Selective A(3) adenosine receptor antagonists derived from nucleosides containing a bicyclo[3.1.0]hexane ring system

Area of Science:

• Medicinal Chemistry
• Pharmacology
• Organic Synthesis

Background:

• Adenosine receptors (ARs) are crucial drug targets.
• Developing selective antagonists for AR subtypes, particularly A3 AR, is of significant therapeutic interest.
• Previous efforts focused on modifying adenosine derivatives and nucleoside analogues.

Purpose of the Study:

• To synthesize and evaluate novel 5'-modified adenosine derivatives and (N)-methanocarba nucleoside analogues.
• To identify potent and selective antagonists for the human A3 adenosine receptor.
• To explore structure-activity relationships for A3 AR antagonism.

Main Methods:

• Synthesis of 5'-modified adenosine derivatives and (N)-methanocarba nucleosides.
• Binding assays to determine affinity at adenosine receptor subtypes (ARs).
• Functional assays, including [35S]GTPγS binding, to assess antagonist activity at the A3 AR.

Main Results:

• Truncated (N)-methanocarba analogues lacking a 4'-hydroxymethyl group demonstrated high potency and selectivity as human A3 AR antagonists.
• Compounds 33b-39b, specifically N6-3-halobenzyl and related arylalkyl derivatives, exhibited potent A3 AR antagonist activity with binding Ki values ranging from 0.7-1.4 nM.
• Compound 33b (3-iodobenzyl) effectively inhibited NECA-stimulated [35S]GTPγS binding with a KB of 8.9 nM.

Conclusions:

• A novel series of highly potent and selective A3 AR antagonists based on the (N)-methanocarba nucleoside scaffold has been successfully developed.
• The structural modifications, particularly the truncated nature and specific N6-substituents, are critical for achieving potent and selective A3 AR antagonism.
• These findings provide valuable lead compounds for the development of new therapeutics targeting A3 AR.