Described herein are compounds of Formula I:




and their pharmaceutically acceptable salts, wherein R1, R2, R3, X1, Y1, Y2, Y3, Y4 and Y5 are defined herein; their use as MC4R antagonists; pharmaceutical compositions containing such compounds and salts; the use of such compounds and salts to treat, for example, cachexia, anorexia, or anorexia nervosa; and intermediates and processes for preparing such compounds and salts.