ESTRADIOL TOCURE RESTENOSIS; The ESTRACURE-1 Trial.

BACKGROUND AND RATIONALE

Since its clinical introduction some 20 years ago, angioplasty (PCTA) has increased in popularity as a clinically effective method for improving blood flow though stenosis or occluded arteries. However, over the next 3 to 6 months, restenosis occurs in approximiately 30-40% of patients, thereby constituting a significant limitation to the long-term success of this procedure. A number of trials using drugs effective in animals for reducing restinosis have produced negative clinical results. The complexity of the restenosis process, species particularities, and sub-optimal drug dosing may partially explain these differences. Restenosis is predominantly due to neointimal hyperplasia and constrictive remodeling. Inadequate compensatory enlargment of a vessel after angioplasty (inadequate vascular remodeling) is considered an important mechanism of post-PTCA restenosis. Constrictive remodeling can be effectively countered by the use of stents, which may account for the decreased incidence of restenosis observed with their use. Despite the use of stents, restenosis continued to limit the long-term success of PTCA. Stenting may provoke an exuberant proliferative response compared to balloon angioplasty. The favorable effect of stents in countering constrictive remodeling is therefore in some cases offset by the increased neointimal hyperplasis associated with stenting, causing difficult to treat in-stent restenosis. Although brachytherapy has been reported to show beneficial effects, few effective therapies existed at this time of neointimal proliferation. Vascular smooth muscle cell (SMC) migration and proliferation occur as early as 36 hours following arterial injury. The number of SMC in the neointima peaks around 2 weeks and cell replication rate after these first few weeks is countered by cell death. Accumulation of extracellular matrix and connective tissue which may constitute the bulk of neointima further increases the intimal thickness. Several mitogens including acidic and basic fioroblast growth factors (aFGF, bFGF), insulin-like growth factors (IGFs), thrombin, angiotensin II, endothelin stimulate SMC proliferation.

Rule of 17B-Estradiol and Estrogen Receptors in the Cardiovascular System
Effects of estrogen therapy on serum lipid concentrations largely result from ER-mediated effects on the hepatic expression of apoprotein genes. 49 Estrogen therapy in postmenopausal women decrease total and LDL-cholesterol concentrations, increases HDL-cholesterol and triglycerides concentrations, and decreases serum L.P. (a) lipoprotein concentrations. Administration of 17B-estradiol (17BE) can decrease the oxidation of LDL-cholesterol.50 This antioxidant effect may be due to ER-mediated changes in the expression of genes for enzymes that regulate the local production of superoxide.51 Hepatic expression of the genes for several coagulation and fibrinolytic proteins is also regulated by estrogen through ER49. Plasma fibrinogen, antithrombin III, protein 5, plasminogenactivator inhibitor is decreased by estrogen. Finally, estrogen directly regulates vasomotor tone through both short-term and long-term effects on the vasculature. Administration of estrogen is associated with decrease plasma concentrations of renin, angiotensin-converting enzyme, endothelin-1 and decreased vascular expression of the gene for angiotensin II receptor type 1, as well as an increased ratio of nitric oxide to endothelin-1 in plasma.43 The net effect of these changes is to promote vasodilatation.

Migration and proliferation of vascular cells remains a cornerstone in neointimal formation and vascular healing. Cardioprotective effects of estrogens have been described in animal and human studies. However, the intracellular mechanisms related to these effects remain poorly understood. In previous studies, we have shown that a single local delivery of 17-beta-estradiol (17BE) prevented restenosis following PTCA (fig. 1).

Fig. 1. 17B-Estradiol PTCA only Vehicle

Verroff’s staining.

In a preliminary study, we demonstrated the presence of the two estrogen receptors (ER) proteins. The presence was revealed using anti-ERa or anti-ERb )1:1000 dilution, Santa Cruz Biotechnology) by western blot (Fig. 2). The confirmation of the existence of the ER in the endothelial cells (EC) and smooth muscle cells (SMC) was crucial to the potential success of this clinical study.

Fig. 2.

OBJECTIVES

1) To evaluate the effects of local delivery of 176-E on late luminal loss and restenosis after Percutaneous Coronary Intervention (PCI).
2) To investigate the inprovement in endothelial function after local delivery of 17B-E and stent implantation.
3) To understand the mechanisms for the clinical benefit 17B-E delivery in vascular healing after PCI.

Since more than 80% of patients undergo stent implantation, it is critical to evaluate the benefit of local delivery of 17B-E following stent implantation. We have observed a similar reduction in restenosis after stenting with 17B-E administration in a porcine coronary artery model (submitted to Circulation). Further more, we have found a significant reduction in the extracellular matrix and collagen expression after local administration of 17B-E and stenting (in preparation).
However, this strategy has not been evaluated in a clinical study. Therefore the following study will be intended to confirm the potential for clinical utility of local 17B-E delivery during PCI to prevent late luminal loss and improve vascular healing after vessel injury.

STUDY OUTLINE

A multicenter prospective randomized clinical trial will be performed at The Montreal Heart Institute. This study will involve 4-6 clinical centers across Canada chosen for the quality of previous work in interventional cardiology research. The homodynamic laboratory of The Montreal Heart Institute will coordinate the trial.

A 6-month angiographic evaluation will be performed and the analysis will be under the leadership of Dr. Jacques Lesperance who has lead the Quantitative Coronary Angiography (QCA) laboratory in many clinical trials.

Predetermined intracoronary Doppler and hematology sub-studies will be performed to assess the mechanisms of benefit for 17B-E delivery during PCI.

Based on the late loss observered in two recent trials we performed (\SISA and CART), we can assume that a trial of 300 pts should have a power of 80% to detect a clinically relevant reduction in late lumen loss of 30% with a 0.05. Further power calculations and a formal clinical protocol will be submitted to the Institutional Review Board.

The timeline for this study is 18 months for enrollment and angiographic follow-up to be complete. However, a 3-month initiation and close-out phases are expected in such a trial. We therefore expect to enroll our first patient in Q1 2002 and finish enrollment during Q4 2002. The angiographic follow-up should be completed by the end of Q2 2003. Final statistical analysis and clinical report should be available by the end of Q4 2003.

EXPECTED RESULTS

This study will give important information on the potential impact of local 17B-E after PCI and the role of this therapy to prevent restenosis. The importance of our strategy to promote a better vascular healing can be placed in perspective of the fact that brachytherapy may retard reendothelialization and impair vessel wall recovery leading to late thrombosis and a potential catch-up phenomena with loss of the initial gains at long term follow-up. It is our understanding from our results and the data available in the literature that local 17B-E offers a promising new approach to vessel passivation after PCI.

FUTURE PERSPECTIVES

All the techniques to be used in this proposal have been published and/or are used by us and our close collaborators, we therefore do not foresee any difficulties to investigate our hypothesis and answer to our objectives. This proposal will bring new understandings in the role of estradiol and estrogen receptors in the vascular healing after stent implantation.

It is our intent to pursue in this field and propose to the patient needing improved vascular healing an ESTRACURE solution including catheter and drug coated stents delivery of 17B-Estradiol to improve clinical outcome. The data obtained may lead to significant advances in therapeutic strategies to improve patient care and reduce restenosis.
ESTRACURE
Confidential
September 25th, 2001