MacroGenics says margetuximab improves PFS versus Herceptin in HER2-positive metastatic breast cancer study

MacroGenics announced Wednesday that the experimental drug margetuximab improved progression-free survival (PFS) compared to Roche's Herceptin (trastuzumab), when used in combination with chemotherapy, in patients with HER2-positive metastatic breast cancer. MacroGenics, whose shares jumped as much as 89 percent on the news, indicated that based on results of the Phase III head-to-head trial, it plans to submit a filing to the FDA in the second half of the year.

The SOPHIA study included 536 patients with HER2-positive metastatic breast cancer who previously received Herceptin and Roche's Perjeta (pertuzumab), and approximately 90 percent had previously received Roche's Kadcyla (ado-trastuzumab emtansine). In the trial, patients were treated with either margetuximab or Herceptin in combination with one of four chemotherapy agents.

According to MacroGenics, the study met the primary endpoint of prolongation of PFS, with patients in the margetuximab arm experiencing a 24-percent risk reduction in PFS compared to patients in the Herceptin group. The company added that in the 85 percent of patients in the trial who carried the CD16A (FcγRIIIa) 158F allele, which has been linked to diminished clinical response to Herceptin, subjects given margetuximab experienced a 32-percent risk reduction in PFS compared to those who received Herceptin.

MacroGenics said that follow-up on the sequential primary endpoint of overall survival is ongoing, adding that the combination of margetuximab and chemotherapy showed acceptable safety and tolerability, comparable overall to that of Herceptin and chemotherapy. The company noted that the results are being prepared for submission for publication and presentation later this year at a medical conference.

Margetuximab is an immune-enhancing monoclonal antibody derived from MacroGenics' Fc optimisation technology platform designed to target the HER2 oncoprotein. CEO Scott Koenig said "we look forward to additional opportunities to develop margetuximab in other HER2-positive breast and gastric cancer populations."

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