Substituted tetrazolo[1,5-A]pyrazine inhibitors of histamine receptors for the treatment of disease

A compound of structural Formula (IX)

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is a monocyclic 4- to 7-membered nonaromatic heterocycloalkyl, which may be optionally substituted with a substituent chosen from amino and lower alkyl;
• and
• R2 is chosen from monocyclic 5- to 7-membered nonaromatic heterocycloalkyl, phenyl and monocyclic 5- to 6-membered heteroaryl, any of which may be optionally substituted with one to three substituents chosen from halogen, lower alkyl, lower haloalkyl, lower alkoxy, lower haloalkoxy, cyano, lower amino, hydroxy, and nitro.