Lexiscan ™(regadenoson) is an injectable adenosine A2A
receptor agonist for use as a pharmacologic stress agent in
myocardial perfusion imaging (MPI) studies in patients unable
to undergo adequate exercise induced stress. Regadenoson
is the first adenosine A2A receptor agonist shown
to be safe and effective as a pharmacologic stress agent in
MPI studies. It is delivered as a rapid bolus (approximately
10 seconds) with no dose adjustment required for body
weight. The product was developed under a license and collaboration
agreement between CV Therapeutics and Astellas,
and was launched by Astellas in June of 2008.
Regadenoson is a selective, short-acting adenosine A2A receptor agonist (Ki = 1.1 nM for pig striatum A2A receptor). It increases coronary blood flow 3.4- to 3.8-fold with a half-time to reversal of 1.9-2.6 minutes in open-chest anesthetized pigs. Regadenoson is used to induce hyperemia (increased blood flow), particularly in the context of myocardial perfusion imaging. It has also been found to increase the delivery of compounds to the central nervous system through the blood-brain barrier in animals.
A selective A2A adenosine receptor agonist in myocardial imaging
Regadenoson is a selective and potent A2A adenosine receptor agonist (1). The adenosine A2A receptor is a G-protein-coupled receptor and a key therapeutic target for oncologic, inflammatory, Parkinson''s and cardiovascular diseases (2). In rodent studies, it has been shown that co-administration of Regadenoson with Temozolomide (T017775) can increase Temozolomide concentration in the brain (3).
ChEBI: Regadenoson is a purine nucleoside.
The synthesis
of regadenoson has been reported in several papers and patents and a scalable procedure is detailed in the scheme. The synthesis was initiated with the reaction of 2-
chloroadenosine hemihydrate (94) and hydrazine monohydrate
at 40-50 ??C to provide 95 in 81% yield with 99.3%
purity. Hydrazine 95 was condensed with ethyl-2-formyl-3-
oxopropionate (96) under refluxing IPA to furnish the pyrazole
97 in 77% yield which was collected by filtration and
used in next step without further purification. Pyrazole 97
was then reacted with methyl amine at room temperature to
provide regadenoson (XV). Although the yield was not reported,
the product was collected by simple filtration.
regadenoson was selective for the a2a adenosine receptor versus the a1, a2b, and a3 receptors in binding and functional studies. regadenoson was also found to be a full and potent agonist to cause coronary vasodilation, a response that has a very large a2a receptor reserve [1].
in a study of 10 conscious dogs, authors compared intravenously injected regadenoson to that of adenosine. regadenoson caused a dose-dependent increase of coronary blood flow (cbf), whereas adenosine was less potent but produced equivalent hyperemia. thus, authors concluded that regadenoson is a potent coronary vasodilator with a short duration of action, minimal and transient systemic hemodynamic effects, and ease of administration [1].
[1] cerqueira md. the future of pharmacologic stress: selective a2a adenosine receptor agonists. am j cardiol. 2004 jul 22;94(2a):33d-40d; discussion 40d-42d.
