Pulse gingersnaps in food processor until they form fine crumbs. Stir in melted butter. Spray 9-inch deep-dish pie dish with cooking spray and press crumbs into bottom.
Combine pumpkin, milk, egg whites, salt, pumpkin pie spice, vanilla, and sugar in a large bowl and beat until smooth. Pour mixture into pie dish.
Bake at 400 degrees for 15 minutes. Lower oven temperature to 325 and bake for 45 minutes more, or until knife inserted into center comes out clean. Cool on wire rack.
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