Macrogenics (MGNX) Announces Publication of SOPHIA Trial Results for MARGENZA in JAMA Oncology

January 25, 2021 7:33 AM EST

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MacroGenics, Inc. (Nasdaq: MGNX), a biopharmaceutical company focused on developing and commercializing innovative monoclonal antibody-based therapeutics for the treatment of cancer, today announced the publication of results from the SOPHIA trial of MARGENZA™ (margetuximab-cmkb) in the Journal of the American Medical Association (JAMA) Oncology. SOPHIA is a pivotal Phase 3 clinical trial of 536 adult patients with metastatic HER2-positive breast cancer previously treated with two or more anti-HER2 regimens and from one to three lines of therapy for metastatic disease. In the study, MARGENZA demonstrated a statistically significant 24% reduction in the risk of disease progression or death compared to Herceptin, each in combination with chemotherapy (Hazard Ratio [HR] = 0.76; 95% CI, 0.59-0.98; p=0.03; median PFS 5.8 vs. 4.9 months).

“MARGENZA is the first HER2-targeted therapy to reduce the risk of disease progression in metastatic breast cancer patients over trastuzumab in a head-to-head comparison involving a heavily pretreated patient population,” said Scott Koenig, M.D., Ph.D., President and CEO of MacroGenics. “These data represent years of research and clinical development at MacroGenics leading to the forthcoming commercialization of this innovative antibody-based therapeutic for the treatment of metastatic HER2-positive breast cancer.”

In addition to the statistically significant improvement in primary endpoint of PFS by centrally blinded review, investigator-assessed PFS (based on 337 events) was also greater with MARGENZA compared to trastuzumab with a 30% PFS relative risk reduction compared to trastuzumab (HR=0.70; 95% CI, 0.56-0.87; P=0.001; median investigator-assessed PFS 5.6 vs 4.2 months). Among 524 response-evaluable patients, the objective response rates for MARGENZA plus chemotherapy and trastuzumab plus chemotherapy were 22% and 16%, respectively (P=0.06) and the clinical benefit rates were 37% for MARGENZA and 25% for trastuzumab, (P=0.003).

At the prespecified interim Overall Survival (OS) analysis, based on 270 events, median OS was 21.6 months with MARGENZA and 19.8 months with trastuzumab (HR=0.89; 95% CI, 0.69-1.13; P=0.33). The stopping threshold was not reached. The final OS analysis will occur after 385 events, and it is expected in the second half of 2021.

Adverse reactions occurring in greater than twenty percent of patients with MARGENZA in combination with chemotherapy were fatigue/asthenia (57%), nausea (33%), diarrhea (25%), and vomiting (21%). The MARGENZA U.S. Prescribing Information has a BOXED WARNING for left ventricular dysfunction and embryo-fetal toxicity. In addition, MARGENZA can cause infusion related reactions (IRRs). IRRs occurred in 13% of patients treated with MARGENZA, with the majority reported as Grade 2 or less. Grade 3 IRRs occurred in 1.5% of patients. See below for Important Safety Information.

“Up to one-fifth of all breast cancers are HER2-positive, and identifying new treatment options for patients in the metastatic setting represents a serious unmet medical need,” said SOPHIA principal investigator Hope S. Rugo, M.D., Professor of Medicine and Director of Breast Oncology and Clinical Trials Education, University of California San Francisco Helen Diller Family Comprehensive Cancer Center. “These results show that MARGENZA provides improvement, for this patient population, beyond what we can achieve with trastuzumab, which is good news for patients with advanced disease.”

MacroGenics anticipates that MARGENZA will be available to patients in the U.S. in March of 2021.

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