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 Boston
Scientific Corporation Drug-Eluting Stent Program
TAXUS stent system uses paclitaxel to inhibit neointimal
hyperplasia and ExpressTM stent (by Boston Scientific)
as the stent platform. Tanslute polymer is used
for even controlled release of paclitaxel. Theoretically,
paclitaxel minimizes endothelial damage, effectively
inhibits smooth muscle cell proliferation, |
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and offers the benefit of being diffused
well into the arterial wall around the stent due
to its liphophilic property. The edge effect is
not seen in the TAXUS clinical study maybe because
paclitaxel diffuses well into tissue around the
stent.
One noticeable finding in the TAXUS clinical study
was that late loss was uniform at about 0.2 mm after
TAXUS stent application, suggesting that the endothelization
had occurred normally without difficulty after stent
application and functioning as a benefit compared
with the sirolimus eluting stent that showed negative
late loss or late loss close to 0mm, supported by
the finding that late malapposition did not pose
any problem. The finding that no significant difference
was present in late loss or restenosis rate according
to patient characteristics could also be a benefit
of TAXUS stent. For example, no restenosis was seen
in diabetes mellitus in the TAXUS II trial.
Thus, he concluded that TAXUS stent is a clinically
very effective stent system that effectively prevented
neointimal hyperplasia without delayed healing,
which could be worrisome at the time of using a
drug eluting stent.
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 TAXUS
- latest clinical data
TAXUS program was a large-scale clinical study on
the polymer-coated paclitaxel eluting stent system
under the sponsorship by Boston Scientific. After
a preclinical study, the TAXUS program included
a feasibility test (TAXUS I), efficacy test for
non-complex lesion (TAXUS II) and complex lesion
(TAXUS IV, V, VI), and safety (TAXUS III) and efficacy
test for in-stent restenotic lesion (TAXUS VII).
Among these tests, Dr. Charles Chan presented the
results of TAXUS II, IV, VI, and he tests; and presented
WISDOM registry data in which the TAXUS stent was
actually used clinically. WISDOM registry involves
26 centers from 9 countries, where the TAXUS slow
release stent system is used. |
| This program enrolls a total of 529
patients who are being followed up and currently
show excellent clinical progress. Thus, he concluded
that the TAXUS stent system is a safe and very effective
stent system even in real practice in which clinicians
have to deal with many complex lesions. |
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 Why
Polymer Coated Paclitaxel Stents
Studies have been conducted on the paclitaxel eluting
stent using the Boston Scientific’s polymer coated
stent and the Cook Inc.’s non-polymer coating stent.
The famous studies on the non-polymer coating stent
were the safety and feasibility studies that include
ASPECT and ELUTE trial and the efficacy studies
that include DELIVER trial. The polymer coated stent
study also included TAXUS program. According to
the results of these studies, ASPECT and ELUTE trial
proved the safety and feasibility of non-polymer
coating stent. However, unlike TAXUS trial, DELIVER
trail failed to prove the efficacy. He thought that
the main reason for this difference was the difference
in using polymer as in the following. He presented
that “This is a very difficult question to answer.
We do not have enough information about the manufacturing
processes and the release kinetics to compare non-polymer
coated and polymer coated, paclitaxel eluting stents.
Given that drug eluting stent is composed of three
major components, drug, stent, and vehicle, we suggest
that the answer to this question lies in one or
more of the three components. First, drug concentration
may be a reason for the different results. The studies
investigating the efficient dosage, the ASPECT,
ELUTES, and PATENCY trials, showed that the concentration
of paclitaxel is very important for sufficient inhibition
of neointima, especially in non-polymer coating
technology. From this finding, we raise the possibility
that the paclitaxel concentration of stents used
in the DELIVER trial may not have been sufficient.
Second, The drug releasing kinetics into the arterial
wall is also an important issue for sustaining the
inhibition effect on neointima growth during neoendothelization.
The polymer coated, paclitaxel eluting stent used
in the TAXUS trials has been presented by experimental
studies to release the drug slowly. However, non-polymer
coated, paclitaxel stent has a theoretical possibility
of more rapid drug release than polymer coated,
paclitaxel stent, because the polymer itself might
be effective in controlling the drug release. |
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This might be recognized as the
main advantage of polymer coating technology for
drug eluting stent. Third, the stent platform (NIR
stent in the TAXUS II trial and PENTA stent in the
DELIVER trial) might also have caused the different
results. However, we found no difference in efficiency
between the PENTA and NIR stents as drug releasing
stent platforms.” |
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