Takeda Pharmaceutical Co. Ltd. committed to pay Mersana Therapeutics Inc. $40 million up front, plus up to $750 million in milestone payments plus royalties to gain ex-U.S. and Canada rights to the company's lead candidate, a preclinical antibody-drug conjugate (ADC) targeting HER2-expressing tumors, and to advance a potential new slate of ADCs, one of which Mersana can opt to co-develop following phase I studies.