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• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides
  • A61K38/16—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • A61K38/43—Enzymes; Proenzymes; Derivatives thereof
  • A61K38/46—Hydrolases (3)
  • A61K38/48—Hydrolases (3) acting on peptide bonds (3.4)
  • A61K38/482—Serine endopeptidases (3.4.21)
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/10—Drugs for disorders of the cardiovascular system for treating ischaemic or atherosclerotic diseases, e.g. antianginal drugs, coronary vasodilators, drugs for myocardial infarction, retinopathy, cerebrovascula insufficiency, renal arteriosclerosis

Definitions

• the present invention relates to a method for the treatment of stroke by the administration of a single dose of a defibrinogenating agent followed by normalization of fibrinogen levels without the further administration of a defibrinogenating agent. More particularly, the invention relates to a method for minimizing neurological damage associated with stroke and reducing the likelihood and occurrence of serious side effects associated with stroke, such as symptomatic intracranial hemorrhage and death.
• Stroke is a type of cardiovascular disease that affects the arteries leading to and within the brain.
• Ischemic stroke is the third leading cause of death and the leading cause of disability in the U.S.
• Acute ischemic stroke is due to angiographically visible embolic or thrombotic occlusion in 70% to 80% of cases. Following occlusion, there; is a time- dependent cascade of pathological events characterized by decreased energy production, over-stimulation of neuronal glutamate receptors, intraneuronal accumulatiozti of sodium, chloride and calcium ions, mitochondrial injury, and finally cell death.
• Criti al ischemia produces a core of dead brain tissue surrounded by hypoxic but potentially salvageable tissue.
• the aim of treatment is to prevent or slow the cascade of events, and to restore normal blood flow as soon as possible. There are several treatment options, depending on the circumstances.
• Intravenous ancrod for treatment of acute ischemic stroke has beea reported (Sherman et al.; JAMA 283(18):2395-2403.
• Ancrod (known commercially b>y the trade names, ARWIN ® ARVIN ® , and VIPRINEX ® ), a highly glycosylated serine protease having an average molecular weight of about 38,000 Dalton and a carbohydrate content of about 38%, is a fibrinogen-splitting enzyme obtained from the venom of the Malayan pit viper (Calloselasma rhodostoma, previously known as Agkistrodon rhodostoma or Ancistrodon rhodostoma) and which has anticoagulant properties and the ability to dissolve blood clots (J.
• the ⁇ -(B) chain of the fibrinogen molecule is not attacked by ancrod and is thus not liberated.
• the fragments (de- "A” -fibrin monomers) produced after the elimination of the fibrinopeptides by ancrod are eventually able to polymerize to thin filaments (FIGURE 1).
• Lacking an effect on factor XIII (with cross-linking activity), on other coagulation 1 1 ⁇ factors, and on platelets (Table 1) " the resulting fibrin polymers are rapidly digested by plasmin and eliminated from the circulation via the reticuloendothelial system 1 ' 15 . Further cleavage of the de-"A"-fibrinogen molecule by thrombin to give natural fibrin no longer takes place because the resulting molecule is not a thrombin substrate.
• Ancrod causes a dose-dependent decrease in the blood fibrinogen concentration.
• Therapeutically induced and controlled hypofibrinogenemia diminishes the plasma viscosity and tendency of erythrocytes to aggregate so far that the flow properties of the blood are crucially improved. This provides the condition for greater flow of blood through stenosed vessels.
• Ancrod is currently approved to treat, for example, chronic disturbances of peripheral arterial blood flow and heparin-induced thrombocytopenia, and is undergoing clinical phase HI studies on acute ischemic stroke.
• the present invention provides an improved method for the treatment of ischemic stroke based on a specific rate and pattern of defibrinogenation and subsequent refibrogenation associated with optimized efficacy and significantly improved safety.
• the administration of a single dose of defibrinogenating agent within defined parameters achieves an optimal rate of defibrinogenation and avoids prolonged hypofibrinogenenemia and concomitant adverse side effects such as intracranial hemorrhage.
• the invention relates to a method for treating stroke that employs a method of administration of a defibrinogenating agent that achieves a desired pattern of rapid defibrinogenation followed by nomialization of blood fibrinogen levels.
• the invention in another aspect, relates to a method for treating stroke, the method comprising administering a defibrinogenating agent, such as ancrod, to a patient in need of such treatment at a rate sufficient to achieve rapid initial defibrinogenation.
• Administration of the defibrinogenating agent is terminated after a period of administration of about 30 minutes to 12 hours and subsequently, normalization of fibrinogen levels in the patient is allowed to occur without jEurther administration of the defibrinogenating agent.
• the invention relates to a method for treating stroke, the method comprising administering to a patient in need of such treatment a defibrinogenating composition comprising ancrod in a single continuous dose of about 0.05-1.25 IU/kg/hr, more preferably about 0.1-0.2 IU kg/hr and even more preferably, about 0.14-0.175 IU/kg/hr wherein normalization of fibrinogen levels in the patient is allowed to occur once administration of the defibrinogenating composition is discontinued, without further or additional administration of the defibrinogenating agent.
• a defibrinogenating composition comprising ancrod in a single continuous dose of about 0.05-1.25 IU/kg/hr, more preferably about 0.1-0.2 IU kg/hr and even more preferably, about 0.14-0.175 IU/kg/hr wherein normalization of fibrinogen levels in the patient is allowed to occur once administration of the defibrinogenating composition is discontinued, without further or additional administration of the def
• the invention relates to a method for treating stroke wherein the defibrinogenating agent is ancrod or a functional derivative thereof.
• FIGURE 1 is a schematic representation comparing the mechanisms of action of ancrod and thrombin on fibrinogen.
• FIGURE 2 depicts the effect on functional response, mortality and symptomatic intracranial hemorrhage (ICH) for a defibrinogenation rate of greater than or equal to 3O mg/dL/hr (light gray bars) compared to a rate of less than 30 lng/dL/hr (dark gray bars.)
• FIGURE 3 depicts the difference between an average end-of treatment fibrinogen level of greater than or equal to 60mg/dL (dark gray bars) and less than SOmg/dL (light gray bars) for functional response, mortality and symptomatic ICH.
• FIGURE 4 is a representative graph of the effect on mean plasma fibrinogen concentrations of three different doses of ancrod administered as a single dose over a 12- b-our time course.
• the broken line represents the effect (induction of l ypofibrinogenernia) of the multiple-day dosing paradigm currently used in the art.
• FIGURE 5 is a graph representing the occurrence of intracranial hemorrhage when the target fibrinogen level was 40-69mg/dL.
• FIGURE 6 is a graph representing the occurrence of intracranial hemorrhage when the target fibrinogen level was 70-100mg/dL.
• rapidly initial defibrinogenation refers to a rate of defibrinogenation, that is, an hourly decrease in fibrinogen, in excess of 20mg/dL/hr, more preferably in excess of 25mg/dL/hr and most preferably in excess of 30mg/dL/hr.
• normalization refers to the natural physiologic return to baseline levels, without additional intervention, that is, in the absence of continued administration of defibrinogenating agent.
• the term, as used, however, does not necessary imply that the rate of refibrinogenation is comparable to a normal physiological rate in an untreated subject.
• ancrod is used as the defribrinogenating agent for practicing the method of the present invention.
• the term "ancrod” encompasses not only products prepared from the ancrod protease isolated from the Malayan pit viper venom, but also functional derivatives thereof, including but not limited to products containing ancrod proteins obtained through recombinant technology. Examples of functional derivatives include ancrod proteins containing one or more amino acid additions, substitutions or deletions.
• Methods for the preparation of ancrod from snake venom are well known, and include, but are in no way limited to, the methods taught in United States Patents 6,200,791; 6,015,685; 3,743,722 and 3,879,369; Great Britain Patent documents 1,094,301; 1,177,506 and 1,293,793; and German patent documents 2,428,955 and 2,734,427. Methods for the preparation of ancrod products through genetic manipulation are taught, for example, in United States Patent 5,759,541.
• the present invention provides a method for the treatment of ischemic stroke based on a specific rate and pattern of defibrinogenation and subsequent refibrogenation that is associated with increased efficacy and safety.
• the administration of a single dose of defibrinogenating agent usually by intravenous infusion, over a period of from about 15 minutes to 12 hours and more preferably from about 30 minutes to 6 hours, achieves an optimal rate of defibrinogenation.
• cessation of administration of defibrinogenating agent after the desired time avoids prolonged hypofibrinogenenemia and concomitant adverse side effects such as intracranial hemorrhage.
• the method of the present invention provides for a treatment of ischemic stroke wherein a defibrinogenating agent is administered as a single continuous dose. Between 9 and 72 hours post-dosing, average fibrinogen levels greater than 50mg/dL, more preferably greater than 60mg/dL, and most preferably 70mg/dL, are achieved by simply stopping administration of the defibrinogenating agent.
• administering should be initiated as soon as practicable once a diagnosis of stroke has been made.
• dosages of ancrod or related defibrinogenating agents useful for achieving the objective of rapid initial defibrinogenation will depend on several factors, incl ⁇ ding the patient's fibrin(ogen) level prior to administration.
• the resulting dosing paradigm called for an initial infusion rate of 0.167 IU/kg/hr administered for a limited time that was determined by dividing the pretreatment fibrinogen level in mg/dL by 100, truncating the result, and then stopping the infusion after that number of hours (e.g., for a pretreatment fibrinogen level of 375 mg/dL, one would infuse for 3 hrs, and for a pretreatment fibrinogen level of 415 mg/dL, one would infuse for 4 hrs).
• the infusion was to resume at one-tenth the initial rate (i.e., 0.0167 IU/kg/hr) in order to maintain hypofibrinogenemia in the target range.
• Phase I human studies support the fact that single-administration dosing of ancrod across a range of doses and administered for various durations (30 minutes, 1- hour, 2 hours, 4-hours, 6-hours and 24-hours) will consistently yield the desired pattern of de-/re-fibrinogenation, and avoid prolonged hypofibrinogenemia. Specifically, rapid initial defibrinogenation can be achieved, and the optimally safe and effective end-of- treatment fibrinogen average can then be achieved by stopping the drug and allowing fibrinogen levels to recover naturally over a period of days.
• Efficacy defined as survival for 90 days and functional independence (Barthel Index [BI] scores of 95-100 or at least as good as the prestroke BI), was also demonstrated in a subsequent double-blind, placebo-controlled study of 50O patients randomized to ancrod or placebo within 3 hours of stroke onset 4 .
• BI Barthel Index
• a Phase III North American trial 4 a multi-center, parallel-group, sequential, double-blind, randomized, placebo-controlled study of the safety and efficacy of intravenous (IV) ancrod given within 3 hours after the onset of acute, ischemic stroke was conducted in 500 patients.
• IV intravenous
• Patients were included from " both sexes, who were at least 18 years of age, with acute or progressing ischemic (non-hemorrhagic) cerebral infarction with a neurological deficit that lasted longer than 30 minutes and occurred within 3 hours prior to study drug administration. Patients were to have a pretreatment SSS score less than 40, excluding gait, meaning that patients with mild stroke were excluded.
• the primary exclusion criterion based on blood pressure required that pre-treatment systolic pressure be ⁇ 185 mmHg and pre-treatment diastolic pressure be ⁇ 105 mrnHg.
• Ancrod (70 IU/mL) or placebo was diluted in a ratio of one ampule in each 250 mL normal saline. Defibrinogenation was induced with one of three initial infusion rates based on the pretreatment fibrinogen level (0.083 IU/kg/h, 0.125 IU/kg/h, and 0.167 IU/kg/h). The infusion was continued for 72 hours, followed by intermittent infusions administered at 96 ( ⁇ 6) and 120 ( ⁇ 6) hours after the start of blinded therapy. The dosing regimen permitted frequent regulation of infusion rates based on fibrinogen levels in order to achieve controlled defibrinogenation to levels of 40-69 mg/dL.
• Fibrinogen levels were provided only to an unblinded dosing supervisor at each site responsible for adjusting dosage.
• the unblinded dosing supervisor adjusted the rates as follows: for fibrinogen levels above the target, ancrod infusion rates were increased in 25-50%) increments and for fibrinogen levels below the target, ancrod infusion rates were decreased by similar decrements or replaced with saline.
• Placebo normal saline was administered in accordance with schedules derived from previously-treated ancrod patients.
• the primary efficacy variable was defined as survival for 9O days with a Barthel Index (BI) of 95-100 or at least as high as the prestroke BI.
• Secondary efficacy variables were the numerical BI (at 3 months), SSS score (at 3 days and 3 months), and CT infarct volume (at 7-10 days).
• the principal analysis was carried out on the entire 500 patients according to the intent-to-treat (ITT) principle.
• the primary efficacy variable was analyzed using a logistic model with terms for age, baseline SSS score, pooled center and treatment.
• Secondary and tertiary efficacy parameters were analyzed both with a Wilcoxon Rank Sum test and with a general linear model approach using the same terms (including interaction) as for the primary efficacy parameter.
• Age and pretreatment SS S scores are known to be predictors of outcome from stroke and, based on placebo rates of treatment success in this study, they were. Therefore, covariate-adjusted proportions of treatment success were calculated to provide a better estimate of the true treatment effect with age and pretreatment SSS scores as the covariates. The covariate-adjusted proportion of treatment successes was 42.2% in ancrod patients and 34.4% in placebo patients. No single site was disproportionately responsible for the favorable treatment effect.
• results of subgroup analyses including age category ( ⁇ 65, 65-74, 75-84, >85), pretreatment SSS category ( ⁇ 20, 20-29, 30-39), sex, and time-to-treatment ( ⁇ 2, 2-3, >3) were similar, with a higher proportion of ancrod patients achieving treatment success than placebo patients in all patient subsets characterized by age category, pretreatment SSS category, sex, early infarct signs on the pretreatment CT scan, and time-to-treatment.
• Ancrod benefit extended to those patients whose study drug treatment was delayed beyond 3 hours after stroke onset 4 . More ancrod patients treated within 3.5 hours of stroke onset achieved treatment success than placebo (p-O.029). This preservation of treatment effect beyond 3 hours is consistent with positive results in other 6-hour ancrod trials (A-20) and suggests that small errors in determining the time of stroke onset are not likely to detract from the beneficial effects seen with ancrod treatment.
• a rate of ancrod infusion of about 0_ 05- 1.0 IU/kg/hr, more preferably about 0.1-0.5 IU/kg/hr and most preferred about 0.16-0-25 IU/kg/hr consistently yields initial defibrinogenation at a rate of ⁇ 30 mg/dl/hr, which is correlated to positive efficacy outcomes (i.e., a positive functional response rate of 50*% alive with a Barthel Index score within 5 points of the prestroke score).

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• 2004
  • 2004-03-30 US US10/812,510 patent/US20050220782A1/en not_active Abandoned
• 2005
  • 2005-03-30 EP EP05733220A patent/EP1740271A1/en not_active Withdrawn
  • 2005-03-30 JP JP2007506521A patent/JP2007531759A/ja not_active Withdrawn
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