The 19-year-old, who is regarded as one of the brightest talents in Australia, has confirmed that personal terms have been agreed with the Serie A club.
"It's always been my dream to play in Serie A and I couldn't be happier," Antonis told The World Game.
"It's a fantastic setup over here and a huge opportunity for me to further my career.
"To be joining the same club that Vince Grella and Mark Bresciano played for is a privilege. I hope I can taste some of the success they enjoyed in Italy."
Antonis is currently training with the Italian side.