Development of Thiochroman Dioxide Analogues of Benzothiadiazine Dioxides as New Positive Allosteric Modulators of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors.

On the basis of the activity of 1,2,4-benzothiadiazine 1,1-dioxides as positive allosteric modulators of AMPA receptors, thiochroman 1,1-dioxides were designed applying the isosteric replacement concept. The new compounds expressed strong modulatory activity on AMPA receptors , although lower than their corresponding benzothiadiazine analogues. The pharmacokinetic profile of three thiochroman 1,1-dioxides (, , ) was examined after oral administration, showing that these compounds freely cross the blood-brain barrier. Structural analysis was achieved using X-ray crystallography after cocrystallization of the racemic compound in complex with the ligand-binding domain of GluA2 (L504Y/N775S). Interestingly, both enantiomers of were found to interact with the GluA2 dimer interface, almost identically to its benzothiadiazine analogue, BPAM344 (). The interactions of the two enantiomers in the cocrystal were further analyzed (mapping Hirshfeld surfaces and 2D fingerprint) and compared to those of . Taken together, these data explain the lower affinity on AMPA receptors of thiochroman 1,1-dioxides compared to their corresponding 1,2,4-benzothiadiazine 1,1-dioxides.