Xencor Renegotiates XmAb®5871 Agreement with Amgen; Regains All Rights and Plans Clinical Development in Rare Autoimmune Disease Focusing development on rare autoimmune disorder IgG4-related disease (IgG4-RD)Ongoing Phase 1b/2a clinical trial on track to report topline results by end of 2014Conference call today at 5:00 p.m. EDT