I think Medac's response will be similar to what ATRS presented. Their going to say they have a valid patent, #231 "Concentrated Methotrexate Solutions" & list how ATRS infringes those claims.
The only real issue is whether or not Medac holds a valid patent which supersedes ATRS's claims. The interesting filings will be the arguments by Medac & ATRS why the 231 patent is valid or not.