The invention relates to antagonists of serotonin 5-HT6 receptors simultaneously regulating homeostasis of Ca+2 ions in cells, representing substituted 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles of the general formula 1, pharmaceutically acceptable salts and/or hydrate thereof. In the general formula 1: R1 represents amino group substituent selected from optionally substituted C1-C5 alkyl; R2i is one or more substituents selected from hydrogen, halogen, C1-C3 alkyl, CF3, OCF3; Ar is phenyl optionally substituted with halogen, C1-C6 alkyl, C1-C6 alkoxy, substituted amino group, or CF3; or optionally substituted aromatic 6-membered heterocycle comprising 1-2 nitrogen atoms in the cycle; W represents ethylene group —CH2—CH2—, ethenyl group —CH═CH—, or ethynyl group —C≡C—. The invention also relates to the novel compounds selected from the compounds of the general formula 1, methods for their preparation, pharmaceutical compositions and methods of their use.