Jump to content

Ancrod

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 216.46.75.218 (talk) at 15:22, 31 May 2007 (Updates made to clarify that this product is not currently available; it is in clinical trials for stroke.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Ancrod (former brand name: Arwin®; current brand name: Viprinex®) is an anticoagulant, fibrinolytic, and reperfusion therapy. Currently, Viprinex®/ancrod is not approved or marketed in any country, but is being investigated as a stroke treatment in worldwide clinical trials. In January 2005, the U.S. FDA granted a 'fast-track status' for investigation of ancrod use in patients suffering from ischemic stroke, a life threatening condition caused by the blockage of blood vessels supplying blood and oxygen to portions of the brain, for which phase III studies have been and are currently being conducted.

Ancrod
File:Ancrod.png
Clinical data
Pregnancy
category
  • X (contraindicated)
Routes of
administration		s.c. injection or i.v. infusion
Legal status
Legal status
  • Rx only, where available
Pharmacokinetic data
Bioavailability100% after i.v. dosing
Protein binding95% bound to erythrocytes
Metabolismmainly renal
Elimination half-life3 to 5 hours
Identifiers
  • Ancrod, Ophidian l-amino-acid oxidase (l-amino-acid oxygen:oxidoreductase, deaminating)
CAS Number
ECHA InfoCard100.029.927 Edit this at Wikidata

Marketing Information

Under the brand name Arwin®, ancrod was marketed in Germany and Austria, where it was withdrawn in the 1980s after it was used for some decades. Arwin® was a brand name of Knoll Pharma. Neurobiological Technologies, Inc., currently holds the worldwide rights to ancrod under the brand name Viprinex®. Previously, the rights to Viprinex® were respectively held by Empire Pharmaceuticals, Inc., Abbott Laboratories, and Knoll AG, developers of this investigational drug.

Neurobiological Technologies, Inc. (NTI) has signed agreements with Nordmark Arzneimittel GmbH & Co KG (Nordmark) and Baxter Pharmaceutical Solutions, LLC (Baxter) to manufacture, fill and package Viprinex® for NTI's Phase III clinical trials in acute ischemic stroke. Nordmark will manufacture the biological active ingredient, ancrod. Date of this agreement was 1st. August 2005.

Basic Chemical and Pharmacological Information

Ancrod has a triple mode of action. The exact structure and chemical data such as molecular weight are unknown, but it has been elaborated that the glycosylation of the molecule is an important factor. Glycosylation is remarkably homogenous with the major oligosaccharide accounting for approximately 90% of the total sugar content. Some in vitro reactions have been explored in very detail (see ref. #2, www.blckwell-synergy). Experimentally it was found that ancrod's actions are FAD dependent and that the substance has interesting apoptotic properties (causing programmed cell death), which still remain to be elaborated.

Ancrod is prepared from the crude venom of the Malayan pit viper (Agkistrodon rhodostoma, also termed Calloselasma rhodostoma) and belongs to the group of proteolytic enzymes. Ancrod may also be found in the venoms of many poisonous snakes (crotalids, elapids and viperids) in general, but the Malayan pit viper is most suitable due to a high concentration of ancrod in its venom. For its preparation a snake farm, very skilled and well trained staff (for milking the highly poisonous snakes), and special production facilities are required to purify the enzyme.

The halflife of ancrod is 3 to 5 hours and the drug is cleared from plasma, mainly renally.

Due to its special mode of action (see below) and its price, Arwin® was never been used as 'normal' anticoagulant such as heparin, but only for the symptomatic treatment of moderate to severe forms of peripheral arterial circulatory disorders such as those resulting from years of heavy smoking and/or arteriosclerosis.

The substance is intended for parenteral, namely subcutaneous (s.c.) injection and intravenous (i.v.) infusion, and indirectly inhibits aggregation, adhesion, and release of thrombocytes mediated through the action of a fibrinogen degradation product (FDP). It also cleaves and therefore inactivates a significant part of circulating plasma fibrinogen. Fibrinogen is often found in increased concentrations in arteriae with impaired circulation. This leads to a pathologically increased blood viscosity and thereby to a worsening of symptoms of the circulation disorder (more intense pain, decreased mobility of the limb and decreased temperature, need for partial or even total limb amputation). The blood viscosity in patients receiving ancrod is progressively reduced by 30 to 40% of the pretreatment levels. The decreased viscosity is directly attributable to lowered fibrinogen levels and leads to important improvements in blood flow and perfusion of the microcirculation. Erythrocyte flexibility is not affected by normal doses of ancrod. The rheological changes are readily maintained and the viscosity approaches pretreatment values very slowly (within about 10 days) after stopping ancrod. One of the cleavage fibrinogen products, termed 'desAA-Fibrin', acts as cofactor for the tPA-induced plasminogen activation and an increased fibrinolysis results in return (profibrinolytic activity of ancrod).

Ancrod decreases the blood viscosity in affected arteries, leads to less intense pain, improves physical limb mobility, and faciliates physical and ergo therapy. Finally, ancrod decreases the likelihood of local thrombotic events.

The above mentioned mechanisms also account for ancrod's activity in other diseases.

Effects on Other Clotting Factors: Unlike thrombin, ancrod does not directly activate Factor XIII, nor does it produce platelet aggregation nor cause the release of ADP, ATP, potassium, nor serotonin from platelets. Platelet counts and survival time remain normal during ancord therapy.

Prior Indications for Ancrod

For the treatment of established deep vein thrombosis; central retinal and branch vein thrombosis; priapism; pulmonary hypertension of embolic origin; embolism after insertion of prosthetic cardiac valves; rethrombosis after thrombolytic therapy and rethrombosis after vascular surgery. It is also indicated for the prevention of deep venous thrombosis after repair of the fractured neck of a femur.

For the treatment of moderate and severe chronic circulatory disorders of peripheral arteries (e.g., arteriosclerosis obliterans, thromboangiitis obliterans, diabetic microangiopathy and Raynaud's phenomenon).

Ancrod has been shown to be useful for maintaining anticoagulation in the presence of Heparin-induced thrombocytopenia (HIT) and thrombosis.

Currently, this drug is not approved nor available. It is being investigated in clinical trials for stroke.

Study Results in Patients with early Ischemic Stroke

In a multicenter, parallel, group sequential, randomized, double-blind, placebo-controlled German study of efficacy and safety of i.v. ancrod given within 6 hours after the onset of acute, ischemic stroke and continued for 5 days (called ESTAT study), the early findings for 800 patients were positive, but as the study was expanded to 1,600 patients, placebo was found to be more effective than ancrod and the study was abruptly terminated, mainly because the mortality in the ancrod group was higher. The smaller American study 'Stroke Treatment with Ancrod Trial (STAT)' confirmed the negative outcome for ischemic stroke. In these studies, patients received a multi-day infusion of Viprinex designed to maintain patients’ fibrinogen level within a targeted range. Currently, a new dosing strategy is being investigated in two international phase III trials as part of the 'Ancrod Stroke Program (ASP).' Each of these studies will enroll 650 patients and assess whether a brief, relatively rapid ancrod infusion with no maintenance dosing will be both effective and safe.


Contraindications and Precautions

Pregnancy

Category X : Ancrod was not found to be teratogenic in animal studies, but some fetal deaths occurred as a result of placental hemorrhages in animals given high doses; therefore, it should not be used during pregnancy as the defibrinogenation mechanism of ancrod might be expected to interfere with the normal implantation of the fertilized egg.

Side-Effects

  • Hypersensitivity reactions : Local or generalized skin reactions (rash and urticaria); appearance of neutralizing antibodies to ancrod with partial or total loss of ancrod activity (drug resistance).
  • Sometimes pain at injection site (normally mild). This side-effect may be, if necessary, treated with local or oral antihistaminic drugs (e.g., clemastine, or diphenhydramine). Bleeding at injection site, thrombophlebitis at local veins, and (paradoxical) arterial thrombotic events.
  • Occasionally deposition of cleaved fibrinogen derivates in the splen resulting in splenomegaly; rupture is possible, if the spleen is palpated too strongly (life-threatening bleeding and need of splenectomy may result).
  • Specific side-effects are local and systemic bleeding events. Local bleeding events may be treated with local pressure or surgical dressings, if necessary. Compared with other anticoagulants the risk of systemic bleeding is relatively low. If systemic bleeding is severe enough to warrant fast reversal of ancrod action, fibrinogen should be substituted (please refer to section 'special antidotes').
  • Occasionally, increased headache has been found in patients with known migraine.
  • Also, chills and fever may occur infrequently.

Thrombocytopenia as side-effect has never been noticed with ancrod in contrast to heparin.

Interactions

The risk of bleeding events is increased, if other anticoagulants (e.g., coumarines such as warfarin), inhibitors of thrombocytic aggregation such as aspirin, or fibrinolytics such as urokinase are used concomitantly or within a period of 10 days after discontinuation of ancrod.

Plasma expanders: Artificial plasma expanders (e.g. dextran) may cause severe bleeding in defibrinated patients and should not be administered during or within 10 days of ancrod therapy.

Severe GIT-bleedings may result from the concomitant use of NSAIDs, glucocorticosteroids, niacin derivates, or other drugs with ulcerogenic potential.

The danger of thromboembolic events is considerably increased, if ancrod is given immediately after systemic fibrinolytics.

Necessary Laboratory Examinations

Pretreatment investigations: A complete blood cell count, including platelet count, and fibrinogen determination should be obtained before treatment.

In case of significant bleeding events : Hemoglobin, hematocrit, and a complete red cell status should be obtained. Blood pressure values should be monitored to exclude the development of an impending hemorrhagic shock.

Laboratory Control during Induction Dose Infusion: The fibrinogen concentration should be measured at six hours intervals during, and at the end of the infusion of the induction dose.

Prior Dosage Regimen

Usually, a (high) induction dose of Arwin® was given as i.v. infusion for 12 hours to reach the desired decreased level of fibrinogen quickly, followed by regular lower dose infusions or s.c.-injections.

Special Antidotes

In case that quick reversal of Arwin® action was required, a special antidote was available from Knoll at no cost; it was a serum from the goat containing a high concentration of antibodies to ancrod, with which ancrod could be neutralized rapidly. Nonetheless, it was often necessary to restore normal fibrinogen activity with cryoprecipitate after use of the antidot, because the body needs some time to restore fibrinogen levels on its own. The aforementioned antidot is not obtainable any longer. Now, cryoprecipitate should be administered alone to raise the plasma fibrinogen concentrations to safe levels. Whole blood transfusions are also suitable, particular where cryoprecipitate is not available. Anemia related to severe bleeding events can be corrected with packed red blood cells or whole blood.

Drug Availablility

Viprinex® is not currently approved or available.

External References


Retrieved from "https://en.wikipedia.org/w/index.php?title=Ancrod&oldid=134827665"