When attorneys for Amgen Inc. and Transkaryotic Therapies Inc. appear in trial court May 15, the bottom line, at least initially, will be whether TKTX can show that claim one of AMGN's U.S. Patent No. 5,955,422 is invalid. However, the prospect is that both sides will present their entire argument regarding all 18 claims at issue in the patent infringement suit and the prospect for appeals is high, although such a protracted process is unlikely to last as long as AMGN's EPO patent