Lead identification and optimization of diaminopyrimidines as histamine H4 receptor ligands.

BACKGROUND: The human histamine H(4) receptor (hH(4)R) is a promising new target in the therapy of inflammatory or immune system diseases. METHODS: For the development of new hH(4)R ligands, a broad virtual screening was performed and two hits were identified. Their annelated heterocyclic core was optimized with regard to affinity and potency. RESULTS: Pharmacological characterization of the resulting diaminopyrimidines revealed different agonist and antagonist properties within the same scaffold.