Pertuzumab, commonly known as Perjeta, is an antibody drug that targets HER2- positive cancer cells, but in a different way than trastuzumab.

In people with HER2-positive early breast cancers at high risk of recurrence, adding pertuzumab to treatment with trastuzumab and chemotherapy can reduce the risk of recurrence by about 20 percent.

Pertuzumab is always given in combination with trastuzumab. It’s not given on its own. The combination of drugs is given by vein (through an IV) or injection under the skin every 3 weeks for up to one year.

Possible side effects of pertuzumab include rash, diarrhea, nausea and fatigue.

Treatment with pertuzumab and trastuzumab may begin before breast cancer surgery or after surgery.

Pertuzumab is also used to treat HER2-positive metastatic breast cancer. For more information, see the Living with Metastatic Breast Cancer section in this tool.