ALTER LARGE OBJECT large_object_oid OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER LARGE OBJECT changes the definition of a large object.
You must own the large object to use ALTER LARGE OBJECT. To alter the owner, you must also be a direct or indirect member of the new owning role. (However, a superuser can alter any large object anyway.) Currently, the only functionality is to assign a new owner, so both restrictions always apply.
large_object_oid
new_owner
There is no ALTER LARGE OBJECT statement in the SQL standard.