Potential of the Factor Xa Inhibitor Rivaroxaban for the Anticoagulation Management of Patients with Heparin-Induced Thrombocytopenia

1
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia

• Jeanine M. Walenga, Walter P. Jeske, Margaret
  Prechel, Debra Hoppensteadt, Amanda Drenth,
  Jessica Swank, Meredith McDonald, Luke Sheen,
  Omer Iqbal, Brian Neville
• Presented at the XXIst Congress of International
  Society on Thrombosis and Haemostasis (ISTH)
  2007 Meeting, July 6-12th in Geneva, Switzerland.

2
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Background

• Approximately 15 of patients receiving heparins
  (unfractionated heparin UFH and the low
  molecular weight heparins LWMHs) develop
  heparin-induced thrombocytopenia (HIT), which is
  associated with a substantially increased risk of
  thrombosis
• HIT is caused by the production of antibodies to
  a complex of heparin and platelet factor 4 (PF4),
  and subsequent cross-reaction of these HIT
  antibodies with heparinPF4

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
3
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Background

• Current guidelines recommend the use of a direct
  thrombin inhibitor (DTI) in patients with HIT
• DTIs administered parenterally are associated
  with a high bleeding risk, as well as other
  drug-specific limitations

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
4
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Background

• Rivaroxaban is a novel, oral, direct Factor Xa
  (FXa) inhibitor in advanced clinical development
  for the prevention and treatment of
  thromboembolic disorders
• Rivaroxaban may be suitable for the prevention
  and treatment of thrombosis in patients with HIT,
  because it is structurally unrelated to UFH,
  LMWHs and the heparin-based indirect FXa
  inhibitor fondaparinux, and, therefore, would not
  be expected to generate or cross-react with HIT
  antibodies

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
5
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Objective

• To evaluate, in vitro, the potential of
  rivaroxaban as an anticoagulant for the
  management of patients with HIT

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
6
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Methods

• Several drugs were compared to rivaroxaban in
  the treatment of HIT
• UFH
• the LMWH, enoxaparin
• fondaparinux
• the DTI, argatroban
• saline, as a control

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
7
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Methods

• Serum was collected from 89 patients with HIT
• Three functional assays of platelet activation or
  aggregation were used to determine any
  cross-reaction between rivaroxaban, or other
  drugs, and HIT antibodies
• 14C-serotonin release assay (in washed platelets)
• Heparin-induced platelet aggregation assay (in
  platelet-rich plasma platelet activation defined
  as gt20 aggregation)
• Flow cytometric analysis of platelet activation
  (platelet microparticle formation, platelet
  aggregation, and platelet P-selectin expression
  positive platelets and mean fluorescence
  intensity) in whole blood

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
8
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Methods

• Several drugs were compared to rivaroxaban in
  the treatment of HIT
• UFH
• The LMWH, enoxaparin
• Fondaparinux
• The DTI, argatroban
• Saline, as a control
• Rivaroxaban was tested in a total of 152
  different HIT antibody/donor platelet
  combinations using the three assays

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
9
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Methods

• PF4 release assay
• The release of PF4 from platelets was measured by
  ELISA
• Whole blood or platelet-rich plasma was incubated
  at 37C for 30 minutes with stirring
• The assay was repeated after activation of
  platelets by tissue factor
• PF4 binding assay
• The activity of study drugs (anti-FXa activity of
  rivaroxaban and fondaparinux anti-thrombin
  activity of heparins and argatroban) was measured
  before and after incubation with 10 µg/ml
  purified PF4 at 37C for 30 minutes, with stirring

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
10
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Results

• 14C-serotonin release assay
• Rivaroxaban, fondaparinux and argatroban did not
  activate platelets in the presence of HIT
  antibodies
• i.e. no concentration-dependent increase in
  activity
• As expected, strong, concentration-dependent
  platelet activation was observed with therapeutic
  concentrations of UFH and enoxaparin
• The absence of platelet activation at
  supra-therapeutic concentrations is typical of a
  heparin-dependent, platelet antibody activation
  response

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
11
14C-Serotonin Release Assay
Values are shown as meanSD.Walenga JM, et al.
Presented at ISTH 2007 in Geneva, Switzerland,
abstract P-M-648.
12
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Results

• Heparin-induced platelet aggregation assay
• Rivaroxaban did not activate platelets in the
  presence of HIT antibodies
• Fondaparinux caused activation of platelets in
  only one of the 18 sera samples tested
• UFH and enoxaparin strongly induced platelet
  activation in 100 and 70 of sera samples,
  respectively

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
13
Heparin-Induced Platelet Aggregation Assay
Values are shown as meanSD.Walenga JM, et al.
Presented at ISTH 2007 in Geneva, Switzerland,
abstract P-M-648.
14
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Results

• Flow cytometric analysis of platelet activation
• Rivaroxaban, fondaparinux and argatroban did not
  activate platelets in the presence of HIT
  antibodies (i.e. no concentration-dependent
  increase in parameters of platelet activation
  data not shown)
• UFH and enoxaparin induced strong,
  concentration-dependent platelet activation in
  the presence of HIT antibodies (data not shown)
• PF4 release assay
• Rivaroxaban and fondaparinux did not activate
  platelets, as measured by PF4 release
• UFH and enoxaparin caused strong platelet
  activation

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
15
PF4 Release Assay
140
120
100
80
PF4 Release (ng/ml)
60
40
20
0
Saline
Rivaroxaban(1 mg/ml)
Enoxaparin(5 mg/ml)
Fondaparinux(1 mg/ml)
UFH(5 mg/ml)
Values are shown as meanSD.Walenga JM, et al.
Presented at ISTH 2007 in Geneva, Switzerland,
abstract P-M-648.
16
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Results

• PF4 binding assay
• The anti-FXa activity of rivaroxaban and
  fondaparinux was unchanged after incubation with
  PF4, as was the anti-thrombin activity of
  argatroban
• The anti-thrombin activity of UFH and enoxaparin
  was decreased by 64 and 43, respectively

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
17
PF4 Binding Assay
Values are shown as meanSD.Walenga JM, et al.
Presented at ISTH 2007 in Geneva, Switzerland,
abstract P-M-648.
18
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Conclusions

• Unlike UFH and enoxaparin, Rivaroxaban
• Did not cross-react with HIT antibodies
• Did not interact with PF4
• Did not mobilize PF4 from platelets
• Rivaroxaban may be considered an alternative
  anticoagulant for the management of patients with
  HIT

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
19
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Conclusions

• Rivaroxaban, if used as the initial anticoagulant
  in place of heparin, may not initiate HIT
  antibody production
• Rivaroxaban, administered orally, could be used
  for long-term secondary prevention after an acute
  episode of HIT

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.
20
Potential of the Factor Xa Inhibitor Rivaroxaban
for the Anticoagulation Management of Patients
with Heparin-Induced Thrombocytopenia
Conclusions

• Further clinical investigation is required to
  confirm the potential of rivaroxaban as an
  alternative anticoagulant for the management of
  patients with HIT
• Rivaroxaban may offer certain advantages over
  currently approved DTIs in patients with HIT,
  due to its
• Oral route of administration
• Wide therapeutic window
• And potentially improved bleeding profile

Walenga JM, et al. Presented at ISTH 2007 in
Geneva, Switzerland, abstract P-M-648.