The invention provides substituted imidazo┌1,5-a┐pyrimidines and related organic 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[1,5-a]pyrimidine compounds described herein include substituted 2,4-dimethyl-N-phenylimidazo[1,5-a]pyrimidine-8-carbox-amide compounds and variants thereof.