Heat oven to 350.
Spray 9x5" loaf pan with cooking spray.
Remove biscuits from tube. Separate each biscuit into two layers, making 16 thin biscuits and place on wax paper or aluminum foil.
Spread pumpkin pie mix on each of the 16 biscuits. Top each with melted butter.
Mix granulated sugar and 1 teaspoon of the pumpkin pie spice; sprinkle over each.
Stack biscuits in 4 piles of 4 of the thin biscuits. Place stacks on their sides in a row in the loaf pan. Make sure the sides without filling are on each of the ends (touching the pan).
Bake 40-50 minutes or until loaf is deep golden brown and center is baked through.
While loaf cools slightly, in a small bowl, mix powdered sugar, milk, vanilla and pumpkin pie spice until smooth.
Drizzle over loaf in pan or on a platter. Serve warm.