This document discusses requirements for drug-eluting stents including mechanical properties, stent coating, and drug factors. It compares vascular remodeling and healing of the Coracto DES to first and second generation DES in a rabbit model. Key findings include: 1) Thinner stent struts are associated with improved clinical outcomes compared to thicker struts. The Coracto DES has the thinnest struts reported at 80 microns. 2) Incomplete endothelialization is a major drawback of first generation DES leading to late stent thrombosis. The degree of strut coverage correlates with endothelialization and thrombosis risk. 3) An ideal polymer coating for DES would be inert and biocompatible, precisely

1. Comparing Vascular Remodeling and
Healing of the Coracto DES to 1st and 2nd
Generation DES in a Rabbit Preclinical
Model
Renu Virmani, MD
CVPath Institute
19 Firstfield Road
Gaithersburg, MD USA
www.cvpath.org

2. Requirements of a Drug Eluting Stent
Mechanical Properties Stent Coating Drug
-Design -Polymer type -Drug type/load
-Material -Coating thickness -Elution Profile
-Strut geometry -Biocompatibility -Toxicity
Healing rates Inflammation Safety

3. Stenting of Human Coronary Arteries
Drug Eluting versus Bare Metal Stents
In Stent Re -stenosis [%]
Bare Metal Stent (~15 months) 30
20
10
0
Drug Eluting Stent (~15 months) BMS DES
Neointimal Thickness
2
[mm]
1
0
BMS DES

4. Incomplete Healing
A Current Major Drawback of DES
Late Stent Thrombosis (LST)
BMS DES
Thr
100
90
Mean % Endothelialization
80
70
60
50
40
30
20
DES
10 BMS
0
1 2 4 5 6 9 19 20 24 50
Months
Joner M & Finn AV. J Am Coll Cardiol. 2006;48(1):193-202. Langerqvist et al. Circulation Cardiovasc Interv 2009

5. Pathological Correlates of Late DES Thrombosis: Strut
Coverage as a Marker of Endothelialization
> 30 days implants > 30 days implants
uncovered covered
uncovered covered
80
n=28 p<0.0001
70
% Uncovered struts
60
Thrombus
50
No Thrombus
40
30
n=34
20
10
0
% Uncovered Struts/section
Finn AV, et al., Circulation 2007;115:2435-2441

6. Role of Endothelial Cells
Anti-thrombotic activities
-NO production through eNOS - Thrombomodulin
- Prostacylin (PGI2) - Tissue Plasminogen activator
-Heparin sulphate or chondroitine sulphate - Tissue factor pathway inhibitor

7. Endothelial Cell Intercellular Junctions
Tight junction Adherens junction
VEGF
Ang-1 Ang-2
PECAM PECAM PECAM Endothelial cells
Tie-1 Tie-2 VEGFR2
Claudin VE-cad β-cat
GAP junction JAM apoptosis
Integrin Connexin Integrin β-cat
αvβ5 αvβ3 Akt PI3K
VT
FN
PDGF-BB PDGF-BB
PDGFR-β SMC recruitment:
PDGFR-β Ang-1, PDGF,
uPA TGF-b, PIGF
Smooth Muscle Cell Smooth Muscle Cell
Tight Junctions: GAP junctions Adherens Junctions:
Occludin Connexins VE-Cadherin
Claudin
JAM

8. Impact of Stent Design on Healing
Mechanical Properties
-Strut Patterns
-Strut Thickness
-Mechanical Integrity: Fractures
Healing rates

9. Strut Thickness
CYPHER® TAXUS® Express ENDEAVOR™ XIENCE V™
Strut Thickness: Strut Thickness: Strut Thickness: Strut Thickness:
140 µm 132 µm 91 µm 81 µm

10. Incidence of angiographic and clinical restenosis
Thin-strut (50μm) vs. Thick-strut (140μm)
Total of 651 patients: 326 – thin strut, 325 – thick strut
P=0.005
30 Thin-strut
Thick-strut
incidence (%)
25
(25.3) P=0.03
20
15
(14.7) (13.8)
10
(8.6)
5
0
Angiographic restenosis Clinical restenosis
(DS≥50%) (TVR)
Kastrati A, et al. Circulation 2001;103:2816-21

11. Stent Strut Thickness
 Thinner stent struts associated with improved clinical outcomes1-4
0.006
0.005
Strut Thickness (inches)
0.004
1st Generation DES 2nd Generation
0.003
0.002
Cypher Taxus Taxus Endeavor Resolute Xience V Coracto
Express Liberté
0.0055” 0.0036” 0.0036” 0.0032” 0.0031”
0.001 140 μm 0.0052” 0.0038” 91 μm 91 μm 81 μm 80 μm
132 μm 97 μm
0
1. Kastrati, A, et al. Circulation 2001;103: 2816-2821. 2. Rittersma, SZ, et al. Am J Cardiol 2004; 93: 477-480
3. Pache, J, et al. J Am Coll Cardiol 2003; 41: 1283-1288 4. Turco, M., et al., JACC CI 2008; 1: 699-709.
Modified from Ian Meredith

12. Drug Eluting Stents
Stent Coating
-Polymer type
-Coating thickness
-Biocompatibility
Inflammation

13. What is the ideal drug eluting stent polymer?
• Inert Polymer that is completely biocompatible
Note: Important to distinguish between “short” and “long term”
biocompatibility. Most if not all biocompatible polymers may cause
some foreign body reactions months or years later
• Ability to control drug release at desired rate over a prescribed
time period
• Good adhesion to stent struts & high flexibility
– No acute or late peeling!
• High drug carrying capacity (ie, “carrying efficiency”)
– Low polymer “dose” critical to minimize chronic inflammatory response

14. Polymer Coatings
Durable vs. Biodegradable
Durable
(non-biodegradable)
Biodegradable
CE mark BioMatrix - Poly(lactide) (PLA)
Xience V – Fluoropolymer (Europe)
Cypher - PEVA (polyethylene-co-vinyl Poly(glycolic-co-lactic acid)
acetate) + PBMA (poly(n-butyl) (PLGA)
methacrylate) FDA
Approved Poly(glycolide) (PGA)
Taxus - SIBBS (poly (styrene-b-
isobutylene-b-styrene)) Poly(e-caprolactone) (PCL)
Endeavor - PC (Phosphorylcholine)
Poly(dioxanone) (PDS)
Why the push towards biodegradable polymers?

15. Hypersensitivity – Chronic Inflammation
40 yrs old female, Underwent Cypher stents implantation in RCA and LAD
2years antemortem, She died suddenly after surgery. (Plavix and aspirin
discontinued prior to surgery)
LAD
RCA

16. Patients with Hypersensitivity Reaction
(7 of 95 patients; 7.4%)
Stent Indication Number Stent length Duration of
Case Age Sex Location Cause of death
type for PCI of stent (mm) implant (months)
AMI (LST)
1 58 M Cypher UAP LCX 2 18+18 18
Cardiac rupture
LAD 1 23 32
2 46 M Cypher AMI AMI (LST)
RCA 2 15+15 32
3 61 M Cypher SAP PDA 1 18 4 SCD (LST)
LAD 1 27 17
4 40 F Cypher AMI SCD (LST)
RCA 1 25 17
Removed
5 62 F Cypher SAP LAD 3 23+23+18 33
surgically
LAD 1 18 13
6 61 M Cypher SAP Non-cardiac
LD 1 17 13
7 72 M Cypher SAP LAD 1 18 13 Non-cardiac

17. CORACTOTM Coronary Drug Eluting Stent
CORACTO is coated with a very thin layer (4 μm) of bioabsorbable
polymer loaded with 1.7 μg/mm2 Rapamycin (sirolimus)
Polylactic-co-glycolic acid based copolymer is used as drug carrier.

18. Drug Eluting Stents
Drug
-Drug type/load
-Elution Profile
-Toxicity
Safety

19. FDA Approved DES
Release
Dose Kinetics
Stents Drug Polymer
(µg) (28 days
%)
Xience V Everolimus Fluoropolymer 1.0 µg/mm2 80
Taxus Paclitaxel SIBBS (poly (styrene-b- 1.0 µg/mm2 10
isobutylene-b-styrene))
Cypher Sirolimus PEVA (polyethylene-co-vinyl 1.4 µg/mm2 68.4
acetate) + PBMA (poly(n-
butyl) methacrylate)
Endeavor Zotarolimus PC (Phosphorylcholine) 10 µg/mm2 100

20. Comparative Elution Profiles
FDA Approved DES
100 ENDEAVOR™
CYPHER®
Cumulative % Released
80 XIENCE™
60
40
20
TAXUS®
0 5 10 15 20 25 30
Days

21. How to assess variations in DES?
Impact on endothelialization
100 ?
90
Peak Percentage of
80
70
Neointima
60
Animals
50 Humans
40
30
20
10
0
3 7 14 28 3 6 12 18
Days Months
Time After Stent Implantation
Virmani, R, et al. Heart 2003;89:133

22. Evaluation of Endothelium has
Evolved in Pre-Clinical Models
Histological Scanning Electron En-Face
Visual Microscopy Confocal
Estimation Microscopy
EC-Specific Markers

23. Comprehensive Endothelial Cell Coverage
of FDA approved DES
Comparison of Endothelialization following Implantation of CYPHER (S-ES), TAXUS (P-ES),
ENDEAVOR (Z-ES) and XIENCE V (E-ES) Stents in Rabbit Iliac Arteries at 14 and 28 days
1st generation 2nd generation
CYPHER TAXUS ENDEAVOR™ XIENCE V
Joner M et al.Endothelial Cell Recovery Between Comparator Polymer-Based Drug-Eluting Stents. JACC 2008

24. Scanning Electron Microscopy of 14-Day Comparator Stents
S-ES P-ES Z-ES E-ES BMS

25. Scanning Electron Microscopy of 28-Day Comparator Stents
S-ES P-ES Z-ES E-ES BMS

26. En Face SEM Analysis of Comparator Stents
(%)
A 100 P< 0.0001 P= NS
80 * * *
14-Day
60
40
20 S-ES (Cypher)
0 P-ES (Taxus)
Above Struts Between Struts
Z-ES (Endeavor)
B (%) P= NS P= NS E-ES (Xience V)
100 BMS
80
28-Day
60
40
20
0
Above Struts Between Struts

27. Confocal Analysis
PECAM-1 (CD31) Thrombomodulin (TM) Merged

28. Confocal Analysis
Example images
Endothelialized Strut Non-Endothelialized Strut

29. Confocal Analysis
S-ES P-ES Z-ES E-ES BMS
14-day Comparator Stents

30. En Face Confocal Analysis (PECAM-1) of Comparator Stents
(%) P=0.02 P= NS
100
* * *
80
60
14-Day
40
20 S-ES
0 P-ES
Above Struts Between Struts
Z-ES
(%) P= NS
P= NS E-ES
100
BMS
80
60
28-Day
40
20
0
Above Struts Between Struts

31. CORACTO Pre-clinical Study
Comparison of vascular healing and endothelialization of the
Coracto DES to 1st and 2nd generation DES, along with a bare
metal stent, in the rabbit iliac stent model.
Alvimedica DES 1st generation DES 2nd generation DES Bare Metal Stent
Coracto Cypher Xience V Constant

32. Study Parameters
Endothelialization Vascular Healing
(14-days) (28-days)
Constant Coracto Xience V Cypher Constant Coracto Xience V Cypher
n=6 n=6 n=6 n=6 n=8 n=8 n=8 n=8
Evaluated by: Evaluated by:
o Scanning electron microscopy (SEM) o Light Microscopy (H&E and Movat)
o Confocal Microscopy Injury, Strut Coverage
Fibrin, Inflammation
SEM
Confocal

33. Scanning Electron Microscopic Findings
Above and in between the Stent struts
SEM % endothelial coverage SEM % endothelial coverage
above stent struts @ 14 days between stent struts @ 14 days
100 100
P=0.066 ★
P<0.0001
80 80
60
★ 60
★
40 40
★
20 20
0 0
CONSTANT CORACTO Xience V Cypher CONSTANT CORACTO Xience V Cypher
= significantly different from control ANOVA and Dunnett post hoc test (CONSTANT as control)

34. Constant Coracto Xience Cypher

35. Confocal Microscopic Findings of PECAM-1
Above and in between the Stent struts
% PECAM-1 positive endothelial cells % PECAM-1 positive endothelial cells
above stent struts @ 14 days between stent struts @ 14 days
100 100
80 80
P= 0.0003 P=0.0087
60 ★ ★ ★ 60 ★ ★
40 40
20 20
0 0
CONSTANT CORACTO Xience V Cypher CONSTANT CORACTO Xience V Cypher
�= significantly different from control (Dunnett post hoc test, CONSTANT as control)

36. Confocal Microscopy following PECAM-1 staining in Rabbit at 14-days
CONSTANT CORACTO
CYPHER XIENCE V

37. Morphometric Measurements
Neointimal Thickness at 28 days
0.10 BMS
* Coracto
Neointimal Thickness [mm]
0.08
0.06
0.04 Xience V Cypher
0.02
0
Cypher
Xience V
Coracto
BMS

38. 28-day Light Microscopy Results
p < 0.0001
75
* * BMS
60
Coracto
% Fibrin
45
30
15
CORACTO
Xience V
Cypher
0
CONSTANT
Xience V Cypher
P < 0.0001
2
* *
Fibrin Score
1
CORACTO
0
Cypher
Xience
0
CONSTANT

39. 28-day Light Microscopy Results
P < 0.0001
Inflammation Score
2
*
BMS Coracto
1
CORACTO
Xience V
Cypher
0
0
CONSTANT
80 P < 0.0001
* Xience V Cypher
% Giant Cells
60
40
20
CONSTANT
CORACTO
Xience V
Cypher
0
0

40. Summary
• Endothelial integrity is the key to prevention of
late stent thrombosis
• 1st generation DES are not fully re-endothelialize
as demonstrated by SEM and Confocal
microscopy (PECAM-1 staining) especially above
stent struts at 14- and 28-days
• 2nd generation DES show greater
endothelialization than 1st generation DES
• The Coracto stent shows higher degree of
reendothelialization as compared to other DES and
less inflammation as compared to Cypher.

41. Acknowledgments
Funding
Alvimedica
CVPath Institute
Frank D Kolodgie, PhD CVPath Institute
Elena Ladich, MD
Masataka Nakano, MD
Fumiyuki Otsuka, MD
Ed Acampado, DVM
Youhui Liang, MD
Abebe Atiso, HT
Jinky Beyer
Giselle Magsalin
Hedwig Avallone, HT
Carma Cooney, HT Washington
Hengying Ouyang, MD DC
Roberto Calvo