MacroGenics Soars on Phase III Breast Cancer Study

Shares of Rockville, Md.-based MacroGenics, Inc. have skyrocketed nearly 160 percent in premarket trading after the company announced its Phase III HER2-positive metastatic breast cancer study hit the mark. Investors snapping up shares of MacroGenics drove the stock up more than $17 per share. MacroGenics closed at $11.11 per share on Tuesday, but this morning, the stock has jumped to $28.88 per share in premarket trading.
MacroGenics said its clinical asset margetuximab met the primary endpoints of prolongation of progression-free survival (PFS) in patients who have HER2-positive metastatic breast cancer. In the Phase III SOPHIA trial, patients were treated with a combination of margetuximab plus chemotherapy. Their data were compared to those patients who were treated with Genentech’s Herceptin (trastuzumab) plus chemotherapy. Trial data showed that patients on the margetuximab arm experienced a 24 percent risk reduction in PFS compared to patients in the trastuzumab arm. MacroGenics pointed out that approximately 85 percent of the patients in the Phase III trial were carriers of the CD16A (FcγRIIIa) 158F allele, which has been previously associated with diminished clinical response to Herceptin and other antibodies. In this particular group of patients, MacroGenics said patients who took its treatment exhibited a 32 percent risk reduction in PFS compared to patients in the trastuzumab arm.