OERMATAN SULFATE: A NEW CONCEPT IN ANTITHROMBOTIC THERAPY

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1 OERMATAN SULFATE: A NEW CONCEPT IN ANTITHROMBOTIC THERAPY by JOANNE VAN RYN-McKENNA, B.Sc., M.Sc. A Thesis Submitted to the School of Graduate Studies in Partial Fulfilment of the Requirements for the Degree Doctor of Philosophy McMaster University (April 1991)

2 DERMATAN SULFATE: A NEW CONCEPT IN ANTITHROMBOTIC THERAPY

3 DOCTOR OF PHILOSOPHY (1991) McMASTER UNIVERSITY Hamilton, Ontario TITLE: Oermatan Sulfate: A New Therapy Concept in Antithrombotic AUTHOR: Joanne Van Ryn-McKenna, B.Sc. (McMaster University) M.Sc. (McMaster University) SUPERVISOR: Professor M.R. Buchanan NUMBER OF PAGES: xiv, 171 ii

4 ABSTRACT DERMATAN SULFATE: A NEW CONCEPT IN ANTITHROMBOTIC THERAPY This study was undertaken to explore the hypothesis that dermatan sulfate, which catalyses thrombin inhibition by heparin cofactor II, prevents thrombosis more effectively than heparin, which catalyses throdwin inhibition by antithrombin III. The rationale for this hypothesis is based upon three general observations. First, higher doses of heparin are required for the treatment of thrombus growth than are required for the prevention of thrombus formation. second, thrombin bound to fibrin or to vessel wall components in vitro is resistant to inhibition by heparin/antithrombin III. Third, preliminary evidence indicates that the catalysis of thrombin inhibition by antithrombin III-independent inhibitors may be more effective than heparin/antithrombin III. The results of this present study support the above hypothesis and demonstrated that dermatan SUlfate, a glycosaminoglycan which catalyses thrombin inhibition by heparin cofactor II, i~hibited i) thrombus formation, ii) thrombus growth, and iii) acted synergistically with tpa to enhance thrombolysis, more effectively than heparin. These effects were achieved with iii

5 minimal detrimental side-effects. These results indicate that dermatan sulfate is an effective antithrombotic agent and support the conclusion that the catalysis of thrombin inhibition by dermatan sulfate/heparin cofactor II provides a more effective pathway for preventing thrombus formation and thrombus growth than the catalysis of thrombin inhibition by heparin/antithrombin III. iv

6 ACKNOWLEDGEMENTS The work described in this thesis was performed under the supervision of Dr. M.R. Buchanan. I wish to thank Dr. Buchanan for his continual encouragement, for his lessons in critical evaluation of both experimental and writte! work, and for his support during the course of my thesis work. I would also like to thank Dr. F.A. Ofosu for his continual interest, encouragement and suggestions. I also wish to thank Drs. J. Hirsh and G. Singh for their guidance and critical reviews during the course of my thesis work. There are many other people I wish to thank, who through their generous assistance have made the completion of this thesis an easier task, including Ms. M. Falcone, Dr. E. Gray, and Dr. J. okwusidi. I especially wish to thank Dr. L. Cai, for her excellent technical assistance, Dr. M. Bertomeu, for her never ending encouragement and Dr. P. Brill-Edwards, for introducing me to my computer. I also wish to thank my husband, Sean, who always gave me his unfailing support and encouragement. This work was supported by student fellowships from the Canadian Heart and Stroke Foundation and the Medical Research Council of Canada. v

7 TABLE OF CONTENTS CHAPTER 1 INTRODUCTION... 1 I. COAGULATION AND THROMBUS FORPATION II. ANTICOAGULANT PROPERTIES OF HEPARIN AND DERMATAN SULFATE structure and heterogeneity of heparin and dermatan sulfate Anticoagulant actions of heparin (a) Catalysis of thrombin and factor Xa inhibition by antithrombin III (b) Catalysis of thrombin inhibition by heparin cofactor II (c) Heparin cofactor independent effects Anticoa~alant action of dermatan sulfate (a) Catalysis of thrombin inhibition by heparin cofactor II Relative importance of factor Xa and thrombin inhibition III. PHARMACOKINETICS AND PHARMACODYNAMICS: POTENTIAL INFLUENCE ON COAGULATION Intravenous heparin Intravenous low molecular weight heparin fractions Intravenous dermatan sulfate Importance of glycosaminoglycan clearance for achieving anticoagulant arlo antithrombotic effects vi

8 IV. THE PREVENTION OF VENOUS THROMBOSIS BY HEPARIN AND DERMATAN SULFATE Clinical use of heparin in the prevention of venous thrombosis Heparin and dermatan sulfate in the prevention of venous thrombosis in experimental models. 28 Ca) Stimulus initiating thrombosis (b) Relative importance of anti-factor Xa activity and anti-thrombin activity. 29 V. THE TREATMENT OF VENOUS THROMBOSIS BY HEPARIN AND DERMATAN SULFATE VI. HEPARIN INTERACTIONS WITH tpa ON FIBRINOLySIS Fibrinolysis and the mechanism of action of tpa ' Interactions between tpa and heparin.. 36 (a) Clinical studies 36 (b) Experimental studies 37 VII. HEMOR~~GIC SIDE-EFFECTS 39 VIII. THE TREATMENT OF ARTERIAL THROMBOSIS Clinical use of heparin in the treatment of arterial thrombosis Experimental use of heparin in the treatment of arterial injury 42 AIMS OF PRESENT STUDy CHAPTER 2 MATERIALS AND METHODS Materials. 47 (a) Glycosaminoglycans and other drugs used in yivq (b) Other anticoagulants 48 (c) Anesthetics (d) Anticoagulant assay materials 48 (e) Prothrombotic stimuli 49 vii

9 ( f) Rabbits Methods (a) Processing of blood samples 49 (b) Anticoagulant parameters (i) Measurement of anticoagulant levels (c) (d) (e) ( f) (g) 3. (a) (b) (c) (d) (e) ( f) ex V1VO (ii) Anti-factor Xa ajsay (iii) Anti-thrombin assay (iv) «z-antiplasmin assay (v) Plasma fibrinogen levels Preparation of radiolabelled dermatan sulfate. (i) Coupling dermatan sulfate to SHPP. (ii) Radiolabelling SHPP-dermatan sulfate... (iii) protamine sulfate assay..... Preparation of radiolabelled fibrinogen..... (i) Fibrinogen purification (ii) Clottable fibrinogen assay.... (iii) Labelling purified fibrinogen Radiolabelling fjrothrombin... prepara~ion of lcr-labelled platelet suspens1.on.. statistical Analysis Experimental Designs Determination of the distribution and clearance half-lives of dermatan sulfate.. 63 (i) Calculation of the «, p and 1 half- lives of DS30. Prevention of venous thrombosis... Treatment of venous thrombosis.. (i) Prevention of 12SI - f ibrin accretion (ii) Prothrombin clearance and accretion Venous fibrinolysis model Hemorrhagic side-effects. continuous arterial injury CHAPTER 3 RESULTS 74 I. PHARMACOKINETICS AND PHARMACODYNAMICS OF DERMA.TAN SULFATE Pharmacokinetics Pharmacodynamics.. 75 viii

10 II. EFFECTS OF DERMATAN SULFATE AND HEPARIN IN THE PREVENTION OF VENOUS THROMBOSIS Tissue thromboplastin-induced thrombus formation Thrombin-induced thrombus formation Factor Xa-induced thrombus forma~ion Anticoagulant activity ex vivo Summary III. EFFECTS OF DERMATAN SULFATE AND HEPARIN ON THE TREATMENT OF VENOUS THROMBOSIS 89 l. Inhibition of thrombus growth by a continuous infusion of dermatan sulfate and heparin Effects of dermatan sulfate and heparin on prothrombin turnover in animals with an existing thrombus Inhibition of thrombus growth by a bolus injection of dermatan sulfate and heparin Summary IV. EFFECT OF DERMATAN SULFATE AND HEPARIN ON FIBRINOLYSIS BY tpa Possible synergistic effects of dermatan sulfate or heparin with tpa in lysing an existing thrombus Ex vivo anti-factor Xa and anti-thrombin levels Ex vivo cx 2 -antiplasmin levels Ex vivo fibrinogen levels 106 t 5. Summary ix

11 V. BLEEDING SIDE-EFFECTS Cumulative blood loss Cumulative blood loss in the presence of tpa Summary VI. CONTINUOUS ARTERIAL INJURy Effects of dermatan sulfate and heparin on platelet and fibrin deposition in the presence of an indwelling cannula Platelet half-life Ant~c~agula~t activity ex vivo after drug adm~n.1stratl.on Summary CHAPTER 4 DISCUSSION... ~ I. PHARMACOKINETICS AND PHARMACODYNAMICS OF DERMATAN SULFATE II. ANTITHROMBOTIC EFFECT OF HEP~JRIN AND DERMATAN DERMATAN SULFATE Prevention of venous thrombosis Treatment of venous thrombosis Clinical Relevance III. EFFECTS OF DERMATAN SULFATE AND HEPARIN ON tpa-induced FIBRINOLySIS. 142 IV. BLEEDING SIDE-EFFECTS V. EFFECTS OF DERMATAN SULFATE AND HEPARIN IN THE PREVENTION OF ARTERIAL INJURy StJMM'ARy. 151 REFERENCES x

12 LIST OF TABLES Number Condensed Title ~ 1 The 0:-, p-, and -y-half-lives of 125I_SHPP_ 0530 after an intravenous bolus injection Thrombus size in untreated animals injected with tissue thromboplastin, thrombin or factor Xa e Anti-factor Xa and anti-thrombin levels after injection of heparin, D530, DS48 or saline 88 4 Effect of DS48, heparin and hirudin on 12"5I-thrombin and 12SI-albumin accretion onto existing thrombi 95 X1

13 LIST OF FIGURES Number Condensed Title 1 A summary of the different pathways in the coagulation cascade The major repeating disaccharides of heparin and dermatan sulfate Diagrammatic representation of heparin, antithrombin III, factor Xa and thrombin and their interactions Diagrammatic representation of dermatan sulfate heparin cofactor II and thrombin and their interactions Diagrammatic representation of thrombin bound to fibrin and its protection from inhibition by heparin/antithrombin III standard curves obtained for heparin, DS48 and DS30 using chromogenic assays for antithrombin and anti-factor Xa activity The clearance curve of radioactivity after a bolus injection of DS Schematic representation of the experimental design used fo~ the treatment of venous thrombosis Elution of 12SI-SHPP-OS30 and native DS30 from a Sephacryl column The clearance curve of radioactivity after a bolus injection of 40 U/kg of 12I-SHPP-DS The ex vivo anti-thrombin activity after the injection of increasing doses of OS The effect of heparin, D530 and D548 in inhibiting thrombus formation initiated by tissue thromboplastin 83 xii

14 13 The effect of heparin, 0530 and OS48 in inhibiting thrombus formation initiated by thrombin The effect of heparin, 0530 and 0548 in inhibiting thrombus formation initiated by factor Xa The effect of heparin, 0530 and 0548 in inhibiting fibrin accretion onto existing thrombi after a continuous infusion The effect of a t~rombus on prothrombin clearance ± 0548 or heparin The effect of 0548 and heparin in inhibiting fibrin accretion after a bolus administration Anticoagulant activity over 4 hours after a bolus injection of increasing doses of Anticoagulant activity over 4 hours after a bolus injection of increasing doses of heparin The thrombolytic effect of a co-administration of either D548 or heparin with tpa Anticoagulant activity after a 4 hour infusion of 1.5 U/kq/hr of D548 or 120 U/kg/hr of heparin in combination with tpa «2-Antip1asmin levels after a 4 hour infusion of tpa in combination with either 0548, heparin or placebo Fibrinogen levels after a 4 hour infusion of tpa in combination with either 0548, heparin or placebo cumulative blood loss over 4 hours after an infusion of 30 U/kg/hr of 0548, 0530 or heparin cumulative blood loss over 4 hours after an infusion of 120 U/kq/hr of 0548, D530 or heparin xiii

15 26 Cumulative blood loss over 4 hours after an infusion of tpa, [tpa and 0548] or [tpa and heparin] Effects of 0548, heparin and aspirin on platelet deposition after 48 hours in response to a continual arterial 1nJury Effects of 0548, heparin and aspirin on fibrin deposition after 48 hours in response to a continual arterial injury ummary of the enhanced or inhibited platelet and f~brin dep~s~tion in the presence of 0548, hepar1n or asp1r1n Effect ~f a continual arterial injury on platelet half-life in the presence and absence of treatment Anticoagulant levels after drug administration measured over 48 hours Diagrammatic representation of thrombin present in solution or bound to fibrin in a thrombus Diagrammatic representation of thrombin inhibition by heparin/antithrombin III in the fluid and solid phase Diagrammatic representation of thrombin inhibition by dermatan sulfate/heparin cofactor II in the fluid and solid phase. 139 xiv

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Session 1 Topics. Vascular Phase of Hemostasis. Coagulation Pathway. Action of Unfractionated Heparin. Laboratory Monitoring of Anticoagulant Therapy

$Session 1 Topics. Vascular Phase of Hemostasis. Coagulation Pathway. Action of Unfractionated Heparin. Laboratory Monitoring of Anticoagulant Therapy$ ~~Marshfield Labs Presents~~ Laboratory Monitoring of Anticoagulant Therapy Session 1 of 4 Session 1 Topics Review of coagulation and the vascular phase of hemostasis Unfractionated heparin Low molecular