When, late last year, Daiichi Sankyo Co. Ltd. won breakthrough status from the FDA for HER3-targeting lung cancer prospect patritumab deruxtecan, Wall Street began taking stock of other candidates in the space. “The winning strategy to therapeutically target HER3 remains to be seen,” noted a recent paper in Clinical Cancer Research, “but HER3 is a promising drug target, and the era of drugging the ‘undruggables’ has already started.”