Transcript Potential Use Increases thrombin generation on activated platelet

New Trends In The
Management Of Bleeding
Disorders
Galila Zaher
MRCPath
Consultant Hematologist
KAUH
Congenital Bleeding disorders
 VWD
 Hemophilia
A
 Hemophilia B
 Other congenital factor deficiency
 Bernard Solier syndrome
 Glanzman’Thrombathenia
 Storage pool defect
Acquired Bleeding Disorders
Coagulation Factor
 Liver Disease
 DIC
 Consumptions Coagulopathies
 Vitamin K deficiency
 Platelets defects
 ITP
 Renal impairment
 Myelo-proliferate Disorders

Hemophilia
A
= F VIII deficiency
 B = F IX deficiency
 Affects one in 6000 males
 A is 5 X > B
 Mild >5,Moderate 2 -5, severe < 2 %
 Levels remain stable throughout life
 Both HA & HB are X linked
Clinical presentation
<
2 years: joint bleeds
– Rare
– Only bruising or mouth bleeds are seen
– Head injuries are a major concern

> 2 years
– Joint and muscle bleeds become more
common
Indication For Replacement
 All
joint bleeds: Pain, swelling
,warmth or loss of movement .
 Muscle bleeds : severe pain or are
in a dangerous location
 Bruises usually don’t need
treatment
Treatment
 Keep
weight off of joint
 Ice pack
 Factor replacement - the sooner
the better
 Amicar or tranexamic acid : mouth
bleed
Factor replacement
 Derived
from pooled human plasma
 Derived from pig (porcine) plasma
 Recombinant products
Factor VIII (AHF)
Mechanism of action
 No tool to predict the efficacy
 Allergic reactions
 Transient (short t ½)
 Expensive.
 Risk of transmission of infection

Biotech Development of
Recombinant Factors
Amplification
Human FVII gene
hF
Gene
Single copy
of gene isolated
Liver gene library
hF
gene
®
Activation
and Purification
Expression of
rF in culture medium
hF = human factor
BHK = baby hamster kidney
BHK cells
Recombinant Factors
Advantages :
 Safe and stable source of the agent
 When sources are scarce
Problems :
 Contaminating proteins :Infectious or
immunogenic agent
 Expensive
Genetic Study
Study the development of inhibitors.
 Gene Transfer
Sustained therapeutic production of factors
with No stimulation of an immune response .

The Tools of Genetic Engineering
 DNA
gene fragment of interest
 Endonucleases
 Plasmid
 Ligase
 Host that is capable of accepting DNA
 Insertion into the genetic machinery
 Confirm that the gene is inserted.
 Purify the protein of interest
Gene Transfer Clinical Trials
5
trials approved in the States .
 Retroviral vector :B-domain deletion
 Non-viral approach :reduction factor use
& spontaneous bleeding episodes.
 Gutless adenovirus : eliminate immune
response
Results Of Clinical Trials
 Long-term
therapeutic expression not
achieved, but data are encouraging.
 Detectable factor levels observed.
 The subjective : decreased bleeding .
 No evidence of inhibitor.
 Hepatic toxicity , thrombocytopenia.
 Decline expression .
Shortcoming Of Treatment
Modalities
Short T 1/2
 Coast
 Infections & Immunologic
 Hepatic toxicity ,low platelets
 Decline expression.
 Owing to the shortcoming of treatment
Modalities prompted the need for anew
hemostatic agent.

Initiation of Haemostasis
X
TF
IX
XIa
VIII/vWF
VIIa
TF-bearing cell
TF VIIa
IXa
X
X
IXa VIIIa
IX
prothrombin
Xa
Va
prothrombin
Xa Va
activated platelet
thrombin
platelet
thrombin
VIIIa
V
Va
XI
XIa
Fibrinogen
Fibrin

TF–independent mechanism of rFVIIa
enhanced hemostasis
Rational
 Thrombin
crucial role in haemostasis.
 Any agent that enhances the thrombin
generation 'general haemostatic agent'.
 rFVII enhances thrombin generation on
activated platelets
 Compensates for lack of FVIII and FIX.
 Normalize fibrin clot permeability
Pharmacokinetic
t½ :2.7 h
 Inter-subject variability.
 Rapid clearance in children > adults.
 No readily available assays
 The haemostatic levels remains
uncertain.
 Frequent bolus injections, IVI potential
to minimize usage.

Potential Use

Increases thrombin generation on activated
platelet
– Hemophilia (FVIII/FIX deficiency)
– Acquired hemophilia.
– Platelet disorders qualitative and quantitative
– Diffuse bleeding triggered by surgery and trauma.
Impaired initial hemostasis
– FVII-deficiency
– Liver disease
– Oral anticoagulant therapy
Hemophilia with inhibitors
FDA Approved Feb 1999
 Bleeding during or prior to ITI therapy.
 Control bleeding during surgery.
 Safe and effective in 92% hemophilia
research society registry
 Inhibitor titres are not boosted.
 Home treatment: mild-moderate episodes.
 Recommended dose 60-120 ug/kg q 2 -6 h or
IVI.

Acquired Hemophilia
 Rare
but potentially life-threatening
condition mortality rate 20%.
 Auto-antibodies against the deficient
factor.
 rFVIIa is effective in major bleeding
 Induces haemostasis independent of the
presence of FVIII or FIX.
 Well tolerated in these patients
Liver Disease
 Reduction
in the synthesis of factors
involved in coagulation and fibrinolysis.
 Moderate thrombocytopenia.
 Upper gastrointestinal tract.
 Vitamin K .
 FFP
 PCCs : thromboembolic complications.
rFVII &Liver Disease
 Acute
hepatic trauma, liver biopsy,
chronic liver disease ,cirrhosis, and
liver transplantation.
 Experimental studies :seems to be safe
and effective.
 No evidence of thrombosis .
 Cirrhosis , achieved hemostasis in 74%
Jeffers et al
The Risk Of Thrombosis In LIVER
Patients
 No
evidence of dose relationship
 Many events have an alternative
aetiology
 Few events within the first day after
dosing
 No increase in events as compared with
background transplant population
Drug-Induced Coagulopathy
Oral anticoagulant treatment  hemorrhage
:0.6%/ m .
 Vitamin K, FFP or PCCs
 rFVIIa in healthy volunteers :50% drop of
INR
Girard et al
 An open, multicenter pilot trial is underway to
determine the efficacy
 Fondaparinux. normalized PT, aPTT, and TT.

Bijsterveld et al
Glanzmann’s Thrombasthenia
Refractory to platelet transfusion
 Increases the initial thrombin generation,
thereby compensating for defective platelet
 Effective in 60% during surgery .
 No adverse effects of rFVIIa
 International registry data :relatively safe
and effective when used in GT.

Blood 1999; 94 (11): 3951-3953
Thrombocytopenia
Increased thrombin generation on
activated platelets compensate for the
low platelet number.
 Reduction in bleeding time in 52.4% of
105 patients .
Kristensen et al
 No
major adverse
Surgical &Trauma patients
Effective and safe in the management of
uncontrolled surgical in patients not known to
have inherited coagulopathy.
 Trauma :surgical intervention failed to stop
life- threatening bleeding.
– Significant decrease to 2 packed RBC
– Shortening of PT & aPTT
 Adjunctive hemostatic treatment
 Theoretical risk of TED ,none observed
Building Strong Scientific
Evidence
Clinical area
 Liver transplantation
 Upper GI bleeds
 Liver resection
 BMT
 Reversal of OAC
 Traumatology
Status on project
Ph 2 study
Ph 2 study
Ph 2 study
Ph 2 study
Ph 2 to be started
Ph 2 to be started
Questions more than answers
 Optimal
dosage.
 Dosing interval.
 Adjunctive hemostatic treatment .
 ‘General haemostatic agent.
 Thromboembolic events .
 Coat analysis studies.
 Need for evidence-based guidelines
Local experience
 Acquired
Hemophilia
 Fresh PR bleeding
 FFP. Cryoppt,FVIII conc
 In preparation for molar root extract
 FVIII conc 100IU/Kg
 rFVII 30IU
 Normal hemostasis
 Tranexamic acid
Thank You
Amount of thrombin formed in the
initial burst is critical to assure
1.
assembly of a thick, strong fibrin
plug
2.
activation of FXIII to cross link
fibrin
3.
activation of TAFI to make
fibrin plug resistant to fibrinolysis
RNA repair
Pre-messenger RNA (pre-mRNA) repair.
 splicing mechanisms to correct a portion of
the defective RNA.
 The advantage :large genes or genes that
contain large regulatory elements.
 Injection of a plasmid encoding a pre-mRNA
 Useful for the treatment of autosomal
dominant disorders.

Inhibitors &Gene Transfer
Inhibitors :20% HA patients and 3% of HB
patients.
 Antibodies inactivate the factor by changing
conformation.
 Depends on type of genetic mutation.
 A large deletion  incidence of inhibitor .
 Bleeding episodes are difficult to manage

Human/porcine
factor VIII
FEIBA