Neuroprotective profile of pyridothiazepines with blocking activity of the mitochondrial Na+/Ca2+ exchanger

• Mitochondria participate in the control of Ca2+, a key event in many cell processes.
• The mitochondrial Na+/Ca2+ exchanger (mNCX) plays an essential role in such control.
• There are few and poor mNCX blockers, like CGP37157, which lacks of selectivity.
• The new thiazepines analogs to CGP37157 could be used to better study the mNCX.
• New derivatives present an aqueous solubility above 0.1 mM, measured by UV/visible.

The mitochondrial Na+/Ca2+ exchanger plays an important role in the control of cytosolic Ca2+ cycling in excitable cells, essential for the regulation of a plethora of Ca2+-dependent physio-pathological events, such as apoptosis in the presence of a Ca2+ overload. There are very few pharmacological tools available to study both physiological and pathological implications of the mitochondrial Na+/Ca2+ exchanger, where the benzothiazepine CGP37157 is the best-known ligand, used since the 1980s. However, it is not an efficient blocker and lacks of selectivity, as also blocks several other cellular Ca2+ transporters. Moreover, CGP37157 is a very lipophilic drug, showing very poor water solubility, what has hindered its therapeutic use. Attempting to improve its pharmacokinetic profile as well as its potency and selectivity, we herein describe the synthesis of new CGP37157 analogs, where the benzene-fused ring has been replaced by a pyridine. On top of a better water solubility and lower log P value, some of these new pyridothiazepine derivatives also presented a higher capacity to regulate the mitochondrial Ca2+ clearance, while keeping the neuroprotective properties presented in the head compound CGP37157.

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