Preheat oven to 350°F. Mist a rimmed baking sheet with cooking spray.
In a small bowl, mix brown sugar, chili powder, cumin and salt. In a large bowl, combine pepitas and egg white; stir to coat. Add sugar-and spice mixture and mix well. Spread pepitas in a single layer on baking sheet and bake until dry and toasted, about 12 minutes. Remove from oven, stir to break up while still warm and let cool completely on baking sheet on wire rack.