Patients with HER-2 positive MBC ...received Herzuma® (8mg/kg IV for 1st cycle loading dose, and then 6mg/kg IV every 3 weeks) plus Gedatolisib (180mg on D1, 8, 15 of every 21 days). All patients were confirmed to have pathologic PIK3CA aberrations: H1047R, H1047L, E542Q, E542K, E453K, N345K, and PIK3CA amplification. All patients who have reached PR remain on investigational treatment at the data cutoff point, and the longest one is on treatment for 7.8 months. In this phase 2 pilot study, Trastuzumab biosimilar plus Gedatolisib presented 45.5% of response rate with manageable toxicity in patients with HER-2 positive MBC with PIK3CA aberration.