the invention provides novel imidazopyridin - 3 - yl - acetic acid hydrazides of formula wherein r 1 , r 2 and r 3 have different meanings , and pharmaceutically acceptable salts , polymorphs , hydrates , tautomers , solvates and stereoisomers thereof . compounds of formula are useful for treating or preventing , in a human or non - human mammal , diseases associated with gaba a receptors modulation , anxiety , epilepsy , sleep disorders including insomnia , and for inducing sedation - hypnosis , anesthesia , sleep and muscle relaxation . the invention also provides synthetic processes for preparing said compounds .