ERBB3 and invasive ductal breast carcinoma: We next examined the efficacy of SAH5-EJ1 in a patient-derived xenograft of grade 3 invasive ductal breast carcinoma (TM01278) with increased expression of HER1 (with an R521K mutation that reduces ligand binding [62]) and increased expression of HER3 (carrying a G1288A mutation in the kinase domain [8]).