The agreement does not include a purchase clause for the former Spanish U21 international, with Dominic Torrent’s side, as per reports from Diario AS.
Pena has already travelled to Turkey this weekend and a deal is expected to be completed before the European transfer window closes in the next 24 hours.
The 23-year-old has returned to Barcelona’s B team this season with nine appearances for them in 2021/22.
His departure includes a wage sharing agreement between the two clubs as Barcelona look to reduce their salary bill in the second half of 2021/22.
Ter Stegen and Neto will continue as the two senior goal keeping options for Barcelona in the coming months.