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

This is a multicenter, open-label, dose escalation, phase I study to estimate the Maximum Tolerated Dose (MTD) or a lower Recommended Dose for Expansion (RDE) of LJM716 in combination with trastuzumab in patients with Human Epidermal growth factor Receptor 2 (HER2) overexpressing Metastatic Breast Cancer (MBC) or gastric cancer (MGC). The study consists of a dose escalation part and a dose expansion part. LJM716 will be administered intravenously once weekly unless a less frequent dosing regimen such as every 2 weeks or once every 4 weeks is introduced. Patients will continue on their trastuzumab dosing, administered intravenously once weekly at 2mg/kg. During dose escalation, a minimum of 15 patients are anticipated to be treated in successive cohorts. The dose escalation will continue until the MTD/RDE is declared. The RDE dose selected will either be the MTD or a dose below the MTD based on safety and Pharmacokinetic/Pharmacodynamic (PK/PD) considerations. Following the MTD/RDE declaration, approximately 20 MBC and 20 MGC patients will be enrolled in separate arms in the dose expansion part and treated at the MTD/RDE to further assess the safety, tolerability, and anti-tumor activity of the combination.