Narcisse Bizet’s Twelve Grand Exercises for Advanced Studies, or “Douze Grande Etudes de Perfectionnement”, are a perfect stepping stone into the world of advanced grand etudes by the French masters. They are excellent preparation for the fifteen studies of Balay (here) the studies of Chavanne (here) and the Grand Studies of Petit (here).
These are slightly less difficult, but very challenging in their own right, with wonderful melodic textures and fantastically idiomatic writing for the trumpet. The first etude is available for free in the samples to the left. The complete book is available in at the link above. Enjoy!