Eleftha 440 mg Injection Eleftha 440 mg contains trastuzumab, a laboratory-produced monoclonal antibody designed to target HER2 (human epidermal growth factor receptor 2). It is used as part of treatment for certain HER2-positive cancers, particularly breast cancer and some stomach or gastroesophageal-junction cancers. By attaching to HER2 receptors, trastuzumab interferes with signals that encourage cancer-cell growth and helps the immune system recognize and attack the targeted cells.