Drug Eluting Stents: The Taxus Stent

Drug eluting stents were developed to combat the need for recurrent cardiovascular procedures. Bare metal stents were effective in the reduction of early ischemic complications associated with angioplasty but were limited by scar tissue formation within the stent. This scar often resulted in a recurrence of the symptoms that led to the initial procedure. A drug eluting stent consists of the stent platform, the polymer to hold the drug, and a drug to inhibit the scar formation induced by angioplasty.

Taxus stent was developed by Boston Scientific and came to market in 2004. The stent quickly became the market leader with wide spread acceptance and use. The original stent platform was the Express2 bare metal stent. This stainless steel stent was coated with a polymer (Transulate) and Paclitaxel (commonly used in ovarian cancer and lung cancer). The polymer keeps the drug adherent to the stent and controls the delivery of the drug. Paclitaxel inhibits smooth muscle growth inside the stent. The current version of the stent is called the Liberte. It is coated with the same polymer and drug, but on a new thin strut stent that is lower profile and thus easier to implant.

The Taxus stent has been extensively studied by trials sponsored by Boston Scientific that lead to approval. The pivotal trial that led to approval was Taxus IV, where the bare stent was compared with the drug-coated. The finding demonstrated a reduction in repeat procedures with an acceptable safety profile. Comparisons to the Cypher stent from J&J followed shortly after approval. After many studies, the two stents were essentially considered equivalent. The Taxus platform has been studied in more than 43,000 patients (sponsored by Boston Scientific). The stent has a very low rate of repeat procedures (about 8 percent of cases). The stent has been well studied in acute MI, chronic occlusions, long lesions, overlapping stents and in bifurcations. All of these situations are considered of label indications for the most part. It comes in sizes ranging from 2.25mm to 4mm in diameter and 8mm to 32mm in length. The exact indications for use from the product insert are below:

The TAXUS Express2 Paclitaxel-Eluting Coronary Stent System is indicated for improving luminal diameter for the treatment of de novo lesions in native coronary arteries ≥ 2.25 to ≤ 4.00 mm in diameter in lesions ≤ 28 mm in length, and within bare metal stent restenotic lesions ≥ 2.5 to ≤ 3.75 mm in diameter and ≤ 28 mm in length.

With drug-coated stents comes the risk of stent thrombosis. In 2006, at the peak of our fears over stent thrombosis, a drop in DES usage was seen. After a careful analysis of the data, the risk of stent thrombosis was determined to be equivalent in comparison to bare stents after the first 12 months. Newer studies and more extensive data have pointed towards a possible mortality benefit with DES. The Taxus stent has a relatively low rate of stent thrombosis, which varies between 0.5 to 1.7 percent, depending on the definition used. It is mandatory to take Plavix and aspirin for 12 months after stent implantation. If a patient is considered to be at high risk for bleeding Plavix can be potentially stopped at 6 months. The Stent Plus program, sponsored by Boston Scientific, is designed to help patients remain adherent to the medication regimen necessary after DES implantation.