ABSTRACT
HCN4 channels are considered to be a promising target for cardiac pathologies, epilepsy, and multiple sclerosis. However, there are no subtype-selective HCN channel blockers available, and only a few compounds are reported to display subtype preferences, one of which is EC18 (cis-1). Herein, we report the optimized synthetic route for the preparation of EC18 and its evaluation in three different pharmacological models, allowing us to assess its activity on cardiac function, thalamocortical neurons, and immune cells.
Subject(s)
Cyclic Nucleotide-Gated Cation Channels , Potassium Channels , Cyclic Nucleotide-Gated Cation Channels/metabolism , Structure-Activity Relationship , Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels , Neurons/metabolismABSTRACT
The P2X7 receptor (P2X7R) stands out among the purinergic receptors due to its strong involvement in the regulation of tumor growth and metastasis formation as well as in innate immune responses and afferent signal transmission. Numerous studies have pointed out the beneficial effects of P2X7R antagonism for the treatment of a variety of cancer types, inflammatory diseases, and chronic pain. Herein we describe the development of novel P2X7R antagonists, incorporating piperazine squaric diamides as a central element. Besides improving the antagonists' potency from pIC50 values of 5.7-7.6, ADME properties (logD7.4 value, plasma protein binding, in vitro metabolic stability) of the generated compounds were investigated and optimized to provide novel P2X7R antagonists with drug-like properties. Furthermore, docking studies revealed the antagonists binding to the allosteric binding pocket in two distinct binding poses, depending on the substitution of the central piperazine moiety.
Subject(s)
Cyclobutanes/pharmacology , Diamide/pharmacology , Piperazine/pharmacology , Purinergic P2X Receptor Antagonists/pharmacology , Receptors, Purinergic P2X/metabolism , Cyclobutanes/chemical synthesis , Cyclobutanes/chemistry , Diamide/chemical synthesis , Diamide/chemistry , Dose-Response Relationship, Drug , HEK293 Cells , Humans , Molecular Structure , Piperazine/chemical synthesis , Piperazine/chemistry , Purinergic P2X Receptor Antagonists/chemical synthesis , Purinergic P2X Receptor Antagonists/chemistry , Structure-Activity Relationship , Tumor Cells, CulturedABSTRACT
The central CB2 receptor represents a promising target for the treatment of neuroinflammatory diseases as CB2 activation mediates anti-inflammatory effects. Recently, the F-18 labeled PET radiotracer [18F]7a was reported, which shows high CB2 affinity and high selectivity over the CB1 subtype but low metabolic stability due to hydrolysis of the amide group. Based on these findings twelve bioisosteres of 7a were synthesized containing a non-hydrolysable functional group instead of the amide group. The secondary amine 23a (Kiâ¯=â¯7.9â¯nM) and the ketone 26a (Kiâ¯=â¯8.6â¯nM) displayed high CB2 affinity and CB2:CB1 selectivity in in vitro radioligand binding studies. Incubation of 7a, 23a and 26a with mouse liver microsomes and LC-quadrupole-MS analysis revealed a slightly higher metabolic stability of secondary amine 23a, but a remarkably higher stability of ketone 26a in comparison to amide 7a. Furthermore, a logD7.4 value of 5.56⯱â¯0.08 was determined for ketone 26a by micro shake-flask method and LC-MS quantification.
