Phesgo 600 mg + 600 mg Phesgo 600 mg + 600 mg/10 mL is a targeted cancer treatment containing pertuzumab 600 mg and trastuzumab 600 mg in a single subcutaneous injection. It is designed for the treatment of HER2-positive breast cancer. The two active ingredients work together by targeting the HER2 protein and interfering with the signals that promote cancer-cell growth and survival. This strength is generally used as the maintenance dose following the initial loading dose and is administered under the supervision of a healthcare professional.