NEW YORK – Daiichi Sankyo and AstraZeneca on Tuesday announced the start of a Phase III, head-to-head comparison of trastuzumab deruxtecan (Enhertu) and trastuzumab emtansine (Genentech's Kadcyla or T-DM1) as adjuvant treatment in early-stage, HER2-positive breast cancer patients after they've received neo-adjuvant therapy.