Margenza Approved to Treat Metastatic HER2 Breast Cancer

December 16, 2020 – The U.S. FDA has approved MargenzaTM (margetuximab-cmkb), manufactured by MacroGenics, for use in combination with chemotherapy to treat adults who have metastatic HER2- positive breast cancer and have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease.

HER2 breast cancer accounts for up to 20% of breast cancer diagnoses in the United States. The HER2 protein expressed by the cancer’s cells contributes to tumor development and makes the disease more aggressive. Margenza is a monoclonal antibody designed to inhibit the function of the HER2 protein, helping to slow tumor development.

In a clinical study, Margenza plus chemotherapy delivered a 24% reduction in risk of disease progression or death compared to trastuzumab plus chemotherapy (a current standard of care). Treatment with Margenza plus chemotherapy produced a 22% objective response rate (ORR) versus a 16% ORR with trastuzumab plus chemotherapy. The analysis of overall survival has not yet been completed.

Recommended dosing is 15mg/kg of the patient’s body weight administered as an intravenous infusion every three weeks until disease progression or unacceptable toxicity occur. The initial infusion must be given over the course of at least 120 minutes, while all subsequent infusions can be administered over the course of at least 30 minutes.

A black box warning cautions that there is a risk of left ventricular dysfunction and embryo-fetal toxicity with Margenza. Left ventricular dysfunction occurs when the left ventricle, a chamber in the heart responsible for pumping oxygenated blood to the body’s other organs, is unable to function properly.

MacroGenics plans to launch Margenza in March 2021. Pricing is not yet available.