Mersana Therapeutics and Takeda Pharmaceutical Co. have expanded their ongoing collaboration to create Fleximer antibody-drug conjugate (ADC) drug candidates to include additional oncology targets. Mersana is now eligible to receive additional upfront and milestone payments potentially totaling more than $300 million.   The collaboration from April 2014 has resulted in the conduct of preclinical, proof-of-concept studies for several Fleximer-ADCs against an undisclosed oncology target under a re...