A clinical trial of neratinib with or without fulvestrant is ongoing in patients with metastatic breast cancer with HER2 mutation but not amplification (ClinicalTrials.gov Identifier: NCT01670877; A Phase II Study of Neratinib Alone and in Combination With Fulvestrant in Metastatic HER2 Non-amplified But HER2 Mutant Breast Cancer). Here, ERBB2 is linked to breast cancer.