He was an opponent of Nestorius and close ally of Cyril of Alexandria at the Council of Ephesus of 431.
He delivered a homily at Ephesus and wrote two letters to Cyril.
Cyril in turn wrote two letters to Acacius.
[1] Melitene was a town in Eastern Anatolia.
He would have been young bishop at the time of the Second Council of Ephesus.