The FDA has approved margetuximab-cmkb plus chemotherapy to treat adults with metastatic HER2-positive breast cancer who have received at least two prior anti-HER2 regimens. 

According to a release from the American Association for Cancer Research, the approval follows results from the SOPHIA trial, which included more than 500 patients with IHC 3+ or ISH-amplified HER2+ metastatic breast cancer who had received prior anti-HER2 therapies. During the trial, patients were treated with either margetuximab and chemotherapy or trastuzumab and chemotherapy. The trial’s primary outcomes were progression-free survival and overall survival, with researchers also examining objective response rate and duration of response. 

The median progression-free survival in the margetuximab arm was 5.8 months (95% CI: 5.5-7.0), compared to 4.9 months (95% CI: 4.2-5.6) in the control arm. The confirmed overall response rate was 22% (95% CI: 17-27), with a median duration of response of 6.1 months (95% CI: 4.1-9.1) in the margetuximab arm, compared to an overall response rate of 16% (95% CI: 12-20), and a median duration of response of 6 months (95% CI: 4.0-6.9) in the control arm. 

The most common adverse drug reactions in the margetuximab arm included fatigue, nausea, diarrhea, and vomiting. The release noted that the prescribing information includes a Boxed Warning for the risks of left ventricular dysfunction and embryo-fetal toxicity. 

Prior to the approval, the FDA had granted the application Fast-Track designation.