Phase I Study LJM716 Combined With Trastuzumab in Patients With HER2 Overexpressing Metastatic Breast or Gastric Cancer

Inclusion Criteria: * Patients with confirmed HER-2 positive, metastatic or non-operable locally advanced breast or gastric cancer * Metastatic breast cancer patients must have received a minimum of 1 and a maximum of 3 prior anti HER2 based regimens with documented progression on the most recent regimen which must contain trastuzumab, ado-trastuzumab emtansine or lapatinib * Metastatic gastric cancer patients must have received a minimum of 1 and a maximum of 2 prior anti HER2 based regimens with documented progression on the most recent regimen which must contain trastuzumab or ado-trastuzumab emtansine * During the dose expansion part of study, all patients must have at least one measurable lesion as defined by RECIST criteria. * Patients must have at least one prior trastuzumab-containing regimen * Eastern Cooperative Oncology Group (ECOG) Performance status ≤ 2 Exclusion Criteria: * Patients with Central Nervous System (CNS) metastasis which are: symptomatic or require treatment for symptom control and/or growing * Prior treatment with any anti-HER3 (Human Epidermal growth factor Receptor 3) treatment * Impaired cardiac function * Prior to the first dose of study treatment, patients who have received systemic antineoplastic therapy or any investigational therapy within 4 weeks or within 5 half- lives of the therapy prior to starting study treatment, whichever is shorter, or for cyclical therapy, within one cycle length (e.g. 6 weeks for nitrosourea, mitomycin-C). * Patients who have a history of primary malignancy other than that being treated in this study, and currently requires active clinical intervention. * Patients who do not have an archival tumor sample (or sections of it) available or readily obtainable. Other protocol-defined inclusion/exclusion criteria may apply