The chemokine receptor CCR3 is believed to play a role in the development of allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis. Despite the conflicting results that have been reported regarding the importance of eosinophils and CCR3 in allergic inflammation, inhibition of this receptor with small molecule antagonists is thought to provide a valuable approach for the treatment of these diseases. This review describes the structure-activity relationships (SAR) of small molecule CCR3 antagonists as reported in the scientific and patent literature. Various chemical classes of small molecule CCR3 antagonists have been described so far, including (bi)piperidine and piperazine derivatives, N-arylalkylpiperidine urea derivatives and (N-ureidoalkyl)benzylpiperidines, phenylalanine derivatives, morpholinyl derivatives, pyrrolidinohydroquinazolines, arylsulfonamides, amino-alkyl amides, imidazole- and pyrimidine-based antagonists, and bicyclic diamines. The (N-ureidoalkyl)benzylpiperidines are the best studied class in view of their generally high affinity and antagonizing potential. For many of these antagonists subnanomolar IC(50) values were reported for binding to CCR3 along with the ability to effectively inhibit intracellular calcium mobilization and eosinophil chemotaxis induced by CCR3 agonist ligands in vitro.
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