Xencor, Inc. has received a milestone payment from Merck for the initiation of a Phase I trial for an undisclosed biologic candidate that uses Xencor’s XmAb antibody engineering platform.   Under the June 2013 agreement, Xencor granted Merck a non-exclusive license to certain patents for an undiclosed biologic along with an option to license the intellectual property for future products. Xencor receives annual maintenance fees and is eligible to receive success-based milestone payments, as...