Since the discovery and early characterization of the histamine H receptor (HR) in the 1980’s, predominantly imidazole-based agonists were presented to the scientific community such as N-methylhistamine (N-MeHA) or (R)-α-methylhistamine ((R)α-MeHA). Whereas therapeutic applications have been prompted for HR agonists such as treatment of pain, asthma and obesity, several drawbacks associated with imidazole-containing ligands makes the search for new agonists for this receptor demanding. Accordingly, high interest arose after publication of several pyrrolidindione-based, highly affine HR agonists within this journal that avoid the imidazole moiety and thus, presenting a novel type of potential pharmacophores (Ghoshal, Anirban et al., 2018). In our present study performed in two independent laboratories, we further evaluated the exposed lead-compound (EC = 0.1 nM) of the previous research project with regards to pharmacological behavior at HR. Thereby, no binding affinity was observed in neither [H]N-MeHA nor bodilisant displacement assays that contradicts the previously published activity. Additional functional exploration employing GTPγ[S], cAMP-accumulation assay and cAMP response element (CRE)-driven reporter gene assays exhibited slight partial agonist properties of such pyrrolidindiones but acting apart from the reported concentration range. We conclude, that the previously reported actions of such pyrrolidindiones result from an overestimation based on the method of measurement and thus, we cast doubt on the new pharmacophores with HR agonist activity.
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