Corneal and scleral permeability of Desmoteplase in different species.

OBJECTIVE: Intraocular fibrin clots caused by severe uveitis can be a sight-threatening condition that needs to be resolved quickly and reliably. Intracameral injection of tissue-plasminogen activator (tPA) is commonly used to resolve intraocular fibrin. However, the drug does not reach fibrinolytic concentrations after topical application. Desmoteplase (DSPA) is a structurally similar but smaller fibrinolytic agent with a higher fibrin selectivity, a longer half-life, and better biocompatibility compared with tPA. This study was designed to evaluate the corneal and scleral permeability of DSPA in rabbits, pigs, dogs, horses, and humans ex vivo. PROCEDURES: Corneal and scleral tissues (n = 5 per group) were inserted into Franz-type diffusion chambers and exposed to 1.4 mg/mL DSPA for 30 minutes. Drug concentrations on the receiver side were determined by liquid chromatography-tandem mass spectrometry. RESULTS: Concentrations of DSPA after corneal and scleral permeation through fresh tissues ranged from 0.0 to 16.3 µg/mL and 0.0 to 11.4 µg/mL (rabbits), 0.3 to 5.6 µg/mL and 3.1 to 9.2 µg/mL (dogs), 2.1 to 14.9 µg/mL and 4 to 8.7 µg/mL (horses), and 0.6 to 3 µg/mL and 2.9 to 18.1 µg/mL (pigs), respectively. A concentration of 0.07-12.9 µg/mL DSPA was detectable after diffusion through tissue culture preserved human donor bank corneas (Table 1). CONCLUSIONS: Desmoteplase has the ability to permeate both cornea and sclera ex vivo in all species tested. Implications of the ex vivo permeability of DSPA suggest that in vivo permeability may be possible, and if so, it could lead to a novel topical application for lysing fibrin.

Safety and Tolerability of Desmoteplase Within 3 to 9 Hours After Symptoms Onset in Japanese Patients With Ischemic Stroke.

BACKGROUND AND PURPOSE: This study investigated the safety and tolerability of desmoteplase administered within 3 to 9 hours after stroke symptoms onset in Japanese patients with acute ischemic stroke. METHODS: Patients were randomized to treatment with either desmoteplase or placebo in a 2:1 ratio in 2 consecutive cohorts (70 µg/kg and then 90 µg/kg). Included patients had a baseline National Institutes of Health Stroke Scale score of 4 to 24 and occlusion or high-grade stenosis in the middle cerebral artery segment M1 or M2 on magnetic resonance angiography. The incidence of symptomatic intracranial hemorrhage (≤72 hours) was defined as the primary end point. The occurrence of asymptomatic ICH, symptomatic cerebral edemas, and adverse events were other safety outcomes of special interest. RESULTS: Symptomatic intracranial hemorrhage was observed within 72 hours in 2 patients treated with placebo and in 1 patient treated with 70 µg/kg desmoteplase. Any ICH (symptomatic or asymptomatic ICH) within 72 hours were observed in 7 (43.8%) patients treated with placebo, in 8 (50%) patients treated with 70 µg/kg desmoteplase, and in 9 (56.3%) patients treated with 90 µg/kg desmoteplase. Desmoteplase treatment with 70 or 90 µg/kg was not associated with an increased risk of symptomatic cerebral edema compared with placebo. There were no other serious safety concerns associated with desmoteplase. CONCLUSIONS: Desmoteplase in both 70 and 90 µg/kg doses had a favorable safety profile and was well tolerated in Japanese patients with acute ischemic stroke when administered 3 to 9 hours after stroke symptoms onset. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01104467.

[Intravenous thrombolysis in ischemic stroke: Therapeutic perspectives]. / Thrombolyse intraveineuse des infarctus cérébraux: perspectives thérapeutiques.

New therapeutic strategies are under evaluation to improve the treatment of acute ischemic stroke (AIS). Approaches combining intravenous (IV) thrombolysis with recombinant tissue plasminogen activator (rt-PA) and antithrombotic agents are currently evaluated. The combination of IV rt-PA and aspirin showed a high rate of intracranial hemorrhage whereas the association of rt-PA and eptifibatide seems more promising. The results of recent studies evaluating the administration of eptifibatide or argatroban in conjunction with conventional IV thrombolysis with rt-PA are expected to clarify the safety and efficacy of these treatments. More fibrin-specific plasminogen activators, tenecteplase and desmoteplase, are also investigated. These fibrinolytic agents showed a favorable safety profile but their efficacy in AIS remains uncertain. While phase III studies, DIAS-3 and DIAS-4, evaluating IV desmoteplase up to nine hours after stroke onset did not meet the primary endpoint, the results of studies comparing IV tenecteplase and IV rt-PA are expected.

Identification, characterization, and engineering of glycosylation in thrombolytics.

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.

Fibrinolytic Capacity of Desmoteplase Compared to Tissue Plasminogen Activator in Rabbit Eyes.

PURPOSE: Desmoteplase (DSPA) was evaluated and compared with tissue plasminogen activator (t-PA) for its intraocular fibrinolytic effect and short-term toxicity in an in vivo study using rabbit eyes. METHODS: Fibrin clots were induced in the anterior chamber of 44 rabbit eyes, and drug efficacy was measured by clot size reduction over 24 h. Topical DSPA eye drops (1.4 and 2 mg/mL) were compared with vehicle solution in a multiple-drop regimen in 8 animals per group. Intracameral injections of 0.6 µg DSPA (n = 14) and 25 µg t-PA (n = 14) were evaluated for their fibrinolytic efficacy. Animals were euthanized 24 h after drug application. RESULTS: No significant differences were seen between topically treated DSPA and vehicle-treated animals. Intracameral t-PA had a higher fibrinolytic efficacy than DSPA at early time points, but no significant difference was seen between both groups at 24-h postapplication. Animals with t-PA treatment demonstrated significantly more side effects compared with DSPA-treated animals. DSPA showed no-to-mild side effects after topical and intracameral treatment. Histologically, no toxic effects were observed in any globe. CONCLUSIONS: DSPA is a promising drug with fewer side effects and similar fibrinolytic efficacy compared with t-PA 24 h after intracameral application in rabbit eyes at the tested concentration. Drug efficacy might be improved by increasing intracameral DSPA doses.

Thrombolytic Therapy for Acute Ischemic Stroke: Past and Future.

BACKGROUND: Thromboembolic ischemic stroke, which is mainly caused by hypertension, as well as plasma dyslipidemia, arterial fibrillation and diabetes, is a leading cause of death in the US and other countries. Numerous clinical trials for thrombolytic drugs, which aimed to pharmacologically dissolve thrombi, were conducted in the 1950s, when the first thrombolytic therapy was performed. METHODS: In this study, we summarize the pathophysiologic features of ischemic stroke, and the history of thrombolytic therapy, and discuss the recent progress that has been made in the ongoing development of thrombolytic drugs. CONCLUSION: Thrombolytic therapy is sometimes accompanied by harmful hemorrhagic insults; accordingly, a window of time wherein therapy can safely be performed has been established for this approach. Several basic and clinical studies are ongoing to develop next-generation thrombolytic drugs to expand the time window.

[Thrombolytic therapy of ischemic stroke]. / Tromboliticheskaia terapiia ishemicheskogo insul'ta.

Reperfusion therapy is one of the main treatment strategies of ischemic stroke. The first studies of the efficacy of thrombolytic medications started form the use of streptokinase and fibrinolysin in patients with ischemic stroke in late 50 - early 60 of the XX century in the United States, Soviet Union, and Western Europe. After the development of recombinant tissue plasminogen activator, thrombolysis became one of the main methods of reperfusion in patients with acute ischemic stroke, acute myocardial infarction, or other acute vascular thrombotic events. Later, modified variants of tissue plasminogen activator with prolonged clearance time, high fibrin-selectivity, and bolus delivery were introduced. Another group of thrombolytic agents includes derivatives of flora and fauna - external plasminogen activators, of which streptokinase, staphylokinase, and desmoteplase are most common drugs. These medications are not a structural part of the human organism, and overcoming of immunogenicity while preserving fibrinolytic activity and fibrin specificity is one of the main tasks in applying them in clinical practice.

Desmoteplase for Acute Ischemic Stroke: A Systematic Review and Metaanalysis of Randomized Controlled Trials.

INTRODUCTION: There is an unmet need to develop better treatments for acute ischemic stroke (AIS). Desmoteplase is a vampire bat saliva-derived analogue of human tissue plasminogen activator. It has higher fibrin selectivity and a longer half-life, compared to alteplase. We performed this metaanalysis to investigate the safety and efficacy of desmoteplase in AIS. METHOD: A computer literature search (PubMed, EMBASE, CENTRAL, Scopus, Web of science, and clinicaltrials.gov) was carried out. Data were extracted from eligible records and analyzed using RevMan software (version 5.3 for windows). Safety and efficacy endpoints were pooled as odds ratios (ORs) for the two groups. RESULT: Five randomized trials (n=821 patients) were pooled in the final analysis. The overall effect size favored desmoteplase over placebo in terms of reperfusion 4 to 24 hours posttreatment (OR 1.49, 95% CI [1.02, 2.19]). However, the pooled effect size did not favor either of the two groups in terms of good clinical outcome at 90 days (OR 1.16, 95% CI [0.86, 1.55]). Neither of the primary safety outcomes differed significantly between the two groups (symptomatic intracranial hemorrhage: OR 1.29, 95% CI [0.53, 3.16] and mortality within 90 days: OR 1.20, 95% CI [0.73, 1.97]). CONCLUSION: Current evidence suggests a favorable reperfusion effect for desmoteplase within 3 to 9 hours after AIS. Further large randomized trials, using a moderate dose between 90 µg/kg and 125 µg/kg, are required to translate this successful reperfusion into better clinical and quality of life outcomes for AIS patients.

In Vitro Examination of the Thrombolytic Efficacy of Desmoteplase and Therapeutic Ultrasound Compared with rt-PA.

The aim of the study described here was to evaluate the thrombolytic efficacy of combined treatment with the fibrin-selective plasminogen activator desmoteplase (DSPA) and therapeutic ultrasound (sonothrombolysis [STL]) compared with conventional rt-PA (recombinant tissue plasminogen activator) treatment in vitro. Lysis rates were determined by the weight loss of platelet-rich plasma (PRP) clots treated with rt-PA (60 kU/mL) or DSPA (2 µg/mL) combined with pulsed wave ultrasound (2 MHz, 0.179 W/cm(2)). To reveal the individual effects of medication and ultrasound, lysis rates were also determined for DSPA monotherapy and for combined treatment with rt-PA and ultrasound. Clots solely placed in plasma served as the control group. Lysis increased significantly with rt-PA (26.5 ± 7.8%) and DSPA (30.5 ± 6%) compared with the control group (18.2 ± 5.9%) (each p < 0.001). DSPA lysis was more effective than rt-PA lysis (without STL: p = 0.015, with STL: p = 0.01). Combined treatment with DSPA and 2-MHz STL significantly exceeded rt-PA lysis (32.8% vs. 26.5%, p < 0.001).

Desmoteplase as a potential treatment for cerebral ischaemia.

INTRODUCTION: Desmoteplase is an investigational plasminogen activator found in the saliva of the vampire bat, Desmodus rotundus. It has been of scientific interest for over 25 years as it exhibits pharmacological properties that have led to the hypothesis that desmoteplase may be safer and more effective than recombinant tissue plasminogen activator (rtPA) in arterial thromboembolic disease, and in particular, acute ischaemic stroke (AIS). AREAS COVERED: In this review, the authors cover the pharmacological properties of desmoteplase, focussing on how this translates into a theoretical advantage over rtPA in AIS. The authors further present preclinical studies and clinical data on the use of desmoteplase in AIS. EXPERT OPINION: In contrast to rtPA, and despite a similar structure, desmoteplase has demonstrated high selectivity for fibrin and an absence of neurotoxicity in experimental models. Demonstrating such properties in animal models, one would have expected an ambitious clinical study future. Phase II and Phase III clinical studies in patients with AIS demonstrated an excellent safety profile with low risk of symptomatic intracranial haemorrhage compared to rtPA. However, data on clinical and radiological efficacy end points of desmoteplase in AIS are inconclusive. Further Phase III trials are currently underway and their results are eagerly awaited.

t-PA, but not desmoteplase, induces plasmin-dependent opening of a blood-brain barrier model under normoxic and ischaemic conditions.

Tissue-type plasminogen activator (t-PA) is the only thrombolytic treatment available for patients with acute ischaemic stroke. However, t-PA can increase permeability of the blood-brain barrier (BBB). Desmoteplase is a plasminogen activator derived from the common vampire bat, currently under clinical development for ischaemic stroke. We compared how t-PA and desmoteplase influenced BBB permeability using a human in vitro model where primary brain endothelial cells (BEC) and astrocytes are co-cultured on the opposite sides of a porous membrane. Permeability changes were evaluated 6 or 24h post-stimulation by passage of fluorescent albumin across the membrane. Under normoxic conditions, t-PA, but not desmoteplase, increased BBB permeability. Surprisingly, the ability of t-PA to affect the barrier was lost under conditions of oxygen-glucose deprivation (OGD). Addition of plasminogen re-sensitised the BBB to the action of t-PA under both normoxia and OGD, but did not affect the inert behaviour of desmoteplase, even when digested fibrinogen was added to ensure optimal plasmin generation. These observations coincided with plasmin-dependent changes in astrocyte and BEC morphology and disruption of tight junction proteins in BECs, specifically initiated by t-PA but not by desmoteplase. Finally, inhibition of plasmin post-stimulation with t-PA and plasminogen, especially within 2h, protected the BBB against t-PA-mediated barrier opening. Hence t-PA, but not desmoteplase, increases BBB permeability under both normoxic and OGD conditions in a reversible, plasmin-dependent process. The inability of desmoteplase to increase permeability despite its capacity to generate plasmin provides further support for its use as thrombolytic in patients with ischaemic stroke.

The biotechnological potential of fibrinolytic enzymes in the dissolution of endogenous blood thrombi.

Formation of endogenous thrombi in blood vessels is one of the leading causes of death in our modern life. According to data provided by the World Health Organization (WHO) in 2000, heart diseases are responsible for 29% of the total mortality rate in the world. For this, a tremendous amount of research has been done in the area of prevention and treatment of these diseases. The classical therapy of these thrombi relies upon the use of antiplatelets, anticoagulants, or even surgeries. Relatively recently, the fibrinolytic enzymes produced by microorganisms, snakes, earthworms, insects, plants, and other organisms are being successfully used in the treatment of blood clots, especially with regard to the direct dissolving action on fibrin in tandem with less cost and side effects in comparison with the first-generation thrombolytic agents, streptokinase and urokinase. Furthermore, recombinant DNA technology has succeeded in improving and decreasing the undesirable effects of the first generation of enzymes. Recombinant PAs or rt-PAs like alteplase, retelase, saruplase, tenecteplase, lanoteplase, and desmoteplase became available in the drug markets with advantages of less binding loci with PAI-1 to avoid degradation while providing faster and more complete reperfusion in a greater number of patients with less risk of bleeding and intracranial hemorrhage. This review is the first to cover all the natural and recombinant thrombolytic agents used in enzyme therapy.