The 22-year-old has spent several seasons out on loan with his most recent spell at Belgian side Sint-Truiden, where he scored six goals in 16 games last season.
With the likes of Danny Welbeck and Lucas Perez ahead of Akpom in the pecking order at Arsenal, the forward wasn't expected to be part of Unai Emery's plans going into next season while his contract only has 12 months to run on it.
Akpom will travel to Thessaloniki on Monday where he is set to put the finishing touches to his permanent move.
Arsenal are also expected to see both Carl Jenkinson and Joel Campbell leave the club this summer.
Campbell has struggled to find a home since moving to the Gunners in 2011 from Saprissa in his home country, while Jenkinson no longer fits in the club's plans.
The club are, however, closing in on a new deal for Alex Iwobi, with Emery confirming that the 22-year-old was "near" a contract extension last week .