MacroGenics Presents Results from SOPHIA Study

MacroGenics (NASDAQ:MGNX) has announced updated results from its Phase 3 SOPHIA study in patients with HER2-positive metastatic breast cancer who have previously been treated with anti-HER@-targeted treatments.

As quoted in the press release:

Margetuximab is an investigational, immune-enhancing monoclonal antibody derived from the Company’s proprietary Fc-engineering technology platform. The data were presented today during an oral session at the San Antonio Breast Cancer Symposium (SABCS) by Dr. Hope Rugo, M.D., Director, Breast Oncology and Clinical Trials Education, University of California San Francisco Helen Diller Family Comprehensive Cancer Center.

“Patients with later stage HER2-positive metastatic breast cancer need access to new therapies. The updated SOPHIA study results presented today at the second interim survival analysis showed a trend in overall survival favoring margetuximab and are encouraging. Furthermore, margetuximab is the only HER2-targeted agent to show PFS superiority versus trastuzumab in a head-to-head Phase 3 clinical trial,” said Dr. Rugo. “The SOPHIA study also includes a pre-specified analysis of CD16A genotype as a predictor of anti-HER2 antibody efficacy, which although exploratory, is the first such prospective clinical analysis and suggests differential benefit in this population.”

Overall survival (OS) results favored margetuximab plus chemotherapy compared with trastuzumab and chemotherapy in the intention-to-treat (ITT) population; however, these data did not reach statistical significance at this second interim analysis as of a September 2019 cut-off after 270 events (median OS=21.6 months versus 19.8 months; hazard ratio [HR]=0.89; 95% CI: 0.69-1.13; P=0.326). The final pre-specified OS analysis is planned after 385 events have accrued, which is projected to occur in the second half of 2020. A pre-specified exploratory objective of the study was to evaluate the effect of CD16A (Fcγ receptor) allelic variation on margetuximab activity. Among the genetically defined subpopulation of patients carrying a CD16A 158F allele, who represent approximately 85% of the human (and SOPHIA study) population, the median OS at the second interim analysis was prolonged by 4.3 months in the margetuximab arm compared to the trastuzumab arm (23.7 months versus 19.4 months; HR=0.79; 95% CI: 0.61-1.04; nominal P=0.087). Among the approximately 15% of patients who were homozygous for the CD16A 158V allele, the trastuzumab arm performed better than the margetuximab arm.

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