Eleftha 150 mg Injection Eleftha 150 mg is an intravenous anticancer medicine containing trastuzumab, a laboratory-produced monoclonal antibody designed to target the HER2 protein. It is used for certain HER2-positive cancers, particularly breast cancer and some gastric or gastroesophageal cancers. By attaching to HER2 on cancer cells, trastuzumab interferes with signals that encourage tumor-cell growth and can also help the immune system recognize and attack these cells.