Sirolimus Was Unexpectedly Found to Have Immunosuppressive Activity
A naturally occurring substance called sirolimus was discovered in a soil sample from Easter Island.
- Sirolimus first was thought to have some promise as an antifungal antibiotic but this idea was jettisoned when sirolimus was unexpectedly found to have immunosuppressive activity.
- After the usual delays inherent in drug research and development, the US Food and Drug Administration in 1999 approved the use of sirolimus as an immunosuppressant agent.
- Evidence had been uncovered earlier in the nineties that sirolimus was also a potent inhibitor of the growth of smooth muscle cells in blood vessels.
- The idea was then "hatched" that sirolimus might be used to inhibit the restenosis (reclosure) of coronary arteries.
- Today, after a balloon angioplasty has been done to open a clogged coronary artery, a mesh tube called a stent is often inserted to keep the artery open; however, restenosis occurs in up to a third of cases when smooth muscle cells migrate from the vessel wall into the stent.
- The muscle cells proliferate there and narrow the interior diameter of the stent.
Sirolimus Stents Show Considerable Promise
- Stents medicated with sirolimus have shown promise in the prevention of restenosis after balloon dilation of simple coronary lesions.
- By "simple" coronary lesions is meant, for example, a short area of narrowing in one coronary artery.
- The clinical trial compared the sirolimus stent with a standard stent in patients with complex coronary lesions.
- The research was done at 53 centers in the US. In the trial there were 1,058 patients with "complex" coronary lesions.
- The coronary disease in these patients was considered "complex" because of the frequent presence of diabetes, the high percentage of patients with longer lesions, and small vessels.
- The sirolimus stent proved to be superior to standard stents in the prevention of restenosis.
- The rate of failure of the vessel was reduced from 21 percent with a standard stent to 8.6 percent with a sirolimus stent.
- The investigators conclude with typical scientific understatement that: "Coronary stents coated with sirolimus have considerable promise in the treatment of simple and complex coronary stenoses."
Sirolimus Stents Good for Long Narrowed Areas
- One medical report focused on the use of sirolimus stents compared with bare-metal stents in long narrowed areas in the coronary arteries.
- The research was done in Europe. There were 352 patients in the trial. All had a long narrow segment in a single coronary artery that need to be treated.
- Eight months after the stents were put in, the minimum diameter was significantly greater within sirolimus stents than in the standard bare metal stents.
- The rate of restenosis was significantly reduced with the sirolimus stents compared with the bare metal stents and at nine months, fewer patients with sirolimus stents had major adverse cardiac events than did the controlled group.
- The researchers concluded with precision that: "Sirolimus-eluting stents are better than bare-metal stents for treatment of single long atherosclerotic lesions in a coronary vessel smaller than three millimeters in diameter."
You will find more information about angioplasty; as well as, the stent at the following links:
Angioplasty Info and the Stent, Part 1
Angioplasty Info and the Stent, Part 2
Angioplasty Info and the Stent, Part 3
Angioplasty Info and the Stent, Part 4
Angioplasty Info and the Stent, Part 5
Angioplasty Info and the Stent, Part 7