The U.S. Food and Drug Administration (FDA) approved pertuzumab on June 8, 2012, for the treatment of patients with advanced metastatic breast cancer who are anti-human epidermal growth factor receptor 2 (HER2)-positive, a novel anti-HER2-positive therapy. Patuximab can be used in combination with trastuzumab and other anti-HER2 therapies as well as docetaxel and is expected to be used in those patients with metastatic breast cancer who have not yet received anti-HER2 therapy or chemotherapy. HER2 is a protein associated with normal cell growth and its presence can be found in some proliferating numbers of cancer cells, including breast cancer, and in these HER2-positive breast cancer patients, amplification of the HER2 protein promotes cancer cell growth. Patuximab, a biotechnologically manufactured human monoclonal antibody that can be administered intravenously and targets different fractions of the HER protein, further reduces the growth and survival of HER2-positive breast cancer cells compared to trastuzumab. A clinical trial enrolling 808 patients with metastatic breast cancer who tested HER2-positive prior to treatment evaluated the safety and efficacy of pertuzumab. Patients were randomized to two groups: those receiving pertuzumab + trastuzumab + docetaxel and a control group of trastuzumab + docetaxel + placebo. The study evaluated the patients’ progression-free survival (PFS). The results showed that the median PFS was 18.5 months in the treatment group combined with pertuzumab and 12.4 months in the placebo group. The most common adverse reactions in patients treated with pertuzumab + trastuzumab + docetaxel included diarrhea, alopecia, leukopenia, nausea, malaise, rash, and nerve damage (peripheral sensory neuropathy).