Apart from mechanicals and crashes, there shouldn’t be a lot time hole opening up for GC contenders, however there can be some ache.
Col de Soudet mid-way, presenting a thousand meters of ascent in about 8 miles. Approx 7% grade, on common.
Then, 250 meter ascension for col d’Ichere with 7% grade, adopted quickly after by Col de Marie Blanque, with 700 m ascension, at about 8.6%
Then, descent and 4 miles of flat to the end. These closing few miles are very straight. Any breakaway can have bother holding off on this down hill and flat, straight end.