1. Are all Xa Inhibitors the Same. Alexander G. G
Are all Xa Inhibitors the Same? Alexander G. G. Turpie, MD Professor of Medicine McMaster University Hamilton, Ontario, Canada

2. Antithrombotics That Have Changed Clinical Practice
Anticoagulants
Low-molecular-weight heparin
Antiplatelet Drugs
Thienopyridines
Glycoprotein IIb/IIIa Inhibitors

3. Low Molecular Weight Heparins
Nadroparin -Fraxiparine
Enoxaparin -Lovenox
COONa O
CaO3SO O O
Saccharide chain
Saccharide chain
NHSO3Ca OH
OSO2ONa
OR1
Dalteparin -Fragmin H R2
R1 = H or SO3Na R2 = COONa
CHOR2
Saccharide chain O
CH2OH HO OH O
OR1

4. Low-Molecular-Weight Heparins
Potential Advantages:
Lack of binding to plasma proteins and endothelium
Good bioavailability
Stable dose response
Long half-life
Resistance does not develop

5. Low Molecular Weight Heparin
Venous Thromboembolism
- prophylaxis
- treatment
Ischaemic heart disease
unstable angina
acute MI
coronary stenting
Cerebrovascular disease
ischaemic stroke
embolic stroke
Peripheral vascular disease
reconstructive surgery

6. New anticoagulants ORAL PARENTERAL TF/VIIa TFPI (tifacogin) TTP889 XIX
APC (drotrecogin alfa)
sTM (ART-123)
IXa
VIIIa
Rivaroxaban Apixaban LY YM150
DU-176b PRT Va AT Xa
Fondaparinux Idraparinux
There are many targets for novel anticoagulants in the coagulation pathway:
Tissue factor pathway inhibitor (TFPI) bound to Factor Xa inactivates the tissue factor (TF)–Factor VIIa complex, preventing initiation of coagulation
Activated protein C (APC) degrades Factors Va and VIIIa, and thrombomodulin (soluble; sTM) converts thrombin (Factor IIa) from a procoagulant to a potent activator of protein C
Fondaparinux and idraparinux indirectly inhibit Factor Xa, requiring antithrombin (AT) as a cofactor
Direct (AT-independent) inhibitors of Factor Xa include rivaroxaban (BAY 59­7939), LY517717, YM150 and DU-176b (all orally available), and DX-9065a (intravenous)
Oral, direct thrombin inhibitors include ximelagatran (now withdrawn) and dabigatran
Weitz JI & Bates SM. New anticoagulants. J Thromb Haemost 2005;3:1843–1853 II
DX-9065a Otamixaban
Ximelagatran Dabigatran
IIa
Fibrinogen
Fibrin
Adapted from Weitz & Bates, J Thromb Haemost 2005

7. Factor Xa inhibitors FXa may be a better target than thrombin
Has few functions outside coagulation (compared with thrombin)
Has a wider therapeutic window than thrombin (separation of efficacy and bleeding), in vitro
Thrombin inhibitors are associated with rebound thrombin generation – no evidence with FXa inhibitors
Efficacy of heparin-based anticoagulants improves as selectivity for FXa increases: UFH < LMWH < fondaparinux

8. Factor Xa Inhibitors
Indirect
Direct

9. Fondaparinux: First in New Class of Synthetic Inhibitors of FactorXa
Total Chemical Synthesis
Single chemical entity
Highly selective for its target
No risk of pathogen contamination
Batch-to-batch consistency
Herbert JM et al. Cardiovasc Drug Rev. 1997;15:1.
van Boeckel CAA et al. Angew Chem, Int Ed Engl. 1993;32:1671.

10. Fondaparinux: Targeted Mechanism of Action
Intrinsic
pathway
Extrinsic pathway
Antithrombin AT AT AT Xa Xa
Fondaparinux II
IIa
Fibrinogen
Fibrin clot
Turpie AGG et al. N Engl J Med. 2001;344:619.

11. Overall Efficacy Fondaparinux vs Enoxaparin
Fondaparinux better
Enoxaparin better
Exact 95% CI
Ephesus
N = 1817
[72.9; 37.5]
58.5%
Pentathlon 2000
N = 1584
[52.2; 7.6]
28.1%
Penthifra
N = 1250
61.6%
[73.4; 45.0]
Pentamaks
N = 724
63.1%
[75.5; 44.8]
Overall Odds Reduction
[63.2; 45.8]
55.3%
P =
% odds reduction
-80
-60
-40
-20
-100 20 40 60 80
100
Overall odds reduction for proximal DVT = 57.4% [CI: ]; p = 10 x -6
Turpie AGG, et al. Arch Intern Med. 2002;162:

12. OASIS-5 – efficacy and safety at day 9
Death, MI, refractory ischaemia
Major bleeding
Primary efficacy endpoint: 5.8% (fondaparinux) vs 5.7% (enoxaparin)
Major bleeding: 2.2% (fondaparinux) vs 4.1% (enoxaparin) 1 2 3 4 5 6 7 8 9
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Days
Cumulative hazard
Enoxaparin
Fondaparinux
HR 1.01
95% CI 0.90, 1.13 1 2 3 4 5 6 7 8 9
0.00
0.01
0.02
0.03
0.04
Days
Cumulative hazard
Enoxaparin
HR 0.52
95% CI 0.44, 0.61
p<0.001
Fondaparinux
OASIS-5 Trial Group NEJM Available at

13. OASIS-5 – mortality at 6 months
Days
Cumulative hazard
0.0
0.02
0.04
0.06 20 40 60 80
100
120
140
160
180
Enoxaparin
Fondaparinux
HR 0.89
95% CI 0.80, 1.00 p=0.05
Comparison of Fondaparinux and Enoxaparin in Acute Coronary Syndromes. N Engl J Med
2006
OASIS-5 Trial Group NEJM Available at

14. OASIS-6 – death at study end (3–6 months)
Days
Cumulative hazard
0.0
0.02
0.04
0.06
0.08
0.10
0.12 18 36 54 72 90
108
126
144
162
180
UFH/placebo
Fondaparinux
HR 0.88
95% CI 0.79, 0.99 p=0.029
OASIS-6 Trial Group JAMA Available at

15. Direct FactorXa Inhibitors

16. Oral Factor Xa inhibitors Clinical development
Rivaroxaban (JNJ/Bayer) Phase IIb
Phase III
Apixaban (BMS) Phase III
YM150 (Astellas) Phase IIb
DU-176b (Daiichi) Phase IIb
LY (Lilly) Phase IIb
(GSK) Phase I/II
PRT054021(Portola) Phase II

17. Direct Factor Xa inhibition
XIIa
Tissue factor ×
XIa
VIIa
IXa Xa
Rivaroxaban
Apixaban
DU-176b
YM150
LY517717
PRT
Factor II (prothrombin)
Fibrinogen
Fibrin clot

18. Direct Factor Xa Inhibitors
FXa
Direct FXa inhibitors
eg Rivaroxaban
FXa in the
prothrombinase
complex
Direct Factor Xa inhibitors can inhibit Factor Xa within the prothrombinase complex

19. Rivaroxaban: a direct, competitive inhibitor of Factor Xa activity
In vitro kinetic analysis
600
Rivaroxaban 0.9 nM
500
Rivaroxaban 0.7 nM
Rivaroxaban 0.5 nM
Rivaroxaban 0.2 nM
400
Control
1/OD/minute
300
200
This kinetic analysis clearly shows competitive inhibition of Factor Xa activity by BAY 59­7939, thus indicating it is a competitive, active-site-directed Factor Xa inhibitor
This Lineweaver–Burk plot shows the activity of 0.5 nM Factor Xa against a chromogenic substrate in the absence or presence of 0.2, 0.5, 0.7, or 0.9 nM Rivaroxaban, in vitro, in the absence of antithrombin
Rivaroxaban potently inhibited purified human Factor Xa activity in the absence of antithrombin, demonstrating that Rivaroxaban is a direct Factor Xa inhibitor
100
0.000
0.005
0.010
0.015
0.020
1/chromogenic peptide (µM)
Perzborn et al., J Thromb Haemost 2005
Perzborn E, Strassburger J, Wilmen A et al. In vitro and in vivo studies of the novel antithrombotic agent Rivaroxaban—an oral, direct Factor Xa inhibitor. J Thromb Haemost 2005;3:514–521

20. Rivaroxaban inhibits free Factor Xa, prothrombinase-bound FactorXa, and fibrin-bound Factor Xa activity
In vitro studies
100 80 60
Inhibition of Factor Xa activity (%) 40
Rivaroxaban not only potently inhibits purified, human, free Factor Xa
activity in a concentration-dependent manner (Ki = 0.4 nM), but also
inhibits prothrombinase activity (IC nM)1 and fibrin-bound Factor Xa
(IC50 75 nM).2
The inhibitory effect of Rivaroxaban was measured as follows:
Purified, free Factor Xa activity: using a chromogenic substrate of Factor Xa (in vitro)1
Prothrombinase activity: measuring thrombin generation in a reconstituted prothrombinase complex using prothrombin as a substrate1
Fibrin-bound Factor Xa activity: by determining prothrombin activation in fibrinogen- and Factor Xa-deficient plasma incubated with clots preformed in human plasma2
1. Perzborn E et al. In vitro and in vivo studies of the novel antithrombotic agent Rivaroxaban—an oral, direct Factor Xa inhibitor. J Thromb Haemost 2005;3:514–521
2. Depasse F et al. Effect of Rivaroxaban – a novel, oral, direct Factor Xa inhibitor – on clot-bound Factor Xa activity in vitro. J Thromb Haemost 2005;3(S1):Abstract Poster presentation at the International Society on Thrombosis and Haemostasis XXth Congress, Sydney, Australia, August 6–12, 2005 20
Free Factor Xa1
Prothrombinase activity1
Fibrin-bound Factor Xa2
0.01
0.1 1 10
100
1000
Rivaroxaban (nM)
1Perzborn et al., J Thromb Haemost 2005; 2Depasse et al., ISTH 2005

21. Apixaban A highly potent, oral, direct FXa inhibitor (Ki 0.08 nM)
Follow-up to razaxaban (development halted due to bleeding concerns)
Phase II study for VTE prevention after TKR: completed
Double-blind; dose-ranging; three od and three bid apixaban doses; comparator enoxaparin and warfarin; target enrolment n=1202
Phase II pilot study for VTE prevention in patients with advanced metastatic cancer: ongoing

22. Apixaban
The Botticelli-DVT study for treatment of acute symptomatic DVT: ongoing
– efficacy and safety of apixaban 5 mg bid, 10 mg bid and 20 mg od; comparators LMWH or fondaparinux followed by VKA
Phase II study in patients with recent UA or MI: ongoing
Placebo-controlled; double-blind; target enrolment n=1800
AF Study

23. Rivaroxaban Human Factor Xa/rivaroxaban complexS4 S1
Rivaroxaban
This slide shows the X-ray crystal structure of rivaroxaban in complex with human Factor Xa, demonstrating the direct binding of rivaroxaban to human Factor Xa
Supported by two hydrogen bonds, the (S)-oxazolidinone core of rivaroxaban provides the L-shape needed for binding to Factor Xa. It serves as a central template for directing the substituents into the S1 and S4 subsites
Perzborn E et al. In vitro and in vivo studies of the novel antithrombotic agent
BAY —an oral, direct Factor Xa inhibitor. J Thromb Haemost 2005;3:514–521
Roehrig S et al. Discovery of the novel antithrombotic agent 5-chloro-N-({(5S)-2-oxo-3-[4-(3-
oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl}methyl)thiophene-2-carboxamide
(BAY ): An oral, direct Factor Xa inhibitor. J Med Chem 2005;48:5900–5908
Rivaroxaban is an oral, direct Factor Xa inhibitor, with high selectivity for Factor Xa (Ki 0.4±0.02 nM)
IC50 for Factor VIIa, Factor XIa, thrombin, activated protein C, plasmin, urokinase, trypsin: >20,000 nM
Roehrig et al., J Med Chem 2005; Perzborn et al., J Thromb Haemost 2005

24. Rivaroxaban bid (THR/TKR pooled):10 20 30 40 50 60
Enoxaparin
DVT, PE, and all-cause mortality
Major bleeding
Estimated incidence rate* (%)
Rivaroxaban (mg total daily dose) 5
Efficacy: p=0.39
The highlighted section demonstrates the wide therapeutic window of
rivaroxaban – where the observed efficacy and safety of rivaroxaban were
similar to those of enoxaparin.
Turpie AGG et al. Thromboprophylaxis after orthopaedic surgery with an oral, direct Factor
Xa inhibitor: pooled results of two phase IIb clinical trials. Blood 2005;106(11):Abstract 277.
Oral presentation at the 47th American Society of Hematology meeting, Atlanta, GA, 9–13
December 2005
Safety: p<0.0001
*Estimated rates calculated by logistic regression adjusted for study, age, and gender

25. Rivaroxaban efficacy and safety after THR with od dosing5 10 20 40
Enoxaparin 30
Incidence – efficacy (%)
Incidence – safety (%)
Total daily dose (mg) of rivaroxaban
DVT, PE, and all-cause mortality
Major, post-operative bleeding
The graph shows the dose–response relationships between rivaroxaban and
the primary efficacy and safety endpoints estimated using logistic regression
with doses of rivaroxaban as a covariate.
When efficacy and safety are considered together, this study suggests that the optimum dose of rivaroxaban is 10 mg once daily
There was no significant dose trend for efficacy (p=0.0852)
There was a significant dose trend for major bleeding (p=0.0072)
Eriksson BI et al. Prevention of venous thromboembolism after total hip replacement with
once-daily BAY – an oral, direct Factor Xa inhibitor. Oral presentation at the
American Society of Hematology Annual Meeting, Atlanta, GA, 9–13 December 2005
Total rivaroxaban daily doses of 5–20 mg had similar efficacy and safety to enoxaparin when given twice daily
Rivaroxaban 10 mg once daily appears to be the optimum dose
Eriksson et al. ASH 2005

26. RECORD – REgulation of Coagulation in major Orthopaedic surgery reducing the Risk of DVT and PE
Rivaroxaban 10 mg od will be compared with enoxaparin in over 10,000 patients worldwide
RECORD 1: THR, 5 weeks therapy
RECORD 2: THR, 5 weeks vs 10–14 days enoxaparin
RECORD 3: TKR, 10–14 days therapy
RECORD 4: TKR, 10–14 days therapy

27. ODIXa-DVT – dose–response relationship for efficacy
Primary efficacy outcome 80 70 60 50 40 30 20 10
Rivaroxaban total daily dose (mg)
Enox+VKA
bid rivaroxaban doses
od rivaroxaban dose
Thrombus regression without recurrent VTE (%)
There was no significant dose–response relationship between rivaroxaban (bid doses only) and the primary efficacy outcome (p=0.67).
≥4-point improvement in thrombus burden by CCUS without recurrent VTE Dose–response relationship: p=0.67 Per-protocol population (n=528)

28. EINSTEIN-DVT – dose–response relationship for efficacy20
Recurrent DVT or PE (fatal or non-fatal) and deterioration in CUS or PLS 18 16 14 12
Rate of deterioration (%) 10 8 6 4
There was no dose–response relationship between rivaroxaban and the primary efficacy outcome (p=0.86). 2 10 20 30 40
LMWH/heparin +VKA
Rivaroxaban total daily dose (mg)
Dose–response relationship: p=0.86 Per-protocol population (n=449)

29. Rivaroxaban-Clinical Studies
- VTE Treatnent
- Atrial Fibrillation
ACS treatment

30. Factor Xa inhibitors in development
Indication
VTE prevention*
VTE treatment
Stroke prevention in patients with AF
Other?
Idraparinux –
Phase III results expected soon
Phase III halted
Rivaroxaban
Phase III
ACS ongoing
LY517717
Phase IIb completed
YM150
Phase IIa completed
Planned
DU-176b
ACS planned
Apixaban
Phase IIb completed; planned in cancer patients
Phase II underway
Post-ACS planned
PRT
Phase II planned
Secondary prevention of stroke and MI planned
*Prevention of VTE after major orthopaedic surgery, unless indicated

31. New anticoagulants ORAL PARENTERAL TF/VIIa TFPI (tifacogin) TTP889 XIX
APC (drotrecogin alfa)
sTM (ART-123)
IXa
VIIIa
Rivaroxaban Apixaban LY YM150
DU-176b PRT Va AT Xa
Fondaparinux Idraparinux
There are many targets for novel anticoagulants in the coagulation pathway:
Tissue factor pathway inhibitor (TFPI) bound to Factor Xa inactivates the tissue factor (TF)–Factor VIIa complex, preventing initiation of coagulation
Activated protein C (APC) degrades Factors Va and VIIIa, and thrombomodulin (soluble; sTM) converts thrombin (Factor IIa) from a procoagulant to a potent activator of protein C
Fondaparinux and idraparinux indirectly inhibit Factor Xa, requiring antithrombin (AT) as a cofactor
Direct (AT-independent) inhibitors of Factor Xa include rivaroxaban (BAY 59­7939), LY517717, YM150 and DU-176b (all orally available), and DX-9065a (intravenous)
Oral, direct thrombin inhibitors include ximelagatran (now withdrawn) and dabigatran
Weitz JI & Bates SM. New anticoagulants. J Thromb Haemost 2005;3:1843–1853 II
DX-9065a Otamixaban
Ximelagatran Dabigatran
IIa
Fibrinogen
Fibrin
Adapted from Weitz & Bates, J Thromb Haemost 2005

32. Antithrombotic Therapy
2007

33. Question
&
Answer