The second or subsequent action on patentability in an inter partes reexamination proceeding is called the Action Closing Prosecution (ACP).  The patent owner may respond with argument and/or an evidentiary showing and/or amendments.  Alternatively, the patent owner may choose not to respond.  If the patent owner does file a response, then the third party requester may thereafter file written comments directed only to the patent owner’s submission.  Entry of the patent owner response is not a matter of right.  Neither party may appeal at this point in the proceeding [MPEP 2671.02].