Heterobicyclic compounds of Formula (I): or a pharmaceutically-acceptable salt, tautomer, or stereoisomer thereof, as defined in the specification, and compositions containing them, and processes for preparing such compounds. Provided herein also are methods of treating disorders or diseases treatable by inhibition of PDE10, such as obesity, non-insulin dependent diabetes, schizophrenia, bipolar disorder, obsessive-compulsive disorder, Huntington’s Disease, and the like.本發明係有關本說明書中所定義之式(I)之雜雙環化合物:或其醫藥學上可接受之鹽、互變異構體或立體異構體,及含有其之組合物,及製備該等化合物之方法。本文亦提供治療可藉由抑制PDE10來治療之病症或疾病的方法,該等病症或疾病為諸如:肥胖、非胰島素依賴性糖尿病、精神分裂症、躁鬱症、強迫症、亨廷頓氏病(Huntington's Disease)及其類似病症或疾病。