FDA approves Margenza for metastatic HER2-positive breast cancer
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The FDA approved margetuximab-cmkb for use in combination with chemotherapy for the treatment of adults with metastatic HER2-positive breast cancer, according to a press release from the agent’s manufacturer.
Margetuximab-cmkb (Margenza, MacroGenics) — a HER2-targeted monoclonal antibody — is indicated for patients who received two or more prior anti-HER2 regimens, including at least one for metastatic disease.
Approximately 15% to 20% of breast cancers are positive for HER2, and new treatments for these patients in the metastatic setting have been an unmet need.
The FDA based this decision, in part, on data from the phase 3 SOPHIA trial, presented in 2019 at the San Antonio Breast Cancer Symposium. The trial included 536 patients randomly assigned 1:1 to receive 15 mg/kg IV margetuximab (n = 266) every 3 weeks or 6 mg/kg IV trastuzumab (n=270; 8 mg/kg loading dose) every 3 weeks in combination with one of four chemotherapy agents: capecitabine, eribulin (Halaven, Eisai) gemcitabine or vinorelbine.
The primary endpoints of the study included sequentially assessed PFS followed by OS.
As Healio previously reported, data from that trial showed the combination of margetuximab plus chemotherapy led to a significant 24% reduction in the risk for progression or death compared with trastuzumab (Herceptin, Genentech) plus chemotherapy (HR = 0.76; 95% CI, 0.59-0.98). With these data, margetuximab became the first agent to improve PFS over trastuzumab in a head-to-head phase 3 trial.
Researchers reported objective response rates of 22% for the margetuximab combination and 16% for the trastuzumab combination. OS data are expected in the second half of next year.
Adverse events associated with the margetuximab combination included fatigue/asthenia (57%), nausea (33%), diarrhea (25%), and vomiting (21%). Infusion-related reactions occurred in 13% of patients receiving margetuximab, 1.5% of which were grade 3.
The agent also includes a boxed warning for left ventricular dysfunction and embryo-fetal toxicity.
“Early detection and treatment have had a positive impact on the survival of patients with breast cancer, but the prognosis for people diagnosed with metastatic breast cancer remains poor, and additional treatments are needed,” Hope S. Rugo, MD, researcher on the SOPHIA trial and professor of medicine and director of breast oncology and clinical trials education at University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, said in the press release. “As the only HER2-targeted agent to have shown a PFS improvement vs. trastuzumab in a head-to-head phase 3 clinical trial, Margenza with chemotherapy represents the newest treatment option for patients who have progressed on available HER2-directed therapies.”
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