MECHANISM BASED ADVERSE CARDIOVASCULAR EVENTS AND SPECIFIC

INHIBITORS OF COX-2

Garret A. FitzGerald M.D.Robinette Professor of Cardiovascular Medicine

Elmer Bobst Professor of PharmacologyUniversity of Pennsylvania

McAdam et al. Proc Natl Acad Sci USA. 1999;96:272.

*20 M arachdonic acid as agonist.

Inh

ibit

ion

of

pla

tele

t ag

gre

gat

ion

(% c

on

tro

l)

0

100

Placebo

20

IbuprofenCelecoxib (mg)

100 400 800

40

60

80

10

30

50

70

90

P<0.01 vs placebo

Coxibs are not platelet inhibitors

COX in Human Platelets: Western Blot Analysis

AnitbodiesCOX-1: monoclonalantibody raised againstpurified ram COXCOX-2: monoclonalantibody raised against theCOOH peptide of humanCOX-2

COX-1

Protein (µg) 10 50 100 30 3010 50 100 10 50 100

45 –

66 –

97 –

117 –

COX-1

EC + PMA

COX-2 COX-2(max exposure)

CO

X-2

CO

X-1

Platelets

COX-2

COX-1

Habib A 2000

Inhibition of prostacyclin synthesis by celecoxib and rofecoxib

* PGI-M = 2,3-dinor-6-keto-PGF1; † P<0.01 vs Placebo; ‡ P<0.05 vs Placebo.

0

40

80

120

160

200

Placebo(n=7)

Celecoxib 400 mg(n=7)

Ibuprofen 800 mg(n=7)

Mea

n u

rin

ary

PG

I-M

* ±

SE

(p

g/m

g c

reat

inin

e)

†

‡

Placebo(n=12)

Rofecoxib50 mg qd

(n=12)

Indomethacin50 mg tid

(n=10)

†

†

0

40

80

120

160

200

McAdam et al. Proc Natl Acad Sci USA. 1999;96:272; Catella-Lawson et al. J Pharmacol Exp Ther. 1999;289:735.

Celecoxib 800 mg(n=7)

†

REGULATED EXPRESSION OF COX-2 IN ENDOTHELIUM BY LAMINAR SHEAR

COX-2

COX-1

Topper et al. Proc Natl Acad Sci USA. 1996

Co

ntr

ol

LS

S 1

hr

LS

S 6

hr

Co

ntr

ol

TS

S 1

hr

TS

S 6

hr

Co

ntr

ol

IL-1

1 h

r

IL-1

6 h

r

PGI2 modulates the cardiovascular response to TxA2 in vivo

Cheng et al Science. 296: 539 – 541, 2002.

Endothelial COX-2 dependent PGI2 modulates thrombosis induced in vivo by photochemical injury to the vasculature

0

25

50

75

100 PGHS1 KOPGHS1Neo/Neo

WT(10)

(12)

(10)

Co

mp

lete

oc

clu

sio

n t

ime

(m

in)

#

50 mg/kg 100 mg/kg0

25

50

75

100PGHS1 KOPGHS1Neo/Neo

WT

(8) (7)

(12)

(4) (3)

(5)

Re

sis

tan

ce

to

AA

-In

du

ce

dT

hro

mb

os

is (

% S

urv

iva

l)

**

Yu et al JCI (in press) 2005

DELETION OR 98% KNOCK DOWN OF COX-1 PROTECTS AGAINST THROMBOSIS

Parecoxib/valdecoxib and combined coronary

and cerebrovascular events

• Study Valde Plcb Valde Plcb RR 95%CI• =========================================• Ott 311 151 14 2 3.40 0.82-13.98• 2nd CABG 1088 548 17 3 2.85 0.81-10.02 • Meta-analytic RR 3.08 1.20-7.87

• p-value 0.019• p-value heterogeneity 0.86

Furberg, Psaty and FitzGerald Circ 111;249,2005

A. B.

Fig. 1: Ventilation-Perfusion Scan (VQ Scan). A. After inhalation of 20.1mCi of Xenon-133 gas, scintigraphic images were obtained in the posterior projection showing uniform ventilation to lungs. B. After IV injection of 4.1mCi of Tc-99m-labeled MAA, scintigraphic images were obtained in the posterior projection showing decreased activity in the following regions: apical segment of right upper lobe, anterior segment of right upper lobe, superior segment of right lower lobe, posterior basal segment of right lower lobe, anteromedial basal segment of left lower lobe, and lateral basal segment of left lower lobe.

VALDECOXIB AND ENVIRONMENTAL PREDISPOSTION TO THROMBOSIS

MECHANISM BASED CARDIOVASCULAR HAZARD - 1

• HEMODYNAMIC INDUCTION OF ENDOTHELIAL COX-2 DERIVED PROSTACYCLIN

• PROSTACYCLIN CONSTRAINS PLATELET ACTIVATION AND THROMBOGENESIS IN VIVO

• SUPPRESSION OF PROSTACYCLIN DOES NOT CAUSE SPONTANEOUS THROMBOSIS , BUT AUGMENTS THE RESPONSE TO THROMBOGENIC STIMULI IN VIVO

• HAZARD FROM COXIBS PARTICULARLY IN THOSE OTHERWISE PREDSIPOSED TO THROMBOSIS

• HAZARD ATTENUATED BY >98% INHIBITION OF COX-1

Breyer and colleagues 2002

100

110

120

130

140

150

160

170

Normal salt Low salt High Salt

SB

P (

mm

Hg

)

**

† ‡

§

*

SALT SENSITIVE HYPERTENSION IN IPKOs

Francois et al 2004

MECHANISM BASED CARDIOVASCULAR HAZARD -2

• SUPPRESSION OF COX-2 DERIVED PGI2 AND PGE2 INCREASES BP AND AUGMENTS THE RESPONSE TO HYPERTENSIVE STIMULI

• DELETION OR INHIBITION OF COX-1 DEPRESSES THE RESPONSE TO VASOSCONSTRICTORS IN VIVO

• HYPERTENSION ON NSAIDS RELATES TO INHIBITION OF COX-2 AND THE SELECTIVITY WITH WHICH IT IS ATTAINED

Narumiya, JCI; 2004.

TxA2 and PGI2 have opposing effects on the initiation of Atherosclerosis

DELETION OF THE IP REDUCES MARKEDLY THE ANTIATHEROSCLEROTIC EFFECT OF ESTROGEN IN VIVO

Egan et al Science 306; 1954- 1957, 2004

MECHANISM BASED CARDIOVASCULAR HAZARD -3

• INITIATION AND ACCELERATION OF EARLY ATHEROGENESIS BY DELETION OF THE IP

• FOSTERS PLATELET AND NEUTROOPHIL ACTIVATION AND VASCULAR INTERATIONS

• REMOVES CONSTRAINT ON ATTENDANT OXIDANT STRESS.

• HYPERTENSION ALSO ACCELERATES ATHEROGENESIS

• PREDISPOSITION TO ATHEROSCLEROSIS AND HYPERTENSION ATTENUATED BY COINCIDENT INHIBITION OF COX-1

Confirmed Thrombotic EndpointKaplan-Meier Estimates (95% CI)

RR(95% CI): 1.96 (1.20, 3.19)*

* p<0.05

Patients at RiskPlacebo

Rofecoxib 25 mg1299 1192 1148 1079 1039 1002 4701287 1123 1050 986 935 898 411

0 6 12 18 24 30 36

Month

0

2

4

6

8C

umul

ativ

e In

cide

nce(

%)

with

95%

CI

PlaceboRofecoxib 25mg

COX-2COX-2

PGIPGI22

COX-1 COX-1

BPBP

TXATXA22

COX-1COX-1

COX-2 COX-2

Cardiac Cardiac FibrosisFibrosis

HIGHHIGH

Detection of a Cardiovascular Signal

NNT &/or Trial DurationNNT &/or Trial Duration

INTERINTER

LOWLOW

CABGCABG

? RA? RA

OA /OA /?? PolypsPolyps

LOWLOW

INTERINTER

HIGHHIGH

Intrinsic Intrinsic CV RiskCV Risk

Drug Exposure Drug Exposure and Selectivity and Selectivity in vivoin vivo

VARIATION WITHIN A CLASS EFFECT

• Underlying substrate of cardiovascular risk

• Dose, duration of dosing

• Duration of drug action

• Volume of distribution?

• Concomitant therapy – eg ASA

WHAT ABOUT

TRADITIONAL NSAIDs?

Effects of Aspirin or Ibuprofen Alone on COX-1

Ibuprofen 400mg tid x6 days

Aspirin 81mg qd x6 daysHOURS

2 6 240

25

50

75

100

0

25

50

75

100

HOURS2 6 24

PLATELET AGGREGATION

% inhibition

SERUM THROMBOXANE

Catella et al NEJM 345:1809 -1817,2001

RR=1.04 [1.00-1.08

RR=0.88 [0.8-0.95]

RR = 1.03 [.96-1.1]

NSAIDs

NAPROXEN

IBUPROFEN

NAPROXEN : HALF AS GOOD AS ASPIRIN?

RR OF MYOCARDIAL INFARCTION

Garcia Rodriguez 2004

The VIGOR Study

Event Rofecoxib Naproxen

Stroke 9 (0.2%) 8 (0.2%)

Myocardial Infarction 20 (0.5%) 4 (0.1%)

*

Differential Recovery From Steady-State Inhibition Of Platelet COX-1 By Low-Dose ASA and

Naproxen

ASA = aspirin; COX = cyclooxygenase.

Capone et al 2003

6065707580859095

100

PlateletCOX-1

%Inhibition

P <.01

Naproxen (N = 9)ASA (N = 8)

P <.01

Time (hours after last administration)

P =.074

1 3 12 24

Human Whole Blood COX 1/COX 2 Assays

Updated from FitzGerald & Patrono, N Engl J Med 2001; 345:433-442

Indomethacin

Naproxen

Ibuprofen

6-MNA

Acetaminophen

Diclofenac

CelecoxibNimesulideMeloxicam

Rofecoxib

Valdecoxib

Etoricoxib

Lumiracoxib

0,01COX-1 IC50

M

COX-2 IC50 M

0,01

0,1

1

10

100

0,1 1 10 100

Diclo COX-2

Diclo COX-1

0

20

40

60

80

100 Cele COX-1Cele COX-2

% Inhibition

Diclofenac = Celebrex in whole human blood in vitro

Patrignani et al 2005

Aspirin / Ibuprofen vs Aspirin / Diclofenac

*

0

25

50

75

100

HOURS

2 6 12 24

Aspirin 81mg qd /Diclofenac-DR 75mg bid

Aspirin 81mg qd / Ibuprofen 400mg tid

HOURS

2 6 12 24

* *

0

25

50

75

100

PLATELET AGGREGATION

% inhibition

SERUM THROMBOXANE

Diclofenac = Celecoxib

• Same selectivity in whole blood in vitro

• No pharmacodynamic interaction with asa

• No clinical asa interaction in MI protection

• Superimposition of GI and CV events in CLASS

• EDGE and MEDAL – comparisons within the class

tNSAIDs and CV risk

• Evidence that naproxen achieves sustained platelet inhibition in some individuals. A “dilute” aspirin?

• Evidence that diclofenac is a COX-2 inhibitor like celebrex ( with hepatic AEs )

• Evidence that ibuprofen might undermine benefit from asa

• No rationale for lumping diclofenac and ibuprofen as “non-naproxen NSAIDs”

DEAD DRAGONS

• It’s all naproxen

• Hypertension is a different mechanism

• Off target fantasies

• It’s just a matter of reducing the dose

• Time for a study of coxibs in ACS

Lumen

Laminin Smooth muscle cell actin

TP antagonism with COX-2 inhibition results in plaque destabilizationTP antagonism with COX-2 inhibition results in plaque destabilization

Vehicle

COX 2

TP

COX 2 / TP

Egan et al Circulation 111;334-342,2005

THE WAY FORWARD?

• Exclude patients at high intrinsic risk of thrombosis from exposure to selective inhibitors of COX-2

• Dose reduction alone does not protect from individual hazard due to variability in dose – response

• Subject drugs already approved to the same requirements for extended dosing as drugs yet to be approved

• Restrict duration of dosing until the parameters of safety for extended dosing are established

Interindividual variability in the responses to coxibs

ex vivo COX-2 assay ex vivo COX-1 assay

urinary 2,3 dinor-6-keto PGF1a urinary 11-dehydro TxB2

Inhi

bitio

n se

rum

PG

E2

(pos

t dos

e / p

re d

ose

ratio

)

0.1

1

5

placebo rofecoxib celecoxib

Inhi

bitio

n se

rum

TxB

2

(pos

t dos

e / p

re d

ose

ratio

)

placebo rofecoxib celecoxib

urin

ary

PG

I-M

(pg/

mg

crea

tinin

e)

10

50

100

200

300

placebo rofecoxib celecoxib

50

100

500

1000

2000

placebo rofecoxib celecoxib

urin

ary

TxM

(pg/

mg

crea

tinin

e)

Fig. 3

A B

DC

0.1

1

5

PERSONALIZED MEDICINE AND THE FUTURE OF THE COXIBS

• Restrict to individuals intolerant of tNSAIDs plus PPIs

• Determine whether risk transformation occurs during chronic dosing

• Combine physiologic, biochemical and genomic variables in discriminant analysis of evolving risk in existing trials – APPROVe, APC etc

• Validate prospectively in studies of extended dosing

CONCLUSIONS• Selective inhibitors of COX-2 depress PGI2 without

concomitant inhibition of TxA2

• This can result in an augmented response to thrombotic and hypertensive stimuli and acceleration of atherogenesis in mice

• An increase in MI and/or stroke has been seen in 5 placebo controlled trials with 3 structurally distinct COX-2 inhibitors

• Hazard would be expected to relate to drug selectivity, dose and duration of exposure and to interindividual differences in drug response