Abstract 5201: U3-1402, a novel HER3-targeting antibody-drug conjugate, exhibits in vitro antitumor activity against breast cancer cells expressing HER3 mutations without dependence on HER2 overexpression

Background: U3-1402, a novel HER3-targeting antibody-drug conjugate (ADC) composed of a fully human anti-HER3 antibody (patritumab), tetrapeptide-based linker, and topoisomerase I inhibitor payload, is currently being studied in clinical trials for patients with HER3-positive breast cancer (phase 1/2, NCT02980341) and NSCLC (phase 1, NCT03260491). HER3 is overexpressed in multiple human cancers and plays an important role in cell proliferation...