of successful reperfusion and higher risk of symptomatic intracerebral hemorrhage with standard-dose alteplase, standard-dose alteplase was associated with a better functional outcome in patients receiving combined thrombolysis and thrombectomy.

Rationale and design of Tenecteplase Reperfusion Therapy in Acute Ischaemic Cerebrovascular Events III (TRACE III): a randomised, phase III, open-label, controlled trial

BACKGROUND AND PURPOSE

Recombinant human TNK tissue-type plasminogen activator (rhTNK-tPA) was not inferior to alteplase for ischaemic stroke within 4.5 hours. Our study aimed to investigate the efficacy and safety of rhTNK-tPA in patients who had an ischaemic stroke due to large vessel occlusion (LVO) of anterior circulation beyond 4.5 hours.

METHODS AND DESIGN

Tenecteplase Reperfusion Therapy in Acute Ischaemic Cerebrovascular Events-III (TRACE III) is a multicentre, prospective, randomised, open-label, blind endpoint, controlled clinical trial. Patients who had an ischaemic stroke due to anterior circulation LVO (internal carotid artery, middle cerebral artery M1 and M2 segments) within 4.5-24 hours from last known well (including wake-up stroke and no witness stroke) and with salvageable tissue (ischaemic core volume <70 mL, mismatch ratio ≥1.8 and mismatch volume ≥15 mL) based on CT perfusion or MRI perfusion-weighted imaging (PWI) were included and randomised to rhTNK-tPA 0.25 mg/kg (single bolus) to a maximum of 25 mg or standard medical therapy. Specially, we will exclude patients who are intended for direct thrombectomy. All will be followed up for 90 days.

STUDY OUTCOMES

Primary efficacy outcome is modified Rankin Scale (mRS) score ≤1 at 90 days. Secondary efficacy outcomes include ordinal distribution of mRS at 90 days, major neurological improvement defined by a decrease ≥8 points compared with the initial deficit or a score ≤1 on the National Institutes of Health Stroke Scale (NIHSS) at 72 hours, mRS score ≤2 at 90 days, the rate of improvement on Tmax >6 s at 24 hours and NIHSS score change from baseline at 7 days. Safety outcomes are symptomatic intracerebral haemorrhage within 36 hours and mortality at 90 days.

DISCUSSION

TRACE III will provide evidence for the efficacy and safety of rhTNK-tPA in patients who had an ischaemic strokes due to anterior circulation LVO beyond 4.5 hours.

TRIAL REGISTRATION NUMBER

NCT05141305.

Intra-arterial tenecteplase during thrombectomy for acute stroke (BRETIS-TNK II): rationale and design

BACKGROUND

Our recent pilot study suggests intra-arterial tenecteplase (TNK) during the first pass of endovascular treatment (EVT) seems safe, may increase first-pass reperfusion and good outcome in acute ischaemic stroke (AIS) patients with large-vessel occlusion (LVO).

AIMS

To determine the efficacy and safety of intra-arterial TNK administration during EVT in AIS-LVO patients presenting up to 24 hours from symptom onset.

SAMPLE SIZE ESTIMATES

A maximum of 380 patients are required to test the superiority hypothesis with 80% power according to a two-side 0.05 level of significance, stratified by age, gender, baseline systolic blood pressure, prestroke modified Rankin Scale (mRS), baseline National Institute of Health stroke scale, baseline ASPECTS, time from onset to groin puncture, intravenous thrombolysis before EVT, stroke territory and stroke aetiology.

DESIGN

Intra-arterial TNK during thrombectomy for acute stroke (BRETIS-TNK II) study is a prospective, randomised, adaptive enrichment, open-label, blinded end point, multicentre study. Eligible AIS-LVO patients are randomly assigned into the experimental group and control group with a ratio of 1:1. The experimental group will be treated with intra-arterial infusion of TNK during EVT. The control group will be treated with standard EVT.

OUTCOME

The primary end point is a favourable outcome, defined as an mRS score of 0-2 at 90 days. The primary safety end point is symptomatic intracranial haemorrhage within 48 hours, which is defined as an increase in the National Institutes of Health Stroke Scale score of ≥4 points as a result of the intracranial haemorrhage.

CONCLUSIONS

The results of BRETIS-TNK II will provide evidence for the efficacy and safety of intra-arterial TNK administration during EVT in AIS patients with LVO.

Anti-stroke biologics: from recombinant proteins to stem cells and organoids

The use of biologics in various diseases has dramatically increased in recent years. Stroke, a cerebrovascular disease, is the second most common cause of death, and the leading cause of disability with high morbidity worldwide. For biologics applied in the treatment of acute ischaemic stroke, alteplase is the only thrombolytic agent. Meanwhile, current clinical trials show that two recombinant proteins, tenecteplase and non-immunogenic staphylokinase, are most promising as new thrombolytic agents for acute ischaemic stroke therapy. In addition, stem cell-based therapy, which uses stem cells or organoids for stroke treatment, has shown promising results in preclinical and early clinical studies. These strategies for acute ischaemic stroke mainly rely on the unique properties of undifferentiated cells to facilitate tissue repair and regeneration. However, there is a still considerable journey ahead before these approaches become routine clinical use. This includes optimising cell delivery methods, determining the ideal cell type and dosage, and addressing long-term safety concerns. This review introduces the current or promising recombinant proteins for thrombolysis therapy in ischaemic stroke and highlights the promise and challenges of stem cells and cerebral organoids in stroke therapy.

The fibrinolysis renaissance

Fibrinolysis is the system primarily responsible for removal of fibrin deposits and blood clots in the vasculature. The terminal enzyme in the pathway, plasmin, is formed from its circulating precursor, plasminogen. Fibrin is by far the most legendary substrate, but plasmin is notoriously prolific and is known to cleave many other proteins and participate in the activation of other proteolytic systems. Fibrinolysis is often overshadowed by the coagulation system and viewed as a simplistic poorer relation. However, the primordial plasminogen activators evolved alongside the complement system, approximately 70 million years before coagulation saw the light of day. It is highly likely that the plasminogen activation system evolved with its roots in primordial immunity. Almost all immune cells harbor at least one of a dozen plasminogen receptors that allow plasmin formation on the cell surface that in turn modulates immune cell behavior. Similarly, numerous pathogens express their own plasminogen activators or contain surface proteins that provide binding sites for host plasminogen. The fibrinolytic system has been harnessed for clinical medicine for many decades with the development of thrombolytic drugs and antifibrinolytic agents. Our refined understanding and appreciation of the fibrinolytic system and its alliance with infection and immunity and beyond are paving the way for new developments and interest in novel therapeutics and applications. One must ponder as to whether the nomenclature of the system hampered our understanding, by focusing on fibrin, rather than the complex myriad of interactions and substrates of the plasminogen activation system.

Efficacy and safety of tenecteplase in comparison to alteplase in acute ischemic stroke: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Alteplase is the standard medical therapy for acute ischemic stroke (AIS) patients who present within 4.5 h of symptom onset. Tenecteplase is a modified alteplase variant with pharmacological and practical advantages over alteplase. Many trials have investigated the efficacy and safety of tenecteplase against alteplase. This systematic review and meta-analysis aimed to compare the efficacy and safety of tenecteplase to alteplase across randomized controlled trials.

METHOD

Medline, Embase, and Cochrane CENTRAL were used to search the related articles until February 20, 2023. Randomized controlled trials (RCTs) that compared the effectiveness and safety of tenecteplase against alteplase for AIS patients were included. Screening, risk of bias assessment, and data extraction were performed following PRISMA guidelines. Data were pooled using a random-effect model.

RESULTS

Ten RCTs were included, with a total of 5123 patients. There was no significant difference between the two interventions in modified rankin scale 0-1 (mRS 0-1) (RR= 1.04, 95% CI [0.99-1.10], P = 0.11, I2 =0%) and early neurological improvement (RR= 1.06, 95% CI [0.97-1.15], P = 0.21, I2 =35). There was no difference in the rates of symptomatic intracranial hemorrhage (RR= 1.18, 95% CI [0.84-1.65], P = 0.35, I2 = 0%). Tenecteplase was associated with significantly higher complete recanalization rate compared to alteplase (RR= 1.17, 95% CI [1.00-1.36], P = 0.05, I2 =0%). For large vessel occlusion (LVO) patients assigned to tenecteplase, there was a significant improvement in mRS 0-1 (RR= 1.28, 95% CI [1.07-1.52], P = 0.006, I2 =0%).

CONCLUSION

Based on our meta-analysis, tenecteplase has similar efficacy and safety to alteplase, with a more promising effect in patients with LVO.

A Systematic Review of the Efficacy and Safety of Tenecteplase Versus Streptokinase in the Management of Myocardial Infarction in Developing Countries

Myocardial infarction (MI) is a significant cause of morbidity and mortality in low- and middle-income countries. Fibrinolytic agents and percutaneous coronary intervention (PCI) are the main approaches for the recanalization and reperfusion of the myocardium following MI. Many studies have shown that PCI is superior to thrombolytics due to better outcomes and decreased mortality. Nevertheless, PCI's mortality gain over thrombolysis decreases as the time between presentation and PCI procedure increases. Furthermore, PCI is not widely available in most developing countries; thus, it cannot be delivered promptly. Most patients in developing countries cannot afford the cost of PCI. Thus, thrombolytic therapy remains essential to managing MI in developing countries and should not be disregarded. Tenecteplase (TNK) and streptokinase (SK) are the two most widely used fibrinolytics in managing MI in underdeveloped nations. Despite their widespread availability, comparative studies on them have been inconclusive. This study aims to review the available literature on the effectiveness and safety of TNK versus SK in managing MI in resource-poor nations. The study is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) extension and analyzed according to Cochrane guidelines on synthesis without meta-analysis. A comprehensive literature search for studies comparing TNK and STK was conducted on EMBASE, Cochrane Library, Web of Science, CINAHL, Scopus, Google Scholar, and Ovid version of MEDLINE databases. A reference list of the eligible articles and systematic reviews was also screened. A narrative synthesis of the available data was done by representing the data on the effect direction plot, followed by vote counting. Of the 2284 references retrieved from the databases, only 17 studies met the inclusion criteria and were selected for final analysis. The study suggested that TNK is more effective in complete ST-segment resolution (80% vs 10% on the effect direction plot) and symptom relief (80% vs 20%) than SK. SK and TNK were comparable in achieving successful fibrinolysis (50% vs 50%). For the safety parameters, TNK is associated with a lesser risk of major bleeding than SK (88.9% vs 11.1%) and minor bleeding (25% vs 75%). SK was linked with a higher risk of hypotension/shock (77.8% vs 11.1%) and anaphylaxis/allergy (100% vs 0%). Long-term mortality was higher in the SK arm (100% vs 0%). In-hospital mortality is comparable between the two agents (37.5% vs 37.5%). There is conflicting evidence regarding other safety and efficacy endpoints. Compared to SK, TNK results in better complete ST-segment resolution and symptom relief. A higher risk of long-term mortality, increased risk of major and minor bleeding, hypotension, and allergy/anaphylaxis was observed in patients who received SK. Both agents were comparable in terms of in-hospital mortality and successful fibrinolysis. Controversy exists regarding which agent is linked with increased risk of 30-35-day mortality benefit and stroke. Randomized controlled trials (RCTs) with large sample sizes are needed to establish TNK vs SK superiority in efficacy and safety. The long-term duration of follow-up of the mortality rate of the two agents is also essential, as most patients in these regions cannot afford the recommended PCI post-fibrinolysis.

Identification, characterization, and engineering of glycosylation in thrombolyticsa

Cardiovascular diseases, such as myocardial infarction, ischemic stroke, and pulmonary embolism, are the most common causes of disability and death worldwide. Blood clot hydrolysis by thrombolytic enzymes and thrombectomy are key clinical interventions. The most widely used thrombolytic enzyme is alteplase, which has been used in clinical practice since 1986. Another clinically used thrombolytic protein is tenecteplase, which has modified epitopes and engineered glycosylation sites, suggesting that carbohydrate modification in thrombolytic enzymes is a viable strategy for their improvement. This comprehensive review summarizes current knowledge on computational and experimental identification of glycosylation sites and glycan identity, together with methods used for their reengineering. Practical examples from previous studies focus on modification of glycosylations in thrombolytics, e.g., alteplase, tenecteplase, reteplase, urokinase, saruplase, and desmoteplase. Collected clinical data on these glycoproteins demonstrate the great potential of this engineering strategy. Outstanding combinatorics originating from multiple glycosylation sites and the vast variety of covalently attached glycan species can be addressed by directed evolution or rational design. Directed evolution pipelines would benefit from more efficient cell-free expression and high-throughput screening assays, while rational design must employ structure prediction by machine learning and in silico characterization by supercomputing. Perspectives on challenges and opportunities for improvement of thrombolytic enzymes by engineering and evolution of protein glycosylation are provided.

Evolving Thrombolytics: from Alteplase to Tenecteplase

Alteplase has been the primary thrombolytic used in the treatment of acute ischemic stroke since thrombolysis was first established as an effective treatment of acute ischemic stroke in 1995. Tenecteplase, a genetically modified tissue plasminogen activator, has gained attention as an attractive alternative to alteplase given its practical workflow advantages and possible superior efficacy in large vessel recanalization. As more data is analyzed both from randomized trials and non-randomized patient registries, there is mounting support that tenecteplase appears to be at least equally, if not more, safe and potentially more effective than alteplase in the treatment of acute ischemic stroke. Randomized trials investigating tenecteplase in the delayed treatment window and with thrombectomy are ongoing, and their results are eagerly awaited. This paper provides an overview of completed and ongoing randomized trials and nonrandomized studies analyzing tenecteplase in the treatment of acute ischemic stroke. Results reviewed support the safe use of tenecteplase in clinical practice.

Rescue thrombolysis for medium vessel occlusion (RESCUE-TNK): Rationale and design of a phase 2 randomized trial

Background

The best reperfusion strategy for medium-sized vessel occlusion (MeVO) is not well established. Given the proven treatment effect of intra-arterial thrombolysis in patients with large vessel occlusion (LVO), we hypothesized that intra-arterial tenecteplase (TNK) could increase the recanalization rate of MeVO and thus improve clinical outcome.

Aims

To explore the safety and efficacy of intra-arterial TNK in patients with MeVO.

Sample size estimates

A maximum of 80 patients are required to test the superiority hypothesis, using power = 80% and α = 0.025 to conduct the one-sided test.

Design

Rescue treatment for mEdium veSsel oCclUsion by intra-artErial TNK (RESCUE-TNK) is a pilot, randomized, open-label, blinded end point, and multicenter trial. Eligible patients including primary MeVO as detected by the first DSA examination or secondary MeVO after endovascular treatment (EVT) for LVO will be assigned into the experimental group and control group as a ratio of 1:1. The experimental group will be treated with intra-arterial TNK (0.2–0.3 mg/min, for 20–30 min) via a microcatheter placed proximal to the site of occlusion, and the control group will be treated with routine therapy. Both groups of patients will be given standard stroke care based on the guidelines.

Outcome

The primary efficacy end point is successful recanalization of MeVO, defined as the expanded treatment in cerebral ischemia (eTICI) score 2b67-3 after the procedure, while the primary safety end point is symptomatic intracranial hemorrhage (sICH), defined as National Institutes of Health Stroke Scale score increase ≥4 caused by intracranial hemorrhage within 24 (−6/+24) hours after randomization.

Conclusion

The results of RESCUE-TNK will provide evidence for the efficacy and safety of intra-arterial TNK in the recanalization of patients with MeVO.

Tenecteplase in acute ischemic stroke: Review of the literature and expert consensus from the French Neurovascular Society

BACKGROUND

Intravenous alteplase is the only thrombolytic treatment approved for patients with acute ischemic stroke (AIS). Although no randomized controlled trial (RCT) has shown the superiority of tenecteplase over alteplase in AIS, tenecteplase is increasingly used off-label in Stroke Units. The purpose of the present work was to provide an up-to-date set of expert consensus statements on the use of tenecteplase in AIS.

METHODS

Members of the working group were selected by the French Neurovascular Society. RCTs comparing tenecteplase and alteplase in the treatment of AIS were reviewed. Recent meta-analysis and real-life experience data on tenecteplase published until 30th October 2021 were also analyzed. After a description of the available data, we tried to answer the subsequent questions about the use of tenecteplase in AIS: What dosage of tenecteplase should be preferred? How effective is tenecteplase for cerebral artery recanalization? What is the clinical effectiveness of tenecteplase? What is the therapeutic safety of tenecteplase? What are the benefits associated with tenecteplase ease of use? Then expert consensus statements for tenecteplase use were submitted. In October 2021 the working group was asked to review and revise the manuscript. In November 2021, the current version of the manuscript was approved.

EXPERT CONSENSUS

A set of three expert consensus statements for the use of tenecteplase within 4.5hours of symptom onset in AIS patients were issued: (1) It is reasonable to use tenecteplase 0.25mg/kg when mechanical thrombectomy (MT) is planned. (2) Tenecteplase 0.25mg/kg can be used as an alternative to alteplase 0.9mg/kg in patients with medium- or small-vessel occlusion not retrievable with MT. (3) Tenecteplase 0.25mg/kg could be considered as an alternative to alteplase 0.9mg/kg in patients without vessel occlusion.

CONCLUSIONS

These expert consensus statements could provide a framework to guide the clinical decision-making process for the use of tenecteplase according to admission characteristics of AIS patients. However, existing data are limited, requiring inclusions in ongoing RCTs or real-life registries.

Comparison of dosing errors between tenecteplase and alteplase for management of acute ischemic stroke

BACKGROUND

Acute ischemic stroke (AIS) is a medical emergency leading to morbidity and mortality. Thrombolytic therapy is currently the mainstay for the management of AIS owing to its improvement in neurologic function at 3 months.

OBJECTIVES

The objective of this study was to compare the frequency of dosing errors made with tenecteplase versus alteplase administration in management of AIS. The secondary objectives evaluated efficacy outcomes of intensive care unit length of stay (LOS), hospital LOS, and time from door to needle and safety outcomes of bleeding and all-cause mortality between groups.

METHODS

This multicenter retrospective cohort study included patients with AIS treated with thrombolytics (tenecteplase or alteplase). The study evaluated patients at 9 different hospitals in a Texas Network between August 2018 and August 2020.

RESULTS

There were 3808 patients evaluated for inclusion and 359 were included: 171 in the tenecteplase group and 188 in the alteplase group. There were no differences found in dosing errors between tenecteplase and alteplase (25.7% vs. 32.4%, P = 0.16). There was no difference in all-cause mortality (tenecteplase 1.8% vs. alteplase 5.3%, P = 0.09) or bleeding events (tenecteplase 8.8% vs. alteplase 7.4%, P = 0.64). Patients who received tenecteplase had improved door to needle time < 60 minutes (tenecteplase 60% vs. alteplase 49%, P = 0.04).

CONCLUSION

There was no difference in dosing errors between tenecteplase and alteplase for the management of AIS. Tenecteplase was associated with shorter door to needle times, which may be caused by simpler administration times. Institutions could consider strategies to mitigate dosing errors for thrombolytic therapies.

Different dosing regimens of Tenecteplase in acute ischemic stroke: A network meta-analysis of the clinical evidence

Introduction:

Acute ischemic stroke remains the major cause of death and disability and conclusive evidence of Tenecteplase in treating stroke is lacking.

Objective:

To conduct a meta-analysis to determine whether Tenecteplase produces better outcomes than Alteplase and a network meta-analysis comparing the different dosing regimens of Tenecteplase.

Methods:

Searches were made in MEDLINE, CENTRAL, and ClinicalTrials.gov. The outcome measures are recanalization, early neurological improvement, functional outcomes at 90 days (modified Rankin Scale 0–1 and 0–2), intracranial hemorrhage, symptomatic intracranial hemorrhage, and mortality within 90 days from treatment.

Results:

Fourteen studies are included in the meta-analyses and 18 studies in the network meta-analyses. In the meta-analysis, Tenecteplase 0.25 mg/kg has significant results in early neurological improvement (OR = 2.35, and 95% CI = 1.16–4.72) and excellent functional outcome (OR = 1.20, and 95% CI = 1.02–1.42). In the network meta-analysis, Tenecteplase 0.25 mg/kg produces significant results in early neurological improvement (OR = 1.52 [95% CI = 1.13–2.05], p-value = 0.01), functional outcomes (mRS 0–1 and 0–2) (OR = 1.19 [95% CI = 1.03–1.37], p-value = 0.02; OR = 1.21 [95% CI = 1.05–1.39], p-value = 0.01; respectively) and mortality (OR = 0.78 [95% CI = 0.64–0.96], p-value = 0.02) whereas Tenecteplase 0.40 mg/kg increases the chances of symptomatic intracranial hemorrhage (OR = 2.35 [95% CI = 1.19–4.64], p-value = 0.01).

Conclusion:

While not conclusive, our study lends evidence to 0.25 mg/kg Tenecteplase dose for ischemic stroke treatment. Further randomized trials need to be done to validate this finding.

Registration:

International prospective register of systematic reviews (PROSPERO) – CRD42022339774 URL: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=339774

Alteplase or tenecteplase for thrombolysis in ischemic stroke: An illustrated review

Intravenous thrombolysis is a standard of care treatment for patients with acute ischemic stroke. Tissue plasminogen activator (tPA) has been the main thrombolytic agent used since the publication of the seminal National Institutes of Neurological Disorders and Stroke trial in 1995. There is now mounting evidence to support the routine use of Tenecteplase (TNK) to treat acute ischemic stroke. TNK is a genetically modified tPA with higher fibrin specificity, longer half‐life, and reduced systemic coagulopathy. In this illustrated review, we compare the indications, doses, mechanisms of action, efficacy and safety of TNK and tPA. We provide an overview of published clinical trials studying TNK in acute ischemic stroke, including dose‐escalation studies and head‐to‐head comparisons with tPA. Finally, we summarize current acute stroke guideline recommendations and suggest treatment algorithms to manage the two main complications of intravenous thrombolysis: symptomatic intracerebral hemorrhage and angioedema.

A novel ex vivo approach for measuring plasminogen activation upon established plasma clots

Background

The fibrinolytic system plays a critical role in maintaining hemostasis. Central to fibrinolysis is the degradation of fibrin by plasmin, produced in the circulation following the activation of plasminogen by plasminogen activators (PAs). Accurately measuring the plasminogen activation rate is vital for the understanding of fibrinolytic processes, particularly in the context of thrombolysis. Yet, due to the insoluble nature of fibrin, in vitro and ex vivo investigations of PA-mediated plasminogen activation have proven challenging. As researchers frequently adopt soluble fibrinogen fragments and/or alter the experimental system beyond what is physiologically relevant, they limit the validation and interpretation of their findings. Here, we present a novel, high-throughput assay for measuring plasminogen activation rates on natural, plasma-derived fibrin that optimally simulates in vivo conditions.

Method

Human plasma was used as the source of plasmin(ogen) and fibrin(ogen). "Halo-shaped" plasma clots were produced in a 96-well plate using a thrombin-containing clotting mixture, ensuring that an optically compatible and plasma-free center is maintained in each well. Subsequent additions of a plasmin chromogenic substrate and different PAs were followed by absorbance measurements over time to extract the corresponding enzyme kinetics information.

Results and Discussion

Validation experiments demonstrated the capability of our approach to accurately model fibrin-dependent and -independent plasminogen activation as well as sensitively detect variations in plasminogen and fibrinogen plasma levels.

Conclusion

This assay allows a straightforward, yet powerful, measurement of plasminogen activation rates on established plasma clots, with the capability of properly assessing fibrin- and non-fibrin-dependent plasminogen activation by various therapeutic PAs.

Basic science research opportunities in thrombosis and hemostasis: Communication from the SSC of the ISTH

Bleeding and thrombosis are major clinical problems with high morbidity and mortality. Treatment modalities for these diseases have improved in recent years, but there are many clinical questions remaining and a need to advance diagnosis, management, and therapeutic options. Basic research plays a fundamental role in understanding normal and disease processes, yet this sector has observed a steady decline in funding prospects thereby hindering support for studies of mechanisms of disease and therapeutic development opportunities. With the financial constraints faced by basic scientists, the ISTH organized a basic science task force (BSTF), comprising Scientific and Standardization Committee subcommittee chairs and co-chairs, to identify research opportunities for basic science in hemostasis and thrombosis. The goal of the BSTF was to develop a set of recommended priorities to build support in the thrombosis and hemostasis community and to inform ISTH basic science programs and policy making. The BSTF identified three principal opportunity areas that were of significant overarching relevance: mechanisms causing bleeding, innate immunity and thrombosis, and venous thrombosis. Within these, five fundamental research areas were highlighted: blood rheology, platelet biogenesis, cellular contributions to thrombosis and hemostasis, structure-function protein analyses, and visualization of hemostasis. This position paper discusses the importance and relevance of these opportunities and research areas, and the rationale for their inclusion. These findings have implications for the future of fundamental research in thrombosis and hemostasis to make transformative scientific discoveries and tackle key clinical questions. This will permit better understanding, prevention, diagnosis, and treatment of hemostatic and thrombotic conditions.

Tenecteplase in Pulmonary Embolism Patients: A Meta-Analysis and Systematic Review

Objective

To assess the efficacy and safety of tenecteplase in patients with pulmonary embolism (PE).

Methods

We completed the literature search on May 31, 2021 using PubMed, EMBASE and the Web of Science. Analyses were conducted according to PE risk stratification, study design and duration of follow-up. The pooled risk ratios (RRs) and its 95% confident intervals (CIs) for death and major bleeding were calculated using a random-effect model.

Results

A total of six studies, with four randomized controlled trials (RCTs) and two cohort studies, were included in this study out of the 160 studies retrieved. For patients with high-risk PE, tenecteplase increased 30-day survival rate (16% vs 6%; P = 0.005) and did not increase the incidence of bleeding (6% vs 5%; P = 0.73). For patients with intermediate-risk PE, four RCTs suggested that tenecteplase reduced right ventricular insufficiency at 24h early in the onset and the incidence of hemodynamic failure without affecting mortality in a short/long-term [<30 days RR = 0.83, 95% CI (0.47, 1.46);≥30 days RR = 1.04, 95% CI (0.88, 1.22)]. However, tenecteplase was associated with high bleeding risk [<30 days RR = 1.79, 95% CI (1.61, 2.00); ≥30 days RR = 1.28, 95% CI (0.62, 2.64)].

Conclusions

Tenecteplase may represent a promising candidate for patients with high risk PE. However, tenecteplase is not recommended for patients with intermediate-risk PE because of high bleeding risk. More large-scale studies focused on tenecteplase are still needed for PE patients.

Tenecteplase and Alteplase for Thrombolysis of Acute Ischemic Stroke within 4.5 Hours: An Efficacy and Safety Study

Objective

To compare the efficacy and safety of thrombolysis using Tenecteplase (TNK) versus alteplase in acute ischaemic stroke (AIS) patients within 4.5-hour window period.

Methods

This retrospective study involved the collection of data from consecutive AIS patients who underwent thrombolysis in the Department of Neurology at a tertiary care university hospital, between May 2018 to January 2021. Data including clinical history, neurological assessment using modified Rankin score (mRS), National Institutes of Health Stroke Scale (NIHSS), brain neuroimaging, treatment, and outcome details were collected. The primary efficacy outcome was the proportion of patients with good functional recovery (mRS of 0-2) at 90 days of follow-up.

Results

Total of 42 patients with AIS underwent thrombolysis, of which 19 received alteplase and 23 got TNK. The median (range) onset to door time [120 (20-210) versus 120 (30-210) minutes; P = 0.823] and median (range) onset to needle time [150 (60-255) versus 160 (50-240) minutes; P = 0.779] were comparable in both alteplase and TNK groups, respectively. The primary outcome of good functional recovery (mRS ≤2) at 3 months was observed in more than half the patients in each group and was comparable (P = 0.701). Post-thrombolysis complications including cerebral haemorrhage (symptomatic or asymptomatic) were comparable between the two groups (31.6% vs 30.4%; P = 0.936), except a significantly higher proportion of patients on TNK required mechanical ventilation (10.5% v/s 43.5%; P = 0.019).

Conclusions

This study showed a comparable efficacy and safety profile of alteplase and TNK in thrombolysis of AIS throughout the 4.5 hours window period. Moreover, the ease of administration and better pharmacodynamic properties favors tenecteplase.

Emerging agents for the treatment and prevention of stroke: progress in clinical trials

INTRODUCTION

Recent years have witnessed unprecedented progress in stroke care, but unmet needs persist regarding the efficacy of acute treatment and secondary prevention. Novel approaches are being tested to enhance the efficacy of thrombolysis or provide neuroprotection in non-thrombolized patients.

AREAS COVERED

The current review highlights pharmaceutical agents under evaluation in clinical trials concerning the acute, subacute, and chronic phase post-stroke. We examine the evidence in favor of tenecteplase as an alternative thrombolytic drug to alteplase, nerinetide as a promising neuroprotective agent, and glibenclamide for reducing edema in malignant hemispheric infarction. We discuss the use of ticagrelor and the promising novel category of factor XI inhibitors in the subacute phase after stroke. We offer our insights on combined rivaroxaban and antiplatelet therapy, PCSK-9 inhibitors, and other non-statin hypolipidemic agents, as well as novel antidiabetic agents that have been shown to reduce cardiovascular events in the long-term.

EXPERT OPINION

Current approaches in stroke treatment and stroke prevention have already transformed stroke care from a linear one-for-all treatment paradigm to a more individualized approach that targets specific patient subgroups with novel pharmaceutical agents. This tendency enriches the therapeutic armamentarium with novel agents developed for specific stroke subgroups.

ABBREVIATIONS

IVT: intravenous thrombolysis; RCTs: randomized-controlled clinical trials; TNK: Tenecteplase; COVID-19: Coronavirus 2019 Disease; EXTEND-IA TNK: The Tenecteplase versus Alteplase Before Endovascular Therapy for Ischemic Stroke trial; AIS: acute ischemic stroke; NNT: number needed to treat; MT: mechanical thrombectomy; sICH: symptomatic intracranial hemorrhage; mRS: modified Rankin Scale; AHA/ASA: American Heart Association/American Stroke Association; ESO: European Stroke Organization; NA-1: Nerinetide; ENACT: Evaluating Neuroprotection in Aneurysm Coiling Therapy; CTA: CT angiography; TIA: transient ischemic attack; CHANCE: Clopidogrel in High-risk patients with Acute Non-disabling Cerebrovascular Events; LOF: loss-of-function; PRINCE: Platelet Reactivity in Acute Nondisabling Cerebrovascular Events; THALES: Acute Stroke or Transient Ischemic Attack Treated with Ticagrelor and ASA [acetylsalicylic acid] for Prevention of Stroke and Death; CHANCE-2: Clopidogrel With Aspirin in High-risk Patients With Acute Non-disabling Cerebrovascular Events II; FXI: Factor XI; PACIFIC-STROKE: Program of Anticoagulation via Inhibition of FXIa by the Oral Compound BAY 2433334-NonCardioembolic Stroke study; COMPASS: Cardiovascular Outcomes for People Using Anticoagulation Strategies; CANTOS-ICAD: Combination Antithrombotic Treatment for Prevention of Recurrent Ischemic Stroke in Intracranial Atherosclerotic Disease; SAMMPRIS: Stenting and Aggressive Medical Therapy for Preventing Recurrent Stroke in Intracranial Stenosis; WASID: Warfarin-Aspirin Symptomatic Intracranial Disease; SPARCL: Stroke Prevention by Aggressive Reduction in Cholesterol Levels; LDL-C: low-density lipoprotein cholesterol; TST: Treat Stroke to Target; IMPROVE-IT: Improved Reduction of Outcomes: Vytorin Efficacy International Trial; PCSK9: proprotein convertase subtilisin-kexin type 9; FOURIER: Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk; CLEAR: Cholesterol Lowering via Bempedoic acid, an ACL-inhibiting Regimen; REDUCE-IT: Reduction of Cardiovascular Events With EPA Intervention Trial; STRENGTH: Outcomes Study to Assess STatin Residual Risk Reduction With EpaNova in HiGh CV Risk PatienTs With Hypertriglyceridemia; ACCORD: Action to Control Cardiovascular Risk in Diabetes; ADVANCE: Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation; VADT: Veterans Affairs Diabetes Trial; GLP-1R: Glucagon-like peptide-1 receptor; SGLT2: sodium-glucose cotransporter 2; CONVINCE: COlchicine for preventioN of Vascular Inflammation in Non-CardioEmbolic stroke; PROBE: Prospective Randomized Open-label Blinded Endpoint assessment.

Use of Exogenous Enzymes in Human Therapy: Approved Drugs and Potential Applications

The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.

Acute Stroke Management: Overview and Recent Updates

Stroke is a leading cause of morbidity and mortality in the United States. Whether hemorrhagic or ischemic, stroke leads to severe long-term disability. Prior to the mid-1990s, the treatment offered to a patient who presented with an acute stroke was mainly limited to antiplatelets. The lack of adequate treatment, in particular, one without reperfusion contributed to the disability that ensued. There have been many advances in stroke care within the past two decades, especially with the acute management of ischemic stroke. Even with these advances, it is quite alarming that only a fraction of patients receives acute stroke treatment. Numerous trials were conducted to broaden treatment eligibility in hopes that more patients can be treated acutely and safely. These trials have tested both the time window for IV tPA and endovascular therapy (EVT). Acute stroke management is moving from a universal time window approach to a concept of tissue preservation. Specifically, preserving cerebral blood flow, the penumbra, and reducing the risk of a second event. This movement is being executed through the use of multimodal CT and MRI, as well as individualizing treatment to our patients. Minimizing the initial effect of stroke changes the outcome and leads to an increased likelihood of functional independence. In this review, we discuss the recent updates of acute ischemic stroke management in regards to mechanical thrombectomy as well as thrombolytics including tenecteplase.

Fibrin(ogen) as a Therapeutic Target: Opportunities and Challenges

Fibrinogen is one of the key molecular players in haemostasis. Thrombin-mediated release of fibrinopeptides from fibrinogen converts this soluble protein into a network of fibrin fibres that form a building block for blood clots. Thrombin-activated factor XIII further crosslinks the fibrin fibres and incorporates antifibrinolytic proteins into the network, thus stabilising the clot. The conversion of fibrinogen to fibrin also exposes binding sites for fibrinolytic proteins to limit clot formation and avoid unwanted extension of the fibrin fibres. Altered clot structure and/or incorporation of antifibrinolytic proteins into fibrin networks disturbs the delicate equilibrium between clot formation and lysis, resulting in either unstable clots (predisposing to bleeding events) or persistent clots that are resistant to lysis (increasing risk of thrombosis). In this review, we discuss the factors responsible for alterations in fibrin(ogen) that can modulate clot stability, in turn predisposing to abnormal haemostasis. We also explore the mechanistic pathways that may allow the use of fibrinogen as a potential therapeutic target to treat vascular thrombosis or bleeding disorders. Better understanding of fibrinogen function will help to devise future effective and safe therapies to modulate thrombosis and bleeding risk, while maintaining the fine balance between clot formation and lysis.

The Fibrinolytic System: Mysteries and Opportunities

The deposition and removal of fibrin has been the primary role of coagulation and fibrinolysis, respectively. There is also little doubt that these 2 enzyme cascades influence each other given they share the same serine protease family ancestry and changes to 1 arm of the hemostatic pathway would influence the other. The fibrinolytic system in particular has also been known for its capacity to clear various non-fibrin proteins and to activate other enzyme systems, including complement and the contact pathway. Furthermore, it can also convert a number of growth factors into their mature, active forms. More recent findings have extended the reach of this system even further. Here we will review some of these developments and also provide an account of the influence of individual players of the fibrinolytic (plasminogen activating) pathway in relation to physiological and pathophysiological events, including aging and metabolism.

Precision targeting of the plasminogen activator inhibitor-1 mechanism increases efficacy of fibrinolytic therapy in empyema

Plasminogen activator inhibitor‐1 (PAI‐1) is an endogenous irreversible inhibitor of tissue‐type (tPA) and urokinase (uPA) plasminogen activators. PAI‐1‐targeted fibrinolytic therapy (PAI‐1‐TFT) is designed to decrease the therapeutic dose of tPA and uPA, attenuating the risk of bleeding and other complications. Docking site peptide (DSP) mimics the part of the PAI‐1 reactive center loop that interacts with plasminogen activators, thereby affecting the PAI‐1 mechanism. We used DSP for PAI‐1‐TFT in two rabbit models: chemically induced pleural injury and Streptococcus pneumoniae induced empyema. These models feature different levels of inflammation and PAI‐1 expression. PAI‐1‐TFT with DSP (2.0 mg/kg) converted ineffective doses of single chain (sc) tPA (72.5 µg/kg) and scuPA (62.5 µg/kg) into effective ones in chemically induced pleural injury. DSP (2.0 mg/kg) was ineffective in S. pneumoniae empyema, where the level of PAI‐1 is an order of magnitude higher. DSP dose escalation to 8.0 mg/kg resulted in effective PAI‐1‐TFT with 0.25 mg/kg sctPA (1/8th of the effective dose of sctPA alone) in empyema. There was no increase in the efficacy of scuPA. PAI‐1‐TFT with DSP increases the efficacy of fibrinolytic therapy up to 8‐fold in chemically induced (sctPA and scuPA) and infectious (sctPA) pleural injury in rabbits. PAI‐1 is a valid molecular target in our model of S. pneumoniae empyema in rabbits, which closely recapitulates key characteristics of empyema in humans. Low‐dose PAI‐1‐TFT is a novel interventional strategy that offers the potential to improve fibrinolytic therapy for empyema in clinical practice.

Adjunctive Intracoronary Fibrinolytic Therapy During Primary Percutaneous Coronary Intervention

Despite routinely restoring epicardial coronary patency, with primary percutaneous coronary intervention (PCI), microvascular obstruction affects approximately half of patients and confers an adverse prognosis. There are no evidence-based treatments for microvascular obstruction. A key contributor to microvascular obstruction is distal embolisation and microvascular thrombi. Adjunctive intracoronary fibrinolytic therapy may reduce thrombotic burden, potentially reducing distal embolisation of atherothrombotic debris to the microcirculation. In this review, the evidence from published randomised trials on the effects of adjunctive intracoronary fibrinolytic therapy during primary PCI is critically appraised, the ongoing randomised trials are described, and conclusions are made from the available evidence. Clinical uncertainties, to be addressed by future research, are highlighted.

Recombinant Soluble Corin Improves Cardiac Function in Mouse Models of Heart Failure

Background

Corin is a transmembrane protease that activates ANP and BNP (atrial and B‐type natriuretic peptides). Impaired corin expression and function are associated with heart failure. In this study, we characterized a soluble form of corin (sCorin) and examined its effects on cardiac morphology and function in mouse heart failure models.

Methods and Results

sCorin, consisting of the full‐length extracellular fragment of human corin with an engineered activation site, was expressed in Chinese hamster ovary cells, purified from the conditioned medium with affinity chromatography, and characterized in pro‐ANP processing assays in vitro and pharmacokinetic studies in mice. Effects of sCorin on mouse models of heart failure induced by left coronary artery ligation and transverse aortic constriction were assessed by ELISA analysis of plasma markers, histologic examination, and echocardiography. We showed that purified and activated sCorin converted pro‐ANP to ANP that stimulated cGMP production in cultured cells. In mice, intravenously and intraperitoneally administered sCorin had plasma half‐lives of 3.5±0.1 and 8.3±0.3 hour, respectively. In the mouse heart failure models, intraperitoneal injection of sCorin increased plasma ANP, BNP, and cGMP levels; lowered plasma levels of NT‐proANP (N‐terminal‐pro‐ANP), angiotensin II, and aldosterone; reduced cardiac hypertrophy and fibrosis; and improved cardiac function.

Conclusions

We show that sCorin treatment enhanced natriuretic peptide processing and activity, suppressed the renin‐angiotensin‐aldosterone system, and improved cardiac morphology and function in mice with failing hearts.

Off-label use of intravenous thrombolysis for acute ischemic stroke: a critical appraisal of randomized and real-world evidence

Intravenous thrombolysis (IVT) represents the only systemic reperfusion therapy able to reverse neurological deficit in patients with acute ischemic stroke (AIS). Despite its effectiveness in patients with or without large vessel occlusion, it can be offered only to a minority of them, because of the short therapeutic window and additional contraindications derived from stringent but arbitrary inclusion and exclusion criteria used in landmark randomized controlled clinical trials. Many absolute or relative contraindications lead to disparities between the official drug label and guidelines or expert recommendations. Based on recent advances in neuroimaging and evidence from cohort studies, off-label use of IVT is increasingly incorporated into the daily practice of many stroke centers. They relate to extension of therapeutic time windows, and expansion of indications in co-existing conditions originally listed in exclusion criteria, such as use of alternative thrombolytic agents, pre-treatment with antiplatelets, anticoagulants or low molecular weight heparins. In this narrative review, we summarize recent randomized and real-world data on the safety and efficacy of off-label use of IVT for AIS. We also make some practical recommendations to stroke physicians regarding the off-label use of thrombolytic agents in complex and uncommon presentations of AIS or other conditions mimicking acute cerebral ischemia. Finally, we provide guidance on the risks and benefits of IVT in numerous AIS subgroups, where equipoise exists and guidelines and treatment practices vary.

Enzyme engineering and its industrial applications

Recently, there has been an increase in the demand for enzymes with modified activity, specificity, and stability. Enzyme engineering is an important tool to meet the demand for enzymes adjusted to different industrial processes. Knowledge of the structure and function of enzymes guides the choice of the best strategy for engineering enzymes. Each enzyme engineering strategy, such as rational design, directed evolution, and semi-rational design, has specific applications, as well as limitations, which must be considered when choosing a suitable strategy. Engineered enzymes can be optimized for different industrial applications by choosing the appropriate strategy. This review features engineered enzymes that have been applied in food, animal feed, pharmaceuticals, medical applications, bioremediation, biofuels, and detergents.

Endovascular Treatment for Lower Extremity Deep Vein Thrombosis: An Overview

Lower extremity deep vein thrombosis (DVT) is a serious medical condition that can result in local pain and gait disturbance. DVT progression can also lead to death or major disability as a result of pulmonary embolism, postthrombotic syndrome, or limb amputation. However, early thrombus removal can rapidly relieve symptoms and prevent disease progression. Various endovascular procedures have been developed in the recent years to treat DVT, and endovascular treatment has been established as one of the major therapeutic methods to treat lower extremity DVT. However, the treatment of lower extremity DVT varies according to the disease duration, location of affected vessels, and the presence of symptoms. This article reviews and discusses effective endovascular treatment methods for lower extremity DVT.

Development and Testing of Thrombolytics in Stroke

Despite recent advances in recanalization therapy, mechanical thrombectomy will never be a treatment for every ischemic stroke because access to mechanical thrombectomy is still limited in many countries. Moreover, many ischemic strokes are caused by occlusion of cerebral arteries that cannot be reached by intra-arterial catheters. Reperfusion using thrombolytic agents will therefore remain an important therapy for hyperacute ischemic stroke. However, thrombolytic drugs have shown limited efficacy and notable hemorrhagic complication rates, leaving room for improvement. A comprehensive understanding of basic and clinical research pipelines as well as the current status of thrombolytic therapy will help facilitate the development of new thrombolytics. Compared with alteplase, an ideal thrombolytic agent is expected to provide faster reperfusion in more patients; prevent re-occlusions; have higher fibrin specificity for selective activation of clot-bound plasminogen to decrease bleeding complications; be retained in the blood for a longer time to minimize dosage and allow administration as a single bolus; be more resistant to inhibitors; and be less antigenic for repetitive usage. Here, we review the currently available thrombolytics, strategies for the development of new clot-dissolving substances, and the assessment of thrombolytic efficacies in vitro and in vivo.

Tenecteplase for Acute Ischemic Stroke Treatment

The introduction of thrombolytic therapy in the 1990s has transformed acute ischemic stroke treatment. Thus far, intravenous recombinant tissue plasminogen activator (rt-PA) also known as alteplase is the only thrombolytic proven to be efficacious and approved by the United States Food and Drug Administration. But the thrombolytic agent tenecteplase (TNK) is emerging as a potential replacement for rt-PA. TNK has greater fibrin specificity, slower clearance, and higher resistance to plasminogen activator inhibitor-1 than rt-PA. Hence, TNK has the potential to provide superior lysis with fewer hemorrhagic complications. Also, easier bolus-only administration makes TNK a very practical rt-PA alternative. In several clinical trials, TNK has shown similar efficacy and safety to rt-PA, and the potential to be at least noninferior to rt-PA in some settings. TNK may be superior to rt-PA for reperfusing large vessel occlusions in patients with salvageable penumbra, although this has not yet translated to improved clinical outcomes. Further phase 3 studies are in progress comparing rt-PA with TNK for acute ischemic stroke during the first 4.5 hours. Studies are also in progress to evaluate the use of TNK for extended applications, such as wake-up stroke.

Single- and two- chain tissue type plasminogen activator treatments differentially influence cerebral recovery after stroke

Tissue type Plasminogen Activator (tPA), named alteplase (Actilyse®) under its commercial form, is currently the only pharmacological treatment approved during the acute phase of ischemic stroke, used either alone or combined with thrombectomy. Interestingly, the commercial recombinant tPA (rtPA) contains two physiological forms of rtPA: the single chain rtPA (sc-rtPA) and the two-chains rtPA (tc-rtPA), with differential properties demonstrated in vitro. Using a relevant mouse model of thromboembolic stroke, we have investigated the overall effects of these two forms of rtPA when infused early after stroke onset (i.e. 20 min) on recanalization, lesion volumes, alterations of the integrity of the blood brain barrier and functional recovery. Our data reveal that there is no difference in the capacity of sc-rtPA and tc-rtPA to promote fibrinolysis and reperfusion of the tissue. However, compared to sc-rtPA, tc-rtPA is less efficient to reduce lesion volumes and to improve functional recovery, and is associated with an increased opening of the blood brain barrier. These data indicate better understanding of differential effects of these tPA forms might be important to ultimately improve stroke treatment.

Tenecteplase Thrombolysis for Acute Ischemic Stroke

Tenecteplase is a fibrinolytic drug with higher fibrin specificity and longer half-life than the standard stroke thrombolytic, alteplase, permitting the convenience of single bolus administration. Tenecteplase, at 0.5 mg/kg, has regulatory approval to treat ST-segment-elevation myocardial infarction, for which it has equivalent 30-day mortality and fewer systemic hemorrhages. Investigated as a thrombolytic for ischemic stroke over the past 15 years, tenecteplase is currently being studied in several phase 3 trials. Based on a systematic literature search, we provide a qualitative synthesis of published stroke clinical trials of tenecteplase that (1) performed randomized comparisons with alteplase, (2) compared different doses of tenecteplase, or (3) provided unique quantitative meta-analyses. Four phase 2 and one phase 3 study performed randomized comparisons with alteplase. These and other phase 2 studies compared different tenecteplase doses and effects on early outcomes of recanalization, reperfusion, and substantial neurological improvement, as well as symptomatic intracranial hemorrhage and 3-month disability on the modified Rankin Scale. Although no single trial prospectively demonstrated superiority or noninferiority of tenecteplase on clinical outcome, meta-analyses of these trials (1585 patients randomized) point to tenecteplase superiority in recanalization of large vessel occlusions and noninferiority in disability-free 3-month outcome, without increases in symptomatic intracranial hemorrhage or mortality. Doses of 0.25 and 0.4 mg/kg have been tested, but no advantage of the higher dose has been suggested by the results. Current clinical practice guidelines for stroke include intravenous tenecteplase at either dose as a second-tier option, with the 0.25 mg/kg dose recommended for large vessel occlusions, based on a phase 2 trial that demonstrated superior recanalization and improved 3-month outcome relative to alteplase. Ongoing randomized phase 3 trials may better define the comparative risks and benefits of tenecteplase and alteplase for stroke thrombolysis and answer questions of tenecteplase efficacy in the >4.5-hour time window, in wake-up stroke, and in combination with endovascular thrombectomy.

Tenecteplase for Acute Ischemic Stroke: Current Evidence and Practical Considerations

Tenecteplase offers pharmacological advantages over alteplase, and growing evidence supports its consideration for the treatment of patients with acute ischemic stroke. Its ease of administration as a single bolus makes it a preferable agent for patients who need to be urgently transported to a comprehensive stroke center for endovascular therapy (drip and ship) and for patients first evaluated at comprehensive stroke centers who are eligible for endovascular intervention (combined intravenous and endovascular approach). Recent randomized controlled trials indicated that the efficacy of tenecteplase may be similar to that of alteplase in patients with mild strokes and that it is superior to alteplase for patients with more severe strokes from a large vessel occlusion. Cumulative evidence currently favors the use of the 0.25 mg/kg dose. While tenecteplase has not been approved by regulatory agencies in the USA or the EU for the treatment of acute ischemic stroke, ongoing trials and additional clinical experience from countries where it is already being used in practice will likely clarify the role of tenecteplase for the acute management of ischemic stroke in the near future.

3K3A-Activated Protein C Variant Does Not Interfere With the Plasma Clot Lysis Activity of Tenecteplase

BACKGROUND AND PURPOSE

A recombinant engineered variant of APC (activated protein C), 3K3A-APC, lacks anticoagulant properties (<10%) while preserving APCs anti-inflammatory, anti-apoptotic, and neuroprotective functions and is very promising in clinical trials for ischemic stroke. Therapeutic intervention with single bolus administration of the third-generation tPA (tissue-type plasminogen activator), tenecteplase, is anticipated to be widely adopted for treatment of acute ischemic stroke. 3K3A-APC is well-tolerated in stroke patients dosed with alteplase, and in vitro studies show 3K3A-APC does not interfere with alteplase-induced clot lysis. The purpose of this in vitro study was to assess the influence of 3K3A-APC on tenecteplase-induced clot lysis.

METHODS

Tenecteplase-mediated lysis of thrombin generated plasma clots of human normal pooled plasma was monitored in the presence of varying doses of 3K3A-APC. The effects on fibrinolysis by tenecteplase and alteplase were compared.

RESULTS

The presence of 3K3A-APC shortened the time for clot lysis induced by tenecteplase at very low levels but not at higher therapeutic concentrations of tenecteplase. Comparisons of alteplase-mediated clot lysis to tenecteplase clot lysis showed that both thrombolytic agents behaved similarly in the presence of 3K3A-APC.

CONCLUSIONS

These results indicate that 3K3A-APC does not interfere with tenecteplase's clot lysis function.

Design and production of new chimeric reteplase with enhanced fibrin affinity: a theoretical and experimental study

Plasminogen activators (PAs) are widely used for treatment of disorders caused by clot formation. Fibrin specific PAs are safe drugs from this group because of reducing the incidence of hemorrhage. The newer generation of PAs like tenecteplase, reteplase and desmoteplase were designed with the aim of achieving desirable properties such as improving specificity and affinity to fibrin and increasing half-life. Protein engineering and using of theoretical methods can help to rational and reliable design of new PAs with a set of favorable properties. In the present study, two new chimeric reteplase named M1-chr and M2-chr were designed with the aim of enhancing fibrin affinity also some potential properties include of increasing resistance to plasminogen activator inhibitor-1 and decreasing neurotoxicity. So, finger domain of desmoteplase was added to reteplase as a high fibrin specific domain. Some other point mutations were considering to achieve other mentioned properties. Three dimensional structure of wild-type reteplase and mutants were created by homology modeling and were evaluated by molecular dynamic simulation. Then, mutants docked to fibrin by HADDOCK web tools. Result of theoretical section verified the stability of mutants' structures. Also showed better interaction between M1-chr with fibrin than M2-chr. Wild-type and mutants were produced in bacterial expression system. Experimental assessment showed both mutants have appropriate enzymatic activity also 1.9-fold fibrin binding ability compared to wild-type. Therefore, this study offers new thrombolytic drugs with desirable properties specially enhanced fibrin affinity so they can represent a promising future in cost-effective production of favorable thrombolytic drugs.Communicated by Ramaswamy H. Sarma.

Blood Biomarkers for Stroke Diagnosis and Management

Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment and predict outcomes. Many blood biomarkers already guide decision-making in clinical practice. In stroke, the number of candidate biomarkers is constantly increasing. These biomarkers include proteins, ribonucleic acids, lipids or metabolites. Although biomarkers have the potential to improve the diagnosis and the management of patients with stroke, there is currently no marker that has demonstrated sufficient sensitivity, specificity, rapidity, precision, and cost-effectiveness to be used in the routine management of stroke, thus highlighting the need for additional work. A better standardization of clinical, laboratory and statistical procedures between centers is indispensable to optimize biomarker performance. This review focuses on blood biomarkers that have shown promise for translation into clinical practice and describes some newly reported markers that could add to routine stroke care. Avenues for the discovery of new stroke biomarkers and future research are discussed. The description of the biomarkers is organized according to their expected application in clinical practice: diagnosis, treatment decision, and outcome prediction.

Engineered microparticles and nanoparticles for fibrinolysis

Fibrinolytic agents including plasmin and plasminogen activators improve outcomes in acute ischemic stroke and thrombosis by recanalizing occluded vessels. In the decades since their introduction into clinical practice, several limitations of have been identified in terms of both efficacy and bleeding risk associated with these agents. Engineered nanoparticles and microparticles address some of these limitations by improving circulation time, reducing inhibition and degradation in circulation, accelerating recanalization, improving targeting to thrombotic occlusions, and reducing off-target effects; however, many particle-based approaches have only been used in preclinical studies to date. This review covers four advances in coupling fibrinolytic agents with engineered particles: (a) modifications of plasminogen activators with macromolecules, (b) encapsulation of plasminogen activators and plasmin in polymer and liposomal particles, (c) triggered release of encapsulated fibrinolytic agents and mechanical disruption of clots with ultrasound, and (d) enhancing targeting with magnetic particles and magnetic fields. Technical challenges for the translation of these approaches to the clinic are discussed.

Tenecteplase versus alteplase in acute ischemic stroke: systematic review and meta-analysis

Tenecteplase is a product of genetic modification of recombinant tissue plasminogen activator with superior pharmacodynamic and pharmacokinetic properties. This meta-analysis was to determine whether intravenous thrombolysis with tenecteplase in patients with acute ischemic stroke has better efficacy and safety outcomes than with intravenous alteplase. PubMed, Cochrane Central Register of Controlled Trials, WHO International clinical trials registry platform (ICTRP), Australian New Zealand Clinical Trials Registry (ANZCTR), EU Clinical Trials Register (EU-CTR) and ClinicalTrials.gov were searched for trials comparing tenecteplase with alteplase in acute ischemic stroke. Functional outcomes (modified Rankin Scale at 90 days), early major neurological improvement, rates of any intracerebral haemorrhage, symptomatic intracerebral haemorrhage and mortality rate at 90 days were the outcomes compared. Four randomized controlled trials involving 1334 patients were included. The Tenecteplase group compared to the alteplase group had significantly better early major neurological improvement (RR = 1.56, 95% CI [1.00, 2.43], p = 0.05). There was no significant difference between tenecteplase and alteplase in excellent functional outcome at 90 days, good functional outcome at 90 days, any intracerebral haemorrhage, symptomatic intracerebral haemorrhage or mortality at 90 days. Our meta-analysis found tenecteplase to be significantly favouring one outcome: early major neurological improvement. Other outcomes did not differ between the tenecteplase and alteplase groups. Trials of cost-effective/benefit analysis comparing tenecteplase versus alteplase and tenecteplase versus endovascular treatment are necessary to reinforce the evidence for the potential cost advantage of tenecteplase.

Structural Biology and Protein Engineering of Thrombolytics

Myocardial infarction and ischemic stroke are the most frequent causes of death or disability worldwide. Due to their ability to dissolve blood clots, the thrombolytics are frequently used for their treatment. Improving the effectiveness of thrombolytics for clinical uses is of great interest. The knowledge of the multiple roles of the endogenous thrombolytics and the fibrinolytic system grows continuously. The effects of thrombolytics on the alteration of the nervous system and the regulation of the cell migration offer promising novel uses for treating neurodegenerative disorders or targeting cancer metastasis. However, secondary activities of thrombolytics may lead to life-threatening side-effects such as intracranial bleeding and neurotoxicity. Here we provide a structural biology perspective on various thrombolytic enzymes and their key properties: (i) effectiveness of clot lysis, (ii) affinity and specificity towards fibrin, (iii) biological half-life, (iv) mechanisms of activation/inhibition, and (v) risks of side effects. This information needs to be carefully considered while establishing protein engineering strategies aiming at the development of novel thrombolytics. Current trends and perspectives are discussed, including the screening for novel enzymes and small molecules, the enhancement of fibrin specificity by protein engineering, the suppression of interactions with native receptors, liposomal encapsulation and targeted release, the application of adjuvants, and the development of improved production systems.