Eleftha 375 mg Injection Eleftha 375 mg Injection contains trastuzumab, a targeted monoclonal antibody used for cancers in which the HER2 protein is present at high levels. It works by attaching to HER2 receptors on cancer cells and interfering with signals that promote cancer-cell growth. It can also help the immune system recognize and attack these abnormal cells. Eleftha is administered by intravenous infusion after appropriate reconstitution and dilution, under the supervision of a qualified healthcare professional.