Alena has spent the second half of the season on loan at Real Betis and it had previously been unclear where his future would lie beyond this season.
The 22-year-old – whose deal expires at Barcelona expires in 2022 – joined the Seville-based club in January due to a lack of first-team minutes at the Camp Nou, where he found himself behind Frenkie de Jong, Sergio Busquets, Arturo Vidal, Ivan Rakitic and Artur Melo in the pecking order.
However, Melo has since joined Juventus with Miralem Pjanic moving the other way – while there are doubts on the long-term futures of Vidal and Rakitic at the Camp Nou, with another youngster, Riqui Puig, enjoying prominent minutes under Quique Setien.
Indeed, it is said that Setien is a fan of Alena and would not have sanctioned the loan exit of the midfielder that his predecessor Ernesto Valverde did.
La Masia youth graduate Alena made 27 first-team appearances for the Catalan giants last season after being promoted from their B team but started just two games this season after the opening day of the campaign.
Alena has made 14 appearances for Betis to date since his loan move two months ago and has generally impressed in his outings for Los Verdiblancos, who languish in the lower half of mid-table in La Liga.