The invention provides substituted imidazo[1, 2-b]pyridazine compounds, substituted imidazo[1, 5-b]pyridazine compounds, related compounds, compositions containing such compounds, medical kits, and methods for using such compounds and compositions to treat medical disorders, e.g., Gaucher disease, Parkinson' s disease, Lewy body disease, dementia, or multiple system atrophy, in a patient. Exemplary substituted imidazo[1, 2-b]pyridazine compounds described herein include substituted imidazo[1, 2-b]pyridazine-3-carboxamide compounds and variants thereof.