Sadly most PrC that grant casting on their own depend on CHA, not INT.
That said, I can see a Factotum entering Master of the Unseen Hand, Mindspy or Mindbender.
If you consider using Non-WotC Sources, Castlemourn has the Rhymesword PrC(10 levels, Int-based casting roughly equal to a Hexblade/Ranger/Paladin + some nice abilities related to (Greater) Magic Weapon & Energy Substitution).
Not all that impressive, considering the sheer versatility of singelclassed Factotum or Factotum/Chameleon.
But you asked for Arcane flavored PrC's and the ones I mentioned no serious spellcaster would consider, but they could work out ok for a Factotum looking for some unusual abilities.