Use of ancrod in acute or progressing ischemic cerebral infarction

Revisiting promising preclinical intracerebral hemorrhage studies to highlight repurposable drugs for translation

Intracerebral hemorrhage is a devastating global health burden with limited treatment options and is responsible for 49% of 6.5 million annual stroke-related deaths comparable to ischemic stroke. Despite the impact of intracerebral hemorrhage, there are currently no effective treatments and so weaknesses in the translational pipeline must be addressed. There have been many preclinical studies in intracerebral hemorrhage models with positive outcomes for potential therapies in vivo, but beyond advancing the understanding of intracerebral hemorrhage pathology, there has been no translation toward successful clinical application. Multidisciplinary preclinical research, use of multiple models, and validation in human tissue are essential for effective translation. Repurposing of therapeutics for intracerebral hemorrhage may be the most promising strategy to help relieve the global health burden of intracerebral hemorrhage. Here, we have reviewed the existing literature to highlight repurposable drugs with successful outcomes in preclinical models of intracerebral hemorrhage that have realistic potential for development into the clinic for intracerebral hemorrhage.

Defibrinogen Therapy for Acute Ischemic Stroke: 1332 Consecutive Cases

This study aimed to examine the effectiveness of defibrinogen therapy on functional recovery and safety among 1332 consecutive ischemic stroke patients who had not received intravenous thrombolysis with recombinant tissue plasminogen activator. Stroke patients undergoing conservative and relatively individualized multiple-day dosing regimens of defibrinogen therapy between January 1, 2008 and May 30, 2016 were enrolled. Data were analyzed according to functional success (Barthel Index of 95 or 100, mRS of 0 or 1) and safety variables (intracranial hemorrhage, mortality and stroke recurrence). At 12 months, 18.62% (203/1087) of patients were lost to follow-up. The functional success rates were 39.84% (526/1320) and 42.23% (459/1087) as assessed by BI at 3 months and 12 months, respectively. Fifteen patients had asymptomatic intracranial hemorrhage within 24 hours after the initial defibrase administration. During the 14 days after hospitalization, 12 patients were diagnosed with symptomatic intracranial hemorrhage (sICH) and a total of 12 patients died from all causes. At 3 months, 56 patients were dead and 21 patients had recurrent stroke. The percentage of death and recurrence of stroke at 12 months were 6.81% and 3.22%, respectively. Results from the historical control showed no significant differences of functional success were detected between the patients treated with rt-PA within 6 hours of stroke onset in NINDS II and the patients treated with defibrase within 6 hours after stroke in the present study. The multiple-day dosing regimen of defibrinogen therapy using defibrase applied in the present study could achieve functional improvement among acute ischemic stroke patients, with low risks of mortality when compared with other similar studies. However, the efficacy and safety of such a defibrinogenating therapy is needed to be verified by RCTs with large sample size.

[Intravenous thrombolysis in ischemic stroke: Therapeutic perspectives]

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.

Neurological effects of venomous bites and stings: snakes, spiders, and scorpions

Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake bite envenoming may result in stroke or muscle paralysis. Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Latrodectism is related to neurotoxins present in the venom of widow spiders. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. It may present with a stroke due to a severe coagulopathy. The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduce the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.

Neurological complications of venomous snake bites: a review

Snake bite envenoming is a neglected tropical disease affecting millions of people living in the developing world. According to the offending snake species, the clinical picture may be dominated by swelling and soft tissue necrosis in the bitten limb, or by systemic or neurological manifestations. Serious neurological complications, including stroke and muscle paralysis, are related to the toxic effects of the venom, which contains a complex mixture of toxins affecting the coagulation cascade, the neuromuscular transmission, or both. Metalloproteinases, serine proteases, and C-type lentins (common in viper and colubrid venoms) have anticoagulant or procoagulant activity and may be either agonists or antagonists of platelet aggregation; as a result, ischemic or hemorrhagic strokes may occur. In contrast, the venom of elapids is rich in phospholipase A(2) and three-finger proteins, which are potent neurotoxins affecting the neuromuscular transmission at either presynaptic or post-synaptic levels. Presynaptic-acting neurotoxins (called β-neurotoxins) inhibit the release of acetylcholine, while post-synaptic-acting neurotoxins (called α-neurotoxins) cause a reversible blockage of acetylcholine receptors. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduces the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.

Fibrinogen depleting agents for acute ischaemic stroke

BACKGROUND

Fibrinogen depleting agents reduce fibrinogen in blood plasma, reduce blood viscosity and hence increase blood flow. This may help remove the blood clot blocking the artery and re-establish blood flow to the affected area of the brain after an ischaemic stroke. The risk of haemorrhage may be less than with thrombolytic agents. This is an update of a Cochrane review first published in 1997 and last updated in 2003.

OBJECTIVES

To assess the effect of fibrinogen depleting agents in patients with acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (July 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 7), the Chinese Stroke Trials Register (September 2011), MEDLINE (1950 to July 2011), EMBASE (1980 to July 2011) and Web of Science Conference Proceedings (1990 to July 2011). In addition, we searched six Chinese databases, four ongoing trials registers (July 2011) and relevant reference lists. For previous versions of the review, we handsearched journals and contacted researchers in China and Japan and relevant drug companies.

SELECTION CRITERIA

Randomised trials of fibrinogen depleting agents started within 14 days of stroke onset, compared with control in patients with definite or possible ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted the data. We resolved disagreement by discussion.

MAIN RESULTS

We included eight trials involving 5701 patients. Six trials tested ancrod and two trials tested defibrase (patients were treated for less than three hours to less than 48 hours). Allocation concealment was adequate in seven trials. Fibrinogen depleting agents marginally reduced the proportion of patients who were dead or disabled at the end of follow-up (risk ratio (RR) 0.95, 95% confidence Interval (CI) 0.90 to 0.99, 2P = 0.02). There was no statistically significant difference in death from all causes during the scheduled treatment or follow-up period. There were fewer stroke recurrences in the treatment group than in the control group (RR 0.67, 95% CI 0.49 to 0.92, 2P = 0.01). However, symptomatic intracranial haemorrhage was about twice as common in the treatment group compared with the control group (RR 2.42, 95% CI 1.65 to 3.56, 2P < 0.00001).

AUTHORS' CONCLUSIONS

The current evidence is promising but not yet sufficiently robust to support the routine use of fibrinogen depleting agents for the treatment of acute ischaemic stroke. Further trials are needed to determine whether there is worthwhile benefit, and if so, which categories of patients are most likely to benefit.

Ancrod for acute ischemic stroke: a new dosing regimen derived from analysis of prior ancrod stroke studies

BACKGROUND

Ancrod, a fibrinogen-reducing agent, has been evaluated as treatment beginning within 3 or 6 hours of onset of acute ischemic stroke with inconsistent results. The data sets from these studies provide an opportunity to determine whether ancrod-related variables are associated with efficacy and safety.

OBJECTIVE

This post hoc analysis of data from the Stroke Treatment with Ancrod Trial (STAT) analyzed ancrod-related variables as potential determinants of efficacy or safety. The resulting hypotheses were then tested in the European STAT (ESTAT) database.

METHODS

The relationships between ancrod-related variables and the outcomes of efficacy and symptomatic intracranial hemorrhage (ICH) were analyzed using a 3-stage multivariate process.

RESULTS

Good clinical outcome at 3 months based on the Barthel Index occurred almost twice as often in rapid defibrinogenators (>or=30 mg/dL/h) (52%) as in slow defibrinogenators (26%), with no increase in mortality or symptomatic ICH. Compared with a 20.7% incidence of symptomatic ICH in patients with mean post-9-hour fibrinogen levels less than or equal to 60 mg/dL, symptomatic ICH incidence was 0.8% in those with mean levels greater than 60 mg/dL (with no loss of efficacy). There were no symptomatic ICHs among 220 North American patients with mean levels greater than 70 mg/dL. It was hypothesized that an initial controlled rapid ancrod infusion with mean post-9-hour fibrinogen levels greater than 70 mg/dL would yield superior efficacy and safety. Such ESTAT patients had statistically significant efficacy versus placebo and a marked reduction in the incidence of symptomatic ICH versus patients taking ancrod with lower maintenance fibrinogen levels.

CONCLUSION

Modifications to ancrod dosing may substantially improve efficacy while reducing the rate of symptomatic ICH.

Emerging therapies for acute ischemic stroke

Stroke is a major public health problem in the United States and the development of novel therapeutic strategies is an important research priority. Advances in this field are proceeding on several fronts, including the use of next-generation plasminogen activators and glycoprotein IIb/ IIIa inhibitors, refined patient selection with advanced magnetic resonance imaging sequences, endovascular approaches to thrombolysis and thrombectomy, and adjuvant use of ultrasound. There remains no proven therapy for intracerebral hemorrhage, but early results with recombinant activated factor VII look very promising. It is hoped that in the near future, physicians managing patients with acute neurological events will have a robust armamentarium of therapies to bring to bear on both ischemic and hemorrhagic vascular disease.

Intravenous ancrod for acute ischaemic stroke in the European Stroke Treatment with Ancrod Trial: a randomised controlled trial

BACKGROUND

Intravenous tissue plasminogen activator is the only approved specific treatment for acute ischaemic stroke. Ancrod, a natural defibrinogenating agent from snake venom, has proved to have a favourable effect when given within 3 h after an acute ischaemic stroke. The European Stroke Treatment with Ancrod Trial was undertaken to assess the effects of ancrod when given within 6 h.

METHODS

1222 patients with an acute ischaemic stroke were included in this randomised double-blind placebo-controlled trial. Brain CT scans were done to exclude intracranial haemorrhages and large evolving ischaemic infarctions. Patients were randomly assigned ancrod (n=604) or placebo (n=618). The primary outcome was functional success at 3 months (survival, Barthel Index of 95 or 100, or return to prestroke level). The analysis was by intention-to-treat. This trial is registered with ClinicalTrials.gov, trial number NCT00343174.

FINDINGS

Functional success at 3 months did not differ between patients given ancrod (42%) and those given placebo (42%) (p=0.94, OR=0.99, 95% CI, 0.76-1.29).

INTERPRETATION

On the basis of our findings, ancrod should not be recommended for use in acute ischaemic stroke beyond 3 h.

Advances in thrombolytics and mechanical devices for treatment of acute ischemic stroke

Stroke is a leading cause of death and disability. Recently, there have been advances in the treatment of acute ischemic stroke aimed at re-establishing blood flow to the affected area in an effort to save the ischemic penumbra surrounding the area of infarction. This is achieved by the use of thrombolytics intravenously or intra-arterially. The use of mechanical devices facilitates the function of pharmacological agents used in addition to minimizing the associated risks. In this review, we first discuss the therapeutic potentials and strategies employed in using different thrombolytics in management of acute ischemic stroke. Subsequently, we discuss the recent advances and therapeutic applications of mechanical devices in this field.

Fibrinogen depleting agents for acute ischaemic stroke

BACKGROUND

Fibrinogen depleting agents reduce fibrinogen in blood plasma, reduce blood viscosity and hence increase blood flow. This may help remove the blood clot blocking the artery and re-establish blood flow to the affected area of the brain after an ischaemic stroke. The risk of haemorrhage may be less than with thrombolytic agents.

OBJECTIVES

The objective of this review was to assess the effect of fibrinogen depleting agents in patients with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched May 2003). In addition we searched the following electronic databases: EMBASE (1980-October 2001), China Biological Medicine Database (CBM-disc 1981- December 2002), Chinese Stroke Trials Register (1996 - December 2002) and Index of Scientific and Technical Proceedings (Web of Science Proceedings [1990-October 2001]). We handsearched relevant journals and contacted Chinese and Japanese researchers and drug companies.

SELECTION CRITERIA

Randomised and quasi-randomised trials of fibrinogen depleting agents started within 14 days of stroke onset, compared with control in patients with definite or possible ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the inclusion criteria, assessed trial quality and extracted the data.

MAIN RESULTS

Five trials involving 2926 patients were included. A further trial (ESTAT) has not yet been published in full. Four trials tested ancrod and one trial tested defibrase. Allocation concealment was adequate in four trials. Fibrinogen depleting agents moderately reduced the proportion of patients who were dead or disabled at the end of follow up (Relative risk [RR] 0.90, 95% Confidence Interval [CI] 0.82 to 0.98, 2P=0.02). There was no statistically significant difference in death from all causes during the scheduled treatment period (RR 0.71, 95% CI 0.44 to 1.13) and at the end of follow-up (RR 0.98, 95% CI 0.78 to 1.24). There was a non-significant excess of symptomatic intracranial haemorrhages with treatment (RR 2.64, 95%CI 0.96 to 7.30, 2P=0.06).

REVIEWER'S CONCLUSIONS

Fibrinogen depleting agents are promising. However more data, particularly ESTAT data, are needed before more reliable conclusions can be drawn.

Stroke trials: what have we learned?

We reviewed the recent, major, therapeutic trials of intravenous thrombolytic therapy and ancrod for ischemic stroke. Randomized, controlled studies of acute ischemic stroke treatment were reviewed. Several post-FDA approval intravenous tPA studies were reviewed to understand the experience of this medication in practice. STAT trial was the major study using ancrod. Of multiple intravenous thrombolytic studies, the NINDS study of intravenous tPA was the only study to demonstrate a significantly higher percentage of patients with complete recovery or minimal deficit at three months. Studies in communities utilizing intravenous tPA for stroke illustrate the need for close adherence to the NINDS study protocol or else the risk of tPA use may exceed the benefits.

Management of acute stroke

Acute stroke is a medical emergency. The outcome is influenced by the rapidity and quality of initial care, which is best delivered by specialists with appropriate facilities, including 24 h access to computed tomography. Stroke management requires attention to simple details and has been summarised in clinical guidelines. General measures include control of blood glucose concentration, temperature, fluid balance, and oxygenation. Blood-pressure management is a matter for continuing research. Aspirin should be started early in ischaemic stroke, but heparin has doubtful value; antiembolism stockings may be preferable. Thrombolysis has a substantial benefit in selected circumstances, and trials continue to examine a wider role. Neuroprotection remains experimental, though magnesium is potentially of interest. Early neurosurgery has a role limited to decompression of lesions in the posterior fossa but is under trial for large hemispheric infarcts and moderate intracerebral bleeds.

Stroke--acute interventions

The reduction of blood flow to parts of the brain is the cause of ischemic stroke leading to functional deficits and, if prolonged, to irreversible neurological and morphological defects. The fast reperfusion, therefore is the most important therapeutic strategy and was proven to be effective in clinical trials. Steps to intervene with secondary biochemical, molecular, or inflammatory disturbances were not successful so far. Since direct therapeutic interventions are limited, the general management of the stroke victim is of utmost importance--and was shown to be most successful in dedicated stroke units. Acute therapeutic interventions in ischemic stroke can only be successful as long as tissue in the area of the ischemic compromise is still viable. The area of irreversible damage can be identified and distinguished from the penumbral zone, i.e., tissue with impaired function but preserved morphology by functional imaging modalities, like positron emission tomography (PET) or perfusion-(PW) and diffusion-weighted (DW) magnetic resonance imaging (MRI). In such studies it was demonstrated that a large portion of the final infarct is irreversibly affected in the first few hours in many patients. A considerable tissue volume is viable but critically hypoperfused; a smaller portion of the final infarct is sufficiently perfused and in this area secondary and delayed biochemical and molecular mechanisms contribute to the damage. Based on this concept the improvement of perfusion within the time window of opportunity must be the primary goal in treatment of ischemic stroke, and neuroprotective and other strategies can only play a supportive and additive role. That this is the case can be seen from the results of many controlled therapeutic trials, in which up to now only thrombolytic therapy with a 3 h time window for systemic and a 6 h time window for intraarterial application proved its efficacy, whereas all trials with neuroprotective, anti-inflammatory or anti-apoptotic strategies failed. Since the direct treatment strategies are limited the acute management of stroke victims is of utmost importance: This can be achieved optimally in dedicated stroke units in which the outcome was significantly improved over the regular care. It is still to be investigated if invasive strategies--e.g., craniectomy and hypothermia--or the combination of reperfusion and neuroprotective therapy can improve the outcome after ischemic stroke.

A systematic review of randomized evidence for fibrinogen-depleting agents in acute ischemic stroke

OBJECTIVE

To assess the efficacy and safety of fibrinogen-depleting agents (snake venom extracts) in the treatment of acute ischemic stroke.

METHODS

A systematic review of all the relevant randomized controlled trials (RCTs) was performed. RCTs were identified from the Cochrane Stroke Group's Specialized Trial Register, additional electronic and hand searching, and personal contact with pharmaceutical companies. We included all completed and unconfounded truly or quasi-randomized trials in patients with ischemic stroke comparing fibrinogen depleting agents with control started within 14 days of the stroke onset. The Peto method was used for analysis.

RESULTS

Eight completed and two ongoing RCTs have been identified so far. Only three trials using ancrod (182 patients) met the inclusion criteria. Ancrod was associated with a significant reduction in early deaths (5.6% v 16%; odds ratio [OR], 0.33; 95% confidence interval [CI], 0.13 to 0.85; 2P=.02) suggesting that treatment of 100 patients would avoid about 10 early deaths. The frequency of asymptomatic intracranial hemorrhage shown by computed tomography was similar between ancrod-treated and control groups (7.6% v 9.6%; OR, 0.78; 95% CI, 0.26 to 2.33; 2P=.65). No major intracranial or extracranial hemorrhages or recurrent ischemic strokes occurred in the ancrod-allocated patients. There were nonsignificant trends in favor of ancrod in death from any cause (OR, 0.57; 95% CI, 0.27 to 1.23; 2P=.15) and death or disability (OR, 0.52; 95% CI, 0.26 to 1.03; 2P=.06) at the end of trial follow-up.

CONCLUSIONS

There were too few patients and outcome events to draw reliable conclusions from the present data. Although ancrod-like agents appeared promising, their routine use cannot be recommended at the moment. Two ongoing trials (including about 1,000 patients in total) will provide more data. Future trials should test simpler fixed-dose regimens to allow better generalizability.

Ancrod in the treatment of acute ischaemic stroke

Ancrod converts fibrinogen into soluble fibrin products, resulting in a decrease in plasma fibrinogen and blood viscosity, and also induces the release of endogenous tissue-type plasminogen activator from the vessel wall. These activities suggest that treating patients with acute ischaemic stroke with ancrod might result in improved cerebral blood flow and patient outcome. Two large randomised placebo-controlled studies have evaluated treatment with ancrod in patients with acute ischaemic stroke. In the first, patients were treated within 6 hours of symptom onset: this was not successful in quickly lowering fibrinogen levels to the target range (0.7 to 1.0 g/L) and the results were inconclusive. However, a post hoc analysis suggested that treatment with ancrod was effective in patients whose fibrinogen level was reduced to less than 1.3 g/L within 6 hours of starting treatment. A second larger study is still in progress, but preliminary results in patients treated within 3 hours of onset of ischaemic stroke are available and indicate that the target fibrinogen level of less than 1 g/L within 6 hours of instituting treatment is being achieved in most patients.

Thrombolytic therapy for cerebral infarction

Until recently, no clinically effective therapy for acute ischemic stroke has been available. Recent advances in the use of thrombolytic therapy for ischemic stroke appear promising in clinical care. As the use of thrombolytic therapy in acute stroke progress, emergency physicians (EPs) will become increasingly involved in its implementation. The EP must be cognizant of both prior and ongoing investigations in acute ischemic stroke therapy. To that end, this article reviews research in the field of thrombolytic therapy for acute ischemic stroke.

Ancrod for the treatment of acute ischemic brain infarction. The Ancrod Stroke Study Investigators

BACKGROUND AND PURPOSE

There is no acute therapy proven to be of benefit for ischemic stroke. Ancrod is a potentially effective therapy because of the advantageous consequences of fibrinogen lowering.

METHODS

We studied the safety and efficacy of ancrod in patients with acute ischemic stroke administered within 6 hours of stroke onset. In a double-blind, randomized, placebo-controlled trial 64 patients received intravenous ancrod and 68 received placebo for 7 days. Neurological outcome, disability, and brain infarct volume were measured.

RESULTS

There was no significant difference in overall mean scores on the Scandinavian Stroke Scale. No increase in bleeding occurred in the ancrod-treated patients. The target reduction of plasma fibrinogen levels of less than 100 mg/dL was achieved in only 15 (23%) of 64 ancrod-treated patients. Those patients with ancrod-induced 6-hour fibrinogen levels 130 mg/dL or less had a marginally significantly better neurological outcome on the Scandinavian Stroke Scale, mortality, and Barthel Index than ancrod-treated patients with higher fibrinogen levels.

CONCLUSIONS

Ancrod appears safe and potentially effective when administered to patients within 6 hours of onset of ischemic stroke.

Ancrod causes rapid thrombolysis in patients with acute stroke

Clot lysis is desirable in patients with thrombi in arteries and arterioles by a safe rapidly-acting thrombolytic agent. Ancrod cleaves fibrinogen; the resulting circulating ancrod-fibrin stimulates fibrinolysis. Ancrod action and effect were studied in 20 patients with acute developing stroke in a double-blind, placebo-controlled study. Patients were randomly assigned to one of two treatment groups, and received either normal saline or ancrod 0.5 mu/kg in normal saline administered as a constant-rate intravenous infusion over 6 hours. Subsequent doses of ancrod (or saline placebo) were determined daily thereafter for a total treatment period of 7 days. Neither bleeding nor re-thrombosis occurred within the 90 day follow-up period. That ancrod acted rapidly was shown by a significant decrease in functional plasminogen activator inhibitor (PA-I) within 60 minutes, and by significant elevations of fibrin(ogen) degradation products (FDP) and D-dimer within 3 and 4 hours. The biological effect of fibrinolysis in ancrod infused patients was demonstrated by a greater improvement in stroke score when compared to those infused with saline.