First human experience with angiopeptin-eluting stent: a quantitative coronary angiography and three-dimensional intravascular ultrasound study

Controlling drug delivery from coronary stents: are we aiming for the right targets?

In this review article, the currently employed or explored delivery concepts for local intravascular drug delivery with drug-eluting stents (DES) are discussed with a special emphasis on clinical evidence regarding the desired release profiles. Traditional concepts to control drug release from DES include diffusion through polymers, polymer degradation and erosion as well as dissolution of particulate drug. Published clinical studies do not always reveal fine mechanistic details. The long duration of release favored for DES and the short duration of release favored for drug-eluting balloons require further investigation in experimental studies and clinical trials.

Therapeutic strategies to combat neointimal hyperplasia in vascular grafts

Neointimal hyperplasia (NIH) in bypass conduits such as veins and prosthetic grafts is an important clinical entity that limits the long-term success of vascular interventions. Although the development of NIH in the conduits shares many of the same features of NIH that develops in native arteries after injury, vascular grafts are exposed to unique circumstances that predispose them to NIH, including surgical trauma related to vein handling, hemodynamic changes creating areas of low flow, and differences in biocompatibility between the conduit and the host environment. Multiple different approaches, including novel surgical techniques and targeted gene therapies, have been developed to target and prevent the causes of NIH. Recently, the PREVENT trials, the first molecular biology trials in vascular surgery aimed at preventing NIH, have failed to produce improved clinical outcomes, highlighting the incomplete knowledge of the pathways leading to NIH in vascular grafts. In this review, we aim to summarize the pathophysiologic pathways that underlie the formation of NIH in both vein and synthetic grafts and discuss current and potential mechanical and molecular approaches under investigation that may limit NIH in vascular grafts.

Drug-eluting stents - what should be improved?

Despite the success of drug-eluting stents (DES) in reducing restenosis and the need for target vessel revascularization, several deficiencies have been unraveled since their first clinical application including the risk of stent thrombosis, undesired effects due to the stent polymer as well as the stent itself, and incomplete inhibition of restenosis (especially in complex lesions). Several novel stent systems are being investigated in order to address these issues. In second-generation DES, the rapamycin analogues zotarolimus and everolimus (and more recently biolimus) have been most extensively studied. Furthermore, special stent-coatings to actively promote endothelial healing (in order to reduce the risk of stent thrombosis) and to further reduce restenosis have been employed. To avoid undesirable effects of currently applied (durable) polymers, biocompatible and bioabsorbable polymers as well as DES delivery systems without the need for a polymer have been developed. Bioabsorbable stents, both polymeric and metallic, were developed to decrease potential late complications after stent implantation. Although most of these innovative novel principles intuitively seem appealing and demonstrate good results in initial clinical evaluations, long-term large-scale studies are necessary in order to reliably assess whether these novel systems are truly superior to first-generation DES with respect to safety and efficacy.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Coronary stents: a materials perspective

The objective of this review is to describe the suitability of different biomaterials as coronary stents. This review focuses on the following topics: (1) different materials used for stents, (2) surface characteristics that influence stent-biology interactions, (3) the use of polymers in stents, and (4) drug-eluting stents, especially those that are commercially available.