Clinical activity of MCLA-128 (zenocutuzumab) in combination with endocrine therapy (ET) in ER+/HER2-low, non-amplified metastatic breast cancer (MBC) patients (pts) with ET-resistant disease who had progressed on a CDK4/6 inhibitor (CDK4/6i).

1037Background: MCLA-128 (zenocutuzumab) is an ADCC-enhanced humanized bispecific antibody targeting HER2 and HER3 and potently blocking HER3-ligand induced receptor dimerization. Upregulation of H...