He appeared Monday in Castle Rock, which is in suburban Douglas County south of Denver. His attorney entered Cox's plea during the hearing. The judge set an Oct. 18 trial date.
Cox is charged with one count of sexual assault while the victim was physically helpless and one count of sexual assault while the victim was incapable of determining the nature of the conduct.
Court documents say the alleged assault happened on Sept. 6. He was arrested Dec. 9 and is free on bond.
Details of the charges remain under seal at the request of prosecutors and Cox's defense attorney, which is being contested by the media.