The majority of patients with a PR had HER2+ metastatic breast cancer….Patients with HER2+ metastatic breast cancer (*) [HER2+ MBC] tended to have longer PFS (median PFS 5.4 months, range 1.2–17.1 months)….The median duration of maintenance single-agent varlitinib therapy was 5.1 months (range 2.0–13.3 months) without disease progression in these patients. All eight patients had HER2+ metastatic breast cancer.