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Dr. Channick, at the present time no clinical data
are available comparing different endothelin antagonists
to each other. Thus, the ACCP could not suggest one drug
over another. At present, bosentan, a nonspecific (dual-receptor)
endothelin antagonist is FDA-approved for use. At present,
do you feel that endothelin antagonists specific for the
A receptor will have advantages over the nonspecific drugs?
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 Richard
Channick, MD
Associate Professor of Medicine
Pulmonary and Critical Care Division
University of California, San Diego Medical Center
San Diego, California
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Although the existing data for two selective endothelin-A
(ET-A) receptor antagonists, sitaxsentan and ambrisentan,
are favorable, there are not sufficient data to suggest
that they are more effective than the currently approved
dualreceptor antagonist bosentan. Arguments can be made
on both sides, for A receptor or A, B receptor antagonism.
But the proof is in the clinical data, both short and
long term. As of now, most of those data are with bosentan,
which has been shown to improve exercise capacity, functional
class, hemodynamics, quality of life, and survival, as
well as prevent clinical worsening. Time will tell whether
ET-A antagonists can reach or exceed the high bar that
bosentan has established.
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