overview by c. michael gibson

Current Concepts In Therapeutic Angiogenesis

C. Michael Gibson M.S., M.D.

Scope of Coronary Artery Disease

• ~ 15 - 20 million Americans have a history of MI, angina, or both

• Cardiovascular disease is the number one cause of death in the US

• ~ 500,000 deaths per year• 1,500,000 new or recurrent MI’s per year

AHA Databank

• ~ 10 million Americans have angina• ~ 350,000 new cases of angina

diagnosed each year• ~ 1.5 million coronary angiograms

per year• ~ 500,000 PTCA per year• ~ 500,000 CABGs per year

AHA Databank

Scope of Coronary Artery Disease

Therapeutic Angiogenesis

Current Therapeutic OptionsMedical• Antianginals• Antiplatelet Agents• Lipid Lowering

Agents• Anticoagulants• Vasodilators

Interventional• PTCA• CABG• TMR/PMR• Cardiac

Transplantation• PVD: Amputation

New Therapeutic Option

Therapeutic Angiogenesis: DefinitionsAngiogenesis• The formation of new capillary blood vessels from

existing microvessels by sprouting, i.e. cellular outgrowth

Vasculogenesis• The formation of new blood vessels of all types from

blood islands, i.e. committed stem cells, in early embryogenesis

Growth Factor • Polypeptide which acts as a regulator of cellular

function, including proliferation, migration, differentiation, and survival/apoptosis

Angiogenic Growth Factors

• Basic fibroblast growth factor (bFGF)

• Acidic fibroblast growth factor (aFGF)

• Angiogenin• Angiotropin• Insulin-like growth factor• Interleukin-8• Platelet activating factor

(PAF)

J. Battegay: J. Mol Med; 1995

• Platelet-derived growth factor (PDGF)

• Proliferin• Transforming growth factor-• Transforming growth factor-• Tumor necrosis factor-• Vascular endothelial growth

factor (VEGF)

Basic Fibroblast Growth Factor (bFGF)

• 154 amino acids, MW 18 kD• Additional higher MW forms exist• Post-translational modification may yield a

shorter form• Present in almost all cells• Present from embryogenesis to adult cells• Released from extracellular sites by heparin

and various proteolytic enzymes

bFGF Receptors• The cell receptor is a transmembrane

tyrosine kinase• Found on numerous cell types• Receptor expression upregulated by

injury (PTCA & ischemia)• bFGF Binds to heparin which protects it

from degradation• Seperate binding sites for bFGF receptor

and heparin

Functions of Growth Factors

• Embryogenesis: Stimulates proliferation & differentiation of a variety of cells

• Wound Healing: Stimulates migration and proliferation of connective tissue

• Cytoprotection: CNS, vascular smooth muscle and endothelial cells

• Angiogenesis: Ischemic & Non-Ischemic• Active at 0.1 to 1.0 ng/ml

Augustin-Voss et al.

0

200

400

600

800

1000

1200

5 15 25 35 45

Control +bFGF

Passage Number

End

othe

lial C

ell M

igra

tion

(m

72

hour

s)

Bovine Endothelial Cell Migration

0

200

400

600

800

1000

1200

Control +bFGF

Prol

ifera

tion

% /

48 h

r

Augustin-Voss et al.

Impact of bFGF on Bovine Endothelial Cell Proliferation

Functions of bFGF

Non-ischemic Angiogenesis• Promotes endothelial cell migration and

tube formation• Stimulates the production of collagenases

and plasminogen activator necessary for basement membrane remodeling

M. Klagsbrun: Progress Growth Factor Research; 1989

Ischemic Angiogenesis

• Endogenous bFGF production in the presence of ischemia

• Impact of exogenous bFGF on ischemic tissues

Ischemic Angiogenesis

M. Cohen: J Mol Cell Cardiol; 1994

Longitudinal Changes in Myocardial Basic Fibroblast Growth Factor (FGF-2) Activity

Following Coronary Artery Ligation in the Dog

Michael V. Cohen et al.Albert Einstein College of Medicine

Demonstration of Endogenous Tissue Production of bFGF: Canine LAD Occlusion Model

Time Following Canine LAD Occlusion

Isch

emic

/Nor

mal

Myo

card

ial b

FGF

ratio

0

0.5

1

1.5

2

2.5

3

2 Hours 1 Week 2 Weeks 8 Weeks

*

*

Cohen et al: J Mol Cell Cardiol; 1994

Endogenous bFGF production assayed in ischemic and adjacent normal cardiac tissue bFGF production rose as early as 2 hours

Production of Growth Factors in Ischemia: Other Indirect Evidence

Fujita et al measured the bFGF levels in the pericardial fluid of patients undergoing open heart surgery for unstable angina (CABG) versus those undergoing surgery for non-ischemic causes

Elevated bFGF levels found in the pericardial fluid of patients with unstable angina

M. Fujita et al, Circulation; 1996

Baffour et al.• Rabbit model of hind limb ischemia (ligated main

arteries in staged procedure over 2 weeks)• Compared two weeks of IM bFGF to saline• Results:

• bFGF groups had angiographically improved collaterals

• bFGF groups had greater capillary density (per mm and per muscle fiber)

• bFGF groups had greater muscle viability

R. Baffour et al, J Vasc Surg; 1992

Ischemic Angiogenesis & Exogenous Growth Factors : Peripheral Models

Yang et al

• Rat model of hind limb ischemia• Compared one to four weeks of continuous intra-

arterial bFGF (1 g/day) to heparinized saline control• Demonstrated improvement in:

• Collateral blood flow by microspheres

• Capillary density

• Muscle performance by stimulated tension

H. Yang et al, Circ. Res 1996


0

10

20

30

40

50

60

Base 1 Week 2 Weeks 4 Weeks

ControlbFGF

Time Following Hind Limb Arterial Occlusion

Col

late

ral F

low

(ml /

min

/ 10

0g) * *

H. Yang et al, Circ. Res.; 1996


Uchida et al

• Occluded canine LAD model• Compared intrapericardial bFGF, heparin, or both to

saline control (drug given 30 minutes after occlusion)• Measured:

• Ejection fraction

• Capillary density

• Infarct size Y. Uchida et al, Am Heart J; 1995

Ischemic Angiogenesis & Exogenous Growth Factors : Cardiac Models

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Base 30 min. 1 month

SalineHeparinbFGFHep+bFGF

Time Following Arterial Occlusion

Ejec

tion

Frac

tion

**

Y. Uchida: Am Heart J; 1995


0

5

10

15

20

25

30

Saline Heparin bFGF Hep +bFGF

Infa

rcte

d W

eigh

t (%

of L

V)

‡

*

Y. Uchida et al, Am Heart J; 1995


0123456789

Saline Heparin bFGF Hep+bFGF

Noninfarct Zone

Infarct Zone

Cap

illar

y N

umbe

r per

200

m‡

Y. Uchida et al, Am Heart J; 1995

*


Ameroid constriction of porcine circumflex• Compared intrapericardial bFGF and/or heparin to

saline control• Measured:

• Angiographic collaterals

• Microsphere blood flow

• MRI Cardiac function

• MRI collateral flow

M. Simmons, personal communication; 1997


0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 Weeks 4 Weeks

SalineHeparinbFGF 30bFGF 200bFGF 2000

Circ

umfle

x F

low

(m

l / m

in /

g)*

**

Time Post Drug Administration



0

5

10

15

20

25

30

Saline Heparin bFGF 30

bFGF200

bFGF2000

Del

ayed

Con

tras

t Arr

ival

Ext

ent (

%)

*


**


Lazarous et al.

• Ameroid constriction of porcine circumflex

• Daily systemic bFGF (4 to 9 weeks) vs saline control

• Measured microsphere determinations of collateral blood flow

D. Lazarous et al, Circulation; 1995


Lazarous et al. Short Infusion Model

• Ameroid constriction of porcine circumflex

• Shorter duration of systemic bFGF (7 days) or VEGF to saline control

• Measured microsphere determinations of collateral blood flow



D. Lazarous: Circulation; 1996

Lazarous et al: Data Following 7 Day Infusions

Yanagisawa-Miwa et al.

• Acute occlusion of canine LAD

• Compared two bolus circumflex injections of bFGF vs saline

• Measured:• LV Function• Infarct size• Histologic assessment of collateral growth

A. Yanagisawa-Miwa et al, Science; 1992


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Baseline 30 Min. 1 Week

SalinebFGF

Ejec

tion

Frac

tion *

A. Yanagisawa-Miwa: Science; 1992

Time post Infarction


0

5

10

15

20

25

bFGF Saline

Infa

rct w

eigh

t / L

V w

eigh

t (%

) *



0

10

20

30

40

50

60

70

80

90

100C

apill

ary

Num

ber /

Uni

t Are

a*


0

2

4

6

8

10

12

14

16

Control bFGF

*

Art

erio

le N

umbe

r / U

nit A

rea


Control bFGF

Horrigan et al.

• Four hour balloon occlusion of canine LAD

• Compared two bolus LM injections of bFGF or vehicle

• Measured:

• Infarct size

• Histologic assessment of collateral growth

M. Horrigan et al, Circulation; 1996


0

5

10

15

20

25

30

Vehicle bFGF

Infa

rct S

ize

(% a

rea

at ri

sk)

*

M. Horrigan et al, Circulation; 1996


Chiron Study

Multi-Center, Single-Blind, Dose Escalation, Safety and Tolerability Study

of Recombinant Fibroblast Growth Factor-2 (rFGF-2) in Subjects with

Advanced Coronary Artery Disease

Study Objectives

• Evaluate safety, tolerability and pharmacokinetics of short-term (20 min) intracoronary (IC) and intravenous (IV) single infusions of ascending doses of rFGF-2

• Determine maximum tolerated IC and IV doses• Measure preliminary efficacy data using

nuclear stress imaging and cardiac MRI

• Study Agent• Recombinant protein produced in yeast• Differs from native human bFGF by only two amino

acids• Essentially identical angiogenic properties

• Enrollment• Screening physical exam and labs• Exercise or dipyridamole stress test with dual isotope

imaging• Cardiac MRI with cardiac function and collateral flow

determinations• Ophthalmologic exam• Quality of Life questionnaire

Study Design

Inclusion Criteria

• Severe CAD with inducible ischemia on stress test

• No optimal revascularization option• Normal routine laboratory screening• Willingness and ability to complete all

components of the study and its follow-up• Signed informed consent

• Class IV CHF or EF < 20%• MI < 3 months• New or unstable angina < 3 wks• CABG < 6 months• PTCA or TMR < 6 months• Significant arrhythmias• Pacemaker or AICD• LBBB

• Severe valvular heart disease

• Restrictive or hypertrophic cardiomyopathy

• Known AVMs• TIA or CVA < 6 mths• DM with end-organ

damage• Cr Cl < 80 ml/min or

proteinuria• Cancer within 10 years

Exclusion Criteria

Drug Administration• Intracoronary Infusion

• Left and Right heart catheterizations• 10 minute infusions of bFGF into the RCA and

LM (or the major supplying bypass graft)• Intravenous Infusion

• Left heart catheterization (if not done within 6 mths)

• 10 minute infusion into a peripheral vein

Follow-Up Protocol

• Clinic visits with routine blood tests at day 6, day 14 and at 1, 2, 6 and 12 months

• Repeat stress test and MRI scans at 1 month

• Subsequent exams only if indicated

• Repeat Eye exams at 2 and 12 months

• Repeat Quality of Life questionnaire at 2 months

overview by c. michael gibson

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